Vehicle control device and vehicle control method

Abstract

Provided is a vehicle control device that makes it possible to improve vehicle stability by promptly suppressing an initial slip. The vehicle control device comprises control unit for controlling: a friction brake actuator that applies a friction braking force to each wheel by pressing a friction pad against a rotor that rotates together with each wheel; and an in-wheel motor (IWM) that applies a braking / driving force to each wheel. The control unit: acquires a requested braking force to apply to each wheel; drives the friction brake actuator on the basis of the requested braking forces; acquires a slip ratio of each wheel when decelerating the vehicle; and, when applying a driving force via the IWM to a slip wheel which, among the wheels, has a slip ratio exceeding a prescribed threshold value, controls the driving force on the basis of the magnitude of the friction braking force and the rate of change of the friction braking force.

Description

Vehicle control device and vehicle control method

[0001] The present invention relates to a vehicle control device and a vehicle control method for recovering a vehicle from a slip, and more particularly to a device and a method for recovering a vehicle from a slip, the device and method including a braking / driving electric motor mounted on each wheel and braking by pressing brake pads, the position of which is adjusted by a friction braking electric motor, against brake rotors that rotate together with the wheels.

[0002] Patent Document 1 describes an electric vehicle that has a drive motor for each wheel and performs regenerative braking and friction braking. In this patent document 1, if it is determined that a wheel is tending to lock during friction braking, a braking control device controls the torque of the drive motor to suppress wheel slip.

[0003] Japanese Patent Application Publication No. 5-270387

[0004] However, because the braking technology of Patent Document 1 is basically feedback (FB) control, it is difficult to improve responsiveness to initial slip, and there is a concern that the initial slip may become large. To strongly suppress the initial slip, a high-gain feedback (Hi-Gain-FB) control system can be used, but high-gain feedback tends to make the control unstable, and there is a possibility that the initial slip may not be suppressed effectively.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a vehicle control device and a vehicle control method that can improve vehicle stability by quickly suppressing initial slip.

[0006] According to one aspect of the present invention, there is provided a vehicle control device including a control unit that acquires a required braking force to be applied to each wheel, drives a friction braking electric motor based on the required braking force, acquires a slip ratio of each wheel when decelerating the vehicle, and controls the driving force based on the magnitude of the friction braking force and the rate of change of the friction braking force when applying driving force by the braking / driving electric motor to a slipping wheel among the wheels whose slip ratio exceeds a predetermined threshold. According to another aspect of the present invention, there is provided a vehicle control method that, when applying driving force by the braking / driving electric motor during deceleration of the vehicle by driving the friction braking electric motor, makes the driving force larger when the rotational speed of the friction braking electric motor is 20% of the maximum output of the friction braking electric motor than when it is zero.

[0007] In the vehicle control device and vehicle control method of the present invention, the electric motor for braking / driving the slipping wheel applies a driving force to the slipping wheel based on the magnitude and rate of change of the frictional braking force, and the braking force applied to the slipping wheel is reduced quickly at the beginning of slippage, thereby helping to suppress initial slippage, thereby quickly suppressing initial slippage and improving vehicle stability.

[0008] 4 is a schematic configuration diagram of an electric vehicle equipped with a vehicle control device according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing an example of the configuration of the brake system in FIG. 1. FIG. 2A is a timing chart for explaining brake operation, motor rotation speed, and pad position in the brake system in FIG. 2A. FIG. 2B is a block diagram showing a part of the example of the configuration of the vehicle control device according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the remaining parts of the vehicle control device according to the first embodiment of the present invention. FIG. 4 is a control block diagram showing an example of the configuration of the slip determination unit in FIG. 3. FIG. 4 is a control block diagram showing an example of the configuration of the FF driving force reset determination unit in FIG. 3. FIG. 4 is a control block diagram showing an example of the configuration of the FF driving force holding unit in FIG. 3. FIG. 4 is a control block diagram showing an example of the configuration of the motor braking / driving force output selection unit in FIG. 4. FIG. 4 is a control block diagram showing an example of the configuration of the motor braking / driving force output setting unit in FIG. 4. FIG. 4 is a control block diagram showing an example of the configuration of the motor braking / driving force recovery determination unit in FIG. 4. FIG. 4 is a control block diagram showing an example of the configuration of the rate limiter during braking force recovery in FIG. 4. FIG. 4 is a control block diagram showing an example of the configuration of the reduction request value rate limiter in FIG. 4. FIG. 4 is a diagram for explaining a gain map based on the rotation speed of the brake motor in FIG. 3. FIG. 4 is a diagram for explaining a gain map based on the slip ratio change rate in FIG. 3. FIG. 4 is a diagram for explaining the FF driving force reduction gain map in FIG. 3. FIG. 5 is a diagram for explaining the gain map based on the state after slip determination in FIG. 4. FIG. 6 is a timing chart showing the basic operation during slip in the vehicle control device shown in FIGS. 3 and 4. FIG. 7 is a timing chart showing the operation when the gain map based on the state after slip determination is used in the vehicle control device shown in FIGS. 3 and 4. FIG. 8 is a timing chart showing the operation when the predetermined time is set to "0" when the slip ratio change rate is fast in the gain map based on the state after slip determination in FIG. 4. FIG. 9 is a timing chart showing the operation when the slip ratio increases again while it is decreasing. FIG. 10 is a block diagram showing a part of an example configuration of a vehicle control device according to a second embodiment of the present invention. FIG. 11 is a block diagram showing the remaining parts of the vehicle control device according to the second embodiment of the present invention.22 is a diagram for explaining a gain map based on the slip ratio change rate and pad position in FIG. 21. FIG. 23 is a block diagram showing a part of an example configuration of a vehicle control device according to a third embodiment of the present invention. FIG. 24 is a block diagram showing the remaining part of the vehicle control device according to the third embodiment of the present invention. FIG. 25 is a diagram for explaining a gain map based on the amount of change in a reduction request value in FIG. 24.

[0009] 1 shows a schematic configuration of an electric vehicle equipped with a vehicle control device according to an embodiment of the present invention. ＦＬ , 11 ＦＲ and rear wheel 11 ＲＬ , 11 ＲＲ And these front wheels 11 ＦＬ , 11 ＦＲ and rear wheel 11 ＲＬ , 11 ＲＲ an in-wheel motor (abbreviated as IWM) 12 that outputs torque to ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ These IWM12 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ is an electric motor for braking and driving the electric vehicle 10. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ Each of the motors has an IWM resolver 13 for detecting the motor rotation speed. ＦＬ , 13 ＦＲ , 13 ＲＬ , 13 ＲＲ The front wheels 11 are installed. ＦＬ , 11 ＦＲ and rear wheel 11 ＲＬ , 11 ＲＲ These are collectively referred to as wheels, wheels, or drive wheels.

[0010] The electric vehicle 10 also includes a friction brake actuator (friction braking electric motor) 14 provided on each wheel to generate a friction braking force on the wheel. ＦＬ , 14 ＦＲ , 14 ＲＬ , 14ＲＲ Friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ The wheels 11 of the electric vehicle 10 are driven by the ＦＬ , 11 ＦＲ , 11 ＲＬ , 11 ＲＲ Brake rotor (rotor) 28 rotating with ＦＬ , 28 ＦＲ , 28 ＲＬ , 28 ＲＲ By pressing a friction pad against each wheel 11 ＦＬ , 11 ＦＲ , 11 ＲＬ , 11 ＲＲ The friction brake actuator 14 applies a friction braking force to the ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ , brake rotor 28 ＦＬ , 28 ＦＲ , 28 ＲＬ , 28 ＲＲ The friction braking device is made up of the friction pads and the like. ＦＬ , 11 ＦＲ , 11 ＲＬ , 11 ＲＲ Each of the wheels has a wheel speed sensor 15 for detecting the wheel speed. ＦＬ , 15 ＦＲ , 15 ＲＬ , 15 ＲＲ Furthermore, the electric vehicle 10 is provided with an acceleration sensor 16 near the center of gravity of the vehicle, which detects the acceleration of the vehicle.

[0011] The electric vehicle 10 includes a low-voltage battery 17 used for various on-board devices, and an IWM 12 which is an electric motor for braking and driving. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ The vehicle is equipped with a high-voltage battery 18 used for the above-mentioned purposes. The low-voltage battery 17 is, for example, a lead-acid battery. The high-voltage battery 18 is, for example, a lithium-ion battery or a nickel-metal hydride battery. The high-voltage battery 18 is charged with a voltage boosted by a DC-DC converter 19.

[0012] The electric vehicle 10 includes a vehicle control device 20, a brake control device 21, an IWM control device 22, and other electronic control devices that control the vehicle. ＦＬ , 22 ＦＲ , 22 ＲＬ , 22 ＲＲ and a battery control device 23. The control devices share information with each other via an in-vehicle communication line (CAN bus) 24 indicated by hatching.

[0013] The vehicle control device 20 includes an IWM resolver 13 that detects the motor rotation speed. ＦＬ , 13 ＦＲ , 13 ＲＬ , 13 ＲＲ The vehicle control device 20 acquires information from various sensors, such as an accelerator pedal sensor 25 that detects an accelerator operation amount, a brake pedal sensor 26 that detects a brake operation amount, and a gear position sensor 27, and performs integrated control of the electric vehicle 10 based on this information. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ The torque requested by the driver is output.

[0014] The brake control device 21 is connected to the acceleration sensor 16 and the wheel speed sensor 15. ＦＬ , 15 ＦＲ , 15 ＲＬ , 15 ＲＲ and information from a brake pedal sensor 26 via the CAN bus 24. Then, based on the driver's brake operation, the friction braking electric motor (friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ) and adjusts the brake pad position by the electric motor, thereby generating a friction braking force. The magnitude of the friction braking force is calculated based on physical quantities related to a reference braking force based on the required braking force (the position of the brake pad, the current value of the electric motor for friction braking, the friction braking torque or the required value for reducing the ABS braking force). The rate of change in the friction braking force is calculated based on physical quantities related to the rotation speed of the electric motor for friction braking. Furthermore, when the brake pedal is depressed, the friction braking torque is calculated based on the physical quantities related to the rotation speed of the electric motor for friction braking. ＦＬ , 11 ＦＲ , 11 ＲＬ , 11 ＲＲ When a wheel slips, the braking force of the wheel in the slipping state is adjusted to increase or decrease the braking force (so-called ABS operation) so as to recover from the slip.

[0015] The battery control device 23 monitors the charge / discharge state of the high-voltage battery 18 and the single battery cells that make up the high-voltage battery 18. The battery control device 23 calculates a battery required torque limit value based on the charge / discharge state of the high-voltage battery 18. The battery required torque limit value is calculated by the IWM 12. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ For example, when the charge level of the high-voltage battery 18 is low, the battery torque limit value is set to a value smaller than normal. ＦＬ , 22 ＦＲ , 22 ＲＬ , 22 ＲＲ is set based on the IWM request torque. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ Control the power supplied to

[0016] 2A is a schematic diagram showing an example of the configuration of the brake system in FIG. 1. In this example, the friction braking device is an electric caliper brake, which presses brake pads (friction pads) 14c against a brake rotor (rotor) 28 via a ball screw mechanism 14b that converts the rotation of a brake motor (friction braking electric motor) 14a into linear motion. The brake rotor 28 rotates integrally with each wheel, and braking force is generated by frictional force when the brake pads 14c are pressed in the rotational axis direction of each wheel, as indicated by the arrow. The brake motor 14a is provided with a brake motor resolver 14d that detects the motor rotation speed.

[0017] 2B is a timing chart illustrating the brake operation, motor rotational speed, and pad position in the brake system of FIG. 2A. When the driver applies the brakes (time t0), the rotational speed of the brake motor 14a increases according to the amount of brake operation, and the ball screw mechanism 14b converts the rotational motion of the brake motor 14a into linear motion, causing the brake pads 14c to approach the brake rotor 28 (time t1). Between times t1 and t2, if the brake pedal is applied with a constant depression force, the motor rotational speed continues to increase, and the brake pads 14c are pressed against the brake rotor 28.

[0018] At time t2, when the driver releases the brake pedal pressure to a certain level, the motor rotation speed decreases, and at time t3, the motor rotation speed becomes negative, i.e., reverse, and then becomes constant. The position of the brake pads 14c continues to be pressed against the brake rotor 28 even after the brake is released, and the motor rotates in the reverse direction, thereby loosening the brake force. Therefore, the period from time t2 to t3 indicated by arrow AA is a delay time during which the braking force is not weakened.

[0019] 3 and 4 are block diagrams showing an example of the configuration of a vehicle control device according to a first embodiment of the present invention. ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ(Electric motor for braking and driving) and friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ The control section of the electric motor for friction braking is shown.

[0020] In the first embodiment, each wheel 11 ＦＬ , 11 ＦＲ , 11 ＲＬ , 11 ＲＲ IWM12 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ , and friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ A driver's request command value for the braking / driving electric motor is a command value generated for each IWM. ＦＲ If the right front wheel slips, the IWM12 ＦＲ and the right front wheel friction brake actuator 14 ＦＲ Control is performed on the combination of

[0021] The control section of the vehicle control device 20 is configured to receive inputs such as the brake pad position (or brake motor current value), the brake motor rotation speed, slip ratio change rate, the braking force requirement value for the brakes calculated from the brake operation amount in the brake control device 21, the ABS braking force reduction requirement value calculated in the brake control device 21 when there is a slip, and a driver-requested command value for the braking / driving electric motor determined based on the vehicle speed and the driver's accelerator pedal operation amount, and to output a motor braking / driving force recovery determination flag, the final ABS braking force reduction requirement value, and the final braking / driving force command value for the motor.

[0022] The positions of the brake pads (or the current value of the brake motor) are input to a base braking force map 40. The base braking force map 40 is a map that converts physical quantities related to the positions of the pads moved by the brake motor (friction brake actuator) and the current of the brake motor into a braking force reference value. Note that, instead of performing conversion using the base braking force map 40, a configuration may be adopted in which the braking force calculated by measuring the pressing pressure of the brake pads, etc. is used, or a configuration may be adopted in which the braking force requirement value for the brakes calculated by the brake control device 21 is used as is.

[0023] The rotational speed of the brake motor is input to a gain map 41 based on the rotational speed of the brake motor. The gain map 41 is a map that calculates a larger gain as the rotational speed of the brake motor increases. The slip ratio change rate is input to a gain map 42 based on the slip ratio change rate. The slip ratio change rate is obtained by differentiating the slip ratio and is used to determine whether the braking / driving force generated at each wheel significantly deviates from the braking force that can be generated on the road surface on which the vehicle is traveling. This gain map 42 is a map that calculates a larger gain as the slip ratio change rate increases in the direction in which the slip ratio increases. Then, a reference braking force is output from the base braking force map 40, a gain based on the rotational speed of the brake motor is output from the gain map 41, and a gain based on the slip ratio change rate is output from the gain map 42.

[0024] The reference braking force output from base braking force map 40 is multiplied by a gain output from gain map 41 in multiplication unit 43, and input to motor braking / driving force recovery determination unit 50. The result of this multiplication by multiplication unit 43 is multiplied by a gain output from gain map 42 in multiplication unit 44, and the result is input as FF driving force to FF driving force holding unit 45. FF driving force holding unit 45 holds the FF driving force when the slip ratio becomes equal to or greater than the slip determination threshold (when it is determined that slip has occurred), or the FF driving force when FF driving force reset determination unit 47 determines to reset it.

[0025] The slip ratio is input to the slip determination unit 46. The slip ratio during vehicle deceleration is calculated based on the following formula. Here, Si is the slip ratio of each wheel, V is the vehicle speed, vi is each wheel speed, and i is the number of each wheel (i = 1, ..., 4). In the above formula, the closer the slip ratio Si is to "1," the higher the possibility that the wheel is locked, and the smaller Si is, the lower the possibility that the wheel is locked. The vehicle speed may be obtained by a sensor, or may be estimated using the wheel speed or motor speed.

[0026] The slip determination unit 46 determines whether or not each wheel is slipping. If the slip ratio calculated from the vehicle speed and each wheel speed exceeds a slip determination threshold for any wheel, it is determined that the wheel is slipping. If the slip ratio is equal to or less than a non-slip determination threshold, it is determined that the wheel is not slipping. The output of the slip determination unit 46 is input to an FF driving force reset determination unit 47, an FF driving force holding unit 45, a gain map 51 based on the state after slip determination, and a motor braking / driving force recovery determination unit 50.

[0027] The slip ratio change rate is input to the FF driving force reset determination unit 47, and its output is output to the FF driving force holding unit 45. This FF driving force reset determination unit 47 sets an FF driving force reset determination flag if, during slip determination by the slip determination unit 46, the slip ratio change rate becomes equal to or less than the slip ratio decrease determination threshold and then becomes equal to or greater than the slip ratio increase determination threshold.

[0028] The slip ratio change rate and slip ratio are input to an FF driving force reduction gain map 48, and the output of this gain map 48 is multiplied by the driving force held in the FF driving force holding unit 45 in a multiplication unit 49 to generate an increased driving force reference value. When it is determined that the vehicle is tending to recover from slip based on the slip ratio and the slip ratio change rate, the gain map 48 outputs a gain that reduces the driving force held in the FF driving force holding unit 45.

[0029] The driver's requested command value for the braking / driving electric motor is input to a selector 57, a motor braking / driving force output selection unit 59, and a motor braking / driving force output setting unit 60. The selector 57 adds a driving force to the driver's requested command value to cancel out the regenerative braking force, thereby limiting the driving force to zero ("0") so that the driving force does not become excessively large compared to the driving force held by the FF driving force holding unit 45. A deviation calculation unit 58 calculates a driving force increase command value from the deviation between the increased driving force reference value and the driver's requested command value. While the limit is set to zero in this embodiment, if it is expected that the slip ratio will increase based on the slip ratio or the slip ratio change rate, for example, a driving force to cancel out the regenerative braking force may be added to more quickly suppress initial slip. The calculated driving force increase command value is input to the motor braking / driving force output selection unit 59 and the motor braking / driving force output setting unit 60. The motor braking / driving force output selection unit 59 also receives the motor braking / driving force recovery judgment flag output from the motor braking / driving force recovery judgment unit 50, and the output of this output selection unit 59 is input to the motor braking / driving force output setting unit 60, the rate limit unit 52 for braking force recovery, and the reduction request value rate limit unit 54.

[0030] When the motor braking / driving force return determination unit 50 determines that the return of the motor braking / driving force is permitted, the motor braking / driving force output selection unit 59 determines to output a driver's requested command value to the braking / driving electric motor. Furthermore, when the return of the motor braking / driving force is not permitted, the motor braking / driving force output selection unit 59 selects to output the sum if the sum of the driving force increase command value and the driver's requested command value to the braking / driving electric motor is greater than "0", and to output "0" if the sum is equal to or less than "0". Here, the output selection flag is set with the sum value being "0" as the threshold value, but the threshold value may be other than "0". The motor braking / driving force output setting unit 60 determines the torque set by the output setting unit 60 based on the selection value output from the output selection unit 59, and outputs the torque set by the output setting unit 60 to the braking / driving electric motor (IWM12 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ ) as the final braking / driving force command value.

[0031] As described above, the motor braking / driving force return determination unit 50 receives the reference braking force output from the base braking force map 40 and the output of the slip determination unit 46, as well as the brake braking force request value and the ABS braking force reduction request value (negative value). Based on the reference braking force, the brake braking force request value, the ABS braking force reduction request value, and the output of the slip determination unit, the motor braking / driving force return determination unit 50 executes a motor braking / driving force return permission determination if slip is not determined, the reference braking force is equal to the brake braking force request value, and the ABS braking force reduction request value is equal to or greater than a specified value. That is, the motor braking / driving force return determination unit 50 executes a motor braking / driving force return permission determination if either the brake braking force request value and the reference braking force are equal and the slip determination unit 46 has not determined slip, or the brake braking force request value and the reference braking force are equal and the ABS braking force reduction request value is equal to or greater than a specified value is satisfied. The motor braking / driving force return determination unit 50 then sets a motor braking / driving force return determination flag.

[0032] The slip ratio change rate and the output of the slip determination unit 46 are input to a gain map 51 based on the state after slip determination. This gain map 51 calculates a gain smaller than "1" when it is determined that recovery from slip has not been sufficient even after a predetermined time has passed, based on the time elapsed since slip was determined by the slip determination unit 46 and the slip ratio change rate. Then, the gain map 51 helps the vehicle to quickly recover from slip by weakening the braking force so that the relationship "driving force of the braking / driving electric motor ≧ brake braking force" holds.

[0033] The braking force recovery rate limiter 52 receives an increased driving force reference value. When the vehicle is recovering from a slip, the driving force increase command value approaches "0," and both the motor braking force and the brake braking force return to the values ​​requested by the driver. However, if the motor braking force and the brake braking force are returned to the values ​​requested by the driver at the same time, the braking force may return abruptly, causing the vehicle to slip again.

[0034] Therefore, in order to first reduce the motor braking / driving force to "0" and then increase the brake braking force, the rate of reduction of the increased driving force reference value output to the brake braking force side is changed based on whether the output of the motor braking / driving force output setting unit is "0" (or it may be set to a specified value or less instead of "0"), thereby achieving the above-mentioned operation.

[0035] The output of the gain map 51 and the output of the rate limiter 52 are input to the multiplier 53 and multiplied together. The ABS braking force reduction request value and the output of the motor braking / driving force output selector 59 are input to the reduction request value rate limiter 54. The output of the multiplier 53 and the output of the reduction request value rate limiter 54 are added by an adder 55 and input to a selector 56. The selector 56 limits the final ABS braking force reduction request value to "0" so that it does not become a positive value, and outputs the final ABS braking force reduction request value.

[0036] The ABS braking force reduction request value is not a requested reduction from the braking force currently applied by the brakes, but a signal indicating a reduction from the braking force requested by the driver. This signal is configured as a negative value, but if it is a positive value, it may be configured to be implemented based on that. Also, a pressure sensor may be attached to the brake pad, and a differential value of the pressure sensor may be used instead of the rotation speed of the brake motor.

[0037] Next, an example of the configuration of each block in Figures 3 and 4 will be described in detail. [Slip Determination Unit] Figure 5 is a control block diagram showing an example of the configuration of the slip determination unit 46 in Figure 3. The slip determination unit 46 determines whether or not each wheel is slipping. If the slip rate of any wheel calculated from the vehicle speed and each wheel speed is greater than or equal to a slip determination threshold, it is determined that the wheel is slipping, and a slip determination flag is set to "1". On the other hand, if the slip rate is less than or equal to the non-slip determination threshold, it is determined that the wheel is not slipping, and a slip determination flag is set to "0".

[0038] [FF Driving Force Reset Determination Unit] Figure 6 is a control block diagram showing an example of the configuration of the FF driving force reset determination unit 47 in Figure 3. The FF driving force reset determination unit 47 sets an FF driving force reset determination flag when, during slip determination, the slip ratio change rate becomes equal to or less than the slip ratio decrease determination threshold and then equal to or greater than the slip ratio increase determination threshold. That is, when the slip ratio change rate becomes smaller than or equal to the slip ratio decrease determination threshold, it is determined that the slip ratio has decreased, and the flag is set to "0." On the other hand, when the slip ratio change rate becomes larger than or equal to the slip ratio increase determination threshold, it is determined that the slip ratio has increased, and the flag is set to "1."

[0039] If the slip ratio has decreased and begun to return to normal, then increases again to "1," torque resetting is required. Therefore, if the previous value flag was "0" and the slip ratio change rate increases, the flag becomes "1," and the slip determination flag also becomes "1," the FF driving force reset determination flag is set to "1" and a reset request is made. If at least one of the conditions is not met, the FF driving force reset determination flag is set to "0," and no reset request is made.

[0040] [FF Driving Force Holding Unit] Figure 7 is a control block diagram showing an example of the configuration of the FF driving force holding unit 45 in Figure 3. The FF driving force holding unit 45 holds the FF driving force when the slip determination unit 46 determines that a slip has occurred or when the FF driving force reset determination unit 47 determines that the FF driving force has been reset. That is, when the slip determination flag is "1" and the previous slip determination flag is "0," a logical product is established, and the FF driving force is output as the FF driving force hold value. Similarly, when the FF driving force reset determination flag is "1," the FF driving force is output as the FF driving force hold value. When the logical product on the slip determination flag side is not established and the FF driving force reset determination flag is "0," the previous value is output as the FF driving force hold value.

[0041] [Motor braking / driving force output selection unit] Figure 8 is a control block diagram showing an example of the configuration of motor braking / driving force output selection unit 59 in Figure 4. Motor braking / driving force output selection unit 59 selects whether to output a driver-requested torque command value, a sum of the FF torque and the driver-requested torque command value, or "0" based on the determination result (motor braking / driving force return determination flag) of motor braking / driving force return determination unit 50, the drive force increase command value, and the driver-requested command value to the braking / driving electric motor.

[0042] When the motor braking / driving force return determination unit 50 determines that return is permitted, the driver's requested torque command value is output to the braking / driving electric motor. When the motor braking / driving force return determination unit 50 does not determine that return is permitted and the sum of the motor braking / driving force increase command value and the driver's requested command value for the braking / driving electric motor is greater than "0", the sum of the driving force increase command value and the driver's requested command value for the braking / driving electric motor is output. On the other hand, when the sum of the driving force increase command value and the driver's requested command value for the braking / driving electric motor is less than or equal to "0", the output is set to "0".

[0043] As a result, when the motor braking / driving force return determination flag is "1", the motor braking / driving force output selection flag becomes "1". When the motor braking / driving force return determination flag is "0", if the sum of the driving force increase command value and the driver request command value for the braking / driving electric motor is greater than "0", the motor braking / driving force output selection flag is set to "2", and if the sum is less than or equal to "0", the motor braking / driving force output selection flag is set to "3". The motor braking / driving force output selection flag is "2" when driving torque continues to be output during slipping, and the motor braking / driving force output selection flag is "3" when driving torque is held at "0" to wait for the brakes to return.

[0044] [Motor braking / driving force output setting unit] Figure 9 is a control block diagram showing an example of the configuration of motor braking / driving force output setting unit 60 in Figure 4. Motor braking / driving force output setting unit 60 sets a driver's requested command value to the braking / driving electric motor, a sum of the driver's requested command value and a driving force increase command value to the braking / driving electric motor, or "0" based on the motor braking / driving force output selection flag being "1," "2," or "3," and outputs final braking / driving force command values ​​to the braking / driving electric motor.

[0045] [Motor braking / driving force return determination unit] Figure 10 is a control block diagram showing an example of the configuration of motor braking / driving force return determination unit 50 in Figure 4. When the braking force requested by the driver to the brake is equal to the reference braking force and slip determination unit 46 has not determined that slip has occurred (the slip determination flag is "0"), or when the braking force requested by the brake is equal to the reference braking force and the ABS braking force reduction request value is equal to or greater than a specified value, the motor braking / driving force return determination unit 50 determines that motor braking / driving force return is permitted and sets a flag (motor braking / driving force return determination flag).

[0046] [Rate Limiting Unit During Braking Force Recovery] Figure 11 is a control block diagram showing an example of the configuration of rate limiting unit 52 during braking force recovery in Figure 4. When the flag of motor braking / driving force output selection unit 59 is set to "3" and the braking / driving force is set to "0," that is, at the timing when it is considered appropriate to return the braking force to the driver's request, the rate limiting unit changes from specified rate 2 to specified rate 1, thereby quickly restoring the braking force. Here, specified rate 2 is "0" or a very small negative value, and specified rate 1 is a larger negative value than specified rate 2 (for example, specified rate 2 is -5 and specified rate 1 is -100, with specified rate 1 being a larger negative value).

[0047] When the final braking / driving force command value to the motor is a positive command during slip determination, a specified rate 2 is used that is set to a small negative value or "0" to prevent the braking force from quickly approaching the braking force requested by the driver, so that the timing of the decrease in braking / driving force by the motor and the increase in braking force do not coincide.

[0048] On the other hand, when the motor torque output is held at "0", it is necessary to quickly restore the braking force to the braking force requested by the driver, so a large negative value of regulated rate 1 is used. This staggers the timing of the increase in braking force and the decrease in braking / driving force by the motor, making it possible to always respond to changes in the road surface, etc.

[0049] 12 is a control block diagram showing an example of the configuration of the reduction request value rate limiter 54 in FIG. 4. The rate limiter 52 reduces the motor braking / driving force when the braking force is restored, thereby preventing an increase in the frictional braking force at the same time. However, this logic alone cannot prevent the frictional braking force from increasing in the direction approaching the driver-requested braking force due to a decrease in the ABS braking force reduction request value itself.

[0050] Therefore, when the flag of motor braking / driving force output selection unit 59 is set to set the braking / driving force to "0," that is, when the ABS braking force reduction request value decreases at the timing when it is considered appropriate to return the braking force to the driver-requested braking force, the brake braking force is quickly restored by changing from specified rate 4 to specified rate 3. Here, specified rate 4 is "0" or a very small set positive value, and specified rate 3 is a larger set positive value than specified rate 4 (for example, specified rate 4 is +5, specified rate 3 is +100, and specified rate 3 is a larger negative value).

[0051] When the final braking / driving force command value to the motor is a positive command during slip determination, a regulation rate 4 set to a small positive value or "0" is used to prevent the brake braking force from quickly approaching the braking force requested by the driver even when the ABS braking force reduction request value is reduced, thereby preventing the timing of the reduction in braking / driving force by the motor and the increase in brake braking force from occurring at the same time.

[0052] On the other hand, since it is necessary to quickly restore the braking force to the driver's requested braking force when the motor torque output is held at "0," a large positive value of specified rate 3 is used. This staggers the timing of the increase in braking force and the decrease in the braking / driving force by the motor, making it possible to always respond to changes in the road surface, etc.

[0053] FIG. 13 is provided to explain the gain map 41 shown in FIG. 3 and shows the relationship between the rotational speed of the brake motor and the gain. This map calculates a larger gain as the rotational speed of the brake motor increases (i.e., as conditions increase that make it more likely that the reduction in braking force due to braking will be delayed). Specifically, when the rotational speed of the brake motor is between "0" and X1, the gain is set to Y1, and when the rotational speed of the brake motor is between X1 and X2, the gain is increased from Y1 to Y2. When the rotational speed of the brake motor exceeds X2, the gain is set to Y2.

[0054] When the rotation speed of the brake motor is high, the braking force cannot be reduced unless the brake motor is rotated in reverse, resulting in a delay time before the braking force decreases. However, by outputting a gain according to the rotation speed of the brake motor, calculating the drive torque, and applying it to the slipping wheel using feedforward control (FF control), the braking force applied to the slipping wheel can be canceled out, thereby suppressing incipient slip. In this way, by determining the drive torque according to the rotation state of the brake motor, it is possible to effectively suppress incipient slip.

[0055] A preferred example is a vehicle control method executed by a control unit, in which, when a driving force is applied by the braking / driving electric motor during deceleration of the electric vehicle by driving the friction braking electric motor, the driving force is made larger when the rotational speed of the friction braking / driving electric motor is 20% (indicated by the arrow) of the maximum output of the friction braking electric motor than when the rotational speed of the friction braking / driving electric motor is zero. In this way, the control unit controls so that the driving force applied when the slip ratio exceeds a predetermined threshold value increases as the physical quantity related to the rotational speed of the friction braking / driving electric motor increases.

[0056] Note that while Y1, which is the gain when the rotational speed of the brake motor ranges from "0" to X1, is a value other than "0," it may be "0," and a map may be used in which the gain changes between when the rotational speed is "0" and when it is X1. Also, Y2, which is the gain when the rotational speed of the brake motor is high (when it is X2), may be "1." Furthermore, although this map is used in which the gain decreases when the rotational speed is "0," a map in which the gain Y1 continues up to a negative rotational speed may also be used.

[0057] FIG. 14 is used to explain the gain map 42 in FIG. 3 and shows the relationship between the slip ratio change rate and the gain. This map calculates a larger gain as the slip ratio change rate increases in the positive direction (i.e., the more likely the wheel lock is to occur). Specifically, the gain increases from 0 to A1 when the slip ratio change rate goes from 0 to B1, and is set to A1 from B1 to B2. The gain then increases as the slip ratio change rate goes from B2 to B3, and is set to A2 when the slip ratio change rate exceeds B3.

[0058] In this way, the control unit controls the driving force based on a physical quantity related to the reference braking force, a physical quantity related to the rotational speed of the friction braking / driving electric motor, and the rate of change of the slip ratio. When the rate of change of the slip ratio is slow, it is assumed that there is sufficient time for the brake motor to adjust the pad position. Therefore, by using this map to reduce the driving torque output by the braking / driving electric motor, unnecessary application of driving torque is suppressed. Furthermore, because the map is designed so that the gain decreases as the rate of change of the slip ratio decreases, it is possible to suppress the output of driving torque when there is little need to increase the driving torque. By determining the driving torque according to the slip condition, unnecessary deterioration of electric fuel economy can be suppressed.

[0059] Note that A1, which is the gain when the slip ratio change rate changes from B1 to B2, is a value other than "0," but it may also be "0." Also, A1 is set to continue up to slip ratio change rate B2, but it may also be set to different values ​​when the slip ratio change rate is B1 and B2. A2, which is the gain when the slip ratio change rate is fast (at B3), may also be "1." Furthermore, while the map is set so that the gain is "0" when the slip ratio change rate is "0," it may also be set so that the slip ratio change rate at which the gain becomes "0" is offset in the positive or negative direction from 0.

[0060] [FF Driving Force Reduction Gain Map] Figure 15 is used to explain the gain map 48 in Figure 3, and shows the relationship between the slip ratio change rate, slip ratio, and gain. This map calculates a gain that reduces the increased driving force reference value in situations where it is determined that ABS intervention by the braking / driving electric motor can be weakened, based on the slip ratio change rate and slip ratio. When the slip ratio change rate is fast and the slip ratio is large, the gain is set to P1.

[0061] The control unit determines the gradient of reduction in driving force in the second control, which will be described later with reference to Figure 17, based on the rate of change of the slip ratio. If the rate of change of the slip ratio and the slip ratio show a tendency to decrease, the control unit reduces the gain multiplied by the FF control, thereby bringing the braking force applied to the vehicle closer to that required by the driver. When the slip ratio is deemed to have decreased sufficiently, the control unit reduces the driving torque based on the slip condition, since it is necessary to restore the braking force requested by the driver.

[0062] In FIG. 15 , P1 is preferably set to "1," but may be set to a value smaller than "1." Q2 is the value when the slip ratio change rate is high in the increasing direction of the slip ratio. Q2 may be the rate at which the slip ratio change rate is expected to begin to decrease, for example, it may be set to "0." Although Q2 may be set to "0" as described above, for example, the slip ratio change rate Q1 at which the gain becomes "0" may be set to "0," and Q2 may be set to a value that indicates a positive slip ratio change rate. Slip ratio threshold value R2 is set to a value larger than R1, and may be set to, for example, the same as the slip determination threshold value, or may be set to a value smaller than the slip determination threshold value. Slip ratio threshold value R1 is set to a value smaller than threshold value R2, and may be set to, for example, the same as the slip ratio used to determine the end of ABS control.

[0063] [Gain Map Based on State After Slip Determination] Figure 16 is used to explain the gain map 51 in Figure 4, and shows the relationship between the time elapsed since slip determination, the slip ratio change rate, and the gain. This map calculates the gain based on the slip ratio change rate and the time elapsed since slip determination. By allowing the brake braking force to be smaller than the motor driving force depending on the slip condition and the time elapsed since slip, it is possible to provide more assistance in recovering from slip when it takes a long time to recover from slip or when the slip ratio change rate is fast. The slip ratio change rate F1 is set so that the slip ratio change rate is fast in the direction of wheel lock.

[0064] When the rate of change in the increasing direction of the slip ratio is smaller than a predetermined value, the control unit sets the control range for the friction braking force in the first control, which will be described later with reference to Figure 18, to a braking force equal to or greater than the braking force that balances the driving force maintained in the first control until a predetermined time has elapsed, and when the slip ratio does not change in the decreasing direction even after the predetermined time has elapsed, sets the control range to a braking force smaller than the balancing braking force.

[0065] 16, if the slip ratio change rate indicates an increasing tendency for the slip ratio and furthermore, if time has passed since slip detection, the gain output from gain map 51 based on the state after slip detection is reduced to allow the braking force to be smaller than the motor drive torque, thereby helping to recover from wheel lock. In this way, by allowing the braking force to be smaller than the motor drive torque depending on the slip condition and the time elapsed since slip, it is possible to prevent situations in which the wheels do not tend to recover from lock even after a predetermined time has passed since slip detection.

[0066] The slip ratio change rate F2 may be set to a value smaller than F1, for example, "0." Also, in FIG. 16, the elapsed time E1 after slip determination is set to a value other than "0," but it may also be set to "0." While the map shows E1 set to a value smaller than E2, E1 and E2 may also be set to the same value. Furthermore, the gain when the slip ratio change rate F1 and the elapsed time E1 are the same as the gain when the slip ratio change rate F2 and the elapsed time E2 are the same, that is, D1, but a different, smaller value may also be set. Here, the gain D1, although not explicitly shown, may also be set to "1."

[0067] [Example of Basic Operation During Slip] Next, the basic operation during slip in the above-described configuration will be described with reference to the timing chart in Figure 17. During slip, the control unit executes a first control to maintain the driving force and reduce the frictional braking force until the slip ratio decreases, executes a second control to maintain the frictional braking force and reduce the driving force when the slip ratio decreases, and executes a third control to increase the frictional braking force after the driving force has been reduced to a predetermined driving force ("0").

[0068] Friction braking electric motor (friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ ) has a delay in responding to changes in the situation when the rotation speed is high, and the braking / driving electric motor (IWM12 ＦＬ , 12 ＦＲ , 12ＲＬ , 12 ＲＲ ) has a limit to the driving force it can output, so it may be difficult to increase the driving torque. Therefore, by staggering the operation of each actuator, it is possible to follow changes in the situation. In this way, by making it possible for either the brake motor or the braking / driving electric motor to move quickly, it is possible to respond quickly to changes in the slip ratio.

[0069] In other words, the control unit sets the friction braking force in the first control to the third control within a control range equal to or greater than the braking force that balances with the driving force maintained in the first control. Because the driving force is output by the electric motor for braking / driving, if the original ABS braking force reduction request were accepted as is, there is a risk that the driving wheels would accelerate due to the driving torque. Therefore, the control range of the brake braking force is set to operate only within a torque range greater than the torque output by the electric motor for braking / driving. This prevents the braking force from being unnecessarily reduced by the brake motor, which would erroneously accelerate the driving wheels.

[0070] At time t1 when the specific wheel speed falls below the slip threshold speed, the driving force of the braking / driving electric motor is increased based on the brake motor rotation speed and slip ratio change rate at that time. The brake control device then reduces the braking force based on the final ABS braking force reduction request value for the brakes. At this time, the braking force is controlled within a range from the driver-requested braking force to balance with the motor driving force so as not to accelerate.

[0071] At time t2, when the vehicle begins to recover from slip, the braking force is maintained, and the motor driving force is quickly reduced. At time t3, when the motor driving force is "0" or below a specified value, the motor braking force is maintained at that value, and the braking force is increased toward the driver-requested braking force. At time t4, when the brake braking force has returned to the driver-requested braking force, the motor braking force is changed toward the driver-requested braking force. Here, it has been described that the brake braking force is maintained at time t2, but it may also be increased at a rate that is sufficiently gradual compared to the reduction in motor driving force.

[0072] In this control, torque is calculated according to the rotational speed of the brake motor, which is an index of the difficulty of releasing the braking force (difficulty of returning the brake pad position) at the initial stage of slippage. This makes it possible to suppress an increase in the slip ratio at the initial stage of slippage, even in situations where it is difficult to reduce the braking force. In this way, by referencing the rotational speed of the brake motor when wheel lock is detected (when ABS start is determined), and calculating the drive torque of the braking / driving electric motor according to that rotational speed, a large drive torque can be applied at the initial stage of slippage, thereby effectively suppressing initial slippage and improving vehicle stability.

[0073] 18 is a timing chart showing the operation when the gain map 51 based on the state after slip determination is used. In this example, if the slip rate does not decrease after a predetermined time has elapsed, the braking force applied by the brake motor is permitted to be smaller than the braking force that balances the driving force applied by the braking / driving electric motor.

[0074] At time t1 when the specific wheel speed falls below the slip threshold speed, the driving force of the braking / driving electric motor is increased based on the brake motor rotation speed and slip ratio change rate at that time. The brake control device then reduces the brake braking force based on the final ABS braking force reduction request value for the brakes. At this time, the brake braking force is controlled within a range from the driver-requested braking force to a braking force that balances with the motor driving force so as not to erroneously accelerate the vehicle. In Figure 18, the brake braking force is reduced to a level that balances with the motor driving force at time t2.

[0075] At time t3, a predetermined time after slippage is detected, the brake braking force is reduced to a value equal to or less than the brake braking force that balances with the motor driving force. At time t4, when the vehicle begins to recover from slippage, the brake braking force is maintained and the motor driving force is quickly reduced. At time t5, when the motor driving force is zero or less than a specified value, the motor braking force is maintained at that value and the brake braking force is increased toward the driver-requested braking force. At time t6, when the brake braking force has returned to the driver-requested braking force, the motor braking force is changed toward the driver-requested braking force. This makes it possible to effectively suppress slippage when it is taking a long time to recover from slippage.

[0076] [Example of Operation When the Predetermined Time is Set to 0 When the Slip Ratio Changes Fast in the Gain Map Based on the State After Slip Determination (When the Slip Ratio Changes Fast)] Fig. 19 is a timing chart showing operation when the predetermined time is set to 0 when the slip ratio changes fast in the gain map based on the state after slip determination. This example shows operation when the slip ratio change rate is fast and the slip ratio increases suddenly.

[0077] In other words, in the gain map based on the state after slip determination, when the rate of change of the slip ratio is fast in the positive direction, the time elapsed after slip determination until the gain is reduced is set to "0," thereby allowing the braking force of the brake motor to be reduced to a range smaller than the driving force of the braking / driving electric motor without waiting a predetermined time. This makes it possible to quickly suppress slip even in situations where the slip ratio is likely to increase.

[0078] When the rate of change in the increasing direction of the slip ratio is greater than a predetermined value, the control unit controls the friction braking force in the first control to a range up to a braking force smaller than the braking force that balances with the driving force maintained in the first control.When the rate of change in the slip ratio is fast, slip is suppressed more quickly by making the braking force equal to or less than the driving force without waiting for a predetermined time.

[0079] At time t1, the rate of change of the slip ratio is sufficiently fast in the direction of increasing slip, so the braking force is reduced without any elapsed time (when E1 = 0) based on a gain map based on the state after slip determination, and the braking force is allowed to become equal to or less than the driving force of the electric motor for braking and driving. Next, at time t2, when the vehicle begins to recover from slip, the braking force is maintained and the driving force of the motor is quickly reduced.

[0080] At time t3, when the motor driving force becomes "0" or equal to or less than a specified value, the motor braking force is maintained at that value, and the brake braking force is increased toward the driver-requested braking force. Then, at time t4, when the brake braking force returns to the driver-requested braking force, the motor braking force is changed toward the driver-requested braking force. By doing this, incipient slip can be suppressed more quickly when the slip change rate is very fast.

[0081] [Example in which the slip ratio increases again while it is decreasing] Figure 20 is a timing chart showing the operation when the slip ratio increases again while it is decreasing. This example shows the operation when the slip ratio starts to increase again while it is decreasing. The operation is the same as in the other examples from time t1 to t3, but at time t4, while the brake braking force is being increased toward the braking force requested by the driver, it is detected that the slip ratio change rate has once again increased in the direction of the slip ratio increase. Therefore, the FF drive force is reset, and from this time onwards, slip suppression is again carried out as in the other examples.

[0082] [Embodiment suitable for slippage during constant deceleration] Figures 21 and 22 are block diagrams showing an example of the configuration of a vehicle control device according to a second embodiment of the present invention. This example is configured to assist the braking motor with the driving force of the braking / driving electric motor even when the rotation speed of the braking motor is not high. In Figures 21 and 22, as in Figures 3 and 4, the IWM 12 in the vehicle control device 20 shown in Figure 1 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ (Electric motor for braking and driving) and friction brake actuator 14 ＦＬ, 14 ＦＲ , 14 ＲＬ , 14 ＲＲ The control section of the electric motor for friction braking is shown.

[0083] In the second embodiment, instead of the gain map 42 based on the slip ratio change rate and the multiplication unit 43 in the first embodiment, a gain map 61 based on the slip ratio change rate and pad position and a selection unit 62 are provided. The larger of the outputs of the gain map 41 and the gain map 61 is selected by the selection unit 62 and multiplied by the reference braking force in the multiplication unit 44 to generate an FF driving force which is input to the FF driving force holding unit 45. The other configuration is the same as in Figures 2A, 2B and 3, so the same parts are designated by the same reference numerals and detailed description thereof will be omitted.

[0084] Even during constant deceleration (when the brake motor rotation speed is not high), if the slip ratio changes rapidly in the direction of increasing slip ratio, there is a risk that the responsiveness to reduce braking force may not be sufficient. Therefore, a configuration is adopted in which the larger gain is output between the output value of the gain map based on the brake motor rotation speed and the gain map based on the slip ratio change rate and pad position. This aims to output driving force from the braking / drive electric motor and speed up recovery from slip when the slip ratio change rate is fast or when the braking force is strong and a large amount of braking force must be released quickly, even if the motor rotation speed is low.

[0085] The physical quantity related to the reference braking force is a physical quantity related to the position of the friction pad (current value of the electric motor for friction braking or friction braking torque), and the control unit controls the driving force based on the larger of the physical quantity related to the position of the friction pad, an adjustment gain based on the physical quantity related to the rotational speed of the electric motor for friction braking, and an adjustment gain obtained based on the physical quantity related to the position of the friction pad and the rate of change of the slip ratio.

[0086] By obtaining the output of either a map based on the rotational speed of the electric motor for friction braking or a map that determines the gain based on the physical quantity related to the position of the friction pad and the rate of change of the slip ratio, whichever has the larger gain, it is possible to output driving torque when the braking force must be suddenly reduced even if the rotational speed is low.

[0087] As described above, even when the rotation speed of the brake motor is low, if the vehicle enters a split μ road surface and the road surface μ of one of the left and right wheels changes from high μ to low μ, a so-called μ change, and the braking force must be suddenly reduced, initial slip can be suppressed by using the drive torque to assist in the reduction of the braking force applied to the wheel.

[0088] [Gain Based on Slip Ratio Change Rate and Pad Position] Figure 23 is a diagram illustrating a gain map based on the slip ratio change rate and pad position. The braking / driving electric motor is required to generate a large driving force when the braking force is large and the slip ratio change rate is large in the positive direction (the direction in which the slip ratio increases). Therefore, this map determines the gain based on the pad position and the slip ratio change rate.

[0089] M1 is a set value when the rate of change of the slip ratio is not fast in the direction in which the slip ratio is increasing, and is set to a value equal to or less than "0." M2 is a set value when the rate of change of the slip ratio is faster in the direction in which the slip ratio is increasing than M1, and is set to a value at least greater than M1. L1, which is a set value related to the brake pad position, is a value when the brake is not pressed down very hard, and L2 is a value when the brake is pressed down slightly hard. K1 may be set to "1," and although K1 and K2 are set to different values ​​in the above, they may also be set to the same value.

[0090] [Another embodiment suitable for slippage during constant deceleration] Figures 24 and 25 are block diagrams showing an example of the configuration of a vehicle control device according to a third embodiment of the present invention. This example is another example of the configuration in which the braking motor is assisted by the driving force of the braking / driving electric motor even when the rotation speed of the braking motor is not high. In Figures 24 and 25, as in Figures 3 and 4, the IWM 12 in the vehicle control device 20 shown in Figure 1 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ (Electric motor for braking and driving) and friction brake actuator 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ The control section of the electric motor for friction braking is shown.

[0091] In the third embodiment, in addition to the configuration of the first embodiment, there are provided a gain map 63 based on the reduction request value change amount, a selector 64, and an absolute value calculator 65. The ABS braking force reduction request value (negative value) is input to the gain map 63, and its output is input to the selector 64 together with the output of the gain map 41, and the larger one is selected. The absolute value of the ABS braking force reduction request value is calculated in the absolute value calculator 65, and this absolute value is multiplied by the output of the gain map selected by the selector 64 in the multiplier 43. Since the other configurations are the same as those in Figures 2A, 2B, and 3, the same parts are designated by the same reference numerals and detailed description thereof will be omitted.

[0092] The physical quantity related to the reference braking force is a required value for reducing the braking force by the antilock brakes, and the control unit controls the driving force based on the larger of the required value for reducing the braking force by the antilock brakes, an adjustment gain based on a physical quantity related to the rotational speed of the electric motor for friction braking, and an adjustment gain obtained based on a change in the required value for reducing the braking force by the antilock brakes.

[0093] Since the amount of reduction in braking force by the antilock brakes is calculated based on the current braking force, the slip ratio change rate, and the slip ratio, the same effect can be obtained even when implemented using the requested reduction in braking force by the antilock brakes. In this way, even when based on the requested ABS braking force reduction value, the same effect as the main idea of ​​this patent can be achieved.

[0094] Even during constant deceleration by braking (when the rotational speed of the brake motor is not high), if the slip ratio changes rapidly in the direction of increasing the slip ratio, there is a risk that the responsiveness to reduce the braking force may be insufficient. Therefore, in this embodiment, the FF driving force is calculated based on the ABS braking force reduction request value rather than the reference braking force. Furthermore, the system is configured to output the larger gain between the map output based on the amount of change in the ABS braking force reduction request value and the gain map output based on the rotational speed of the brake motor.

[0095] As a result, even if the motor rotation speed is low, when the amount of change in the ABS braking force reduction request value is large and it is expected that a large amount of braking force must be released quickly, it is possible to output driving force from the braking / driving electric motor and aim to speed up recovery from slip. Here, the amount of change in the ABS braking force reduction request value may be the difference between the previous ABS braking force reduction request value and the current ABS braking force reduction request value, or the ABS braking force reduction request value may be calculated from a differential.

[0096] [Gain Map Based on Amount of Change in Reduction Request Value] Fig. 26 is a diagram for explaining a gain map based on the amount of change in the reduction request value. The greater the change in the braking force reduction request value, the greater the change required from the current braking / driving force of the braking / driving electric motor and the braking force of the brake. Therefore, this map is designed to increase the gain as the amount of change in the braking force reduction request value increases.

[0097] In this map, gain H1 is set to a value other than "0", but it may be set to "0", and the map may also have G2 set to "0". Furthermore, although not explicitly stated, H2 may also be set to 1. Furthermore, the amount of change in the ABS braking force reduction request value may be the difference between the previous ABS braking force reduction request value and the current ABS braking force reduction request value, or the ABS braking force reduction request value may be calculated from a differentiation.

[0098] As described above, according to the present invention, the rotational speed of the brake motor at the time of wheel lock detection is referenced, and if it is determined from the rotational speed of the brake motor that it will take time to weaken the braking force, the drive torque of the braking / driving electric motor is calculated based on a gain determined in accordance with the rotational speed of the brake motor, thereby making it possible to effectively and quickly suppress initial slippage and improve vehicle stability.

[0099] It should be noted that the configurations, methods, etc. described in the above-described embodiments are merely schematic illustrations to enable the present invention to be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical ideas set forth in the claims.

[0100] 10...electric vehicle, 11 ＦＬ , 11 ＦＲ ...Front wheels, 11 ＲＬ , 11 ＲＲ ...Rear wheels, 12 ＦＬ , 12 ＦＲ , 12 ＲＬ , 12 ＲＲ …IWM, 13 ＦＬ , 13 ＦＲ , 13 ＲＬ , 13 ＲＲ ...IWM resolver, 14 ＦＬ , 14 ＦＲ , 14 ＲＬ , 14 ＲＲ ...friction brake actuator (electric motor for friction braking), 14a...brake motor (electric motor for friction braking), 14b...ball screw mechanism, 14c...brake pad (friction pad), 14d...resolver for brake motor, 15 ＦＬ , 15 ＦＲ , 15ＲＬ , 15 ＲＲ Wheel speed sensor, 17 low-voltage battery, 18 high-voltage battery, 19 DC-DC converter, 20 vehicle control device, 21 brake control device, 22 ＦＬ , 22 ＦＲ , 22 ＲＬ , 22 ＲＲ ...IWM control device, 23...Battery control device, 24...In-vehicle communication line (CAN bus), 28, 28 ＦＬ , 28 ＦＲ , 28 ＲＬ , 28 ＲＲ ...Brake rotor (rotor)

Claims

1. A vehicle control device provided on a vehicle having a plurality of friction braking devices that apply friction braking forces to each wheel by driving friction braking electric motors to press friction pads against rotors that rotate together with the vehicle wheels, and a plurality of braking / driving electric motors that apply braking / driving forces to each of the wheels, the vehicle control device having a control unit that controls the plurality of friction braking electric motors and the plurality of braking / driving electric motors, wherein the control unit obtains a required braking force to be applied to each wheel, drives the friction braking electric motors based on the required braking force, and obtains a slip ratio of each wheel when decelerating the vehicle, and when applying a driving force to a slipping wheel of each wheel whose slip ratio exceeds a predetermined threshold value using the braking / driving electric motors, controls the driving force based on the magnitude of the friction braking force and the rate of change of the friction braking force.

2. A vehicle control device according to claim 1, wherein the magnitude of the frictional braking force is calculated based on a physical quantity related to a reference braking force based on the required braking force, and the rate of change of the frictional braking force is calculated based on a physical quantity related to the rotational speed of the electric motor for frictional braking.

3. A vehicle control device according to claim 2, wherein the control unit controls the driving force based on a physical quantity related to the reference braking force, a physical quantity related to the rotational speed of the electric motor for friction braking, and a rate of change of the slip ratio.

4. A vehicle control device according to claim 3, wherein the control unit controls the driving force to be applied when the slip ratio exceeds a predetermined threshold value so that the greater the rate of change of the slip ratio, the greater the driving force to be applied when the slip ratio exceeds a predetermined threshold value.

5. A vehicle control device according to claim 2, wherein the control unit controls the driving force to be applied when the slip ratio exceeds a predetermined threshold value so that the greater the physical quantity related to the rotational speed of the electric motor for friction braking, the greater the driving force to be applied when the slip ratio exceeds a predetermined threshold value.

6. A vehicle control device according to claim 2, wherein the control unit: executes a first control to maintain the driving force and reduce the frictional braking force until the slip ratio decreases; executes a second control to maintain the frictional braking force and reduce the driving force when the slip ratio decreases; and executes a third control to increase the frictional braking force after the driving force has been reduced to a predetermined driving force.

7. A vehicle control device according to claim 6, wherein the control unit controls the friction braking force in the first control to the third control to a range equal to or greater than the braking force that balances with the driving force maintained in the first control.

8. A vehicle control device according to claim 6, wherein the control unit determines the gradient of the decrease in the driving force in the second control based on the rate of change of the slip ratio.

9. A vehicle control device as claimed in claim 6, wherein the control unit, when the rate of change in the increasing direction of the slip ratio is smaller than a predetermined value, controls the friction braking force in the first control to a control range equal to or greater than a braking force that balances with the driving force maintained in the first control until a predetermined time has elapsed, and when the slip ratio does not change to the decreasing side even after the predetermined time has elapsed, controls the control range to a braking force smaller than the balancing braking force.

10. A vehicle control device as described in claim 6, wherein, when the rate of change in the increasing direction of the slip ratio is greater than a predetermined value, the control unit controls the friction braking force in the first control to a braking force smaller than the braking force that balances with the driving force maintained in the first control.

11. A vehicle control device as described in claim 2, wherein the physical quantity related to the reference braking force is a physical quantity related to the position of the friction pad, and the control unit controls the driving force based on the larger of the physical quantity related to the position of the friction pad, an adjustment gain based on a physical quantity related to the rotational speed of the electric motor for friction braking, and an adjustment gain obtained based on the physical quantity related to the position of the friction pad and the rate of change of the slip ratio.

12. A vehicle control device as described in claim 2, wherein the physical quantity related to the reference braking force is a required value for reducing the braking force by the antilock brakes, and the control unit controls the driving force based on the larger of the required value for reducing the braking force by the antilock brakes, an adjustment gain based on a physical quantity related to the rotational speed of the electric motor for friction braking, and an adjustment gain obtained based on a change in the required value for reducing the braking force by the antilock brakes.

13. A vehicle control method executed by a control unit mounted on a vehicle having a plurality of friction braking devices provided independently for each wheel of the vehicle and which apply friction braking force to each wheel by pressing friction pads against rotors that rotate together with the wheels through the drive of friction braking electric motors, and a plurality of braking / driving electric motors provided independently for each wheel and which apply braking / driving force to each wheel, wherein, when a driving force is applied by the braking / driving electric motors while the vehicle is decelerating due to the drive of the friction braking electric motors, the driving force is made larger when the rotational speed of the friction braking electric motors is 20% of the maximum output of the friction braking electric motors than when it is zero.

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