Patent Application
20250196658
This application claims priority to Japanese Patent Application No. 2023-213893 filed on Dec. 19, 2023, incorporated herein by reference in its entirety.
The present disclosure relates to a driving force control device for a vehicle configured to drive right and left wheels independently of each other.
Japanese Unexamined Patent Application Publication No. 2001-112114 (JP 2001-112114 A) describes a control device for a four-wheel drive vehicle that includes a front motor that serves as a drive force source for a pair of front wheels and a rear motor that serves as a drive force source for a pair of rear wheels. When the operation of the rear motor is limited according to the temperature of the rear motor or the temperature of a power storage device, the control device sets the output torque of the rear motor to limit torque determined based on the temperature of the rear motor. Then, torque corresponding to the limit torque of the rear motor is subtracted from the drive torque required for the vehicle. Further, the subtracted torque is set as the output torque of the front motor. The front motor and the front wheels are coupled via a differential gear mechanism, and similarly, the rear motor and the rear wheels are coupled via a differential gear mechanism.
In addition, WO 2021/220693 describes a control device for a vehicle that includes a pair of electric motors that drives right and left wheels and a differential mechanism that applies a torque difference to the right and left wheels. This control device is intended to improve the turning responsiveness of the vehicle body to steering. The control device is configured to output, from the electric motors, compensation torque for canceling a turning inhibition yaw moment generated by a difference between first inertial torque in a power transfer path from the electric motor to the right wheel and second inertial torque in a power transfer path from the electric motor to the left wheel. SUMMARY
In the four-wheel drive vehicle described in JP 2001-112114 A, the motors and the drive wheels are coupled via the differential mechanisms. When the position of the center of gravity of the vehicle as a whole changes according to the presence or absence of an occupant or a load, or the weight thereof, or the position thereof, the torque is split such that larger torque is transferred to the wheel whose ground contact load increases. On the other hand, the wheel to which such larger torque is transferred is closer to the center of gravity of the vehicle than the wheel on the other side. That is, even if the distance between the position of the center of gravity and the drive wheels changes with the change of the position of the center of gravity, the driving force mechanically changes according to the change of the distance. Thus, the 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 is suppressed, and deterioration of the traveling stability and the operability of the vehicle can be suppressed.
In contrast, in the case of a vehicle in which the right and left wheels are independently provided with motors, the same torque is output from the respective motors, and the same torque is transferred to the right and left drive wheels. Thus, when the position of the center of gravity of the vehicle as a whole changes, a change in the distance between the position of the center of gravity and the drive wheels due to the change in the position of the center of gravity 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. As a result, a yaw moment is generated so as to deflect the vehicle, and there is a possibility that the traveling stability and the operability of the vehicle deteriorate.
Further, according to the control device described in WO 2021/220693, compensation torque for canceling a turning inhibition yaw moment is obtained based on predetermined specifications of a power transfer path from an electric motor to a drive wheel, motors, tires, etc. However, the control device described in WO 2021/220693 does not consider that the position of the center of gravity of the entire vehicle changes according to an occupant or a load. Therefore, even if the compensating torque for canceling the turning inhibition yaw moment is output, a yaw moment is generated along with the change in the position of the center of gravity, and there is a possibility that the traveling stability and the operability of the vehicle deteriorate.
The present disclosure has been made in view of the above technical issue, and an object of the present disclosure is to provide a driving force control device for a right and left wheel independent drive type vehicle capable of suppressing the generation of a yaw moment due to a change in the position of the center of gravity of the vehicle.
In order to achieve the above object, an aspect of the present disclosure provides a driving force control device for a right and left wheel independent drive type vehicle, including: a right electric motor that drives a right wheel, and a left electric motor that drives a left wheel paired with the right wheel; and
In an aspect of the present disclosure, the driving force control device may further include a plurality of seats on which an occupant is to be seated, and a plurality of seating sensors provided for each of the seats to detect that the occupant is seated, and the center-of-gravity estimation unit may estimate the center-of-gravity position of the right and left wheel independent drive type vehicle based on a position of the seating sensor that detects that the occupant is seated.
In an aspect of the present disclosure, the driving force control device may further include a plurality of suspensions that reciprocates in an up-down direction of the right and left wheel independent drive type vehicle to suppress vibration of each of the wheels in the up-down direction, and a stroke sensor provided for each of the suspensions to detect a displacement amount of the suspension, and
In an aspect of the present disclosure, the torque correction unit may increase torque of one of the right electric motor and the left electric motor that is coupled to one of the right wheel and the left wheel on a side closer to the estimated center-of-gravity position estimated by the center-of-gravity estimation unit than the predetermined center-of-gravity position, and reduce torque of the other of the right electric motor and the left electric motor.
In an aspect of the present disclosure, the center-of-gravity estimation unit may estimate the center-of-gravity position of the right and left wheel independent drive type vehicle when the right and left wheel independent drive type vehicle is stopped or during straight travel in which a steering angle of the right and left wheel independent drive type vehicle is within a predetermined angle range.
According to the present disclosure, the center-of-gravity position of the right and left wheel independent drive type vehicle is estimated, and the correction torque for canceling the yaw moment is added to the output torque of the right electric motor and the left electric motor, the yaw moment being generated according to the difference between the estimated center-of-gravity position and the predetermined center-of-gravity position determined in advance. Therefore, even if the position of the center of gravity of the right and left wheel independent drive type vehicle as a whole changes based on the position or the weight of an occupant that rides in the right and left wheel independent drive type vehicle, or the loading position or the weight of a load, the yaw moment due to the change in the position of the center of gravity can be canceled, and the generation of an unintended yaw moment can be suppressed. As a result, it is possible to improve the straight traveling property, the turning traveling property, or the stability during braking. In other words, deterioration in the operability during traveling can be suppressed.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:
Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of the implementation of the present disclosure, and do not limit the present disclosure.
A vehicle according to the present disclosure is an electric motor (motor or motor generator) as a power source corresponding to a pair of left front wheels and right front wheels, or a pair of left rear wheels and right rear wheels. Hereinafter, it will be described as a motor. The present disclosure relates to a vehicle capable of independently driving a left wheel and a right wheel. The vehicle may be a total four-wheeled vehicle of a front two-wheeled and a rear two-wheeled vehicle. In this case, the vehicle may be a vehicle in which a driving device is provided on each of the front two wheels and the rear two wheels, and each of the front two wheels and the rear two wheels can be driven independently of each other. The motor may be provided on each of two wheels of either the front two wheels or the rear two wheels, and the other two wheels may be a vehicle connected to a single electric motor via a differential gear.
In the drive unit Pr of the rear wheel 2r, 2l, a motor Mrr, Mrl is mounted with its rotational center axial line facing the front-rear direction of the vehicle Ve. A drive gear 3rr, 3rl is attached to the rotor shaft, and the drive gear 3rr, 3rl meshes with the counter driven gear 4rr, 4rl. The counter driven gear 4rr, 4rl is larger in diameter than the drive gear 3rr, 3rl, and therefore these gear pairs constitute a reduction gear. A counter drive gear 5rr, 5rl which is a bevel gear is provided so as to rotate integrally on the same axis as the counter driven gear 4rr, 4rl. The counter drive gear 5rr, 5rl meshes with a driven gear 7rr, 7rl which is a bevel gear integral with a drive shaft 6rr, 6rl connected to the rear wheel 2r, 2l. By making the driven gear 7rr, 7rl larger in diameter than the counter drive gear 5rr, 5rl, the gear pair can be a reduction gear.
Since the counter driven gear 15fr, 15fl has a larger diameter than the drive gear 12fr, 12fl attached to the motor Mfr, Mrl, the gear pair constitutes a reduction gear. A counter drive gear 16fr, 16fl is attached to the counter shaft 14r, 141. The counter drive gear 16fr, 16fl meshes with a driven gear 18fr, 18fl integral with a drive shaft 17fr, 17fl coupled to the front wheel 1r, 1l. Since the driven gear 18fr, 18fl has a larger diameter than that of the counter drive gear 16fr, 16fl, the gear pair constitutes a reduction gear.
Note that the wheel 1l, 2l corresponds to the “left wheel” in the embodiment of the present disclosure, and the wheel 1r, 2r corresponds to the “right wheel” in the embodiment of the present disclosure. The motor Mfl, Mrl corresponds to the “left electric motor” in the embodiment of the present disclosure, and the motor Mfr, Mrr corresponds to the “right electric motor” in the embodiment of the present disclosure.
The vehicle Ve shown in
The vehicle Ve configured as described above can control the output torques of the motor Mfr, Mfl, Mrr, Mrl independently of each other. Therefore, for example, it is possible to switch between the two-wheel drive traveling mode in which the motor Mrr, Mrl is controlled as the driving force source and the energization of the motor Mfr, Mfl is stopped, and the four-wheel drive traveling mode in which the motor Mfr, Mfl, Mrr, Mrl are controlled as the driving force source. In addition, in order to improve the turning performance, when the two-wheel drive traveling mode or the four-wheel drive traveling mode is set, the right motor Mfr, Mrr and the left motor Mfl, Mrl can travel with different torques.
Further, in the above-described vehicle Ve, in order to determine the position of the center of gravity of the entire vehicle Ve, a pressure sensor is provided for each seat to detect whether or not the occupant is seated on any of the seats, and to detect the weight of the occupant seated on the seat or the load placed on the seat.
Further, in the above-described vehicle Ve, suspensions 25 for absorbing the vertical loads of the wheels are attached to the respective drive shaft 6rr, 6rl, 17fr, 17fl.
In addition, the vehicle Ve is provided with controllers (electronic control units) 31 for controlling the motor Mfr, Mfl, Mrr, Mrl. The controller 31 mainly includes a microcomputer. The controller 31 is configured to perform an operation according to a predetermined program or referring to a predetermined map using the input data and data stored in advance, and to output the result of the operation to the motor Mfr, Mfl, Mrr, Mrl as a control command signal.
An example of an input signal and an output signal for performing such control is shown in
Further, as shown in
Like the conventional vehicle, 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 operation amount detected by the accelerator operation amount sensor. 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 operation amount as parameters. The drive torque setting unit 32 is configured to acquire the vehicle speed signal of the vehicle speed sensor and the accelerator operation amount signal of the accelerator operation amount sensor, and to set the required driving torque of the vehicle Ve by referring to the driving torque map.
The reference torque setting unit 33 sets the torque of each motor Mfr, Mfl, Mrr, Mrl in the same manner as the conventional vehicles capable of independently controlling the torque of each wheel. Specifically, for example, the distribution ratio of the torque transmitted to the front and rear wheels is determined in accordance with the required drive torque of the vehicle Ve, and the torque of the motor Mfr, Mfl, Mrr, Mrl is determined based on the distribution ratio of the torque. In addition, when the vehicle Ve is traveling in a turning direction, the torque of the motor Mfr, Mfl, Mrr, Mrl is determined by determining the distribution ratio and the torque differential of the torque transmitted to the left and right wheels based on the signals detected by the wheel speed sensor and the steering angle sensor.
The center-of-gravity estimation unit 34 is configured to estimate a position of a center of gravity in at least the vehicle width direction among three axial directions in the vehicle width direction, the vehicle height direction, and the front-rear direction.
Specifically, the center-of-gravity estimation unit 34 is configured to acquire a detection value of the pressure sensor 20 provided for each seat 21 and a detection value of the stroke sensor 30 provided for each suspension 25 (that is, a load acting on the suspension 25), and the center-of-gravity estimation unit 34 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 the detection value thereof. Alternatively, the center-of-gravity estimation unit 34 is configured to store a center-of-gravity position map that defines a center-of-gravity position corresponding to a position where the occupant is seated, such as a center-of-gravity position when the occupant is seated only on the driver's seat and the rear seat, a center-of-gravity position when the occupant is seated only on the driver's seat, the passenger's seat, and the rear seat of the passenger's seat. The center-of-gravity estimation unit 34 is configured to estimate the position of the center of gravity based on a signal indicating the presence or absence of seating input from a seating sensor (pressure sensor 20) provided for each seat 21. In this case, the center-of-gravity position map may be constructed such that an occupant having a predetermined weight is seated without detecting the weight of the occupant.
Note that the pressure sensor 20 provided on the seat 21 and the stroke sensor 30 provided on the suspension 25 detect a load in the vertical direction, and therefore, if a centrifugal force or an inertial force acts on an object to be detected, there is a possibility that an accurate weight cannot be detected. Therefore, it is preferable that the center-of-gravity estimation unit 34 estimates the position of the center of gravity by acquiring the detected values of the pressure sensor 20 and the stroke sensor 30 when the vehicle Ve is stopped or when the steering angle of the vehicle Ve is straight traveling within a predetermined angular range.
As described above, when the position of the center of gravity of the vehicle Ve estimated by the center-of-gravity estimation unit 34 is deviated in the vehicle width direction from the predetermined position of the center of gravity (predetermined position of the center of gravity) due to the construction of the vehicle Ve, the distance between the estimated center of gravity position and one of the drive wheels is shorter than the distance between the estimated center of gravity position and the other of the drive wheels. The yaw moment acting on the vehicle Ve is a magnitude obtained by multiplying the driving force by the distance between the position where the driving force is generated and the position of the center of gravity. Therefore, when the same torque is outputted from the left and right motor Mfr, Mfl (Mrr, Mrl), there is a possibility that the yaw moment based on the driving force generated by the driving wheels on the side close to the estimated center of gravity position becomes smaller than the yaw moment based on the driving force generated by the driving wheels on the other side, and consequently, there is a possibility that Ve of vehicles is unintentionally deflected.
Therefore, the torque correction unit 35 is configured to correct the reference torque set by the reference torque setting unit 33 based on the position of the center of gravity of the vehicle Ve estimated by the center-of-gravity estimation unit 34. Specifically, the torque correction unit 35 is configured to obtain a difference (distance) between the center of gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 and a predetermined center of gravity position based on the specifications of the vehicle Ve. The torque correction unit 35 obtains a correction torque for canceling a yaw moment caused by a change in the position of the center of gravity from a difference in the position of the center of gravity, and adds the correction torque to the reference torque. Therefore, the torque of the motor (for example, the motor Mfr or the 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, the motor Mfl or the motor Mrl) connected to the wheel on the other side is decreased.
When the vehicle is not switched to the driving range, for example, when the vehicle is in the parking range or when the vehicle is switched to the neutral range, there is a low possibility that the vehicle Ve starts traveling immediately, and there is a possibility that the position of the center of gravity of the vehicle Ve changes due to riding or loading. Therefore, if a negative determination is made in S2, the routine is terminated once.
On the contrary, when the driving range is changed from the parking range to the driving range (D range) or the reverse range (R range) and a positive determination is made on S2, the position of the center of gravity of the vehicle Ve is estimated (S3). This S3 is executed by the center-of-gravity estimation unit 34 described above, and is estimated based on the sensing signals of the pressure sensor 20 and the stroke sensor 30.
Then, the reference torque of the motor Mfr, Mfl, Mrr, Mrl is set (S4). This S4 is executed by the reference torque setting unit 33. As described above, the reference torque setting unit 33 obtains the required driving torque according to the vehicle speed and the accelerator operation amount, determines the distribution ratio of the torque of the front and rear wheels according to the required driving torque, and further sets the distribution ratio of the left and right torques of the pair of front wheels and the distribution ratio of the left and right torques of the pair of rear wheels based on the steering angle and each wheel speed.
Then, the reference torque set by S4 is corrected based on the position of the center of gravity estimated by S3 (S5), and the routine is terminated once. This S5 is executed by the torque correction unit 35. That is, the torque correction unit 35 obtains a difference (distance) between the center of gravity position of the vehicle Ve estimated by the center-of-gravity estimation unit 34 and a predetermined center of gravity position based on the specifications of the vehicle Ve. Then, the torque correction unit 35 obtains a correction torque for canceling the yaw moment caused by the change in the position of the center of gravity from the difference in the position of the center of gravity, and adds the correction torque to the reference torque.
As described above, the position of the center of gravity 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 the correction torque for canceling the yaw moment is obtained based on the position of the center of gravity. Accordingly, it is possible to suppress the occurrence of an unintended yaw moment based on the occupant's riding position, the weight thereof, the loading position of the load, and the weight thereof. As a result, it is possible to improve the straight traveling property, the turning traveling property, or the stability at the time of braking. In other words, deterioration in operability during traveling can be suppressed. In particular, the load is not limited to the case where the load is placed on the seat cushion 22, and the load position is not fixed, such as the case where the load is placed under the foot of the rear seat, and the weight thereof is varied. Therefore, by estimating the position of the center of gravity based on the detection value of the stroke sensor 30, an error between the actual position of the center of gravity and the estimated position of the center of gravity can be reduced, and the accuracy of the correction torque can be improved.
Note that the right and left wheel independent drive type vehicle according to the embodiment of the present disclosure is not limited to a vehicle including two motors as driving force sources of a pair of front wheels and two motors as driving force sources of a pair of rear wheels, and may be a vehicle including two motors as driving force sources of either one of the front wheels and the rear wheels, and including an engine and one motor as driving force sources of the other wheel. Even in such a case, by adding the correction torque to the reference torque of the pair of wheels using the two motors as the driving force sources, it is possible to suppress the occurrence of the yaw moment caused by the change in the position of the center of gravity.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-213893 | Dec 2023 | JP | national |
