Vehicle control device and vehicle control method

Abstract

This invention provides a vehicle control device capable of improving vehicle stability by rapidly suppressing initial slip. The vehicle control device includes a control unit that controls a friction brake actuator and an in-wheel motor (IWM). The friction brake actuator applies friction braking force to each wheel by pressing friction pads against a rotor rotating with the wheel, and the in-wheel motor (IWM) applies braking driving force to each wheel. The control unit acquires the requested braking force applied to each wheel, drives the friction brake actuator based on the requested braking force, acquires the slip ratio of each wheel while 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 driving force is applied to a slip wheel whose slip ratio exceeds a predetermined threshold via the IWM.

Description

Technical Field

[0001] This invention relates to a vehicle control device and method for recovering a vehicle from slippage. More specifically, it relates to a device and method in which brake drive motors are mounted on each wheel, and brake pads, whose positions are adjusted by friction brake motors, are pressed against brake rotors (brake discs) that rotate together with the wheels, thereby recovering the braked vehicle from slippage. Background Technology

[0002] Patent Document 1 describes an electric vehicle in which each wheel has a drive motor for regenerative braking and friction braking. In this Patent Document 1, during friction braking, if it is determined that the wheel is prone to locking, the torque of the drive motor is controlled by a braking control device in a manner that suppresses wheel slippage.

[0003] Prior technology documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 5-270387 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, the braking technology in the aforementioned patent document 1 is essentially feedback (FB) control, which makes it difficult to improve the responsiveness to initial slip and raises concerns about the initial slip increasing. To strongly suppress initial slip, a high-gain feedback (Hi-Gain-FB) control system can be used, but high-gain feedback control is prone to instability and may not be able to suppress initial slip effectively.

[0008] The present invention was made in view of the above-mentioned circumstances, and its object is to provide a vehicle control device and a vehicle control method that can improve vehicle stability by rapidly suppressing initial slip.

[0009] Methods for solving problems

[0010] According to one aspect of the present invention, a vehicle control device having a control unit is provided, which acquires the requested braking force applied to each wheel, and when the vehicle is decelerated by driving a friction braking motor based on the requested braking force, acquires the slip ratio of each wheel, and when a driving force is applied to a slip wheel whose slip ratio exceeds a predetermined threshold by a braking drive motor, the driving force is controlled based on the magnitude of the friction braking force and the rate of change of the friction braking force.

[0011] Furthermore, according to another aspect of the present invention, a vehicle control method is provided in which, during vehicle deceleration based on a friction braking motor, when a driving force is applied by a braking drive motor, the driving force is increased at a rotational speed of 20% of the maximum output of the friction braking motor, compared to a rotational speed of zero for the friction braking motor.

[0012] Invention Effects

[0013] In the vehicle control device and method of the present invention, a driving motor for braking the slip wheel is used to apply a driving force to the slip wheel based on the magnitude and rate of change of the friction braking force. This accelerates the reduction of the braking force applied to the slip wheel in the initial stage of slippage, thereby assisting in suppressing initial slippage. As a result, initial slippage can be quickly suppressed, improving vehicle stability. Attached Figure Description

[0014] Figure 1 This is a schematic structural diagram of an electric vehicle equipped with the vehicle control device according to an embodiment of the present invention.

[0015] Figure 2A It means Figure 1 A schematic diagram of the structure of the braking system in the example.

[0016] Figure 2B It is used for Figure 2A A timing diagram illustrating the braking operation, motor rotation speed, and liner position in the braking system.

[0017] Figure 3 This is a block diagram illustrating a portion of the structural example of a vehicle control device according to the first embodiment of the present invention.

[0018] Figure 4 This is a block diagram showing the remaining parts of the vehicle control device according to the first embodiment of the present invention.

[0019] Figure 5 It means Figure 3 The control block diagram of the structure example of the slip determination unit in the middle.

[0020] Figure 6 It means Figure 3 The control block diagram of the structure example of the FF driving force reset determination unit.

[0021] Figure 7 It means Figure 3 The control block diagram of the structure example of the FF driving force holding part.

[0022] Figure 8 It means Figure 4 A control block diagram of the structure of the electric motor braking drive force output selection unit.

[0023] Figure 9 It means Figure 4 A control block diagram of the structure of the electric motor braking drive force output setting unit.

[0024] Figure 10 It means Figure 4 The control block diagram of the structure example of the motor braking drive force recovery judgment unit.

[0025] Figure 11 It means Figure 4 A control block diagram of the structure of the rate limiting unit during braking force recovery.

[0026] Figure 12 It means Figure 4 The control block diagram of the structure example of the reduced request value rate limiting section.

[0027] Figure 13 For the purpose of illustrating based on Figure 3 A graph showing the gain mapping of the rotational speed of the braking motor in the circuit.

[0028] Figure 14 It is used for based on Figure 3 The graph illustrates the gain mapping of the slip rate change rate.

[0029] Figure 15 It is used for Figure 3 The diagram illustrates the gain reduction mapping of the FF driving force.

[0030] Figure 16 It is used for based on Figure 4 The diagram illustrates the gain mapping of the state after the slip judgment.

[0031] Figure 17 It means Figure 3 and Figure 4 The timing diagram shows the basic actions of the vehicle control device during slippage.

[0032] Figure 18 It means in such Figure 3 as well as Figure 4 The vehicle control device shown utilizes a timing diagram of actions based on gain mapping of the state after slip judgment.

[0033] Figure 19 It means based on Figure 4 In the gain mapping of the state after slip judgment, the timing diagram of the action when the specified time when the slip rate changes rapidly is set to "0" is shown.

[0034] Figure 20 It is a timing diagram that shows the action when the slip ratio is increased again during the process of decreasing slip ratio.

[0035] Figure 21 This is a block diagram illustrating a portion of the structural example of a vehicle control device according to a second embodiment of the present invention.

[0036] Figure 22 This is a block diagram illustrating the remaining portion of the vehicle control device according to the second embodiment of the present invention.

[0037] Figure 23 It is used to illustrate based on Figure 21 A graph showing the gain mapping between the slip ratio change rate and the liner position.

[0038] Figure 24 This is a block diagram illustrating a portion of the structural example of a vehicle control device according to a third embodiment of the present invention.

[0039] Figure 25 This is a block diagram illustrating the remaining portion of the vehicle control device according to the third embodiment of the present invention.

[0040] Figure 26 It is used to illustrate based on Figure 24 The graph shows the gain mapping that reduces the change in the requested value. Detailed Implementation

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0042] Figure 1 This diagram illustrates a schematic structure of an electric vehicle equipped with the vehicle control device according to an embodiment of the present invention. The electric vehicle 10 has front wheels 11. FL 11 FR And rear wheel 11 RL 11 RR And towards these front wheels 11 FL 11 FR And rear wheel 11 RL 11 RR In-wheel motor (IWM) 12 FL 12 FR 12 RL 12 RR These IWM 12 FL 12 FR 12 RL 12 RR It is the electric motor for braking and driving electric vehicles 10. In IWM 12... FL 12 FR 12 RL 12 RR IWM rotary transformers 13 are set up to detect the motor speed.FL 13 FR 13 RL 13 RR In addition, the front wheel 11 FL 11 FR and rear wheel 11 RL 11 RR They are collectively referred to as wheels, trolleys, or drive wheels.

[0043] In addition, the electric vehicle 10 has a friction brake actuator (friction brake electric motor) 14 installed on each wheel to generate friction braking force on the wheel. FL 14 FR 14 RL 14 RR Friction braking actuator 14 FL 14 FR 14 RL 14 RR Driven by the friction plate, the friction pad is pressed against the wheel 11 of the electric vehicle 10. FL 11 FR 11 RL 11 RR Brake rotor (rotor) 28 rotating together FL 28 FR 28 RL 28 RR Thus, for each wheel 11 FL 11 FR 11 RL 11 RR Apply friction braking force. This is achieved by friction braking actuator 14. FL 14 FR 14 RL 14 RR Brake rotor 28 FL 28 FR 28 RL 28 RR Friction braking devices, including friction pads, are constructed on each wheel 11. FL 11 FR 11 RL 11 RR Wheel speed sensors 15 were installed to detect wheel speed. FL 15 FR 15 RL 15 RR Furthermore, the electric vehicle 10 has an acceleration sensor 16 near the vehicle's center of gravity to detect the vehicle's acceleration.

[0044] The electric vehicle 10 is equipped with a low-voltage battery (rechargeable battery) 17 for various onboard devices and an IWM 12 for use as a braking drive motor. FL 12 FR 12 RL 12 RR The high-voltage battery (rechargeable battery) 18. 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 by the voltage boosted by the DC-DC converter 19.

[0045] The electric vehicle 10 includes a vehicle control unit 20, a braking control unit 21, and an IWM control unit 22, which are electronic control devices for controlling the vehicle. FL ,twenty two FR ,twenty two RL ,twenty two RR And battery control unit 23, etc. The various control units share information with each other via the in-vehicle communication line (CAN bus) 24, which is shown in shaded lines.

[0046] The vehicle control unit 20 uses a rotary transformer 13 to detect the speed of the electric motor from the IWM. FL 13 FR 13 RL 13 RR The vehicle control unit 20 acquires information from various sensors, including the accelerator pedal sensor 25 (detecting acceleration input), the brake pedal sensor 26 (detecting braking input), and the gear position sensor 27, and performs overall control of the electric vehicle 10 based on this information. For example, in response to a requested torque corresponding to the driver's accelerator operation, the vehicle control unit 20 distributes torque according to the request and outputs various IWMs 12. FL 12 FR 12 RL 12 RR The torque requested by the driver should be output.

[0047] Braking control device 21 receives data from acceleration sensor 16 and wheel speed sensor 15. FL 15 FR 15 RL 15 RR Information is obtained from various sensors, including the brake pedal sensor 26 via the CAN bus 24. Furthermore, based on the driver's braking operation, the system calculates the activation of the friction brake motor (friction brake actuator 14). FL 14 FR 14 RL 14 RRThe frictional braking torque generated by the motor is used to adjust the position of the brake pads, thereby generating a frictional braking force. The magnitude of the frictional braking force is determined based on physical quantities related to the reference braking force based on the requested braking force (brake pad position, current value of the frictional braking motor, frictional braking torque, or ABS braking force reduction request value). Furthermore, the rate of change of the frictional braking force is determined based on physical quantities related to the rotational speed of the frictional braking motor. And, when the brake pedal is depressed, the wheel 11... FL 11 FR 11 RL 11 RR In the event of slippage, the braking force of the brakes is adjusted by regulating the braking force of the wheel in the slippage state to increase or decrease the braking force (so-called ABS action) in order to recover from the slippage.

[0048] The battery control device 23 monitors the charge / discharge state of the high-voltage battery 18 and the individual cell units constituting the high-voltage battery 18. The battery control device 23 calculates the battery requested torque limit value based on the charge / discharge state of the high-voltage battery 18, etc. The battery requested torque limit value is calculated for each 1Wm 12 FL 12 FR 12 RL 12 RR The maximum allowable torque. For example, when the charge level of the high-voltage battery 18 decreases, the battery requested torque limit value is set to a value smaller than usual. IWM control device 22 FL ,twenty two FR ,twenty two RL ,twenty two RR Controlling the torque request to IWM 12 based on IWM FL 12 FR 12 RL 12 RR The electricity supplied.

[0049] Figure 2A It means Figure 1 A schematic diagram of the structure of the braking system is shown. In this example, the friction braking device is an electric caliper brake. A ball screw mechanism 14b, which converts the rotation of the braking motor (friction braking motor) 14a into linear motion, presses the brake pads (friction pads) 14c onto the braking rotor (rotor) 28. The braking rotor 28 rotates integrally with each wheel, and the brake pads 14c are pressed in the direction of the rotation axis of each wheel, as indicated by the arrow, thereby generating braking force using friction. A brake motor rotary transformer 14d for detecting the motor speed is installed on the braking motor 14a.

[0050] Figure 2B It is used for Figure 2A The timing diagram illustrates the braking operation, motor rotation speed, and pad position in the braking system. If the driver performs the braking operation (time t0), the rotation speed of the braking motor 14a increases in response to the amount of brake operation. Through the ball screw mechanism 14b, the rotational motion of the braking motor 14a is converted into linear motion, and the brake pad 14c approaches the brake rotor 28 (time t1).

[0051] Between time t1 and t2, with the brake pedal operated with a fixed pedal force, the rotational speed of the motor continues to increase, and the brake pad 14c is pressed against the brake rotor 28.

[0052] At time t2, if the driver releases the brake pedal force to a fixed level, the motor's rotational speed decreases, becomes negative (i.e., reverses) at time t3, and then reaches a constant speed. The brake pad 14c remains pressed against the brake rotor 28 after the brake is released, and is released by the motor reversing. Therefore, the time interval between t2 and t3, indicated by arrow AA, is the delay time during which the braking force does not decrease.

[0053] [First Implementation Method (Overall Image of the Control Structure)]

[0054] Figure 3 and Figure 4 This is a block diagram illustrating a structural example of a vehicle control device according to the first embodiment of the present invention. Figure 3 as well as Figure 4 Extract from Figure 1 The IWM 12 in the vehicle control unit 20 shown FL 12 FR 12 RL 12 RR (Electric motor for brake drive) and friction brake actuator 14 FL 14 FR 14 RL 14 RR The control unit of the (friction brake motor) is shown.

[0055] In this first embodiment, it is used for each wheel 11 FL 11 FR 11 RL 11 RR IWM 12 FL 12 FR 12 RL 12 RR and friction brake actuator 14 FL 14 FR 14 RL 14 RRSelective control is implemented, and the driver's request command value for the brake drive motor is a command value generated separately for each IWM. Furthermore, for example, in the right front wheel 11... FR In the case of slippage, the IWM 12 on the right front wheel FR Friction brake actuator 14 of the right front wheel FR The combination of control measures is implemented.

[0056] The control unit of the vehicle control device 20 is configured to input the position of the brake pads (or the current value of the brake motor), the rotational speed of the brake motor, the slip ratio change rate, the slip ratio, the braking force request value for the brake calculated in the brake control device 21 based on the amount of braking operation, the ABS braking force reduction request value calculated by the brake control device 21 during slip, and the driver request command value for the brake drive motor determined based on the vehicle speed and the amount of accelerator pedal operation by the driver, and output the motor braking drive force recovery judgment flag, the final ABS braking force reduction request value, and the final braking drive force command value for the motor.

[0057] The position of the brake pads (or the current value of the brake motor) is input to the base braking force mapping 40. The base braking force mapping 40 is a mapping that transforms physical quantities related to the position of the pads moved by the brake motor (friction brake actuator) and the current of the brake motor into a braking force reference value. Alternatively, it can be configured to use a structure that calculates the braking force of the brake using the pressure of the brake pads, etc., without performing the conversion based on the base braking force mapping 40, or it can directly use a structure that uses the braking force request value of the brake calculated by the brake control device 21.

[0058] The rotational speed of the brake motor is input into a gain mapping 41 based on the rotational speed of the brake motor. Gain mapping 41 calculates a larger gain as the rotational speed of the brake motor increases. The slip ratio change rate is input into a gain mapping 42 based on the slip ratio change rate. The slip ratio change rate is a value obtained by differentiating the slip ratio and is used to determine whether the braking force generated by each wheel deviates significantly from the braking force that can be generated on the road surface. Gain mapping 42 calculates a larger gain as the slip ratio change rate increases in the direction of increasing slip ratio. Furthermore, a reference braking force is output from the base braking force mapping 40, a gain based on the rotational speed of the brake motor is output from gain mapping 41, and a gain based on the slip ratio change rate is output from gain mapping 42.

[0059] The reference braking force output from the base braking force mapping 40 is multiplied by the gain output from the gain mapping 41 in the multiplication unit 43 and input to the motor braking drive force recovery determination unit 50. The multiplication result of the multiplication unit 43 is multiplied by the gain output from the gain mapping 42 in the multiplication unit 44 and input as the FF driving force to the FF driving force holding unit 45. The FF driving force holding unit 45 holds the FF driving force when the slip ratio is above the slip determination threshold (when slip is determined), or the FF driving force when the FF driving force reset determination unit 47 has made a reset determination.

[0060] The slip ratio is input to the slip determination unit 46. The slip ratio during vehicle deceleration is calculated based on the following formula.

[0061] [Formula 1]

[0062]

[0063] Here, Si is the slip ratio of each wheel, V is the vehicle speed, vi is the speed of each wheel, and i is the wheel number (i=1,...,4).

[0064] In the above formula, the closer the slip ratio Si is to "1", the higher the probability of wheel lock-up; the smaller Si is, the lower the probability of wheel lock-up.

[0065] In addition, the vehicle speed can be obtained through sensors or estimated using wheel speed and electric motor speed.

[0066] In the slip determination unit 46, it is determined whether slippage occurs in each wheel. If the slip ratio calculated based on the vehicle speed and the speed of each wheel exceeds the slip determination threshold in any wheel, slippage is determined to be occurring. Conversely, if the slip ratio is below the non-slip determination threshold, non-slippage is determined to be occurring. The output of the slip determination unit 46 is input to the FF drive force reset determination unit 47, the FF drive force holding unit 45, the gain mapping table 51 based on the state after slippage determination, and the electric motor brake drive force recovery determination unit 50, respectively.

[0067] Additionally, 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. In the slip determination unit 46, during slip determination, the FF driving force reset determination unit 47 sets an FF driving force reset determination flag when the slip ratio change rate becomes less than or equal to the decrease determination threshold, and when it becomes greater than or equal to the slip ratio increase determination threshold.

[0068] The slip rate change rate and slip rate are input to the FF driving force reduction gain mapping 48. In the multiplication unit 49, the output of the gain mapping 48 is multiplied by the driving force held by the FF driving force holding unit 45 to generate an increased driving force reference value. When the gain mapping 48 determines that there is a tendency to recover from slip based on the slip rate and the slip rate change rate, it outputs a gain that reduces the driving force held by the FF driving force holding unit 45.

[0069] The driver's request command value for the braking drive motor is input to the selection unit 57, the motor braking drive force output selection unit 59, and the motor braking drive force output setting unit 60, respectively. In the selection unit 57, a driving force to counteract the regenerative braking force of the driver's request command value is added, limited to zero ("0"), so as not to become a driving force that is too large relative to the driving force held in the FF driving force holding unit 45. In the deviation calculation unit 58, the driving force increase command value is calculated based on the deviation between the increase driving force reference value and the driver's request command value. Here, it is limited to zero in this embodiment, but for example, if the slip ratio is expected to increase based on the slip ratio and the slip ratio change rate, the driving force to counteract the regenerative braking force can also be added in order to suppress the initial slip more quickly. The calculated driving force increase command value is input to the motor braking drive force output selection unit 59 and the motor braking drive force output setting unit 60. The output of the motor braking drive force output selection unit 59 is also input to the motor braking drive force recovery judgment flag output from the motor braking drive force recovery judgment unit 50. The output of the output selection unit 59 is input to the motor braking drive force output setting unit 60, the braking force recovery rate limiting unit 52, and the reduction request value rate limiting unit 54.

[0070] When the electric motor brake drive force recovery determination unit 50 performs a judgment on whether electric motor brake drive force recovery is permitted, the electric motor brake drive force output selection unit 59 determines that it will output the driver's request command value for the brake drive motor. Alternatively, if electric motor brake drive force recovery is not permitted, the selection is performed as follows: if the sum of the drive force increase command value and the driver's request command value for the brake drive motor is greater than "0", the sum is output; if the sum is less than or equal to "0", "0" is output. Here, a sum of "0" is used as a threshold to set the output selection flag, but values ​​other than "0" can also be used as thresholds. The electric motor brake drive force output setting unit 60, based on the selection value output from the output selection unit 59, sets the torque set by the output setting unit 60 as the torque for the brake drive motor (IWM12). FL 12 FR 12 RL 12 RR The final braking driving force command value is output.

[0071] In the electric motor brake drive force recovery determination unit 50, in addition to the reference braking force output from the base braking force mapping 40 and the output of the slip determination unit 46 as described above, a braking force request value for the brake and an ABS braking force reduction request value (negative value) are also input. Based on the reference braking force, the braking force request value for the brake, the ABS braking force reduction request value, and the output of the slip determination unit, the electric motor brake drive force recovery permission determination is performed when slip judgment is not performed, the reference braking force is equal to the braking force request value for the brake, and the ABS braking force reduction request value is greater than or equal to a predetermined value. That is, the electric motor brake drive force recovery permission determination is performed when the braking force request value for the brake is equal to the reference braking force and slip is not determined in the slip determination unit 46, or when the braking force request value for the brake is equal to the reference braking force and the ABS braking force reduction request value meets or exceeds a predetermined value. Furthermore, an electric motor brake drive force recovery determination flag is established.

[0072] In the gain mapping 51 based on the state after slip determination, the slip rate change rate and the output of the slip determination unit 46 are input. This gain mapping 51 calculates a gain less than "1" based on the elapsed time since slip was determined in the slip determination unit 46, and the slip rate change rate, if it is determined that recovery from slip is insufficient even after a predetermined time. Furthermore, by reducing the braking force in a manner that establishes a relationship of "driving force of the brake drive motor ≥ braking force of the brake," it helps to quickly recover from slip.

[0073] An increase in driving force reference value is input to the rate limiting unit 52 when braking force is restored. When there is a tendency to recover from slippage, the driving force increase command value is close to "0", and both the electric motor braking driving force and the brake force are restored to the values ​​requested by the driver. However, if the electric motor braking driving force and the brake force are returned to the values ​​requested by the driver at the same timing, the braking force is restored sharply, and the vehicle will fall into a slippage state again.

[0074] Therefore, in order to increase the braking force of the brake after reducing the electric motor braking driving force to "0", the rate of decrease of the reference value of the increased driving force output to the brake braking force side is changed based on whether the output of the electric motor braking driving force output setting unit is "0" (or it may not be "0" but set to a value below a specified value), thereby performing the operation described above.

[0075] The outputs of gain mapping 51 and rate limiting unit 52 are input to multiplication unit 53 and multiplied. The ABS braking force reduction request value and the output of electric motor braking drive force output selection unit 59 are input to reduction request value rate limiting unit 54. The outputs of multiplication unit 53 and reduction request value ratio limiting unit 54 are added in addition unit 55 and input to selection unit 56. In selection unit 56, the final ABS braking force reduction request value is limited to "0" to prevent it from becoming positive, and the final ABS braking force reduction request value is output.

[0076] Furthermore, the ABS braking force reduction request value does not represent the amount of reduction requested from the current braking force of the brakes, but rather a signal representing the amount of reduction requested from the driver regarding the braking force of the brakes. This signal is configured as a negative value, but it can also be configured to be implemented based on this negative value if it is positive.

[0077] Alternatively, the pressure sensor can be mounted on the brake pads, and the differential value of the pressure sensor can be used instead of the rotational speed of the brake motor.

[0078] The above will be described in detail below. Figure 3 and Figure 4 Examples of the structure of each module in the document.

[0079] [Slip Detection Section]

[0080] Figure 5 It means Figure 3 The diagram shows a control block diagram illustrating the structure of the slip determination unit 46. The slip determination unit 46 determines whether slippage occurs in each wheel. Based on the slip ratio calculated from the vehicle speed and the speed of each wheel, if the slip ratio in a particular wheel is greater than or equal to a slip determination threshold, slippage is determined, and a slip determination flag is set to "1". Conversely, if the slip ratio is less than or equal to a no-slip determination threshold, no slippage is determined, and a slip determination flag is set to "0".

[0081] [FF Drive Force Resetting Judgment Unit]

[0082] Figure 6 It means Figure 3The diagram shows a control block diagram of an example structure of the FF driving force reset determination unit 47. In the FF driving force reset determination unit 47, during slip determination, if the slip rate change rate is less than or equal to the slip rate decrease determination threshold, but greater than or equal to the slip rate increase determination threshold, an FF driving force reset determination flag is set. That is, if the slip rate change rate is less than or equal to the slip rate decrease determination threshold, it is determined that the slip rate is decreasing, and the flag is set to "0". On the other hand, if the slip rate change rate is greater than or equal to the slip rate increase determination threshold, it is determined that the slip rate is increasing, and the flag is set to "1".

[0083] If the slip ratio decreases, begins to recover, and then increases again to "1", the torque needs to be reset. Therefore, if the previous value was "0", and the slip ratio change rate increases and the flag becomes "1", and the slip judgment flag becomes "1", then the FF drive force reset judgment flag is set to "1" and a reset request is made. If at least one of the conditions is not met, the FF drive force reset judgment flag is set to "0" and no reset request is made.

[0084] [FF Drive Force Retention Unit]

[0085] Figure 7 It means Figure 3 The control block diagram shows an example of the structure of the FF driving force holding unit 45. The FF driving force holding unit 45 holds the FF driving force when a slip determination is made in the slip determination unit 46 or when a reset determination is made in the FF driving force reset determination unit 47.

[0086] That is, when the slip judgment flag is "1" and the previous slip judgment flag was "0", the logical AND condition is met, and the FF driving force is output as the FF driving hold value. Similarly, when the FF driving force judgment flag is reset to "1", the FF driving force is output as the FF driving hold value. Furthermore, when the logical AND condition on the slip judgment flag side is not met, and the FF driving force judgment flag is reset to "0", the previous value is output as the FF driving hold value.

[0087] [Electric Motor Braking Drive Force Output Selection Unit]

[0088] Figure 8 It means Figure 4The control block diagram shows an example of the structure of the electric motor braking drive force output selection unit 59. The electric motor braking drive force output selection unit 59 selects to output any one of the following based on the judgment result (electric motor braking drive force recovery judgment flag) of the electric motor braking drive force recovery judgment unit 50, the drive force increase command value, the driver request command value for the braking drive motor, and "0".

[0089] If a restoration permission determination is performed in the electric motor brake drive force restoration determination unit 50, the output is set to the driver's requested torque command value for the brake drive motor. If a restoration permission determination is not performed in the electric motor brake drive force restoration determination unit 50, and the sum of the electric motor brake drive force increase command value and the driver's requested command value for the brake drive motor is greater than "0", the output is set to the sum of the drive force increase command value and the driver's requested command value for the brake drive motor. On the other hand, if the sum of the drive force increase command value and the driver's requested command value for the brake drive motor is less than or equal to "0", the output is set to "0".

[0090] Therefore, when the electric motor braking drive force recovery judgment flag is "1", the electric motor braking drive force output selection flag becomes "1". When the electric motor braking drive force recovery judgment flag is "0", if the sum of the driving force increase command value and the driver request command value for the braking drive motor is greater than "0", the electric motor braking drive force output selection flag is set to "2"; if it is less than or equal to "0", the electric motor braking drive force output selection flag is set to "3". The electric motor braking drive force output selection flag being "2" indicates continuous output of drive torque during slippage, while the electric motor braking drive force output selection flag being "3" indicates maintaining the drive torque at "0" while waiting for brake recovery.

[0091] [Electric Motor Braking Drive Force Output Setting Unit]

[0092] Figure 9 It means Figure 4 The control block diagram shows an example of the structure of the electric motor braking drive force output setting unit 60. In the electric motor braking drive force output setting unit 60, the driver request command value for the braking drive motor, the sum of the driver request command value for the braking drive motor and the drive force increase command value, or "0" is set based on the electric motor braking drive force output selection flag "1", "2" or "3", and the final braking drive force command value for the braking drive motor is output.

[0093] [Electric Motor Braking Drive Force Recovery Judgment Unit]

[0094] Figure 10 It means Figure 4 The control block diagram shows an example of the structure of the electric motor brake drive force recovery determination unit 50. In the electric motor brake drive force recovery determination unit 50, if the braking force request value from the driver is equal to the reference braking force and no slip determination is performed in the slip determination unit 46 (the slip determination flag is "0"), or if the conditions are met that the braking force request value is equal to the reference braking force and the ABS braking force reduction request value is greater than or equal to a specified value, it is determined that the electric motor brake drive force recovery is allowed, and a flag (electric motor brake drive force recovery determination flag) is established.

[0095] [Rate limiting section during braking force recovery]

[0096] Figure 11 It means Figure 4 The control block diagram shows an example of the structure of the rate limiting unit 52 during brake force recovery. When the flag of the electric motor brake drive force output selection unit 59 is set to "3" and the brake drive force is set to "0", that is, when it is believed that the brake force can be restored to the time requested by the driver, the brake force is quickly restored by changing from the specified rate 2 to the specified rate 1.

[0097] Here, the specified rate 2 is "0" or a very small negative value, and the specified rate 1 is a negative value that is larger than the specified rate 2 (for example, the specified rate 1 is a larger negative value, such as the specified rate 2 being -5 and the specified rate 1 being -100).

[0098] In the slip determination, when the final braking drive force command value of the electric motor is a positive command, in order to prevent the braking force of the brake from rapidly approaching the braking force requested by the driver, a specified rate 2, which is set to a small negative value or "0", is adopted, so that the timing of the decrease of the braking drive force of the electric motor and the increase of the braking force of the brake are different.

[0099] On the other hand, when the motor torque output is kept at "0", it is necessary to quickly restore the braking force of the brake to the braking force requested by the driver, so a specified rate of 1 with a large negative value is used.

[0100] Therefore, the timing of the increase in braking force of the brake and the decrease in braking driving force generated by the electric motor can be staggered, so that one side can always be responded to when the road surface changes.

[0101] [Reduce request rate limit]

[0102] Figure 12 It means Figure 4The control block diagram shows an example of the structure of the rate limiting unit 54 for reducing the requested braking force. By reducing the braking force driving force of the electric motor through the rate limiting unit 52 during braking force recovery, it is possible to prevent the frictional braking force from increasing at the same time. However, based solely on this logic, since the ABS braking force reduction request value itself decreases, it is impossible to prevent the frictional braking force from increasing in the direction close to the driver's requested braking force.

[0103] Therefore, when the braking force is set to "0" by the mark of the electric motor braking force output selection unit 59, that is, when it is believed that the timed ABS braking force reduction request value that can restore the braking force of the brake to the braking force requested by the driver has decreased, the braking force of the brake is quickly restored by changing from the specified rate 4 to the specified rate 3.

[0104] Here, the specified rate 4 is "0" or set to a very small positive value, and the specified rate 3 is set to a positive value greater than the specified rate 4 (for example, the specified rate 4 is +5, the specified rate 3 is +100, and the specified rate 3 is a large negative value).

[0105] In the slip determination, when the final braking drive force command value of the electric motor is a positive command, in order to prevent the brake force from rapidly approaching the driver's requested braking force even when the ABS braking force reduction request value is reduced, a specified rate of 4, which is set to a smaller positive value or "0", is adopted, so that the timing of the reduction of the electric motor's braking drive force and the increase of the brake force are different.

[0106] On the other hand, when the motor torque output is kept at "0", it is necessary to quickly restore the braking force of the brake to the braking force requested by the driver, so a specified rate of 3 with a large positive value is used.

[0107] Therefore, the timing of the increase in braking force of the brake and the decrease in braking driving force generated by the electric motor can be staggered, so that one side can always be responded to when the road surface changes.

[0108] Figure 13 Used for Figure 3 The gain mapping 41 shown illustrates the relationship between the rotational speed of the brake motor and the gain. In this mapping, the faster the rotational speed of the brake motor (i.e., the easier it is to delay the reduction of the braking force of the brake), the larger the gain is calculated. Specifically, the gain is set to Y1 during the period when the rotational speed of the brake motor is from "0" to X1, and the gain increases from Y1 to Y2 during the period from X1 to X2. Furthermore, if the rotational speed of the brake motor exceeds X2, the gain is set to Y2.

[0109] When the braking motor rotates at a high speed, a delay occurs because the braking force is not reduced unless the braking motor is reversed, requiring time until the braking force decreases. However, by calculating the drive torque through a gain corresponding to the rotational speed of the braking motor and providing it to the slip wheel via feedforward control (FF control), the braking force applied to the slip wheel can be counteracted, suppressing initial slip. Thus, by determining the drive torque corresponding to the rotational state of the braking motor, initial slip can be effectively suppressed.

[0110] As a preferred example, in the vehicle control method executed by the control unit, during the deceleration of an electric vehicle driven by a friction brake motor, when the driving force is applied by the brake drive motor, the driving force is increased at a rotational speed of 20% (indicated by the arrow) of the maximum output of the friction brake motor, compared to when the rotational speed of the friction brake motor is zero.

[0111] Thus, the control unit controls the system in the following way: the greater the physical quantity related to the rotational speed of the friction brake drive motor, the greater the driving force applied when the slip ratio exceeds a specified threshold.

[0112] In addition, the gain Y1 of the motor used for braking, which is rotating from "0" to X1, is not a value that is "0". However, it can also be "0" or a mapping of the gain change when the rotational speed is "0" and when it is X1.

[0113] In addition, when the rotational speed of the braking motor is relatively fast (X2), the gain Y2 can also be "1".

[0114] Furthermore, in this mapping, it is set to a mapping that reduces the gain starting from the rotational speed of "0", but it can also be set to a mapping where the gain Y1 continues until the rotational speed is negative.

[0115] Figure 14 It is used for Figure 3 The diagram 42, illustrating the gain mapping, shows the relationship between the slip ratio change rate and the gain. In this mapping, the faster the slip ratio change rate moves in the positive direction (i.e., the deeper the wheel lock), the greater the calculated gain. Specifically, the gain increases from "0" to A1 as the slip ratio change rate moves from "0" to B1, and is set to A1 during the period from B1 to B2. Then, the gain increases further during the period from B2 to B3, and is set to A2 when the slip ratio change rate exceeds B3.

[0116] In this way, the control unit controls the driving force based on physical quantities related to the reference braking force, physical quantities related to the rotational speed of the friction braking drive motor, and the rate of change of the slip ratio.

[0117] Furthermore, since the braking motor has sufficient time to adjust the liner position when the slip ratio changes slowly, this mapping reduces the drive torque output by the braking drive motor, thereby suppressing unnecessary application of drive torque. Additionally, since the mapping is such that the smaller the slip ratio change rate, the lower the gain, the output of drive torque can be suppressed when the necessity to increase drive torque is low. By determining the drive torque based on the slip condition, unnecessary degradation of power consumption can be suppressed.

[0118] In addition, the gain A1 when the slip ratio changes from B1 to B2 is set to a value that is not "0", but can also be "0".

[0119] In addition, A1 continues until the slip ratio changes at a rate of B2, but the slip ratio can change at different values ​​at B1 and B2.

[0120] A2, which represents the gain when the slip ratio changes rapidly (at B3), can also be "1".

[0121] Furthermore, although it is set to a mapping such that the gain is "0" when the slip rate change rate is "0", it can also be set to a mapping such that the slip rate change rate when the gain is "0" is shifted in a positive or negative direction from 0.

[0122] [FF driving force reduced gain mapping]

[0123] Figure 15 It is used for Figure 3 The diagram 48, which illustrates the gain mapping, shows the relationship between the slip ratio change rate, slip ratio, and gain. This mapping, based on the slip ratio change rate and slip ratio, calculates the gain that reduces the reference value for increased driving force in scenarios where the ABS intervention of the braking drive motor is deemed to be reduced. When the slip ratio change rate is fast and the slip ratio is large, the gain is set to P1.

[0124] Control Department Reference Figure 17 The reduction slope of the driving force in the second control, described later, is calculated based on the rate of change of the slip ratio. Then, as the rate of change of the slip ratio and the slip ratio tend to decrease, the gain multiplied with the FF control can be reduced, and the braking force applied to the vehicle can be made quite close to that of the driver. Furthermore, when the slip ratio is considered to have decreased sufficiently, it is necessary to restore the driver's requested braking force; therefore, the driving torque is reduced based on the slip condition.

[0125] exist Figure 15In this context, P1 is preferably set to "1", but it can also be set to a value smaller than "1". Q2 is the value when the slip ratio change rate is relatively fast in the direction of increasing slip ratio. Q2 can be the rate at which the slip ratio change rate begins to change in the direction of decreasing slip ratio, for example, it can also be "0". Alternatively, Q2 can also be "0", but for example, the slip ratio change rate Q1 with a gain of "0" can be set to "0", and Q2 can be set to a value such that a slip ratio change rate in the positive direction appears.

[0126] The threshold R2 related to the slip ratio is set to a value larger than R1. For example, it can be set to be the same as the slip judgment threshold or smaller than the slip judgment threshold.

[0127] In addition, the threshold R1 related to the slip ratio is set to a value smaller than the threshold R2, for example, it can also be set to the same slip ratio as the one used to determine the end of ABS control.

[0128] [Gain mapping based on the state after glide judgment]

[0129] Figure 16 It is used for Figure 4 The diagram 51, which illustrates the gain mapping, shows the relationship between the elapsed time after slip determination, the rate of change of slip ratio, and the gain. This mapping is based on the rate of change of slip ratio and the elapsed time since the slip determination.

[0130] Based on the slip condition and the elapsed time since the slip, the braking force of the brake is allowed to be less than the driving force of the electric motor. This further assists in the recovery from slip when it takes time and when the slip ratio changes rapidly. The slip ratio change rate F1 is set at a point where the slip ratio change rate is faster in the direction of wheel lockup.

[0131] When the rate of change in the direction of increase of slip ratio is less than a specified value, the control unit refers to... Figure 18 The friction braking force in the first control described later is set to a control range that is greater than or equal to the braking force that is balanced with the driving force maintained in the first control before a specified time. If the slip ratio does not change to the decreasing side even after a specified time, the braking force that is less than the balanced braking force is set to the control range.

[0132] exist Figure 16 In this context, the slip ratio change rate indicates the tendency of the slip ratio to increase. Given the time elapsed since the slip judgment, the output gain is reduced by decreasing the gain mapping 51 from the state after the slip judgment, allowing the braking force of the brake to be less than the driving torque of the electric motor, thus aiding in recovery from wheel lock-up.

[0133] In this way, by allowing the braking force of the brake to be less than the driving torque of the electric motor based on the slip condition and the elapsed time since the slip, it is possible to suppress scenarios where the wheel does not tend to recover from wheel lock-up even after a specified time following slip detection.

[0134] In addition, the slip ratio change rate F2 can also be set to a value smaller than F1, for example, set to "0".

[0135] In addition, Figure 16 In the process, the elapsed time E1 after the slip judgment is set to a value that is not "0", but it can also be set to "0". Although it forms a mapping such that E1 is set to a value less than E2, E1 and E2 can also be set to the same value.

[0136] Furthermore, the gain when the slip rate changes at speed F1 and after time E1 is set to D1, just like the gain when the slip rate changes at speed F2 and after time E2, but different smaller values ​​can also be set.

[0137] Here, although the gain D1 is not explicitly stated, it can also be set to "1".

[0138] [Example illustrating the basic movements during sliding]

[0139] Next, in the structure described above, utilizing Figure 17 The timing diagram illustrates the basic actions during slip.

[0140] During slippage, the control unit performs a first control that maintains the driving force and reduces the friction braking force until the slip ratio changes to the decreasing side, a second control that maintains the friction braking force and reduces the driving force when the slip ratio changes to the decreasing side, and a third control that increases the friction braking force after reducing the driving force to a specified driving force ("0").

[0141] Friction braking electric motor (friction braking actuator 14) FL 14 FR 14 RL 14 RR At high rotational speeds, delays occur in responding to changes in conditions, leading to braking delays in the drive motor (IWM 12). FL 12 FR 12 RL 12 RR There are limitations in the driving force that can be output, making it difficult to increase the driving torque. Therefore, by staggering the actions of each actuator in time, it is possible to follow changes in conditions. In this way, either the brake motor or the brake drive motor can be in a state where it can operate quickly, and can respond rapidly to changes in slip ratio.

[0142] That is, the control unit sets the friction braking force in the first control to the third control to a control range that is above the braking force that is balanced with the driving force maintained in the first control.

[0143] Since the driving force is output by the brake drive motor, if the original ABS braking force reduction request is directly accepted, the drive wheels will accelerate due to the driving torque. Therefore, the braking force of the brake is controlled to operate only within a torque range greater than the torque output by the brake drive motor.

[0144] This prevents the drive wheels from being accelerated unnecessarily due to an unnecessary reduction in braking force caused by the brake motor.

[0145] At a specified moment t1 when the wheel speed is less than or equal to the slip judgment speed, the driving force of the brake drive motor is increased based on the rotational speed of the brake motor and the rate of change of the slip ratio at that moment. Then, the brake control device reduces the brake force based on the final ABS braking force reduction request value. At this time, the brake force is controlled within the range from the driver's requested braking force to the brake force balanced with the motor driving force to prevent acceleration.

[0146] At the moment t2 when the slippage changes to a tendency to recover, the braking force of the brake is maintained, causing the driving force of the electric motor to decrease rapidly. At the moment t3 when the driving force of the electric motor becomes "0" or less than or equal to a specified value, the braking driving force of the electric motor is maintained at that value, causing the braking force of the brake to increase towards the braking force requested by the driver. At the moment t4 when the braking force of the brake recovers to the braking force requested by the driver, the braking driving force of the electric motor changes towards the braking driving force requested by the driver.

[0147] Here, it is recorded that the braking force of the brake is maintained at time t2, but it can also be increased at a rate of change that is slow enough compared to the decrease in the driving force of the electric motor.

[0148] In this control system, during the initial stage of slippage, the torque is calculated based on the rotational speed of the brake motor, which corresponds to the index of the difficulty in eliminating the brake force (the difficulty in returning the brake pad position). Therefore, even when it is difficult to reduce the brake force, the increase in the slip ratio during the initial stage of slippage can be suppressed.

[0149] In this way, when wheel lock-up is detected (when ABS starts to detect it), the driving torque of the brake drive motor is calculated based on the rotational speed of the brake motor. As a result, since a large driving torque is applied in the early stage of slippage, the initial slippage can be effectively suppressed and the vehicle stability can be improved.

[0150] [This illustrates an example of action utilizing gain mapping based on the state after slip determination (when the slip rate changes slowly and recovery from slip takes time)]

[0151] Figure 18 This is a timing diagram showing the action when the gain mapping 51 based on the slip determination state is used. In this example, even after a specified time, if the slip change rate is not in the direction of slip rate reduction, the braking force of the braking motor is allowed to become less than the braking force that balances the driving force of the braking drive motor.

[0152] At the moment t1 when the specified wheel speed is less than or equal to the slip judgment speed, the driving force of the braking drive motor is increased according to the rotational speed of the braking motor and the slip ratio change rate at this time.

[0153] Then, the brake control unit reduces the brake force based on the final ABS braking force reduction request value. At this point, the brake force is controlled within a range from the driver's requested braking force to a braking force balanced with the electric motor's driving force, to prevent the vehicle from accelerating unnecessarily. Figure 18 At time t2, the braking force of the brake is reduced to a level that balances the driving force of the electric motor.

[0154] At time t3 after the slip judgment, the braking force of the brake is reduced to below the braking force of the brake that is balanced with the driving force of the electric motor.

[0155] At the moment t4 when the slippage changes to the tendency to recover, the braking force of the brake is maintained, so that the driving force of the electric motor is reduced rapidly.

[0156] At the moment t5 when the driving force of the electric motor becomes "0" or less than or equal to the specified value, the braking driving force of the electric motor is maintained at that value, so that the braking force of the brake is increased in the direction requested by the driver.

[0157] At the moment t6 when the braking force of the brake is restored to the braking force requested by the driver, the braking driving force of the electric motor is changed towards the braking driving force requested by the driver.

[0158] Therefore, slippage can be effectively suppressed even when recovery from slippage takes time.

[0159] [An example of an action where, in the gain mapping based on the state after slip determination, a specified time is set to "0" when the slip rate changes rapidly (when the slip rate changes rapidly)]

[0160] Figure 19 This is a timing diagram representing the action when the specified time for a rapid change in slip ratio is set to "0" in the gain mapping based on the slip-rate determination state. This example shows the action under the condition of a rapid change in slip ratio and a sharp increase in slip ratio.

[0161] That is, in the gain mapping based on the state after slip determination, when the slip ratio changes rapidly in the positive direction, the elapsed time after slip determination until the gain decreases is set to "0". Thus, even without waiting for a specified time, the braking force of the braking motor is allowed to decrease to a range less than the driving force of the braking drive motor. Therefore, even in scenarios where the slip ratio may increase, slip can be quickly suppressed.

[0162] When the rate of change in the direction of increase of slip ratio is greater than a predetermined value, the control unit sets the friction braking force in the first control to a control range, which is a braking force smaller than the braking force that is balanced with the driving force maintained in the first control.

[0163] When the slip ratio changes rapidly, slip can be suppressed more quickly by setting the braking force below the driving force, even without waiting for a specified time.

[0164] At time t1, the slip ratio changes rapidly enough in the direction of increasing slip. Therefore, based on the gain mapping of the state after slip judgment, the braking force of the brake is reduced without time elapsed (when E1=0 is set), allowing the braking force of the brake to be less than or equal to the driving force of the brake drive motor.

[0165] Then, at the moment t2 when the slippage changes to the tendency to recover, the braking force of the brake is maintained, so that the driving force of the electric motor is reduced rapidly.

[0166] At the moment t3 when the driving force of the electric motor becomes "0" or less than or equal to the specified value, the braking driving force of the electric motor is maintained at that value, so that the braking force of the brake is increased in the direction requested by the driver.

[0167] Furthermore, at the moment t4 when the braking force of the brake is restored to the braking force requested by the driver, the braking driving force of the electric motor is changed towards the braking driving force requested by the driver.

[0168] Therefore, even when the slip change rate is very fast, the initial slip can be suppressed more quickly.

[0169] [Example of increasing slip ratio again after a decrease]

[0170] Figure 20 This is a timing diagram showing the action when the slip ratio increases again after a period of decrease. This example illustrates the action when the slip ratio begins to decrease and then tends to increase again.

[0171] From time t1 to t3, it is the same as in other embodiments, but at time t4, during the process of increasing the braking force of the brake in the direction requested by the driver, the slip ratio change rate is detected to be increasing in the direction of increasing slip ratio again. Therefore, the FF driving force is reset, and slip suppression is implemented again at this time and thereafter in the same way as in other embodiments.

[0172] [Implementation method suitable for situations where slippage occurs during constant deceleration]

[0173] Figure 21 as well as Figure 22 This is a block diagram illustrating a structural example of a vehicle control device according to the second embodiment of the present invention. This example shows a structure where, even when the rotational speed of the brake motor is not high, assistance is still provided by the driving force of the brake drive motor. In these... Figure 21 and Figure 22 In, also with Figure 3 and Figure 4 Similarly, extraction Figure 1 The IWM 12 in the vehicle control unit 20 shown FL 12 FR 12 RL 12 RR (Electric motor for brake drive) and friction brake actuator 14 FL 14 FR 14 RL 14 RR The control unit of the (friction brake motor) is shown.

[0174] In this second embodiment, instead of the gain mapping 42 and multiplication unit 43 based on the slip ratio change rate in the first embodiment, a gain mapping 61 and selection unit 62 based on the slip ratio change rate and the liner position are provided. The larger of the outputs of gain mapping 41 and gain mapping 61 is selected by selection unit 62, multiplied with reference braking force in multiplication unit 44 to generate FF driving force, and input to FF driving force holding unit 45.

[0175] Other structures and Figure 2A , Figure 2B and Figure 3 Since they are the same, the same symbols are used to mark the same parts and their detailed descriptions are omitted.

[0176] When braking at a constant deceleration (when the rotational speed of the braking motor is not fast), if the change in slip ratio is faster in the direction of increasing slip ratio, there is a risk of insufficient responsiveness until the braking force is reduced.

[0177] Thus, a structure is formed in which the output value has a larger gain between the gain mapping based on the rotational speed of the braking motor and the gain mapping based on the slip ratio change rate and the liner position.

[0178] Therefore, even if the motor's rotational speed is low, in cases where the slip ratio changes rapidly or the brake force is strong, and it is assumed that a large amount of brake force must be quickly eliminated, the motor can output driving force through braking to accelerate the recovery from slip.

[0179] The physical quantity related to the reference braking force is a physical quantity related to the position of the friction plate (current value of the friction braking motor or friction braking torque). The control unit controls the driving force based on the larger of the adjustment gain based on the physical quantity related to the position of the friction plate, the physical quantity related to the rotational speed of the friction braking motor, and the adjustment gain obtained based on the physical quantity related to the position of the friction plate and the rate of change of the slip ratio.

[0180] By obtaining the larger of the output gain from the mapping based on the rotational speed of the friction braking motor and the mapping based on the rate of change of physical quantities and slip ratio related to the position of the friction pads, it is possible to output driving torque even when the braking force must be drastically reduced at low speeds.

[0181] As described above, even when the speed of the braking motor is low, when the vehicle enters a separated μ road surface, and the braking force must be reduced sharply due to a so-called μ change where the road surface μ of one of the left and right wheels changes from high μ to low μ, the initial slip can be suppressed by using the driving torque to assist in reducing the braking force applied to the wheels.

[0182] [Gain based on slip ratio change rate and liner position]

[0183] Figure 23 This diagram illustrates a gain mapping based on the slip ratio change rate and the pad position. The requirement for a larger output driving force in the brake drive motor is that the braking force is large, and consequently, the slip ratio change rate is large in the positive direction (the direction of increasing slip ratio). Therefore, in this mapping, the gain is determined based on the pad position and the slip ratio change rate.

[0184] M1 is the setting value when the rate of change of slip ratio is not fast in the direction of increasing slip ratio, and is set to a value below "0". M2 is the setting value when the rate of change of slip ratio is faster than M1 in the direction of increasing slip ratio, and is set to a value at least greater than M1.

[0185] L1, a setting related to the position of the brake pads, is the value when the brake is not depressed that much, while L2 is the value when the brake is considered to be depressed slightly more.

[0186] K1 can also be set to "1", and K1 and K2 can be set to different values, or they can both be set to the same value.

[0187] [Other implementations suitable for situations where slippage occurs during constant deceleration]

[0188] Figure 24 as well as Figure 25 This is a block diagram illustrating a structural example of a vehicle control device according to the third embodiment of the present invention. This example is another structural example in which assistance is provided by the driving force of the brake drive motor even when the rotational speed of the brake motor is not fast. In these... Figure 24 as well as Figure 25 In, also with Figure 3 as well as Figure 4 Similarly, extraction Figure 1 The IWM 12 in the vehicle control unit 20 shown FL 12 FR 12 RL 12 RR (Electric motor for brake drive) and friction brake actuator 14 FL 14 FR 14 RL 14 RR The control unit of the (friction brake motor) is shown.

[0189] In this third embodiment, in addition to the structure of the first embodiment, a gain mapping 63 based on the change in the reduction request value, a selection unit 64, and an absolute value calculation unit 65 are also provided. An ABS braking force reduction request value (negative value) is input to the gain mapping 63, and its output, along with the output of the gain mapping 41, is input to the selection unit 64, selecting the larger one. The absolute value calculation unit 65 obtains the absolute value of the ABS braking force reduction request value, and the multiplication unit 43 multiplies this absolute value with the output of the gain mapping selected by the selection unit 64.

[0190] Other structures and Figure 2A , Figure 2B and Figure 3 Since they are the same, the same symbols are used to mark the same parts and their detailed descriptions are omitted.

[0191] The physical quantity related to the reference braking force is the reduction request value of the braking force of the anti-lock braking system. The control unit controls the driving force based on the larger of the reduction request value of the braking force of the anti-lock braking system, the adjustment gain based on the physical quantity related to the rotational speed of the friction brake motor, and the adjustment gain obtained based on the change of the reduction request value of the braking force of the anti-lock braking system.

[0192] Since the reduction in braking force of anti-lock braking is calculated based on the current braking force, the rate of change of slip ratio, and slip ratio, the same effect can be achieved when the braking force reduction request value of anti-lock braking is implemented.

[0193] In this way, the same effect as the main concept of this patent can be achieved when the requested value of ABS braking force is reduced.

[0194] When braking at a constant deceleration (when the rotational speed of the braking motor is not fast), if the change in slip ratio is faster in the direction of increasing slip ratio, there is a risk of insufficient responsiveness until the braking force is reduced.

[0195] Therefore, in this embodiment, the FF driving force is calculated based on the ABS braking force reduction request value, not the reference braking force. Furthermore, the output is configured to have a larger gain than the output mapped based on the change in the ABS braking force reduction request value and the output mapped based on the rotational speed of the brake motor.

[0196] Therefore, even if the rotational speed of the electric motor is low, the change in the required value of ABS braking force reduction is relatively large. In cases where it is necessary to quickly eliminate a large amount of braking force, the driving force can be output by the electric motor to accelerate the recovery from slippage.

[0197] Here, the change in the ABS braking force reduction request value can be the difference between the previous ABS braking force reduction request value and the current ABS braking force reduction request value, or it can be calculated based on the derivative.

[0198] [Gain mapping based on reducing changes in request values]

[0199] Figure 26 It is a diagram used to illustrate the gain mapping based on the amount of change in the reduced request value.

[0200] The greater the change in the requested braking force reduction value, the greater the change in the braking driving force of the current braking drive motor and the braking force of the brake. Therefore, in this mapping, we define a mapping where the greater the change in the requested braking force reduction value, the greater the gain.

[0201] Furthermore, in this mapping, the gain H1 is set to a value other than "0", but it can also be set to "0", or it can be a mapping where G2 is also set to "0". Also, H2 is not explicitly stated, but it can also be set to 1.

[0202] In addition, the change in the ABS braking force reduction request value can also be the difference between the previous ABS braking force reduction request value and the current ABS braking force reduction request value, or it can be calculated based on the derivative.

[0203] As explained above, according to the present invention, when the rotational speed of the brake motor is measured during a wheel lock-up detection, and the time required to reduce the braking force of the brake is determined based on the rotational speed of the brake motor, the driving torque of the brake drive motor is calculated based on the gain determined corresponding to the rotational speed of the brake motor. As a result, initial slippage can be effectively and quickly suppressed, thereby improving vehicle stability.

[0204] Furthermore, the structures, methods, etc., described in the above embodiments are merely schematic representations to the extent that the present invention can be understood and practiced. Therefore, the present invention is not limited to the described embodiments, and various modifications can be made without departing from the scope of the technical concept shown in the claims.

[0205] Explanation of reference numerals in the attached figures

[0206] 10…electric vehicles; 11 FL 11 FR …front wheel; 11 RL 11 RR …rear wheels; 12 FL 12 FR 12 RL 12 RR …IWM; 13 FL 13 FR 13 RL 13 RR …IWM uses rotary transformers; 14 FL 14 FR 14 RL 14 RR …friction brake actuator (electric motor for friction braking); 14a…electric motor for braking (electric motor for friction braking); 14b…ball screw mechanism; 14c…brake pad (friction pad); 14d…rotary transformer for brake motor; 15 FL 15 FR 15 RL 15 RR …Wheel speed sensor; 17…Low-voltage battery; 18…High-voltage battery; 19…DC-DC converter; 20…Vehicle control unit; 21…Brake control unit; 22 FL ,twenty two FR ,twenty two RL ,twenty two RR …IWM control unit; 23…Battery control unit; 24…In-vehicle communication circuit (CAN bus); 28, 28 FL 28 FR 28 RL 28RR …brake rotor (rotor).

Claims

1. A vehicle control device, the vehicle control device being disposed in a vehicle, the vehicle having: a plurality of friction braking devices, wherein friction pads are pressed against rotors rotating together with the wheels of the vehicle by being driven by friction braking motors, thereby applying friction braking force to each wheel; and a plurality of brake drive motors, wherein braking drive force is applied to each wheel. The vehicle control device includes a control unit that controls the plurality of friction braking motors and the plurality of brake drive motors. The control unit performs: Obtain the requested braking force applied to each of the wheels. When the vehicle is decelerated by driving the friction braking motor based on the requested braking force, the slip ratio of each wheel is obtained. When the braking drive motor applies a driving force to the slip wheel whose slip ratio exceeds a predetermined threshold, The driving force is controlled based on the magnitude of the friction braking force and the rate of change of the friction braking force.

2. The vehicle control device according to claim 1, wherein, The magnitude of the frictional braking force is determined based on a physical quantity related to a reference braking force based on the requested braking force. The rate of change of the friction braking force is determined based on a physical quantity related to the rotational speed of the friction braking motor.

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

4. The vehicle control device according to claim 3, wherein, The control unit controls the slip ratio in such a way that the greater the rate of change of the slip ratio, the greater the driving force applied when the slip ratio exceeds a predetermined threshold.

5. The vehicle control device according to claim 2, wherein, The control unit controls the system such that the greater the physical quantity related to the rotational speed of the friction braking motor, the greater the driving force applied when the slip ratio exceeds a predetermined threshold.

6. The vehicle control device according to claim 2, wherein, The control unit performs the first control, the second control, and the third control. In the first control, the driving force is maintained and the frictional braking force is reduced until the slip ratio changes towards the decreasing side. In the second control, when the slip ratio changes towards the decreasing side, the frictional braking force is maintained while the driving force is reduced. In the third control, after the driving force is reduced to a predetermined driving force, the friction braking force is increased.

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

8. The vehicle control device according to claim 6, wherein, The control unit calculates the reduction slope of the driving force in the second control based on the rate of change of the slip ratio.

9. The vehicle control device according to claim 6, wherein, When the rate of change in the direction of increase of the slip ratio is less than a specified value, The control unit sets the friction braking force in the first control to a control range that is greater than or equal to the braking force balanced with the driving force maintained in the first control until a predetermined time has elapsed. If the slip ratio does not change towards the decreasing side even after the specified time, the control range is set up up to a braking force smaller than the equilibrium braking force.

10. The vehicle control device according to claim 6, wherein, When the rate of change in the direction of increase of the slip ratio is greater than a specified value, The control unit sets the friction braking force in the first control within a control range that is smaller than the braking force balanced with the driving force maintained in the first control.

11. The vehicle control device according to claim 2, wherein, The physical quantity related to the reference braking force is a physical quantity related to the position of the friction plate. The control unit, based on physical quantities related to the position of the friction plate, and The driving force is controlled based on the larger of the adjustment gain obtained from the adjustment gain of a physical quantity related to the rotational speed of the friction braking motor and the adjustment gain obtained from the adjustment gain obtained from the physical quantity related to the position of the friction plate and the rate of change of the slip ratio.

12. The vehicle control device according to claim 2, wherein, The physical quantity associated with the reference braking force is the requested reduction value of the anti-lock braking force. The control unit, based on the request value for reducing the braking force of the anti-lock braking system, and The driving force is controlled by the larger of the adjustment gain based on the adjustment gain of a physical quantity related to the rotational speed of the friction braking motor and the adjustment gain based on the change in the braking force reduction request value of the anti-lock braking system.

13. A vehicle control method, wherein the vehicle control method is executed by a control unit mounted on a vehicle, the vehicle having: a plurality of friction braking devices, independently arranged relative to each wheel of the vehicle, wherein friction pads are pressed against rotors rotating together with the wheels of the vehicle by being driven by friction braking motors, thereby applying friction braking force to each wheel; and a plurality of brake drive motors, independently arranged relative to each wheel, applying braking drive force to each wheel. During vehicle deceleration driven by the friction braking motor, when a driving force is applied by the braking drive motor, Compared to a friction braking motor with a rotational speed of zero, the driving force is increased at a rotational speed of 20% of the maximum output of the friction braking motor.

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