JP2015127159A - Vehicle behavior control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle behavior control device which can suppress the occurrence of an under-steer state during the control of a vehicle behavior by properly adjusting a brake force for suppressing an over-steer state.SOLUTION: A control part 100 of a vehicle behavior control device comprises: steering angle speed calculation means 130 which acquires a steering angle speed ω; lateral acceleration acquisition means 111 which acquires lateral acceleration AY; and behavior stabilization control means 160 which performs behavior stabilization control for stabilizing a behavior of a vehicle by imparting brake forces to turning outside wheels of the vehicle by a set target brake force. The behavior stabilization means 160 has a target fluid pressure setting part 168 which sets a target brake force, and a lateral acceleration storage part 167 which stores the lateral acceleration AY when abrupt steering is performed. When the lateral acceleration AY stored by the lateral acceleration storage part 167 exceeds a lateral acceleration threshold, the target fluid pressure setting part 168 sets an upper limit of the target brake force small as the lateral acceleration AY stored by the lateral acceleration storage part 167 is larger.

Description

  The present invention relates to a vehicle behavior control device that stabilizes the behavior of a vehicle.

  As a behavior stabilization control device that stabilizes the behavior of the vehicle, when an oversteer condition occurs due to the steering being suddenly steered while the vehicle is traveling straight, the oversteer condition is set by applying braking force to the turning outer wheel of the vehicle. What is comprised so that it may suppress is known (for example, refer patent document 1).

JP 2010-64720 A

  By the way, in the conventional vehicle behavior control device, even when the vehicle is suddenly steered while the vehicle is turning, the same braking force as that when the vehicle is steered straight is applied to the wheels, so the oversteer state is excessively suppressed. As a result, the yaw rate decreased more than necessary, which could cause an understeer condition.

  Accordingly, an object of the present invention is to provide a vehicle behavior control device capable of appropriately adjusting a braking force for suppressing an oversteer state and suppressing occurrence of an understeer state during vehicle behavior control. And

  The present invention for solving the above-described problems is directed to a vehicle by applying a braking force with a set target braking force to a steering angular velocity acquisition unit that acquires a steering angular velocity, a lateral acceleration acquisition unit that acquires a lateral acceleration, and a turning outer wheel of the vehicle. Behavior stabilization control means for performing behavior stabilization control for stabilizing the behavior of the vehicle. The behavior stabilization control means includes a target braking force setting unit that sets the target braking force, and the lateral acceleration when the steering is suddenly performed. A lateral acceleration storage unit that stores the lateral acceleration storage unit, and the target braking force setting unit stores the lateral acceleration stored in the lateral acceleration storage unit when the lateral acceleration stored in the lateral acceleration storage unit exceeds a lateral acceleration threshold value. The larger the is, the smaller the upper limit of the target braking force is set.

  According to such a configuration, when the stored lateral acceleration exceeds the lateral acceleration threshold value, in other words, when the vehicle is suddenly steered during a turn in which a predetermined lateral acceleration is applied to the vehicle, the stored lateral acceleration is large. Since the upper limit of the target braking force is set smaller, it is possible to suppress the yaw rate from decreasing more than necessary. Thereby, it can suppress that an understeer state generate | occur | produces during vehicle behavior control.

  In the above-described apparatus, the target braking force setting unit may be configured to set the upper limit of the target braking force constant when the lateral acceleration stored in the lateral acceleration storage unit is equal to or less than the lateral acceleration threshold value. it can.

  According to such a configuration, it is possible to prevent the target braking force from being set to be smaller than necessary when the vehicle is suddenly steered during turning or straight traveling with a small lateral acceleration acting on the vehicle. The state can be effectively suppressed and the behavior of the vehicle can be further stabilized.

  According to the vehicle behavior control device of the present invention, it is possible to appropriately adjust the braking force for suppressing the oversteer state and to suppress the occurrence of the understeer state during the vehicle behavior control.

It is a lineblock diagram of vehicles provided with a vehicle behavior control device concerning one embodiment of the present invention. It is a block diagram which shows the structure of a hydraulic unit. It is a block diagram which shows the structure of a control part. It is a map which shows the relationship between steering angular velocity and offset amount. 6 is a timing chart showing changes in steering angle, steering angular velocity, and lateral acceleration. It is a map which shows the relationship between the deviation of the standard yaw rate and the limit yaw rate, and the target hydraulic pressure for setting the target hydraulic pressure. It is a map which shows the relationship between the lateral acceleration which the lateral acceleration memory | storage part memorize | stored and the hydraulic pressure upper limit for setting a hydraulic pressure upper limit. For setting the present target pressure PT _n at the end processing mode, a map showing the current relationship between the target fluid pressure PT _n preceding the target hydraulic pressure PT _n-1. It is a flowchart which shows the whole process of behavior stabilization control. It is a flowchart which shows the process of a target hydraulic pressure setting. It is a flowchart which shows the process of control end determination. It is a timing chart which shows change of vehicle speed, various yaw rates, and steering angular velocity for explaining operation of vehicle behavior control. 6 is a timing chart showing (a) changes in steering angle, actual yaw rate and slip angle, and (b) changes in brake fluid pressure of each wheel in a conventional vehicle behavior control device. 4 is a timing chart showing (a) changes in steering angle, actual yaw rate, and slip angle, and (b) changes in brake hydraulic pressure of each wheel in the vehicle behavior control device of the present embodiment. 5 is a timing chart showing (a) changes in steering angle, lateral acceleration, actual yaw rate, and slip angle, and (b) changes in brake hydraulic pressure of each wheel in a vehicle behavior control device of a comparative example. 4 is a timing chart showing (a) changes in steering angle, lateral acceleration, actual yaw rate, and slip angle, and (b) changes in brake hydraulic pressure of each wheel in the vehicle behavior control device of the present embodiment.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle behavior control device A according to an embodiment is a device that appropriately controls the braking force applied to each wheel W of the vehicle CR. The vehicle behavior control apparatus A mainly includes a hydraulic unit 10 provided with an oil passage and various components, and a control unit 100 for appropriately controlling various components in the hydraulic unit 10.

  Each wheel W is provided with a wheel brake FL, RR, RL, FR, and each wheel brake FL, RR, RL, FR is braked by a hydraulic pressure supplied from a master cylinder MC as a hydraulic pressure source. Is provided. Master cylinder MC and wheel cylinder H are each connected to hydraulic unit 10. Then, the brake fluid pressure generated in the master cylinder MC according to the depression force of the brake pedal BP (driver's braking operation) is supplied to the wheel cylinder H after being controlled by the control unit 100 and the fluid pressure unit 10.

  The control unit 100 includes a pressure sensor 91 that detects the pressure of the master cylinder MC, a wheel speed sensor 92 that detects the wheel speed of each wheel W, a steering angle sensor 93 that detects the steering angle θ of the steering ST, and a vehicle. A lateral acceleration sensor 94 that detects acceleration acting in the lateral direction of the CR (lateral acceleration AY) is connected. The control unit 100 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output circuit, and inputs from the sensors 91 to 94 and the ROM The control is executed by performing various arithmetic processes based on the programs and data stored in. Details of the control unit 100 will be described later.

  As shown in FIG. 2, the hydraulic unit 10 includes a master cylinder MC that is a hydraulic pressure source that generates a brake hydraulic pressure corresponding to a pedaling force applied by the driver to the brake pedal BP, and wheel brakes FR, FL, RR, RL. It is arranged between. The hydraulic unit 10 includes a pump body 10a which is a base body having an oil passage (hydraulic passage) through which brake fluid flows, a plurality of inlet valves 1, outlet valves 2 and the like arranged on the oil passage. The two output ports M1, M2 of the master cylinder MC are connected to the inlet port 121 of the pump body 10a, and the outlet port 122 of the pump body 10a is connected to each wheel brake FL, RR, RL, FR. In normal times, the oil passage is communicated from the inlet port 121 to the outlet port 122 in the pump body 10a, so that the depression force of the brake pedal BP is transmitted to the wheel brakes FL, RR, RL, FR. It is like that.

  Here, the oil path starting from the output port M1 leads to the wheel brake FL on the left side of the front wheel and the wheel brake RR on the right side of the rear wheel, and the oil path starting from the output port M2 is set to the wheel brake FR on the right side of the front wheel and the left side of the rear wheel. To the wheel brake RL. Hereinafter, the oil passage starting from the output port M1 is referred to as “first system”, and the oil passage starting from the output port M2 is referred to as “second system”.

  The hydraulic unit 10 is provided with two control valve means VL corresponding to each wheel brake FL, RR in the first system, and similarly corresponding to each wheel brake RL, FR in the second system. Two control valve means VL are provided. The hydraulic unit 10 is provided with a reservoir 3, a pump 4, an orifice 5a, a pressure regulating valve (regulator) R, and a suction valve 7 in each of the first system and the second system. The hydraulic unit 10 is provided with a common motor 9 for driving the first system pump 4 and the second system pump 4.

  In the following, the oil passages from the output ports M1 and M2 of the master cylinder MC to the respective pressure regulating valves R are referred to as “output hydraulic pressure passages A1”, and the oil from the first system pressure regulating valve R to the wheel brakes FL and RR. The oil passages from the road and the second system pressure regulating valve R to the wheel brakes RL and FR are respectively referred to as “wheel hydraulic pressure passage B”. In addition, an oil path from the output hydraulic pressure path A1 to the pump 4 is referred to as “suction hydraulic pressure path C”, an oil path from the pump 4 to the wheel hydraulic pressure path B is referred to as “discharge hydraulic pressure path D”, and The oil passage from the wheel fluid pressure passage B to the suction fluid pressure passage C is referred to as “open passage E”.

  The control valve means VL is a valve that controls the flow of hydraulic pressure from the master cylinder MC or the pump 4 side to the wheel brakes FL, RR, RL, FR side (specifically, the wheel cylinder H side). (Pressure in the wheel cylinder H) can be increased, held or decreased. Therefore, the control valve means VL includes an inlet valve 1, an outlet valve 2, and a check valve 1a.

  The inlet valve 1 is a normally open electromagnetic valve provided between each wheel brake FL, RR, RL, FR and the master cylinder MC, that is, in the wheel hydraulic pressure path B. The inlet valve 1 is normally opened to allow the brake hydraulic pressure to be transmitted from the master cylinder MC to the wheel brakes FL, FR, RL, RR. In addition, the inlet valve 1 is appropriately closed by the control unit 100 to cut off the brake hydraulic pressure transmitted from the brake pedal BP to each wheel brake FL, FR, RL, RR.

  The outlet valve 2 is a normally closed electromagnetic valve interposed between each wheel brake FL, RR, RL, FR and each reservoir 3, that is, between the wheel hydraulic pressure path B and the release path E. Although the outlet valve 2 is normally closed, the brake fluid pressure acting on each wheel brake FL, FR, RL, RR is released to each reservoir 3 by being appropriately opened by the control unit 100.

  The check valve 1a is connected to each inlet valve 1 in parallel. This check valve 1a is a valve that only allows the brake fluid to flow from each wheel brake FL, FR, RL, RR side to the master cylinder MC side, and when the input from the brake pedal BP is released, Even when the valve 1 is closed, inflow of brake fluid from each wheel brake FL, FR, RL, RR side to the master cylinder MC side is allowed.

  The reservoir 3 is provided in the release path E, and has a function of storing brake fluid pressure that is released when each outlet valve 2 is opened. Further, between the reservoir 3 and the pump 4, a check valve 3a that allows only the flow of brake fluid from the reservoir 3 side to the pump 4 side is interposed.

  The pump 4 is interposed between the suction hydraulic pressure path C leading to the output hydraulic pressure path A1 and the discharge hydraulic pressure path D leading to the wheel hydraulic pressure path B, and sucks the brake fluid stored in the reservoir 3 And has a function of discharging to the discharge hydraulic pressure path D.

  The orifice 5a attenuates the pulsation of the pressure of the brake fluid discharged from the pump 4 and the pulsation generated when the pressure regulating valve R described later operates.

  The pressure regulating valve R permits the flow of brake fluid from the output hydraulic pressure path A1 to the wheel hydraulic pressure path B during normal times, and increases the pressure on the wheel cylinder H side by the brake hydraulic pressure generated by the pump 4. It has a function of adjusting the pressure on the discharge hydraulic pressure path D, wheel hydraulic pressure path B and control valve means VL (wheel cylinder H) side to set values while blocking the flow, and includes a switching valve 6 and a check valve 6a. Configured.

  The switching valve 6 is a normally open type linear solenoid valve interposed between the output hydraulic pressure path A1 leading to the master cylinder MC and the wheel hydraulic pressure path B leading to each wheel brake FL, RR, RL, FR. .

  The check valve 6a is connected to each switching valve 6 in parallel. The check valve 6a is a one-way valve that allows the flow of brake fluid from the output hydraulic pressure path A1 to the wheel hydraulic pressure path B.

  The suction valve 7 is a normally closed electromagnetic valve provided in the suction fluid pressure passage C, and switches between a state in which the suction fluid pressure passage C is opened and a state in which the suction fluid pressure passage C is shut off.

  The pressure sensor 91 detects the brake hydraulic pressure in the output hydraulic pressure path A1, and the detection result is input to the control unit 100.

Next, details of the control unit 100 will be described.
The control unit 100 is a device that performs control to stabilize the behavior of the vehicle CR by controlling the hydraulic unit 10 and applying a braking force with a target braking force set to the turning outer wheel of the vehicle CR. For this reason, as shown in FIG. 3, the control unit 100 includes a steering angle acquisition unit 110, a lateral acceleration acquisition unit 111, a vehicle speed calculation unit 120, a steering angular velocity calculation unit 130, a standard yaw rate calculation unit 140, and a limit yaw rate setting unit 150. The behavior stabilization control means 160 and the storage means 190 are provided. Note that the output of the pressure sensor 91 is not shown in FIG. 3 because it is not necessary for the characteristic configuration of the vehicle behavior control apparatus A of the present invention. Further, in the following description, for each variable such as the steering angle θ, the steering angular velocity ω, and the lateral acceleration AY, the value at the left turn is positive and the value at the right turn is negative.

  The steering angle acquisition unit 110 is a unit that acquires information on the steering angle θ from the steering angle sensor 93 for each control cycle. The steering angle θ is output to the steering angular velocity calculation means 130 and the normative yaw rate calculation means 140.

  The lateral acceleration acquisition unit 111 is a unit that acquires information on the lateral acceleration AY from the lateral acceleration sensor 94 for each control cycle. The lateral acceleration AY is output to the behavior stabilization control means 160.

  The vehicle speed calculation means 120 is means for acquiring wheel speed information (pulse signal of the wheel speed sensor 92) from the wheel speed sensor 92 for each control cycle, and calculating the wheel speed and the vehicle speed V by a known method. . The calculated vehicle speed V is output to the normative yaw rate calculating means 140 and the limit yaw rate setting means 150.

The steering angular velocity calculation unit 130 is an example of a steering angular velocity acquisition unit, and is a unit that calculates the steering angular velocity ω from the steering angle θ. The steering angular velocity ω can be obtained by differentiating the steering angle θ or calculating the difference between the previous steering angle θ _n−1 and the current steering angle θ _n . The calculated steering angular velocity ω is output to the behavior stabilization control means 160. In the present specification, the subscript n attached after the variable indicates that the variable is the current value, and n−1 indicates the previous value.

  The reference yaw rate calculation means 140 is a means for calculating a reference yaw rate YS as a yaw rate intended by the driver based on the steering angle θ and the vehicle speed V by a known method. The calculated reference yaw rate YS is output to the behavior stabilization control means 160.

  The limit yaw rate setting means 150 is a means for setting a limit yaw rate YL that is a limit yaw rate at which the vehicle can stably travel based on the vehicle speed V. The limit yaw rate YL is set to a smaller value as the vehicle speed V increases. In this embodiment, the calculation is performed on the assumption that the road surface state is a dry road surface. However, when the control unit 100 holds a reliable estimated road surface friction coefficient, the estimated yaw rate is calculated using the estimated road surface friction coefficient. YL may be calculated. The calculated limit yaw rate YL is output to the behavior stabilization control means 160.

  The behavior stabilization control means 160 is a means for executing behavior stabilization control that stabilizes the behavior of the vehicle CR by applying a braking force to the turning outer wheel of the vehicle CR with a set target braking force. In this embodiment, the target hydraulic pressure PT is set as a value corresponding to the target braking force, and the hydraulic pressure is set so that the wheel cylinder pressures of the wheel brakes FL, RR, RL, FR of the turning outer wheel become the target hydraulic pressure PT. The unit 10 is controlled. For this control, the behavior stabilization control unit 160 includes a control intervention threshold setting unit 163, a control intervention determination unit 164, a control end determination unit 165, a sudden steering determination unit 166, a lateral acceleration storage unit 167, and a target braking force setting unit. As an example, a target hydraulic pressure setting unit 168 and a control execution unit 169 are included.

  The control intervention threshold setting unit 163 is a means for setting the control intervention threshold YSth based on the limit yaw rate YL and the steering angular velocity ω. Specifically, the control intervention threshold YSth is calculated by adding the offset amount YD depending on the absolute value of the steering angular velocity ω to the limit yaw rate YL (adding to the negative side for right turn). As shown in FIG. 4, the offset amount YD is a constant value YD1 when the absolute value of the steering angular velocity ω is from 0 to a predetermined value ω1, and is between the predetermined value ω1 and the predetermined value ω2. As the absolute value of ω increases, the absolute value decreases, and in a range larger than the predetermined value ω2, the constant value YD2 is smaller than YD1. For this reason, the absolute value of the control intervention threshold YSth is set smaller as the absolute value of the steering angular velocity ω is larger. As shown in the graph of changes in various yaw rates shown in FIG. 12, the control intervention threshold YSth is calculated as two values for right turn and left turn. The control intervention threshold setting unit 163 outputs the calculated control intervention threshold YSth to the control intervention determination unit 164.

  The control intervention determination unit 164 is a unit that determines that behavior stabilization control is started when the absolute value of the reference yaw rate YS exceeds the absolute value of the control intervention threshold YSth set by the control intervention threshold setting unit 163. When the standard yaw rate YS is positive, it is compared with the control intervention threshold YSth for turning left, and when it is negative, it is compared with the control intervention threshold YSth for turning right.

  When the control intervention determination unit 164 determines to start the behavior stabilization control, the control mode M changes the control mode M from non-controlling (M = 0) to controlling (M = 1). Since the control intervention threshold YSth is set based on the steering angular velocity ω, the control intervention determination unit 164 determines the start of behavior stabilization control based on the steering angular velocity ω.

  The control end determination unit 165 is means for determining the end of the behavior stabilization control. Specifically, the end of the behavior stabilization control is determined when the absolute value of the reference yaw rate YS is smaller than the absolute value of the limit yaw rate YL as the control end threshold. When the control end determination unit 165 determines the end of the behavior stabilization control, the control mode M is set to the end process (M = 2).

  The sudden steering determination unit 166 is means for determining whether or not the steering ST is steered. Specifically, as shown in FIG. 5, the sudden steering determination unit 166 monitors the change in the steering angular velocity ω, and when the lateral acceleration AY is not stored (K = 0), the steering angular velocity ω When the absolute value exceeds the absolute value of the determination threshold value ωth, it is determined that sudden steering has been performed. The determination threshold value ωth can be set as appropriate according to the weight of the vehicle CR and the like, for example, ωth = 400 deg / s. When the sudden steering determination unit 166 determines that sudden steering has been performed, the sudden steering determination unit 166 outputs information to that effect to the lateral acceleration storage unit 167.

  The lateral acceleration storage unit 167 is means for storing the lateral acceleration AY when sudden steering is performed. Specifically, when the sudden steering determination unit 166 determines that the sudden steering is performed, the lateral acceleration storage unit 167 stores the lateral acceleration AY at that time, that is, the currently acquired lateral acceleration AY in the storage unit 190 as an example. The storage flag is set to a state in which the lateral acceleration AY is stored (K = 1). Here, the lateral acceleration AY to be stored may be, for example, a lateral acceleration at a point in time slightly before the point at which it is determined that sudden steering is performed, or an average of a plurality of lateral accelerations slightly before the point in time of determination. It may be a value.

  As shown in FIG. 5, even when sudden steering is performed, the lateral acceleration AY does not change immediately. Therefore, when it is determined that sudden steering is performed (when the steering angular velocity ω exceeds the determination threshold ωth). The lateral acceleration AY is substantially the same as the lateral acceleration AY slightly before that, and can be treated as meaning the traveling state of the vehicle CR before sudden steering is performed. In order to make the stored lateral acceleration AY mean the running state before the sudden steering, the determination threshold ωth is small enough to exceed the steering angular velocity ω before the lateral acceleration AY largely fluctuates. Set as a value.

  The target hydraulic pressure setting unit 168 is means for setting the target hydraulic pressure PT according to whether the control mode M is under control or is in the end process. First, the case during control will be described. During the control, the target hydraulic pressure setting unit 168 sets the target hydraulic pressure PT based on the reference yaw rate YS, the limit yaw rate YL, and the lateral acceleration AY stored in the lateral acceleration storage unit 167.

In principle, the target hydraulic pressure setting unit 168 sets the target hydraulic pressure PT to a larger value as the deviation ΔY is larger, based on the standard yaw rate YS and the deviation ΔY between the limit yaw rate YL. Here, ΔY is the value of | YS−YL | as it is when the absolute value | YS−YL | of the difference between the reference yaw rate YS and the limit yaw rate YL increases, and the previous value when it decreases. Calculate to hold. That is, ΔY changes so as to maintain the peak value after | YS−YL | FIG. 6 is a map for setting this basic target hydraulic pressure PT. The larger the deviation ΔY is, the higher the target hydraulic pressure PT is determined. More specifically, the target hydraulic pressure PT gradually increases from 0 to a predetermined value d1, and when the deviation ΔY is equal to or greater than the predetermined value d1, the target hydraulic pressure PT is set to a certain upper limit value PTm. Yes.
Here, since the deviation ΔY reflects the disturbance of the behavior of the vehicle CR, the target hydraulic pressure PT is set according to the magnitude of the deviation ΔY, so that the deviation of the behavior of the vehicle CR is predicted. Since the corresponding braking force can be applied to the turning outer wheel, disturbance of the behavior of the vehicle CR can be reduced.

  The target hydraulic pressure setting unit 168 stores the lateral acceleration stored in the lateral acceleration storage unit 167 in order to suppress the occurrence of understeer caused by applying an excessive braking force to the turning outer wheel with respect to the target hydraulic pressure PT obtained as a principle value. A hydraulic pressure upper limit value PTL is set according to AY, and the smaller one of the target hydraulic pressure PT obtained as a principle value and the hydraulic pressure upper limit value PTL is set as a new target hydraulic pressure PT.

  In the present embodiment, the hydraulic pressure upper limit value PTL is set based on the map of FIG. Specifically, the target hydraulic pressure setting unit 168 stores the lateral acceleration storage unit 167 when the absolute value of the lateral acceleration AY stored in the lateral acceleration storage unit 167 exceeds the first threshold value AY1 as the lateral acceleration threshold value. The larger the absolute value | AY | of the lateral acceleration AY, the smaller the hydraulic pressure upper limit value PTL is set. When the absolute value | AY | of the lateral acceleration AY stored in the lateral acceleration storage unit 167 exceeds the second threshold value AY2 larger than the first threshold value AY1, the hydraulic pressure upper limit value PTL is set to a constant value PTL2. When the absolute value | AY | of the lateral acceleration AY stored in the lateral acceleration storage unit 167 is equal to or less than the first threshold value AY1, the hydraulic pressure upper limit value PTL is set to a constant value PTL1 (PTL1> PTL2).

  When | AY | exceeds the first threshold value AY1, the lateral acceleration that has been applied at the time of sudden steering is somewhat large, so that the steering ST is suddenly steered when the vehicle CR is turning. be able to. At this time, if a large braking force is applied to the turning outer wheel of the vehicle CR in the subsequent behavior stabilization control, an understeer state may be caused. Therefore, by increasing the hydraulic pressure upper limit value PTL as | AY | The hydraulic pressure upper limit value PTL tends to be smaller than the target hydraulic pressure PT obtained from the map of FIG. Thus, when the smaller one of the target hydraulic pressure PT obtained from the map of FIG. 6 and the hydraulic pressure upper limit value PTL is selected, the new target hydraulic pressure PT can be reduced. Braking force applied to the vehicle can be suppressed. In addition, when | AY | exceeds the second threshold value AY2, the hydraulic pressure upper limit value PTL is set to the constant value PTL2, thereby suppressing the new target hydraulic pressure PT from becoming smaller than necessary.

  On the other hand, when | AY | is equal to or less than the first threshold value AY1, the lateral acceleration that was applied before the sudden steering is small, and therefore the steering ST is steered rapidly when the vehicle CR is traveling substantially straight. It can be said that. At this time, since an understeer state is unlikely to occur, by setting the hydraulic pressure upper limit value PTL (PTL1) to be larger than when | AY | exceeds the first threshold value AY1, the new target hydraulic pressure PT becomes | AY | Is more likely to be set than when it exceeds the first threshold AY1. The hydraulic pressure upper limit PTL1 is equal to or higher than the target hydraulic pressure PTm and does not affect the target hydraulic pressure PT obtained from the map of FIG.

Next, the setting of the target hydraulic pressure PT when the end process is being performed will be described. During termination processing, the target fluid pressure setting unit 168, based on the target hydraulic pressure PT _n-1 of the previous sets a current target hydraulic pressure PT _n based on the map of FIG. Map of FIG. 8, although the present target pressure PT _n the larger the target hydraulic pressure PT _n-1 of the previous large, the target hydraulic pressure PT _n of this time, a little than the target hydraulic pressure PT _n-1 of the previous It is set to a small value. When the previous target hydraulic pressure PT _n−1 is smaller than a predetermined value, the current target hydraulic pressure PT _n is set to be zero. If the current target hydraulic pressure PT _n is 0, the target hydraulic pressure setting section 168 changes the control mode M to the non-control in (M = 0). When the control mode M is changed to non-control, the lateral acceleration storage unit 167 resets the lateral acceleration AY stored in the storage unit 190, and the storage flag does not store the lateral acceleration AY (K = 0). ).

  The control execution unit 169 is means for controlling the hydraulic pressure unit 10 based on the target hydraulic pressure PT set by the target hydraulic pressure setting unit 168 to control the wheel cylinder pressure of the turning outer wheel to the target hydraulic pressure PT. This control is well known and will not be described in detail. However, in brief, the pump 9 is driven by operating the motor 9, the suction valve 7 is opened, and an appropriate current is supplied to the pressure regulating valve R. Control to flow.

  The storage unit 190 is a unit that appropriately stores constants, parameters, control modes, maps, calculation results, and the like necessary for the operation of the control unit 100.

The process by the control part 100 of the vehicle behavior control apparatus A comprised as mentioned above is demonstrated with reference to FIG. Note that the process of FIG. 9 is repeated for each control cycle. The initial value of the control mode M is 0.
First, the steering angle acquisition unit 110 acquires the steering angle θ from the steering angle sensor 93, the lateral acceleration acquisition unit 111 acquires the lateral acceleration AY from the lateral acceleration sensor 94, and the vehicle speed calculation unit 120 includes a wheel speed sensor. The wheel speed is acquired from 92 (S101). Then, the steering angular speed calculation means 130 calculates the steering angular speed ω from the steering angle θ, and the vehicle speed calculation means 120 calculates the vehicle speed V from the wheel speed (S102). Next, the normative yaw rate calculating means 140 calculates the normative yaw rate YS based on the steering angle θ and the vehicle speed V (S110). Further, the limit yaw rate setting means 150 sets the limit yaw rate YL based on the vehicle speed V (S111).

  Next, the control intervention threshold setting unit 163 sets the control intervention threshold YSth based on the limit yaw rate YL and the steering angular velocity ω (S112). At this time, as described above, the control intervention threshold YSth is set by adding the offset amount YD, which decreases as the absolute value of the steering angular velocity ω increases, as shown in FIG. 4, to the limit yaw rate YL. The threshold YSth decreases as the absolute value of the steering angular velocity ω increases.

  Then, the control intervention determination unit 164 determines whether or not the absolute value of the reference yaw rate YS is larger than the absolute value of the corresponding control intervention threshold YSth for right turn or left turn. When the absolute value of the reference yaw rate YS is larger than the absolute value of the control intervention threshold YSth (S120, Yes), the control intervention determination unit 164 determines the start of control and sets the control mode M to 1 (S121). If the absolute value of the reference yaw rate YS is not greater than the absolute value of the control intervention threshold YSth (S120, No), the control intervention determination unit 164 proceeds to step S130 without changing the control mode M.

  Then, the behavior stabilization control means 160 determines whether or not the control mode M is 0, that is, whether or not the control mode M is not in control. If the control mode M is not 0 (S130, No: M = 1 or 2), Steps S200 to S300 are performed.

In step S200, the behavior stabilization control means 160 sets the target hydraulic pressure PT. As shown in FIG. 10, the target hydraulic pressure setting unit 168 determines whether or not the control mode M is 1, and when it is not 1, that is, when the control mode M is 2 and the end process is being performed (S210, No) ), based on the map of FIG. 8, on the basis of the target hydraulic pressure _{PT n-1} previous to determine the current target hydraulic pressure PT _n (S220). Then, when the present target pressure PT _n is 0 (S221, Yes), the control mode M to 0 means that termination process has been completed (S222). On the other hand, if the present target pressure PT _n is not 0 (S221, No), the process ends without changing the control mode M.

  If the control mode M is 1 in the determination in step S210 (S210, Yes), the behavior stabilization control means 160 determines whether or not the storage flag K is 0 (S231). When the storage flag K is 0 (S231, Yes), that is, when the lateral acceleration AY is not stored, the sudden steering determination unit 166 determines whether the absolute value of the steering angular velocity ω exceeds the absolute value of the determination threshold ωth. It is determined whether or not (S232), and whether or not the sudden steering is being performed.

  When sudden steering is being performed (S232, Yes), the lateral acceleration storage unit 167 stores the lateral acceleration AY (S233), sets the storage flag K to 1 (S234), and proceeds to step S241. Further, when the storage flag K is not 0 in Step S231 (when the lateral acceleration AY is stored) (S231, No), or in Step S232, the absolute value of the steering angular velocity ω does not exceed the absolute value of the determination threshold value ωth. In the case (S232, No), it progresses to step S241.

  In step S241, the target hydraulic pressure setting unit 168 sets the target hydraulic pressure PT from the map of FIG. 6 based on the deviation ΔY. Further, the target hydraulic pressure setting unit 168 sets the hydraulic pressure upper limit value PTL from the map of FIG. 7 based on | AY | (stored lateral acceleration) (S242). Then, the target hydraulic pressure setting unit 168 sets the smaller one of the target hydraulic pressure PT set in step S241 and the hydraulic pressure upper limit value PTL set in step S242 as a new target hydraulic pressure PT (S243). ).

  When the target hydraulic pressure PT is set in this way, returning to FIG. 9, the control execution unit 169 switches the hydraulic pressure unit 10 so that the hydraulic pressure in the wheel cylinder H of the turning outer wheel becomes the target hydraulic pressure PT. Control is performed (S131).

  Next, the control end determination unit 165 performs control end determination in step S300. Specifically, as shown in FIG. 11, it is determined whether or not the absolute value of the normative yaw rate YS is smaller than the absolute values of the corresponding left and right limit yaw rates YL. If the absolute value is smaller (S310, Yes), the behavior is stable. It is determined that the control is to be ended, and the control mode M is changed to 2 which is in the end process (S311). On the other hand, when the absolute value of the normative yaw rate YS is not smaller than the absolute values of the corresponding left and right limit yaw rates YL (S310, No), the process ends without changing the control mode M.

  In step S130 of FIG. 9, when the control mode M is 0 (S130, Yes), the behavior stabilization control means 160 resets the stored lateral acceleration AY (S132) and sets the storage flag K to 0 (S133). The process is terminated.

  Changes in various parameters by the above control will be described with reference to FIG. Although the steering angle θ is not shown in FIG. 12, the steering angle θ changes with substantially the same phase as the reference yaw rate YS. In the following description, the value of each parameter is discussed with respect to the magnitude, and “absolute value” is omitted, and each parameter is expressed in the same way as a positive value during right turn.

  As shown in the change in the standard yaw rate YS in FIG. 12, the vehicle CR turns the steering ST to the left between times t11 and t15, and turns the steering ST to the right between times t15 and t18. Since the limit yaw rate YL decreases as the vehicle speed V increases, the limit yaw rate YL gradually increases as the vehicle speed V gradually decreases after time t11. Here, when the steering angular velocity ω increases after time t11, the left turn control intervention threshold YSth decreases rapidly. For this reason, at time t12 before starting to turn right, the reference yaw rate YS exceeds the control intervention threshold YSth for turning left, and the control mode M is changed from 0 to 1. And from time t12 to t13, the control intervention threshold YSth increases as the steering angular velocity ω decreases. When the reference yaw rate YS facing left decreases and at time t14, the reference yaw rate YS becomes smaller than the limit yaw rate YL as the control end threshold, and the control mode M becomes 2. Then, when the termination process is finished, the control mode M becomes zero.

  When the steering ST is turned back to the right after time t13, the steering angular velocity ω increases to the right, so that the control intervention threshold YSth for right turn decreases, and at time t16, the reference yaw rate YS is used for right turn. When the control intervention threshold value YSth is exceeded, the control mode M changes from 0 to 1. Then, the normal yaw rate YS facing right decreases, and at time t17, the standard yaw rate YS becomes smaller than the limit yaw rate YL and the control mode M becomes 2. Then, when the termination process is finished, the control mode M becomes zero.

The effect of the vehicle behavior control apparatus A as described above will be described with reference to FIGS.
FIG. 13 and FIG. 14 show changes in parameters when the vehicle returns straight from the straight traveling state to the left, right, or left. FIG. 13 shows a case where the control start determination in the prior art is used. In the determination of the start, as in JP 2011-102048, it is determined that the control is started when the deviation between the corrected normative yaw rate set based on the lateral acceleration and the actual yaw rate exceeds a threshold value. . The threshold value is not changed according to the steering angular velocity.

  In the prior art, as shown in FIG. 13 (a), the start of control is determined at time t21 after the steering angle θ reaches a peak due to turning the steering to the left, that is, after starting to turn back to the right. Has been. As shown in FIG. 13B, the brake fluid pressure is not generated sufficiently during the left turn that is the first steering, but is generated only at a sufficient level during the right turn that is the second steering. doing. Therefore, as shown in FIG. 13A, at the time t25, the actual yaw rate is decreased, and the difference between the steering angle and the actual yaw rate is increased, resulting in an understeer tendency. At time t24, the slip angle β (the deviation angle between the traveling direction of the vehicle and the steering direction) indicating the state of disturbance of the vehicle behavior is largely fluctuated, and the behavior of the vehicle is disturbed.

  On the other hand, in the vehicle behavior control apparatus A of the present embodiment, as shown in FIG. 14A, the control is started at time t31 before the steering angle θ reaches the peak, that is, at the first turning of the steering ST. Has been determined. Then, as shown in FIG. 14B, a sufficiently large brake fluid pressure is generated during the left turn which is the first steering. For this reason, the disturbance of the behavior of the vehicle is suppressed, and as shown in FIG. 14A, the slip angle β is kept small at the time t35 during turning to the right.

  FIG. 15 and FIG. 16 show changes in parameters when the vehicle returns to a straight traveling state after being steered further to the right from the right turning state. FIG. 15 shows a comparative example in which the target hydraulic pressure PT is set based only on the map of FIG. 6 without setting the hydraulic pressure upper limit value PTL, and FIG. 16 shows the embodiment. This is the case.

  In the comparative example, as shown in FIG. 15 (a), when behavior stabilization control is started at time t41 after the steering is further turned to the right from the right turn state, as shown in FIG. 15 (b). A large brake fluid pressure is generated. For this reason, in the comparative example, the braking force becomes excessive while the steering is being returned to the left, and as shown in FIG. 15 (a), the actual yaw rate decreases and an understeering tendency occurs at time t42. Yes. In addition, the variation of the slip angle β is relatively steep.

  On the other hand, in the present embodiment, as shown in FIG. 16A, when behavior stabilization control is started at time t51 after turning the steering ST further to the right from the right turn state, FIG. As shown in FIG. 5, a smaller brake fluid pressure is generated than in the comparative example. This is the minimum value of the hydraulic pressure upper limit value PTL and the target hydraulic pressure PT obtained from the map of FIG. 6 by setting the hydraulic pressure upper limit value PTL smaller as | AY | is larger in the map of FIG. This is because the new target hydraulic pressure PT is reduced. Therefore, in the present embodiment, as the brake fluid pressure decreases, as shown in FIG. 16A, the decrease in the actual yaw rate during the return of the steering ST to the left can be suppressed, and an understeer tendency occurs. It is suppressed. Further, the variation of the slip angle β is gentle.

  As described above, according to the vehicle behavior control apparatus A of the present embodiment, the larger the absolute value of the stored lateral acceleration AY is, the larger the stored lateral acceleration AY is when the vehicle CR is steered during a turn in which a relatively large lateral acceleration AY acts. Since the hydraulic pressure upper limit value PTL is set small, the target hydraulic pressure PT can be reduced, and the actual yaw rate can be suppressed from decreasing more than necessary. Thereby, it can suppress that an understeer state generate | occur | produces during vehicle behavior control.

  Further, when the stored absolute value of the lateral acceleration AY is equal to or less than the first threshold value AY1, the hydraulic pressure upper limit value PTL is set to a constant value PTL1, so that the lateral acceleration AY acting on the vehicle CR is small during turning or straight traveling When the vehicle is steered suddenly, the target hydraulic pressure PT can be prevented from being set smaller than necessary. As a result, it is possible to effectively suppress the oversteer state when the vehicle is suddenly steered during straight traveling or the like, and to stabilize the behavior of the vehicle CR.

  Further, since the vehicle behavior control device A can determine the start of the behavior stabilization control based on the steering angle θ, the steering angular velocity ω, and the vehicle speed V without being based on the actual yaw rate, the result of steering of the steering ST is It can be determined that the behavior stabilization control is started before the actual behavior of the vehicle CR appears. Therefore, behavior stabilization control can be started at an early stage, and disturbance in behavior of the vehicle CR can be suppressed.

  The vehicle behavior control apparatus A can start the behavior stabilization control at an initial stage where the steering ST is cut from the straight traveling state because the control intervention threshold YSth decreases as the absolute value of the steering angular velocity ω increases.

  Further, since the vehicle behavior control apparatus A increases the target hydraulic pressure PT as the deviation ΔY between the reference yaw rate YS and the limit yaw rate YL increases, the braking force according to the predicted disturbance in the behavior of the vehicle CR. Can be given to the turning outer wheel, so that the disturbance of the behavior of the vehicle CR can be reduced.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be implemented in various forms as exemplified below.

  In the embodiment, the stored lateral acceleration AY is reset when the control mode M is 0. For example, the control mode M is 0 and the steering angular velocity | ω | is equal to or less than the determination threshold value | ωth |. In this case, the stored lateral acceleration AY may be reset.

  In the above-described embodiment, the steering angular velocity calculation unit 130 that calculates and acquires the steering angular velocity ω from the steering angle θ is exemplified as the steering angular velocity acquisition unit. However, the steering angular velocity may be acquired from a sensor.

  In the embodiment, the lateral acceleration storage unit 167 is configured to store the lateral acceleration AY when the sudden steering determination unit 166 determines that the sudden steering is performed. However, the lateral acceleration storage unit 167 is not limited to this. Absent. For example, the lateral acceleration storage unit 167 stores the lateral acceleration AY when the control intervention determination unit 164 determines to start the behavior stabilization control based on the control intervention threshold YSth set by the control intervention threshold setting unit 163. It may be configured. That is, when it is determined that the behavior stabilization control is started, it can be said that the sudden steering is performed. Therefore, in the above embodiment, the control intervention threshold setting unit 163 and the control intervention determination unit are not provided without the rapid steering determination unit 166. 164 may be used as a means for determining sudden steering.

  In the embodiment, the target hydraulic pressure is set as an example of the target braking force, but the target braking force itself may be set as the target value.

  In the above embodiment, the target hydraulic pressure PT is set without distinguishing the front wheel and the rear wheel among the turning outer wheels, but the size of the target hydraulic pressure PT is set for each wheel according to the weight distribution of the front and rear wheels. You may adjust.

  In the embodiment described above, only the case where the vehicle behavior stabilization control is executed has been described. However, the vehicle behavior control device A may be configured to perform antilock brake control and the like together.

  In the above-described embodiment, the present invention is applied to the brake system configured such that the hydraulic pressure of the master cylinder MC is transmitted to the wheel cylinder H. However, the vehicle behavior control device of the present invention pressurizes the brake fluid with an electric motor, The present invention can also be applied to a so-called by-wire type brake device.

DESCRIPTION OF SYMBOLS 10 Hydraulic unit 100 Control part 110 Steering angle acquisition means 111 Lateral acceleration acquisition means 120 Vehicle speed calculation means 130 Steering angular velocity calculation means 140 Standard yaw rate calculation means 150 Limit yaw rate setting means 160 Behavior stability control means 163 Control intervention threshold setting part 164 Control Intervention determination unit 165 Control end determination unit 166 Rapid steering determination unit 167 Lateral acceleration storage unit 168 Target hydraulic pressure setting unit A Vehicle behavior control device

Claims (2)

Steering angular velocity acquisition means for acquiring the steering angular velocity;
Lateral acceleration acquisition means for acquiring lateral acceleration;
A behavior stabilization control means for performing behavior stabilization control for stabilizing the behavior of the vehicle by applying a braking force to the turning outer wheel of the vehicle with a set target braking force;
The behavior stabilization control means includes
A target braking force setting unit for setting the target braking force;
A lateral acceleration storage unit that stores the lateral acceleration when sudden steering is performed;
When the lateral acceleration stored in the lateral acceleration storage unit exceeds a lateral acceleration threshold, the target braking force setting unit sets the upper limit of the target braking force to be smaller as the lateral acceleration stored in the lateral acceleration storage unit is larger. A vehicle behavior control device.   The target braking force setting unit sets an upper limit of the target braking force to be constant when the lateral acceleration stored in the lateral acceleration storage unit is equal to or less than the lateral acceleration threshold value. Vehicle behavior control device.

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