Regenerative cooperation control device and regenerative cooperation control method

Abstract

In the present invention, a regenerative cooperation control device comprises: a switching control unit (M17) that is configured so as to execute switching control for switching regenerative braking force to friction braking force in situations where regenerative braking force is applied to a vehicle; and a correction unit (M19) that is configured so as to execute a correction process for correcting the braking force that has the higher response speed between the regenerative braking force and the friction braking force so such that the magnitude of the difference between the deceleration rate of the vehicle and a target deceleration rate will decrease when the switching control is being executed.

Description

Regenerative Coordination Control Device and Regenerative Coordination Control Method

[0001] The present disclosure relates to a regenerative cooperative control device and a regenerative cooperative control method.

[0002] Patent Document 1 discloses a regenerative braking coordination control device that controls the regenerative braking force and friction braking force applied to a vehicle. When the vehicle speed falls below a predetermined speed while regenerative braking force is being applied, this regenerative braking coordination control device executes switching control to gradually decrease the regenerative braking force and gradually increase the friction braking force.

[0003] International Publication No. 2010 / 128652

[0004] The response speeds of the regenerative braking force and the frictional braking force are different, so that during execution of the switching control, the sum of the actual values ​​of the regenerative braking force and the frictional braking force may vary, which may cause fluctuations in the deceleration of the vehicle.

[0005] A regenerative cooperative control device according to one aspect of the present disclosure is applied to a vehicle including a regenerative braking device configured to apply a regenerative braking force and a friction braking device configured to apply a friction braking force. The regenerative cooperative control device includes: a switching control unit configured to execute switching control for switching the regenerative braking force with the friction braking force when the regenerative braking force is being applied to the vehicle; and a correction unit configured to execute a correction process when the switching control is being executed to correct one of the regenerative braking force and the friction braking force, which has a higher response speed, so as to reduce the magnitude of the difference between the deceleration of the vehicle and a target deceleration.

[0006] A regenerative cooperative control method according to another aspect of the present disclosure is applied to a vehicle including a regenerative braking device configured to apply a regenerative braking force and a friction braking device configured to apply a friction braking force, the regenerative cooperative control method including: executing a substitution control for substituting the regenerative braking force with the friction braking force under a condition in which the regenerative braking force is being applied to the vehicle; and executing a correction process, while the substitution control is being executed, for correcting one of the regenerative braking force and the friction braking force, which has a higher response speed, so as to reduce the magnitude of the difference between the deceleration of the vehicle and a target deceleration.

[0007] FIG. 1 is a schematic diagram showing a vehicle equipped with a regeneration coordination control device according to an embodiment. FIG. 2 is a block diagram showing the functional configuration of the regeneration coordination control device of FIG. 1. FIG. 3 is a map showing the relationship between a target deceleration and a starting vehicle speed for switching control, used by the regeneration coordination control device of FIG. 1. FIG. 4 is a map used by the regeneration coordination control device of FIG. 1 for determining an increase in a friction braking force command value when preliminary switching control is performed. FIG. 5 is a flowchart showing the processing flow when applying braking force to a vehicle in the regeneration coordination control device of FIG. 1. FIG. 6 is a flowchart showing the processing flow when switching control is performed in the regeneration coordination control device of FIG. 1. FIG. 7 is a flowchart showing the processing flow when the vehicle is stopped in the regeneration coordination control device of FIG. 1. FIG. 8 is a timing chart showing the application of braking force to stop the vehicle of FIG. 1.

[0008] An embodiment of a regenerative cooperative control device and a regenerative cooperative control method will be described below with reference to FIGS. 1 to 8. FIG. 1 illustrates a vehicle 10 equipped with a regenerative cooperative control device 100. The vehicle 10 includes a brake operating member 11, a plurality of wheels 12, a plurality of friction brakes 20, a friction braking device 30, a motor generator 40, and a plurality of sensors. The brake operating member 11 is a member operated by the driver to decelerate the vehicle 10. An example of the brake operating member 11 is a brake pedal. FIG. 1 illustrates only one wheel 12 and one friction brake 20 out of the plurality of wheels 12 and friction brakes 20.

[0009] <Friction Brake> The multiple friction brakes 20 operate to apply a friction braking force to the corresponding wheels 12. The friction brakes 20 have wheel cylinders 21, rotating bodies 22, and friction materials 23. The rotating bodies 22 rotate integrally with the wheels 12. Therefore, the friction materials 23 are pressed against the rotating bodies 22, thereby applying a friction braking force to the wheels 12. The higher the hydraulic pressure in the wheel cylinders 21, the greater the force pressing the friction materials 23 against the rotating bodies 22. Therefore, with the friction brakes 20, the higher the hydraulic pressure in the wheel cylinders 21, the greater the friction braking force that can be applied to the wheels 12.

[0010] <Friction Braking Device> The friction braking device 30 has a discharge source 31 that discharges brake fluid. Examples of the discharge source 31 include an electric pump and an electric cylinder. The brake fluid discharged from the discharge source 31 is supplied to the wheel cylinder 21, thereby applying a friction braking force to the wheel 12.

[0011] <Motor Generator> The motor generator 40 is a power source for the vehicle 10. When the motor generator 40 functions as an electric motor, it applies driving force to the wheels 12. The driving force in the rotational direction of the wheels 12 when moving the vehicle 10 forward is called the "forward driving force." The driving force in the rotational direction of the wheels 12 when moving the vehicle 10 backward is called the "reverse driving force." The motor generator 40 can also function as a generator. In this case, a regenerative braking force corresponding to the amount of power generated by the motor generator 40 is applied to the vehicle 10. In other words, the motor generator 40 functions as a regenerative braking device that applies regenerative braking force to the vehicle 10, and also functions as a driving device that can apply driving force to the wheels 12 of the vehicle 10. The motor generator 40 also corresponds to a "braking / driving device."

[0012] <Sensors> The multiple sensors output detection signals corresponding to the detection results to the regenerative cooperative control device 100. The multiple sensors include a brake sensor 51, multiple wheel speed sensors 52, an acceleration sensor 53, and a motor angle sensor 54. The brake sensor 51 detects operation-related information related to the operation of the brake operating member 11 by the driver. The brake sensor 51 may be a stroke sensor that detects the amount of operation of the brake operating member 11 by the driver as the operation-related information, or may be a sensor that detects the operating force of the brake operating member 11 by the driver as the operation-related information. The wheel speed sensors 52 output signals corresponding to the rotational speeds of the corresponding wheels 12. The acceleration sensor 53 detects the longitudinal acceleration of the vehicle 10. The motor angle sensor 54 detects the rotational angle of the rotor of the motor-generator 40.

[0013] The rotation speed of the wheels 12 based on the detection signal of the wheel speed sensor 52 is referred to as the "wheel speed VW." The acceleration of the vehicle 10 based on the detection signal of the acceleration sensor 53 is referred to as the "longitudinal acceleration GX." The rotation speed of the rotor of the motor generator 40 based on the detection signal of the motor angle sensor 54 is referred to as the "motor rotation speed Nmt."

[0014] <Regenerative Cooperative Control Device> The regenerative cooperative control device 100 has a friction braking control unit 60 that controls the friction braking device 30, and a motor control unit 70 that controls the motor generator 40. The control units 60, 70 are configured to be able to send and receive information to and from each other. An example of the control units 60, 70 is an electronic control device.

[0015] The friction braking control unit 60 has a processing circuit 61. The processing circuit 61 has a CPU 62 and a memory 63. The memory 63 stores a control program executed by the CPU 62. The CPU 62 executes the control program, causing the processing circuit 61 to control the friction braking device 30.

[0016] The motor control unit 70 has a processing circuit 71. The processing circuit 71 has a CPU 72 and a memory 73. The memory 73 stores a control program to be executed by the CPU 72. The CPU 72 executes the control program, causing the processing circuit 71 to control the motor generator 40.

[0017] <Functional Configuration of Regenerative Cooperative Control Device> The CPU 62 executes the control program in the memory 63, causing the processing circuit 61 to function as a plurality of functional units. The CPU 72 executes the control program in the memory 73, causing the processing circuit 71 to function as a plurality of functional units.

[0018] 2, the multiple functional units include a target deceleration setting unit M11, a regenerative braking coordination control unit M13, a start vehicle speed setting unit M15, a switching control unit M17, a correction unit M19, a friction braking control unit M21, a regenerative braking control unit M23, and a drive control unit M25. The processing circuit 61 of the friction braking control unit 60 functions as the target deceleration setting unit M11, the regenerative braking coordination control unit M13, the start vehicle speed setting unit M15, the switching control unit M17, and the friction braking control unit M21. The processing circuit 71 of the motor control unit 70 functions as the correction unit M19, the regenerative braking control unit M23, and the drive control unit M25. The drive control unit M25 corresponds to the "brake / drive control unit."

[0019] <Target Deceleration Setting Unit> When there is a braking request, the target deceleration setting unit M11 sets a target deceleration DVSTr, which is a target for the deceleration of the vehicle 10. The target deceleration setting unit M11 determines that there is a braking request when it detects that the brake operating member 11 is being operated or when there is a deceleration request from another control device. For example, when the brake operating member 11 is being operated, the target deceleration setting unit M11 sets the target deceleration DVSTr based on the detection signal of the brake sensor 51.

[0020] <Regenerative Cooperative Control Unit> The regenerative cooperative control unit M13 executes regenerative cooperative processing to derive a regenerative braking force command value FxRTr and a frictional braking force command value FxMTr based on the target deceleration DVSTr. The regenerative braking force command value FxRTr is a command value for the regenerative braking force FxR. The frictional braking force command value FxMTr is a command value for the frictional braking force FxM.

[0021] The regenerative coordination control unit M13 converts the target deceleration DVSTr into a target braking force FxTr. The target braking force FxTr is a target for the braking force Fx of the vehicle 10. Then, in the regenerative coordination processing, the regenerative coordination control unit M13 derives a regenerative braking force command value FxRTr and a frictional braking force command value FxMTr so that the sum of the regenerative braking force command value FxRTr and the frictional braking force command value FxMTr is equal to the target braking force FxTr. In this case, it is preferable that the regenerative coordination control unit M13 derives the regenerative braking force command value FxRTr and the frictional braking force command value FxMTr so that the regenerative braking force command value FxRTr is as large as possible.

[0022] <Start vehicle speed setting unit> The start vehicle speed setting unit M15 sets a start vehicle speed VS1Th, which is the vehicle speed at which the switching control, which will be described later, is started. The start vehicle speed setting unit M15 sets the start vehicle speed VS1Th to a smaller vehicle speed as the target deceleration DVSTr is lower. As will be described in detail later, the switching control is a control that is performed just before the vehicle 10 is stopped. Therefore, the start vehicle speed VS1Th is set to, for example, 10 km / h or less.

[0023] For example, the start vehicle speed setting unit M15 sets the start vehicle speed VS1Th using the map shown in FIG. 3. In this case, if the target deceleration DVSTr is less than the first deceleration DVS1, the start vehicle speed setting unit M15 sets the start vehicle speed VS1Th to the first vehicle speed VS1. If the target deceleration DVSTr is equal to or greater than the second deceleration DVS2, the start vehicle speed setting unit M15 sets the start vehicle speed VS1Th to the second vehicle speed VS2. The second deceleration DVS2 is greater than the first deceleration DVS1. The second vehicle speed VS2 is greater than the first vehicle speed VS1. If the target deceleration DVSTr is equal to or greater than the first deceleration DVS1 and less than the second deceleration DVS2, the start vehicle speed setting unit M15 sets the start vehicle speed VS1Th to a larger value as the target deceleration DVSTr is greater.

[0024] 2, the switching control unit M17 executes switching control to switch the regenerative braking force FxR to the frictional braking force FxM under the condition that the regenerative braking force FxR is being applied to the vehicle 10. The switching control unit M17 starts the switching control when the vehicle speed VS becomes equal to or lower than the start vehicle speed VS1Th. Note that the vehicle speed VS is a vehicle speed derived based on the motor rotation speed Nmt.

[0025] The switching control includes a main switching control and a preliminary switching control that reduces the rate of decrease of the regenerative braking force FxR compared to when the main switching control is executed. The switching control unit M17 executes the main switching control after executing the preliminary switching control.

[0026] Specifically, when the vehicle speed VS becomes equal to or lower than the start vehicle speed VS1Th, the switching control unit M17 starts the preliminary switching control. In the preliminary switching control, the switching control unit M17 gradually increases the frictional braking force command value FxMTr and gradually decreases the regenerative braking force command value FxRTr.

[0027] The process of deriving the command values ​​FxRTr and FxMTr during the preliminary switching control will be described with reference to Fig. 4. Fig. 4 is a map showing the relationship between the vehicle speed VS and the pre-charge frictional braking force FxMp. The pre-charge frictional braking force FxMp is the amount of increase in the frictional braking force command value FxMTr during execution of the preliminary switching control.

[0028] In the map shown in Fig. 4, when the vehicle speed VS is greater than the start vehicle speed VS1Th, the pre-charge frictional braking force FxMp is 0 (zero). The switch vehicle speed VS2Th is a vehicle speed lower than the start vehicle speed VS1Th. The switch vehicle speed VS2Th is set to, for example, a vehicle speed that serves as a criterion for determining whether the vehicle 10 is about to stop. When the vehicle speed VS is equal to or lower than the switch vehicle speed VS2Th, the pre-charge frictional braking force FxMp is maintained at a predetermined braking force FxMp1. When the vehicle speed VS is greater than the switch vehicle speed VS2Th and equal to or lower than the start vehicle speed VS1Th, the pre-charge frictional braking force FxMp increases as the vehicle speed VS decreases.

[0029] When the friction braking force FxM is increased from 0 (zero), a response delay in the friction braking force FxM is likely to occur in the initial stage of the increase. Therefore, a friction braking force that serves as a criterion for determining whether a response delay is likely to occur is set as the predetermined braking force FxMp1. The braking force range in which a response delay in the friction braking force FxM occurs is determined by the specifications of the friction braking device 30 and the friction brake 20, etc.

[0030] When the start vehicle speed VS1Th is set by the start vehicle speed setting unit M15, the switching control unit M17 creates a map as shown in FIG. 4 . The switch vehicle speed VS2Th is a preset vehicle speed, and the predetermined braking force FxMp1 is a preset magnitude. Therefore, the switching control unit M17 sets the slope of the map line Lmap shown in FIG. 4 from the start vehicle speed VS1Th to the switch vehicle speed VS2Th, depending on the start vehicle speed VS1Th. The slope of the map line Lmap represents the increase in the pre-charge friction braking force FxMp relative to the decrease in the vehicle speed VS. This allows the switching control unit M17 to create the map. Note that the switching control unit M17 updates the map each time the start vehicle speed VS1Th is updated. However, if the switching control unit M17 starts switching control because the vehicle speed VS becomes equal to or lower than the start vehicle speed VS1Th, the switching control unit M17 stops updating the map.

[0031] In the preliminary switching control, the switching control unit M17 obtains the pre-charge friction braking force FxMp corresponding to the vehicle speed VS from the map shown in FIG. 4. Then, the switching control unit M17 derives the value obtained by subtracting the pre-charge friction braking force FxMp from the regenerative braking force command value FxRTr as the latest value of the regenerative braking force command value FxRTr. The switching control unit M17 also derives the value obtained by subtracting the latest value of the regenerative braking force command value FxRTr from the target braking force FxTr as the latest value of the friction braking force command value FxMTr.

[0032] When the vehicle speed VS becomes equal to or lower than the switching vehicle speed VS2Th during the execution of the preliminary switching control, the switching control unit M17 terminates the preliminary switching control and starts the main switching control. In the main switching control, the switching control unit M17 derives the regenerative braking force command value FxRTr and the friction braking force command value FxMTr so as to satisfy the following conditions (A1) and (A2).

[0033] (A1) When the vehicle speed VS becomes 0 (zero), the regenerative braking force command value FxRTr becomes 0 (zero). (A2) The regenerative braking force command value FxRTr is decreased at a constant gradient, while the frictional braking force command value FxMTr is increased at the same gradient.

[0034] <Correction unit> Returning to Figure 2, when switching control is being executed, the correction unit M19 performs a correction process to correct the braking force with the higher response speed, either the regenerative braking force FxR or the frictional braking force FxM, so that the magnitude of the difference ΔDVS between the deceleration DVS of the vehicle 10 and the target deceleration DVSTr becomes smaller.

[0035] Here, the friction braking device 30 is a hydraulic braking device that applies a friction braking force FxM to the vehicle 10 by increasing the hydraulic pressure in the wheel cylinder 21. Therefore, particularly when the braking force is small, the response speed of the friction braking force FxM is slower than the response speed of the regenerative braking force FxR.

[0036] Therefore, in the correction process, the correction unit M19 corrects the regenerative braking force command value FxRTr, of the regenerative braking force command value FxRTr and the frictional braking force command value FxMTr derived by the switching control unit M17, in accordance with the difference ΔDVS. For example, the correction unit M19 corrects the regenerative braking force command value FxRTr by feedback control using the difference ΔDVS as an input.

[0037] The correction unit M19 starts the correction process when the switching control is started and ends the correction process immediately before the regenerative braking force FxR becomes 0 (zero). As described above, the switching control includes the preliminary switching control and the main switching control. Therefore, it is preferable that the correction unit M19 ends the correction process when the switching control switches from the preliminary switching control to the main switching control.

[0038] <Friction Braking Control Unit> The friction braking control unit M21 controls the friction braking device 30. Specifically, the friction braking control unit M21 adjusts the friction braking force FxM by operating the friction braking device 30 based on the friction braking force command value FxMTr.

[0039] <Regenerative braking control unit> The regenerative braking control unit M23 controls the regenerative braking force FxR by causing the motor generator 40 to function as a generator. Specifically, the regenerative braking control unit M23 controls the inverter of the motor generator 40 so that the amount of power generated by the motor generator 40 increases as the regenerative braking force command value FxRTr increases. In this way, the regenerative braking control unit M23 adjusts the regenerative braking force FxR in accordance with the regenerative braking force command value FxRTr.

[0040] <Drive Control Unit> When the vehicle 10 is stopped, the drive control unit M25 controls the drive force Fd by causing the motor generator 40 to function as an electric motor. For example, when the vehicle 10 is stopped on a downhill road, the drive control unit M25 operates the motor generator 40 so that a drive force Fd in the backward direction is applied to the wheels 12. When the vehicle 10 is stopped on an uphill road, the drive control unit M25 operates the motor generator 40 so that a drive force Fd in the forward direction is applied to the wheels 12. When the road surface on which the vehicle 10 is stopped is not a slope, the drive control unit M25 controls the motor generator 40 so that the drive force Fd becomes 0 (zero).

[0041] However, the driver's operating force on the brake operating member 11 may be reduced after the vehicle 10 has stopped. In this case, the drive control unit M25 operates the motor generator 40 so that a driving force Fd corresponding to the creep torque is applied to the wheels 12.

[0042] <Braking Process> Referring to Figure 5, the braking process, which is the flow of processing in the regeneration coordination control device 100 when adjusting the braking force Fx of the vehicle, will be described. The braking process is repeatedly executed for each predetermined control cycle. However, when the execution condition for the switching control is met, the execution of the braking process is stopped.

[0043] In step S11, the regenerative cooperative control device 100 determines whether or not a braking request is made. In this embodiment, the processing of step S11 is performed by the processing circuit 61 of the friction braking control unit 60 functioning as the target deceleration setting unit M11. If the regenerative cooperative control device 100 determines that a braking request is made (S11: YES), the processing proceeds to step S13. On the other hand, if the regenerative cooperative control device 100 determines that a braking request is not made (S11: NO), the regenerative cooperative control device 100 temporarily terminates the braking processing.

[0044] In step S13, the regenerative braking coordination control device 100 sets the target deceleration DVSTr. In this embodiment, the processing circuit 61 of the friction braking control unit 60 functions as a target deceleration setting section M11, thereby executing the processing of step S13.

[0045] In the following step S15, the regenerative coordination controller 100 converts the target deceleration DVSTr into a target braking force FxTr. In the next step S17, the regenerative coordination controller 100 derives as the regenerative braking force command value FxRTr the smaller of the value obtained by subtracting the frictional braking force command value FxMTr from the target braking force FxTr or the regenerative braking force upper limit value FxRmax. The regenerative braking force upper limit value FxRmax is the maximum value of the regenerative braking force FxR that the motor-generator 40 can apply to the vehicle 10. In the following step S19, the regenerative coordination controller 100 derives as the frictional braking force command value FxMTr the larger of 0 (zero) or the value obtained by subtracting the regenerative braking force command value FxRTr from the target braking force FxTr. In this embodiment, the processing circuit 61 of the friction braking control unit 60 functions as the regenerative braking coordination control unit M13, thereby executing the processes of steps S17 and S19.

[0046] In step S21, the regenerative cooperative control device 100 operates the motor-generator 40 based on the regenerative braking force command value FxRTr, and operates the friction braking device 30 based on the friction braking force command value FxMTr. In this embodiment, the processing circuit 71 of the motor control unit 70 functions as the regenerative braking control unit M23, thereby executing the process of controlling the motor-generator 40 in step S21. The processing circuit 61 of the friction braking control unit 60 functions as the friction braking control unit M21, thereby executing the process of controlling the friction braking device 30 in step S21.

[0047] In step S23, the regenerative braking cooperative control device 100 sets the vehicle speed corresponding to the target deceleration DVSTr as the starting vehicle speed VS1Th by using, for example, the map shown in Fig. 3. In this embodiment, the processing circuit 61 of the friction braking control unit 60 functions as the starting vehicle speed setting section M15, thereby executing the processing of step S23.

[0048] In the next step S25, the regeneration coordination control device 100 determines whether the vehicle speed VS is equal to or less than the start vehicle speed VS1Th. If the vehicle speed VS is equal to or less than the start vehicle speed VS1Th (S25: YES), the regeneration coordination control device 100 determines that the execution condition for the switching control is met and terminates the braking process.

[0049] On the other hand, if the vehicle speed VS is greater than the starting vehicle speed VS1Th (S25: NO), the regeneration coordination control device 100 determines that the execution condition for the switching control is not met and temporarily terminates the braking process. In this case, the regeneration coordination control device 100 continues to repeatedly execute the braking process.

[0050] <Swapping During Processing> The swapping during processing, which is a processing flow in the regeneration coordination control device 100 when swapping control is executed, will be described with reference to Fig. 6. The swapping during processing is repeatedly executed for each predetermined control cycle if the vehicle 10 has not yet stopped and the execution conditions for swapping control are met.

[0051] In step S43, the regenerative coordination control device 100 determines whether the vehicle speed VS is greater than the switching vehicle speed VS2Th. If the regenerative coordination control device 100 determines that the vehicle speed VS is greater than the switching vehicle speed VS2Th (S43: YES), the regenerative coordination control device 100 executes preliminary switching control. On the other hand, if the regenerative coordination control device 100 determines that the vehicle speed VS is equal to or less than the switching vehicle speed VS2Th (S43: NO), the regenerative coordination control device 100 executes main switching control.

[0052] The flow of the preliminary switching control process will be described. In step S45, the regenerative coordination control device 100 uses a map such as that shown in FIG. 4 to set a braking force corresponding to the vehicle speed VS as the pre-charge friction braking force FxMp. In step S47, the regenerative coordination control device 100 derives the smaller of the value obtained by subtracting the pre-charge friction braking force FxMp from the target braking force FxTr and the regenerative braking force upper limit value FxRmax as the regenerative braking force command value FxRTr. In step S49, the regenerative coordination control device 100 derives the value obtained by subtracting the regenerative braking force command value FxRTr from the target braking force FxTr as the friction braking force command value FxMTr. In this embodiment, the processing circuit 61 of the friction braking control unit 60 functions as the switching control unit M17, thereby executing the processes of steps S45 to S49.

[0053] In the next step S51, the regenerative coordination controller 100 derives a difference ΔDVS between the target deceleration DVSTr and the deceleration DVS by subtracting the deceleration DVS of the vehicle 10 from the target deceleration DVSTr. In the following step S53, the regenerative coordination controller 100 executes a correction process to correct the regenerative braking force command value FxRTr so as to reduce the magnitude of the difference ΔDVS. In this embodiment, the processing circuit 71 of the motor control unit 70 functions as the correction unit M19, thereby executing the processes of steps S51 and S53. Thereafter, the regenerative coordination controller 100 proceeds to step S59.

[0054] The flow of the switching control process will be described. In step S55, the regenerative coordination control device 100 subtracts the switching braking force ΔFx2 from the regenerative braking force command value FxRTr to obtain the latest value of the regenerative braking force command value FxRTr. The switching braking force ΔFx2 is set to a magnitude that satisfies the above conditions (A1) and (A2). In step S57, the regenerative coordination control device 100 subtracts the latest value of the regenerative braking force command value FxRTr from the target braking force FxTr to obtain the frictional braking force command value FxMTr. In this embodiment, the processing circuit 61 of the frictional braking control unit 60 functions as the switching control unit M17, thereby executing steps S55 and S57. The regenerative coordination control device 100 then proceeds to step S59.

[0055] In step S59, the regenerative coordination controller 100 operates the motor-generator 40 based on the regenerative braking force command value FxRTr, and operates the friction braking device 30 based on the friction braking force command value FxMTr. In this embodiment, the processing circuit 71 of the motor control unit 70 functions as the regenerative braking control unit M23, thereby executing the process of controlling the motor-generator 40 in step S59. The processing circuit 61 of the friction braking control unit 60 functions as the friction braking control unit M21, thereby executing the process of controlling the friction braking device 30 in step S59. Then, the regenerative coordination controller 100 temporarily ends the switching process.

[0056] <Post-Stop Processing> A post-stop processing, which is a flow of processing in the regeneration coordination control device 100 while the vehicle 10 is stopped, will be described with reference to Fig. 7. The post-stop processing is repeatedly executed for each predetermined control cycle.

[0057] In step S81, the regenerative coordination control device 100 determines whether the vehicle 10 is stopped. If the regenerative coordination control device 100 determines that the vehicle 10 is stopped (S81: YES), the process proceeds to step S83. On the other hand, if the regenerative coordination control device 100 determines that the vehicle 10 is not stopped (S81: NO), the regenerative coordination control device 100 temporarily ends the post-stop process.

[0058] In step S83, the regenerative coordination control device 100 determines whether the target braking force FxTr is equal to or less than the start-determination braking force FxA. When the driver intends to start the vehicle 10, he or she cancels the operation of the brake operating member 11. The target braking force FxTr is a value based on at least one of the operation amount and operation force of the brake operating member 11. Therefore, the start-determination braking force FxA is set to a value that serves as a criterion for determining whether the driver intends to start the vehicle 10. If the target braking force FxTr is equal to or less than the start-determination braking force FxA (S83: YES), the regenerative coordination control device 100 proceeds to step S85. On the other hand, if the target braking force FxTr is greater than the start-determination braking force FxA (S83: NO), the regenerative coordination control device 100 proceeds to step S87.

[0059] In step S85, the regenerative cooperative control device 100 sets the driving force Fd to the creep driving force Fc. The creep driving force Fc is a driving force equivalent to creep torque. The regenerative cooperative control device 100 then proceeds to step S97.

[0060] In step S87, the regeneration coordination control device 100 acquires slope information about the road surface on which the vehicle 10 is stopped. Specifically, the regeneration coordination control device 100 acquires the road surface gradient. For example, the regeneration coordination control device 100 can estimate the road surface gradient based on the longitudinal acceleration GX.

[0061] In the next step S89, the regenerative coordination control device 100 determines whether the road surface on which the vehicle 10 is stopped is a downhill road. If the regenerative coordination control device 100 determines that the road surface is a downhill road (S89: YES), the process proceeds to step S91. On the other hand, if the regenerative coordination control device 100 determines that the road surface is not a downhill road (S89: NO), the process proceeds to step S93.

[0062] In step S91, the regenerative coordination control device 100 sets the driving force Fd to a driving force in the reverse direction. The regenerative coordination control device 100 then proceeds to step S97. In step S93, the regenerative coordination control device 100 determines whether the road surface on which the vehicle 10 is stopped is an uphill road. If the regenerative coordination control device 100 determines that the road surface is an uphill road (S93: YES), the regenerative coordination control device 100 proceeds to step S95. On the other hand, if the regenerative coordination control device 100 determines that the road surface is not an uphill road (S89: NO), the road surface can be considered to be a level road, and the regenerative coordination control device 100 temporarily terminates the post-stop process. In this case, the regenerative coordination control device 100 does not cause the motor generator 40 to apply the driving force Fd to the wheels 12.

[0063] In step S95, the regenerative coordination controller 100 sets the driving force Fd to a driving force in the forward direction. Then, the regenerative coordination controller 100 proceeds to step S97. In step S97, the regenerative coordination controller 100 drives the motor generator 40 so that the set driving force Fd is applied to the wheels 12. Thereafter, the regenerative coordination controller 100 temporarily ends the post-stop process.

[0064] In this embodiment, the processing circuit 71 of the motor control unit 70 functions as the drive control unit M25 to execute the processes of steps S85 to S97. <Functions and Effects of This Embodiment> The functions and effects of this embodiment will be described with reference to FIG.

[0065] At timing t11 while the vehicle 10 is traveling, a braking request is generated, for example, when the driver starts to operate the brake operating member 11. Then, as shown in (B) of Figure 8, the target deceleration DVSTr gradually increases. Therefore, a braking force Fx is applied to the vehicle 10 through the execution of the braking process.

[0066] That is, when the target braking force FxTr correlated with the target deceleration DVSTr is equal to or less than the regenerative braking force upper limit value FxRmax, a value equal to the target braking force FxTr is derived as the regenerative braking force command value FxRTr, as shown in Fig. 8C. The motor generator 40 is operated based on this regenerative braking force command value FxRTr. Meanwhile, 0 (zero) is derived as the frictional braking force command value FxMTr.

[0067] After timing t12, the target deceleration DVSTr and the target braking force FxTr are maintained as shown in Fig. 8B. Therefore, after timing t12, the start vehicle speed VS1Th is maintained at a vehicle speed corresponding to the target braking force FxTr at timing t12.

[0068] When the regenerative braking force FxR is applied to the vehicle 10 in this manner, the vehicle speed VS gradually decreases as shown in Fig. 8A. Then, at timing t13, the vehicle speed VS reaches the start vehicle speed VS1Th, and the switching control is started from timing t13.

[0069] Preliminary switching control is started as switching control from timing t13. In the preliminary switching control, the rate of decrease of the regenerative braking force command value FxRTr and the rate of increase of the frictional braking force command value FxMTr are relatively small.

[0070] As described above, supplying brake fluid to the wheel cylinder 21 increases the frictional braking force FxM. Therefore, the response speed of the frictional braking force FxM is slower than that of the regenerative braking force FxR. In particular, at the initial stage of generating hydraulic pressure in the wheel cylinder 21, a deviation between the frictional braking force FxM and the frictional braking force command value FxMTr is likely to occur. When a deviation occurs between the frictional braking force FxM and the frictional braking force command value FxMTr, the deceleration DVS of the vehicle 10 deviates from the target deceleration DVSTr.

[0071] Therefore, when the preliminary switching control is being executed, the regenerative coordination control device 100 executes a correction process to correct the regenerative braking force command value FxRTr so as to reduce the magnitude of the difference ΔDVS between the target deceleration DVSTr and the deceleration DVS of the vehicle 10. Then, the friction braking device 30 is operated based on the friction braking force command value FxMTr derived by the preliminary switching control, and the motor generator 40 is operated based on the regenerative braking force command value FxRTr corrected by the correction process. As a result, the response delay of the friction braking force FxM is compensated for by the regenerative braking force FxR. This prevents the sum of the friction braking force FxM and the regenerative braking force FxR from deviating from the target braking force FxTr. Therefore, the regenerative coordination control device 100 can prevent fluctuations in the deceleration of the vehicle 10 caused by the execution of the switching control.

[0072] The vehicle speed VS decreases even while the preliminary switching control is being executed. Then, at timing t14, the vehicle speed VS reaches the switching vehicle speed VS2Th. In this case, it can be determined that the vehicle 10 is about to stop, and the switching control is switched from the preliminary switching control to the main switching control.

[0073] In this switching control, the rate at which the regenerative braking force command value FxRTr decreases and the rate at which the frictional braking force command value FxMTr increases are greater than when the preliminary switching control is executed. At timing t15 when the vehicle speed VS becomes 0 (zero), the regenerative braking force command value FxRTr also becomes 0 (zero). In other words, the switching from the regenerative braking force FxR to the frictional braking force FxM is completed.

[0074] Generally, as the vehicle speed VS approaches 0 (zero), the controllability of the regenerative braking force FxR decreases. If the correction process is executed even when the controllability of the regenerative braking force FxR decreases, the execution of the correction process may result in large fluctuations in the deceleration DVS of the vehicle 10.

[0075] In this embodiment, the correction process is terminated when the switching control is started. That is, in the regenerative cooperative control device 100, the correction process is initiated when the switching control is started, and the correction process is terminated immediately before the regenerative braking force FxR becomes 0 (zero). Therefore, the regenerative cooperative control device 100 can suppress fluctuations in the deceleration DVS immediately before the vehicle 10 is stopped.

[0076] As described above, at the start of the switching control, the frictional braking force command value FxMTr is set to a braking force equal to the predetermined braking force FxMp1. Therefore, a response delay of the frictional braking force FxM is unlikely to occur during the switching control.

[0077] The present embodiment can further provide the following effects. (1) If the frictional braking force command value FxMTr is significantly lower than the predetermined braking force FxMp1 at the start of the main switching control, the deceleration DVS may fluctuate due to a response delay of the frictional braking force FxM during the execution of the main switching control. On the other hand, if the frictional braking force command value FxMTr is significantly higher than the predetermined braking force FxMp1 at the start of the main switching control, the execution time of the preliminary switching control may become too long, which may reduce the efficiency of recovery of regenerative energy.

[0078] Therefore, in the regeneration coordination control device 100, the starting vehicle speed VS1Th is set to a smaller vehicle speed as the target deceleration DVSTr decreases. This allows the start timing of the preliminary switching control to be changed depending on the target deceleration DVSTr. As a result, the friction braking force command value FxMTr is prevented from falling significantly below the predetermined braking force FxMp1 at the start of the preliminary switching control. Furthermore, when the target deceleration DVSTr is low, the preliminary switching control is prevented from being started too early. Therefore, the regeneration coordination control device 100 can suppress fluctuations in the deceleration DVS during the execution of the preliminary switching control while suppressing a decrease in the efficiency of recovery of regenerative energy during vehicle braking.

[0079] (2) Consider a case where, after the vehicle 10 has stopped, the creep driving force Fc continues to be applied to the wheels 12 of the vehicle 10 as the driving force Fd. In this case, the driving force Fd continues to be applied to the wheels 12 even though the driver has no intention of starting the vehicle 10, so it is difficult to say that the energy efficiency of the vehicle 10 is high.

[0080] In this regard, when the regenerative cooperative control device 100 determines that the vehicle 10 is not stopped on a slope, the driving force Fd is not applied to the vehicle 10. This allows the regenerative cooperative control device 100 to suppress unnecessary consumption of electrical energy while the vehicle 10 is stopped.

[0081] However, when it is determined that the vehicle 10 is stopped on a downhill road, a driving force in the reverse direction is applied to the wheels 12 as a driving force Fd, as shown in Fig. 8 (D). When the vehicle 10 is stopped on a downhill road, the driving force in the reverse direction acts on the vehicle 10 as a force that prevents the vehicle 10 from rolling down due to its own weight. In other words, when the vehicle 10 is stopped on a downhill road, the regenerative cooperative control device 100 can prevent the vehicle 10 from rolling down due to its own weight by applying a driving force in the reverse direction to the wheels 12.

[0082] Furthermore, when it is determined that the vehicle 10 is stopped on an uphill road, a driving force in the forward direction is applied to the wheels 12 as the driving force Fd. When the vehicle 10 is stopped on an uphill road, the driving force in the forward / backward direction acts on the vehicle 10 as a force that prevents the vehicle 10 from rolling down due to its own weight. In other words, when the vehicle 10 is stopped on an uphill road, the regenerative cooperative control device 100 can prevent the vehicle 10 from rolling down due to its own weight by applying a driving force in the forward / backward direction to the wheels 12.

[0083] However, if the target braking force FxTr becomes equal to or less than the start-determination braking force FxA while the vehicle 10 is stopped, it is assumed that the driver intends to start the vehicle 10. Therefore, when the target braking force FxTr becomes equal to or less than the start-determination braking force FxA, the creep driving force Fc is applied to the wheels 12 as the driving force Fd. This allows the regenerative cooperative control device 100 to contribute to the prompt start of creep running of the vehicle 10 when the driver releases the braking operation.

[0084] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0085] If the regenerative cooperative control device applies a driving force in the backward direction to the wheels 12 when the vehicle 10 is stopped on a downhill road, it does not have to apply a driving force in the forward direction to the wheels 12 when the vehicle 10 is stopped on an uphill road. Conversely, if the regenerative cooperative control device applies a driving force in the forward direction to the wheels 12 when the vehicle 10 is stopped on an uphill road, it does not have to apply a driving force in the backward direction to the wheels 12 when the vehicle 10 is stopped on a downhill road.

[0086] The regenerative cooperative control device does not need to apply the driving force Fd to the wheels 12 when the vehicle 10 is stopped, even if the target braking force FxTr is equal to or less than the start-up determination braking force FxA. It is not necessary to vary the starting vehicle speed VS1Th according to the target deceleration DVSTr. For example, the starting vehicle speed VS1Th may be a vehicle speed higher than the switching vehicle speed VS2Th and a predetermined vehicle speed. Even in this case, when the vehicle speed VS becomes equal to or less than the switching vehicle speed VS2Th, the switching control switches from the preliminary switching control to the main switching control. Therefore, when the starting vehicle speed VS1Th is fixed at a predetermined vehicle speed, it is preferable to slow down the rate of reduction of the regenerative braking force FxR as the target deceleration DVSTr at the start of the preliminary switching control decreases.

[0087] The switching control does not necessarily include preliminary switching control as long as it includes the main switching control. In this case, the regenerative cooperative control device starts the main switching control when the vehicle speed VS falls below the start vehicle speed. The regenerative cooperative control device also corrects the regenerative braking force command value FxRTr derived by the main switching control through a correction process so that the difference ΔDVS between the target deceleration DVSTr and the deceleration DVS decreases. However, it is preferable that the regenerative cooperative control device terminates the correction process during the execution of the main switching control.

[0088] In the above embodiment, the correction process is terminated when the switching control is switched from the preliminary switching control to the main switching control. However, if the correction process is terminated immediately before the vehicle speed VS becomes 0 (zero), the correction process may be terminated while the main switching control is being executed. However, if the correction process is executed while the main switching control is being executed, it is preferable to make the gain of the feedback control smaller than that during the execution of the preliminary switching control.

[0089] The friction braking device may be an electric braking device that can apply a friction braking force to the wheels 12 according to the rotation angle of the electric motor. When such an electric braking device is employed as the friction braking device, the friction braking force FxM may have a higher response speed than the regenerative braking force FxR. If the friction braking force FxM has a higher response speed than the regenerative braking force FxR, the correction process may correct the friction braking force command value FxMTr so as to reduce the magnitude of the difference ΔDVS between the target deceleration DVSTr and the deceleration DVS. On the other hand, if the friction braking force FxM has a lower response speed than the regenerative braking force FxR, the correction process may correct the regenerative braking force command value FxRTr so as to reduce the magnitude of the difference ΔDVS.

[0090] The braking force to be corrected by the correction process is defined as the braking force to be corrected. In the above embodiment, the braking force with the higher response speed out of the regenerative braking force and the frictional braking force is defined as the braking force to be corrected, but this is not limited to this. For example, the braking force to be corrected may be determined based on the control accuracy and the amount of data used. For example, the braking force to be corrected out of the regenerative braking force and the frictional braking force with the higher control accuracy may be defined as the braking force to be corrected, or the braking force with the lower amount of data used may be defined as the braking force to be corrected.

[0091] The processing circuits 61 and 71 may be configured as circuits including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Examples of dedicated hardware include application-specific integrated circuits (ASICs). The processor includes a CPU and memory such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer.

[0092] It should be noted that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. A regenerative cooperative control device applied to a vehicle equipped with a regenerative braking device configured to apply a regenerative braking force, and a friction braking device configured to apply a friction braking force, comprising: a switching control unit configured to execute a switching control for switching the regenerative braking force to the friction braking force when the regenerative braking force is applied to the vehicle; and a correction unit configured to execute a correction process for correcting the braking force having a higher response speed, out of the regenerative braking force and the friction braking force, when the switching control is being executed, so as to reduce the magnitude of the difference between the deceleration of the vehicle and a target deceleration.

2. A regenerative cooperative control device as described in claim 1, wherein the friction braking device includes a hydraulic braking device configured to apply the friction braking force by increasing the hydraulic pressure in a wheel cylinder, and the correction unit corrects the regenerative braking force in the correction process so that the magnitude of the difference between the deceleration of the vehicle and the target deceleration is reduced.

3. The regenerative cooperative control device according to claim 1, wherein the correction unit is configured to start the correction process when the switching control is started, and to end the correction process immediately before the regenerative braking force becomes 0 (zero).

4. A regenerative cooperative control device as described in any one of claims 1 to 3, wherein the switching control unit is configured to start the switching control when the vehicle speed becomes equal to or lower than a starting vehicle speed, and the regenerative cooperative control device further includes a starting vehicle speed setting unit configured to set the starting vehicle speed to a smaller vehicle speed the lower the target deceleration.

5. The regenerative cooperative control device as described in claim 4, wherein the switching control includes a main switching control and a preliminary switching control that reduces the rate of reduction of the regenerative braking force compared to when the main switching control is being executed, and the switching control unit is configured to: start the preliminary switching control when the vehicle speed becomes equal to or lower than the starting vehicle speed, and to end the preliminary switching control and start the main switching control when the vehicle speed becomes equal to or lower than a switching vehicle speed that is lower than the starting vehicle speed.

6. The regenerative braking device is a brake / drive device configured to apply either a regenerative braking force or a drive force to the wheels of the vehicle, and the regenerative cooperative control device further includes a brake / drive control unit configured to control the brake / drive device so that, when the vehicle is stopped on a downhill road, the drive force for rotating the wheels in a reverse direction is applied to the wheels. The regenerative cooperative control device described in claim 1.

7. The regenerative cooperative control device according to claim 1, wherein the switching control unit reduces the regenerative braking force so that the regenerative braking force becomes 0 (zero) when the vehicle speed becomes 0 (zero) in the switching control.

8. A regenerative cooperative control method applied to a vehicle equipped with a regenerative braking device configured to apply a regenerative braking force and a friction braking device configured to apply a friction braking force, comprising: executing a switching control to switch the regenerative braking force to the friction braking force under a situation in which the regenerative braking force is applied to the vehicle; and executing a correction process to correct the braking force having a higher response speed out of the regenerative braking force and the friction braking force when the switching control is being executed so that the magnitude of the difference between the deceleration of the vehicle and a target deceleration is reduced.

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