JP4419978B2 - Vehicle motion control device - Google Patents

Description

  The present invention prevents excessive oversteer and excessive understeer by applying a braking force to each wheel regardless of whether or not the vehicle is in a braking state due to the operation of the brake pedal when the vehicle is turning. The present invention relates to a vehicle motion control device having a brake steering control function for suppressing control and an anti-skid control function for preventing a slip by controlling a braking force to the wheel so that the wheel is not locked during braking.

  Recently, as means for controlling vehicle motion characteristics, in particular, turning characteristics, means for directly controlling a turning moment by a left-right difference control of a braking force has been attracting attention and is being put into practical use. For example, Patent Document 1 proposes a motion control device that maintains the stability of a vehicle by a braking control unit that compensates for the influence of the lateral force of the vehicle. The apparatus is configured to control the braking force on the vehicle by the braking control means in accordance with the comparison result between the actual yaw rate and the target yaw rate. For example, the device reliably ensures the stability against the movement of the vehicle during cornering. Can be maintained. Thus, a braking force is applied to each wheel regardless of whether or not the braking state is caused by the operation of the brake pedal, and oversteer suppression control and understeer suppression control are performed by so-called braking steering control.

  Further, Patent Document 2 relates to a vehicle braking force control device in which a braking force according to the motion state of the vehicle is applied to each wheel so as to reestablish the behavior of the vehicle. The problem is to quickly and accurately correct the behavioral abnormality, and the following means are provided. That is, a feedforward control means for outputting a feedforward control signal corresponding to the target slip ratio, and a combined output means for synthesizing the feedforward control signal with the separately output feedback control signal and outputting it to the hydraulic control device are provided. .

Japanese Patent Laid-Open No. 2-70561 Japanese Patent Application Laid-Open No. 7-117654

  By the way, various functions such as an anti-skid control function for controlling the braking force by controlling the brake fluid pressure on the wheel cylinder according to the rotation state of each wheel so as to prevent the wheel from locking at the time of sudden braking of the vehicle have been conventionally provided. The above-described steering control function can be combined with these functions to effectively function as a motion control device.

  In this case, during the decompression operation for anti-kid control, decompression compensation processing for correcting the decompression amount is performed in order to prevent the decompression amount from becoming excessive and causing an excessive decrease in wheel acceleration and cornering force. . On the other hand, regarding the pressure increase control after the pressure reduction operation, the process of increasing the pressure according to the total pressure reduction so far is called the pressure increase compensation process, for example, based on the total pressure reduction time until the previous time, the wheel acceleration, the road surface friction coefficient, etc. Thus, the amount of pressure increase is corrected.

  However, since there is only one control mode that can be executed on each wheel of the vehicle, for example, when the anti-skid control mode is set when the brake steering control is performed on one wheel, the anti-skid control mode is controlled. Since the power cannot be increased, only the steering control by the pressure reducing operation is performed, but there is a contradiction that the braking force is reduced if the pressure is reduced too much. This occurs because the brake steering control is a control that applies a braking force to the wheels, whereas the anti-skid control is a control that reduces the braking force for the wheels having a lock tendency. In such a case, it is necessary to give priority to the anti-skid control mode, but it is not desirable to stop the steering control function.

  FIG. 16 is a μ-S characteristic diagram showing the relationship between the friction coefficient μ of the road surface and the cornering force CF and the slip ratio S. FIG. 17 shows the anti-skid control status for one wheel, and a to d are attached to the time points corresponding to the points a to d attached to the μ-S curve of FIG. In FIG. 17, Vso ** represents the estimated vehicle body speed, Vw ** represents the wheel speed, and Wc ** represents the wheel cylinder hydraulic pressure. 16 and 17, the point c is the peak value (μ peak) of the coefficient of friction and represents the start of the anti-kid control, the point d is the end point of the sudden decompression operation, and the point a is maintained (or the decompression operation). The point b represents the point at which the pressure increase compensation process should be terminated. As shown in FIG. 17, the area from point c to point a is the area where the pressure reduction compensation process is performed, and the area from point a to point b is the area where the pressure increase compensation process is performed.

  As can be seen from FIG. 16, the cornering force CF rapidly decreases in the process from the point a to the point d, so that steering control can be performed using this. At this time, in order to quickly reduce the cornering force CF, it is only necessary to quickly reach the points c to d. However, the transition from the point a to the point b after the pressure reducing operation is performed so as not to impair the anti-skid control ( It is important to perform the pressure increase compensation process quickly.

  Thus, when the braking steering control and the anti-skid control are simultaneously performed on the wheel to be controlled, that is, when the braking steering control is performed during the anti-skid control of the wheel to be controlled, or during the braking steering control. When skid control is performed, steering control can be performed without impairing anti-skid control by rapidly reducing the cornering force.

  Therefore, according to the present invention, when the braking steering control and the anti-skid control are simultaneously performed on the wheel to be controlled in the vehicle motion control device, the cornering force is quickly controlled so as to smoothly perform both the controls. It is an object to obtain a configuration to obtain.

In order to achieve the above object, according to the present invention, the brake fluid pressure of the wheel cylinder provided on each wheel of the vehicle is controlled according to the operation of the brake pedal at least to control each wheel. Brake hydraulic pressure control device for controlling power, vehicle state determination means for determining the motion state of the vehicle, and determination by the vehicle state determination means regardless of whether the vehicle is in a braking state due to operation of the brake pedal On the basis of the determination result of the vehicle state determination means, the brake steering control means for driving and controlling the brake fluid pressure control device based on the result and applying a braking force to each wheel of the vehicle to control the stability of the vehicle Anti-skid control means for controlling the braking fluid pressure control device according to the rotation state of each wheel during braking of the vehicle and controlling the braking force on each wheel to prevent slipping. The motion control device for a vehicle, to the wheels of one of the control object among the wheels of the vehicle, the brake fluid pressure control by the drive control and the brake steering control unit of the brake fluid pressure control apparatus according to the anti-skid control means When the drive control of the device is performed at the same time, the brake fluid pressure control device is controlled only by the anti-skid control means for the brake fluid pressure increasing speed after the pressure reducing operation by the brake fluid pressure control device. Pressure increasing compensation means for controlling the brake fluid pressure to be set larger than the pressure increasing speed of the brake fluid pressure after the pressure reducing operation by the brake fluid pressure control device .

As described in claim 2, the pressure increase compensation means includes drive control of the brake hydraulic pressure control device by the anti-skid control means and drive control of the brake hydraulic pressure control device by the brake steering control means. It is performed simultaneously, and the case the hydraulic control mode of the brake fluid pressure control apparatus for rapid pressure increase mode, between the surge pressure time, the drive control of the brake fluid pressure control apparatus according to only the anti-skid control means is performed, and The brake fluid pressure control device can be configured to be set longer than the rapid pressure increase time when the fluid pressure control mode is the rapid pressure increase mode .

Further, as the pressure increase compensation means, as described in claim 3, drive control of the brake hydraulic pressure control device by the anti-skid control means and drive control of the brake hydraulic pressure control device by the brake steering control means There are performed simultaneously, and the case the hydraulic control mode of the brake fluid pressure control device of the pulse pressure increase mode, the duty ratio, the driving control of the brake fluid pressure control apparatus according to only the anti-skid control means is performed, Further, the brake fluid pressure control device can be configured to be set to be larger than the duty ratio when the fluid pressure control mode is the pulse pressure increasing mode . Here, the pulse pressure increase is a control in which the pressure is gradually increased as a whole by repeating the operation and holding of the brake fluid pressure supply source and the wheel cylinder to increase pressure, and is also called step pressure increase.

  The brake fluid pressure control device includes an auxiliary fluid pressure source including, for example, a fluid pressure pump and an accumulator in addition to a master cylinder that outputs the brake fluid pressure according to the operation of the brake pedal, as shown in an embodiment described later. The brake fluid pressure can be output from the auxiliary fluid pressure source even when the brake pedal is not operated. The vehicle state determination means detects, for example, the wheel speed, wheel acceleration, vehicle body lateral acceleration, yaw rate, etc. of each wheel, and based on the detection results, the estimated vehicle body speed calculated based on the detection results, the vehicle body side slip angle, etc. The vehicle motion state can be determined, and the occurrence of excessive oversteer and excessive understeer, and the wheel lock state can be determined.

Since this invention is comprised as mentioned above, there exist the following effects. In other words, the vehicle motion control apparatus of the present invention is provided with a pressure increase compensation means, and for the wheel to be controlled , drive control of the brake hydraulic pressure control apparatus by the anti-skid control means and brake hydraulic pressure control by the brake steering control means. When the drive control of the device is performed at the same time, the brake fluid pressure increasing speed after the pressure reducing operation by the brake fluid pressure control device is set to the brake when the drive control of the brake fluid pressure control device is performed only by the anti-skid control means. Since it is configured to be controlled to be set larger than the pressure increase speed of the brake fluid pressure after the pressure reducing operation by the fluid pressure control device, the drive control of the brake fluid pressure control device by the anti-skid control means and the brake steering control means in also rapidly reducing the cornering force when the drive control of the brake fluid pressure control apparatus according to is carried out at the same time Can, it is possible to perform both control smoothly.

In the motion control apparatus according to claims 2 and 3, the pressure increase compensation means is configured to simultaneously perform drive control of the brake hydraulic pressure control apparatus by the anti-skid control means and drive control of the brake hydraulic pressure control apparatus by the brake steering control means. The rapid pressure increase time when it is performed is set longer than the sudden pressure increase time when the brake fluid pressure control device is driven only by the anti-skid control means, or the brake fluid pressure control device is driven by the anti-skid control means. The duty ratio when the control of the brake fluid pressure control device by the brake steering control means is simultaneously performed and the duty ratio when the drive control of the brake fluid pressure control device by the anti-skid control means alone is made larger It is configured to set, so you can quickly reduce the cornering force .

  Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of the configuration of an embodiment of a motion control apparatus according to the present invention. The brake fluid pressures of wheel cylinders Wfl, Wfr, Wrl, Wrr provided on each wheel FL, FR, RL, RR of a vehicle are shown. At least the brake fluid pressure control device PC that controls the braking force for each wheel by controlling the brake pedal BP according to the operation of the brake pedal BP, the vehicle state determination means DR that determines the motion state of the vehicle, and the determination of the vehicle state determination means DR Based on the determination result of the brake steering control means ST that drives and controls the brake fluid pressure control device PC and applies braking force to each wheel of the vehicle to control the stability of the vehicle and the determination result of the vehicle state determination means DR. Anti-skid control means AB for preventing slip by controlling the brake hydraulic pressure control device PC according to the rotation state of each wheel during braking and controlling the braking force on each wheel. There. Then, when the control by the anti-skid control means AB and the control by the brake steering control means ST are simultaneously performed on one of the wheels of the vehicle to be controlled, after the pressure reduction operation by the brake hydraulic pressure control device PC. The pressure increase compensation means PM is provided for controlling the pressure increase speed of the brake fluid pressure to be larger than the pressure increase speed at the time of control only by the anti-skid control means AB.

  As the pressure increase compensation means PM, when the control by the anti-skid control means AB and the control by the brake steering control means ST are simultaneously performed and the control mode of the brake fluid pressure control device PC is the rapid pressure increase mode, the rapid pressure increase The time can be set to be longer than the rapid pressure increase time at the time of control only by the anti-skid control means AB. Further, as the pressure increase compensation means PM, when the control by the anti-skid control means AB and the control by the brake steering control means ST are performed at the same time and the control mode of the brake fluid pressure control device PC is the pulse pressure increase mode, The duty ratio may be set to be larger than the duty ratio at the time of control by only the anti-skid control means AB.

  As shown in FIG. 2, the engine EG of the present embodiment is an internal combustion engine having a throttle control device TH and a fuel injection device FI. In the throttle control device TH, the main throttle valve is operated in accordance with the operation of the accelerator pedal AP. The main throttle opening of the MT is controlled. Further, according to the output of the electronic control unit ECU, the sub-throttle valve ST of the throttle control unit TH is driven to control the sub-throttle opening, and the fuel injection unit FI is driven to control the fuel injection amount. It is configured. The engine EG of the present embodiment is connected to the wheels RL and RR on the rear side of the vehicle via a speed change control device GS and a differential gear DF, so that a so-called rear wheel drive system is configured. It is not limited to.

  Regarding the braking system, wheel cylinders Wfl, Wfr, Wrl, Wrr are mounted on the wheels FL, FR, RL, RR, respectively, and a brake fluid pressure control device PC is connected to these wheel cylinders Wfl. The brake fluid pressure control device PC will be described later with reference to FIG. Note that the wheel FL indicates the front left wheel as viewed from the driver's seat, the wheel FR indicates the front right side, the wheel RL indicates the rear left side, and the wheel RR indicates the rear right wheel.

  As shown in FIG. 2, wheel speed sensors WS1 to WS4 are disposed on the wheels FL, FR, RL, and RR, and these are connected to the electronic control unit ECU, and the rotational speed of each wheel, that is, the wheel speed is determined. A pulse signal with a proportional number of pulses is input to the electronic control unit ECU. Furthermore, the brake switch BS that is turned on when the brake pedal BP is depressed, the front wheel steering angle sensor SSf that detects the steering angle δf of the wheels FL and FR in front of the vehicle, the lateral acceleration sensor YG that detects the lateral acceleration of the vehicle, and the vehicle A yaw rate sensor YS for detecting the yaw rate is connected to the electronic control unit ECU. In the yaw rate sensor YS, the changing speed of the vehicle rotation angle (yaw angle) around the vertical axis passing through the center of gravity of the vehicle, that is, the yaw angular velocity (yaw rate) is detected and output to the electronic control unit ECU as the actual yaw rate γ.

  Since the actual yaw rate γ can be estimated based on the wheel speed difference Vfd (= Vwfr−Vwfl) between the left and right wheels on the driven wheel side (wheels FL and FR in front of the vehicle in this embodiment), the wheel speed sensor WS1. If the detection output of WS2 is used, the yaw rate sensor YS can be omitted. Further, a steering angle control device (not shown) may be provided between the wheels RL and RR. According to this, the steering of the wheels RL and RR is performed by a motor (not shown) according to the output of the electronic control unit ECU. The angle can also be controlled.

  As shown in FIG. 2, the electronic control unit ECU according to the present embodiment includes a microcomputer CMP including a processing unit CPU, a memory ROM, a RAM, an input port IPT, an output port OPT, and the like connected to each other via a bus. ing. Output signals from the wheel speed sensors WS1 to WS4, the brake switch BS, the front wheel steering angle sensor SSf, the yaw rate sensor YS, the lateral acceleration sensor YG, etc. are input to the processing unit CPU from the input port IPT via the amplifier circuit AMP. It is configured. Further, control signals are output from the output port OPT to the throttle control device TH and the brake fluid pressure control device PC via the drive circuit ACT. In the microcomputer CMP, the memory ROM stores a program for various processes including the flowcharts shown in FIGS. 4 to 8, and the processing unit CPU executes the program while an ignition switch (not shown) is closed. The memory RAM temporarily stores variable data necessary for executing the program. It should be noted that a plurality of microcomputers may be configured for each control such as throttle control or a combination of related controls as appropriate, and electrically connected to each other.

  FIG. 3 shows an example of the brake fluid pressure control device PC in the present embodiment, and the master cylinder MC and the fluid pressure booster HB are driven according to the operation of the brake pedal BP. An auxiliary hydraulic pressure source AP is connected to the hydraulic pressure booster HB, and these are connected to the low pressure reservoir RS together with the master cylinder MC.

  The auxiliary hydraulic pressure source AP has a hydraulic pump HP and an accumulator Acc. The hydraulic pump HP is driven by the electric motor M, boosts and outputs the brake fluid in the low pressure reservoir RS, and the brake fluid is supplied to the accumulator Acc via the check valve CV6 and accumulated. The electric motor M is driven in response to the hydraulic pressure in the accumulator Acc falling below a predetermined lower limit value, and stops in response to the hydraulic pressure in the accumulator Acc exceeding a predetermined upper limit value. A relief valve RV is interposed between the accumulator Acc and the low pressure reservoir RS. Thus, a so-called power hydraulic pressure is appropriately supplied from the accumulator Acc to the hydraulic pressure booster HB. The hydraulic booster HB receives the output hydraulic pressure of the auxiliary hydraulic pressure source AP, adjusts the output hydraulic pressure of the master cylinder MC to the booster hydraulic pressure proportional to the pilot hydraulic pressure, and thereby the master cylinder MC Boosted.

  Solenoid valves SA1 and SA2 are interposed in the hydraulic pressure passages on the front wheel side connecting the master cylinder MC and the wheel cylinders Wfr and Wfl in front of the vehicle, and these are respectively connected via control passages Pfr and Pfl. The electromagnetic on-off valves PC1, PC5 and the electromagnetic on-off valves PC2, PC6 are connected. In addition, an electromagnetic on-off valve SA3 and supply / discharge control electromagnetic on-off valves PC1 to PC8 are interposed in the hydraulic pressure passages connecting the hydraulic booster HB and the wheel cylinder Wfr, etc., and proportional to the rear wheel side. A pressure reducing valve PV is interposed. The auxiliary hydraulic pressure source AP is connected to the downstream side of the electromagnetic on-off valve SA3 via the electromagnetic on-off valve STR. In FIG. 3, the front and rear pipes are divided into a front wheel hydraulic pressure control system and a rear wheel hydraulic pressure control system, but a so-called X pipe may be used.

  In the front wheel side hydraulic system, the electromagnetic on-off valves PC1 and PC2 are connected to the electromagnetic on-off valve STR. The electromagnetic open / close valve STR is a 2-port 2-position electromagnetic open / close valve, which is in a shut-off state at the closed position when not in operation, and directly connects the electromagnetic open / close valves PC1 and PC2 to the accumulator Acc at the open position during operation. The electromagnetic switching valve SA1 and the electromagnetic switching valve SA2 are three-port and two-position electromagnetic switching valves. When not operating, the wheel cylinders Wfr and Wfl are connected to the master cylinder MC in the first position shown in FIG. However, when the solenoid coil is excited and switched to the second position, the wheel cylinders Wfr and Wfl are both disconnected from the master cylinder MC and communicated with the electromagnetic on-off valves PC1 and PC5 and the electromagnetic on-off valves PC2 and PC6, respectively. To do.

  The check valves CV1 and CV2 are connected in parallel to the electromagnetic on-off valves PC1 and PC2. The inflow side of the check valve CV1 is connected to the control passage Pfr, and the inflow side of the check valve CV2 is connected to the control passage Pfl. ing. When the electromagnetic switching valve SA1 is in the operating position (second position) and the brake pedal BP is released, the check valve CV1 reduces the brake hydraulic pressure of the wheel cylinder Wfr to the output hydraulic pressure of the hydraulic booster HB. The brake fluid flow in the direction of the hydraulic booster HB is allowed but the reverse flow is blocked. The same applies to the check valve CV2.

  Next, the rear-wheel hydraulic system will be described. The electromagnetic on-off valve SA3 is a two-port 2-position electromagnetic on-off valve, and is in the open position shown in FIG. The hydraulic booster HB communicates with the valve PV. At this time, the electromagnetic on-off valve STR is closed and communication with the accumulator Acc is blocked. When the electromagnetic on-off valve SA3 is switched to the closed position during operation, the electromagnetic on-off valves PC3 and PC4 are disconnected from the hydraulic pressure booster HB and connected to the electromagnetic on-off valve STR via the proportional pressure reducing valve PV. The on-off valve STR communicates with the accumulator Acc when activated.

  Further, check valves CV3 and CV4 are connected in parallel to the electromagnetic on-off valves PC3 and PC4. The inflow side of the check valve CV3 is connected to the wheel cylinder Wrr, and the inflow side of the check valve CV4 is connected to the wheel cylinder Wrl. Has been. These check valves CV3 and CV4 are provided to cause the brake fluid pressure of the wheel cylinders Wrr and Wrl to quickly follow the decrease in the output fluid pressure of the fluid pressure booster HB when the brake pedal BP is released. Thus, the flow of brake fluid in the direction of the electromagnetic on-off valve SA3 is allowed and the flow in the reverse direction is blocked. Further, the check valve CV5 is provided in parallel with the electromagnetic on-off valve SA3, and even when the electromagnetic on-off valve SA3 is in the closed position, the brake pedal BP can be stepped on.

  The electromagnetic switching valves SA1 and SA2, the electromagnetic on-off valves SA3 and STR, and the electromagnetic on-off valves PC1 to PC8 are driven and controlled by the electronic control unit ECU described above, and various controls including not only anti-skid control but also braking steering control are performed. Done. For example, when it is determined that the vehicle is excessively oversteered during a turning motion, for example, a braking force is applied to the front wheels on the outside of the turn, and an outward yaw moment to the vehicle, that is, a yaw moment that directs the vehicle to the outside of the turn is generated. Controlled to occur. This is called oversteer suppression control and is also called stability control. Further, when it is determined that the vehicle is excessively understeered during the turning motion, in the case of a rear wheel drive vehicle as in this embodiment, a braking force is applied to the front wheels and the rear two wheels on the outer side of the turning, and the vehicle is inwardly directed toward the vehicle. The yaw moment, that is, the yaw moment that directs the vehicle toward the inside of the turn is generated. This is called understeer suppression control and is also called course trace control. The oversteer suppression control and the understeer suppression control are collectively referred to as braking steering control.

  Thus, during the brake steering control performed when the brake pedal BP is not operated, the brake hydraulic pressure is not output from the hydraulic pressure booster HB and the master cylinder MC, so that the electromagnetic switching valves SA1 and SA2 are in the second position. Then, the electromagnetic on-off valve SA3 is set to the closed position, and the electromagnetic on-off valve STR is set to the open position. As a result, the output power hydraulic pressure of the auxiliary hydraulic pressure source AP can be supplied to the wheel cylinder Wfr and the like via the electromagnetic on-off valve STR and the open electromagnetic on-off valves PC1 to PC8. As described above, when the electromagnetic on-off valves PC1 to PC8 are appropriately opened and closed, the brake fluid pressure in each wheel cylinder is suddenly increased, pulse increased (slowly increased), pulse reduced (slowly reduced), suddenly reduced, and The holding state is set, and the above-described oversteer suppression control and / or understeer suppression control is performed.

  In the present embodiment configured as described above, a series of processing such as braking steering control and anti-skid control is performed by the electronic control unit ECU, and when an ignition switch (not shown) is closed, FIGS. Execution of the program corresponding to the flowchart of FIG. FIG. 4 shows the motion control operation of the vehicle. First, in step 101, the microcomputer CMP is initialized, and various calculation values are cleared. Next, at step 102, detection signals from the wheel speed sensors WS1 to WS4 are read, a detection signal from the front wheel steering angle sensor SSf (steering angle δf), a detection signal from the yaw rate sensor YS (actual yaw rate γ), and a lateral acceleration sensor YG. The detection signal (that is, the actual lateral acceleration, expressed as Gya) is read.

Subsequently, the process proceeds to step 103, where the wheel speed Vw ** (** represents each wheel FR) of each wheel is calculated, and these are differentiated to obtain the wheel acceleration DVw ** of each wheel. Subsequently, in step 104, the maximum value of the wheel speed Vw ** of each wheel is calculated as the estimated vehicle body speed Vso at the center of gravity of the vehicle (Vso = MAX (Vw **)). Further, the estimated vehicle body speed Vso ** is obtained for each wheel based on the wheel speed Vw ** of each wheel, and normalization is performed as necessary to reduce errors based on the difference between the inner and outer wheels when turning the vehicle. . Further, the estimated vehicle speed Vso is differentiated, and the estimated vehicle acceleration DVso at the vehicle center of gravity is calculated. In step 105, based on the wheel speed Vw ** and estimated vehicle speed Vso ** (or normalized estimated vehicle speed) obtained in steps 103 and 104, the actual slip ratio Sa ** of each wheel. Is obtained as Sa ** = (Vso **-Vw **) / Vso **. Next, at step 106, the road surface friction coefficient μ is approximately set to (DVso ² + Gya ² ) ^1/2 based on the estimated vehicle body acceleration DVso at the vehicle center of gravity and the actual lateral acceleration Gya of the detection signal of the lateral acceleration sensor YG. Desired. Furthermore, as a means for detecting the road surface friction coefficient, various means such as a sensor for directly detecting the road surface friction coefficient can be used.

Subsequently, at step 107, the vehicle body side slip angular velocity Dβ is calculated, and at step 108, the vehicle body side slip angle β is calculated. The vehicle body side slip angle β represents the slip of the vehicle body with respect to the traveling direction of the vehicle as an angle, and can be calculated and estimated as follows. That is, the vehicle body side slip angular velocity Dβ is a differential value dβ / dt of the vehicle body side slip angle β and can be obtained as Dβ = Gy / Vso−γ in step 107, and is integrated in step 108 to obtain β = ∫ (Gy The vehicle body side slip angle β can be obtained as / Vso−γ) dt. Gy represents the lateral acceleration of the vehicle, Vso represents the estimated vehicle body speed at the vehicle center of gravity, and γ represents the yaw rate. Alternatively, β = tan ⁻¹ (Vy / Vx) can be obtained based on the ratio of the vehicle speed Vx in the traveling direction and the vehicle speed Vy in the lateral direction perpendicular thereto.

  Then, the process proceeds to step 109, where the brake steering control process is performed, and a target slip ratio to be used for the brake steering control is set as will be described later, and the brake fluid is controlled according to the driving state of the vehicle by the hydraulic servo control at step 117 described later. The pressure controller PC is controlled to control the braking force for each wheel. This braking steering control is superimposed on the control in all control modes described later. Thereafter, the routine proceeds to step 110, where it is determined whether or not the anti-skid control start condition is satisfied. If the start condition is satisfied and it is determined that the anti-skid control is started at the time of braking, the control mode is set in step 111 for performing both the brake steering control and the anti-skid control.

  When it is determined in step 110 that the anti-skid control start condition is not satisfied, the routine proceeds to step 112, where it is determined whether or not the front / rear braking force distribution control start condition is satisfied. If it is determined that the control is to be started, the process proceeds to step 113 and the control mode is set to perform both the brake steering control and the front / rear braking force distribution control. If not satisfied, the process proceeds to step 114 and the traction control start condition is satisfied. It is determined whether or not. If it is determined that the traction control is started at the time of the brake steering control, the control mode is set in step 115 to perform both the brake steering control and the traction control. If no control is determined to be started at the time of the brake steering control, In Step 116, it is determined whether or not the brake steering control start condition is satisfied. When it is determined that the brake steering control is started, the process proceeds to step 117, and the control mode is set to perform only the brake steering control. Then, hydraulic servo control is performed in step 118 based on these control modes, and the process returns to step 102. If it is determined in step 116 that the brake steering control start condition is not satisfied, the solenoids of all the solenoid valves are turned off in step 119, and then the process returns to step 102. Note that, based on steps 111, 113, 115, and 117, if necessary, the sub-throttle opening of the throttle control device TH is adjusted according to the driving state of the vehicle, the output of the engine EG is reduced, and the driving force is limited. You may comprise as follows.

  In the anti-skid control mode, as described above, the braking force applied to each wheel is controlled so that the wheel is not locked during vehicle braking. In the front / rear braking force distribution control mode, the distribution of the braking force applied to the rear wheels to the braking force applied to the front wheels is controlled so that the stability of the vehicle is maintained when the vehicle is braked. In the traction control mode, braking force is applied to the driving wheel and throttle control is performed so as to prevent slipping of the driving wheel during driving of the vehicle, and the driving force for the driving wheel is controlled by these controls. The

  FIG. 5 shows the specific processing contents of the target slip ratio setting in the brake steering control process of step 109 in FIG. 4. The brake steering control includes oversteer suppression control and understeer suppression control. A target slip ratio is set according to oversteer suppression control and / or understeer suppression control. First, in steps 201 and 202, oversteer suppression control and understeer suppression control start / end determination is performed.

  The start / end determination of the oversteer suppression control performed in step 201 is performed based on whether or not the control region is indicated by the hatched area in FIG. That is, the oversteer suppression control is started when entering the control region according to the values of the vehicle body side slip angle β and the vehicle body side slip angular velocity Dβ at the time of determination, and the oversteer suppression control is terminated when the control region is exited. Controlled as shown by the arrow curve. Therefore, the boundary between the control region and the non-control region (indicated by a two-dot chain line in FIG. 9) corresponds to the boundary of the start region. Further, as will be described later, the braking force of each wheel is controlled so that the control amount becomes larger as it moves away from the boundary indicated by the two-dot chain line in FIG. 9 toward the control region.

  On the other hand, the start / end determination of the understeer suppression control performed in step 202 is performed based on whether or not it is in the control region indicated by hatching in FIG. That is, understeering suppression control is started when the control region is deviated from the ideal state indicated by the alternate long and short dash line in accordance with the change in the actual lateral acceleration Gya with respect to the target lateral acceleration Gyt at the time of determination. Is finished, and the control is performed as shown by the arrow curve in FIG.

  Subsequently, it is determined in step 203 whether or not oversteer suppression control is being controlled. If not in control, it is determined in step 204 whether or not understeer suppression control is being controlled. Return to the main routine. When it is determined in step 204 that the understeer suppression control is performed, the routine proceeds to step 205, where the target slip ratio of each wheel is set for understeer suppression control described later. If it is determined in step 203 that the oversteer suppression control is performed, the process proceeds to step 206, in which it is determined whether the understeer suppression control is performed. Set for. When it is determined in step 206 that understeer suppression control is being performed, oversteer suppression control and understeer suppression control are performed simultaneously, and in step 208, a target slip ratio for simultaneous control is set.

The vehicle body side slip angle β and the vehicle body side slip angular velocity Dβ are used for setting the target slip ratio for oversteer suppression control in step 207. Further, the difference between the target lateral acceleration Gyt and the actual lateral acceleration Gya is used for setting the target slip ratio in the understeer suppression control. This target lateral acceleration Gyt is obtained based on Gyt = γ (θf) · Vso. Here, γ (θf) is obtained as γ (θf) = {θf / (N · L)} · Vso / (1 + Kh · Vso ² ), Kh is a stability factor, N is a steering gear ratio, and L is a wheelbase. Represents.

  In step 205, the target slip ratio of each wheel is set such that the front wheel outside the turn is set to Stufo, the rear wheel outside the turn is set to Sturo, and the rear wheel inside the turn is set to Sturi. Regarding the sign of the slip ratio (S) shown here, “t” represents “target” and is compared with “a” representing “actual measurement” described later. “u” represents “understeer suppression control”, “r” represents “rear wheel”, “o” represents “outside”, and “i” represents “inside”.

  The target slip ratio of each wheel in step 207 is set such that the front wheel outside the turn is set to Stefo, the rear wheel outside the turn is set to Stero, and the rear wheel inside the turn is set to Steri. Here, “e” represents “oversteer suppression control”. In step 208, the target slip ratio of each wheel is set such that the front wheel outside the turn is set to Stefo, the rear wheel outside the turn is set to Sturo, and the rear wheel inside the turn is set to Sturi. That is, when oversteer suppression control and understeer suppression control are performed simultaneously, the front wheels on the outside of the turn are set in the same manner as the target slip ratio of oversteer suppression control, and the rear wheels are set in the same manner as the target slip ratio of understeer suppression control. Is set. In any case, the front wheels on the inner side of the turn (that is, the driven wheels in the rear wheel drive vehicle) are not controlled for setting the estimated vehicle body speed.

  The target slip rate Stefo for the turning outer front wheel used for oversteer suppression control is set as Stefo = K1 · β + K2 · Dβ, and the target slip rate Stero for the turning outer rear wheel is set as Stero = K3 · β + K4 · Dβ. The rate Steri is set as Steri = K5 · β + K6 · Dβ. Here, K1 to K6 are constants, and the target slip ratios Stefo and Stero for the wheels on the outer side of the turn are set to values for controlling the pressurizing direction (the direction in which the braking force is increased). On the other hand, the target slip ratio Steri for the wheel on the inside of the turn is set to a value that controls the pressure reducing direction (direction in which the braking force is reduced).

  On the other hand, the target slip ratio used for understeer suppression control is set as follows based on the deviation ΔGy between the target lateral acceleration Gyt and the actual lateral acceleration Gya. That is, the target slip ratio Stefo for the front wheels outside the turn is set as K7 · ΔGy, and the constant K7 is set to a value for controlling the pressurizing direction (or the depressurizing direction). Further, the target slip ratios Sturo and Sturi for the rear wheels are set to K8 · ΔGy and K9 · ΔGy, respectively, and the constants K8 and K9 are both set to values for controlling the pressurizing direction.

  6 and 7 show the processing contents of the hydraulic servo control performed at step 118 of FIG. 4, and the slip ratio servo control of the wheel cylinder hydraulic pressure is performed for each wheel. First, the target slip ratio St ** set in the above-described step 205, 207 or 208 is read in step 301, and these are read as they are as the target slip ratio St ** of each wheel. Next, the routine proceeds to step 302, where it is determined whether or not anti-skid control is in progress. If so, at step 303, a predetermined limit is imposed on the target slip ratio St ** as shown in FIG.

  That is, when the target slip ratio St ** set based on the vehicle body side slip angle β from the request in the brake steering control exceeds 20%, the anti-skid control is set to 20% or less. Accordingly, the process proceeds to step 304, where the target slip ratio St ** is updated by adding the slip ratio correction amount ΔSs ** for anti-skid control to the target slip ratio St **. If the anti-skid control is not in progress, the routine proceeds to step 305, where it is determined whether the front / rear braking force distribution control is in progress. If it is determined in step 305 that the front / rear braking force distribution control is being performed, the slip ratio correction amount ΔSb ** is added to the target slip ratio St ** and updated in step 306, otherwise the process proceeds to step 307.

  In step 307, it is determined whether or not traction control is in progress. If so, the slip ratio correction amount ΔSr ** is added to the target slip ratio St ** and updated in step 308. After the target slip ratio St ** is updated in Steps 304, 306, and 308, or when it is determined that the traction control is not being performed in Step 307, the process proceeds to Step 309 and the slip ratio deviation ΔSt ** is determined for each wheel. And at step 310, the vehicle body acceleration deviation ΔDVso ** is calculated. 6 illustrates the anti-skid control, the front / rear braking force distribution control, and the traction control, but the target slip ratio St ** is similarly set for each control listed in FIGS.

  In step 309, the difference between the target slip ratio St ** and the actual slip ratio Sa ** of each wheel is calculated to obtain the slip ratio deviation ΔSt ** (ΔSt ** = St ** − Sa **). In step 310, the difference between the estimated vehicle body acceleration DVso at the vehicle center of gravity position and the wheel acceleration DVw ** at the wheel to be controlled is calculated to obtain the vehicle body acceleration deviation ΔDVso **. The actual slip rate Sa ** and the vehicle body acceleration deviation ΔDVso ** of each wheel at this time have different calculations depending on the control mode such as anti-skid control and traction control, but the description thereof will be omitted.

  Subsequently, the process proceeds to step 311 where the slip ratio deviation ΔSt ** is compared with a predetermined value Ka. If the slip ratio deviation ΔSt ** is equal to or greater than the predetermined value Ka, the integrated value of the slip ratio deviation ΔSt ** is updated at step 312. That is, a value obtained by multiplying the current slip rate deviation ΔSt ** by the gain GI ** is added to the previous slip rate deviation integrated value IΔSt **, thereby obtaining the current slip rate deviation integrated value IΔSt **. When the slip ratio deviation | ΔSt ** | is less than the predetermined value Ka, the slip ratio deviation integrated value IΔSt ** is cleared (0) in step 313. Next, in steps 314 to 317 in FIG. 7, the slip ratio deviation integral value IΔSt ** is limited to a value not more than the upper limit value Kb and not less than the lower limit value Kc, and when it exceeds the upper limit value Kb, it is set to Kb. If it falls below Kc, it is set to Kc, and then the process proceeds to step 318.

  In step 318, one parameter Y ** used for brake fluid pressure control in each control mode is calculated as Gs ** · (ΔSt ** + IΔSt **). Here, Gs ** is a gain, which is set according to the vehicle body side slip angle β as shown by a solid line in FIG. In step 319, another parameter X ** used for brake fluid pressure control is calculated as Gd ** · ΔDVso **. The gain Gd ** at this time is a constant value as shown by a broken line in FIG.

  Thereafter, the process proceeds to step 320, and the hydraulic pressure control mode is set for each wheel according to the control map shown in FIG. 11 based on the parameters X ** and Y **. In FIG. 11, each of a sudden pressure reduction region, a pulse pressure reduction region, a holding region, a pulse pressure increase region, and a sudden pressure increase region is set in advance, and in step 320, according to the values of parameters X ** and Y **. It is determined which region corresponds to this. In the non-control state, the hydraulic pressure control mode is not set (solenoid off). Further, when the region determined this time in step 320 is switched from pressure increase to pressure reduction or pressure reduction to pressure increase with respect to the region determined last time, step 321 performs pressure increase / decrease compensation processing. Will be described later. In step 322, the solenoid of each solenoid valve constituting the brake fluid pressure control device PC is driven according to the fluid pressure control mode, and the braking force of each wheel is controlled.

  FIG. 8 shows the contents of the pressure increase compensation processing of the pressure increase / decrease compensation processing executed in step 321. First, in step 401, a control mode for performing both control of braking steering control and anti-skid control ( It is determined whether it is set in step 111 of FIG. If it is determined that the control mode of “braking steering control + anti-skid control” is set, the process proceeds to step 402, where it is determined whether or not it is the rapid pressure increasing mode. It is determined whether or not the pulse pressure increasing mode is set. Thus, if it is the rapid pressure increasing mode, the rapid pressure increasing time is corrected in step 404, and if it is the pulse pressure increasing mode, the pressure increasing gradient is corrected in step 405.

  The correction of the rapid pressure increase time executed in step 404 is to set the rapid pressure increase time in the control mode of “braking steering control + anti-skid control” longer than the rapid pressure increase time in the control mode of only anti-skid control. Is done by. For example, the target hydraulic pressure coefficient at the time of wheel cylinder hydraulic pressure recovery set according to the total pressure reduction time until the previous time is set to Kt times (for example, Kt = 1.2). Specifically, the current rapid pressure increase time is set to Kt times in the control mode of only the anti-skid control.

  On the other hand, the correction of the pressure increase gradient in the pulse pressure increase mode executed in the above step 405 is based on FIGS. 14 and 15 and the duty ratio in the control mode of “braking steering control + anti-skid control” is changed to anti-skid. This is performed by setting the duty ratio larger than that in the control mode of only control. Specifically, the pressure increasing time (solenoid valve on time) is set as shown in FIG. 14 according to the number of times of pulse pressure increasing. Further, according to the hydraulic pressure difference between the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure, the period of the pulse pressure increasing signal is set as shown in FIG.

  Thereafter, the process proceeds to step 406, where various pressure increase / decrease compensation processes such as the pressure increase / decrease compensation process in the control mode of only the anti-skid control, the pressure increase / decrease compensation process accompanying the fluctuation of the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure are performed. Since these are not directly related to the present invention, description thereof will be omitted.

  Thus, the target slip ratio St ** is rapidly increased by the processing of the above-described steps 404 and 405 and quickly reaches the points c to d in FIG. 16 (beyond the μ peak), and the cornering force CF is rapidly reduced. This enables steering control even during anti-skid control. Moreover, since the upper limit value of the target slip ratio St ** is set in step 303, excessive control is prevented.

It is a block diagram which shows the outline | summary of one Embodiment of the vehicle motion control apparatus of this invention. 1 is an overall configuration diagram of an embodiment of a motion control device of the present invention. It is a block diagram which shows an example of the brake fluid pressure control apparatus in one Embodiment of this invention. It is a flowchart which shows the whole motion control of the vehicle in one Embodiment of this invention. It is a flowchart which shows the brake steering control process in one Embodiment of this invention. It is a flowchart which shows the process of the hydraulic-pressure servo control in one Embodiment of this invention. It is a flowchart which shows the process of the hydraulic-pressure servo control in one Embodiment of this invention. It is a flowchart which shows the pressure increase / decrease compensation process in one Embodiment of this invention. It is a graph which shows the start / end determination area | region of the oversteer suppression control in one Embodiment of this invention. It is a graph which shows the start / end determination area | region of the understeer suppression control in one Embodiment of this invention. It is a graph which shows the relationship between the parameter used for brake hydraulic pressure control, and hydraulic pressure control mode in one Embodiment of this invention. It is a graph which shows the relationship between the vehicle body side slip angle and the gain for parameter calculation in one Embodiment of this invention. 6 is a graph showing a relationship between a vehicle body side slip angle β and a target slip ratio St ** during anti-skid control in an embodiment of the present invention. In one embodiment of the present invention, it is a graph which shows the relation between the number of times of execution of pulse pressure increase, and the pressure increase time of a pulse pressure increase signal. In one Embodiment of this invention, it is a graph which shows the relationship between the hydraulic pressure difference of a master cylinder hydraulic pressure and a wheel cylinder hydraulic pressure, and the period of a pulse pressure increase signal. It is a graph which shows the relationship between a road surface friction coefficient and a slip ratio. It is a graph which shows the anti-skid control condition with respect to one wheel.

Explanation of symbols

BP Brake pedal BS Brake switch MC Master cylinder HB Hydraulic booster Wfr, Wfl, Wrr, Wrl Wheel cylinder WS1-WS4 Wheel speed sensor FR, FL, RR, RL Wheel PC Brake hydraulic pressure control device ST Sub throttle valve EG Engine GS Shift Control device YS Yaw rate sensor YG Lateral acceleration sensor FI Fuel injection device DF Differential gear SSf Front wheel rudder angle sensor CMP Microcomputer IPT Input port OPT Output port ECU Electronic control device

Claims (3)

A brake fluid pressure control device for controlling the braking force on each wheel by controlling the brake fluid pressure of a wheel cylinder provided on each wheel of the vehicle according to the operation of the brake pedal at least, and a vehicle state for determining the motion state of the vehicle Regardless of whether or not the vehicle is in a braking state due to the operation of the determination means and the brake pedal, the brake fluid pressure control device is driven and controlled based on the determination result of the vehicle state determination means, and braking force is applied to each wheel of the vehicle. And a brake steering control means for controlling the stability of the vehicle by driving the brake hydraulic pressure control device according to the rotation state of each wheel during braking of the vehicle based on the determination result of the vehicle state determination means An anti-skid control means for controlling and controlling the braking force on each wheel to prevent slipping, comprising: controlling one of the wheels of the vehicle. To a wheel of the subject, when the drive control of the brake fluid pressure control apparatus are carried out simultaneously by the brake steering control means and the drive control of the brake fluid pressure control apparatus according to the anti-skid control means, the brake fluid pressure control device The brake fluid pressure increase rate after the pressure reducing operation by the brake fluid pressure after the pressure reducing operation by the brake fluid pressure control device when the drive control of the brake fluid pressure control device is performed only by the anti-skid control means. A vehicle motion control apparatus, comprising: a pressure increase compensation unit configured to control the pressure increase speed to be set larger than the pressure increase speed. The pressure increase compensating means simultaneously performs drive control of the brake hydraulic pressure control device by the anti-skid control means and drive control of the brake hydraulic pressure control device by the brake steering control means, and the brake hydraulic pressure control If the device fluid pressure control mode is the rapid pressure increase mode, between the surge pressure time, the drive control of the anti-skid control unit only by said brake fluid pressure control device is performed, and hydraulic control of the brake fluid pressure control device 2. The motion control apparatus for a vehicle according to claim 1, wherein the mode is set to be longer than the rapid pressure increase time when the mode is the rapid pressure increase mode . The pressure increase compensating means simultaneously performs drive control of the brake hydraulic pressure control device by the anti-skid control means and drive control of the brake hydraulic pressure control device by the brake steering control means, and the brake hydraulic pressure control If the device the hydraulic control mode of the pulse increase mode, the duty ratio, the driving control of the anti-skid control unit only by said brake fluid pressure control device is performed, and hydraulic control of the brake fluid pressure control device 2. The vehicle motion control device according to claim 1, wherein the mode is set to be larger than a duty ratio when the mode is a pulse pressure increasing mode .

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