JP5314445B2 - Vehicle motion control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle motion control system capable of shifting to a smooth turning motion, when becoming an understeer state or an oversteer state in the turning motion of a vehicle. <P>SOLUTION: A VSA control part, as the control function part of a brake fluid pressure control device for a vehicle, determines whether the turning state of the vehicle is an understeer state, or whether the turning state of the vehicle is an oversteer state. When determining that the turning state of the vehicle is the understeer state, the VSA control part applies a braking force to wheels inside turning, and a rear wheel toe angle control part sets rear wheels outside turning to toe-in in response to the determination of the VSA control part. When determining that the turning state is the oversteer state, the VSA control part applies the braking force to wheels outside turning, and the rear wheel toe angle control part sets the rear wheels inside turning to toe-in in response to the determination of the VSA control part. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a vehicle motion control system, and more particularly, a braking force control means for stabilizing a vehicle by controlling a braking force difference between left and right wheels, and a rear wheel toe angle capable of individually changing left and right rear wheel toe angles. The present invention relates to a vehicle motion control system provided with a control means.

Conventionally, the traction control system (abbreviated as TCS) function for controlling idling of drive wheels using the vehicle brake hydraulic pressure control device described in Patent Document 1, and the understeer state and oversteer state are detected during turning. Vehicle stability assist system that includes a function to stabilize the vehicle behavior by increasing the braking force of the wheel on the inside of the turn or the wheel on the outside of the turn to give the yaw moment to correct the understeer state or oversteer state ( (Abbreviated as VSA) is disclosed (Patent Document 2).
Incidentally, the VSA includes a known ABS (Antilock Brake System) function. The VSA corresponds to “braking force control means” in the present invention.

  Further, in Patent Document 3, the rear wheel toe angle is individually changed and controlled according to the operation angle of the steering wheel or the accelerator pedal or the brake pedal, thereby improving the turning performance of the vehicle. A technology of a vehicle rear wheel toe angle control device (corresponding to the “rear wheel toe angle control means” in the present invention) that enhances or enhances vehicle running stability is disclosed.

JP 2007-030745 A JP 2007-118676 A JP 2008-055921 A

However, the braking force control by the VSA during the turning motion of the vehicle by the technology disclosed in the conventional patent document 2 and the rear wheel toe angle control by the rear wheel toe angle control device by the technology disclosed in the conventional patent document 3 are merely simple. In the combination, for example, when the understeer state is determined, as shown in FIG. 6 (a), braking forces FVSA1 and FSSA2 are applied to the wheels 3FL and 3RL on the inside of the turn to generate the yaw moment MVSA in the turning direction. By doing so, it is possible to increase the yaw rate in the turning direction so as to change the vehicle body direction inwardly. However, the toe angles of the rear wheels (rear wheels) 3RL, 3RR are the turning directions in which the wheels 3FL, 3FR, which are steered wheels, are directed so as to promote turning by the rear wheel toe angle control device in the prior art. As shown in FIG. 6A with respect to the inward direction, the phase is set to the opposite phase or the toe angle is set to zero .
In such a control, the yaw rate of the vehicle is stably controlled, but the trajectory of the rear part of the vehicle swells to the outside of the turn and does not make a smooth transition from the understeer state to the neutral state turning motion.

The same can be said for the oversteer state. As shown in FIG. 7A, the braking forces FVSA1, FSSA2 are applied to the wheels 3FR, 3RR on the outside of the turn, and the yaw moment MVSA in the direction opposite to the turn direction. By generating the above, the yaw rate in the turning direction can be suppressed so as to change the vehicle body direction to turn outward. However, the toe angles of the rear wheels (rear wheels) 3RL, 3RR are the turning directions in which the wheels 3FL, 3FR, which are steered wheels, are directed so as to promote turning by the rear wheel toe angle control device in the prior art. As shown in FIG. 7A with respect to the inward direction, the phase is set to the opposite phase or the toe angle is set to zero .
In such a control, the yaw rate of the vehicle is stably controlled, but the trajectory of the rear part of the vehicle has a weak bulge to the outside of the turn and does not make a smooth transition from the oversteer state to the neutral state turning motion. It was.

  The present invention solves the above-described conventional problems, and in a vehicle motion control system including a braking force control means and a rear wheel toe angle control means, the vehicle is in an understeer state or an oversteer state during a turning motion of the vehicle. It is an object of the present invention to provide a vehicle motion control system that can smoothly transition to a turning motion in a neutral state.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a braking force control unit that performs control to apply different braking forces to the left and right wheels of the vehicle so as to generate a yaw moment in the vehicle, A vehicle motion control system comprising at least a rear wheel toe angle control means for controlling a toe angle of a rear wheel in accordance with an operation angle of a steering wheel that changes the direction of a front wheel that is a steered wheel, wherein the vehicle turns state with understeer state determining means for determining whether understeer state, when the turning state of the vehicle in the understeer state determining means determines that an understeer state, said braking force control means, the front and rear wheels of the turning inner one that performs control for applying a braking force, the rear wheel toe angle control means, toe-side rear wheels different turning outside the turning inner wheel the braking force is applied And performing toe angle control to direct.

According to the first aspect of the present invention, when the understeer state determination means determines that the understeer state, the braking force control means performs control to apply the braking force to the front and rear wheels inside the turn, while the rear wheel toe angle control means, the braking force makes a toe angle control for directing the rear wheel of different pivot outwardly toe side of the turning inner wheel is applied, not only the vehicle comes to cut into more pivot inwardly, conventional can rear part of the trajectory is inhibited from swell tends to pivot outward, to shift the behavior of the vehicle to smooth neutral pivoting motion state.
In addition, because the toe angle control is performed so that the rear wheels on the outer side of the turn different from the wheels on the inner side of the turn to which the braking force is applied are directed to the toe-in side, the friction circles related to the front and rear wheels on the inner side of the turn are affected during the turning motion. And stable control of the turning motion can be realized.

According to a second aspect of the present invention, there is provided braking force control means for performing control for applying different braking forces to the left and right wheels of the vehicle so as to generate a yaw moment in the vehicle, and front wheels that are steered wheels of the vehicle. And a rear wheel toe angle control means for performing rear wheel toe angle control in accordance with an operation angle of a steering handle for changing the direction, wherein the turning state of the vehicle is in an oversteer state or not. Oversteer state determination means for determining whether or not the oversteer state determination means determines that the turning state of the vehicle is an oversteer state, the braking force control means applies braking force to the front and rear wheels outside the turn. On the other hand, the rear wheel toe angle control means performs toe angle control in which the rear wheel inside the turn different from the wheel outside the turn to which the braking force is applied is directed toward the toe in side. Cormorant be characterized.
According to the second aspect of the present invention, when the oversteer state determination unit determines that the oversteer state is present, the braking force control unit performs control to apply the braking force to the front and rear wheels outside the turn, while the rear wheel toe The angle control means performs toe angle control in which the rear wheels on the inside of the turn different from the wheels on the outside of the turn to which the braking force is applied are directed to the toe-in side. By correcting that the trajectory of the rear part of the vehicle body is less likely to bulge outward, it is possible to shift the behavior of the vehicle to a smooth neutral turning motion state.
Also, because the toe angle control is performed so that the rear wheels on the inside of the turn, which are different from the wheels on the outside of the turn to which the braking force is applied, are directed to the toe-in side, the friction circles on the front and rear wheels on the outside of the turn are affected during the turning motion. And stable control of the turning motion can be realized.

According to a third aspect of the present invention, when the understeer state determination means determines that the vehicle is in an understeer state during turning acceleration, the understeer state determination unit suppresses the required torque for the engine control device mounted on the vehicle. It is characterized by making it.
According to the third aspect of the invention, the understeer state determination means causes the engine control device mounted on the vehicle to suppress the required torque when it is determined that the vehicle is in the understeer state during the turning acceleration. In addition to the effects of the first aspect of the invention, the vehicle behavior can be smoothly shifted from the understeer state to the neutral turning state from the viewpoint of engine torque.

According to the present invention, in a vehicle motion control system including a braking force control means and a rear wheel toe angle control means, even when the vehicle is in an understeer state or an oversteer state during a turning motion , the behavior of the vehicle is controlled. It is possible to smoothly shift from the understeer state or the oversteer state to the neutral turning motion state.

1 is an overall conceptual diagram of a vehicle to which a vehicle motion control system according to an embodiment of the present invention is applied. It is a block diagram which shows the function structure of vehicle motion control ECU. It is a flowchart which shows the flow of control in the understeer state and oversteer state of a VSA control part. It is a flowchart which shows the flow of control in the understeer state and oversteer state of a VSA control part. It is a flowchart which shows the flow of control in a rear-wheel toe angle control part. It is explanatory drawing of a vehicle motion when it determines with an understeer state during a left turn of a vehicle, (a) is explanatory drawing in the conventional case, (b) is explanatory drawing in the case of this embodiment. . It is explanatory drawing of a vehicle motion when it determines with an oversteer state during a left turn of a vehicle, (a) is explanatory drawing in the conventional case, (b) is explanatory drawing in the case of this embodiment. .

<Overview>
First, an overall outline of a vehicle 1 to which a vehicle motion control system according to an embodiment of the present invention is applied will be described with reference to FIG.
FIG. 1 is an overall conceptual diagram of a vehicle to which a vehicle motion control system according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing a functional configuration of the vehicle motion control ECU.
For example, the vehicle 1 is configured such that the engine E and the transmission TM are horizontally placed in the front part of the vehicle, and the front left and right wheels (steered wheels) 3FL and 3FR are driven by driving force transmission means (not shown). This is a front-wheel drive vehicle using left and right wheels (rear wheels) 3RL, 3RR as driven wheels. Each wheel 3FL, 3FR, 3RL, 3RR is fitted with a tire T, and brake devices 4FL, 4FR, 4RL, 4RR are incorporated.
As shown in FIG. 1, the vehicle 1 controls an electric power steering device 100, toe angle changing devices 120L and 120R, a vehicle brake hydraulic pressure control device (braking force control means) 150, and them as a vehicle motion control system. The vehicle motion control ECU 15 as a control unit is included.

  The vehicle motion control ECU 15 includes, for example, a microcomputer including a CPU, a ROM, a RAM, an input interface circuit for inputting various signals to the microcomputer, an output interface circuit for outputting output signals from the microcomputer, and a postscript A linear solenoid valve included in the hydraulic pressure unit 16 and a drive circuit for driving the motor are included.

The vehicle motion control ECU 15 has an EPS control unit 23 that functions as a control unit of the electric power steering apparatus 100 described above as a functional block configuration realized by the CPU executing a program stored in advance in the ROM, and a toe angle. It has a rear wheel toe angle control unit 24 that functions as a host control unit of the change devices 120L and 120R, and a VSA (vehicle stability assist) control unit 22 that functions as a control unit of the vehicle brake fluid pressure control device 150. Yes.
Here, the toe angle changing devices 120L and 120R and the rear wheel toe angle control unit 24 constitute "rear wheel toe angle control means" described in the claims of the present invention.

The vehicle 1 detects a handle operation angle sensor S _AH that detects a handle operation angle θ _H (see FIG. 2) that is an operation amount of the steering handle 6, and a yaw rate γ (see FIG. 2) that shows a turning rate of the vehicle body. Yaw rate sensor Sγ, lateral G sensor Sα _Y for detecting lateral acceleration (hereinafter also referred to as “lateral G” for short) of the vehicle body, and longitudinal G sensor Sα for detecting longitudinal acceleration (hereinafter also referred to as “front and rear G” for short) of the vehicle body _X , front left and right wheels 3FL, 3FR, and rear left and right wheels (rear wheels) 3RL, 3RR, and wheel speed sensors 5FL, 5FR, 5RL, 5RR for detecting the respective wheel speeds. A signal from the sensor is input to the vehicle motion control ECU 15.

The signal from the steering torque sensor S _T for detecting the applied to the pinion shaft of an electric power steering apparatus 100 steering torque T _rq (see FIG. 2), a motor rotation angle of the EPS motor 7 to be described later theta _M (see FIG. 2) motor rotational angle sensor S _AM for detecting an accelerator depression amount signal from the accelerator sensor S _AC for detecting the amount of depression of the accelerator pedal AP, the brake depression amount from the brake sensor S _BR for detecting a depression amount of the brake pedal BP A signal, a signal of a brake SW (see FIG. 2) from a brake switch (SW) 36 that detects that the brake pedal BP is depressed, and the like are input to the vehicle motion control ECU 15.

When it is not necessary to distinguish the position of the wheel in the future, the wheel 3FL, 3FR, 3RL, 3RR is shown in FIG. 1, but it is typically referred to as the wheel 3 and is similarly provided on each wheel 3. When there is no need to distinguish the position of the wheel to which the later-described brake device and wheel speed sensor are attached, the brake device 4 and the wheel are simply replaced instead of the brake devices 4FL, 4FR, 4RL, 4RR. Instead of the speed sensors 5FL, 5FR, 5RL, 5RR, they are simply referred to as wheel speed sensors 5. Further, regarding the wheel speed detected by the wheel speed sensor 5, when it is not necessary to distinguish the position of the wheel, the wheel speed VW _FL , VW _FR , VW _RL , VW _RR is simply replaced with the wheel speed in FIG. It is called speed VW.

Incidentally, the vehicle 1 is provided with an engine control ECU 13 that controls the engine E, and is connected to the vehicle motion control ECU 15 via a communication line, for example, CAN (Controller Area Network) communication.
The engine control ECU 13 also includes, for example, a microcomputer including a CPU, a ROM, a RAM, an input interface circuit for inputting various signals to the microcomputer, an output interface circuit for outputting an output signal from the microcomputer, and the like. It consists of
The engine control ECU 13, the vehicle motion control ECU 15, and the motor drive circuit 25 are supplied with electric power from a power source such as a battery (not shown).

《Electric power steering device》
First, an outline of the configuration of the electric power steering apparatus 100 will be described.
In FIG. 1, an electric power steering apparatus 100 includes a steering shaft provided with a steering handle 6 and a pinion shaft connected by an intermediate shaft (not shown) and a universal joint (universal joint), and a lower end of the pinion shaft. The pinion gear provided in the section meshes with the rack teeth of the rack shaft 8 that can reciprocate in the vehicle width direction, and the left and right wheels 3FL, 3FR on the front side are connected to both ends of the rack shaft 8 via tie rods 9. Has been. With this configuration, the electric power steering apparatus 100 can change the traveling direction of the vehicle when the steering handle 6 is operated.
The pinion gear provided at the lower end of the pinion shaft and the rack teeth of the rack shaft 8 constitute a rack and pinion mechanism 10.

  The electric power steering apparatus 100 includes an electric power steering motor 7 (hereinafter referred to as “EPS (Electric Power)” that supplies a steering assist force for reducing the manual steering force by the steering handle 6 and a steering resistance force to the steering handle 6. The worm gear provided on the output shaft of the EPS motor 7 meshes with the worm wheel gear provided on the pinion shaft to constitute the speed reduction mechanism 11. For example, a DC motor is used as the EPS motor 7.

The electric power steering apparatus 100 also includes an EPS control unit 23 as a functional component of the vehicle motion control ECU 15, a motor drive circuit 25 that drives the EPS motor 7, and a steering torque _Trq applied to the pinion shaft (see FIG. 2). steering torque sensor S _T to be detected, the differential amplifier circuit not shown for amplifying an output of the steering torque sensor S _T, is configured to include a like steering angle sensor S _AH.

The motor drive circuit 25 includes a plurality of switching elements such as an H-type bridge circuit, for example, and generates a rectangular wave current using a DUTY signal from the EPS control unit 23 of the vehicle motion control ECU 15 as shown in FIG. And a power supply circuit for driving the EPS motor 7. The motor drive circuit 25 has a function of detecting motor current using a motor current sensor (not shown) and a function of detecting motor voltage using a motor voltage sensor (not shown).
Motor rotational angle sensor S _AM is provided on the EPS motor 7 detects a motor rotation angle of the EPS motor 7 theta _M (see FIG. 2), and outputs the motor rotation angle theta _M signals of the vehicle motion control ECU 15.

(EPS control unit)
The EPS control unit 23 has a known configuration and is omitted in FIG. 2, but for example, two-dimensional map data of the vehicle speed VS and the steering torque _Trq is stored in the ROM in advance, and the vehicle speed VS and the steering torque T Referring to _rq , the base target current value corresponding to the steering assist force is calculated based on the two-dimensional map data, and the base current calculation unit that outputs to the motor drive circuit 25 and the rising characteristic of the steering assist force are corrected. An inertia compensator, a damper compensator for calculating a motor rotation angular velocity from the motor rotation angle θ _M of the EPS motor 7 and adjusting a steering assist force from the turning angular velocity of the wheels 3FL, 3FR, and the like. The damper compensator outputs a corrected current value for correcting the base target current value, and outputs the corrected target current value to the motor drive circuit 25.
The EPS control unit 23 has a deviation unit that detects an actual current value or voltage value from the motor drive circuit 25 and calculates a difference from the corrected target current value. Performs feedback control according to the deviation of the target current value.

《Toe angle changing device and rear wheel toe angle control unit》
(Toe angle changing device)
Next, the toe angle changing devices 120L and 120R and the rear wheel toe angle control unit 24 will be described.
As shown in FIG. 1, the vehicle 1 is provided with toe angle changing devices 120 </ b> L and 120 </ b> R as described in FIGS. 3 and 4 of JP 2008-201173 A, for example.
The toe angle changing devices 120L and 120R are attached to the left and right wheels 3RL and 3RR on the rear side of the vehicle 1, respectively. The toe angle changing device 120L includes an actuator 17L and a toe angle changing control ECU 18L. Similarly, the toe angle changing device 120R includes an actuator 17R and a toe angle changing control ECU 18R.
The toe angle changing devices 18L and 18R are respectively the target toe angles for the left and right rear wheels (rear wheels) 3RL and 3RR from the rear wheel toe angle control unit 24 of the vehicle motion control ECU 15 which is a higher-level control unit. The stroke position signals from the stroke sensors 38 and 38 are fed back and controlled so that the actual toe angles θ _TL and θ _TR of the wheels 3RL and 3RR coincide with θ ^* _TTL and θ ^* _TTR (see FIG. 2).

  The actuators 17L and 17R are provided with the stroke sensor 38 that detects the stroke position. The stroke sensor 38 includes, for example, a magnet and can detect the position using magnetism. As described above, by detecting the position using the stroke sensor 38, the toe-in and toe-out rudder angles of the left and right wheels 3RL and 3RR on the rear side, that is, the toe angle can be individually detected with high accuracy. Yes.

Further, toe angle change control ECUs 18L and 18R are integrally attached to the actuators 17L and 17R, respectively. The toe angle change control ECUs 18L and 18R are fixed to the case main body of the actuators 17L and 17R, and are connected to the stroke sensor 38 via a connector or the like. The left and right toe angle change control ECUs 18L and 18R are connected to the vehicle motion control ECU 15 via a communication line.
The toe angle change control ECUs 18L and 18R are supplied with electric power from a power source such as a battery (not shown) mounted on the vehicle.
Note that the toe angle change control ECUs 18L and 18R include a motor drive circuit including a switching element that drives a motor built in the actuators 17L and 17R.

(Rear wheel toe angle controller)
Next, the functional configuration of the rear wheel toe angle control unit 24 will be specifically described with reference to FIG. The rear wheel toe angle control unit 24 includes, for example, a target toe angle calculation unit 41 that calculates target toe angles θ _TTL and θ _TTR based on three-dimensional target toe angle map data 41a stored in advance in a ROM, and VSA control. The target toe angle θ _TTL or the target toe angle θ calculated by the target toe angle calculating unit 41 when the wheel 22 RL or the wheel 3 RR inside or outside the turn is determined to be an understeer state or an oversteer state described later in the unit 22. Instead of the _TTR , the toe angle change control ECU 18L or the toe angle change control is replaced with a new target toe angle θ ^* _TTL or target toe angle θ ^* _TTR that becomes a toe-in according to the required yaw moment amount from the VSA control unit 22. A target toe angle correction unit 42 output to the ECU 18R is included.
The detailed function of the target toe angle correction unit 42 will be described in the description of the flowchart of FIG.

The target toe angle calculation unit 41 has a handle operation angle time differentiation unit (not shown) that calculates the handle operation angular velocity θ ′ _H by differentiating the handle operation angle θ _H with respect to time. The target toe angle map data 41a of the target toe angle calculation unit 41 is, for example, three-dimensional map data of the steering angle θ _H , the absolute value of the steering angle angle θ ′ _H , and the vehicle speed VS. Specifically, when the vehicle speed VS indicates a slow, behind the wheel 3RL, front wheels 3FL a steered wheel to 3RR, the 3FR opposite phase, the target toe angle according to the steering wheel steering angle theta _H set toe angle theta _TTL, the theta _TTR, gain speed VS is in the first or the predetermined vehicle speed value, setting the toe angle corresponding to the steering wheel steering angle theta _H target toe angle theta _TTL reverse phase, the theta _TTR Is designed to attenuate. When the vehicle speed VS is equal to or higher than a second predetermined vehicle speed value greater than the first predetermined vehicle speed, the toe angle corresponding to the steering angle θ _H is set to the target toe angles θ _TTL and θ _TTR in phase with the wheels 3FL and 3FR. In many cases, the gain is gradually increased with the vehicle speed VS and saturated.
However, the target toe angle map data 41a, even if the second or more predetermined vehicle speed value the vehicle speed VS is the absolute value of the steering angle theta _H is or large angle greater than a predetermined value, the steering angular velocity theta _'H When the absolute value is greater than or equal to the predetermined value, the data structure is such that the target toe angles θ _TTL and θ _TTR of the opposite phase corresponding to the steering angle θ _H are set, and the danger avoidance movement during high speed driving is prevented. In many cases, it can be done accurately.

《Vehicle brake fluid pressure control device》
Next, the vehicle brake hydraulic pressure control device 150 will be described.
As shown in FIG. 1, the vehicle brake fluid pressure control device 150 is for appropriately controlling the braking force (brake fluid pressure) applied to each wheel 3 of the vehicle 1, and is provided with an oil passage and various parts. The hydraulic unit 16 and the VSA control unit 22 that is a functional unit of the vehicle motion control ECU 15 that is a control unit for appropriately controlling various components in the hydraulic unit 16 are mainly configured.

The VSA control unit 22 includes a wheel speed VW from a wheel speed sensor 5 that detects the wheel speed of the wheel 3 (see FIG. 2, but in FIG. 2, VW _FL , VW corresponding to the position of each wheel 3. _FR , VW _RL , VW _RR ) signals, steering wheel 6 operating angle θ _H signal from steering wheel operating angle sensor S _AH , lateral acceleration from lateral G sensor Sα _{Y of} vehicle 1 (in FIG. A signal of α _Y, a signal of yaw rate γ from the yaw rate sensor Sγ that detects the yaw rate of the vehicle 1 (see FIG. 2), a signal of the longitudinal acceleration α _X of the vehicle 1 from the front and rear G sensor Sα _X , accelerator depression amount signal from the accelerator sensor S _AC for detecting the amount of depression of the accelerator pedal AP (not shown in FIG. 2), the signal (Fig brake depression amount from the brake sensor S _BR for detecting a depression amount of the brake pedal BP Figure 2 Optional), a brake switch (SW) signal for detecting that stepping on the brake pedal BP is input to the VSA control unit 22.

The VSA control unit 22 is based on, for example, input from the wheel speed sensor 5, the steering wheel operation angle sensor S _AH , the lateral G sensor Sα _Y , the yaw rate sensor Sγ, and the front and rear G sensor Sα _X , and programs and data stored in the ROM. The control is executed by performing each calculation process.
The brake device 4 provided on each wheel 3 is a hydraulic device that converts the brake hydraulic pressure generated by the master cylinder M and the hydraulic unit 16 into the operating force of the brake device 4 provided on each wheel 3. A wheel cylinder is included, and each wheel cylinder is connected to the hydraulic unit 16 of the vehicle brake hydraulic pressure control device 150 via a pipe.

  As shown in FIG. 1, the hydraulic unit 16 of the vehicular brake hydraulic pressure control device 150 includes a master cylinder M that is a hydraulic pressure supply unit that generates a brake hydraulic pressure corresponding to a pedaling force applied to the brake pedal BP by the driver. The brake device 4 (shown as 4FL, 4FR, 4RL, and 4RR in FIG. 1) is disposed between the brake device 4 and a detailed configuration thereof, for example, in FIGS. 1 to 3 of Japanese Patent Laid-Open No. 2007-30745. It is the same as that described, and detailed description is omitted. In normal times, the depression force of the brake pedal BP is transmitted to each brake device 4FL, 4RR, 4RL, 4FR.

  Further, the hydraulic unit 16 of the vehicle brake hydraulic pressure control device 150 turns when it is determined that the driver is in the understeer state even when the driver is not operating the brake pedal BP, under the control of the VSA control unit 22. It has a function of a hydraulic circuit that increases the braking force of the inner wheel and assists to increase the braking force of the wheel on the outer side of the turn and maintain a stable turning motion of the vehicle when it is determined that the vehicle is oversteered. ing.

(VSA controller)
Next, detailed functions of the VSA controller 22 will be described with reference to FIG.
The VSA control unit 22 includes a vehicle speed calculation unit 50, an ABS (Anti-lock Brake System) control unit 51, a standard yaw rate calculation unit 53, an understeer amount calculation unit (understeer state detection means) 55, an oversteer amount calculation unit (oversteer state detection unit). Means) 56, a brake control amount calculation unit 57, and an engine control amount calculation unit 58.
The vehicle speed calculation unit 50 calculates the vehicle speed VS from each wheel speed VW and inputs it to the ABS control unit 51 in the VSA control unit 22 as well as the EPS control unit 23 and the rear wheel toe angle control unit 24 described above. input.

  The ABS control unit 51 has a conventionally known ABS function, calculates the slip ratio of each wheel 3 from the vehicle speed VS and each wheel speed VW during braking, and brake fluid for each wheel so that each wheel 3 does not lock. Adjust pressure. Further, the ABS control unit 51 performs control for preventing slipping of the driving wheels by calculating slip ratios of the wheels 3FL and 3FR that are driving wheels during acceleration or the like.

The reference yaw rate calculation unit 53 has three-dimensional map data 53a of a steering wheel operation angle θ _H , a lateral acceleration (displayed as “lateral G” in FIG. 2) α _Y , and a vehicle speed VS stored in advance in a ROM. The reference yaw rate γ _T is calculated based on the three-dimensional map data 53 a with reference to the steering wheel operation angle θ _H , the lateral acceleration α _Y , and the vehicle speed VS, and is input to the understeer amount calculator 55 and the oversteer amount calculator 56.

The understeer amount calculation unit 55 calculates a deviation Δγ (= γ _T −γ) between the reference yaw rate γ _T calculated by the reference yaw rate calculation unit 53 and the yaw rate _γ from the yaw rate sensor S _γ , and γ _T is negative ( Left turn), γ _T + ε ₁ ≦ γ, or γ _T is positive (right turn) and γ _T −ε ₁ ≧ γ, it is determined as an understeer state, and based on Δγ The requested yaw moment amount is calculated and output to the brake control amount calculating unit 57 and the target toe angle correcting unit 42 together with a determination flag (understeer flag IFLAGA = 1) indicating an understeer state.
If the understeer state is not determined, a determination flag (understeer flag IFLAGA = 0) is output to the brake control amount calculation unit 57 and the target toe angle correction unit 42.

Note that the understeer amount calculating unit 55 has been omitted in FIG. 2, the longitudinal acceleration alpha _X from the longitudinal G sensor S.alpha _X, and the lateral acceleration alpha _Y from the lateral G sensor S.alpha _Y, accelerator from an accelerator sensor S _AC When the depression amount is appropriately input and the understeer state is determined, and the acceleration state is determined, the requested yaw moment amount is sent to the engine control amount calculation unit 58 together with the determination flag indicating the understeer state (understeer flag IFLAGA = 1). Output.

The oversteer amount calculation unit 56 calculates a deviation Δγ (= γ _T −γ) between the reference yaw rate γ _T calculated by the reference yaw rate calculation unit 53 and the yaw rate _γ from the yaw rate sensor S _γ , and γ _T is negative ( Left turn), and γ _T −ε ₂ ≧ γ, or γ _T is positive (right turn) and γ _T + ε ₂ ≦ γ, it is judged as an oversteer state and based on Δγ The requested yaw moment amount is calculated and output to the brake control amount calculating unit 57 and the target toe angle correcting unit 42 together with a determination flag (oversteer flag IFLAGB = 1) indicating an oversteer state.
When the oversteer state is not determined, a determination flag (oversteer flag IFLAGB = 0) is output to the brake control amount calculation unit 57 and the target toe angle correction unit 42.

Incidentally, in the understeer amount calculation unit 55 and the oversteer amount calculation unit 56, the threshold value ε ₁ and the threshold value ε ₂ used for the determination of the understeer state or the oversteer state are positive values and are appropriately set. At that time, the threshold value ε ₁ = ε ₂ may be satisfied, or the threshold value ε ₁ ≠ ε ₂ may be satisfied.

When the determination flag input from the understeer amount calculation unit 55 or the oversteer amount calculation unit 56 is the understeer flag IFLAGA = 1, the brake control amount calculation unit 57 sets the front and rear wheels 3FL, 3RL or 3FR, For 3RR, depending on the required yaw moment amount, the front and right wheel speeds VW _FL and VW _FR and the rear left and right wheel speeds VW _RL and VW _RR are taken into account, and signals are sent to the required valves of the hydraulic unit 16. Is output, the brake fluid pressure is adjusted, and braking force is applied.
Incidentally, the hydraulic pressure unit 16 controls the vehicle motion control ECU 15 to control the master cylinder hydraulic pressure and the required portion of the hydraulic circuit in order to control the brake hydraulic pressure in the ABS control unit 51 and the brake control amount calculation unit 57. The pressure is detected and output.

  The engine control amount calculation unit 58 outputs a signal for suppressing the required torque to the engine control ECU 13 according to the engine rotational speed NE input from the engine control ECU 13 and the required yaw moment amount from the understeer amount calculation unit 55. To do.

<< Cooperative control of VSA control and rear wheel toe angle control in understeer state and oversteer state >>
Next, the vehicle stabilization control during the turning motion of the vehicle 1 by the braking control of the wheels 3 when it is determined as the understeer state and the oversteer state in the VSA control unit 22 with reference to FIG. 3 to FIG. The operation of the target toe angle correction unit 42 in the rear wheel toe angle control unit 24, which is a feature of the present invention, will be described.
3 and 4 are flowcharts showing the control flow in the understeer state and the oversteer state of the VSA control unit, and FIG. 5 is a flowchart showing the control flow in the rear wheel toe angle control unit.
FIG. 6 is an explanatory diagram of vehicle motion when it is determined that the vehicle is in an understeer state during a left turn, (a) is an explanatory diagram of a conventional case, and (b) is an example of this embodiment. It is explanatory drawing. FIGS. 7A and 7B are explanatory diagrams of vehicle motion when it is determined that the vehicle is in an oversteer state during a left turn, FIG. 7A is an explanatory diagram of a conventional case, and FIG. 7B is a case of the present embodiment. It is explanatory drawing.
First, the vehicle stabilization control during the turning motion of the vehicle 1 by the braking control of the wheels 3 when the understeer state and the oversteer state are determined in the VSA control unit 22 will be described with reference to FIGS. 3 and 4.

In step S01, the VSA controller 22 initially resets the understeer state determination flag (understeer flag) IFLAGA = 0 and the oversteer state determination flag (oversteer flag) to IFLAGB = 0.
In step S02, the VSA control unit 22 controls the steering wheel operating angle θ _H , the vehicle speed VS, the lateral acceleration α _Y (shown as “lateral Gα _Y ” in FIG. 2), the yaw rate γ, and the wheel speeds VW _FL , VW _FR , Reads VW _RL and VW _RR .
In step S03, the standard yaw rate calculation unit 53 calculates the standard yaw rate γ _T from the three-dimensional map data 53a based on the steering wheel operation angle θ _H , the vehicle speed VS, and the lateral acceleration α _Y.

In step S04, based on the normative yaw rate γ _T calculated in step S03 and the yaw rate γ, γ _T is negative, γ _T + ε ₁ ≦ γ, or γ _T is positive, and γ _T − Check if ε ₁ ≧ γ. If No in step S04, the process proceeds to step S05. If Yes in step S04, the process proceeds to step S06.
In step S05, the understeer amount calculation unit 55 outputs the understeer flag IFLAGA = 0 to the brake control amount calculation unit 57 and the target toe angle correction unit 42 without determining the understeer state (“IFLAGA = 0”). Then, it progresses to step S08 according to a connector (A).

In step S06, the understeer amount calculation unit 55 determines that the state is an understeer state, calculates a requested yaw moment amount based on Δγ (= γ _T −γ), and calculates the brake control amount together with the understeer flag IFLAGA = 1. To the unit 57 and the target toe angle correction unit 42.
Thereafter, the control in steps S24 and S25 in the target toe angle correction unit 42 shown in FIG. 5 is taken over.

In step S07, since the understeer flag IFLAGA = 1 input from the understeer amount calculation unit 55, the brake control amount calculation unit 57 calculates the required yaw moment amount and the four wheel speeds, that is, the front left and right wheel speeds VW _FL. , VW _FR , brake devices 4FL and 4RL for the front and rear wheels 3FL and 3RL inside the turn based on the left and right wheel speeds VW _RL and VW _RR on the rear side, or brake devices 4FR for the front and rear wheels 3FR and 3RR inside the turn, Calculate the brake fluid pressure for 4RRL and output a control signal to the fluid pressure unit 16 (“Calculate the front and rear wheel brake fluid pressure inside the turn based on the required yaw moment amount and the wheel speed of the four wheels, and output "). Thereafter, the process returns to step S02 according to the connector (B).

Although is omitted in the flowchart of FIG. 3, in step S06, the understeer amount calculating unit 55, when it is determined that the understeer state during turning acceleration based on the further longitudinal acceleration alpha _X and the lateral acceleration alpha _Y is an engine control The requested yaw moment amount and the understeer flag IFLAGA = 1 are also output to the amount calculation unit 58, and the engine control ECU 13 is caused to output a request torque suppression signal.

In step S08, based on the normative yaw rate γ _T calculated in step S03 and the yaw rate γ, γ _T is negative, γ _T −ε ₂ ≧ γ, or γ _T is positive, and γ _T It is checked whether + ε ₂ ≦ γ. If No in step S08, the process proceeds to step S09. If Yes in step S08, the process proceeds to step S10.
In step S09, the oversteer amount calculation unit 56 outputs the oversteer flag IFLAGB = 0 to the brake control amount calculation unit 57 and the target toe angle correction unit 42 without determining that the state is an oversteer state (“IFLAGB = 0”). Thereafter, the process returns to step S02 according to the connector (B).

In step S10, the oversteer amount calculation unit 56 determines that the state is an oversteer state, calculates a requested yaw moment amount based on Δγ (= γ _T −γ), and together with the oversteer flag IFLAGB = 1, the brake control amount calculation unit 57 and the target toe angle correction unit 42.

In step S11, since the oversteer flag IFLAGB = 1 input from the oversteer amount calculation unit 56, the brake control amount calculation unit 57 determines the requested yaw moment amount and the four wheel speeds, that is, the front left and right wheel speeds VW _FL , Based on VW _FR , rear left and right wheel speeds VW _RL , VW _RR , brake devices 4FL, 4RL for the front and rear wheels 3FL, 3RL on the outside of the turn, or brake devices 4FR, 4RR for the front and rear wheels 3FR, 3RR on the outside of the turn And the control signal is output to the hydraulic unit 16 ("Calculate and output the front and rear wheel brake hydraulic pressures on the outside of the turn based on the required yaw moment amount and the wheel speed of the four wheels") ).

Thereafter, the control in steps S26 and S27 in the target toe angle correction unit 42 shown in FIG. 5 is taken over.
Thereafter, the process returns to step S02 according to the connector (B).
This repeating process stops when the ignition key is turned off.

Next, with reference to FIG. 5, the stability of the vehicle trajectory during the turning motion of the vehicle 1 by the toe angle control of the rear wheels 3RL or 3RR when the rear wheel toe angle control unit 24 determines the understeer state and the oversteer state. Control will be described.
In step S21, the target toe angle calculation unit 41 reads the steering wheel operation angle θ _H and the vehicle speed VS. In step S22, the target toe angle calculation unit 41 calculates the handle operation angular velocity θ ′ _H by differentiating the handle operation angle θ _H with respect to time.
In step S23, the target toe angle calculation unit 41 determines the target toe angle map data 41a (“target toe angle map” in the flowchart of FIG. 5) based on the steering wheel operating angle θ _H , the steering wheel operating angular velocity θ ′ _H , and the vehicle speed VS. The target toe angles θ _TTL and θ _{TTR of} the rear wheels 3RL and 3RR (displayed as “rear wheel target toe angles θ _TTL and θ _TTR ” in the flowchart of FIG. 5) are set.

In step S24, the target toe angle correction unit 42 checks whether or not the state determination flag IFLAGA = 1. If IFLAGA = 1 (Yes), that is, if understeered, the process proceeds to step S25. If IFLAGA ≠ 1 (No), the process proceeds to step S26.
In step S25, the target toe angle correction unit 42 converts the toe angle of the rear wheel 3RR (wheel 3RL) outside the turn to a predetermined toe-in angle according to the requested yaw moment amount input from the understeer amount calculation unit 55. The corrected target toe angle θ ^* _TTR (target toe angle θ ^* _TTL ) is set. The toe angle of the rear wheel 3RL (wheel 3RR) inside the turn is corrected to the target toe angle θ ^* _TTL corrected with the value of the target toe angle θ _TTL (target toe angle θ _TTR ) set in step S23. (Corrected target toe angle θ ^* _TTR ) (“correction by setting the toe-in angle of the rear outer wheel according to the required yaw moment amount”).
In this embodiment, the toe angle of the rear wheel on the outer side of the turn is set so that the larger the required yaw moment amount, the larger the toe angle becomes on the toe-in side. However, the present invention is not limited to this. A predetermined fixed toe-in angle may be set.

As a result, as shown in FIG. 6A, for example, when it is determined that the vehicle is understeered by turning left, in the conventional case, the braking force F _{VSA1 is} applied to the front and rear wheels 3FL, 3RL inside the turn by VSA control. , F _VSA2 is applied and the yaw moment M _VSA is generated by the VSA control. At the same time, for example, the wheels 3RL and 3RR are controlled in the opposite phase by the rear wheel toe angle control, and the yaw moment M _RTC is generated. The trajectory of the rear part of 1 is controlled so as to bulge outward as indicated by an arrow Trac_rea, and the trajectory of the vehicle 1 as a whole bulges outward of the turning, and thus the turning motion is stably controlled.

On the other hand, in this embodiment, as shown in part A of FIG. 6B, the rear wheel 3RR on the outside of the turn is set to toe-in, the yaw moment M _RTC is not generated, and the vehicle 1 Since the rear trajectory is controlled to be pushed inward as indicated by an arrow Trac_rea, the trajectory of the entire vehicle 1 does not swell outwardly and the driver feels a smooth turning motion as indicated by a solid line in the traveling direction. Stable turning control is provided. In particular, as the yaw moment M _VSA is large, the toe angle of the wheel 3RR is largely set to toe-side, Trac_rea is stronger, pushed the turning inward sense rear of the vehicle 1 is sensory (spins swayed outward ) Can be suppressed.

  In addition, because the toe angle control is performed on the outer wheel 3RR that is different from the inner wheel 3RL that is braking, the friction circle of the inner wheel 3RL during the turning motion is not affected. There is no need to adversely affect the braking force of the wheel 3RL.

Returning to the flowchart of FIG. 5, in step S <b> 26, the target toe angle correction unit 42 checks whether or not the state determination flag IFLAGB = 1. If IFLAGA = 1 (Yes), that is, if oversteered, the process proceeds to step S27. If IFLAGA ≠ 1 (No), the series of control is terminated, the process returns to step S21, and the series of control is repeated. .
In step S27, the target toe angle correction unit 42 converts the toe angle of the rear wheel 3RL (wheel 3RR) inside the turn to a predetermined toe-in angle according to the requested yaw moment amount input from the oversteer amount calculation unit 56. And set the corrected target toe angle θ ^* _TTL (target toe angle θ ^* _TTR ). Then, the toe angle of the rear wheel 3RR (wheel 3RL) inside the turn is corrected with the target toe angle θ ^* _TTR corrected with the value of the target toe angle θ _TTR (target toe angle θ _TTL ) set in step S23. (Corrected target toe angle θ ^* _TTL ) (“correction by setting the toe-in angle of the rear inner wheel according to the required yaw moment amount”).
In the present embodiment, the toe angle of the rear wheel on the inner side of the turn is set such that the larger the required yaw moment amount, the larger the toe angle becomes on the toe-in side. However, the present invention is not limited to this. A predetermined fixed toe-in angle may be set.

As a result, as shown in FIG. 7A, for example, when it is determined that the vehicle is in an oversteer state by turning left, in the conventional case, the braking force F _{VSA1 is} applied to the front and rear wheels 3FR, 3RR by VSA control. , F _VSA2 is applied and the yaw moment M _VSA is generated by the VSA control. At the same time, for example, the wheels 3RL and 3RR are controlled in the opposite phase by the rear wheel toe angle control, and the yaw moment M _RTC is generated. The trajectory of the rear portion of 1 is controlled as indicated by an arrow Trac_rea, and the stable control of the turning motion is performed in such a manner that the driver feels that the trajectory of the entire vehicle 1 is likely to enter the spin. The toe angle of the wheel 3RL at this time is θ _{TL (1)} on the toe-in side.
On the other hand, in the present embodiment, as shown in part B of FIG. 7B, the rear wheel 3RL on the inner side of the turn has a larger toe angle θ _TL on the toe-in side than the toe-in θ _{TL (1). (2) Although} the yaw moment M _RTC is set and the trajectory of the rear portion of the vehicle 1 is controlled to be pushed out of the turn as indicated by the arrow Trac_rea, the trajectory of the entire vehicle 1 swells out of the turn and the traveling direction Stable turning control that gives the driver a feeling of smooth turning movement as indicated by the solid line.

  In addition, because the toe angle control is performed on the inner wheel 3RL that is different from the outer wheel 3RR that is braking, the friction circle of the outer wheel 3RR that is turning is not affected. There is no need to adversely affect the braking force of the wheel 3RR.

In this embodiment, the three functions of the VSA control unit 22, the EPS control unit 23, and the rear wheel toe angle control unit 24 are concentrated in the vehicle motion control ECU 15, but all three functions are handled by one CPU. It is not necessary and may be shared by a plurality of CPUs.
Further, it is divided into three ECUs including a microcomputer, an input / output interface circuit, and a necessary power supply drive unit, for example, a VSA control ECU, an EPS control ECU, and a rear wheel toe angle control ECU, and each ECU is connected by a communication line. You may make it connect.

DESCRIPTION OF SYMBOLS 1 Vehicle 3FL, 3FR, 3RL, 3RR Wheel 4FL, 4FR, 4RL, 4RR Brake device 5FL, 5FR, 5RL, 5RR Wheel speed sensor 6 Steering handle 7 EPS motor 8 Rack shaft 9 Tie rod 10 Rack pinion mechanism 11 Deceleration mechanism 13 Engine Control ECU
15 Vehicle motion control ECU
16 Hydraulic unit (braking force control means)
17L, 17R Actuator 18L, 18R Toe angle change control ECU
22 VSA control unit (braking force control means)
23 EPS control unit 24 Rear wheel toe angle control unit (rear wheel toe angle control means)
25 Motor drive circuit 36 Brake SW
38 stroke sensor 41 target toe angle calculation unit 42 target toe angle correction unit 50 vehicle speed calculation unit 51 ABS control unit 53 reference yaw rate calculation unit 55 understeer amount calculation unit (understeer state detection means)
56 Oversteer amount calculation unit (oversteer state detection means)
57 Brake control amount calculation unit 58 Engine control amount calculation unit 100 Electric power steering device 120L, 120R Toe angle changing device (rear wheel toe angle control means)
150 Brake hydraulic pressure control device for vehicle (braking force control means)
AP accelerator pedal BP brake pedal M master cylinder S _AC accelerator sensor S _AH steering wheel angle sensor S _AM motor rotation angle sensor S _BR brake sensor S _T steering torque sensor Sα _X longitudinal acceleration sensor Sα _Y lateral acceleration sensor Sγ yaw rate sensor T tire

Claims (3)

A braking force control means for performing control to apply different braking forces to the left and right wheels of the vehicle so as to generate a yaw moment in the vehicle, and an operation angle of a steering handle for changing the direction of the front wheel which is a steered wheel of the vehicle. A rear wheel toe angle control means for performing rear wheel toe angle control in response, and a vehicle motion control system comprising at least
Comprising an understeer state determining means for determining whether or not the turning state of the vehicle is an understeer state ;
When the understeer state determining means determines that the turning state of the vehicle is an understeer state, the braking force control means performs control to apply braking force to the front and rear wheels inside the turn, while the rear wheel toe angle control It means a vehicle motion control system which is characterized in that the toe angle control for directing the rear wheel of different pivot outwardly toe side of the turning inner wheel the braking force is applied. A braking force control means for performing control to apply different braking forces to the left and right wheels of the vehicle so as to generate a yaw moment in the vehicle, and an operation angle of a steering handle for changing the direction of the front wheel which is a steered wheel of the vehicle. A rear wheel toe angle control means for performing rear wheel toe angle control in response, and a vehicle motion control system comprising at least
An oversteer state determining means for determining whether the turning state of the vehicle is an oversteer state ;
When the oversteer state determination means determines that the turning state of the vehicle is an oversteer state, the braking force control means performs control to apply braking force to the front and rear wheels outside the turning, while the rear wheel toe angle control It means a vehicle motion control system which is characterized in that the toe angle control for directing the rear wheel of different turning inside the toe side of the turning outer wheel the braking force is applied. The understeer state determination means causes an engine control device mounted on the vehicle to suppress a required torque when the vehicle is determined to be in an understeer state during turning acceleration. The vehicle motion control system described.

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