Vehicle control device

Abstract

Vehicle control device (50) applicable to a vehicle, wherein the vehicle comprises: a drive torque generating device (10) that outputs a drive torque to wheels (FL, FR, RL, RR) of the vehicle; and a brake torque generating device that outputs a brake torque to the wheels (FL, FR, RL, RR) of the vehicle, wherein the vehicle control device (50) is configured to control a longitudinal acceleration of the vehicle based on a longitudinal acceleration setpoint (GxTr) of the vehicle, which is a setpoint of the longitudinal acceleration (Gx) of the vehicle, and wherein the vehicle control device (50) comprises: a determination unit (51) that determines whether prescribed conditions are met, including the condition that an amplitude of an oscillation of the longitudinal acceleration setpoint (GxTr) is less than or equal to a first determination amplitude, and the condition that an amplitude of an oscillation of the longitudinal acceleration (Gx) of the vehicle is greater than a second determination amplitude; and a cooperative control unit (523) which, based on the condition that the prescribed conditions have been determined to be met, performs a brake-drive cooperative procedure to maintain a torque output by one of the drive torque generating device (10) or the brake torque generating device (20) at a greater value than the torque at the time when the prescribed conditions were met and to adjust the torque output by the other device by control using the longitudinal acceleration setpoint (GxTr) and the longitudinal acceleration (Gx) of the vehicle.

Description

Technical area

[0001] The present invention relates to a vehicle control device that controls a longitudinal acceleration of the vehicle. background

[0002] DE 10 2012 221 837 A1 relates to a method and a device for vibration control of a drive train in a vehicle for reducing the vibrations in a drive train when driving over a projecting section of a road surface using engine torque control.

[0003] DE 10 2012 011 181 A1 relates to a method for operating a drive device, which is a vibration-capable system that is part of a motor vehicle having multiple wheels. A target torque is determined for at least some of the wheels, in particular for each wheel, and, in a normal operating mode, a drive torque provided by a drive unit is distributed to the wheels of the motor vehicle by means of a torque distribution device in accordance with the respective target torque.

[0004] US 2012 / 0 028 759 A1 discloses a power transmission control device for a vehicle comprising a multi-speed transmission, a clutch, and a control unit. The clutch is provided between the output shaft of the internal combustion engine and the input shaft of the multi-speed transmission to adjust a clutch torque (the maximum torque that the clutch can transmit). When the clutch is held in the half-engaged state, a damping effect is exerted on the torsional vibration due to clutch slippage.

[0005] A vehicle with an automatic longitudinal acceleration adjustment function, such as adaptive cruise control and automatic operation control, is provided with a target value calculation unit that calculates a longitudinal acceleration target value, which is a target value of the vehicle's longitudinal acceleration. JP 2008-120181 A describes an example of a method for calculating a longitudinal acceleration target value while a vehicle is traveling with adaptive cruise control. That is, according to JP 2008-120181 A, the target value calculation unit calculates the longitudinal acceleration target value such that an inter-vehicle distance from the preceding vehicle can be maintained at the specified inter-vehicle distance.

[0006] Furthermore, in the vehicle having the automatic longitudinal acceleration adjustment function, a driving torque output from a driving torque generating device and a braking torque output from a braking torque generating device are controlled based on a ratio of the thus calculated longitudinal acceleration target value and an actual longitudinal acceleration of the vehicle. Summary of the inventionTechnical problems

[0007] The drive torque generating device and the braking torque generating device may have a nonlinear control region, which is a control region in which fine adjustment of the torque is difficult. When the torque is controlled in the nonlinear control region, the torque becomes larger or smaller than necessary, and convergence of the actual longitudinal acceleration of the vehicle to the longitudinal acceleration target value becomes difficult. Therefore, when the torque is adjusted in the nonlinear control region, a rapid increase and decrease of the torque are alternately repeated, and the actual longitudinal acceleration of the vehicle may oscillate even though the longitudinal acceleration target value does not oscillate.

[0008] Furthermore, a case where the drive torque is increased and a case where the braking torque is increased may alternate depending on the longitudinal acceleration command value and the actual longitudinal acceleration of the vehicle. Even in such a case, the actual longitudinal acceleration of the vehicle may fluctuate even though the longitudinal acceleration command value does not fluctuate.

[0009] If the actual longitudinal acceleration of the vehicle oscillates, the vehicle occupant may feel uncomfortable when driving the vehicle. Solutions to the problems

[0010] A vehicle control device for solving the above-described problem is a device applicable to a vehicle, the vehicle having a drive torque generating device that outputs drive torque to wheels of the vehicle and a braking torque generating device that outputs braking torque to the wheels of the vehicle, and the vehicle control device is configured to control a longitudinal acceleration of the vehicle based on a longitudinal acceleration target value of the vehicle, which is a target value of the longitudinal acceleration of the vehicle. The vehicle control device includes a determination unit that determines whether prescribed conditions are met, including the conditions that an amplitude of an oscillation of the longitudinal acceleration target value is less than or equal to a first determination amplitude.and that an amplitude of a vibration of the longitudinal acceleration of the vehicle is greater than a second determination amplitude, and a cooperative control unit that, based on the condition that it has been determined that the prescribed conditions are met, performs a braking / driving cooperative process to maintain a torque output by one of the driving torque generating device or the braking torque generating device at a greater value than the torque at the time at which the prescribed conditions were met, and adjusts the torque output by the other device by feedback control using the longitudinal acceleration target value and the longitudinal acceleration of the vehicle.

[0011] If the oscillation amplitude of the longitudinal acceleration target value is less than or equal to the first determination amplitude, it cannot be determined that the longitudinal acceleration target value is oscillating. Furthermore, if the oscillation amplitude of the vehicle's longitudinal acceleration is greater than the second determination amplitude, it can be determined that the vehicle's longitudinal acceleration is oscillating.

[0012] In the configuration described above, when the prescribed conditions are met, the torque output from one of the drive torque generating devices or the brake torque generating devices is maintained at a larger value than the torque at the time when the prescribed conditions were met, and the torque output from the other device is adjusted through feedback control by executing the brake / drive cooperative process. Therefore, both the torque output from one device and the torque output from the other device can be made larger than the torques at the time when the prescribed conditions were met. That is,, both the torque output from one device and the torque output from the other device can be adjusted in a control range outside a non-linear control range, and as a result, fine adjustment of the torque output from the other device becomes easier than before the prescribed conditions were met.

[0013] Furthermore, according to the implementation of such a braking / driving cooperative method, the alternating repetition of a driving torque adjustment period and a braking torque adjustment period can be suppressed. Therefore, the generation of vibrations in the longitudinal acceleration of the vehicle when the longitudinal acceleration target value is not oscillating can be suppressed, and furthermore, the deterioration of ride comfort for the vehicle occupants can be suppressed. Short description of the characters Fig. 1 is a diagram showing a functional configuration of a control device of a vehicle according to an embodiment and a schematic configuration of a vehicle equipped with the control device. Fig. 2 is a flowchart describing a processing routine executed by a determination unit of the control device. Fig. 3 is a diagram showing a state in which noise components are removed to extract the vibration of the longitudinal acceleration of the vehicle. Fig. 4 is a flowchart describing a processing routine executed by a brake / drive control unit of the control device. Fig. 5(a) to 5(d) are timing charts showing a case where a switching process is performed under the condition that a prescribed condition is satisfied. Fig. 6(a) to 6(d) are timing charts showing a case where a braking / driving cooperative process is performed under the condition that a prescribed condition is satisfied. Description of an embodiment

[0014] The following is based on reference to Fig. 1 to 6 an embodiment of a vehicle control device is described. Fig. 1 shows, in accordance with the present embodiment, a vehicle equipped with a control device 50. As in Fig. As shown in Figure 1, the vehicle is a front-wheel drive vehicle having a plurality of (four in the present embodiment) wheels (left front wheel FL, right front wheel FR, left rear wheel RL, right rear wheel RR). The vehicle includes a drive torque generating device 10 that outputs drive torque to the front wheels FL and FR, which are drive wheels, and a braking torque generating device 20 that outputs braking torque to each of the wheels FL, FR, RL, and RR.

[0015] The drive torque generating device 10 includes an engine 11, which is an example of a drive source of the vehicle, a transmission 12 configured to automatically change the gear speed, and a differential gear 13. The drive torque output from the engine 11 is transmitted to each of the front wheels FL and FR through the transmission 12 and the differential gear 13. In the present embodiment, a stepped transmission with six forward speeds is used as the transmission 12. In this case, when the first gear speed is the lowest gear speed and the gear speed of the transmission 12 is equal to the first gear speed, the transmission 12 cannot be further downshifted. That is, the first gear speed is the lowest gear speed.

[0016] The braking torque generating device 20 includes a hydraulic pressure generating device 21, to which a braking operating element 22, such as a brake pedal, is connected, and a brake actuator 26. Wheel cylinders 31 of brake mechanisms 30a, 30b, 30c, and 30d provided on the wheels FL, FR, RL, and RR are connected to a hydraulic circuit of the brake actuator 26. The brake mechanisms 30a to 30d are configured to apply a larger braking torque to the wheels FL, FR, RL, and RR as the wheel cylinder pressure (WC pressure), which is the hydraulic pressure in the wheel cylinder 31, increases.

[0017] When the vehicle driver operates the brake operating element 22, the hydraulic pressure generating device 21 inputs an operating force input to the brake operating element 22 to a master cylinder 24 with the aid of a booster 23, and a master cylinder pressure (MC pressure), which is a hydraulic pressure corresponding to the input operating force, is generated in the master cylinder 24. Then, the brake fluid from the hydraulic pressure generating device 21 is supplied to the wheel cylinder 31 through the hydraulic circuit of the brake actuator 26. As a result, the WC pressure in the wheel cylinder 31 becomes higher as the operating force input to the brake operating element 22 increases.

[0018] The brake actuator 26 is configured to adjust the braking torque for each wheel FL, FR, RL and RR even when the driver does not perform any braking operation, ie, to adjust the WC pressure in each wheel cylinder 31.

[0019] Next, the vehicle control device 50 will be described with reference to Fig. 1. As described in Fig. As shown in Figure 1, two longitudinal acceleration sensors SE1 and SE2, which output detection signals corresponding to the longitudinal acceleration acting on the vehicle, are electrically connected to the control device 50. The detection signal output by the first longitudinal acceleration sensor SE1 of the two longitudinal acceleration sensors SE1 and SE2 is used when performing vehicle control for automatically adjusting the longitudinal acceleration of the vehicle, such as in adaptive cruise control and automatic operation control. The detection signal output by the second longitudinal acceleration sensor SE2 is used when estimating the gradient of the road surface on which the vehicle is traveling.

[0020] Furthermore, the control device 50 is configured with a target acceleration setting unit 100 that sets a longitudinal acceleration target value GxTr, which is a target value of the longitudinal acceleration, when performing vehicle control for automatically adjusting the longitudinal acceleration of the vehicle. Therefore, the control device 50 controls the longitudinal acceleration Gx of the vehicle based on the longitudinal acceleration target value GxTr input from the target acceleration setting unit 100.

[0021] The control device 50 includes a determination unit 51 and a braking / driving control unit 52 as functional units for controlling the driving torque generating device 10 and the braking torque generating device 20 based on the longitudinal acceleration target value GxTr.

[0022] The determination unit 51 determines whether a prescribed condition, which is a condition for determining whether a shift process and a braking / driving cooperative process described below are executed, is met. The braking / driving control unit 52 controls at least one of the drive torque generating device 10 and the braking torque transmitting device 20 to cause the longitudinal acceleration Gx to converge with the longitudinal acceleration target value GxTr. That is, the braking / driving control unit 52 includes a gearshift control unit 521, a normal control unit 522, and a cooperative control unit 523.

[0023] The gearshift control unit 521 executes a shift process for downshifting the transmission 12 under the condition that the prescribed condition is satisfied in a situation where the braking torque is not applied to the FL, FR, RL, and RR wheels. Furthermore, even if the prescribed condition is satisfied, the gearshift control unit 521 does not execute the shift process if the transmission 12 cannot be further downshifted because the gear stage of the transmission 12 is equal to the first gear stage.

[0024] The normal control unit 522 performs a normal acceleration control process for controlling at least one of the drive torque and the brake torque under the condition that the prescribed condition is not satisfied. That is, in the acceleration control process for controlling the drive torque, the normal control unit 522 calculates a drive torque demand value DTR, which is a drive torque demand value, based on the longitudinal acceleration target value GxTr and the longitudinal acceleration Gx, and controls the drive torque generating device 10 so that the sum of the torques transmitted to the front wheels FL and FR converges to the drive torque demand value DTR.Furthermore, in the acceleration control process for controlling the braking torque, the normal control unit 522 calculates a braking torque demand value BTR, which is a demand value of the braking torque, based on the longitudinal acceleration command value GxTr and the longitudinal acceleration Gx, and controls the operation of the brake actuator 26 so that the sum of the braking torques transmitted to each of the wheels FL, FR, RL, and RR converges to the braking torque demand value BTR.

[0025] When the braking torque is applied to the wheels FL, FR, RL, and RR, the cooperative control unit 523 executes the braking / driving cooperative process to control the driving torque and the braking torque under the condition that the prescribed condition is satisfied. Furthermore, when the transmission 12 cannot be further downshifted because the gear stage of the transmission 12 is equal to the first gear stage, the cooperative control unit 523 executes the braking / driving cooperative process under the condition that it is determined that the prescribed condition is satisfied. Then, in the braking / driving cooperative process, the cooperative control unit 523 calculates the driving torque demand value DTR and controls the driving torque generating device 10 based on the driving torque demand value DTR.Furthermore, in the braking / driving cooperative process, the cooperative control unit 523 calculates the braking torque demand value BTR and controls the operation of the brake actuator 26 so that the sum of the braking torques transmitted to the wheels FL, FR, RL and RR converges to the braking torque demand value BTR.

[0026] Next, with reference to Fig. 2 and Fig. 3 describes a process routine executed by the determination unit 51 for determining whether the prescribed condition is met. This process routine is executed for each predetermined control cycle.

[0027] As in Fig. 2, in the present processing routine, the determination unit 51 acquires a period Y1 and an amplitude Z1 of the oscillation of the longitudinal acceleration target value GxTr of the vehicle (step S1). Subsequently, the determination unit 51 determines whether the longitudinal acceleration target value GxTr is oscillating (step S12). Specifically, the determination unit 51 may determine that the longitudinal acceleration target value GxTr is oscillating if the acquired period Y1 of the oscillation of the longitudinal acceleration target value GxTr is shorter than a first determination period Y1Th and the amplitude Z1 of the oscillation of the longitudinal acceleration target value GxTr is greater than a first determination amplitude Z1Th. If it is determined that the longitudinal acceleration target value is oscillating (step S12: YES), the determination unit 51 proceeds to step S17 described below.

[0028] On the other hand, if it is not determined that the longitudinal acceleration target value GxTr is oscillating (step S12: NO), the determination unit 51 acquires a time period Y3 and an amplitude Z3 of the oscillation of a gradient equivalent acceleration Gθ (step S13). The gradient equivalent acceleration Gθ is an example of the gradient equivalent value, which is a value correlated with the gradient of the road surface on which the vehicle is traveling, and can be calculated based on the detection signal of the second longitudinal acceleration sensor SE2. More specifically, the gradient equivalent acceleration Gθ is a value obtained by performing a known smoothing method on the detection signal of the second longitudinal acceleration sensor SE2. Therefore, even if the longitudinal acceleration Gx of the vehicle oscillates in a situation where the road surface gradient is constant, the gradient equivalent acceleration Gθ hardly oscillates.Subsequently, the determination unit 51 determines whether the gradient equivalent acceleration Gθ is oscillating (step S14). Specifically, the determination unit 51 determines that the gradient equivalent acceleration Gθ is oscillating, that is, the road surface gradient is oscillating, when the acquired period Y3 of oscillation of the gradient equivalent acceleration Gθ is shorter than a third determination period Y3Th and the amplitude Z3 of oscillation of the gradient equivalent acceleration Gθ is greater than a third determination amplitude Z3Th. Then, if it is determined that the gradient equivalent acceleration Gθ is oscillating (step S14: YES), the determination unit 51 proceeds to step S17 described below.

[0029] On the other hand, if it is not determined that the gradient equivalent acceleration Gθ is oscillating (step S14: NO), the determination unit 51 acquires a time period Y2 and an amplitude Z2 of the oscillation of the longitudinal acceleration Gx of the vehicle (step S15). The longitudinal acceleration Gx is a value corresponding to the actual longitudinal acceleration of the vehicle and can be calculated based on the detection signal of the first longitudinal acceleration sensor SE1.

[0030] Here, with reference to Fig. 3 describes an example of a method for acquiring the period Y2 and the amplitude Z2 of the oscillation of the longitudinal acceleration Gx. A raw value GxRV of the longitudinal acceleration based on a detection signal of the first longitudinal acceleration sensor SE1 includes a noise component, as shown in Fig. 3 is shown by a dashed line. Thus, the noise component is removed from the raw value GxRV of the longitudinal acceleration by a filtering process using a bandpass filter or a lowpass filter, and the Fig. 3, the longitudinal acceleration Gx indicated by a solid line is acquired. Then, from the waveform showing the transition of the thus acquired longitudinal acceleration Gx, the period PGx of the oscillation of the longitudinal acceleration Gx is derived as the period Y2, and the amplitude AGx of the oscillation is derived as the amplitude Z2, using the zero-crossing method.

[0031] Also, the period Y1 and the amplitude Z1 of the oscillation of the longitudinal acceleration setpoint GxTr can be determined by the same method as that described with reference to Fig. 3. The period Y3 and the amplitude Z3 of the oscillation of the gradient equivalent acceleration Gθ can also be obtained by the same method as that described with reference to Fig. 3 described procedures can be acquired.

[0032] Returning to Fig. 2, the determination unit 51 determines whether the longitudinal acceleration Gx is oscillating (step S16). Specifically, the determination unit 51 can determine that the longitudinal acceleration Gx is oscillating if the acquired oscillation period Y2 of the longitudinal acceleration Gx is shorter than a second determination period Y2Th and the amplitude Z2 of the oscillation of the longitudinal acceleration Gx is greater than a second determination amplitude Z2Th. If it is not determined that the longitudinal acceleration Gx is oscillating (step S16: NO), the determination unit 51 proceeds to the next process step S17.

[0033] At step S17, the determination unit 51 sets a condition satisfaction flag FLG1 to OFF. The condition satisfaction flag FLG1 is a flag that is set to OFF when the prescribed condition is not satisfied and is set to ON when the prescribed condition is satisfied. Then, the determination unit 51 terminates the present processing routine once.

[0034] On the other hand, if it is determined at step S16 that the longitudinal acceleration Gx is oscillating (step S16: YES), the determination unit 51 sets the condition satisfaction flag FLG1 to ON (step S18). That is, in the present embodiment, the prescribed condition includes all of the conditions that the longitudinal acceleration target value GxTr is not determined to be oscillating, the gradient equivalent acceleration Gθ is not determined to be oscillating (that is, the road surface gradient is not determined to be periodically changing), and the longitudinal acceleration Gx is not determined to be oscillating. Thereafter, the determination unit 51 temporarily terminates the present processing routine.

[0035] Next, with reference to Fig. 4 describes a process routine executed by the brake / drive control unit 52 for performing vehicle control based on the longitudinal acceleration target value GxTr. This process routine is a routine that is repeatedly executed and is executed at a time when a prescribed time has elapsed from the end of the previous execution of the present process routine. The prescribed time is a time corresponding to the control cycle.

[0036] As in Fig. 4, in the present process routine, the brake / drive control unit 52 determines whether the condition satisfaction flag FLG1 is set to ON (step S31). If the condition satisfaction flag FLG1 is set to OFF (step S31: NO), the prescribed condition is not satisfied, and thus the normal control unit 522 of the brake / drive control unit 52 executes the normal acceleration control process (step S32). That is, when the longitudinal acceleration Gx of the vehicle is less than or equal to the longitudinal acceleration target value GxTr, the normal control unit 522 controls the drive torque generating device 10, i.e., the drive torque through the acceleration control process. On the other hand, when the longitudinal acceleration Gx of the vehicle is greater than the longitudinal acceleration target value GxTr, the normal control unit 522 controls the drive torque generating device 10, i.e.,the drive torque through the acceleration control process to apply engine braking to the vehicle, or controls the braking torque generating device 20, that is, the braking torque. Then, the braking / driving control unit 52 temporarily terminates the present processing routine.

[0037] On the other hand, if the condition satisfaction flag FLG1 is set to ON at step S31 (step S31: YES), the prescribed condition is satisfied, and thus the brake / drive control unit 52 determines whether the braking torque is applied to the wheels FL, FR, RL, and RR (step S33). When the braking torque is not applied to the wheels FL, FR, RL, and RR, the longitudinal acceleration Gx of the vehicle may possibly oscillate because the drive torque is adjusted in the non-linear control region of the drive torque. The non-linear control region is a control region in which fine adjustment of the drive torque is difficult. On the other hand, when the braking torque is applied to the wheels FL, FR, RL, and RR, the longitudinal acceleration Gx of the vehicle may possibly oscillate because the braking torque is adjusted in the non-linear control region of the braking torque.

[0038] Therefore, if the braking torque is applied to the wheels FL, SR, RL, and RR (step S33: YES), the braking / driving control unit 52 proceeds to step S38 described below. On the other hand, if the braking torque is not applied to the wheels FL, FR, RL, and RR (step S33: NO), the braking / driving control unit 52 determines whether the transmission 12 can be downshifted (step S34). If the transmission 12 cannot be downshifted because the gear stage of the transmission 12 is equal to the first gear stage (step S34: NO), the braking / driving control unit 52 proceeds to step S38 described below.

[0039] On the other hand, if the transmission 12 can be downshifted because the shift stage of the transmission 12 is not equal to the first shift stage (step S34: YES), the gearshift control unit 521 of the brake / drive control unit 52 downshifts the transmission 12, that is, decreases the shift stage of the transmission 12 by one through the shift process (step S35). Subsequently, the normal control unit 522 of the brake / drive control unit 52 executes the normal acceleration control process in the same manner as in step S32 (step S36). Then, the brake / drive control unit 52 determines whether the elapsed time from the time the shift process is performed has reached a predetermined time TM (step S37). A slight time lag occurs from the time the shift process is performed to the time the transmission downshift is actually completed.Therefore, the predetermined time TM is set to a length corresponding to such a time delay.

[0040] If the elapsed time is shorter than the predetermined time TM (step S37: NO), the brake / drive control unit 52 proceeds to the above-described process step S36. On the other hand, if the elapsed time has reached the predetermined time TM (step S37: YES), the brake / drive control unit 52 temporarily terminates the present process routine.

[0041] At step S38, the cooperative control unit 523 of the braking / driving control unit 52 executes the braking / driving cooperative process. That is, in the present embodiment, the braking / driving cooperative process is performed when the prescribed condition is satisfied in a situation where the braking torque is applied to the wheels FL, FR, RL, and RR. Moreover, even when no braking torque is applied to the wheels FL, FR, RL, and RR and when the shift stage of the transmission 12 becomes the lowest stage by the shift control, the braking / driving cooperative process is performed under the condition that a state where the prescribed condition is satisfied continues, even when the shift process is performed.

[0042] In a vehicle equipped with the control device 50 according to the present embodiment, the braking torque response resulting from the operation of the brake actuator 26 is higher than the driving torque response resulting from the driving of the engine 11. Therefore, in the braking / driving cooperative process, the cooperative control unit 523 maintains the driving torque output from the engine 11, that is, the driving torque demand value DTR, at a larger value than the driving torque at the time point at which the prescribed condition is satisfied. Specifically, assuming that the driving torque at the time point at which the prescribed condition is satisfied is equal to a reference driving torque DTB, in the braking / driving cooperative process, the driving torque demand value DTR is made equal to the sum of the reference driving torque DTB and an offset value X.The offset value X is a value corresponding to the difference between the upper limit and the lower limit of the non-linear control range of the drive torque.

[0043] Furthermore, in the braking / driving cooperative process, the cooperative control unit 523 derives the operation amount of the brake actuator 26, that is, the braking torque demand value BTR, by feedback control using the longitudinal acceleration command value GxTr and the longitudinal acceleration Gx of the vehicle.

[0044] Then, in the braking / driving cooperative process, the cooperative control unit 523 controls the engine 11 based on the thus-calculated driving torque demand value DTR and controls the operation of the brake actuator 26 based on the thus-calculated braking torque demand value BTR.

[0045] Subsequently, the braking / driving control unit 52 determines whether the oscillation of the longitudinal acceleration Gx of the vehicle is stable (step S39). Specifically, it can be determined that the oscillation of the longitudinal acceleration Gx is stable when the amplitude Z2 of the oscillation of the longitudinal acceleration Gx becomes smaller than the second determination amplitude Z2Th. If it is still not determined that the oscillation of the longitudinal acceleration Gx is stable (step S39: NO), the braking / driving control unit 52 proceeds to the above-described process step S38. That is, the execution of the braking / driving cooperative process continues.

[0046] On the other hand, if it is determined that the oscillation of the longitudinal acceleration Gx is stable (step S39: YES), the brake / drive control unit 52 determines whether the execution of the brake control for applying the braking torque to the wheels FL, FR, RL, and RR is unnecessary (step S40). It can be determined that the execution of the brake control is unnecessary when the longitudinal acceleration Gx is less than or equal to the longitudinal acceleration target value GxTr, and it can be determined that the execution of the brake control is necessary when the longitudinal acceleration Gx is greater than the longitudinal acceleration target value GxTr. Therefore, if it is determined that the execution of the brake control is unnecessary (step S40: YES), the cooperative control unit 523 of the brake / drive control unit executes the degeneration process of the brake control and executes the acceleration control process through the engine controller (step S41). That is,In the degeneration process of the brake control, the cooperative control unit 523 gradually reduces the braking torque demand value BTR to "0." Furthermore, in the acceleration control process, the cooperative control unit 523 calculates the driving torque demand value DTR through the engine controller so that the longitudinal acceleration Gx converges to the longitudinal acceleration target value GxTr, and controls the engine 11 based on the driving torque demand value DTR. Then, the cooperative control unit 523 terminates process S41 when the braking torque becomes "0" through the degeneration process. Thereafter, the brake / drive control unit 52 temporarily terminates the present process routine.

[0047] On the other hand, if it is determined at step S40 that execution of the brake control is necessary (step S40: NO), the cooperative control unit 523 of the brake / drive control unit 52 executes the degeneration process of the engine control and executes the acceleration control process by the brake control (step S42). That is, in the degeneration process of the engine control, the cooperative control unit 523 gradually reduces the drive torque demand value DTR to the drive torque at the time when the engine 11 is idling. Further, in the acceleration control process by the brake control, the cooperative control unit 523 calculates the brake torque demand value BTR so that the longitudinal acceleration Gx converges to the longitudinal acceleration target value GxTr, and controls the brake actuator 26 based on the brake torque demand value BTR.Then, when the drive torque becomes equal to the drive torque at the idling time point through the degeneration process, the cooperative control unit 523 terminates process step S42. Thereafter, the brake / drive control unit 52 temporarily terminates the present process routine.

[0048] Next, with reference to Fig. 5, the operation in a case where the vibration of the longitudinal acceleration Gx of the vehicle converges due to the execution of the switching process in a situation where the prescribed condition is met is described together with the effect. A two-dot chain line in Fig. 5(a) shows the acceleration corresponding to the lower limit of the drive torque output by the internal combustion engine 11. A solid line in Fig. 5(b) shows the transition of the drive torque demand value DTR, and a hatched area is the non-linear control range of the drive torque. Furthermore, a solid line in Fig. 5(c) shows the transition of the braking torque demand value BTR and a hatched area is the nonlinear control range of the braking torque.

[0049] As in Fig. 5(a), Fig. 5(b), Fig. 5(c) and Fig. As shown in Figure 5(d), the controllability of the drive torque is low because the drive torque is adjusted in the nonlinear control region. As a result, the rapid increase and decrease of the drive torque are alternately repeated, so that the longitudinal acceleration Gx of the vehicle cannot converge to the longitudinal acceleration target value GxTr, and the longitudinal acceleration Gx oscillates. Since at this time, it is neither determined that the longitudinal acceleration target value GxTr oscillates nor that the gradient equivalent acceleration oscillates, it is determined at the first time point t11 ​​that the prescribed condition is satisfied. When the drive torque demand value DTR is a negative value, the drive torque transmitted to the wheels FL, FR, RL, and RR becomes negative, so the engine brake is applied to the vehicle.

[0050] In the Fig. In the example shown in Figure 5, the shifting process is performed at the first time t11 when the braking torque is not applied to the wheels FL, FR, RL, and RR, and the shift stage of the transmission 12 is the third shift stage. As a result, the shift stage of the transmission 12 is changed from the third shift stage to the second shift stage. Thus, as indicated by a two-dot chain line in Fig. 5(a), the acceleration corresponding to the lower limit value of the drive torque output from the engine 11 becomes smaller, and thus the lower limit value DTLm of the drive torque that can be transmitted to the front wheels FL and FR, which are drive wheels, via the transmission 12, as shown by a one-dot chain line in Fig. 5(b). The nonlinear control range of the drive torque can be reduced to the lower side in the figure. Therefore, the drive torque demand value DTR becomes larger than the upper limit of the nonlinear control range. That is, the drive torque can be controlled in a control range outside the nonlinear control range. As a result, the fine adjustment of the drive torque becomes easy compared to that before the switching process is executed, and the longitudinal acceleration Gx can converge to the longitudinal acceleration target value GxTr, and further, the oscillation of the longitudinal acceleration Gx can be suppressed. Therefore, the vehicle occupant is less likely to feel uncomfortable when driving the vehicle.

[0051] Moreover, in the present embodiment, a state in which the longitudinal acceleration Gx oscillates can be solved without performing the brake-drive cooperative process due to the performance of the switching process, that is, the oscillation of the longitudinal acceleration Gx can be suppressed while suppressing an increase in the energy loss of the vehicle.

[0052] The oscillation of the longitudinal acceleration Gx cannot be suppressed only by performing the shift process once. In this case, the shift process is performed again to decrease the gear stage of the transmission 12 by one more time. As described above, if the oscillation of the longitudinal acceleration Gx can be suppressed while repeatedly performing the shift process until the gear stage of the transmission 12 becomes equal to the first gear stage, the braking / driving cooperative process cannot be performed.

[0053] When the braking torque is applied to the wheels FL, FR, RL, and RR, even if the prescribed condition is met in a situation where the shift stage of the transmission 12 is not equal to the first shift stage, the braking / driving cooperative process is performed without executing the shift process. This is because oscillation of the longitudinal acceleration Gx is possible due to the braking torque to be applied to the wheels FL, FR, RL, and RR. In such a case, the oscillation of the longitudinal acceleration Gx cannot be suppressed even if the transmission 12 is downshifted due to the execution of the shift process.

[0054] Therefore, in a case where the prescribed condition is satisfied in a situation where the braking torque is applied to the wheels FL, FR, RL, and RR, the braking / driving cooperative process is performed even though the transmission 12 can be downshifted. Then, according to the execution of the braking / driving cooperative process, the drive torque demand value DTR of the engine 11 and the brake actuator 26, which is a command value for the engine 11, which is a low-response device, is maintained at a larger value than the drive torque at the time when the prescribed condition is satisfied. As a result, the drive torque is adjusted in the control region outside the nonlinear control region.

[0055] Furthermore, in the braking / driving cooperative process, the braking torque demand value BTR, which is a command value for the brake actuator 26, is calculated by the above-described control. In the present embodiment, the driving torque is larger than that at the time when the prescribed condition is satisfied, and thus the braking torque is larger than that at the time when the prescribed condition is satisfied. As a result, even if the braking torque is adjusted at the time when the prescribed condition is satisfied in the non-linear control region, the braking torque can be adjusted by performing the braking / driving cooperative process in the control region outside the non-linear control region. Therefore, the braking torque can be accurately controlled.

[0056] The occurrence of sudden changes in drive torque and braking torque can be suppressed by implementing the braking-driving cooperative process in this way. As a result, the oscillation of the vehicle's longitudinal acceleration Gx is suppressed. Therefore, the occurrence of oscillation of the vehicle's longitudinal acceleration Gx when the longitudinal acceleration target value GxTr and the gradient equivalent acceleration Gθ are not oscillating can be suppressed, and further, deterioration of ride comfort for the vehicle occupant can be suppressed.

[0057] Next, the operation when the prescribed condition is satisfied in a situation where the gear stage of the transmission 12 is set to the first gear stage will be described together with the effects with respect to Fig. 6. A two-dot dashed line in Fig. 6(a) shows the acceleration corresponding to the lower limit of the drive torque output by the internal combustion engine 11. A solid line in Fig. 6(b) shows the transition of the drive torque demand value DTR, and a hatched area is the non-linear control range of the drive torque. Furthermore, a solid line in Fig. 6(c) shows the transition of the braking torque demand value BTR and a hatched area is the nonlinear control range of the braking torque.

[0058] As in Fig. 6(a), Fig. 6(b), Fig. 6(c) and Fig. As can be seen from Figure 6(d), since a case where the drive torque is adjusted and a case where the braking torque is adjusted are alternately repeated, it can be determined that the longitudinal acceleration Gx of the vehicle is oscillating even though the longitudinal acceleration target value GxTr is not determined to be oscillating and the gradient equivalent acceleration Gθ is not determined to be oscillating. Then, it is determined that the prescribed condition is satisfied at the first time point t12.

[0059] In the Fig. In the example shown in Fig. 6, it is not possible to further downshift the transmission 12 by executing the shift process because the shift stage of the transmission 12 is equal to the first shift stage. Therefore, at the first time point t21, execution of the braking / driving cooperative process is started. Then, according to the execution of the braking / driving cooperative process, the drive torque demand value DTR of the engine 11 and the brake actuator 26, which is a command value for the engine 11, which is a low-response device, is maintained at a larger value than the drive torque at the time point when the prescribed condition is satisfied. As a result, the drive torque is adjusted in the control region outside the nonlinear control region.

[0060] Furthermore, in the braking / driving cooperative process, the braking torque demand value BTR, which is a command value for the brake actuator 26, is calculated by the above-described control. In the present embodiment, the driving torque is larger than that at the time when the prescribed condition is satisfied, and thus the braking torque is larger than that at the time when the prescribed condition is satisfied. As a result, even if the braking torque is adjusted at the time when the prescribed condition is satisfied in the non-linear control region, the braking torque can be adjusted by performing the braking / driving cooperative process in the control region outside the non-linear control region. Therefore, the braking torque can be accurately controlled.

[0061] According to such an embodiment of the braking / driving cooperative method, a case where the driving torque is adjusted and a case where the braking torque is adjusted are not repeated alternately, and the occurrence of sudden changes in the driving torque and the braking torque can be suppressed. As a result, the oscillation of the longitudinal acceleration Gx of the vehicle is suppressed. Therefore, the occurrence of the oscillation of the longitudinal acceleration Gx of the vehicle can be suppressed when the longitudinal acceleration target value GxTr and the gradient equivalent acceleration Gθ do not oscillate, and further, deterioration of ride comfort for the vehicle occupant can be suppressed.

[0062] When the oscillation of the longitudinal acceleration Gx is suppressed at the second time point t22 and it is determined that the longitudinal acceleration Gx converges to the longitudinal acceleration target value GxTr, the execution of the brake-drive cooperative process is terminated. Fig. In the example shown in Figure 6, the degeneration process of the brake control is performed, and the braking torque is gradually reduced. Then, the drive torque demand value DTR is also gradually reduced. Therefore, a state in which the longitudinal acceleration Gx converges to the longitudinal acceleration target value GxTr is maintained even after the execution of the braking / driving cooperative process is terminated.

[0063] The embodiment described above may be modified into another embodiment described below. In the above-described embodiment, when a state in which the longitudinal acceleration Gx oscillates cannot be resolved even if the shifting process is performed once, since the prescribed condition is satisfied in a situation where the braking torque is not applied to the wheels FL, FR, RL, and RR, the shifting process is performed again when the transmission 12 can be further downshifted. However, the present invention is not limited to this, and when the state in which the longitudinal acceleration Gx oscillates cannot be resolved even if the shifting process is performed once, the braking / driving cooperative process may be performed even if the transmission 12 can be further downshifted.According to this configuration, in the situation where the prescribed condition is satisfied, the state where the prescribed condition is satisfied can be suppressed from continuing for a long time compared with a case where the braking / driving cooperative process is not performed until the shift stage of the transmission 12 becomes the lowest stage. - In the switching process, the gear stage of the transmission 12 can be reduced by two or more stages. The vehicle incorporating the control device 50 may be configured with a continuously variable transmission that can change the gear ratio in steps, like the transmission. Downshifting in such a continuously variable transmission means an increase in the gear ratio. Even in this case, if the prescribed condition is met in the situation where the braking torque is not applied to the FL, FR, RL, and RR wheels, the oscillation of the longitudinal acceleration Gx can be suppressed by reducing the pseudo-shift stage of the continuously variable transmission through the shifting process. - As a drive torque generating device, a device including the drive motor as a drive source can be mentioned. Hybrid vehicles and electric vehicles are known as vehicles having such a drive torque generating device. In particular, in some electric vehicles, the transmission may not be arranged between the drive motor and the drive wheels. In such a vehicle, when it is determined that the prescribed condition is met, the braking / driving cooperative process is performed regardless of whether the braking torque is applied to the FL, FR, RL, and RR wheels. - The braking torque generating device may not use brake fluid, as long as it can apply braking torque to the wheels FL, FR, RL, and RR by operating the brake mechanisms provided for the wheels FL, FR, RL, and RR. For example, the braking torque generating device may be an electric braking device in which a brake motor is provided for each of the wheels FL, FR, RL, and RR. Since, in the above-described embodiment, the response of the braking torque generating device 20 is higher than the response of the engine 11, the braking torque demand value BTR is calculated by feedback control after setting the driving torque demand value DTR at a constant value in the braking / driving cooperative process. However, in a vehicle in which the response of the braking torque generating device 20 is lower than the response of the engine 11, the driving torque demand value DTR may be calculated by feedback control after setting the braking torque demand value BTR in the braking / driving cooperative process at a value greater than the braking torque at the time when the prescribed condition is satisfied. In the braking / driving cooperative method, a torque demand value with respect to one of the driving torque generating device 10 and the braking torque generating device 20 is maintained at a value equal to the sum obtained by adding an offset value X to the torque demand value at the time when the prescribed condition is met, and the torque demand value output by the other device is calculated through feedback control. However, the present invention is not limited to this, and the torque demand value may be calculated by another method as long as the torque demand value with respect to one device is greater than the torque at the time when the prescribed condition is met.For example, the torque demand value with respect to the one device may be maintained at a value equal to the product obtained by multiplying the torque demand value at the time when the prescribed condition is satisfied by a predetermined gain factor (value greater than 1, e.g., 1.3). The vehicle may be equipped with wheel speed sensors for detecting the wheel speeds of the wheels FL, FR, RL, and RR, and the vehicle body speed of the vehicle may be calculated based on at least one of the wheel speeds of the respective wheels FL, FR, RL, and RR calculated based on the detection signals of the wheel speed sensors. When the control device 50 is applied to such a vehicle, a value obtained by time-deriving the wheel speed may be used as the longitudinal acceleration Gx. - The control device 50 can be applied to a vehicle that cannot acquire a gradient of a road surface on which the vehicle is traveling or a value corresponding to the gradient. In this case, it is determined that the prescribed condition is met when it is determined that the longitudinal acceleration target value GxTr is not determined to be oscillating and the longitudinal acceleration Gx is determined to be oscillating. - In the above-described embodiment, when the braking torque generating device is operated by the braking / driving cooperative method, the braking torque is applied to all of the FL, FR, RL, and RR wheels. However, when the vehicle can be decelerated by applying the braking torque, the braking torque can be applied only to some of the FL, FR, RL, and RR wheels (e.g., only to the front FL and FR wheels). The drive torque generating device 10 may be a device that can apply drive torque to the rear wheels RR and RL, or a device that can apply drive torque to all of the wheels FL, FR, RL, and RR. Furthermore, the drive torque generating device may be a device including the engine and the electric motor as a drive source of the vehicle, or a device including only the electric motor as a drive source of the vehicle. Additionally, the vehicle may be an in-wheel electric vehicle with a drive motor provided for each of the wheels FL, FR, RL, and RR as the drive torque generating device. In the above-described embodiment, the example in which the target acceleration setting unit 100 is provided in the vehicle was described. However, if the control device can receive the longitudinal acceleration target value GxTr, the target acceleration setting unit 100 may not be provided in the vehicle. For example, the target acceleration setting unit 100 may be provided on a portable terminal (e.g., a tablet PC, a smartphone, etc.) of the vehicle occupant or on a server external to the vehicle.In such a case, the vehicle is provided with a receiving unit for receiving the data concerning the longitudinal acceleration target value GxTr transmitted from the target acceleration setting unit 100, and the control device receives the data received by the receiving unit, so that the control device 50 can acquire the longitudinal acceleration target value GxTr and control the longitudinal acceleration Gx based on the longitudinal acceleration target value GxTr.

Claims

[1] A vehicle control device (50) applicable to a vehicle, the vehicle comprising: a drive torque generating device (10) which outputs a drive torque to wheels (FL, FR, RL, RR) of the vehicle; and a braking torque generating device that outputs a braking torque to the wheels (FL, FR, RL, RR) of the vehicle, wherein the vehicle control device (50) is configured to control a longitudinal acceleration of the vehicle based on a longitudinal acceleration target value (GxTr) of the vehicle, which is a target value of the longitudinal acceleration (Gx) of the vehicle, and wherein the vehicle control device (50) comprises: a determination unit (51) that determines whether prescribed conditions are met, including the condition that an amplitude of a vibration of the longitudinal acceleration target value (GxTr) is less than or equal to a first determination amplitude, and the condition that an amplitude of a vibration of the longitudinal acceleration (Gx) of the vehicle is greater than a second determination amplitude; and a cooperative control unit (523) which, based on the condition that it has been determined that the prescribed conditions are met, performs a braking-driving cooperative process to maintain a torque output from one of the driving torque generating device (10) or the braking torque generating device (20) at a larger value than the torque at the time at which the prescribed conditions were met, and to adjust the torque output from the other device by feedback control using the longitudinal acceleration target value (GxTr) and the longitudinal acceleration (Gx) of the vehicle. [2] The vehicle control device (50) according to claim 1, wherein the determination unit (51) determines that the prescribed conditions are satisfied when the amplitude of the oscillation of the longitudinal acceleration target value (GxTr) is less than or equal to the first determination amplitude, the amplitude of the oscillation of the longitudinal acceleration (Gx) of the vehicle is greater than the second determination amplitude, and an amplitude of a gradient equivalent value (Gθ), which is a value correlated with a gradient of a road surface on which the vehicle is traveling, is less than or equal to a third determination amplitude. [3] Vehicle control device (50) according to claim 1 or 2, wherein the drive torque generating device (10) includes a transmission (12) and is configured to transmit the drive torque output by a drive source (11) to the wheels (FL, FR, RL, RR) via the transmission (12), a gearshift control unit (521) is provided which, under the condition that the determination unit (51) determines that the prescribed conditions are met, carries out a shifting process for downshifting the transmission (12), and the cooperative control unit (523) performs the braking / driving cooperative process under the condition that a state in which the prescribed conditions are satisfied continues even when the shifting process is performed by the gearshift control unit (521). [4] Vehicle control device (50) according to claim 3, wherein the gearshift control unit (521) performs the shifting process under the condition that the prescribed conditions are met in a state in which the transmission (12) can be downshifted, and the cooperative control unit (523) performs the braking / driving cooperative process under the condition that a state in which the prescribed conditions are satisfied continues even when a shift stage of the transmission is brought to the lowest stage by executing the shift process by the gearshift control unit (521). [5] Vehicle control device (50) according to claim 3 or 4, wherein the gearshift control unit (521) performs the shifting process under the condition that the determination unit (51) determines that the prescribed conditions are met, when the braking torque is not output from the braking torque generating device (20) to the wheels (FL, FR, RL, RR), and the cooperative control unit (523) performs the braking / driving cooperative process under the condition that the determination unit (51) determines that the prescribed conditions are met when no braking torque is output to the wheels (FL, FR, RL, RR) from the braking torque generating device (20).

Images