Driving force control device for right and left wheel independent drive type vehicle

Abstract

To provide a driving force control device for a right and left wheel independent drive type vehicle capable of suppressing generation of yaw moment accompanying change of a position of a center of gravity of the vehicle.SOLUTION: A left motor for driving a left wheel and a right motor for driving a right wheel paired with the left wheel are provided. A position of a center of gravity of a right and left wheel independent drive type vehicle is estimated (step S3), and correction torque for canceling yaw moment generated according to difference between an estimated position of a center of gravity estimated in the right and left wheel independent drive type vehicle and a predetermined position of a center of gravity is added to output torque of the left motor and the right motor (step S5).SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a driving force control device for a vehicle configured to drive left and right wheels independently.

Background Art

[0002] Patent Document 1 describes a control device for a four-wheel drive vehicle including a front motor that is a driving force source for a pair of front wheels and a rear motor that is a driving force source for a pair of rear wheels. When the operation of the rear motor is restricted according to the temperature of the rear motor or the temperature of the power storage device, this control device sets the output torque of the rear motor to a limit torque determined based on the temperature of the rear motor, subtracts a torque corresponding to the limit torque of the rear motor from the driving torque required for the vehicle, and sets the subtracted torque as the output torque of the front motor. Note that the front motor and the pair of front wheels are connected via a differential gear mechanism, and similarly, the rear motor and the pair of rear wheels are connected via a differential gear mechanism.

[0003] Further, Patent Document 2 describes a control device for a vehicle equipped with a pair of electric motors that drive left and right wheels and a differential mechanism that applies a torque difference to the left and right wheels. This control device is for improving the turning responsiveness of the vehicle body with respect to steering, and is configured to output a compensation torque for canceling a turning inhibition yaw moment caused by a difference between a first inertial torque in a power transmission path from the electric motor to the right wheel and a second inertial torque in a power transmission path from the electric motor to the left wheel from the pair of electric motors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the four-wheel drive vehicle described in Patent Document 1, since the motor and the drive wheels are connected via a differential mechanism, when the center of gravity position of the entire vehicle changes according to the presence or absence of passengers and cargo, their weight, or their position, torque is divided so that a large torque is transmitted to the wheels where the installation load increases. On the other hand, the wheels to which such a large torque is transmitted are closer to the center of gravity position of the vehicle than the wheels on the other side. That is, even if the distance between the center of gravity position and the drive wheels changes with the change in the center of gravity position, the driving force mechanically changes corresponding to the change in the distance. Therefore, it is possible to suppress the occurrence of a difference between the yaw moment based on the driving force of the right drive wheel and the yaw moment based on the driving force of the left drive wheel, and to suppress the deterioration of the running stability and operability of the vehicle.

[0006] On the other hand, in the case of a vehicle equipped with motors independently for the left and right wheels, the same torque is output from each motor, and the same torque is transmitted to the left and right drive wheels. Therefore, when the center of gravity position of the entire vehicle changes, the change in the distance between the center of gravity position and the drive wheels accompanying the change in the center of gravity position appears as a difference between the yaw moment based on the driving force of the right drive wheel and the yaw moment based on the driving force of the left drive wheel, and a yaw moment is generated to deflect the vehicle, which may deteriorate the running stability and operability of the vehicle.

[0007] Further, according to the control device described in Patent Document 2, a compensation torque for canceling the turning resistance yaw moment is obtained based on predetermined specifications such as the power transmission path from the electric motor to the drive wheels, the motor, or the tires. However, since the control device described in Patent Document 2 does not consider that the center of gravity position of the entire vehicle changes according to the passengers and cargo, even if a compensation torque for canceling the turning resistance yaw moment is output, a yaw moment may be generated with the change in the center of gravity position, which may deteriorate the running stability and operability of the vehicle.

[0008] The present invention has been made paying attention to the above technical problem, and an object thereof is to provide a driving force control device for a left and right wheel independent drive type vehicle that can suppress the generation of a yaw moment accompanying a change in the center of gravity position of the vehicle.

Means for Solving the Problems

[0009] In order to achieve the above object, the present invention is a driving force control device for a left and right wheel independent drive type vehicle including a left electric motor that drives a left wheel and a right electric motor that drives a right wheel paired with the left wheel, and includes a controller that controls the left electric motor and the right electric motor. The controller includes a center of gravity estimation unit that estimates the center of gravity position of the left and right wheel independent drive type vehicle, and a torque correction unit that adds a correction torque that cancels a yaw moment generated according to a difference between the estimated center of gravity position of the left and right wheel independent drive type vehicle estimated by the center of gravity estimation unit and a predetermined center of gravity position to the output torques of the left electric motor and the right electric motor.

[0010] In the present invention, it further includes a plurality of seats on which passengers are seated and a plurality of seating sensors provided for each of the plurality of seats to detect that the passengers are seated. The center of gravity estimation unit may estimate the center of gravity position of the left and right wheel independent drive type vehicle based on the positions of the seating sensors that have detected that the passengers are seated.

[0011] In the present invention, it further includes a plurality of suspensions that reciprocate in the vertical direction of the left and right wheel independent drive type vehicle to suppress the vertical vibration of each wheel, and a stroke sensor that detects the displacement amount of each of the plurality of suspensions. The center of gravity estimation unit may estimate the center of gravity position of the left and right wheel independent drive type vehicle based on the displacement amounts of the plurality of suspensions detected by the stroke sensor.

[0012] In the present invention, the torque correction unit may increase the torque of one of the left and right electric motors connected to the wheel on the side where the estimated center-of-gravity position estimated by the center-of-gravity estimation unit among the left and right wheels is closer to the predetermined center-of-gravity position, and decrease the torque of the other electric motor among the left and right electric motors.

[0013] In the present invention, the center-of-gravity estimation unit may estimate the center-of-gravity position of the left-and-right wheels independently-driven vehicle when the left-and-right wheels independently-driven vehicle is stopped or when the steering angle of the left-and-right wheels independently-driven vehicle is within a predetermined angle range during straight-ahead driving.

Advantages of the Invention

[0014] According to the present invention, the center-of-gravity position of a left-and-right wheels independently-driven vehicle is estimated, and a correction torque for canceling a yaw moment generated according to the difference between the estimated center-of-gravity position and a predetermined center-of-gravity position is added to the output torques of the left and right electric motors. Therefore, even if the center-of-gravity position of the entire left-and-right wheels independently-driven vehicle changes based on the position where a person rides on the left-and-right wheels independently-driven vehicle and their weight, or the loading position and weight of a load, the yaw moment accompanying the change in the center-of-gravity position can be canceled, and the generation of an unintended yaw moment can be suppressed. As a result, the straight-ahead drivability, turning drivability, or stability during braking can be improved. In other words, it is possible to suppress the deterioration of the operability during driving.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0016] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0017] The vehicle targeted by the present invention is provided with an electric motor (motor or motor - generator. Hereinafter referred to as motor) as a power source corresponding to each of the left front wheel and the right front wheel, or the left rear wheel and the right rear wheel, which are in a paired relationship with each other, and is configured to be able to drive the left wheel and the right wheel independently. This vehicle may be a vehicle with a total of four wheels, namely two front wheels and two rear wheels. In that case, a driving device may be provided for each of the two front wheels and the two rear wheels so that each of the two front wheels and the two rear wheels can be driven independently of each other, or motors may be provided for each of the two wheels on either the front side or the rear side, and the other two wheels may be a vehicle connected to a single electric motor via a differential gear.

[0018] FIG. 1 schematically shows an example of a four - wheel independent drive vehicle configured to be able to drive all four wheels independently of each other. The electric vehicle (hereinafter simply referred to as vehicle) Ve shown here includes a pair of left and right front wheels 1r, 1l and a pair of left and right rear wheels 2r, 2l, and drive units Pf, Pr as driving power sources are provided corresponding to the front wheels 1r, 1l and the rear wheels 2r, 2l respectively. These drive units Pf, Pr are each mainly composed of a motor and a gear reduction mechanism (transmission mechanism).

[0019] Fig. 2 shows an example of a drive unit Pr on the rear wheel 2r, 2l side in a skeleton diagram. This drive unit Pr is composed of a pair of drive systems that control the left and right rear wheels 2r, 2l independently of each other. Since these drive systems have a symmetric configuration, they will be described together without particularly specifying "right" or "left". In the following description, when the suffix of a reference sign has one character, "f" indicates for the front wheel, "l" indicates for the left wheel, "r" indicates for the right wheel or the rear wheel. When the suffix has two characters, the first character "f" indicates for the front wheel, "r" indicates for the rear wheel, the second character "r" indicates for the right wheel, and "l" indicates for the left wheel.

[0020] In the drive unit Pr for the rear wheels 2r, 2l, motors Mrr, Mrl are mounted with their rotation center axes oriented in the longitudinal direction of the vehicle Ve. Drive gears 3rr, 3rl are attached to the rotor shafts of these motors, and these drive gears 3rr, 3rl mesh with counter-driven gears 4rr, 4rl. The counter-driven gears 4rr, 4rl have a larger diameter than the drive gears 3rr, 3rl. Therefore, these gear pairs constitute a speed reduction mechanism. Counter-drive gears 5rr, 5rl, which are bevel gears, are provided so as to rotate integrally on the same axis as the counter-driven gears 4rr, 4rl. These counter-drive gears 5rr, 5rl mesh with driven gears 7rr, 7rl, which are bevel gears integral with drive shafts 6rr, 6rl connected to the rear wheels 2r, 2l. By making the driven gears 7rr, 7rl have a larger diameter than the counter-drive gears 5rr, 5rl, these gear pairs can be used as a speed reduction mechanism.

[0021] Fig. 3 shows an example of a drive unit Pf on the front wheel 1r, 1l side in a skeleton diagram. Since this drive unit Pf has a symmetric configuration, it will be described collectively without particularly specifying "right" or "left". Motors Mfr and Mfl are mounted with their rotation central axes facing the vehicle width direction (lateral direction), and drive gears 12fr and 12fl are attached to their rotor shafts. These drive gears 12fr and 12fl are meshed with idler gears 13r and 13l. Countershafts 14r and 14l are provided parallel to the rotation central axes of these idler gears 13r and 13l, and the idler gears 13r and 13l are meshed with counter driven gears 15fr and 15fl attached to these countershafts 14r and 14l.

[0022] Since the counter driven gears 15fr and 15fl are larger in diameter than the drive gears 12fr and 12fl attached to the motors Mfr and Mrl, a speed reduction mechanism is constituted by these gear pairs. Counter drive gears 16fr and 16fl are attached to the countershafts 14r and 14l, and these counter drive gears 16fr and 16fl are meshed with driven gears 18fr and 18fl integral with drive shafts 17fr and 17fl connected to the front wheels 1r and 1l. Since the driven gears 18fr and 18fl are larger in diameter than these counter drive gears 16fr and 16fl, a speed reduction mechanism is constituted by these gear pairs.

[0023] Note that the wheels 1l and 2l correspond to the "left wheels" in the embodiment of the present invention, the wheels 1r and 2r correspond to the "right wheels" in the embodiment of the present invention, the motors Mfl and Mrl correspond to the "left electric motors" in the embodiment of the present invention, and the motors Mfr and Mrr correspond to the "right electric motors" in the embodiment of the present invention.

[0024] The vehicle Ve shown in Fig. 1 is provided with a power storage device (Bat) 19 that exchanges electric power with each of the above motors Mfr, Mfl, Mrr, and Mrl. This power storage device 19 is mainly composed of a secondary battery such as a lithium-ion battery or a all-solid-state battery. That is, the power storage device 19 is composed of a DC power source. Each of the motors Mfr, Mfl, Mrr, and Mrl is, for example, a permanent magnet synchronous motor. These motors Mfr, Mfl, Mrr, and Mrl are connected to the power storage device 19 via power controllers PCfr, PCfl, PCrr, and PCrl mainly composed of inverters that convert the DC voltage of the power storage device 19 into an AC voltage and apply it to the motors Mfr, Mfl, Mrr, and Mrl, and also convert the AC voltage generated by the motors Mfr, Mfl, Mrr, and Mrl into a DC voltage to charge the power storage device 19. Therefore, the output torque of each of the motors Mfr, Mfl, Mrr, and Mrl and the braking torque during energy regeneration are controlled independently of each other. Note that the power controllers PCfr, PCfl, PCrr, and PCrl only need to have independent functions and may be configured as an integrated unit as a whole.

[0025] The vehicle Ve configured as described above can control the output torques of the motors Mfr, Mfl, Mrr, and Mrl independently of each other. Therefore, for example, it is possible to switch between a two-wheel drive running mode in which the motors Mrr and Mrl are controlled as driving power sources and the energization of the motors Mfr and Mfl is stopped, and a four-wheel drive running mode in which each of the motors Mfr, Mfl, Mrr, and Mrl is controlled as a driving power source. Also, in order to improve the turning performance, when the two-wheel drive running mode or the four-wheel drive running mode is set, it is possible to run with different torques between the right-side motors Mfr and Mrr and the left-side motors Mfl and Mrl.

[0026] In addition, in the vehicle Ve described above, in order to determine the center of gravity position of the entire vehicle Ve, pressure sensors are provided for each seat to detect whether an occupant is sitting on any seat or to detect the weight of the occupant sitting on the seat or the load placed on the seat. FIG. 4 shows an example of a seat 21 equipped with a pressure sensor 20. The seat 21 shown in FIG. 4 includes a seat cushion 22 on which an occupant sits, a seat back 23 attached vertically upward from the rear end of the seat cushion 22, and a headrest 24 attached to the upper end of the seat back 23. A pressure sensor 20 is provided at the central portion of the seat cushion 22. A plurality of pressure sensors 20 may be provided on one seat cushion 22, and may be configured to detect the weight of the occupant or the load sitting on the seat cushion 22 based on the total value. Note that the configuration of the seat 21 and the position where the pressure sensor 20 is provided are not limited to the example shown in FIG. 4. Further, a seating sensor that only detects an occupant sitting on the seat 21 or a load placed on the seat 21, but does not detect its weight, may be provided instead of the pressure sensor 20.

[0027] Furthermore, in the above-described vehicle Ve, a suspension 25 for absorbing the vertical load of the wheels is attached to each drive shaft 6rr, 6rl, 17fr, 17fl. FIG. 5 shows an example of the suspension 25, and this suspension 25 can be configured in the same manner as the suspension provided in a conventional vehicle. Specifically, it includes an upper rod 26 with its upper end connected to the vehicle body, a lower rod 27 attached to the upper rod 26 so as to be reciprocable in the axial direction and having its lower end connected to the drive shafts 6rr, 6rl, 17fr, 17fl, a coil spring 28 provided between the upper rod 26 and the lower rod 27 so as to press the lower rod 27 downward, and a shock absorber 29 that contains a non-compressible fluid inside and attenuates vibrations due to the flow resistance of the non-compressible fluid when the lower rod 27 moves up and down relative to the upper rod 26. Also, a stroke sensor 30 is provided for detecting the stroke amount (displacement amount) of the suspension 25, that is, the amount by which the lower rod 27 moves relative to the upper rod 26.

[0028] In addition, the vehicle Ve is provided with a controller (electronic control unit) 31 for controlling each motor Mfr, Mfl, Mrr, Mrl. The controller 31 is mainly composed of a microcomputer and performs calculations according to a predetermined program or by referring to a predetermined map using the input data and the data stored in advance, and outputs the result of the calculation to each of the above-described motors Mfr, Mfl, Mrr, Mrl as a control command signal.

[0029] Examples of the input signals and output signals for performing such control are shown in FIG. 6. Examples of the input signals include a vehicle speed signal from a vehicle speed sensor (not shown) that detects the vehicle speed, a wheel speed signal from a wheel speed sensor (not shown) that detects the rotational speed of each wheel, an accelerator opening signal from an accelerator opening sensor that detects the operation amount of an accelerator device (not shown), a steering angle signal from a steering angle sensor (not shown) that detects the steering angle of the vehicle Ve, a pressure signal from the pressure sensor 20 that detects the presence or absence of an occupant and their weight, and a stroke signal from the stroke sensor 30 that detects the stroke amount of the suspension 25. Examples of the command signals to be output include the torque of the motor Mrl for the left rear wheel 2l, the torque of the motor Mrr for the right rear wheel 2r, the torque of the motor Mfl for the left front wheel 1l, and the torque of the motor Mfr for the right front wheel 1r.

[0030] As shown in FIG. 6, the controller 31 includes a drive torque setting unit 32 for determining the drive torque required for the vehicle, a reference torque setting unit 33 for setting the reference torque of each motor Mfr, Mfl, Mrr, Mrl, a center of gravity estimation unit 34 for estimating the center of gravity position of the vehicle Ve, and a torque correction unit 35 for correcting the reference torque based on the center of gravity position (estimated center of gravity position) estimated by the center of gravity estimation unit 34.

[0031] The drive torque setting unit 32 is configured to set the required drive torque based on the vehicle speed detected by the vehicle speed sensor and the accelerator opening detected by the accelerator opening sensor, similar to a conventional vehicle. Specifically, the drive torque setting unit 32 stores a drive torque map for setting the required drive torque using the vehicle speed and the accelerator opening as parameters. It acquires the vehicle speed signal from the vehicle speed sensor and the accelerator opening signal from the accelerator opening sensor, and is configured to set the required drive torque of the vehicle Ve by referring to the drive torque map.

[0032] The reference torque setting unit 33 sets the torques of the motors Mfr, Mfl, Mrr, and Mrl in the same manner as a vehicle that can independently control the torque of each wheel in the prior art. Specifically, for example, it determines the distribution ratio of the torque transmitted to the front and rear wheels according to the required driving torque of the vehicle Ve, and determines the torques of the motors Mfr, Mfl, Mrr, and Mrl based on the torque distribution ratio. Further, when the vehicle Ve is turning, based on the signals detected by the wheel speed sensors and the steering angle sensors, it obtains the distribution ratio and torque difference of the torque transmitted to the left and right wheels, and determines the torques of the motors Mfr, Mfl, Mrr, and Mrl.

[0033] The center of gravity estimation unit 34 is configured to estimate at least the center of gravity position in the vehicle width direction among the three axial directions of the vehicle width direction, vehicle height direction, and front-rear direction. Specifically, it acquires the detection values of the pressure sensors 20 provided for each seat 21 and the detection values of the stroke sensors 30 provided for each suspension 25 (that is, the load acting on the suspension 25), and is configured to calculate and estimate the center of gravity position of the vehicle Ve from the mounting positions of the sensors 20 and 30 and their detection values. Alternatively, a center of gravity position map that defines the center of gravity positions corresponding to the positions where the occupants are seated, such as the center of gravity position when only the driver and the rear seat behind the driver are occupied, and the center of gravity position when only the driver, the passenger seat, and the rear seat behind the passenger seat are occupied, is stored in the center of gravity estimation unit 34, and the center of gravity position is estimated based on the signal indicating the presence or absence of seating input from the seating sensor (pressure sensor 20) provided for each seat 21. In that case, the center of gravity position map may be constructed assuming that occupants of a predetermined weight are seated without detecting the weight of the occupants.

[0034] Note that since the pressure sensors 20 provided on the seat 21 and the stroke sensors 30 provided on the suspension 25 detect the vertical load, if centrifugal force or inertial force acts on the object to be detected, it may not be possible to accurately detect the weight. Therefore, it is preferable that the center of gravity estimation unit 34 obtains the detection values of the pressure sensors 20 and the stroke sensors 30 when the vehicle Ve is stopped or when the vehicle Ve is traveling straight within a predetermined angle range of the steering angle, and estimates the center of gravity position.

[0035] When the center-of-gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 is offset in the vehicle-width direction from a predetermined center-of-gravity position (predetermined center-of-gravity position) due to the structure of the vehicle Ve as described above, the distance between the estimated center-of-gravity position and one driving wheel becomes shorter than the distance between the estimated center-of-gravity position and the other driving wheel. The yaw moment acting on the vehicle Ve is the magnitude obtained by multiplying the driving force by the distance between the position where the driving force is generated and the center-of-gravity position. Therefore, when the same torque is output from the left and right motors Mfr, Mfl (Mrr, Mrl), the yaw moment based on the driving force generated by the driving wheel on the side closer to the estimated center-of-gravity position becomes smaller than the yaw moment based on the driving force generated by the other driving wheel, and the vehicle Ve may deflect unintentionally.

[0036] Therefore, the torque correction unit 35 is configured to correct the reference torque set by the reference torque setting unit 33 based on the center-of-gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34. Specifically, the difference (distance) between the center-of-gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 and the center-of-gravity position predetermined based on the specifications of the vehicle Ve is obtained, and from the difference in the center-of-gravity position, a correction torque for canceling the yaw moment accompanying the change in the center-of-gravity position is obtained, and the correction torque is configured to be added to the reference torque. Therefore, the torque of the motor (for example, motor Mfr or motor Mrr) connected to the wheel on the side where the center-of-gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 approaches is increased, and the torque of the motor (for example, motor Mfl or motor Mrl) connected to the other wheel is decreased.

[0037] Fig. 7 shows a flowchart for explaining an example of the control executed by the above-described controller 31. In the control example shown in Fig. 7, first, it is determined whether or not the power switch for starting the vehicle Ve is on (step S1). If it is determined negatively in step S1 because the power switch is off, this routine is immediately terminated. On the contrary, if it is determined affirmatively in step S1 because the power switch is on, it is determined whether or not the vehicle has been switched from the parking range (P range) to the driving range (D range or R range) (step S2). This step S2 can be determined based on the switch signal of the shift lever operated by the driver to drive.

[0038] When the vehicle is still in the parking range or has been switched to the neutral range, etc., and the switch to the driving range has not been made, the vehicle Ve is less likely to start running immediately, and the center of gravity position of the vehicle Ve may change when getting in or loading. Therefore, if it is determined negatively in step S2, this routine is immediately terminated.

[0039] On the contrary, if it is determined affirmatively in step S2 that the vehicle has been switched from the parking range to the drive range (D range) or the reverse range (R range), the center of gravity position of the vehicle Ve is estimated (step S3). This step S3 is executed by the center of gravity estimation unit 34 described above and is estimated based on the detection signals of the pressure sensor 20 and the stroke sensor 30.

[0040] Next, the reference torques of the respective motors Mfr, Mfl, Mrr, and Mrl are set (step S4). This step S4 is executed by the reference torque setting unit 33. As described above, the required drive torque is obtained according to the vehicle speed and the accelerator opening degree, the distribution ratio of the torques of the front and rear wheels is determined according to the required drive torque, and further, the distribution ratio of the torques of the left and right in a pair of front wheels and the distribution ratio of the torques of the left and right in a pair of rear wheels are set based on the steering angle and the respective wheel speeds.

[0041] Then, the reference torque set in step S4 is corrected based on the center-of-gravity position estimated in step S3 (step S5), and this routine is terminated once. This step S5 is executed by the torque correction unit 35. That is, the difference (distance) between the center-of-gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 and the center-of-gravity position predetermined based on the specifications of the vehicle Ve is obtained, and from the difference in the center-of-gravity position, a correction torque for canceling the yaw moment accompanying the change in the center-of-gravity position is obtained, and the correction torque is added to the reference torque.

[0042] As described above, the center-of-gravity position is estimated from the detection values of the pressure sensor 20 provided on the seat 21 and the stroke sensor 30 provided on the suspension 25, and a correction torque for canceling the yaw moment is obtained based on the center-of-gravity position. Thus, it is possible to suppress the occurrence of an unintended yaw moment based on the seating position and weight of the occupant, or the loading position and weight of the load. As a result, the straight-ahead running performance, turning performance, or stability during braking can be improved. In other words, it is possible to suppress the deterioration of the operability during running. In particular, the load is not limited to the case where it is placed on the seat cushion 22, and may be placed under the feet of the rear seat, etc. Since the loading position is not determined and the weight varies, by estimating the center-of-gravity position based on the detection value of the stroke sensor 30, the error between the actual center-of-gravity position and the estimated center-of-gravity position can be reduced, and the accuracy of the correction torque can be improved.

[0043] Note that the left-right wheel independent drive type vehicle in the embodiment of the present invention is not limited to a vehicle equipped with two motors as the driving force sources for a pair of front wheels and two motors as the driving force sources for a pair of rear wheels, and may be a vehicle equipped with two motors as the driving force sources for either the front wheels or the rear wheels, and an engine or one motor as the driving force source for the other wheels. Even in such a case, by adding the correction torque to the reference torque of the pair of wheels having two motors as the driving force sources, it is possible to suppress the occurrence of a yaw moment accompanying the change in the center-of-gravity position.

Explanation of Signs

[0044] 1r, 1l Front wheels 2r, 2l Rear wheels 20 Pressure sensor 21 Seat 22 Seat cushion 25 Suspension 30 Stroke sensor 31 Controller 32 Driving torque setting unit 33 Reference torque setting unit 34 Center of gravity estimation unit 35 Torque correction unit Mfr, Mfl, Mrr, Mrl Motor Ve Four-wheel independent drive vehicle

Claims

1. A driving force control device for a left and right wheel independent drive type vehicle, comprising a left electric motor for driving a left wheel and a right electric motor for driving a right wheel paired with the left wheel, comprising a controller for controlling the left electric motor and the right electric motor, the controller comprises a center of gravity estimation unit for estimating the center of gravity position of the left and right wheel independent drive type vehicle, and a torque correction unit for adding a correction torque that cancels a yaw moment generated according to a difference between the estimated center of gravity position of the left and right wheel independent drive type vehicle estimated by the center of gravity estimation unit and a predetermined center of gravity position to the output torques of the left electric motor and the right electric motor. A driving force control device for a left and right wheel independent drive type vehicle, characterized by the above.

2. A driving force control device for a left and right wheel independent drive type vehicle according to Claim 1, further comprising a plurality of seats on which passengers sit and a plurality of seating sensors provided for each of the plurality of seats for detecting that the passengers are sitting, wherein the center of gravity estimation unit estimates the center of gravity position of the left and right wheel independent drive type vehicle based on the positions of the seating sensors that have detected that the passengers are sitting. A driving force control device for a left and right wheel independent drive type vehicle, characterized by the above.

3. A driving force control device for a left and right wheel independent drive type vehicle according to Claim 1, further comprising a plurality of suspensions that reciprocate in the vertical direction of the left and right wheel independent drive type vehicle to suppress the vertical vibration of each wheel, and stroke sensors provided for each of the plurality of suspensions for detecting the displacement amount of the suspension, wherein the center of gravity estimation unit estimates the center of gravity position of the left and right wheel independent drive type vehicle based on the displacement amounts of the plurality of suspensions detected by the stroke sensors. A driving force control device for a left and right wheel independent drive type vehicle, characterized by the above.

4. A driving force control device for a left and right wheel independent drive type vehicle according to any one of Claims 1 to 3, wherein the torque correction unit increases the torque of one of the left electric motor and the right electric motor connected to the wheel on the side where the estimated center of gravity position estimated by the center of gravity estimation unit of the left wheel and the right wheel is closer to the predetermined center of gravity position, and decreases the torque of the other of the left electric motor and the right electric motor. A driving force control device for a left and right wheel independent drive type vehicle, characterized by the above.

5. A driving force control device for a left and right wheel independent drive type vehicle according to Claim 1, The center-of-gravity estimation unit estimates the center-of-gravity position of the left-and-right wheel independently-driven vehicle when the left-and-right wheel independently-driven vehicle stops or when the left-and-right wheel independently-driven vehicle travels straight with a steering angle within a predetermined angle range. A driving force control device for a left-and-right wheel independently-driven vehicle, characterized by the above.

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