JP7651960B2 - 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 discloses a vehicle control device that suppresses vehicle body vibrations caused by pitching motion in an electric vehicle. This control device estimates the dynamic fluctuations at a position a predetermined distance away from the center of the pitching motion. Then, in accordance with the estimated fluctuations, a filtering process is performed on the motor output torque, thereby correcting the torque command value so that vehicle body vibrations are suppressed.

JP 2013-240258 A

However, in the above control device, a filtering process is performed on the motor output torque to reduce the gain in a predetermined frequency range. As a result, the actual torque response is different from the torque response based on the original driving force command value. As a result, the method of performing a filtering process on the motor output torque has the problem that, although it is possible to suppress vehicle body vibrations caused by pitching motion (hereinafter referred to as pitching vibrations), it is not possible to obtain the desired acceleration.

The present invention aims to provide a control method and control device for an electric vehicle that can obtain the desired acceleration while suppressing pitching vibration.

One aspect of the present invention is a control method for an electric vehicle having a first motor that drives the front wheels and a second motor that drives the rear wheels. In this control method, a front wheel driving force command value that determines the driving force of the front wheels and a rear wheel driving force command value that determines the driving force of the rear wheels are calculated based on a target driving force for the electric vehicle, and a standard value of the angular velocity or angle of the pitching vibration generated in the electric vehicle is calculated based on the front wheel driving force command value and the rear wheel driving force command value. Meanwhile, a detection value of the angular velocity or angle of the pitching vibration is obtained using a sensor that detects the pitching vibration. Then, based on the difference between the standard value and the detected value of the angular velocity or angle of the pitching vibration, a driving force transfer amount that indicates the magnitude of the driving force to be transferred between the front and rear wheels to suppress the pitching vibration is calculated, and the front wheel driving force command value and the rear wheel driving force command value are corrected based on this driving force transfer amount.

The present invention provides a method and device for controlling an electric vehicle that can obtain a desired acceleration while suppressing pitching vibration.

FIG. 1 is a block diagram showing the configuration of an electric vehicle. FIG. 2 is a flowchart showing a control mode of the electric vehicle. FIG. 3 is a graph showing the relationship between the accelerator opening and the driving force. FIG. 4 is a block diagram of the driving force distribution process. FIG. 5 is an explanatory diagram showing forces acting on an electric vehicle during acceleration. FIG. 6 is a block diagram of the pitch angle control calculation. FIG. 7 is a block diagram of a reference pitch angular velocity model. FIG. 8 is a block diagram showing an inverse model from the driving force movement amount to the pitch angular velocity. FIG. 9 is a block diagram of the driving force movement amount limiting process. FIG. 10 is a graph showing changes in front motor torque, rear motor torque, pitch angle, pitch angular velocity, and longitudinal acceleration. FIG. 11 is a block diagram of a pitch control calculation process according to the second embodiment. FIG. 12 is a block diagram of the FF compensation process. FIG. 13 is a block diagram of the reference pitch angle model. FIG. 14 is a block diagram of the actual pitch angle model. FIG. 15 is a block diagram showing an inverse model from the driving force movement amount to the pitch angle. FIG. 16 is a block diagram showing a reference pitch angular velocity model in the second embodiment.

The following describes an embodiment of the present invention with reference to the drawings.

[First embodiment]
1 is a block diagram showing the configuration of an electric vehicle 1. The electric vehicle 1 is a vehicle that uses the power of an electric motor as a part or all of the driving force, such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. The electric vehicle 1 of this embodiment is a so-called four-wheel drive vehicle.

As shown in FIG. 1, the electric vehicle 1 includes a front drive system 2, a rear drive system 3, a battery 4, and a motor controller 5.

The front drive system 2 is an electrical and mechanical mechanism for driving the front wheels 14 of the electric vehicle 1, and is controlled by a motor controller 5. Specifically, in addition to the front wheels 14, the front drive system 2 includes a front motor 10, which is a first motor, a front inverter 20, and a front reduction gear 30. The front motor 10 generates a drive torque in the front reduction gear 30 in response to the switching operation of the front inverter 20. As a result, the front wheels 14 rotate in response to the drive torque transmitted from the front reduction gear 30, generating a drive force for the electric vehicle 1. Note that the drive torque referred to here includes so-called regenerative torque.

The rear drive system 3 is an electrical and mechanical mechanism for driving the rear wheels 16 of the electric vehicle 1, and is controlled by a motor controller 5. The rear drive system 3 is electrically and mechanically symmetrical to the front drive system 2. Specifically, the rear drive system 3 includes, in addition to the rear wheels 16, a rear motor 12, which is a second motor, a rear inverter 22, and a rear reduction gear 32. The rear motor 12 generates a drive torque in the rear reduction gear 32 in response to the switching operation of the rear inverter 22. As a result, the rear wheels 16 rotate in response to the drive torque transmitted from the rear reduction gear 32, generating a drive force for the electric vehicle 1.

The battery 4 supplies power to the front inverter 20 and the rear inverter 22. The motor controller 5 can arbitrarily acquire the DC voltage _Vdc of the battery 4 as one piece of vehicle information based on a power supply voltage value transmitted from a voltage sensor (not shown) provided on a DC power supply line or a battery controller (not shown).

The motor controller 5 is one or more computers configured to control the front motor 10 and the rear motor 12, and is programmed to function as a calculator or the like that executes various calculations described below. In other words, the motor controller 5 is a control device for the electric vehicle 1. As a result, the motor controller 5 controls the operation of the electric vehicle 1 by operating the front motor 10 or the rear motor 12, or by operating the front motor 10 and the rear motor 12 in cooperation.

The motor controller 5 can arbitrarily acquire various vehicle information indicating the state (vehicle state) of the electric vehicle 1 using sensors (not shown) and the like. For example, the motor controller 5 can appropriately acquire the vehicle speed V and the accelerator opening θ indicating the accelerator operation amount. In addition, the motor controller 5 acquires, for example, the electrical angle of the rotor of the front motor 10 (hereinafter referred to as the front rotor phase) α _f and the current I _f flowing through the front motor 10 as vehicle information indicating the operating state of the front drive system 2 or the front motor 10. Similarly, the motor controller 5 acquires the electrical angle of the rotor of the rear motor 12 (hereinafter referred to as the rear rotor phase) α _r and the current I _r flowing through the rear motor 12 as vehicle information indicating the operating state of the rear drive system 3 or the rear motor 12. In addition, the motor controller 5 can acquire the angular velocity of the pitching vibration (hereinafter referred to as the pitch angular velocity λ') or the angle of the pitching vibration (hereinafter referred to as the pitch angle λ) generated in the electric vehicle 1. In this embodiment, the motor controller 5 acquires the pitch angular velocity λ'. If necessary, the motor controller 5 can obtain other vehicle information by calculation from the directly acquired vehicle information.

The vehicle speed V is obtained from, for example, a meter or a controller (not shown), such as a brake controller. The vehicle speed V may also be calculated using the rotation speed ωm of the front motor 10 (or rear motor 12), the dynamic radius R of the front wheels 14 (or rear wheels 16), and the gear ratio of the final gear. The accelerator opening θ [%] is detected using an accelerator opening sensor (not shown).

The front rotor phase _αf is detected by a rotation sensor 11 attached to the front motor 10. Similarly, the rear rotor phase _αr is detected by a rotation sensor 13 attached to the rear motor 12. In this embodiment, the pitch angular velocity λ' is detected by a pitch rate sensor 17. However, since the pitch angle λ and the pitch angular velocity λ' can be calculated by differentiating or integrating one of them, the pitch angle λ may be detected instead of detecting the pitch angular velocity λ'. In addition, if an acceleration sensor that detects the acceleration in the longitudinal direction of the electric vehicle 1 is provided instead of the pitch rate sensor 17, a controller such as the motor controller 5 can calculate the pitch angle λ and/or the pitch angular velocity λ' based on the output value of the acceleration sensor.

The motor controller 5 generates PWM (Pulse Width Modulation) signals for controlling the front motor 10 and the rear motor 12 based on the input signals representing the various vehicle information described above. The motor controller 5 then generates drive signals for the front inverter 20 and the rear inverter 22 based on the generated PWM signals.

The front inverter 20 and the rear inverter 22 operate according to a drive signal input from the motor controller 5, convert the DC current supplied from the battery 4 into AC current, and output it to the front motor 10 and the rear motor 12. The current I _f output by the front inverter 20 to the front motor 10 is detected by a current sensor 26. The current I _r output by the rear inverter 22 to the rear motor 12 is detected by a current sensor 28. The front motor 10 and the rear motor 12 are, for example, three-phase AC motors, and the current of the remaining phase can be calculated from the current values of two phases. For this reason, the current sensors 26 and 28 may detect the currents of any two phases of the currents I _f and I _r flowing through the front motor 10 and the rear motor 12, and the current of the remaining phase may be calculated by a controller such as the motor controller 5.

<Overall control of electric vehicles>
Fig. 2 is a flowchart showing the control mode of the electric vehicle 1. As shown in Fig. 2, in step S201, the motor controller 5 executes input processing. The input processing is processing for acquiring vehicle information and the like required for calculations of various processes described below.

In step S202, the motor controller 5 executes a basic target driving force calculation process. The basic target driving force calculation process is a process for calculating a target driving force command value F ^* (see FIG. 4) and distributing the target driving force command value F ^* to a first front wheel driving force command value _Ff1 ^* (see FIG. 4) and a first rear wheel driving force command value _Fr1 ^* (see FIG. 4). That is, the motor controller 5 functions as a target driving force calculator and a driving force distributor.

The target driving force command value F ^* is a command value that determines the driving force required of the electric vehicle 1, i.e., the driving force that should be generated in the electric vehicle 1 as a whole (hereinafter referred to as target driving force), and is calculated based on the accelerator opening θ and the vehicle speed V. FIG. 3 is a graph showing the relationship between the accelerator opening θ and the driving force (target driving force). As shown in FIG. 3, the motor controller 5 holds in advance a table (accelerator opening-driving force table) that determines the target driving force according to the accelerator opening θ, and by referring to this, calculates the target driving force command value F ^* according to the accelerator opening θ and the vehicle speed V. The rotation speed on the horizontal axis in the graph of FIG. 3 is calculated based on the vehicle speed V.

The first front-wheel driving force command value _Ff1 ^* is a command value that determines, out of the target driving force, a driving force that should be generated at the front wheels 14 (hereinafter referred to as driving force of the front wheels 14). Similarly, the first rear-wheel driving force command value _Fr1 ^* is a command value that determines, out of the target driving force, a driving force that should be generated at the rear wheels 16 (hereinafter referred to as driving force of the rear wheels 16). The motor controller 5 distributes the target driving force command value F ^* to the first front-wheel driving force command value _Ff1 ^* and the first rear-wheel driving force command value _Fr1 ^* by a driving force distribution process.

FIG. 4 is a block diagram of the driving force distribution process S401. As shown in FIG. 4, the driving force distribution process S401 includes a front wheel driving force calculation process S402 and a rear wheel driving force calculation process S403. The front wheel driving force calculation process S402 is a process for calculating a first front wheel driving force command value F f1 ^* from the target driving force command value F ^* by multiplying the target driving force command value _F ^* by a distribution ratio K _f for the front wheels 14. The rear wheel driving force calculation process S403 is a process for calculating a first rear wheel driving force command value F _r1 ^* by multiplying the target driving force command value F ^* by a distribution ratio "1-K _f " for the rear wheels 16. The distribution ratio K _f for the front wheels 14 is preset to a value between zero and one depending on, for example, the operating state of the electric vehicle 1. The distribution ratio "1-K _f " for the rear wheels 16 is automatically determined by the distribution ratio K _f for the front wheels 14.

When the basic target driving force calculation process is executed in this manner, in step S203 (see FIG. 2), the motor controller 5 executes a pitch angle control calculation process. That is, the motor controller 5 functions as a pitch angle control calculation unit. The pitch angle control calculation process is a process for performing calculations to suppress pitching vibrations occurring in the electric vehicle 1 (or having been caused in the electric vehicle 1). Specifically, in the pitch angle control calculation process, the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* are corrected in accordance with the degree of the pitching vibration to calculate the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* . The pitch angle control calculation process will be described in detail later.

In step S204, the motor controller 5 executes a vibration suppression control calculation process. The vibration suppression control calculation process is a process for performing calculations to suppress vibrations, such as so-called torsional vibrations, that occur in the driving force transmission system. In the vibration suppression control calculation process, the motor controller 5 converts the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* into values equivalent to the motor torque based on the gear ratios and tire diameters of the front and rear wheels 14 and 16, thereby calculating a motor torque command value T _f ^* for the front wheels 14 and a motor torque command value T _r ^* for the rear wheels 16. In addition, the motor controller 5 calculates a rotational angular velocity ω _f (not shown) of the front motor 10 based on the front rotor phase α _f and the like. Similarly, the motor controller 5 calculates a rotational angular velocity ω _r (not shown) of the rear motor 12 based on the rear rotor phase α _r and the like. Then, the motor controller 5 calculates final motor torque command values (hereinafter referred to as post-vibration suppression control motor torque command values) for the front motor 10 and the rear motor 12 based on the motor torque command values _Tf ^* , _Tr ^* for the front wheels 14 and the rear wheels 16 and the rotational angular velocities _ωf , _ωr for the front motor 10 and the rear motor 12. The front motor 10 and the rear motor 12 are driven based on the post-vibration suppression control motor torque command values, thereby suppressing vibrations generated in the driving force transmission system, such as torsional vibrations of the drive shaft, without sacrificing the response of the drive shaft torque. Note that if the electric vehicle 1 does not have a drive shaft or if torsional vibrations and the like are suppressed by a mechanical mechanism, the vibration suppression control calculation process in step S204 may be omitted.

In step S205, the motor controller 5 executes a current command value calculation process. The current command value calculation process is a process for calculating a d-axis current target value i _d ^* and a q-axis current target value i _q ^* (hereinafter referred to as dq-axis current target values i _d ^* , i _q ^* ) for the front motor 10 and the rear motor 12, respectively. Specifically, the motor controller 5 calculates the dq-axis current target values i _{d *, i q * for the front motor 10 and the rear motor 12, respectively, based on the motor torque command value after vibration suppression control, the rotational angular velocities ω f} ^{, ω} _{r , and} the DC voltage V _dc of the battery 4. The motor controller 5 previously holds a table that associates the motor torque command value after vibration suppression control, the rotational angular velocities ω _f , ω _r , and the DC voltage V _dc of the battery 4 with the dq-axis current target values i _d ^* , i _q ^* . Therefore, the motor controller 5 calculates the d-axis and q-axis current target values i _d ^* , i _q ^* of the front motor 10 and the rear motor 12 by referring to this table.

In step S206, the motor controller 5 executes a current control calculation process. The current control calculation process is a process for calculating PWM signals for controlling the opening and closing of the switching elements of the front inverter 20 and the rear inverter 22, based on the dq-axis current target values i _d ^* , i _q ^* .

Specifically, the motor controller 5 calculates the d-axis current i _d and the q-axis current i _q (hereinafter referred to as dq-axis current i _d , i _q ) of the front motor 10 and the rear motor 12, respectively, using the currents I _f , I _r , the front rotor phase α _f , and the rear rotor phase α _r . Next, the motor controller 5 calculates the d-axis voltage command value v _d and the _q -axis voltage command value v _q (hereinafter referred to as dq-axis voltage command values v _d , v _q ⁾ of the front motor 10 and the rear motor 12, respectively, based on the deviation between the dq-axis currents i ^d , i _q and the dq-axis current target values i _{d *} , i _q * . Thereafter, the motor controller 5 calculates the three-phase voltage command values of the front motor 10 and the rear motor 12, respectively, based on the dq-axis voltage command values v _d , v _q , the front rotor phase α _f , and the rear rotor phase α _r . Then, the motor controller 5 calculates the PWM signals to be input to the front inverter 20 and the rear inverter 22 based on the three-phase voltage command values and the DC voltage _Vdc of the battery 4. The front inverter 20 and the rear inverter 22 open and close their built-in switching elements in accordance with the PWM signals calculated in this manner. As a result, the front motor 10 and the rear motor 12 are each driven with the desired torque determined by the motor torque command value after vibration suppression control.

The pitch angle control calculation process is explained in detail below.

<Transfer characteristics used in pitch angle control calculation process>
5 is an explanatory diagram showing forces acting on the electric vehicle 1 during acceleration. Here, the sprung mass (the portion above the suspension) of the body of the electric vehicle 1 (hereinafter simply referred to as the body) is assumed to be a rigid body. In this case, the sprung mass of the body of the electric vehicle 1 is acted upon by a reaction force of the driving force of the electric vehicle 1 (hereinafter referred to as the driving force reaction force), an inertial force, and vertical forces according to the instantaneous rotation angles θ _f and θ _r determined by the operating state of the suspension. The vertical forces according to the instantaneous rotation angles θ _f and θ _r are so-called anti-dive forces and anti-squat forces, or pitching moment M _y caused by these forces.

The parameters used in the equations of motion and the like described below are as follows:
Center of gravity height [m] H _g
Front and rear wheel radius [m] R _a
Distance from the center of the front wheel to the center of gravity [m] L _f
Distance from the center of the rear wheel to the center of gravity [m] L _r
Spring constant of front wheel suspension [N/m] K _f
Rear wheel suspension spring coefficient [N/m] _Kr
Front wheel damping coefficient [N/(m/s)] C _f
Rear wheel damping coefficient [N/(m/s)] C _r
Pitching moment of inertia around the center of gravity [kg/m ² ] I _y
Pitch angle [rad] λ
Pitch angular velocity [rad/s] λ'
Instantaneous rotation angle of front wheels [rad] θ _f
Instantaneous rotation angle of rear wheels [rad] θ _r
Front wheel driving force [N] F _f
Rear wheel drive force [N] F _r

The pitching moment M _y is expressed by the following formula (1) using the above parameters. Note that the instantaneous rotation angles θ _f and θ _r are treated as known fixed values here because changes during the stroke are minute. In other words, the instantaneous rotation angles θ _f and θ _r are determined in advance by simulation, experiment, or the like based on the specific configuration of the electric vehicle 1.

Therefore, the equation of motion around the center of pitching rotation is expressed by the following equation (2). Furthermore, the coefficients Cλ and Kλ in equation (2) are expressed by the following equation (3).

Then, the above formula (2) is Laplace transformed, and the driving force _Ff of the front wheels 14 is set to be equal to the first front wheel driving force command value _Ff1 ^* , and the driving force _Fr of the rear wheels 16 is set to be equal to the first rear wheel driving force command value _Fr1 ^* . As a result, as shown in the following formula (4), the transfer characteristic _Gp λ(s) from the input of the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* to the output of the pitch angle λ is obtained. As shown in formula (4), the transfer characteristic _Gp λ(s) is a second-order system response.

Similarly, the transfer characteristic G _p λ'(s) from the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* to the pitch angular velocity _λ' is expressed by the following equation (5).

The transfer characteristic G _r λ'(s) of the standard response from the first front-wheel driving force command value F _f1 ^* and the first rear-wheel driving force command value F _r1 ^* to the pitch angular velocity λ' is a transfer characteristic in an ideal state in which pitching vibration is minimized. Therefore, the transfer characteristic G _r λ'(s) of the standard response is obtained by setting the damping coefficient ζ _λ to 1 in the above transfer characteristic G _p λ'(s), and is expressed by the following equation (6).

The reference value of the pitch angular velocity λ' (hereinafter referred to as the reference pitch angular velocity) _λr ' is found by using the above formula (6) instead of the transfer characteristic _Gpλ '(s) in the first formula of formula (5). That is, the reference pitch angular velocity _λr ' is expressed by the following formula (7). The reference value of the pitch angular velocity λ' (reference pitch angular velocity _λr ') refers to the value of the pitch angular velocity λ' generated due to a pitching disturbance d or the like in an ideal state in which pitching vibration is minimized.

In the pitch angle control calculation process of this embodiment, as described below, the target driving force command value F ^* , i.e., the sum of the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* , is kept constant. Therefore, as shown in the following equation (8), the driving force transfer amount _Fd is added to or subtracted from the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* to calculate the second front wheel driving force command value _Ff2 ^* and the second rear wheel driving force command value _Fr2 ^* . The driving force transfer amount _Fd ^* represents the magnitude of the driving force that should be transferred between the front wheels 14 and the rear wheels 16 to suppress pitching vibration.

The sign of the driving force transfer amount _Fd is positive in the direction in which the driving force is transferred from the rear wheels 16 to the front wheels 14. In other words, when the driving force is transferred from the rear wheels 16 to the front wheels 14, the driving force transfer amount _Fd is positive, and conversely, when the driving force is transferred from the front wheels 14 to the rear wheels 16, the driving force transfer amount _Fd is negative.

In the following, assuming that the driving force transfer amount _Fd is added to the first front wheel driving force command value _Ff1 ^* and that the driving force transfer amount _Fd is subtracted from the first rear wheel driving force command value _Fr1 ^* , the dynamic characteristics of the pitch angle λ are derived to be an arbitrary standard response.

The response of the pitch angular velocity λ' when the driving force transfer amount _Fd is applied is expressed by the following equation (9) using the transfer characteristic _Gpλ '(s). Therefore, the inverse model of the transfer characteristic from the driving force transfer amount _Fd to the pitch angular velocity λ' is expressed by the following equation (10).

In addition, a disturbance (hereinafter referred to as a pitching disturbance) that generates a pitching vibration relative to the standard pitch angular velocity _λr ' is denoted as "d." In this case, a transfer characteristic _Grd ( _s ) relating to a standard response from the pitching disturbance d to the standard pitch angular velocity λr' (hereinafter referred to as a standard disturbance response) is expressed by the following equation (11).

Moreover, using equation (9) and a disturbance response filter H _d (s) that determines the response characteristics to the pitching disturbance d, the calculation equation for the driving force transfer amount F _d and the pitching disturbance d are defined as in the following equation (12). In this case, the transfer characteristic from the pitching disturbance d to the pitch angular velocity λ' is expressed by the following equation (13).

Using these, the response from the pitching disturbance d is solved to obtain a transfer characteristic G _rd (s) having a similar gain to the transfer characteristic G _p λ'(s) and no overshoot as shown in equation (10), and the disturbance response filter H _d (s) is expressed by the following equation (14). As shown in equation (14), the disturbance response filter H _d (s) is a bandpass filter at the natural frequency of the transfer characteristic G _p λ'(s). Therefore, the steady-state characteristics of the disturbance response filter H _d (s), i.e., the characteristics in frequency bands other than those near the natural frequency of the transfer characteristic G _p λ'(s), are zero.

<Pitch angle control calculation process>
Fig. 6 is a block diagram of the pitch angle control calculation process executed in step S203. As shown in Fig. 6, the pitch angle control calculation process includes a reference pitch angular velocity calculation process S601, a difference calculation process S602, a driving force movement amount calculation process S603, a driving force movement amount limiting process S604, a driving force command value correction process S605, and a phase adjustment process S606. The pitch angle control calculation process is a feedback compensation process (hereinafter referred to as FB compensation process) that compensates for fluctuations in the pitch angle λ by feeding back the detection value of the pitch angular velocity λ'.

The reference pitch angular velocity calculation process S601 is a process for calculating a reference pitch angular velocity _λr ' based on the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* in accordance with a reference pitch angular velocity model. The specific contents of the reference pitch angular velocity model will be described in detail later.

The difference calculation process S602 (see FIG. 6) is a process for obtaining the detected value of the pitch angular velocity λ' from the pitch rate sensor 17 and calculating the difference (λ _r '-λ') between this and the reference pitch angular velocity λ _{r '} .

The driving force transfer amount calculation process S603 is a process for calculating the driving force transfer amount _Fd from the difference _λr' -λ' between the reference pitch angular velocity _λr ' and the detected value of the pitch angular velocity λ' using an inverse model of the pitch angular velocity λ' from the driving force transfer amount _Fd . The inverse model of the pitch angular velocity λ' from the driving force transfer amount _Fd will be described in detail later.

The driving force transfer amount limiting process S604 is a process that applies a limit to the driving force transfer amount _Fd calculated in the driving force transfer amount calculation process S603 based on the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* , and calculates the driving force transfer amount _FdL after limiting.

For example, when the driving force transfer amount F _d is a positive value, that is, when the driving force is transferred from the rear wheels 16 to the front wheels 14 to reduce pitching vibration, it is desirable to make the driving force transfer amount F _d smaller than the driving force of the rear wheels 16. This is because, if the driving force transfer amount F _d is a value equal to or greater than the driving force of the rear wheels 16, a positive driving force is generated in the front wheels 14 and the wheels are powered, but a negative driving force is generated in the rear wheels 16 and the wheels are regeneratively driven. In this way, when driving forces in opposite directions are generated in the front wheels 14 and the rear wheels 16, a rocking motion occurs or the load on the vehicle body increases, so that the desired driving may not be achieved. Therefore, in the driving force transfer amount limiting process S604, the driving force transfer amount F _d from the rear wheels 16 to the front wheels 14 is limited within the range of the driving force of the rear wheels 16. The same applies when the driving force is transferred from the front wheels 14 to the rear wheels 16, that is, when the driving force transfer amount F _d is a negative value. The specific processing content of the driving force movement amount limiting process S604 will be described in detail later.

The driving force command value correction process S605 is a process for calculating a second front wheel driving force command value F _f2 ^* and a second rear wheel driving force command value F _r2 ^* by correcting the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* based on the post-limiting driving force transfer amount F _dL . Specifically, the second front wheel driving force command value F _f2 ^* is calculated by adding the post-limiting driving force transfer amount F _dL to the first front wheel driving force command value F _f1 ^* . Meanwhile, the second rear wheel driving force command value F _r2 ^* is calculated by subtracting the post-limiting driving force transfer amount F _dL from the first rear wheel driving force command value F _r1 ^* .

The phase adjustment process S606 is a process in which the second front wheel driving force command value _Ff2 ^* and/or the second rear wheel driving force command value _Fr2 ^* are filtered using a filter (hereinafter referred to as a phase adjustment filter) configured with a transfer characteristic _Gr (s) and a transfer characteristic _Grr (s). This phase adjustment filter adjusts the second front wheel driving force command value _Ff2 ^* and/or the second rear wheel driving force command value Fr2* so that there is no difference between the dynamic characteristics and phase from the second front wheel driving force command value _Ff2 ^* to the front wheels 14 and the dynamic _{characteristics} and phase ^{from the second rear wheel driving force command value Fr2*} _to ^the rear wheels 16. The transfer characteristic _Gr (s) is a transfer characteristic from the motor torque command value for the front motor 10 (motor torque command value after vibration suppression control) to the rotation speed of the front motor 10, and represents a response delay of the front motor 10. The transfer characteristic G _rr (s) is the transfer characteristic from the motor torque command value for the rear motor 12 (motor torque command value after vibration damping control) to the rotation speed of the rear motor 12, and represents the response delay of the rear motor 12. In this embodiment, the second front wheel driving force command value F _f2 ^* is filtered by a phase adjustment filter expressed as G _rr (s)/G _r (s), and the second rear wheel driving force command value F _r2 ^* is output as is.

<Reference pitch angular velocity model>
Fig. 7 is a block diagram of the reference pitch angular velocity model. As shown in Fig. 7, the reference pitch angular velocity model used in the reference pitch angular velocity calculation process S601 is based on Equation (7). However, in this embodiment, the reference pitch angular velocity model further includes a dead time filtering process and a filtering process using the transfer characteristic G _r (s) and the transfer characteristic G _rr (s).

Specifically, the first front-wheel driving force command value F _f1 ^* is filtered by an all-pass filter e ^-s τ having a dead time τ from the second front-wheel driving force command value F _f2 ^* to the driving force of the front wheels 14. Next, it is filtered by the transfer characteristic G _r (s) to take into account the response delay of the front motor 10. As a result, the phase of the reference pitch angular velocity λ _r ' and the phase of the detected value of the pitch angular velocity λ ' match particularly accurately. Note that the dead time τ from the second front-wheel driving force command value F _f2 ^* to the driving force of the front wheels 14 is the calculation time, communication time, etc. of an ECU (Electronic Control Unit) functioning as the motor controller 5, etc.

Similarly, the first rear wheel driving force command value F _r1 ^* is filtered by an all-pass filter e ^-s τ having a dead time τ from the second rear wheel driving force command value F _r2 ^* to the driving force of the rear wheels 16. Next, it is filtered by the transfer characteristic G _rr (s) to take into account the response delay of the rear motor 12. This makes the phase of the reference pitch angular velocity λ _r ' and the phase of the detected value of the pitch angular velocity λ' match particularly accurately.

The first front wheel driving force command value _Ff1 ^* and first rear wheel driving force command value _Fr1 ^* that have been subjected to the above filtering process are multiplied by coefficients _Mf , _Mr (see equation (4)) based on the instantaneous rotation angles _θf , _θr, respectively, in accordance with equation (7), and then added together. Thereafter, a reference pitch angular velocity λr' is calculated from the sum of these values using a transfer characteristic _Grλ '(s) relating to a reference response from the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* to the pitch angular velocity λ _' .

<Inverse model of pitch angular velocity from driving force movement amount>
Fig. 8 is a block diagram showing an inverse model from the driving force transfer amount _Fd to the pitch angular velocity λ'. As shown in Fig. 8, the "inverse model from the driving force transfer amount _Fd to the pitch angular velocity λ'" used in the driving force transfer amount calculation process S603 is based on the formula (12). That is, in the driving force transfer amount calculation process S603, a filtering process is performed on the difference _λr' -λ' between the reference value of the pitch angular velocity λ' (reference pitch angular velocity _λr ') and the detected value by the inverse model 1/ _Gpλ '(s) of the transfer characteristic _Gpλ '(s) and the disturbance response filter _Hd (s). After that, the driving force transfer amount _Fd is calculated by multiplying it by a predetermined coefficient 1/( _Mf - _Mr ) determined by the coefficients _Mf and _Mr based on the instantaneous rotation angles _θf and _θr .

In this way, the driving force transfer amount F _d is calculated such that the pitch angular velocity λ' coincides with or approaches the reference pitch angular velocity λ _r ' and the pitching vibration is suppressed.

<Driving force movement amount limiting process>
9 is a block diagram of the driving force transfer amount limiting process S604. As shown in FIG. 9, in the driving force transfer amount limiting process S604, the first rear wheel driving force command value F _r1 ^* and the driving force transfer amount F _d are compared. Then, the smaller of these values is compared with the sign-inverted value of the first front wheel driving force command value F _f1 ^* , and the larger of these values is output as the post-limiting driving force transfer amount F _dL . As a result, the driving force transfer amount F _d is limited to a range that does not exceed the driving force of the wheel whose driving force is reduced, either the front wheels 14 or the rear wheels 16. As a result, in the driving force transfer amount limiting process S604, the post-limiting driving force transfer amount F _dL limited so as to keep the signs of the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _{r1 *} ^the same is output.

For example, suppose that the driving force transfer amount _Fd is a positive value and the driving force is transferred from the rear wheels 16 to the front wheels 14. At this time, if the driving force transfer amount _Fd is smaller than the first rear wheel driving force command value _Fr1 ^* , the driving force transfer amount _Fd is output as it is as the post-restriction driving force transfer amount _FdL . That is, if the driving force transfer amount _Fd is within a range smaller than the first rear wheel driving force command value _Fr1 ^* , there is no substantial restriction on the driving force transfer amount _Fd . On the other hand, if the driving force transfer amount _Fd is larger than the first rear wheel driving force command value _Fr1 ^* of the rear wheels 16, the first rear wheel driving force command value _Fr1 ^* is output as the post-restriction driving force transfer amount _FdL . That is, the driving force transfer amount _Fd is limited so that the first rear wheel driving force command value _Fr1 ^* is the upper limit.

The same is true when the driving force transfer amount _Fd is a negative value and the driving force is transferred from the front wheels 14 to the rear wheels 16. That is, when the driving force transfer amount _Fd is smaller than the first front wheel driving force command value _Ff1 ^* , the driving force transfer amount _Fd becomes the limited driving force transfer amount _FdL as it is. On the other hand, when the driving force transfer amount _Fd is larger than the first front wheel driving force command value _Ff1 ^* , the driving force transfer amount _Fd is limited so that the first front wheel driving force command value _Ff1 ^* becomes the upper limit.

<Action>
The operation of the control method for the electric vehicle 1 according to this embodiment will be described below. FIG. 10 is a graph showing the transitions of (A) front motor torque, (B) rear motor torque, (C) pitch angle, (D) pitch angular velocity, and (E) longitudinal acceleration. In FIG. 10, the solid line represents the case where the control method according to this embodiment is implemented. Meanwhile, the dashed line represents the transitions of a comparative example in which pitching vibration is suppressed by applying filtering processing to the output torque of the motor. FIG. 10 also represents a scene in which the accelerator is suddenly depressed at time t1 from a stopped state of the electric vehicle 1, the target driving force command value F ^* increases in a step, and then a pitching disturbance d occurs at time t2.

As shown in FIG. 10(C), even when the electric vehicle 1 suddenly starts at time t1, no overshoot occurs in the pitch angle λ. This is almost the same in the comparative example. In other words, the control of both this embodiment and the comparative example can suppress pitching vibrations during sudden starts.

However, as shown in FIG. 10(E), the control of this embodiment provides a steep longitudinal acceleration in response to accelerator depression, whereas the control of the comparative example does not provide a sufficient increase in longitudinal acceleration.

That is, in the control of the comparative example, the pitching vibration is suppressed by filtering the output torque of the motor, so that a part of the target driving force command value F ^* is necessarily reduced. Therefore, in the control of the comparative example, although the pitching vibration is suppressed, the desired acceleration corresponding to the accelerator operation cannot be obtained.

In contrast, in the control of this embodiment, the distribution of the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* is adjusted by feedback control using the detected value of the pitch angular velocity λ', thereby suppressing pitching vibration without changing the target driving force command value F ^* . Therefore, according to the control of this embodiment, pitching vibration is suppressed, and desired acceleration/deceleration corresponding to accelerator operation is obtained.

When a pitching disturbance d occurs at time t2, as shown in FIG. 10(C), the pitch angle λ overshoots significantly in the control of the comparative example. In contrast, the control of this embodiment causes a smaller overshoot of the pitching disturbance d than in the comparative example. In other words, the control of this embodiment can reduce pitching vibrations (e.g., backswing) caused by disturbances more than the control of the comparative example.

In the first embodiment, the pitch angular velocity λ' is detected by the pitch rate sensor 17, and the driving force transfer amount _Fd is calculated based on the difference between the reference value of the pitch angular velocity λ' (reference pitch angular velocity _λr ') and the detected value, but this is not limited to the above. For example, the pitch angle λ may be detected directly, or the pitch angle λ may be calculated using the pitch angular velocity λ' to indirectly detect the pitch angle λ. In this case, the motor controller 5 can calculate the driving force transfer amount Fd by using the reference value and the detected value of the pitch angle λ in the same manner as in the first embodiment using the pitch angular velocity _λ '. Specifically, the motor controller 5 can calculate the driving force transfer amount _Fd based on the difference _λr -λ between the reference value of the pitch angle λ (reference pitch angle _λr ) and the detected value of the pitch angle λ.

As described above, the control method according to the first embodiment is a control method for an electric vehicle 1 having the front motor 10, which is a first motor that drives the front wheels 14, and the rear motor 12, which is a second motor that drives the rear wheels 16. In this control method, a front wheel driving force command value (first front wheel driving force command value F f1 ^*) that determines the driving force of the front wheels 14 and a rear wheel driving force command value (first rear wheel driving force command value F _r1 ^* ) that determines the driving force of the rear wheels 16 are calculated based on a target driving force command value _F ^* that determines a target driving force for the electric vehicle 1. In addition, a reference value (reference pitch angular velocity λ r ' or reference pitch angle λ r ) of the angular velocity (pitch angular velocity λ') or angle (pitch angle _λ ) of the pitching vibration generated in the electric vehicle 1 is calculated based on the front wheel driving force command value and the rear wheel driving force command value. Meanwhile, a detection value of the pitch angular velocity λ' _or pitch angle λ is obtained using a sensor that detects the pitching vibration. Then, based on the difference between the reference value and the detected value of the pitch angular velocity λ' or the pitch angle λ, a driving force transfer amount _Fd indicating the magnitude of the driving force that should be transferred between the front wheels 14 and the rear wheels 16 in order to suppress the pitching vibration is calculated, and the front wheel driving force command value and the rear wheel driving force command value are corrected based on this driving force transfer amount _Fd .

In this way, in the control method according to the first embodiment, the driving force transfer amount _Fd for suppressing the pitching vibration is calculated using the pitch angular velocity λ' or the pitch angle λ, and the front wheel driving force command value and the rear wheel driving force command value are corrected based on this driving force transfer amount Fd. Therefore, according to the control method according to the first embodiment, the sum of the driving forces generated at the front wheels 14 and the rear wheels 16, i.e., the driving force generated in the electric vehicle 1 as a whole, is maintained. As a result, the pitching vibration of the electric vehicle 1 is suppressed, and at the same time, a desired acceleration/deceleration determined according to the accelerator opening θ and the like is obtained. That is, according to the control method according to the first embodiment, both the acceleration/deceleration required according to the driving operation of the driver and the control of the pitch angle λ for reducing the pitching vibration are achieved. Furthermore, when a pitching disturbance d that generates a pitching vibration is applied to the electric vehicle 1 from the road surface or the like, the change in the pitch angle λ is reduced.

Moreover, in the control method according to the first embodiment, the reference value of the pitch angular velocity λ' or the pitch angle λ is calculated based on the up and down forces represented by the instantaneous rotation angles θ _f and θ _r of the front wheels 14 and the rear wheels 16, which are determined in advance by the driving force generated at the front wheels 14 and the rear wheels 16, the inertial force, and the operating state of the suspension. That is, the reference value of the pitch angular velocity λ' or the pitch angle λ is calculated based on physical parameters that are determined in advance for the electric vehicle 1. Therefore, the reference value of the pitch angular velocity λ' or the pitch angle λ becomes a value that represents a practical and accurate reference response according to the specific configuration of the electric vehicle 1. As a result, the control method according to the first embodiment allows pitching vibration to be suppressed particularly accurately.

In the control method according to the first embodiment, the reference value of the pitch angular velocity λ' or the pitch angle λ is calculated based on the dead time τ from the front wheel driving force command value (second front wheel driving force command value F _f2 ^* ) and the rear wheel driving force command value (second rear wheel driving force command value F _r2 ^* ) to the driving forces generated at the front wheels 14 and the rear wheels 16, and the response delay of the front motor 10 and the rear motor 12. That is, the reference value of the pitch angular velocity λ' or the pitch angle λ is calculated by filtering the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* with the all-pass filter ^{e -s} τ and the transfer characteristics G _r (s), G _rr (s). This makes the phase of the reference pitch angular velocity λ _r ' or the reference pitch angle λ _r and the phase of the detected value of the pitch angular velocity λ' or the pitch angle λ match particularly accurately. As a result, the generation of an excess driving force transfer amount F _d is suppressed, and pitching vibration is particularly accurately suppressed.

In the control method according to the first embodiment, the driving force transfer amount _Fd is calculated using a disturbance response filter _Hd (s) whose steady-state characteristic is zero. As a result, the control method according to the first embodiment is a control system that acts only on the transient response with respect to the control of the pitch angle λ. Therefore, within the range of the steady-state response, the driving force transfer amount _Fd becomes zero, and the output as determined by the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* is realized. In other words, except when it is required transiently or temporarily, the driving force is not transferred wastefully between the front wheels 14 and the rear wheels 16. As a result, the burden on the vehicle body is reduced.

In the control method according to the first embodiment, the disturbance response filter H _d (s) is specifically a band-pass filter that passes the resonance frequency of the pitch angular velocity λ' or the pitch angle λ. Therefore, a driving force transfer amount F _d that reduces the gain of the resonance frequency of the pitching vibration caused by the pitching disturbance d is calculated. As a result, the pitching vibration caused by the pitching disturbance d is particularly effectively reduced.

In the control method according to the first embodiment, the driving force transfer amount _Fd is limited by the driving force transfer amount limiting process S604 to a value that can be taken within a range in which the signs of the front wheel driving force command value (first front wheel driving force command value _Ff1 ^* ) and the rear wheel driving force command value (first rear wheel driving force command value _Fr1 ^* ) are the same. This prevents a situation in which the front wheels 14 are powered and the rear wheels 16 are regeneratively driven, even if the driving force is transferred to suppress pitching vibration. As a result, the burden on the vehicle body is reduced. Also, a backlash (deterioration of fuel efficiency) on fuel efficiency performance can be prevented.

In the control method according to the first embodiment, in the phase adjustment process S606, the dynamic characteristics and phase of the front wheel driving force command value (second front wheel driving force command value F _{f2 *} ⁾ and/or the rear wheel driving force command value (second rear wheel driving force command value F _r2 ^* ) corrected based on the driving force transfer amount F d are adjusted. When the dynamic characteristics and phases from the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* to the driving forces of the front wheels 14 and the rear wheels 16 are different, the pitch angle response according to the standard response may not be realized. However, when the dynamic characteristics and phases from the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* to the driving forces of the front wheels 14 and the rear wheels 16 are adjusted, the pitch angle response according to the standard response is easily realized.

[Second embodiment]
In the first embodiment, the pitch angle control calculation process executed in step S203 is configured by FB compensation processing that feeds back the detected value of the pitch angular velocity λ', but is not limited to this. The pitch angle control calculation process can be configured by compensation processing by feedforward control (hereinafter referred to as FF compensation processing) that estimates the pitch angular velocity λ' and uses the estimated value. Also, the pitch angle control calculation process may be configured by a combination of FF compensation processing and FB compensation processing. In the second embodiment, an example will be described below in which the pitch angle control calculation process is configured by a combination of FF compensation processing and the FB compensation processing of the first embodiment.

Fig. 11 is a block diagram of the pitch angle control calculation process according to the second embodiment. As shown in Fig. 11, the pitch angle control calculation process in step S203 receives the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* as inputs, and outputs the second front wheel driving force command value _Ff2 ^* and the second rear wheel driving force command value _Fr2 ^* obtained by correcting these values through the pitch angle control calculation process, as in the first embodiment. However, in the second embodiment, the pitch angle control calculation process includes an FF compensation process S1101 and an FB compensation process S1102.

The FF compensation process S1101 is a process for suppressing pitching vibrations occurring in the electric vehicle 1 (or caused in the electric vehicle 1) by compensating for fluctuations in the pitch angle λ by feedforward control. In the FF compensation process S1101, the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* are corrected according to the degree of pitching vibration. The first front wheel driving force command value F _f1 ^* corrected in the FF compensation process S1101 (hereinafter referred to as the FF compensated front wheel driving force command value F _λf ^* ) and the first rear wheel driving force command value F _r1 ^* corrected in the FF compensation process S1101 (hereinafter referred to as the FF compensated rear wheel driving force command value F _λr ^* ) are output. The FF compensated front wheel driving force command value F _λf ^* and the FF compensated rear wheel driving force command value F _λr ^* are input to the FB compensation process S1102.

In the pitch angle control calculation process of the first embodiment, the reference value and the detected value of the pitch angular velocity λ' are used, but as described in detail below, in the FF compensation process S1101 of the second embodiment, the reference value and the estimated value of the pitch angle λ are used instead of the pitch angular velocity λ'. However, in the FF compensation process S1101 of this embodiment, the reference value and the estimated value of the pitch angular velocity λ' may be used instead of the reference value and the estimated value of the pitch angle λ.

Figure 12 is a block diagram of the FF compensation process S1101. As shown in Figure 12, it includes a reference pitch angle response calculation process S1201, a pitch angle estimation process S1202, a difference calculation process S1203, a driving force movement amount calculation process S1204, a driving force movement amount restriction process S1205, a driving force command value correction process S1206, and a phase adjustment process S1207.

The reference pitch angle response calculation process S1201 is a process for calculating a reference pitch angle λ _r based on the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* in accordance with a reference pitch angle model.

13 is a block diagram of the reference pitch angle model (reference pitch angle response calculation process S1201). As shown in FIG. 13, the reference pitch angle model is based on the following formula (15). This reference pitch angle model is derived in the same manner as the reference pitch angular velocity model (see formula (7)). The transfer characteristic G _r λ(s) used in the reference pitch angle model is a transfer characteristic related to a reference response from the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* to the pitch angle λ, and is the transfer characteristic G _p λ(s) in formula (4) with the damping coefficient ζ _λ set to 1.

The pitch angle estimation process S1202 is a process for calculating a pitch angle estimated value λ^, which is an estimate of the pitch angle λ, based on the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* in accordance with the actual pitch angle model.

Figure 14 is a block diagram of the actual pitch angle model (pitch angle estimation process S1202). As shown in Figure 14, the actual pitch angle model is based on the following equation (16). This actual pitch angle model is obtained by replacing the pitch angle λ in equation (4) with the pitch angle estimated value λ^.

The difference calculation process S1203 is a process for calculating the difference (λ _r - λ ^) between the reference pitch angle λ _r and the pitch angle estimated value λ ^.

The driving force transfer amount calculation process S1204 is a process for calculating the driving force transfer amount _TdFF from the difference _λr -λ^ between the reference pitch angle _λr and the estimated pitch angle λ^ using an inverse model of the pitch angle λ from the driving force transfer amount _TdFF . The driving force transfer amount _TdFF calculated in the driving force transfer amount calculation process S1204 is similar to the driving force transfer amount _Fd in the first embodiment and the driving force transfer amount _FdFB (not shown) calculated in the FB compensation process S1102, but is suffixed with FF for distinction.

Fig. 15 is a block diagram showing an inverse model from the driving force transfer amount _FdFF to the pitch angle λ (driving force transfer amount calculation process S1204). As shown in Fig. 15, the inverse model from the driving force transfer amount _FdFF to the pitch angle λ is based on the following formula (17). That is, the inverse model from the driving force transfer amount _FdFF to the pitch angle λ is obtained by replacing the disturbance response filter _Hd (s) with "1", the reference pitch angular velocity _λr ' with the reference pitch angle _λr , and the pitch angular velocity λ' with the pitch angle λ in formula (12). The disturbance response filter _Hd (s) is replaced with "1" because in this embodiment, the response of the pitching disturbance d is taken into account in the FB compensation process S1102, and therefore it is not necessary to take the pitching disturbance d into account at the stage of the FF compensation process S1101.

The driving force transfer amount limiting process S1205 is a process for calculating a limited driving force transfer amount _FdFFL by applying a limit based on the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* to the driving force transfer amount FdFF calculated in the driving force transfer amount calculation process _S1204 . The purpose of limiting the driving force transfer amount _FdFF in the driving force transfer amount limiting process S1205 and the specific method of calculating the limited driving force transfer amount _FdFFL are similar to those in the driving force transfer amount limiting process S604 in the first embodiment.

The driving force command value correction process S1206 is a process for calculating the FF compensated front wheel driving force command value _Fλf ^* and _the FF compensated rear wheel driving force command value _Fλr ^* by correcting the first front wheel driving force command value _Ff1 ^* and the first rear wheel driving force command value _Fr1 ^* based on the post-limiting driving force transfer amount _FdFFL . Specifically, the FF compensated front wheel driving force command value _Fλf ^* is calculated by adding the post-limiting driving force transfer amount FdFFL to the first front wheel driving force command value _Ff1 ^* . On the other hand, the FF compensated rear wheel driving force command value _Fλr ^* is calculated by subtracting the post-limiting driving force transfer amount _FdFFL from the first rear wheel driving force command value _Fr1 ^* .

The phase adjustment process S1207 is a process in which a filtering process is performed on the FF compensated front wheel driving force command value F _λf ^* and/or the FF compensated rear wheel driving force command value F _λr ^* using a phase adjustment filter configured with the transfer characteristic G _r (s) and the transfer characteristic G _rr (s). That is, the purpose and specific processing content of the phase adjustment process S1207 are similar to those of the phase adjustment process S606 in the first embodiment. The FF compensated front wheel driving force command value F _λf ^* and the FF compensated rear wheel driving force command value F _λr ^* whose phases have been adjusted are used in the FB compensation process S1102.

In the FB compensation process S1102, the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* are calculated by correcting the FF compensated front wheel driving force command value F _λf ^* and the FF compensated rear wheel driving force command value F _λr ^* according to the degree of pitching vibration.

The specific processing contents of the FB compensation process S1102 are basically the same as the pitch angle control calculation process (step S203) of the first embodiment. However, in the FB compensation process S1102, the FF compensated front wheel driving force command value F _λf ^* and the FF compensated rear wheel driving force command value F _λr ^* are used as inputs instead of the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* . Also, in the FB compensation process S1102, the reference pitch angular velocity λ _r ' is calculated using the transfer characteristic G _p λ'(s).

Fig. 16 is a block diagram showing a reference pitch angular velocity model (reference pitch angular velocity calculation process S601) in the second embodiment. As shown in Fig. 16, in the reference pitch angular velocity model used in the FB compensation process S1102, the FF compensated front wheel driving force command value F _λf ^* is filtered by the all-pass filter e ^-s τ and the transfer characteristic G _r (s). Similarly, the FF compensated rear wheel driving force command value F _λr ^* is filtered by the all-pass filter e ^-s τ and the transfer characteristic G _rr (s). These are the same as the pitch angle control calculation process in the first embodiment.

On the other hand, the reference pitch angular velocity model used in the FB compensation process S1102 is based on the following equation (18) except for the above filtering process. That is, the transfer characteristic G _p λ'(s) is used instead of the transfer characteristic G _r λ'(s). This is because, in this embodiment, the FF compensation process S1101 is performed at all stages, and therefore the reference pitch angular velocity λ _r ' can be obtained more accurately by using the transfer characteristic G _p λ'(s).

According to the control of the second embodiment configured as described above, pitching vibration of the electric vehicle 1 is suppressed, as in the control of the first embodiment, and at the same time, the desired acceleration/deceleration determined according to the accelerator opening degree θ, etc., is obtained.

Furthermore, the control of the second embodiment is particularly robust against fluctuations in the dead time τ. That is, in the control of the second embodiment, by combining the FF compensation process S1101, the effect of fluctuations in the dead time τ is reduced, and the control performance is improved.

For example, when the FB compensation process S1102 of the first or second embodiment is executed alone, the pitch angular velocity λ' for the second front wheel driving force command value F _f2 ^* and the second rear wheel driving force command value F _r2 ^* is fed back, and at the same time, fluctuations (small changes) in the dead time τ caused by various communications, calculations, and timing variations in the detection of the pitch angular velocity λ' are also fed back. As a result, the control performance may be degraded by the fluctuations in the dead time τ. On the other hand, the FF compensation process S1101 is a feedforward process, and is not affected by such fluctuations in the dead time τ. Therefore, when the FF compensation process S1101 and the FB compensation process S1102 are executed in the pitch angle control calculation process as in the control of the second embodiment, the desired acceleration/deceleration can be obtained while suppressing pitching vibration, and the control performance is maintained even if the fluctuations in the dead time τ occur.

In the second embodiment, the driving force transfer amount _TdFF is calculated based on the reference value (reference pitch angle _λr ) and the estimated value (pitch angle estimated value λ^) of the pitch angle λ in the FF compensation process S1101, but this is not limited to the above. In the FF compensation process S1101, the driving force transfer amount TdFF can be calculated based on the reference value (reference pitch angular velocity _λr ') of the pitch angular velocity λ' and its estimated value (reference pitch angular velocity estimated value (not shown)). The reference pitch angular velocity estimated value is calculated in the same manner as the reference pitch angle estimated value λ^. In addition, the method of calculating the driving force transfer amount _TdFF from the reference pitch angular velocity _{λr '} and the reference pitch angular velocity estimated value is the same as when the reference value and the estimated value of the pitch angle λ are used.

As described above, in the control method for the electric vehicle 1 according to the second embodiment, the first front-wheel driving force command value F _f1 ^* and the first rear-wheel driving force command value F _r1 ^* are calculated. Then, a reference value of the pitch angular velocity λ' or the pitch angle λ (e.g., reference pitch angle λ _r ⁾ is calculated based on the first front-wheel driving force command value F _f1 ^* and the first rear-wheel driving force command value F _r1 *. Also, an estimated value of the pitch angular velocity λ' or the pitch angle λ (e.g., pitch angle estimated value λ^) is calculated based on the first front-wheel driving force command value F _f1 ^* and the first rear-wheel driving force command value F _r1 ^* . Then, a first driving force transfer amount (T _dFF ), which is a driving force transfer amount, is calculated based on the difference between the reference value and the estimated value (e.g., λ _r - λ^). Then, a first correction (driving force command value correction process _S1206 ) is executed to correct the first front wheel driving force command value F _f1 ^* and the first rear wheel driving force command value F _r1 ^* based on the first driving force transfer amount (T dFF ). As a result, the front wheel driving force command value after the first correction (FF compensated front wheel driving force command value F _λf ^* ) and the rear wheel driving force command value after the first correction (FF compensated rear wheel driving force command value F _λr ^* ) are calculated. Furthermore, a second driving force transfer amount (driving force transfer amount T dFB in FB compensation process S1102), which is a driving force transfer amount, is calculated based on the difference (λ _r '-λ ') between the reference value (e.g. reference pitch angular velocity λ _r ') and the detected value (e.g. pitch angular velocity λ _' ) of the pitch angular velocity λ' or the pitch angle λ. Then, a second correction (driving force command value correction process _S605 ) is executed to correct the first corrected front wheel driving force command value (FF compensated front wheel driving force command value F _λf ^* ) and the first corrected rear wheel driving force command value (FF compensated rear wheel driving force command value F _λr ^* ) based on the second driving force movement amount (T dFB ). This allows the final front wheel driving force command value (second front wheel driving force command value F _f2 ^* ) and the final rear wheel driving force command value (second rear wheel driving force command value F _r2 ^* ) to be calculated.

With this configuration, the control method for the electric vehicle 1 according to the second embodiment can obtain the desired acceleration and deceleration while suppressing pitching vibration, and maintain control performance even if fluctuations occur in the dead time τ.

Although the embodiments of the present invention have been described above, the configurations described in the above embodiments merely show some of the application examples of the present invention and are not intended to limit the technical scope of the present invention. For example, the reference pitch angular velocity _λr ' is calculated using the transfer characteristic G _r λ'(s) of equation (6), but any response using a rate of change limiter or the like may be used. The same applies to the reference pitch angle _λr .

1: Electric vehicle, 2: Front drive system, 3: Rear drive system, 4: Battery, 5: Motor controller, 10: Front motor, 11: Rotation sensor, 12: Rear motor, 13: Rotation sensor, 14: Front wheel, 16: Rear wheel, 17: Pitch rate sensor, 20: Front inverter, 22: Rear inverter, 26: Current sensor, 28: Current sensor, 30: Front reduction gear, 32: Rear reduction gear, S401: Driving force distribution process, S402: Front wheel driving force calculation process, S403: Rear wheel driving force calculation process, S601 : Standard pitch angular velocity calculation process, S602: Difference calculation process, S603: Driving force movement amount calculation process, S604: Driving force movement amount limiting process, S605: Driving force command value correction process, S606: Phase adjustment process, S1101: FF compensation process, S1102: FB compensation process, S1201: Standard pitch angle response calculation process, S1202: Pitch angle estimation process, S1203: Difference calculation process, S1204: Driving force movement amount calculation process, S1205: Driving force movement amount limiting process, S1206: Driving force command value correction process, S1207: Phase adjustment process

Claims (9)

A control method for an electric vehicle having a first motor that drives front wheels and a second motor that drives rear wheels, comprising:
calculating a front wheel driving force command value that determines the driving force of the front wheels and a rear wheel driving force command value that determines the driving force of the rear wheels based on a target driving force command value that determines a target driving force for the electric vehicle;
calculating a reference value of an angular velocity or an angle of a pitching vibration generated in the electric vehicle based on the front wheel driving force command value and the rear wheel driving force command value;
obtaining a detection value of the angular velocity or the angle using a sensor that detects the pitching vibration;
calculating a driving force transfer amount representing a magnitude of a driving force to be transferred between the front wheels and the rear wheels in order to suppress the pitching vibration, based on a difference between the reference value and the detected value of the angular velocity or the angle;
correcting the front wheel driving force command value and the rear wheel driving force command value based on the driving force transfer amount;
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to claim 1, comprising:
the reference value of the angular velocity or the angle is calculated based on vertical forces represented by instantaneous rotation angles of the front wheels and the rear wheels, which are determined in advance by a driving force generated at the front wheels and the rear wheels, an inertial force, and an operating state of a suspension;
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to claim 1 or 2, comprising:
the reference value of the angular velocity or the angle is calculated based on a dead time from the front wheel driving force command value and the rear wheel driving force command value to the driving forces generated at the front wheels and the rear wheels, and a response delay of the first motor and the second motor.
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to any one of claims 1 to 3,
The driving force movement amount is calculated using a filter having a steady-state characteristic of zero.
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to claim 4, comprising:
The filter is a band-pass filter that passes a resonant frequency of the angular velocity or the angle.
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to any one of claims 1 to 5,
the driving force transfer amount is limited to a value that can be taken within a range in which the signs of the front wheel driving force command value and the rear wheel driving force command value are the same.
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to any one of claims 1 to 6,
adjusting a dynamic characteristic and a phase of the front wheel driving force command value and/or the rear wheel driving force command value corrected based on the driving force transfer amount;
A method for controlling an electric vehicle. A method for controlling an electric vehicle according to any one of claims 1 to 7,
calculating the front wheel driving force command value and the rear wheel driving force command value;
calculating the reference value of the angular velocity or the angle based on the front wheel driving force command value and the rear wheel driving force command value;
calculating an estimated value of the angular velocity or the angle based on the front wheel driving force command value and the rear wheel driving force command value;
calculating a first driving force transfer amount, which is the driving force transfer amount, based on a difference between the reference value and the estimated value;
calculating the front wheel driving force command value after the first correction and the rear wheel driving force command value after the first correction by performing a first correction to correct the front wheel driving force command value and the rear wheel driving force command value based on the first driving force movement amount;
calculating a second driving force movement amount, which is the driving force movement amount, based on a difference between the reference value and the detected value;
a second correction is executed to correct the front wheel driving force command value after the first correction and the rear wheel driving force command value after the first correction based on the second driving force transfer amount, thereby calculating a final front wheel driving force command value and a final rear wheel driving force command value.
A method for controlling an electric vehicle. A control device for an electric vehicle having a first motor that drives front wheels and a second motor that drives rear wheels,
The control device includes:
calculating a front wheel driving force command value that determines a driving force of the front wheels and a rear wheel driving force command value that determines a driving force of the rear wheels based on a target driving force for the electric vehicle;
calculating a reference value of an angular velocity or an angle of a pitching vibration generated in the electric vehicle based on the front wheel driving force command value and the rear wheel driving force command value;
obtaining a detection value of the angular velocity or the angle using a sensor that detects the pitching vibration;
calculating a driving force transfer amount representing a magnitude of a driving force to be transferred between the front wheels and the rear wheels in order to suppress the pitching vibration, based on a difference between the reference value and the detected value of the angular velocity or the angle;
correcting the front wheel driving force command value and the rear wheel driving force command value based on the driving force transfer amount;
A control device for an electric vehicle.

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