JP7718262B2 - Control method for electric vehicle and control device for electric vehicle - Google Patents

Description

The present invention relates to a control method and control device for an electric vehicle.

Patent Document 1 relates to the control of an electric vehicle equipped with a first electric motor that drives the front wheels and a second electric motor that drives the rear wheels, and discloses that a slip state is detected based on the difference in rotational speed between the front and rear wheels, and that, based on the slip state, output torque is transferred from the slipping wheel of the front or rear wheels to the non-slip wheel, while the rate of change in the output torque that is transferred is limited so as to prevent the non-slip wheel from slipping.

Patent No. 5835583

Electric vehicles are known that are equipped with multiple motors, each controlling a separate drive wheel. For example, there are four-wheel-drive electric vehicles in which the front and rear wheels are driven by different motors. In such electric vehicles, the torque required to generate the required drive force, depending on the driver's accelerator operation, is distributed to each motor, thereby generating the required torque (drive force) for the entire electric vehicle. When a difference in rotation speed occurs between drive wheels driven by different motors and it is determined that one of the drive wheels is slipping, the torque that should be generated by the slipping drive wheel is additionally borne by the drive wheel that is not slipping. In this way, the electric vehicle generates the required torque while eliminating drive wheel slippage. In particular, the control described in Patent Document 1 limits the amount of torque transfer, thereby preventing drive wheels that were not slipping from slipping due to torque transfer.

However, as described above, when attempting to correct a rotational speed difference between drive wheels driven by different motors, i.e., slippage, by transferring torque, it may be difficult for the rotational speed of the drive wheels to converge to a stable, steady state. Specifically, repeated torque transfer between the drive wheels may result in an unstable control state in which the rotational speed of each drive wheel changes oscillately. This type of unstable control state can also occur when the rate of change (speed of change) of the transferred torque is limited. In other words, when torque that should be generated at a drive wheel with an excessive rotational speed is transferred to another drive wheel in order to correct a rotational speed difference between the drive wheels, the unstable control state described above may occur.

The present invention aims to provide a control method and control device for an electric vehicle that, when a difference in rotation speed occurs between drive wheels driven by different motors, corrects the difference in rotation speed and easily converges to a stable control state in which rotation speed fluctuations are suppressed.

One aspect of the present invention is a control method for an electric vehicle having first drive wheels driven by a first motor and second drive wheels driven by a second motor different from the first motor. In this control method, a total torque corresponding to the driving force required of the electric vehicle is determined, and this total torque is distributed to the first motor and the second motor to calculate a first base torque, which is the torque to be output by the first motor, and a second base torque, which is the torque to be output by the second motor. Furthermore, a first rotation speed target value, which is a target value for the rotation speed of the first motor, is calculated based on the rotation speed of the second motor, and a second rotation speed target value, which is a target value for the rotation speed of the second motor, is calculated based on the rotation speed of the first motor. Furthermore, a first rotation speed control torque, which is the torque to be output by the first motor, is calculated based on the first rotation speed target value, and a second rotation speed control torque, which is the torque to be output by the second motor, is calculated based on the second rotation speed target value. Then, (a) when the rotation speed of the first motor is greater than the rotation speed of the second motor, a first final torque command value, which is the final torque command value for the first motor, is calculated based on the first rotation speed control torque, and a second final torque command value, which is the final torque command value for the second motor, is calculated by correcting the second basic torque based on a first torque deviation, which is the deviation between the first basic torque and the first rotation speed control torque. Meanwhile, (b) when the rotation speed of the second motor is greater than the rotation speed of the first motor, a first final torque command value is calculated by correcting the first basic torque based on a second torque deviation, which is the deviation between the second basic torque and the second rotation speed control torque, and a second final torque command value is calculated based on the second rotation speed control torque. The first motor and the second motor are then driven based on the first and second final torque command values calculated as described above.

The present invention provides a control method and control device for an electric vehicle that, when a difference in rotation speed occurs between drive wheels driven by different motors, corrects the difference in rotation speed and easily converges to a stable control state in which fluctuations in rotation speed are suppressed.

FIG. 1 is an explanatory diagram showing a schematic configuration of an electric vehicle. FIG. 2 is a block diagram showing the configuration of the motor controller. FIG. 3 is a graph showing an example of an accelerator opening-torque table. FIG. 4 is a block diagram showing the configuration of the torque distribution calculation unit. FIG. 5 is an explanatory diagram relating to the equation of motion of an electric vehicle. FIG. 6 is a block diagram showing the configuration of the slip control calculation unit. FIG. 7 is a block diagram showing the configuration of the slip determination unit. FIG. 8 is a block diagram showing the configuration of the front/rear rotation difference target value calculation unit. FIG. 9 is a block diagram showing the configuration of the front slip control calculation unit. FIG. 10 is a block diagram showing the configuration of the rotation speed control unit in the front slip control calculation unit. FIG. 11 is a block diagram showing the configuration of the disturbance torque estimation section in the front slip control calculation section. FIG. 12 is a block diagram showing the configuration of the rear slip control calculation unit. FIG. 13 is a block diagram showing the configuration of the rotation speed control unit in the rear slip control calculation unit. FIG. 14 is a block diagram showing the configuration of the disturbance torque estimation section in the rear slip control calculation section. FIG. 15 is a block diagram showing the configuration of the longitudinal torque command value calculation unit. FIG. 16 is a time chart showing longitudinal acceleration and the like when the control of the first comparative example is executed. FIG. 17 is a time chart showing longitudinal acceleration and the like when the control of the second comparative example is executed. FIG. 18 is a time chart showing longitudinal acceleration and the like when the control according to this embodiment is executed.

Embodiments of the present invention will be described below with reference to the drawings.

[First embodiment]
Fig. 1 is an explanatory diagram showing the schematic configuration of an electric vehicle 10. As shown in Fig. 1, the electric vehicle 10 of this embodiment is a four-wheel drive vehicle in which front wheels 22 and rear wheels 32 are driven by different motors. The electric vehicle 10 includes a front drive system 11, a rear drive system 12, a battery 13, and a motor controller 14.

The front drive system 11 is a system that drives the front wheels 22 using a front motor 21. In addition to the front motor 21 and front wheels 22, the front drive system 11 also includes a front inverter 23, a rotation sensor 24, a current sensor 25, etc.

The front motor 21 is, for example, a three-phase AC synchronous motor, and is driven by AC power input from the front inverter 23. The output torque of the front motor 21 generates torque (driving force) on the front wheels 22. In addition, when the drive shaft of the front motor 21 is rotated by the front wheels 22, it generates so-called regenerative torque. This allows the front motor 21 to recover the kinetic energy of the electric vehicle 10 as electrical energy.

The front wheels 22 are drive wheels located at the front of the electric vehicle 10. The front wheels 22 are connected to the front motor 21 via a front reduction gear 26 and a drive shaft 27.

The front inverter 23 has two pairs of switching elements for each phase of the front motor 21. The front inverter 23 turns these switching elements on and off in response to a PWM (Pulse Width Modulation) signal input from the motor controller 14. As a result, the front inverter 23 converts the DC power supplied from the battery 13 into AC power and inputs it to the front motor 21 to drive it. The switching elements that make up the front inverter 23 are power semiconductor elements such as insulated gate bipolar transistors (IGBTs) and metal oxide semiconductor field effect transistors (MOS-FETs). During regenerative control, the front inverter 23 converts the AC power generated by the front motor 21 into DC power and inputs it to the battery 13.

The rotation sensor 24 detects the rotor phase _αf of the front motor 21. The rotor phase _αf is a so-called electrical angle [rad]. The rotation sensor 24 is, for example, a resolver or an encoder. The detected rotor phase _αf is input to the motor controller 14.

The current sensor 25 detects the currents i _uf , i _vf , and i _wf flowing through the respective phases of the front motor 21. These currents i _uf , i _vf , and i _wf are input to the motor controller 14.

The rear drive system 12 is a system that drives rear wheels 32 by a rear motor 31, and is configured symmetrically to the front drive system 11. Therefore, in addition to the rear motor 31 and rear wheels 32, the rear drive system 12 also includes a rear inverter 33, a rotation sensor 34, a current sensor 35, a rear reduction gear 36, a drive shaft 37, etc. These components that make up the rear drive system 12 function in the same way as the components of the front drive system 11. In other words, the rear wheels 32 are drive wheels located at the rear of the electric vehicle 10. The rotor phase of the rear drive system 12 detected by the rotation sensor 34 is "α _r ". The currents flowing through each phase of the rear motor 31 detected by the current sensor 35 are "i _ur , i _vr , i _wr ".

The battery 13 is provided in common to the front drive system 11 and the rear drive system 12 and supplies power to drive the front motor 21 and the rear motor 31. During regenerative control, the battery 13 is charged by the regenerative power generated by the front motor 21 and the rear motor 31.

The motor controller 14 is a control device for the electric vehicle 10. The motor controller 14 acquires various vehicle variables and generates PWM signals for driving the front motor 21 and rear motor 31 based on these vehicle variables. The motor controller 14 then inputs the generated PWM signals to the front inverter 23 and rear inverter 33, respectively, to drive the front motor 21 and rear motor 31 in accordance with the vehicle variables.

Vehicle variables are parameters that represent the control state of the electric vehicle 10. The motor controller 14 acquires, as vehicle variables, for example, the rotor phase _αf and currents _iuf , _ivf , and _iwf of the front motor 21, and the rotor phase _αr and currents _iur , _ivr , and _iwr of the rear motor 31. In addition, the motor controller 14 acquires, as vehicle variables, for example, the accelerator opening _Apo , the vehicle speed V, the steering rotation angle _θstr [rad], and the voltage _Vdc (not shown) of the battery 13. The accelerator opening _Apo is a parameter that represents the amount of operation of the accelerator (not shown) by the driver. The steering rotation angle _θstr is a parameter that represents the operation direction and amount of operation of the steering wheel (not shown) by the driver. Vehicle variables such as accelerator opening _Apo , vehicle speed V, steering rotation angle _θstr , and voltage _Vdc of battery 13 can be detected appropriately as needed by sensors (not shown), etc. Although the motor controller 14 in this embodiment acquires the vehicle variables directly from sensors, etc., the motor controller 14 can also acquire some or all of the vehicle variables from another controller (computer) (not shown).

As described above, the electric vehicle 10 has a first drive wheel (e.g., front wheel 22) driven by a first motor (e.g., front motor 21), and a second drive wheel (e.g., rear wheel 32) driven by a second motor (e.g., rear motor 31) different from the first motor. The specific configuration of the motor controller 14 that controls the first motor and second motor, i.e., the front motor 21 and rear motor 31, is described below.

[Motor controller configuration]
2 is a block diagram showing the configuration of motor controller 14. Motor controller 14 is configured with one or more computers and is programmed to repeatedly execute the processes of each unit described below at predetermined intervals. Specifically, motor controller 14 includes an input processing unit 41, a basic torque calculation unit 42, a slip control calculation unit 43, a vibration suppression control calculation unit 44, a current command value calculation unit 45, and a current control calculation unit 46 (motor drive control unit).

The input processing unit 41 acquires vehicle variables used for various control calculations or performs input processing to calculate them.

For example, the input processing unit 41 acquires the accelerator opening A _po , the vehicle speed V, the steering rotation angle θ _str , the voltage V _dc of the battery 13, and the like from a sensor or a controller (not shown).

The input processing unit 41 also acquires the currents _iuf , _ivf , and _iwf of the front motor 21 and the currents _iur , _ivr , and _iwr of the rear motor 31 from the current sensors 25 and 35. In this embodiment, the current sensors 25 and 35 detect three-phase currents, but when the current sensors 25 and 35 detect two-phase currents out of the three-phase currents, the input processing unit 41 calculates the current of the remaining phase using the detected two-phase currents.

The input processing unit 41 also acquires the rotor phase _αf of the front motor 21 and the rotor phase _αr of the rear motor 31 from the rotation sensors 24, 34, respectively. The input processing unit 41 then differentiates these rotor phases _αf and _αr to calculate the rotor angular velocity _ωf [rad/s] of the front motor 21 and the rotor angular velocity _{ωr [rad/s] of the rear motor 31. The input processing unit 41 divides the rotor angular velocities ωf and ωr by the number of pole pairs of the front motor 21 and the rear motor 31 to calculate the rotation speed ωmf [ rad /} s] of the front motor 21 (hereinafter referred to as the front motor rotation speed) and the rotation speed _ωmr [rad/s] of the rear motor 31 (hereinafter referred to as the rear motor rotation speed). The front motor rotation speed ω _mf and the rear motor rotation speed ω _mr are the mechanical angular velocities of the respective drive motors.

In the following various calculations, the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr are used. However, the input processing unit 41 can calculate the rotation speed _Nf [rpm] of the front motor 21 and the rotation speed _Nr [rpm] of the rear motor 31 by multiplying the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr by a unit conversion coefficient (60/2π). The input processing unit 41 can also calculate the wheel rotation speeds of the front wheels 22 and the rear wheels 32 using the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr and the kinetic radii of the front wheels 22 and the rear wheels 32. Therefore, in the following various calculations, rotation speeds _Nf , _{Nr that} are substantially equivalent to the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr or the wheel rotation speeds of the front wheels 22 and the rear wheels 32 can be used instead of _the front motor rotation speed ωmf and the rear motor rotation speed ωmr.

The basic torque calculation unit 42 calculates a total torque T _m1 ^* corresponding to the driving force required of the electric vehicle 10, and executes a basic torque calculation process to distribute this total torque T _m1 ^* to the front motor 21 and the rear motor 31. Specifically, the basic torque calculation unit 42 includes a total torque calculation unit 47 and a torque distribution calculation unit 48. The driving force required of the electric vehicle 10 is a driving force determined according to the driver's operation, such as accelerator operation, and is the driving force that should be generated by the electric vehicle 10 as a whole.

The total torque calculation unit 47 executes a total torque calculation process to calculate the total torque T _m1 ^* based on the front motor rotation speed ω _mf and the accelerator opening A _po . For example, the total torque calculation unit 47 stores in advance an accelerator opening-torque table that associates the front motor rotation speed ω _mf , the accelerator opening A _po , and the total torque T _m1 ^* . Therefore, the total torque calculation unit 47 sets the total torque T _m1 ^* according to the front motor rotation speed ω _mf and the accelerator opening A _po by referring to the accelerator opening-torque table.

The torque distribution calculation unit 48 sets a front basic torque T _mf ^* and a rear basic torque T _mr ^* by a torque distribution calculation process that distributes the total torque T _m1 ^* to the front wheels 22 and the rear wheels 32. The front basic torque T _mf ^* is a target value for the portion of the total torque T _m1 ^* that should be output by the front motor 21. The rear basic torque T _mr ^* is a target value for the portion of the total torque T _m1 ^* that should be output by the rear motor 31.

The configuration of the basic torque calculation unit 42, i.e., the configuration of the total torque calculation unit 47 and the torque distribution calculation unit 48, will be described in detail below.

The slip control calculation unit 43 calculates _a front final torque command value T mf _-f2 * and a rear final torque command value T _mr- f2 ^* based on the front basic torque T _mf ^* , the rear basic torque T _mr ^* , the front motor rotation speed ω _mf , and the rear motor rotation speed ω ^mr . The front final torque command value T _mf-f2 ^* is the final torque command value for the front motor 21. The rear final torque command value T _mr- f2 ^* is the final torque command value for the rear motor 31. In particular, the slip control calculation unit 43 executes slip control calculation processing that eliminates or suppresses slip of the front wheels 22 and the rear wheels 32 and suppresses fluctuations in the front motor rotation speed ω _mf and the rear motor rotation speed ω _mr . Through this slip control calculation processing, the slip control calculation unit 43 sets the front final torque command value T _mf-f2 ^* and the rear final torque command value T _mr-f2 ^* . The configuration of the slip control calculation unit 43 will be described in detail later.

In this embodiment, "slip" refers to a state in which there is a difference between the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr . Therefore, slip can occur even when the front wheels 22 and the rear wheels 32 grip the road surface and both the front wheels 22 and the rear wheels 32 are generating driving force. In this embodiment, even if slip occurs in the front wheels 22 or the rear wheels 32, it is assumed that at least one of the front wheels 22 or the rear wheels 32 is gripping the road surface. In the following, it is assumed that the drive wheel with a relatively higher rotation speed is in a slipping state. For example, when the front motor rotation speed _ωmf is higher than the rear motor rotation speed _ωmr , the front wheels 22 are slipping.

The vibration suppression control calculation unit 44 performs _vibration suppression control calculation processing on the front final torque command value T _mf-f2 ^* and the rear final torque command value T _mr-f2 ^* based on the front motor rotational speed ω _mf and the rear motor rotational speed ω mr. Specifically, the vibration suppression control calculation unit 44 feeds back the front motor rotational speed ω _mf and the rear motor rotational speed ω _mr using the transfer characteristics from the torque input to each motor to the rotational speed of each motor. In this way, the vibration suppression control calculation unit 44 compensates for components such as torsional vibration of the drive shafts 27, 37 that are included in the front final torque command value T _mf-f2 ^* and the rear final torque command value T _mr-f2 ^* . More specifically, the vibration suppression control calculation unit 44 executes known vibration suppression control processing, for example, as described in Japanese Patent Application Laid-Open No. 2003-009566. When the electric vehicle 10 does not have the drive shafts 27, 37, or when torsional vibrations of the drive shafts 27, 37 are suppressed by a mechanical mechanism or the like, the vibration suppression control calculation may be omitted.

The current command value calculation unit 45 executes current command value calculation processing to calculate dq-axis current command values i _df ^* , i _qf ^* (not shown) for the front motor 21 and dq-axis current command values i _dr ^* , i _qr ^* (not shown) for the rear motor 31. Specifically, the current command value calculation unit 45 holds, for example, a front current command value table (not shown). The front current command value table is a look-up table in which the front final torque command value T _mf-f2 ^* , the front motor rotation speed ω _mf , and the voltage V _dc of the battery 13 are associated in advance with the dq-axis current command values i _df ^* , i _qf ^* for the front motor 21 through experiments, simulations, or the like. Therefore, the current command value calculation unit 45 refers to a front current command value table to calculate dq-axis current command values i _df ^* , i _qf ^* for the front motor 21 based on the front final torque command value T _mf-f2 ^* , the front motor rotation speed ω _mf , and the voltage V _dc of the battery 13. Similarly, the current command value calculation unit 45 holds, for example, a rear current command value table (not shown). The rear current command value table is a lookup table in which the rear final torque command value T _mr-f2 ^* , the rear motor rotation speed ω _mr , and the voltage V _dc of the battery 13 are associated in advance with the dq-axis current command values i _dr ^* , i _qr ^* for the rear motor 31 through experiments, simulations, or the like. Therefore, by referring to a rear current command value table, the current command value calculation unit 45 calculates dq-axis current command values i _dr ^* , i _qr ^* for the rear motor 31 based on the rear final torque command value T _mr-f2 ^* , the rear motor rotation speed ω _mr , and the voltage V _dc of the battery 13. When vibration damping control calculation processing is performed, the values used for the front final torque command value T _mf-f2 ^* and the rear final torque command value T _mr-f2 ^* after the vibration damping control calculation processing are used.

The current control calculation unit 46 performs current control calculation processing to calculate each PWM signal input to the front inverter 23 and rear inverter 33.

Specifically, first, the current control calculation unit 46 calculates dq-axis currents i _df and i _qf (not shown) of the front motor 21 based on the currents i _uf , i _vf , and i _wf and the rotor phase α _f of the front motor 21. Similarly, the current control calculation unit 46 calculates dq-axis currents i _dr and i _qr (not shown) of the rear motor 31 based on _the currents i _ur , i _vr , and i wr of the rear motor 31 and the rotor phase α _r .

Next, the current control calculation unit 46 calculates dq-axis voltage command values _vdf ^* , _vqf ^* (not shown) for the front motor 21 based on the deviation between the dq-axis currents idf, iqf of the front motor 21 and the dq-axis current command values _idf ^* , _iqf ^* . Similarly, the current control calculation unit 46 calculates dq-axis voltage command values _vdr ^* , _vqr ^* (not shown) for _the rear motor 31 based on the deviation between _the dq-axis currents _idr , _iqr of the rear motor 31 and the dq-axis current command values _idr ^* , _iqr ^* . Note that in the calculation of the dq-axis voltage command values _vdf ^* , _vqf ^* for the front motor 21 and the dq-axis voltage command values _vdr ^* , _vqr ^* for the rear motor 31, decoupling control may be applied in order to suppress currents due to interference between the d and q axes.

Thereafter, the current control calculation unit 46 calculates voltage command values v _uf ^* , v _vf *, v _wf ^* (not shown) for each phase of the front motor 21 based on the dq-axis voltage command values v _df ^* , v _qf ^* and the rotor phase α _f of the front motor 21. Similarly, the current control calculation unit 46 calculates voltage command values v _ur ^* , v _vr ^* , v _wr ^* (not shown ⁾ for each phase of the rear motor 31 based on the dq-axis voltage command values v _dr ^* , v _qr ^* and the rotor phase α _r of the rear motor 31.

The current control calculation unit 46 then calculates a PWM signal to be input to the front inverter 23 based on the voltage command values v _uf ^* , v _vf ^* , v _wf ^* for each phase of the front motor 21 and the voltage _Vdc of the battery 13. Similarly, the current control calculation unit 46 calculates a PWM signal to be input to the rear inverter 33 based on the voltage command values v _ur ^* , v _vr ^* , v _wr ^* for each phase of the rear motor 31 and the voltage _Vdc of the battery 13.

The front inverter 23 and the rear inverter 33 open and close their switching elements in response to the PWM signals calculated as described above, thereby driving the front motor 21 and the rear motor 31 to output torques corresponding to the front final torque command value T _mf-f2 ^* and the rear final torque command value T _mr-f2 ^* .

[Configuration of basic torque calculation unit]
3 is a graph showing an example of an accelerator opening-torque table. The accelerator opening-torque table is determined in advance through experiments, simulations, etc. In this embodiment, the total torque calculation unit 47 references this accelerator opening-torque table to set the total torque T _m1 ^* based on the front motor rotation speed ω _mf and the accelerator opening A _po .

Figure 4 is a block diagram showing the configuration of the torque distribution calculation unit 48. As shown in Figure 4, the torque distribution calculation unit 48 includes a total torque limiting unit 51, a front wheel distribution gain multiplication unit 52, and a rear wheel distribution gain multiplication unit 53.

The total torque limiting unit 51 limits the total torque T _m1 ^* based on the rate of change of the front motor rotational speed ω _mf or the rate of change of the rear motor rotational speed ω _mr . Specifically, the total torque limiting unit 51 differentiates the front motor rotational speed ω _mf and the rear motor rotational speed ω _mr . Then, when the front motor rotational speed ω _mf is greater than the rear motor rotational speed ω _mr , the total torque limiting unit 51 limits the total torque T _m1 ^* in accordance with the differentiated value of the rear motor rotational speed ω _mr . On the other hand, when the rear motor rotational speed ω _mr is greater than the front motor rotational speed ω _mf , the total torque limiting unit 51 limits the total torque T _m1 ^* in accordance with the differentiated value of the front motor rotational speed ω _mf . In other words, when the front wheels 22 slip, the total torque limiting unit 51 limits the total torque T _m1 ^* based on the rate of change of the rotation speed of the rear wheels 32 that are not slipping, and when the rear wheels 32 slip, the total torque limiting unit 51 limits the total torque T _m1 ^* based on the rate of change of the rotation speed of the front wheels 22 that are not slipping.

In this embodiment, the total torque limiting unit 51 limits the total torque T m1 * as described above when the magnitude of the derivative of the front motor rotation speed ω _mf or the rear motor rotation speed ω _mr is equal to or greater than a predetermined threshold value ^β (not shown). That is, the total torque limiting unit 51 limits the total torque _{T m1} ^* when a sudden slip occurs in the front wheels 22 or the rear wheels 32. The total torque limiting unit 51 does not limit the total torque T _m1 ^* when neither the front wheels 22 nor the rear wheels 32 are slipping, or when the front wheels 22 or the rear wheels 32 are slipping but the slip is not sudden. The threshold value β is determined in advance through experiments, simulations, or the like. The total torque limiting unit 51 limits the basic total torque T _m1 ^* by subtracting a value obtained by multiplying the magnitude of the differential value of the front motor rotation speed ω _mf or the rear motor rotation speed ω _mr by a predetermined gain γ (not shown) from the total torque T _m1 ^* , and calculates the limited total torque T _m2 ^* . The gain γ is determined in advance through experiments, simulations, etc.

The front wheel distribution gain multiplication unit 52 calculates the front basic torque Tmf ^{* by multiplying the limited total torque Tm2*} _{( if} the total torque _Tm1 ^* is not limited, it is essentially the total torque _Tm1 ^{* )} by the front wheel distribution gain _Kf . The front wheel distribution gain Kf is determined in advance between "0" and "1" depending on the settings of the control mode of the electric vehicle 10, etc.

The rear wheel distribution gain multiplication unit 53 calculates the rear basic torque T mr ^* by multiplying the limited total torque T _m2 ^* (effectively the total torque T _m1 ^* if the total torque T _m1 ^* is not limited) by the rear wheel distribution gain "1- _{K f} ".

[Configuration of slip control calculation unit]
FIG. 5 is an explanatory diagram of the equations of motion of the electric vehicle 10. As shown in FIG. 5, the torque transmission system of the electric vehicle 10 is modeled. Therefore, the equations of motion of the electric vehicle 10 are expressed by the following equations (1) to (4). The parameters used in FIG. 5 and the equations of motion are as follows. The auxiliary symbols "f" and "r" for each parameter represent "front" and "rear," respectively. Note that the equations of motion below do not take into account torque due to disturbances such as torsion of the drive shafts 27 and 37 and reaction forces from the road surface (hereinafter referred to as "disturbance torque").

_Jmf , _Jmr : Motor inertia _Jwf , _Jwr : Drive shaft inertia (for one shaft)
_Nf , _Nr : Overall gear ratio _ωmf , _ωmr : Motor rotation speed _Tmf , _Tmr : Motor torque _Tdf , _Tdr : Drive shaft torque

According to the above equations of motion, the transfer characteristic G _pf (s) from the front motor torque T _mf to the front motor rotation speed ω _mf and the transfer characteristic G _pr (s) from the rear motor torque T _mr to the rear motor rotation speed ω _mr are expressed by the following equations (5) to (7). The slip control calculation unit 43 is configured using the transfer characteristic G _pf (s) and the transfer characteristic G _pr (s). Note that "s" is a Laplace operator.

Figure 6 is a block diagram showing the configuration of the slip control calculation unit 43. As shown in Figure 6, the slip control calculation unit 43 includes a slip determination unit 61, a front/rear rotation difference target value calculation unit 62, a front slip control calculation unit 63, a rear slip control calculation unit 64, and a front/rear torque command value calculation unit 65.

The slip determination unit 61 determines whether slip has occurred on the front wheels 22 or the rear wheels 32 based on the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr . The slip determination unit 61 outputs the result of this determination to the front/rear torque command value calculation unit 65 as a front slip flag _SFf and a rear slip flag _SFr .

The front-rear difference rotation target value calculation unit 62 calculates a front-rear difference rotation target value ω _mfr ^* based on the steering rotation angle θ _str and the vehicle body speed V. The front-rear difference rotation target value ω _mfr ^* is a target value for the difference in rotation speed between the front wheels 22 and the rear wheels 32 (hereinafter referred to as the differential rotation ω _mfr ), and represents the differential rotation ω _mfr that should be generated depending on the steering situation of the electric vehicle 10. For example, when the steering rotation angle θ _str is zero and the electric vehicle 10 is traveling straight, the front-rear difference rotation target value ω _mfr ^* is zero. When the electric vehicle 10 is turning to the left or right, the front-rear difference rotation target value ω _mfr ^* has a value that depends on the steering rotation angle θ _str and the vehicle body speed V. The front-rear difference rotation target value ω _mfr ^* is input to a front slip control calculation unit 63 and a rear slip control calculation unit 64.

The front slip control calculation unit 63 calculates a front slip control torque T _mf-slip ^* based on the front motor rotation speed ω _mf , the rear motor rotation speed ω _mr , and the target front/rear rotation difference value ω _mfr ^* . In principle, the front slip control torque T _mf-slip ^* represents a target value for the output torque of the front motor 21 when the front motor rotation speed ω _mf is made to match the rear motor rotation speed ω _mr . In other words, when the front motor 21 is driven to produce an output torque represented by the front slip control torque T mf _- slip ^* , the front motor rotation speed ω _mf will substantially match the rear motor rotation speed ω _mr . Therefore, for example, when the front wheels 22 slip, controlling the front motor 21 to produce an output torque equivalent to the front slip control torque T _mf-slip ^* will substantially eliminate or suppress slip of the front wheels 22. The front slip control torque T _mf-slip ^* is input to the front/rear torque command value calculation unit 65 .

The rear slip control calculation unit 64 calculates rear slip control torque T _mr-slip ^* based on the front motor rotational speed ω _mf , the rear motor rotational speed ω _mr , and the target front/rear rotation difference value ω _mfr ^* . In principle, the rear slip control torque T _mr-slip ^* represents a target value for the output torque of the rear motor 31 when "the rear motor rotational speed ω _mr is made to match the front motor rotational speed ω _mf ." In other words, when the rear motor 31 is driven to produce an output torque represented by the rear slip control torque T _{mr-slip*, the rear motor rotational speed ω mr substantially matches the front motor rotational speed ω mf. Therefore, when the rear wheel 32 slips, if the rear motor 31 is controlled to produce an output torque equivalent to the rear slip control torque T mr-slip} ^* , slip of the rear wheel 32 is substantially eliminated or suppressed. The rear slip control torque T _mr-slip ^* is input to the front/rear torque command value calculation unit 65 .

Note that "matching" the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr means making the front motor rotation speed _ωmf substantially equal to the rear motor rotation speed _ωmr , or making the rear motor rotation speed _ωmr substantially equal to the front motor rotation speed _ωmf , when the target front-rear rotation difference value _ωmfr ^* is zero. When the target front-rear rotation difference value _ωmfr ^* is a value other than zero, "matching" means making the front motor rotation speed _ωmf or the rear motor rotation speed _ωmr substantially equal to a predetermined rotation speed where the rotation difference _ωmfr corresponding to the target front-rear rotation difference value _ωmfr ^* is a certain rotation speed. For example, the state in which the front motor rotation speed _ωmf matches the rear motor rotation speed _ωmr is when the front motor rotation speed _ωmf is substantially equal to _ωmr + | _ωmfr ^* | or _ωmr - | _ωmfr ^* |, with the rear motor rotation speed _ωmr as the reference. The same applies to the case where the rear motor rotation speed ω _mr is made to "match" the front motor rotation speed ω _mf .

The front/rear torque command value calculation unit 65 calculates a front final torque command value T _{mf-f2 *} ^and a rear final torque command value T mr-f2 ^* based on the front basic torque T _mf ^* and the rear basic torque T _mr ^* , the front slip flag SF _f and the rear slip flag SF _r , and the front slip control torque T _mf-slip ^* and the rear slip control torque T _mr-slip ^* .

The specific configuration of each of the above components that make up the slip control calculation unit 43 is described in detail below.

[Specific Configuration of Slip Determination Unit]
7 is a block diagram showing the configuration of the slip determination unit 61. As shown in FIG. 7, the slip determination unit 61 includes a differential rotation calculation unit 71 and a slip flag calculation unit 72.

The differential rotation speed calculation unit 71 calculates the deviation between the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr , i.e., the differential rotation speed _ωmfr . In this embodiment, the differential rotation speed calculation unit 71 calculates the differential rotation speed _ωmfr by subtracting the rear motor rotation speed _ωmr from the front motor rotation speed _ωmf . The differential rotation speed _ωmfr is input to the slip flag calculation unit 72.

The slip flag calculation unit 72 calculates a front slip flag _SFf and a rear slip flag _SFr based on the differential rotation speed _ωmfr and a predetermined rotation speed threshold value ωm _-th . Specifically, the slip flag calculation unit 72 calculates the front slip flag _SFf and the rear slip flag _SFr according to the following equations (8) and (9). For the front slip flag _SFf and the rear slip flag _SFr , "1" indicates "slip" and "0" indicates "non-slip."

As shown in equations (8) and (9), when the front motor rotation speed _ωmf is greater than the rear motor rotation speed _ωmr and the absolute value of the differential rotation speed _ωmfr is equal to or greater than the rotation speed threshold value _ωm-th , the front slip flag _SFf is set to "1" (slip) and the rear slip flag _SFr is set to "0" (non-slip).Furthermore, when the rear motor rotation speed _ωmr is greater than the front motor rotation speed _ωmf and the absolute value of the differential rotation speed _ωmfr is equal to or greater than the rotation speed threshold value _ωm-th , the front slip flag _SFf is set to "0" (non-slip) and the rear slip flag _SFr is set to "1" (slip). That is, when the absolute value of the differential rotation speed ω _mfr is equal to or greater than the rotation speed threshold value ω _{m-th ,} it is determined that the front motor rotation speed ω _mf is greater than the rear motor rotation speed ω _mr , or that the rear motor rotation speed ω _mr is greater than the front motor rotation speed ω mf, depending on the sign of the differential rotation speed ω _mfr .

In this embodiment, the rotation speed threshold ω _m-th is a variable threshold that changes depending on the target front-rear rotation difference value ω _mfr ^* . The rotation speed threshold ω _m-th is set to increase as the ^target front-rear rotation difference value ω mfr _* increases. For example, the rotation speed threshold ω _m-th is calculated by adding or subtracting the target front-rear rotation difference value ω _mfr ^* to a predetermined reference value. In this way, by making the rotation speed threshold ω _m-th variable, the rotation speed threshold ω _m-th becomes an appropriate value depending on the turning state of the electric vehicle 10. Note that the rotation speed threshold ω _m-th may be a fixed value that is determined in advance through experiments, simulations, or the like.

[Specific configuration of the front/rear rotation difference target value calculation unit]
8 is a block diagram showing the configuration of the front/rear rotation difference target value calculation unit 62. As shown in FIG. 8, the front/rear rotation difference target value calculation unit 62 includes a first multiplication unit 81 and a second multiplication unit 82.

The first multiplier 81 multiplies the steering rotation angle θ _str by the vehicle speed V.

The second multiplier 82 calculates the target front-rear rotation difference value ω _mfr ^* by further multiplying the product of the steering rotation angle θ _str and the vehicle speed V by a gain K _θV . The gain K _θV is determined in advance by experiment, simulation, or the like.

In this embodiment, the front-rear rotation difference target value calculation unit 62 includes the first multiplication unit 81 and the second multiplication unit 82 as described above, but is not limited to this. The front-rear rotation difference target value calculation unit 62 may be configured to receive the steering rotation angle θ _str , the vehicle body speed V, the yaw rate sensor value (not shown), etc. as inputs, and to store the corresponding front-rear rotation difference target value ω _mfr ^* in a map or the like.

[Specific Configuration of Front Slip Control Calculation Unit]
Fig. 9 is a block diagram showing the configuration of the front slip control calculation unit 63. As shown in Fig. 9, the front slip control calculation unit 63 includes a front rotation speed target value calculation unit 91 (first or second rotation speed target value calculation unit), a rotation speed control unit 92, a disturbance torque estimation unit 93, and a disturbance torque compensation unit 94.

The front rotation speed target value calculation unit 91 calculates a front rotation speed target value _ωmf ^* , which is a target value for the front motor rotation speed _ωmf , based on the rear motor rotation speed _ωmr . In this embodiment, the front rotation speed target value calculation unit 91 calculates the front rotation _speed target value _ωmf ^* by adding the front/rear difference rotation target value _ωmfr ^* to the rear motor rotation speed ωmr. This front rotation speed target value _ωmf ^* is a rotation speed target value for making the front motor rotation speed _ωmf equal to the rear motor rotation speed _ωmr . When the electric vehicle 10 is traveling straight and the front/rear difference rotation target value _ωmfr ^* is zero, the front rotation speed target value _ωmf ^* is equal to the rear motor rotation speed _ωmr . The front rotation speed target value _ωmf ^* is input to the rotation speed control unit 92.

When the absolute value of the steering rotation angle θ _str is equal to or less than a predetermined threshold value and it is determined that the electric vehicle 10 is traveling substantially straight, the front motor rotation speed ω _mf and the rear motor rotation speed ω _mr may be made to match by omitting the addition of the front/rear rotation difference target value ω _mfr ^* in the front rotation speed target value calculation unit 91. In this case, the straight-line stability of the electric vehicle 10 is improved near the center of the steering.

The rotation speed control unit 92 (first or second rotation speed control torque calculation unit) calculates a front rotation speed control torque _Tωf based on the front motor rotation speed _ωmf and the front rotation speed target value _ωmf ^* . The front rotation speed control torque _Tωf is a target value of the torque that should be output by the front motor 21 when the front motor rotation speed _ωmf is made to match the rear motor rotation speed _ωmr .

Figure 10 is a block diagram showing the configuration of the rotation speed control unit 92 in the front slip control calculation unit 63. As shown in Figure 10, the rotation speed control unit 92 includes a rotation speed deviation calculation unit 101 and a front model matching compensation unit 102.

The rotation speed deviation calculation unit 101 calculates a front rotation speed deviation Δω _mf , which is the deviation between the front motor rotation speed ω _{mf and the front rotation speed target value ω mf *} ^. The front rotation speed deviation Δω _mf is input to the front model matching compensation unit 102.

The front model matching compensation unit 102 calculates the front rotation speed control torque T _ωf by filtering the front rotation speed deviation Δω _mf with a filter formed by a transfer characteristic G _pf (s) and a low-pass filter R ₁ (s). The front model matching compensation unit 102 is expressed, for example, by R ₁ (s)/{G _pf (s) (1 - R ₁ (s))}. The time constant of the low-pass filter R ₁ (s) is determined in advance by experiment, simulation, or the like.

A disturbance torque estimating section 93 (see FIG. 9) calculates the disturbance torque acting on the front motor 21 (hereinafter referred to as front disturbance torque T _df ) based on the dynamic characteristics of the drive shaft 27, which is the drive shaft. In this embodiment, the disturbance torque estimating section 93 receives the front motor rotation speed ω _mf and the front slip control torque T _mf-slip ^* (previous value) as inputs, and outputs the front disturbance torque T _df .

Figure 11 is a block diagram showing the configuration of the disturbance torque estimation unit 93 in the front slip control calculation unit 63. As shown in Figure 11, the disturbance torque estimation unit 93 includes a first front motor torque estimation unit 111, a second front motor torque estimation unit 112, and a front disturbance torque calculation unit 113.

The first front motor torque estimator 111 calculates (estimates) a first front motor torque estimated value T _mf1 ^ by filtering the front motor rotation speed ω _mf with a filter configured with a transfer characteristic G _pf (s) and a low-pass filter H(s). The first front motor torque estimator 111 is expressed, for example, by H(s)/G _pf (s). The low-pass filter H(s) is expressed by the following equation (10). The time constant τ _V is determined in advance by experiment, simulation, or the like.

The second front motor torque estimator 112 calculates (estimates) the second front motor torque estimated value T _mf2 ^ by filtering the front slip control torque T _mf-slip ^* (previous value) with a low-pass filter H(s).

The front disturbance torque calculation unit 113 calculates the front disturbance torque _{Tdf based on the first front motor torque estimate value Tmf1^ and the second front motor torque estimate value Tmf2^. In this embodiment, the front disturbance torque calculation unit 113 calculates the front disturbance torque Tdf by subtracting the} second front motor torque estimate value _Tmf2 ^ from the first front motor torque estimate value _Tmf1 ^.

The disturbance torque compensation section 94 (see FIG. 9) calculates the front slip control torque T _{mf-slip *} by compensating for the front disturbance torque T _df based on the front rotation speed control torque T _ωf and the front disturbance torque T _df . Specifically, the disturbance torque compensation section 94 calculates the front slip control torque T mf-slip ^* with the front disturbance torque T _df compensated for by subtracting the front disturbance torque T _df from the front rotation speed control torque ^T _ωf .

[Specific Configuration of Rear Slip Control Calculation Unit]
Fig. 12 is a block diagram showing the configuration of the rear slip control calculation unit 64. As shown in Fig. 12, the rear slip control calculation unit 64 includes a rear rotation speed target value calculation unit 121 (first or second rotation speed target value calculation unit), a rotation speed control unit 122 (first or second rotation speed control torque calculation unit), and a disturbance torque estimation unit 123. The components constituting the rear slip control calculation unit 64 are symmetrical to the components constituting the front slip control calculation unit 63, except that parameters for the rear drive system 12 are used.

The rear rotation speed target value calculation unit 121 calculates a rear rotation speed target value _ωmr ^* , which is a target value for the rear motor rotation speed _ωmr , based on the front motor rotation speed _ωmf . In this embodiment, the rear rotation speed target value calculation unit 121 calculates the rear rotation speed target value _ωmr * by subtracting the front/rear differential rotation target value _ωmfr ^* from the front motor rotation speed _ωmf . ^This rear rotation speed target value _ωmr ^* is a rotation speed target value for making the rear motor rotation speed _ωmr equal to the front motor rotation speed _ωmf . When the electric vehicle 10 is traveling straight and the front/rear differential rotation target value _ωmfr ^* is zero, the rear rotation speed target value _ωmr ^* is equal to the front motor rotation speed _ωmf . The rear rotation speed target value _ωmr ^* is input to the rotation speed control unit 122.

When the absolute value of the steering rotation angle θ _str is equal to or less than a predetermined threshold value and it is determined that the electric vehicle 10 is traveling substantially straight, the front motor rotation speed ω _mf and the rear motor rotation speed ω _mr may be made to match by omitting the subtraction of the front/rear rotation difference target value ω _mfr ^* in the rear rotation speed target value calculation unit 121. In this case, the straight-line stability of the electric vehicle 10 is improved near the center of the steering.

The rotation speed control unit 122 calculates a rear rotation speed control torque T _ωr based on the rear motor rotation speed ω _mr and the rear rotation speed target value ω _mr ^* . The rear rotation speed control torque T _ωr is a target value of the torque that should be output by the rear motor 31 when the rear motor rotation speed ω _mr is made to match the front motor rotation speed ω _mf .

Figure 13 is a block diagram showing the configuration of the rotation speed control unit 122 in the rear slip control calculation unit 64. As shown in Figure 13, the rotation speed control unit 122 includes a rotation speed deviation calculation unit 131 and a rear model matching compensation unit 132. These units are configured symmetrically to the respective units of the rotation speed control unit 92 in the front slip control calculation unit 63, except that they use parameters for the rear drive system 12.

The rotation speed deviation calculation unit 131 calculates a rear rotation speed deviation Δω _mr , which is the deviation between the rear motor rotation speed ω _{mr and the rear rotation speed target value ω mr *} ^. The rear rotation speed deviation Δω _mr is input to the rear model matching compensation unit 132.

The rear model matching compensation unit 132 calculates the rear rotation speed control torque T _ωr by filtering the rear rotation speed deviation Δω _mr with a filter formed by the transfer characteristic G _pr (s) and a low-pass filter R ₁ (s). The rear model matching compensation unit 132 is expressed, for example, by R ₁ (s)/{G _pr (s) (1 - R ₁ (s))}.

The disturbance torque estimating section 123 (see FIG. 12) calculates the disturbance torque acting on the rear motor 31 (hereinafter referred to as rear disturbance torque _Tdr ) based on the dynamic characteristics of the drive shaft 37, which is the drive shaft. In this embodiment, the disturbance torque estimating section 123 receives the rear motor rotation speed _ωmr and the rear slip control torque Tmr _-slip ^* (previous value) as inputs, and outputs the rear disturbance torque _Tdr .

Figure 14 is a block diagram showing the configuration of the disturbance torque estimation unit 123 in the rear slip control calculation unit 64. As shown in Figure 14, the disturbance torque estimation unit 123 includes a first rear motor torque estimation unit 141, a second rear motor torque estimation unit 142, and a rear disturbance torque calculation unit 143. These have a symmetrical configuration corresponding to the respective units of the disturbance torque estimation unit 93 in the front slip control calculation unit 63, except that parameters for the rear drive system 12 are used.

The first rear motor torque estimator 141 calculates (estimates) a first rear motor torque estimated value T _mr1 ^ by filtering the rear motor rotation speed ωmr with a filter formed by the transfer characteristic G _pr (s) and a low-pass filter H(s). The first rear motor torque estimator 141 is expressed, for example, by H(s)/G _pr (s).

The second rear motor torque estimating section 142 calculates (estimates) the second rear motor torque estimated value T _mr2 ^ by filtering the rear slip control torque T _mr-slip ^* (previous value) with a low-pass filter H(s).

The rear disturbance torque calculation unit 143 calculates the rear disturbance torque _Tdr based on the first rear motor torque estimated value _Tmr1 ^ and the second rear motor torque estimated value _Tmr2 ^. In this embodiment, the rear disturbance torque calculation unit 143 calculates the rear disturbance torque _Tdr by subtracting the second rear motor torque estimated value _Tmr2 ^ from the first rear motor torque estimated value _Tmr1 ^.

The disturbance torque compensation section 124 (see FIG. 12) calculates the rear slip control torque T _mr-slip ^* by compensating for the rear disturbance torque T _dr based on the rear rotation speed control torque T _ωr and the rear disturbance torque T _dr . Specifically, the disturbance torque compensation section 124 calculates the rear slip control torque T _mr -slip * in which the rear disturbance torque T _dr has been compensated for by subtracting the rear disturbance torque T _dr from the rear rotation speed control torque ^{T ωr} _.

[Specific configuration of the longitudinal torque command value calculation unit]
15 is a block diagram showing the configuration of the front/rear torque command value calculation unit 65. As shown in FIG. 15, the front/rear torque command value calculation unit 65 includes a front final torque command value calculation unit 151 and a rear final torque command value calculation unit 152.

The front final torque command value calculation unit 151 includes a rotation speed control torque limit unit 161 (LIM), a torque command value switching unit 162, a correction unit 163, a torque deviation calculation unit 164, and a change rate limit unit 165 (rate limit).

When the front slip control torque T _mf-slip ^* exceeds the front basic torque T _mf ^* , the rotation speed control torque limiting section 161 limits the value of the front slip control torque T _mf-slip ^* to the value of the front basic torque T _mf ^* . In other words, the rotation speed control torque limiting section 16 limits the front slip control torque T _mf-slip ^* to be equal to or less than the front basic torque T _mf ^* .

The torque command value switching unit 162 outputs either the front basic torque T _mf ^* or the front slip control torque T _mf-slip ^* as the first front final torque command value T _mf-f1 ^* based on the front slip flag SF _f . When the front slip flag SF _f is "0" and the front wheels 22 are not slipping, the torque command value switching unit 162 outputs the front basic torque T _mf ^* as the first front final torque command value T _mf-f1 ^* . On the other hand, when the front slip flag SFf is "1" and the front wheels 22 are slipping, the torque command value switching unit 162 outputs the front slip control torque T _mf-slip ^* as the first front final torque command value T _mf-f1 ^* .

The correction unit 163 calculates _{a (second) front final torque command value T mf-f2 * by correcting the first front final torque command value T mf-f1 * based on the rear torque deviation ΔT r} ^, _{which is} ^the _deviation ^between the rear basic torque T mr * and the rear slip control torque T _mr-slip ^* . In the present embodiment, the correction unit 163 calculates the front final torque command value T _mf-f2 ^* by adding the rear torque deviation ΔT _r to the first front final torque command value T _mf-f1 ^* .

The torque deviation calculation unit 164 calculates a front torque deviation _ΔTf , which is the deviation between the front basic torque _Tmf ^* and the first front final torque command value Tmf _-f1 ^* . In the present embodiment, the torque deviation calculation unit 164 calculates the front torque deviation _ΔTf by subtracting the first front final torque command value Tmf _-f1 ^* from the front basic torque _Tmf ^* . The front torque deviation _ΔTf is input to the correction unit 168 of the rear final torque command value calculation unit 152 via the change rate limiter 165. In other words, the front torque deviation _ΔTf represents the amount of torque transferred from the front motor 21 (front wheels 22) to the rear motor 31 (rear wheels 32).

The change rate limiting unit 165 limits the rate of change of the front torque deviation _ΔTf when the front torque deviation _ΔTf is input to the correction unit 168 of the rear final torque command value calculation unit 152. The limit value (upper limit value) for the rate of change of the front torque deviation _ΔTf is determined in advance through experiments, simulations, etc. The change rate limiting unit 165 prevents the rear wheels 32 from slipping due to a shift in torque equivalent to the front torque deviation _ΔTf when a sudden slip occurs in the front wheels 22.

The rear final torque command value calculation unit 152 includes a rotation speed control torque limiting unit 166 (LIM), a torque command value switching unit 167, a correction unit 168, a torque deviation calculation unit 169, and a change rate limiting unit 165 (rate limit). Each of these units has a symmetrical configuration corresponding to each unit of the front final torque command value calculation unit 151, except that parameters for the rear drive system 12 are used.

When the rear slip control torque T _mr-slip ^* exceeds the rear basic torque T _mr ^* , the rotation speed control torque limiting unit 166 limits the value of the rear slip control torque T _mr-slip ^* to the value of the rear basic torque T _mr ^* . In other words, the rotation speed control torque limiting unit 166 limits the rear slip control torque T _mr-slip ^* to be equal to or less than the rear basic torque T _mr ^* .

The torque command value switching unit 167 outputs either the rear basic torque T _mr ^* or the rear slip control torque T _mr-slip ^* as the first rear final torque command value T _mr-f1 ^* based on the rear slip flag _SFr . When the rear slip flag SFr is "0" and the rear wheels 32 are not slipping, the torque command value switching unit 167 outputs the rear basic torque T _mr ^* as the first rear final torque command value T _mr-f1 ^* . On the other hand, when the rear slip flag SFr is "1" and the rear wheels 32 are slipping, the torque command value switching unit 167 outputs the rear slip control torque T _mr-slip ^* as the first rear final torque command value T _mr-f1 ^* .

The correction unit 168 calculates a (second) rear final torque command value T _mr-f2 ^* by correcting the first rear final torque command value T _mr-f1 ^* based on the front torque deviation ΔT _f . In the present embodiment, the correction unit 168 calculates the rear final torque command value T _mr-f2 ^* by adding the front torque deviation ΔT _f to the first rear final torque command value T _mr-f1 ^* .

The torque deviation calculation unit 169 calculates the rear torque deviation _ΔTr . In this embodiment, the torque deviation calculation unit 169 calculates the rear torque deviation _ΔTr by subtracting the first rear final torque command value Tmr _-f1 ^* from the rear basic torque _Tmr ^* . The rear torque deviation _ΔTr is input to the correction unit 163 of the front final torque command value calculation unit 151 via the change rate limiter 170. In other words, the rear torque deviation _ΔTr represents the amount of torque transferred from the rear motor 31 (rear wheels 32) to the front motor 21 (front wheels 22).

The change rate limiting unit 170 limits the rate of change of the rear torque deviation _ΔTr when the rear torque deviation _ΔTr is input to the correction unit 163 of the front final torque command value calculation unit 151. The limit value (upper limit value) for the rate of change of the rear torque deviation _ΔTr is determined in advance through experiments, simulations, etc. The change rate limiting unit 170 prevents the front wheels 22 from slipping due to a shift in torque equivalent to the rear torque deviation _ΔTr when a sudden slip occurs in the rear wheels 32.

[Effect]
As described above, in the electric vehicle 10 according to this embodiment, when slippage occurs in the front wheels 22 or the rear wheels 32, rotation speed control is executed to match the rotation speed of the slipping drive wheel, either the front wheels 22 or the rear wheels 32, to the rotation speed of the other drive wheel that is not slipping. Then, the torque (driving force) that should be output by the slipping drive wheel is transferred to the other drive wheel that is not slipping. This eliminates or suppresses slippage. Below, the operation of the control of the electric vehicle 10 according to this embodiment will be described by comparison with a first comparative example and a second comparative example.

The comparison of the control of the electric vehicle 10 according to this embodiment with the control of the first and second comparative examples is performed for road surfaces and driving conditions that are prone to slippage, as follows. Specifically, the vehicle is traveling on a road surface (such as sand) where resistance increases depending on the amount of slippage, and while accelerating, at time t0, the vehicle enters an uphill road in a straight line while maintaining the same road surface conditions.

16 is a time chart showing longitudinal acceleration Acc _etc. when control of Comparative Example 1 is executed. Comparative Example 1 is a control in which torque (driving force) that should be output from one slipping drive wheel is transferred to the other non-slip drive wheel, without performing rotation speed control to match the rotation speed of one slipping drive wheel with the rotation speed of the other non-slip drive wheel.

FIG. 16(A) is a time chart showing the output torque of the front motor 21 (hereinafter referred to as front motor torque _Tmf ). The solid line in FIG. 16(A) is the front motor torque _Tmf . The dashed line in FIG. 16(A) is the front basic torque _Tmf ^* . FIG. 16(B) is a chime chart showing the front motor rotation speed _ωmf . The solid line in FIG. 16(B) is the front motor rotation speed ωmf. The dashed line in FIG. 16(B) is the vehicle speed V. FIG. 16(C) is a time chart showing the output torque of the rear motor 31 (hereinafter referred to as rear motor torque _Tmr ). The solid line in FIG. 16(C) is the rear motor torque _Tmr . The dashed line in FIG. 16(C) is the rear basic torque _Tmr ^* . FIG. 16(D) is a time chart showing the rear motor rotation speed _ωmr . The solid line in FIG. 16(D) is the rear motor rotation speed _ωmr . The dashed line in Fig. 16(D) represents vehicle speed V. Fig. 16(E) is a time chart showing longitudinal acceleration A _cc of the electric vehicle. The solid line in Fig. 16(E) represents longitudinal acceleration A _cc . The dashed line in Fig. 16(E) represents gradient resistance R _G.

As shown in Figures 16(B) and 16(D), when the vehicle enters an uphill road at time _t0 , the front axle load becomes insufficient until time _t1 , causing the front motor rotation speed _ωmf to relatively increase and the rear motor rotation speed _ωmr to relatively decrease. In other words, slippage occurs in the front wheels 22 from time _t0 to time _t1 . Therefore, as shown in Figures 16(A) and 16(C), torque is transferred from the front wheels 22 (front motor 21) to the rear wheels 32 (rear motor 31) after time _t1 . However, as shown in Figures 16(B) and 16(D), although the differential rotation speed ωmfr between the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr that occurs at time _t1 is reduced, _it is not sufficient, and slippage of the front wheels 22 is not completely suppressed. As a result, the resistance of the front wheels 22 increases, and at the same time, the increase in the torque of the rear wheels 32 (rear motor torque _Tmr ) saturates. 16(E), it is not possible to obtain a longitudinal acceleration _Acc sufficient to overcome the gradient resistance R _G. Therefore, in the control of the first comparative example, when the front wheels 22 slip, the vehicle speed V decreases, and the vehicle may decelerate or become stuck, even though the torque is transferred to the rear wheels 32.

Figure 17 is a time chart showing longitudinal acceleration and other changes when the control of the second comparative example is executed. Like the first comparative example, the second comparative example does not perform rotation speed control to match the rotation speed of one slipping drive wheel to the rotation speed of the other non-slip drive wheel, but instead transfers the torque (driving force) that should be output from one slipping drive wheel to the other non-slip drive wheel. However, the second comparative example is an example in which the control gain is increased compared to the first comparative example, and adjustments are made to increase the amount of torque transfer when slippage occurs.

Fig. 17(A) is a time chart showing front motor torque _Tmf . Fig. 17(B) is a time chart showing front motor rotation speed _ωmf . Fig. 17(C) is a time chart showing rear motor torque _Tmr . Fig. 17(D) is a time chart showing rear motor rotation speed _ωmr . Fig. 17(E) is a time chart showing longitudinal acceleration _Acc of the electric vehicle. The lines in Fig. 17 are the same as those in the example of Fig. 16 relating to the first comparative example.

As shown in Figures 17(B) and 17(D), when the vehicle enters an uphill road at time _t0 , the front axle load becomes insufficient until time _t1 , causing the front motor rotation speed _ωmf to become relatively large and the rear motor rotation speed _ωmr to become relatively small. In other words, slippage occurs in the front wheels 22 from time _t0 to time _t1 . This occurrence of slippage in the front wheels 22 is similar to that in the first comparative example. Then, as shown in Figures 17(A) and 17(C), after time _t1 , torque is transferred from the front wheels 22 (front motor 21) to the rear wheels 32 (rear motor 31), reducing the differential rotation speed _ωmfr that occurred at time _t1 .

However, in the control of the second comparative example, the control gain is set larger than in the control of the first comparative example, so that after time _t1 when the torque transfer starts, the front motor torque _Tmf and the rear motor torque _Tmr exhibit oscillatory behavior, as shown in Figures 17(A) and 17(C). As a result, the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr also oscillate, as shown in Figures 17(B) and 17(D).

Furthermore, in the second comparative example in which the control gain is set large, for example, at time _t2 , slip of the front wheels 22 is reduced, and resistance of the front wheels 22 is reduced. Therefore, the torque of the rear wheels 32 (rear motor torque T _mr ) can be increased. As a result, as shown in Figure 17 (E), the control of the second comparative example obtains a longitudinal acceleration _Acc that is sufficient to overcome the gradient resistance _RG . Therefore, the control of the second comparative example increases the vehicle speed V.

However, in the control of the second comparative example, the oscillations of the front motor torque _Tmf and the rear motor torque _Tmr , and the front motor rotation speed _ωmf and the rear motor rotation speed _ωmr continue after time _t1 and do not converge even at time _t2 , for example. In other words, in the control of the second comparative example, the unstable control state in which the front wheels 22 and the rear wheels 32 repeatedly slip and grip is not resolved.

FIG. 18 is a time chart showing longitudinal acceleration and the like when control according to this embodiment is executed. FIG. 18(A) is a time chart showing front motor torque T _mf . FIG. 18(B) is a time chart showing front motor rotation speed ω _mf . FIG. 18(C) is a time chart showing rear motor torque T _mr . FIG. 18(D) is a time chart showing rear motor rotation speed ω _mr . FIG. 18(E) is a time chart showing longitudinal acceleration A _cc of the electric vehicle. The lines in FIG. 18 are the same as those in FIG. 16 for the first comparative example and FIG. 17 for the second comparative example.

As shown in Figures 18(B) and 18(D), when the vehicle enters an uphill road at time _t0 , the front axle load becomes insufficient until time _t1 , causing the front motor rotation speed _ωmf to become relatively large and the rear motor rotation speed _ωmr to become relatively small. That is, from time _t0 to time _t1 , slippage occurs in the front wheels 22. This occurrence of slippage in the front wheels 22 is similar to the first and second comparative examples. Then, as shown in Figures 18(A) and 18(C), after time _t1 , torque is transferred from the front wheels 22 (front motor 21) to the rear wheels 32 (rear motor 31), reducing the differential rotation speed _ωmfr that occurred at time _t1 .

In this case, as shown in FIGS. 18A and 18C , the control according to this embodiment suppresses the torque (front motor torque T _mf ) of the slipping front wheel 22 more than in the second comparative example, and transfers the torque to the non-slip rear wheel 32. Therefore, from time _t1 to, for example, time _t2 , the differential rotation ω _mfr is sufficiently reduced. As a result, at time t2, the suppression of slippage of the front wheel 22 reduces the resistance of the front wheel 22, and at the same time, it becomes possible to increase the torque of the rear wheel 32. Therefore, as shown in FIG. 18E , the control according to this embodiment obtains a longitudinal acceleration _Acc that overcomes the gradient resistance _RG , and can increase the vehicle speed V. In other words, the control according to this embodiment enables the electric vehicle 10 to climb hills without getting stuck, even when traveling on a road surface prone to slippage, such as a sandy slope. This is because the control according to this embodiment, unlike the second comparative example, performs rotation speed control to match the rotation speed of the slipping front wheel 22 (front motor rotation speed ω _mf ) with the rotation speed of the non-slipping rear wheel 32 (rear motor rotation speed ω _mr ), and then transfers torque from the front wheel 22 to the rear wheel 32.

As described above, the control method for an electric vehicle according to this embodiment is a control method for an electric vehicle that has first drive wheels (e.g., front wheels 22) driven by a first motor (e.g., front motor 21) and second drive wheels (e.g., rear wheels 32) driven by a second motor (e.g., rear motor 31) different from the first motor. In this control method for an electric vehicle, a total torque T _m1 ^* corresponding to the driving force required of the electric vehicle is calculated. Then, by distributing the total torque T _m1 ^* to the first motor and the second motor, a first basic torque (e.g., front basic torque T _mf ^* ) that is the torque to be output by the first motor and a second basic torque (e.g., rear basic torque T _mr ^* ) that is the torque to be output by the second motor are calculated.

Furthermore, a first rotation speed target value (e.g., front rotation speed target value _ωmf ^* ) which is a target value for the rotation speed of the first motor is calculated based on the rotation speed of the second motor (e.g., rear motor rotation speed _ωmr ). Similarly, a second rotation speed target value (e.g., rear rotation speed target value _{ωmr *} ) which is a target value for the rotation speed of the second motor is calculated based on the rotation speed of the first motor (e.g., front motor rotation speed ^ωmf ). Furthermore, a first rotation speed control torque (e.g., front rotation speed control torque _Tωf ) which is a torque to be output by the first motor is calculated based on the first rotation speed target value, and a second rotation speed control torque (e.g., rear rotation speed control torque _Tωr ) which is a torque to be output by the second motor is calculated based on the second rotation speed target value.

Then, (a) when the rotation speed of the first motor is greater than the rotation speed of the second motor, a first final torque command value (e.g., (second) front final torque command value T mf-f2*) that is the final torque command value for the first motor is calculated based on the first rotation speed control torque. Also, a second final torque command value (e.g., (second) rear final torque command value T _mr-f2 ^* ) that is the final torque command value for the second motor is calculated by correcting a second basic torque (e.g., rear basic torque T _mr ^* ) based on a first torque deviation (e.g., front torque deviation _{ΔT f} ) that is the deviation between the first basic torque ^and the first rotation speed control torque.

Conversely, (b) when the rotation speed of the second motor is greater than the rotation speed of the first motor, a first final torque command value (e.g., a (second) front final torque command value T mf-f2 *) is calculated by correcting the first basic torque (e.g., front basic torque T _mf ^* ) based on a second torque deviation (e.g., rear torque deviation _{ΔT r} ) which is the deviation between the second basic torque and the ^second rotation speed control torque. Also, a second final torque command value (e.g., rear rotation speed control torque T _ωr ) is calculated based on the second rotation speed control torque (e.g., rear rotation speed control torque T _ωr ).

The first motor and second motor are then driven based on the first final torque command value and second final torque command value calculated as described above.

As described above, in the control method for an electric vehicle according to the above embodiment, when one of the drive wheels slips, i.e., when a difference in rotation speed occurs, rotation speed control is performed to control the rotation speed of the slipping drive wheel toward a target value corresponding to the rotation speed of the non-slip drive wheel. After this rotation speed control is performed, the torque that should be output by the slipping drive wheel is transferred to the non-slip drive wheel. This control corrects the rotation speed difference when a difference in rotation speed occurs between drive wheels driven by different motors, and facilitates convergence to a stable control state in which rotation speed fluctuations are suppressed. In other words, compared to control that simply transfers the torque of the slipping drive wheel to the non-slip drive wheel in order to maintain the driving force that should be exerted by the electric vehicle 10, vibrations in the rotation speed, torque, etc. of the drive wheels can be reduced or suppressed. Furthermore, the rotation speed difference between the drive wheels is likely to be a value that corresponds to the road surface, maximizing the driving force transmitted to the road surface and preventing the electric vehicle 10 from getting stuck.

Furthermore, in the control method for an electric vehicle according to the above embodiment, when the rotation speed of the first motor (for example, front motor rotation speed ω _mf ) is greater than the rotation speed of the second motor (for example, rear motor rotation speed ω _mr ), the second final torque command value (for example, rear final torque command value T _{mr - f2} ^* ) is calculated by adding the first torque deviation (for example, front torque deviation ΔT _f ) to the second basic torque (for example, rear basic torque T _mr ^* ). Furthermore, when the rotation speed of the second motor (for example, rear motor rotation speed ω _mr ) is greater than the rotation speed of the first motor (for example, front motor rotation speed ω _mf ), the first final torque command value (for example, front final torque command value T _{mf - f2} ^* ) is calculated by adding the second torque deviation (for example, rear torque deviation ΔT _r ) to the first basic torque (for example, front basic torque T _mf ^* ).

In this way, by controlling the rotation speed, the output torque that is reduced at the slipping drive wheel is added to the drive wheel that is not slipping and output, thereby simply and reliably maintaining the driving force of the electric vehicle 10 despite control that prioritizes adjustment of the rotation speed.

In the control method for an electric vehicle according to the above embodiment, a predetermined upper limit is set for the rate of change of the first torque deviation (e.g., front torque deviation ΔT _f ) used in calculating the second final torque command value and the rate of change of the second torque deviation (e.g., rear torque deviation ΔT _r ) used in calculating the first final torque command value in the change rate limiting units 165, 170. By limiting the first torque deviation and the second torque deviation in this manner, slip of a slipping drive wheel is quickly suppressed, and the transfer of torque makes it less likely that slip will occur in a drive wheel that was not slipping.

In the control method for an electric vehicle according to the above embodiment, the first rotation speed target value and the second rotation speed target value (front rotation speed target value _ωmf ^* and rear rotation speed target value _ωmr ^* ) are calculated based on the vehicle speed V and the rotation angle of the steering wheel (steering rotation angle _θstr ). By determining the first rotation speed target value and the second rotation speed target value in this manner, the differential rotation speed _ωmfr required depending on the turning behavior of the electric vehicle 10 can be taken into consideration. As a result, during turning, interference between the drive wheels is suppressed, for example, by limiting the front motor torque _Tmf , and a decrease in yaw rate, for example, is prevented. In other words, even when the electric vehicle 10 is turning, slip control based on the rotation speed is performed, and a driving force appropriate for the turning behavior can be obtained.

In the control method for an electric vehicle according to the above embodiment, a first rotation speed control torque (e.g., front rotation speed control torque _Tωf ) is the torque that should be output by the first motor when the rotation speed of the first motor matches the rotation speed of the second motor. And a second rotation speed control torque (e.g., rear rotation speed control torque _Tωr ) is the torque that should be output by the second motor when the rotation speed of the second motor matches the rotation speed of the first motor. In this way, by matching the rotation speed of a slipping drive wheel to the rotation speed of a non-slip drive wheel, the rotation speed difference is particularly corrected, and it is easy to converge to a stable control state in which rotation speed fluctuations are suppressed.

In the control method for an electric vehicle according to the above embodiment, a first rotation speed control torque (e.g., front rotation speed control torque _Tωf ) is calculated by a first model matching filter configured using a transfer characteristic Gpf( _s ) from the torque to the rotation speed of the first motor, based on a first rotation speed deviation (e.g., front rotation speed deviation _Δωmf ) which is the deviation between the rotation speed of the first motor and a first rotation speed target value. Also, a second rotation speed control torque (e.g., rear rotation speed control torque _Tωr ) is calculated by a second model matching filter configured using a transfer characteristic _Gpr (s) from the torque to the rotation speed of the second motor, based on a second rotation speed deviation (e.g., rear rotation speed deviation _Δωmr ) which is the deviation between the rotation speed of the second motor and a second rotation speed target value. These first and second model matching filters each include a low-pass filter _R1 (s). In this way, when each rotation speed control torque is calculated using a model matching filter including the low-pass filter R1(s), it is possible to prevent problems such as sudden acceleration when returning to a road surface where slip is less likely to occur (a so-called high μ road) from a state in which slip has been suppressed by the rotation speed control torque. Furthermore, slip of the drive wheels is easily corrected while minimizing any discomfort felt by the driver.

In the control method for an electric vehicle according to the above embodiment, a first disturbance torque acting on the first motor (e.g., front disturbance torque T _df ) and a second disturbance torque acting on the second motor (e.g., rear disturbance torque T _dr ) are estimated based on the dynamic characteristics of the drive shaft. When the rotation speed of the first motor is higher than the rotation speed of the second motor, a first final torque command value (e.g., front final torque command value T _mf-f2 ^* ) is calculated by compensating the first rotation speed control torque for the first disturbance torque. When the rotation speed of the second motor is higher than the rotation speed of the first motor, a second final torque command value (e.g., rear final torque command value T _mr-f2 ^* ) is calculated by compensating the second rotation speed control torque for the second disturbance torque. By compensating for the disturbance torque in this way, the rotation speed of a slipping drive wheel can be made to match a target value corresponding to the rotation speed of a non-slip drive wheel with particular accuracy.

In the control method for an electric vehicle according to the above embodiment, a differential rotation speed ω _mfr , which is the difference between the rotation speeds of the first motor and the second motor, is calculated. When the absolute value of the differential rotation speed ω _mfr is equal to or greater than the rotation speed threshold value ω _{m-th ,} it is determined that "the rotation speed of the first motor is greater than the rotation speed of the second motor" or "the rotation speed of the second motor is greater than the rotation speed of the first motor," depending on the sign of the differential rotation speed ω mfr. This determination allows for particularly accurate determination of drive wheel slip. As a result, it is possible to prevent erroneous determination of drive wheel slippage due to the differential rotation speed ω _mfr , which occurs when the electric vehicle 10 is turning, for example.

In the control method for an electric vehicle according to the above embodiment, the first rotation speed control torque (e.g., front rotation speed control torque _Tωf ) is limited to a first basic torque (e.g., front basic torque _Tmf ^* ) or less. Similarly, the second rotation speed control torque (e.g., rear rotation speed control torque _Tωr ) is limited to a second basic torque (e.g., rear basic torque _Tmr ^* ) or less. In this way, by ensuring that the torque generated by a slipping drive wheel does not exceed the basic torque, control is performed to reliably reduce slippage of the drive wheels. Furthermore, when the slippage of the drive wheels subsides, the torque target value is smoothly switched.

In the control method for an electric vehicle according to the above embodiment, when the rotation speed of the first motor is higher than the rotation speed of the second motor, the total torque T _m1 ^* is limited in accordance with the derivative of the rotation speed of the second motor. Also, when the rotation speed of the second motor is higher than the rotation speed of the first motor, the total torque T _m1 ^* is limited in accordance with the derivative of the rotation speed of the first motor. In this way, when a sudden slip occurs in the drive wheels, limiting the total torque T _m1 ^* prevents both the first drive wheels (e.g., the front wheels 22) and the second drive wheels (e.g., the rear wheels 32) from slipping.

The above describes embodiments of the present invention, but the configurations described in the above embodiments merely represent some of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

For example, in the above embodiments, the present invention is described as being implemented in an electric vehicle 10 having front wheels 22 driven by a front motor 21 and rear wheels 32 driven by a rear motor 31 different from the front motor 21, but this is not limiting. This embodiment can be suitably applied to any electric vehicle in which multiple drive wheels are driven by multiple different motors. For example, the present invention is also suitable for electric vehicles in which each of the four wheels is driven by a separate motor. The present invention is also suitable for electric vehicles equipped with so-called in-wheel motor drive wheels.

10: Electric vehicle, 11: Front drive system, 12: Rear drive system, 13: Battery, 14: Motor controller, 16: Rotation speed control torque limiter, 21: Front motor, 22: Front wheels, 23: Front inverter, 24: Rotation sensor, 25: Current sensor, 26: Front reducer, 27: Drive shaft, 31: Rear motor, 32: Rear wheels, 33: Rear inverter, 34: Rotation sensor, 35: Current sensor, 36: Rear reducer, 37: Drive shaft, 41: Input processing section, 42: Basic Torque calculation unit, 43: slip control calculation unit, 44: vibration damping control calculation unit, 45: current command value calculation unit, 46: current control calculation unit, 47: total torque calculation unit, 48: torque distribution calculation unit, 51: total torque limiting unit, 52: front wheel distribution gain multiplication unit, 53: rear wheel distribution gain multiplication unit, 61: slip determination unit, 62: differential rotation target value calculation unit, 63: front slip control calculation unit, 64: rear slip control calculation unit, 65: torque command value calculation unit, 71: differential rotation calculation unit, 72: slip flag calculation unit, 81: first multiplication unit, 82: second Squaring unit, 91: front rotation speed target value calculation unit, 92: rotation speed control unit, 93: disturbance torque estimator, 94: disturbance torque compensation unit, 101: rotation speed deviation calculation unit, 102: front model matching compensation unit, 111: first front motor torque estimator, 112: second front motor torque estimator, 113: front disturbance torque calculation unit, 121: rear rotation speed target value calculation unit, 122: rotation speed control unit, 123: disturbance torque estimator, 124: disturbance torque compensation unit, 131: rotation speed deviation calculation unit, 132: rear model Matching compensation unit, 141: First rear motor torque estimator, 142: Second rear motor torque estimator, 143: Rear disturbance torque calculator, 151: Front final torque command value calculator, 152: Rear final torque command value calculator, 161: Rotation speed control torque limiter, 162: Torque command value switching unit, 163: Correction unit, 164: Torque deviation calculator, 165: Change rate limiter, 166: Rotation speed control torque limiter, 167: Torque command value switching unit, 168: Correction unit, 169: Torque deviation calculator, 170: Change rate limiter

Claims (11)

A control method for an electric vehicle including a first drive wheel driven by a first motor and a second drive wheel driven by a second motor different from the first motor, the method comprising:
calculating a total torque corresponding to a driving force required for the electric vehicle;
calculating a first basic torque, which is a torque to be output by the first motor, and a second basic torque, which is a torque to be output by the second motor, by distributing the total torque to the first motor and the second motor;
calculating a first rotation speed target value, which is a target value for the rotation speed of the first motor, based on the rotation speed of the second motor;
calculating a second rotation speed target value, which is a target value for the rotation speed of the second motor, based on the rotation speed of the first motor;
calculating a first rotation speed control torque, which is a torque to be output by the first motor, based on the first rotation speed target value;
calculating a second rotation speed control torque, which is a torque to be output by the second motor, based on the second rotation speed target value;
(a) when the rotation speed of the first motor is greater than the rotation speed of the second motor;
calculating a first final torque command value, which is a final torque command value for the first motor, based on the first rotation speed control torque; and
calculating a second final torque command value that is a final torque command value for the second motor by correcting the second basic torque based on a first torque deviation that is a deviation between the first basic torque and the first rotation speed control torque;
(b) when the rotation speed of the second motor is greater than the rotation speed of the first motor;
Calculating the first final torque command value by correcting the first basic torque based on a second torque deviation, which is a deviation between the second basic torque and the second rotation speed control torque; and
calculating the second final torque command value based on the second rotation speed control torque;
driving the first motor and the second motor based on the first final torque command value and the second final torque command value;
A method for controlling an electric vehicle. 2. A control method for an electric vehicle according to claim 1,
When the rotation speed of the first motor is greater than the rotation speed of the second motor, the second final torque command value is calculated by adding the first torque deviation to the second basic torque;
When the rotation speed of the second motor is higher than the rotation speed of the first motor, the first final torque command value is calculated by adding the second torque deviation to the first basic torque.
A method for controlling an electric vehicle. 3. A control method for an electric vehicle according to claim 1 or 2,
a predetermined upper limit value is set for the rate of change of the first torque deviation used in the calculation of the second final torque command value and the rate of change of the second torque deviation used in the calculation of the first final torque command value;
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 3,
the first rotation speed target value and the second rotation speed target value are calculated based on a vehicle speed and a rotation angle of a steering wheel;
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 4,
the first rotation speed control torque is a torque that should be output by the first motor when the rotation speed of the first motor is equal to the rotation speed of the second motor;
The second rotation speed control torque is a torque that should be output by the second motor when the rotation speed of the second motor is equal to the rotation speed of the first motor.
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 5,
the first rotation speed control torque is calculated by a first model matching filter configured using a transfer characteristic from torque to rotation speed of the first motor, based on a first rotation speed deviation which is a deviation between the rotation speed of the first motor and the first rotation speed target value;
the second rotation speed control torque is calculated by a second model matching filter configured using a transfer characteristic from torque to rotation speed of the second motor, based on a second rotation speed deviation which is a deviation between the rotation speed of the second motor and the second rotation speed target value;
the first model matching filter and the second model matching filter include low-pass filters;
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 6,
estimating a first disturbance torque acting on the first motor and a second disturbance torque acting on the second motor based on a dynamic characteristic of a drive shaft;
when the rotation speed of the first motor is higher than the rotation speed of the second motor, the first final torque command value is calculated by compensating the first rotation speed control torque for the first disturbance torque;
When the rotation speed of the second motor is higher than the rotation speed of the first motor, the second final torque command value is calculated by compensating the second rotation speed control torque for the second disturbance torque.
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 7,
calculating a differential rotation, which is a deviation between the rotation speed of the first motor and the rotation speed of the second motor;
If the absolute value of the differential rotation is equal to or greater than a threshold value, it is determined that the rotation speed of the first motor is greater than the rotation speed of the second motor, or that the rotation speed of the second motor is greater than the rotation speed of the first motor, depending on the sign of the differential rotation.
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 8,
the first rotation speed control torque is limited to be equal to or less than the first basic torque,
The second rotation speed control torque is limited to be equal to or less than the second basic torque.
A method for controlling an electric vehicle. A control method for an electric vehicle according to any one of claims 1 to 9,
When the rotation speed of the first motor is higher than the rotation speed of the second motor, the total torque is limited in accordance with a differential value of the rotation speed of the second motor;
When the rotation speed of the second motor is higher than the rotation speed of the first motor, the total torque is limited in accordance with a differential value of the rotation speed of the first motor.
A method for controlling an electric vehicle. A control device for an electric vehicle including a first drive wheel driven by a first motor and a second drive wheel driven by a second motor different from the first motor,
a total torque calculation unit that calculates a total torque corresponding to a driving force required for the electric vehicle;
a torque distribution calculation unit that calculates a first basic torque, which is a torque to be output by the first motor, and a second basic torque, which is a torque to be output by the second motor, by distributing the total torque to the first motor and the second motor;
a first rotation speed target value calculation unit that calculates a first rotation speed target value, which is a target value for the rotation speed of the first motor, based on the rotation speed of the second motor;
a second rotation speed target value calculation unit that calculates a second rotation speed target value, which is a target value for the rotation speed of the second motor, based on the rotation speed of the first motor;
a first rotation speed control torque calculation unit that calculates a first rotation speed control torque, which is a torque to be output by the first motor, based on the first rotation speed target value;
a second rotation speed control torque calculation unit that calculates a second rotation speed control torque, which is a torque to be output by the second motor, based on the second rotation speed target value;
(a) a torque command value calculation unit that, when the rotation speed of the first motor is higher than the rotation speed of the second motor, calculates a first final torque command value that is a final torque command value for the first motor based on the first rotation speed control torque, and calculates a second final torque command value that is a final torque command value for the second motor by correcting the second basic torque based on a first torque deviation that is a deviation between the first basic torque and the first rotation speed control torque; (b) when the rotation speed of the second motor is higher than the rotation speed of the first motor, calculates the first final torque command value by correcting the first basic torque based on a second torque deviation that is a deviation between the second basic torque and the second rotation speed control torque, and calculates the second final torque command value based on the second rotation speed control torque;
a motor drive control unit that drives the first motor and the second motor based on the first final torque command value and the second final torque command value;
A control device for an electric vehicle comprising: