JP7723382B2 - Vehicle control device - Google Patents

Description

This case relates to a vehicle control device equipped with a differential mechanism that applies a torque difference to the left and right wheels and two electric motors connected to this differential mechanism.

Conventionally, in electric vehicles equipped with two independent electric motors, a differential mechanism (power distribution mechanism) is known that mechanically links each electric motor to the left and right wheels, and if there is a difference in output torque between the left and right electric motors, amplifies the torque difference and transmits it to the left and right wheels (see, for example, Patent Documents 1 and 2). The inclusion of a differential mechanism with an amplification function has the advantage of being able to generate a large torque difference between the left and right wheels.

Patent No. 4637136 Patent No. 4907390

However, because the differential mechanism mechanically connects two electric motors to the left and right wheels, their rotations (torque) can interfere with each other. This interference can potentially cause vehicle vibration. For example, if the vibration characteristics caused by torque interference change depending on the vehicle's turning state, the control required to suppress the vibration becomes complicated. Note that this same issue can also arise if the differential mechanism does not have an amplification function.

The vehicle control device in this case was devised in light of these issues, and one of its objectives is to simplify the control configuration by compensating for torque interference specific to the mechanism in a vehicle equipped with a differential mechanism capable of applying a torque difference to the left and right wheels and two electric motors. However, this objective is not limited to this, and another objective of this case is to achieve effects that cannot be obtained with conventional technology, which are derived from the various components shown in the detailed description of the invention described below.

The vehicle control device disclosed herein is a vehicle control device including a differential mechanism that imparts a torque difference to left and right wheels and two electric motors connected to the differential mechanism, and includes: a calculation unit that calculates left and right axle control torques based on driver operation, a non-interference compensator that cancels, from the left and right axle control torques calculated by the calculation unit, interference torques that affect opposite left and right sides due to changes in wheel speed of the left and right wheels, and a control unit that controls each of the electric motors based on the left and right second axle control torques whose interference has been canceled by the non-interference compensator. In addition, the non-interference compensator cancels the interference torque by taking into account dynamic factors of a target plant, including the left and right axles and a plant located upstream of the axles in a power transmission path from the electric motors to the left and right wheels.

The disclosed vehicle control device implements a decoupling compensator, which cancels out the interference torque acting from opposite sides, allowing the differential mechanism to be treated as equivalently independent of the left and right. This allows the control to compensate for torque interference specific to the mechanism, simplifying the configuration of various controls, including vibration suppression control.

1 is a schematic diagram of a vehicle to which a control device according to an embodiment is applied; 1 is a skeleton diagram for explaining a configuration example of a differential mechanism mounted on a vehicle according to an embodiment; FIG. 3 is a velocity diagram of the differential mechanism shown in FIG. 2 . FIG. 2 is a block diagram showing an example of a control device of FIG. 1 . FIG. 5 is a block diagram illustrating a model of a target plant taken into account by a decoupling compensator included in the control device of FIG. 4 . FIG. 10 is a block diagram showing an example of a control device including a decoupling compensator according to a modified example. 10 is an example of a flowchart executed by a control device according to an embodiment.

Vehicle control devices according to embodiments will be described with reference to the drawings. The embodiments described below are merely examples, and are not intended to exclude various modifications or technological applications not explicitly stated in the following embodiments. The configurations of each embodiment can be modified in various ways without departing from the spirit of the embodiments. Furthermore, they can be selected or combined as needed.

[1. Vehicle configuration]
FIG. 1 is a schematic diagram of a vehicle 1 equipped with a control device 10 according to this embodiment. The vehicle 1 is equipped with two motors 2 (electric motors) that drive left and right wheels 5 (rear wheels in this case). In the following description, the letter "L" or "R" suffixed to a reference numeral indicates the location of the element associated with that reference numeral (whether it is on the left or right side of the vehicle 1). For example, 5L indicates one of the left and right wheels 5 located on the left side of the vehicle (i.e., the left wheel), and 5R indicates the other located on the right side (i.e., the right wheel).

The two motors 2 have the function of driving at least either the front or rear wheels of the vehicle 1, and may have the function of driving all four wheels. Hereinafter, the one of the two motors 2 located on the left side will be referred to as the left motor 2L, and the other located on the right side will be referred to as the right motor 2R. The left motor 2L and right motor 2R operate independently of each other and can individually output driving forces of different magnitudes. In this embodiment, the left motor 2L and right motor 2R have the same rated output and are provided as a pair.

The vehicle 1 is equipped with a power distribution mechanism 3 (differential mechanism) that applies a torque difference to the left and right wheels 5. In this embodiment, the power distribution mechanism 3 amplifies the torque difference between the two motors 2 and then distributes the torque to each of the left and right wheels 5. As shown in FIG. 2 , the power distribution mechanism 3 includes a pair of reduction mechanisms 3g (gear trains surrounded by dashed lines in FIG. 2 ) that reduce the rotational speed of each motor 2. The reduction mechanisms 3g increase the torque (driving force) output from the motors 2 by reducing the torque. The reduction ratio G of the reduction mechanisms 3g is set appropriately depending on the output characteristics and performance of the motors 2. In this embodiment, the reduction ratios G of the left and right reduction mechanisms 3g are the same. Note that if the torque performance of the motors 2 is sufficiently high, the reduction mechanisms 3g may be omitted. The pair of motors 2 are connected to the power distribution mechanism 3, and by reducing the rotational speed of the motors 2, the torque is amplified and transmitted (distributed) to each of the left and right wheels 5.

As shown in Figures 1 and 2, the power distribution mechanism 3 is a differential mechanism with a yaw control function (AYC function) and is interposed between the axle 4 (left axle 4L) connected to the left wheel 5L and the axle 4 (right axle 4R) connected to the right wheel 5R. The yaw control function actively controls the ratio of the driving force (driving torque) shared between the left and right wheels 5 to adjust the yaw moment and stabilize the posture of the vehicle 1. The power distribution mechanism 3 contains a planetary gear mechanism, a differential gear mechanism, and other components. A vehicle drive system including a pair of motors 2 and the power distribution mechanism 3 is also called a DM-AYC (Dual-Motor Active Yaw Control) system.

Here, an example of the power distribution mechanism 3 will be described using Figure 2. The power distribution mechanism 3 shown in Figure 2 has a pair of reduction mechanisms 3g set to a reduction ratio G, and a planetary gear mechanism that has the function of amplifying the torque difference by a predetermined amplification factor. The power distribution mechanism 3 is preferably disposed between the left and right motors 2L, 2R in the vehicle width direction.

The planetary gear mechanism is a double-pinion planetary gear in which the sun gear 3s1 and ring gear 3r are input elements, and the sun gear 3s2 and carrier 3c are output elements. Torque from the left motor 2L is input to the sun gear 3s1, and torque from the right motor 2R is input to the ring gear 3r. The input element is arranged to rotate integrally with the idler gear 37 (described below), and the output element is arranged to rotate integrally with the output shaft 33.

Each reduction mechanism 3g is configured to reduce the rotational speed of each motor 2 in two stages using four gears 34, 35, 36, and 37 attached to three parallel-arranged shafts 31, 32, and 33. Hereinafter, the three shafts will be referred to as the motor shaft 31, counter shaft 32, and output shaft 33, in order from the upstream side of the power transmission path from each motor 2 to the left and right wheels 5. Two of these shafts 31-33 are provided in each power distribution mechanism 3. The two motor shafts 31, two counter shafts 32, and two output shafts 33 located on the left and right are each configured identically (symmetrically). Furthermore, the reduction mechanisms 3g attached to these shafts 31-33 are also configured identically (symmetrically) on the left and right.

The motor shaft 31 is positioned coaxially with the rotation shafts of the left and right motors 2 and has a first fixed gear 34. The counter shaft 32 is provided with a second fixed gear 35 that meshes with the first fixed gear 34 and a third fixed gear 36 that has a smaller diameter than the second fixed gear 35. The larger-diameter second fixed gear 35 is positioned more inward in the vehicle width direction than the smaller-diameter third fixed gear 36. The output shaft 33 is provided with an idler gear 37 that meshes with the third fixed gear 36. The first fixed gear 34 and second fixed gear 35 form a first-stage reduction gear train, and the third fixed gear 36 and idler gear 37 form a second-stage reduction gear train. The left idler gear 37 is connected to the sun gear 3s1, and the right idler gear 37 is connected to the ring gear 3r.

The reduction ratio G of the reduction mechanism 3g can be expressed as the ratio (or the ratio of the number of gear teeth) between the rotational angular velocity transmitted from the motor 2 to the reduction mechanism 3g and the rotational angular velocity transmitted from the reduction mechanism 3g to the power distribution mechanism 3. Furthermore, symbols _b1 and _b2 in FIG. 2 are reduction ratios (equivalent second speed ratios) determined by the structure of the gears built into the power distribution mechanism 3. Here, symbol b1 denotes the reduction ratio of the path through which the driving force of the left motor 2L is transmitted to the right wheel 5R, and symbol _b2 denotes the reduction ratio of the path through which the driving force of the right motor 2R is transmitted to the left wheel _5L .

As shown in FIG. 1, each motor 2L, 2R is electrically connected to a battery 7 via an inverter 6 (6L, 6R). The inverter 6 is a converter (DC-AC inverter) that converts between the power of the DC circuit on the battery 7 side (DC power) and the power of the AC circuit on the motor 2 side (AC power). The battery 7 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is a secondary battery capable of supplying high-voltage DC current of several hundred volts. When the motor 2 is powered, the DC power is converted to AC power by the inverter 6 and supplied to the motor 2. When the motor 2 is generating power, the generated power is converted to DC power by the inverter 6 and charged into the battery 7.

The control device 10 is one of the electronic control units (ECU) installed in the vehicle 1. The control device 10 is equipped with a processor (microprocessor) such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit), as well as ROM (Read Only Memory), RAM (Random Access Memory), and non-volatile memory. The processor is an arithmetic processing device that incorporates a control unit (control circuit), an arithmetic unit (arithmetic circuit), and cache memory (registers). The ROM, RAM, and non-volatile memory are memory devices that store programs and active data. The contents of the decisions and controls performed by the control device 10 are recorded and saved in memory as firmware or application programs, and when a program is executed, the program contents are expanded into memory space and executed by the processor.

Sensors for acquiring various information about the vehicle 1 are connected to the control device 10. In the example shown in FIG. 1, an accelerator position sensor 21, a brake sensor 22, a steering angle sensor 23, a vehicle speed sensor 24, a wheel speed sensor 25, and a motor rotation speed sensor 26 are connected to the control device 10. The control device 10 controls each inverter 6 based on the various information detected by these sensors 21 to 26, thereby controlling each motor 2.

The accelerator opening sensor 21 is a sensor that detects the amount of depression of the accelerator pedal (accelerator opening) and the depression speed. The brake sensor 22 is a sensor that detects the amount of depression of the brake pedal (brake pedal stroke) and the depression speed. The steering angle sensor 23 is a sensor that detects the steering angle (actual steering angle or steering angle) of the left and right wheels 5, and the vehicle speed sensor 24 is a sensor that detects the vehicle speed (vehicle speed).

The wheel speed sensors 25 (25L, 25R) are sensors that detect the wheel angular velocity _ωL of the left wheel 5L and the wheel angular velocity _ωR of the right wheel 5R, and are provided individually near the left wheel 5L and the right wheel 5R. The motor rotation speed sensors 26 (26L, 26R) are sensors (e.g., resolvers, Hall sensors, encoders) that detect the rotation angular velocities _ωLm , _ωRm of the left and right motors 2L, 2R, and are provided individually for the left motor 2L and the right motor 2R, respectively.

In a two-input, two-output mechanism like the power distribution mechanism 3 described above, the motors 2 and the left and right wheels 5 are mechanically connected, which can cause torque interference between the left and right opposite sides of the power transmission path from each motor 2 to the left and right wheels 5. The torque between the left and right opposite sides (hereinafter referred to as "interference torque") here refers to torque that affects the left and right opposite sides due to changes in the wheel speed of the left and right wheels 5. Interference torque is generated by dynamic factors (specifically, inertia, viscosity, and rigidity) of the target plant, including the left and right axles 4L, 4R and the plant located upstream of each axle 4 in the power transmission path (motor 2, shafts 31-33, carrier 3c, various gears, etc.), as well as friction between the equipment and parts included in the target plant. Here, we will focus on the inertia of the target plant and explain a configuration for canceling inertial torque using Figure 2 as an example.

As described above, the power split mechanism 3 of Figure 2 is equipped with a planetary gear mechanism. Figure 3 shows a speed diagram relating to the input and output of this power split mechanism 3. In the diagram, _b1 and _b2 are the reduction ratios (equivalent second speed ratios), T _Lm and T _Rm are torques (hereinafter referred to as "motor control torques") commanded to the motors 2L and 2R, and T _Lds and T _Rds are torques (hereinafter referred to as "upstream axle input torques") transmitted to the axles 4L and 4R. Also, ω _Lm and ω _Rm are motor rotational angular velocities, and ω _Lds and ω _Rds are rotational angular velocities of the axles 4L and 4R (upstream axle rotational angular velocities).
From FIG. 3, the torque relational expression (Equation 1) and the rotational angular velocity relational expression (Equation 2) can be expressed as follows:

Furthermore, the motor control torques T _Lm and T _Rm are calculated by subtracting the motor inertia torques T _LIm and T _RIm from the motor drive torques T _LDm and T _RDm of the respective motors 2, as shown in the following equation 3. The motor inertia torques T _LIm and T _RIm are expressed by the following equation 4. G is the reduction ratio and _Jm is the motor inertia.

When the upstream axle input torques T _Lds and T _Rds including the inertia on the axle 4 are calculated from the above equations 1 to 4, the following equation 5 is obtained.

As seen in the third term on the right side of the above equation 5, the equation representing the left axle upstream input torque T _Lds contains the derivative of the right axle upstream rotational angular velocity ω _Rds (i.e., the axle rotational angular acceleration), and the equation representing the right axle upstream input torque T _Rds contains the derivative of the left axle upstream rotational angular velocity ω _Lds (i.e., the axle rotational angular acceleration). Thus, it can be seen that the left and right upstream axle input torques T _Lds and T _Rds are interfered with by the inertia torques on the opposite left and right sides (the third term on the right side of equation 5).

This inertia torque is one type of interference torque mentioned above. The presence of interference torque may make it difficult for the vehicle 1 to achieve torque that satisfies the driver's demands, or may cause unexpected vibrations in the vehicle 1. Furthermore, the control configuration to address this, i.e., the control configuration for achieving torque that satisfies the driver's demands and suppressing vibrations, may become complicated. Therefore, the control device 10 of this embodiment compensates for the interference torque in advance through control, making it possible to treat the power distribution mechanism 3 as equivalently independent of the left and right, thereby simplifying the control configuration.

2. Control Configuration
As shown in Fig. 1, the control device 10 includes a calculation unit 11, a decoupling compensator 12, and a control unit 13. These elements are shown by conveniently classifying the functions of the control device 10. Each of these elements can be written as an independent program, or multiple elements can be written as a composite program. The programs corresponding to each element are stored in the memory or storage device of the control device 10 and executed by the processor.

Calculation unit 11 calculates left and right axle control torques based on driver operation. Decoupling compensator 12 cancels the above-mentioned interference torques from the left and right axle control torques calculated by calculation unit 11. Control unit 13 then controls each motor 2 based on the left and right axle control torques (hereinafter referred to as "second axle control torques") whose interference has been canceled out by decoupling compensator 12.

Each element 11-13 will be described in detail below using Figures 4-6. Figure 4 is a block diagram showing an example of the control device 10, and Figure 5 is a block diagram showing an example of a model of the target plant 40 taken into account by the decoupling compensator 12. Figure 6 is a block diagram showing an example of a control device 10' equipped with a decoupling compensator 12' according to a modified example. The computational processing and control configuration of the control devices 10, 10' including the decoupling compensators 12, 12' is designed based on the model of the target plant 40. Note that the control device 10 in Figure 4 and the control device 10' in Figure 6 are identical in configuration apart from the decoupling compensators 12, 12', and therefore the same configuration will be described with reference to Figure 4.

The calculation unit 11 uses various information detected by, for example, the accelerator opening sensor 21, the brake sensor 22, and the steering angle sensor 23 as the driver's operation. In this example, the calculation unit 11 first calculates the axle request torques T _L-ref and T _R-ref indicated by the left arrow in FIG. 4 , and then calculates the axle control torques T′ _L-ref and T′ _R-ref . The calculation of the former may take into account the vehicle speed of the vehicle 1 in addition to the driver's operation. For example, the calculation unit 11 may calculate the total drive torque, determine a target value for the torque difference to be applied to the left and right wheels 5, and calculate the left axle request torque T _L-ref and the right axle request torque T _R-ref from the total drive torque and the target torque difference. Note that the method of calculating the axle request torque is not particularly limited.

The calculation unit 11 in this example calculates axle control torques T'L _-ref , T'R _-ref by performing axle torque control using the axle request torques T _L-ref , T _R-ref as input values. The axle torque control is a control that realizes axle torque in accordance with the axle request torque based on the driver's operation, and includes feedback control using the upstream rotational angular accelerations of the left and right axles (differential values of ω _Lds , ω _Rds ). As shown in Figure 4, the axle torque control includes one feedforward control (FF control), one feedback control (FB control), and axle torque observer, each provided for the left and right axles.

The axle torque observer is an estimator that estimates the actually generated axle torque (estimated axle torque) by subtracting the inertia torque calculated from the upstream axle rotational angular acceleration from the second axle control torques T" _L-ref , T" _R-ref . The inertia torque is calculated by multiplying the upstream axle rotational angular acceleration by the upstream axle motor equivalent inertia. The calculation unit 11 may calculate the upstream axle rotational angular acceleration using three methods described below.

In FF control, the axle request torques T _L-ref and T _R-ref are converted into values that take into account the decoupling compensators 12 and 12'. In FB control, for each of the left and right axle, an FB amount to be added to the axle control torque after FF control is calculated based on the deviation between the axle request torques T _L-ref and T _R-ref and the estimated axle torque. In this way, the calculation unit 11 in this example calculates the axle control torques T _{' L-ref} and T _{' R-ref} by using the deviation between the axle request torques T L- _ref and T _R-ref and the estimated axle torque in FB control and adding the FB amount to the axle control torque after FF control. Note that the calculation method for the axle control torque is not limited to this. For example, the axle torque control may be omitted and the axle request torque based on the driver's operation may be used as the axle control torque as is, or the axle control torque may be calculated by multiplying the axle request torque based on the driver's operation by some coefficient or adding or subtracting some numerical value to or from the axle control torque.

The decoupling compensators 12, 12' are compensators that cancel out interference torque that affects opposite left and right sides. The decoupling compensator 12 shown in Figure 4 cancels out interference torque caused by changes in wheel speed due to the difference in torque applied to the left and right wheels 5. The decoupling compensator 12' shown in Figure 6 is a compensator that cancels out interference torque caused by changes in wheel speed due to the driving state of the vehicle 1.

When a torque difference is applied to the left and right wheels 5, one wheel 5 to which a larger torque is applied accelerates, while the other wheel 5 to which a smaller torque is applied decelerates, enabling smooth cornering. However, when the wheel speeds of the left and right wheels 5 change (one accelerates and the other decelerates), part of the inertia torque of the target plant 40 acts on the vehicle 1 as an interference torque that inhibits the torque difference that promotes cornering. The decoupling compensator 12 in Figure 4 compensates for the interference torque that occurs when a torque difference is applied to the left and right wheels 5.

Even when no torque difference is applied to the left and right wheels 5 (i.e., when torque control is not implemented), the outer wheel accelerates and the inner wheel decelerates during a turn. However, even in this case, if the wheel speeds of the left and right wheels 5 change (one accelerates and the other decelerates), part of the inertia torque of the target plant 40 acts on the vehicle 1 as an interference torque that hinders turning. Even when not turning, for example, if only one wheel 5 drives on a slippery road surface or one wheel slips, only one wheel 5 accelerates, causing the wheel speeds of the left and right wheels 5 to change. In this way, an interference torque is generated when a change in the wheel speeds of the left and right wheels 5 occurs, depending on the driving state of the vehicle 1. The decoupling compensator 12' in Figure 6 compensates for the interference torque generated by the difference in wheel speed between the left and right wheels.

The decoupling compensator 12 in Fig. 4 is designed to cancel out the interference torque in consideration of the dynamic factors of the target plant 40. As described above, the target plant 40 includes the left and right axles 4L, 4R, and plants (motor 2, shafts 31-33, carrier 3c, various gears, etc.) located upstream of each axle 4 in the power transmission path. In the target plant 40, as shown in the model in Fig. 5, the output torques T _LM and T _RM of the left and right motors 2 are converted into upstream axle input torques T _Lds and T _Rds , and then converted into axle torsion torques T _L and _TR by the transfer function Gp(s) and transmitted to the left and right wheels 5.

The transfer function Gp(s) is derived by formulating and solving an equation of motion for the upstream axle, an equation of motion for the downstream axle, and an equation of motion for the axle torsional torque for each of the left and right sides. The transfer function Gp(s) is expressed, for example, as a 2 x 2 determinant as shown in the following equation 6, and the axle torsional torques T _L and _TR are expressed by equation 7. As is clear from equation ₇ , the right axle upstream input torque T _Rds affects the left axle torsional torque T _L , and the left axle upstream input torque T _Lds affects the right axle torsional torque TR.

The decoupling compensator 12 is expressed by the determinant of the following equation 8 so as to cancel out the interference torques affecting the left and right opposite sides (here, the upstream input torques T _Rds and T _Lds of the left and right opposite axles) from the above equation 7.

By implementing the decoupling compensator 12, the axle torsion torques T _L and T _R are expressed by the following equation 9. As is clear from equation 9, the decoupling compensator 12 cancels out the interference torques that affect the opposite left and right sides from the axle torsion torques T _L and T _R.

The decoupling compensator 12' shown in Figure 6 is also designed to cancel out interference torque, taking into account the dynamic factors of the target plant 40. However, the decoupling compensator 12' is composed of a single first compensator 12A and left and right second compensators 12B. Like the decoupling compensator 12 in Figure 4, the first compensator 12A is designed, for example, as a determinant that cancels out interference torque. The second compensator 12B calculates interference torque from the wheel speed in advance and outputs it to the first compensator 12A. This compensates for the interference torque generated by the difference in wheel speed between the left and right wheels.

The upstream axle rotational angular accelerations on the left and right opposite sides are input to the left and right second compensators 12B. In this modification, the calculation unit 11 calculates the upstream axle rotational angular accelerations. The following three methods can be used as calculation methods, and any one of them may be used, or a combination of multiple methods may be used to adopt an average value or a median value.
First method: Calculation based on the left and right wheel speeds. Second method: Calculation based on the rotation speeds of the left and right motors 2. Third method: Calculation based on the steering angle and vehicle speed.

When the first method is used, the calculation unit 11 differentiates the left and right wheel angular velocities ω _L and ω _R (sensor values) detected by the wheel speed sensors 25L and 25R, and calculates the wheel angular acceleration as the upstream axle rotational angular acceleration as shown in the following equation 10.

When the second method is used, the calculation unit 11 differentiates the left and right motor rotational angular velocities ω _Lm , ω _Rm (sensor values) detected by the motor rotational speed sensors 26L, 26R, and calculates the upstream axle rotational angular acceleration based on the motor rotational angular acceleration. For example, in the case of a vehicle 1 equipped with the power distribution mechanism 3 shown in FIG. 2, the calculation unit 11 calculates the upstream axle rotational angular acceleration using the following equation 11.

When using the third method, the calculation unit 11 calculates the upstream axle rotational angular acceleration based on, for example, the steering angles (sensor values) of the left and right wheels 5 detected by the steering angle sensor 23 and the vehicle speed (sensor value) detected by the vehicle speed sensor 24. Alternatively, instead of using the sensor value of the vehicle speed sensor 24, the vehicle speed may be estimated from the left and right wheel speeds, and the upstream axle rotational angular acceleration may be calculated using the estimated vehicle speed value. The calculation method may be, for example, the third method described in International Application PCT/JP2021/013226.

Each second compensator 12B of the decoupling compensator 12' calculates an interference torque using the upstream rotational angular acceleration of the opposite left and right axles calculated by the calculation unit 11, and inputs the calculated interference torque to the first compensator 12A. The first compensator 12A uses the inverse of each left and right interference torque to cancel out the interference torque from each left and right axle control torque T'L _-ref , T'R _-ref . For example, the decoupling compensator 12' cancels out the interference torque contained in the axle control torques T'L _-ref , T'R _-ref by adding a numerical value that has the opposite sign to the interference torque and the same absolute value as the interference torque to the axle control torques T'L _-ref , T'R _{-ref, or by multiplying the axle control torques T'L-ref, T'R-ref} by the reciprocal of the interference torque, and outputs the second axle control torques T" _L-ref , T" _R-ref to the control unit 13.

The control unit 13 controls the left motor 2L based on the left second axle control torque T" _L-ref , and controls the right motor 2R based on the right second axle control torque T" _R-ref . The control unit 13, for example, converts the left and right second axle control torques T" _L-ref , T" _R-ref into left and right motor control torques T _Lm , _TRm , respectively, and controls each motor 2L, 2R. Because interference torques are canceled out from each second axle control torque T" _L-ref , T" _R-ref , it is possible to treat the power distribution mechanism 3 as equivalently independent of the left and right, simplifying the control configuration.

3. Flowchart
7 is an example of a flowchart executed by the above-described control device 10. This flowchart is repeatedly executed at a predetermined calculation cycle under predetermined conditions, for example, from when the vehicle 1 is in the Ready ON state until it is in the Ready OFF state, or while the vehicle is traveling (when the vehicle speed is not 0).

The control device 10 first acquires vehicle information detected by the various sensors 21 to 26 (step S1). Next, the calculation unit 11 calculates left and right axle required torques T _L-ref and T _R-ref (step S2), and then performs axle torque control to determine left and right axle control torques T' _L-ref and T' _R-ref (step S3). Next, the non-interacting compensators 12 and 12' calculate second axle control torques T" _L-ref and T" _R-ref by canceling out the interference torque from the left and right axle control torques (step S4). The control unit 13 calculates motor control torques T _Lm and T _Rm from the second axle control torques T" _L-ref and T" _R-ref (step S5), controls the left and right motors 2L and 2R (step S6), and returns from this flowchart.

[4. Actions and Effects]
In the control device 10 described above, by implementing the decoupling compensators 12, 12', the interference torque acting from the opposite left and right sides is cancelled out, and the left and right power distribution mechanisms 3 can be treated as equivalently independent. In this way, in a vehicle 1 equipped with a power distribution mechanism 3 that mechanically couples two motors 2L, 2R to the left and right wheels 5, the torque interference specific to the mechanism can be compensated for by control, which simplifies the configuration of various controls (for example, FF control and FB control) including vibration suppression control.

By providing the power distribution mechanism 3 described above, it is possible to apply a torque difference to the left and right wheels 5. When a torque difference is applied, the wheel speed of the outer wheel accelerates and the wheel speed of the inner wheel decelerates, resulting in a change in wheel speed. Even if an interference torque is generated due to a change in wheel speed caused by the torque difference applied to the left and right wheels 5, by implementing the decoupling compensator 12 shown in Figure 4, the interference torque can be canceled out and its effects eliminated. This makes it possible to create a virtual plant in which the FF control and FB control performed within the control device 10 can be controlled by treating the left and right wheels as independent mechanisms, simplifying the control configuration.

The calculation unit 11 calculates the axle control torque by performing axle torque control including FB control using the upstream axle rotational angular acceleration, thereby improving the calculation accuracy of the axle control torques T' _L-ref and T' _R-ref input to the decoupling compensators 12 and 12'.
Furthermore, the calculation unit 11 estimates the actually generated estimated axle torque using the second axle control torques T" _L-ref , T" _R-ref in the axle torque observer, and performs FB control using the deviation between the axle request torques T _L-ref , T _R-ref and the estimated axle torque. Therefore, the calculation accuracy of the axle control torques T'L _-ref , T'R _-ref input to the decoupling compensators 12, 12' can be further improved.

Furthermore, by implementing the decoupling compensator 12' shown in Figure 6, it is possible to cancel out interference torque caused by changes in wheel speed when the vehicle 1 is in a driving state other than when a torque difference is applied, such as when cornering or slipping. This expands the range of applications for the decoupling compensator 12' and further simplifies the control configuration.

The calculation unit 11 calculates the upstream axle rotational angular acceleration using one of three methods and then calculates the interference torque using this. Specifically, when using the first method, it is only necessary to differentiate the left and right wheel angular velocities ω _L and ω _R (sensor values) detected by the wheel speed sensors 25L and 25R, so the upstream axle rotational angular acceleration can be calculated by a simple calculation. On the other hand, when using the second method, the upstream axle rotational angular acceleration can be calculated accurately based on both the left and right motor rotational angular velocities ω _Lm and ω _Rm (sensor values) detected by the two motor rotational speed sensors 26L and 26R, so the upstream axle rotational angular acceleration can be calculated accurately and the interference torque can be canceled out with high precision.

Furthermore, when the vehicle 1 is turning, the upstream axle rotational angular acceleration can also be calculated from the steering angle and vehicle speed using the third method. When the first or second method is used in combination with the third method, the interference torque can be cancelled out with higher precision by using the average or median value of the upstream axle rotational angular acceleration calculated using the multiple methods.
The decoupling compensators 12 and 12' are designed taking into consideration the dynamic factors (inertia, viscosity, stiffness) of the target plant, and therefore can cancel out the interference torque with higher precision.

[5. Other]
The configuration of the control device 10 described above is an example and is not limited to the above. For example, the above-described decoupling compensators 12, 12' are designed to focus on the inertia of the target plant and cancel out the inertia torque, which is one type of interference torque. However, a decoupling compensator that cancels out the interference torque may be designed taking into account not only the inertia of the target plant but also its rigidity and viscosity. Furthermore, the decoupling compensator may be designed based on the configuration of the two electric motors and differential device mounted on the vehicle 1.

Furthermore, the configuration of the vehicle 1 described above is an example and is not limited to the above. For example, the configuration of the power distribution mechanism 3 is not limited to that shown in FIG. 2 , and various configurations of planetary gear mechanisms and mechanisms other than planetary gear mechanisms can be employed. The vehicle 1 may be a two-wheel drive (rear-wheel drive or front-wheel drive) vehicle or a four-wheel drive vehicle . If the vehicle is a four -wheel drive vehicle, it is sufficient that a differential mechanism that applies a torque difference to the left and right wheels using two electric motors is connected to at least one of the front and rear wheels.

1. Vehicle 2. Motor (electric motor)
2L Left motor 2R Right motor 3 Power distribution mechanism (differential mechanism)
5 Left and right wheels, wheel 7 Battery 10 Control device 11 Calculation unit 12, 12' Non-interacting compensator 12A First compensator 12B Second compensator 13 Control unit 21 Accelerator opening sensor 22 Brake sensor 23 Steering angle sensor 24 Vehicle speed sensor 25, 25L, 25R Wheel speed sensor 26, 26L, 26R Motor rotation speed sensor 40 Target plant

Claims (7)

A control device for a vehicle including a differential mechanism that applies a torque difference to left and right wheels and two electric motors connected to the differential mechanism,
a calculation unit that calculates left and right axle control torques based on a driver's operation;
a non-interference compensator that cancels out interference torques that affect opposite left and right sides due to changes in wheel speeds of the left and right wheels from the left and right axle control torques calculated by the calculation unit;
a control unit that controls each of the electric motors based on the left and right second axle control torques whose interference has been canceled by the decoupling compensator ,
The decoupling compensator cancels out the interference torque by taking into consideration dynamic factors of a target plant including left and right axles and a plant located upstream of the axles in a power transmission path from the electric motor to the left and right wheels.
A vehicle control device comprising: 2. The vehicle control device according to claim 1, wherein the non-interacting compensator cancels out the interference torque caused by the change in wheel speed due to the torque difference applied to the left and right wheels. 3. The vehicle control device according to claim 2, wherein the calculation unit includes feedback control using upstream rotational angular acceleration of each of the left and right axles of the vehicle and calculates the axle control torque by axle torque control that realizes axle torques in accordance with the required torques of the left and right axles based on the driver's operation. the axle torque control includes an axle torque observer that estimates an estimated axle torque, which is an actually generated axle torque, by subtracting an inertia torque calculated from the upstream axle rotational angular acceleration from the second axle control torque;
4. The vehicle control device according to claim 3, wherein the calculation unit uses a deviation between the axle request torque and the estimated axle torque in the feedback control. 5. The vehicle control device according to claim 1, wherein the non-interacting compensator cancels out the interference torque caused by a change in wheel speed due to a running state of the vehicle. the calculation unit calculates upstream rotational angular accelerations of the left and right axles of the vehicle based on sensor values of wheel speed sensors that detect the wheel speeds of the left and right wheels, or two sensor values of rotational speed sensors that detect the rotational speeds of the electric motors,
6. The vehicle control device according to claim 5, wherein the decoupling compensator calculates the interference torque using the upstream axle rotational angular acceleration calculated by the calculation unit, and uses an inverse element of the interference torque. the calculation unit calculates upstream rotational angular accelerations of the left and right axles of the vehicle based on the steering angles of the left and right wheels and the vehicle speed;
7. The vehicle control device according to claim 5, wherein the decoupling compensator calculates the interference torque using the upstream axle rotational angular acceleration calculated by the calculation unit, and uses an inverse element of the interference torque .