JP2007069844A - Steering control device and steering control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering control device capable of controlling vehicle behavior at will of a driver when a steered angle of a rear wheel is controlled by yaw rate feedback control. <P>SOLUTION: At steering control that an turning state amount of the vehicle is fed-back and rear wheel steering is executed so as to obtain the desired vehicle behavior, when counter steering that the detected turning state amount and the steering direction becomes opposite is detected, the rear wheel steered angle of reverse phase is given to the steering angle regardless of the turning state amount of the vehicle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering control device, and more particularly to vehicle behavior control for obtaining desired vehicle characteristics.

  For example, Patent Document 1 discloses a steering device that performs control so that the rear wheel steering angle is given in reverse phase with respect to the front wheel steering angle in the low speed range, and the rear wheel steering angle is given in phase with respect to the front wheel steering angle in the high speed range. The described techniques are disclosed. In this publication, when a yaw rate larger than the target yaw rate occurs and an oversteer tendency occurs, the oversteer tendency is suppressed by prohibiting the rear wheel steering angle control even in the low speed range ( Hereinafter, this is referred to as yaw rate feedback control).

Further, in the technique described in Patent Document 2, when yaw rate feedback control is similarly performed, if anti-lock brake control (hereinafter referred to as ABS control) on a low μ road or the like intervenes, it is assumed that the yaw rate deviates from the target yaw rate. However, the control of lowering the rear wheel steering angle control amount is intervened to stabilize the vehicle behavior at low speeds and low μ roads.
JP 61-241276 A Japanese Patent No. 3212183

  However, in the technique of Patent Literature 1, even if the rear wheel steering angle control amount is reduced by the yaw rate feedback control when the oversteer tendency is detected, the rear wheel is in a state where a large yaw rate is actually generated. In order to reduce the rudder angle, there was a risk that control intervention would be delayed. Further, when the driver applies counter-steer in order to return the oversteer tendency to the neutral steer by himself, there is a problem that the effect of the counter-steer is reduced because the rear wheel steering angle is set small.

  In the technique of Patent Document 2, although the rear wheel rudder angle control amount is reduced during ABS control, excessive yaw is generated in most cases other than straight braking when braking on a low μ road. Also in this case, when the driver applies counter steer, the rear wheel steering angle is set to be small, so that there is a problem that the effect of counter steer becomes small.

  The present invention has been made paying attention to the above-mentioned problem, and an object thereof is a steering control device capable of controlling the vehicle behavior in accordance with the driver's intention when controlling the auxiliary steering angle by the yaw rate feedback control. Is to provide.

  In order to achieve the above object, in the steering control device of the present invention, a rear wheel steering actuator that gives a steering angle to a rear wheel of a vehicle, a turning state amount detecting means that detects a turning state amount of the vehicle, and a steering angle Based on the target turning state amount calculating means for calculating the target turning state amount of the vehicle, and a first target rear wheel steering for calculating the first rear wheel steering angle at which the detected turning state amount becomes the target turning state amount. In a steering control device comprising angle calculation means and rear wheel steering angle servo control means for controlling the rear wheel steering actuator so as to obtain a target rear wheel steering angle, the detected turning state amount and steering direction, Counter steer detecting means for detecting counter steer that is opposite, second target rear wheel steering angle calculating means for calculating a second rear wheel steering angle in phase opposite to the steering angle, and when counter steer is detected The target rear wheel rudder angle is set to the first And switching means from target rear-wheel steering angle switch to wheel steering angle after the second target, characterized by comprising a.

  Therefore, since the amount that the rear wheel rudder angle can be turned in the opposite phase at the same time as the countersteer is increased, it becomes possible to obtain the opposite yaw to the yaw to be canceled according to the driver's intention, and to stabilize the vehicle behavior Can be achieved.

  The best mode for realizing the steering control device and the steering control method of the present invention will be described below based on the embodiments shown in the drawings.

[Configuration of vehicle control system]
FIG. 1 is a system configuration diagram illustrating a vehicle control system according to a first embodiment. The vehicle according to the first embodiment controls an engine controller (hereinafter referred to as ECU) 1 that controls an engine, an automatic transmission controller (hereinafter referred to as ATCU) 2 that controls an automatic transmission, and various meters. A meter controller (hereinafter referred to as “MCU”) 3, a steering angle sensor 7 that detects the steering angle of the driver, and an integrated sensor 8 that detects vehicle behavior (yaw rate, lateral acceleration, longitudinal acceleration, etc.) are mounted. Yes.

  The steering angle sensor 7 is provided with a controller 7a that outputs an electrical signal detected according to a change in angle as an angle signal, and a value obtained by removing a noise component or the like is output every predetermined period (for example, every 10 msec). . Further, the integrated sensor 8 is provided with a controller 8a for outputting an electric signal detected according to a change in the behavior of the vehicle as a yaw rate signal, a lateral acceleration signal, and a longitudinal acceleration signal, and a value obtained by removing noise components and the like. It is output every predetermined period (for example, every 5 msec).

  Further, there are a rear wheel steering unit 50 capable of controlling the steering angle of the rear wheel 5a with respect to the steering angle of the driver, and a brake unit 60 capable of independently controlling the braking force of each wheel 4a, 5a according to the traveling state. It is installed.

  The rear wheel steering unit 50 includes a rear wheel controller 5 and a rear wheel actuator 51 that operates based on a command from the rear wheel controller 5, and is disposed in the vicinity of the rear wheel behind the vehicle. The brake unit 60 includes a brake controller 6 and a brake actuator 61 that operates based on a command from the brake controller 6, and is disposed in the engine room.

  The ECU 1, ATCU 2, MCU 3, steering angle sensor 7, brake controller 6, and rear wheel controller 5 are provided with a low-speed communication control port and are connected by a low-speed CAN communication line 100 (corresponding to low-speed communication means). The communication speed of the low-speed CAN communication line 100 is configured so that data output from each controller can be transmitted and received every 10 msec.

  In CAN communication, a combination of a high signal and a low signal is output to two communication lines, and a bit signal is transmitted / received based on a deviation between these signals. Therefore, even if a signal is disturbed due to a disturbance or the like, a disturbance occurs simultaneously on the two communication lines. Therefore, a stable bit signal can be transmitted and received by taking a deviation. Further, in this communication line, sensor signals and the like output from each controller are output at a constant cycle or every time an event occurs, and only a necessary controller receives necessary information.

  The rear wheel controller 5, the brake controller 6 and the integrated sensor 8 are provided with a high-speed communication control port and are connected by a high-speed CAN communication line 200 (corresponding to high-speed communication means). The communication speed of the high-speed CAN communication line 200 is configured so that data output from each controller can be transmitted and received every 1 msec. In communication via the low-speed CAN communication line 100, the amount of data that can be transmitted / received within the unit time is small, and in communication via the high-speed CAN communication line 200, the amount of data that can be transmitted / received within the unit time is large. .

  As described above, the brake controller 6 and the rear wheel controller 5 are provided with both a high-speed communication control port and a low-speed communication control port, and are connected to both the high-speed CAN communication line 200 and the low-speed CAN communication line 100. Yes.

[Yaw rate feedback steering system]
FIG. 2 is a system diagram showing the configuration of the yaw rate feedback steering system. In the vehicle of the first embodiment, when a driver generates a certain steering angle at a certain vehicle speed, it is optimal to achieve this degree of yaw rate as a steering feeling and vehicle characteristics. It is equipped with a yaw rate feedback steering system that gives the steering angle to the wheels. That is, a feedback control system including a yaw rate sensor and a lateral acceleration sensor is configured, and the rear wheel steering angle is controlled based on the driver's steering intention and the actually generated yaw rate. The control configuration will be described later.

(Configuration of rear wheel steering unit)
The rear wheel actuator 51 is provided between the left and right rear wheels 5a. The left and right rear wheels 5a are connected by a parallel link. When one side of this link is moved in the vehicle width direction by the rear wheel side motor 51, a steering angle is generated in the rear wheel 5a due to elastic deformation of the parallel link. Since this rear wheel actuator is a well-known technique, description thereof is omitted.

The rear wheel side motor 52 is provided with a rear wheel side rotation angle sensor 53 that detects the rotation angle of the rear wheel side motor 52 and is output to the rear wheel controller 5. In the rear wheel controller 5, a calculation unit 501 that calculates the driving amount of the rear wheel side motor 52 with respect to the target steering angle, and the control amount of the rear wheel side motor 52 are based on the detection value of the rear wheel side rotation angle sensor 53. A servo control unit 502 that performs feedback control, a rear wheel driver unit 503 that outputs a current value to the rear wheel motor 52, and the rear wheel speed based on the steering angle, vehicle speed, and yaw rate detected by the steering angle sensor 7. A target value calculation unit 504 that calculates the target rudder angle is provided.
The rear wheel controller 5 connected to the low-speed CAN communication line 100 includes the steering angle information from the steering angle sensor 7 connected to the low-speed CAN communication line 100 and the vehicle speed information from the ATCU 2 connected to the low-speed CAN communication line 100. The vehicle turning state information and the brake control operation signal from the brake controller 6 connected to the high-speed CAN communication line 200 are received, and the target value calculation unit 504 calculates the target rear wheel steering angle based on these values. . Details of the yaw rate feedback control will be described later.

  The rear wheel controller 5 drives the rear wheel motor 52 so as to achieve the calculated target rear wheel steering angle. At this time, the servo control unit 502 and the rear wheel side driver 503 calculate the control amount every 1 msec based on the detection value of the rear wheel side motor rotation angle sensor 53 and the value of the current sensor, etc. Output to the motor 52. Such processing is executed by multitask processing or the like, and is appropriately assigned according to the processing capability of the CPU.

[ABS / TCS / VDC control system]
FIG. 3 is a system diagram showing the configuration of the ABS / TCS / VDC control system. In the vehicle of the first embodiment, the slip state between the tire and the road surface is monitored, and the braking force is mainly controlled among the tire forces so as to obtain the highest braking force during braking (avoids locking of wheels). ABS control to be performed, TCS control to be able to transmit torque to the road surface most efficiently when driving force is output at the time of starting, etc. (so as not to slip beyond a predetermined slip ratio), and during turning An ABS / TCS / VDC control system that performs VDC control to suppress oversteer and understeer and to control the vehicle so as to obtain the desired vehicle behavior (by giving independent braking force to each wheel) is installed.

  Connected to the brake actuator 61 are a master cylinder 62 that generates brake fluid pressure by a driver's brake pedal operation, and a wheel cylinder 63 that generates braking force on each wheel. A wheel speed sensor 64 that detects the rotational speed of each wheel and a pressure sensor 62a that detects the master cylinder pressure are provided. In the brake actuator 61, a shut-off valve that shuts off the master cylinder 62 and the wheel cylinder 63, a pressure reducing valve that can reduce the hydraulic pressure in the wheel cylinder 63, and a hydraulic pressure in the wheel cylinder 63 are supplied to the driver. A pump or the like that can increase the pressure regardless of the intention is built in, and the braking force of each wheel can be controlled.

  The engine is provided with an electronic control injector 11 for controlling the fuel injection amount of the engine and an electronic control throttle 12 for controlling the throttle opening based on the command signal of the ECU 1 and controls the output torque of the engine as required. It is configured to be possible.

(About ABS control)
When the brake controller 6 detects the tendency of the wheel to lock, the wheel cylinder pressure that tends to lock is repeatedly increased and decreased, and the maximum braking force is secured by the optimum slip ratio.

(About TCS control)
When wheel drive slip is detected in the brake controller 6, a torque down command is output so as to reduce the output of the excessive engine, and fuel injection amount control and throttle opening control are performed to reduce the wheel drive slip. To prevent. Note that the wheel cylinder pressure of the drive wheel may be increased to prevent the slip, or the drive slip may be avoided by outputting an upshift command to the ATCU 2, which is not particularly limited.

(About VDC control)
The ABS control and the TCS control are controls that control the behavior of the vehicle in the front-rear direction, and the VDC control is a control in the left-right direction (turning state) of the vehicle. When the driver performs steering at a certain vehicle speed, load movement and yaw rate are generated accordingly. At this time, since the limit value of the cornering force of the tire is estimated in advance, a target yaw rate that does not exceed the limit value is calculated. The actual yaw rate detected by the integrated sensor 8 is compared with the target yaw rate. If the actual yaw rate exceeds the target yaw rate, an oversteer tendency occurs, and it is determined that an excessive yaw rate has occurred. A braking force is generated on the outer turning wheel and / or the rear turning inner wheel. On the other hand, if the actual yaw rate is smaller than the target yaw rate, an understeer tendency tends to occur, and it is determined that sufficient yaw rate has not occurred. Is generated. That is, the vehicle behavior is controlled by yaw rate feedback control.

  In the ABS / TCS / VDC control system, each sensor value is subjected to a fail check by logical monitoring with other sensor values. Here, the logic monitor compares, for example, the yaw rate value of the integrated sensor 8 with the yaw rate theoretical value based on the vehicle speed and the steering angle, and monitors whether these values are consistent.

(Control configuration of yaw rate feedback steering)
FIG. 4 is a block diagram illustrating a control configuration of the target value calculation unit 504. Each configuration will be described below. The steering angle coefficient setting unit 5041 sets the steering angle coefficient Kθ based on the vehicle speed. The yaw rate coefficient setting unit 5042 sets the yaw rate coefficient Kγ based on the vehicle speed. The steering angle coefficient Kθ is a characteristic that is opposite in phase to the entire vehicle speed as in the steering angle gain map of FIG. 4, and that the absolute value of the value decreases and decreases as the vehicle speed Vsp decreases in the low to medium speed range. The yaw rate coefficient Kγ has the same phase throughout the vehicle speed as shown in the yaw rate gain map of the figure, and is a characteristic that gradually increases and changes as the vehicle speed increases.

  The multiplier 5043 receives the steering angle θ and the steering angle coefficient Kθ, calculates a multiplication value Kθ · θ between them, and outputs it to a first target rear wheel steering angle calculation unit 5045 described later. Similarly, the multiplier 5045 inputs the yaw rate γ and the yaw rate coefficient Kγ, and outputs the multiplication value Kγ · γ of both to the first target rear wheel steering angle calculation unit 5045.

In the first target rear wheel steering angle calculation unit 5045, based on these two multiplied values Kθ · θ and Kγ · γ, the first target rear wheel steering angle δ1 * is expressed by the following equation δ1 * = Kγ · γ + Kθ · θ
Calculated by Therefore, the term Kγ · γ is a stable element that keeps the vehicle on the stable side, and the term Kθ · θ is a turning element that promotes turning.

  Here, the yaw rate γ is generated over the entire vehicle speed according to the turning of the vehicle due to turning or disturbance, and this coefficient Kγ is a characteristic of an increasing function of the vehicle speed Vsp. Therefore, the value of Kγ · γ increases as the vehicle speed Vsp increases. The steering angle θ is generally very small in the medium and high speed range, and therefore the value of Kθ · θ is close to zero even if the coefficient Kθ is small in the opposite phase direction. Therefore, when the yaw rate γ is detected in the middle and high speed range, the first target rear wheel steering angle δ1 * is in the same phase direction according to the value of Kγ · γ, and is controlled with emphasis on stability. In a low speed range where the steering angle θ is large, the control is performed with emphasis on turning ability by the value of Kθ · θ in the opposite phase direction, and at this time, the value is corrected to the stable side by the value of Kγ · γ in the same phase direction of the yaw rate γ.

  The provisional gain setting unit 5046 receives a brake control operation signal indicating whether the ABS / VDC / TCS control is operated from the brake controller 6. When this operation signal is input, it is switched to the provisional gain Kθ ′ and output to the multiplier 5043. The provisional proportional gain Kθ ′ is calculated by multiplying the steering angle coefficient Kθn immediately before the input of the brake control operation signal and the reduction constant G.

The decreasing constant G is a temporal delay constant that gradually decreases as a function of time, for example, and is set by G = Ts / (1 + Ts) by the time constant T and the Laplace operator s.
Therefore, the temporary proportional gain Kθ '
Kθ ′ = G · Kθn, G = Ts / (1 + Ts)
Is calculated and output.

  The counter steer detection unit 5047 calculates the target yaw rate γ * based on the vehicle speed Vsp and the steering angle θ, and the yaw rate γ (turning state amount) generated by the driver in the vehicle based on the steering angle θ and the yaw rate γ. ) To determine whether the steering wheel is in a counter-steer state in which the steering wheel is operated in the opposite direction. At this time, when the actual yaw rate γ is larger than the target yaw rate γ * and the counter steer state is set, a command for switching the target value is output to a target value switching unit 5049 described later.

  The second target rear wheel steering angle calculator 5048 calculates a second target rear wheel steering angle δ2 * that is in opposite phase to the steering angle θ. This second target rear wheel rudder angle δ2 * is determined to have a strong intention to suppress the excessive yaw rate γ with an oversteer tendency when the steering angle θ is large. Therefore, the second target rear wheel rudder angle δ2 * is also large. Is set. Not only the steering angle θ but also the vehicle speed Vsp, the accelerator pedal opening degree, etc. may be set. Specifically, when the vehicle speed Vsp is high, a large yaw rate γ is likely to be generated, so the reverse-phase rear wheel steering angle may be set large. Further, when the accelerator pedal opening is small, it may be determined that the degree of urgency is higher and a large reverse-phase rear wheel steering angle may be set.

  The target value switching unit 5049 selects the first target rear wheel steering angle δ1 * when the counter steer is not detected, and switches to the second target rear wheel steering angle δ2 * when the counter steer is detected. The target rear wheel rudder angle switched to the part 501 is output. In the calculation unit 501, rear wheel steering angle servo control is executed based on the given target rear wheel steering angle.

(Yaw rate feedback steering control process)
Next, the operation of this embodiment will be described. FIG. 6 is a flowchart showing the yaw rate feedback steering control.

[First target rear wheel rudder angle calculation process]
In step S1, it is determined whether or not a brake control operation signal is input. If not, the process proceeds to step S2 to clear the flag, and if it is input, the process proceeds to step S5.

  In step S3, the steering angle coefficient Kθ and the yaw rate coefficient Kγ are set according to the vehicle speed Vsp, and in step S4, the first target rear wheel steering angle δ1 * is calculated by the steering angle θ, its coefficient Kθ, the yaw rate γ, and its coefficient Kγ. To do. Thereafter, servo control is executed in step S15, and the rear wheel steering angle is controlled.

  Therefore, the reverse phase steering angle proportional control and the yaw rate feedback control are executed so that the rear wheel 5a is in phase or in reverse phase and a desired yaw rate is obtained. Therefore, if the steering wheel is turned largely at a low speed such as when starting, the target rear wheel steering angle δ * becomes negative due to the value of Kθ · θ, and the rear wheel 5a is turned in a small turn by reverse phase steering. If the vehicle turns suddenly or the yaw rate γ increases due to the road surface μ and the yaw rate γ increases, the reverse phase steering of the rear wheel 5a is corrected to decrease by the value of Kγ · γ, and the behavior of the vehicle is stabilized.

  In turning at medium and high speeds, the target rear wheel steering angle δ1 * becomes positive mainly by the value of Kγ · γ, and the rear wheel 5a is steered in phase, so that the stability of the vehicle during turning is improved. In addition, when the vehicle suddenly turns to the left or right due to disturbance such as a crosswind, the yaw rate γ is greatly increased or decreased, and this behavior change of the vehicle is detected quickly. Then, the rear wheel 5a is steered by the value of Kγ · γ so as to maintain the in-phase state despite the vehicle turning. For this reason, the vehicle is stably positioned so as not to be swept away by crosswinds, and smoothly returns to the original course.

[First target rear wheel rudder angle calculation process after correction]
In step S5, it is determined whether or not the flag is 0. If it is 0, the process proceeds to step S6. Otherwise, the process proceeds to step S3, and a normal first target rear wheel steering angle calculation process is executed.

  In step S6, it is determined whether the yaw rate γ is larger than the target yaw rate γ *. If larger, the process proceeds to step S10, and otherwise, the process proceeds to step S7.

  In step S7, a provisional proportional gain Kθ ′ is calculated.

  In step S8, it is determined whether or not the absolute value of the provisional proportional gain Kθ ′ is equal to or smaller than a predetermined value that represents substantially 0. When the absolute value is larger than the predetermined value, the temporary proportional gain Kθ ′ is used. Switch to coefficient.

  For example, when a braking operation is performed during traveling on a low μ road such as a snowy road, if the road surface reaction force cannot be obtained and the wheel tends to be locked, the wheel speed rapidly decreases. At this time, the wheel cylinder pressure is appropriately reduced, held, and increased by ABS control, thereby preventing wheel lock. At this time, when the brake control operation signal is input to the provisional gain setting unit 5046, the process proceeds from step S1 to step S5 to check the flag, and in step S7, the provisional proportional gain Kθ ′ is determined by the steering angle coefficient Kθn and the decrease constant G. Is calculated.

  Even if the driver turns the steering wheel on a slippery road surface, the value of Kθ ′ · θ becomes very small and has no effect. Steering is carried out so as to keep it stable in the state, and yaw rate feedback control is strengthened. Therefore, when ABS control is performed at the time of braking on a slippery road surface, the rear wheel steering control is further coordinated to keep the vehicle behavior in a stable state, thereby preventing sudden changes in vehicle behavior during braking. .

[Yaw rate feedback steer control during counter steer detection]
In step S10, it is determined whether the direction of the yaw rate γ is rightward. If it is rightward, the process proceeds to step S12, and if it is leftward, the process proceeds to step S11.

  In step S11, it is determined whether or not the direction of the steering angle θ (steering direction) is leftward. If it is leftward, it is determined that the counter steer is applied and the process proceeds to step S13. Otherwise, the process proceeds to step S15. The servo control is executed based on the first target rear wheel steering angle δ1 *.

  In step S12, it is determined whether or not the direction of the steering angle θ (steering direction) is rightward. If the steering angle θ is rightward, it is determined that the counter steer is applied and the process proceeds to step S13. Otherwise, the process proceeds to step S15. The servo control is executed based on the first target rear wheel steering angle δ1 *.

  In step S13, the second target rear wheel steering angle δ2 * is calculated.

  In step S14, the target rear wheel steering angle δ * is switched from the first target rear wheel steering angle δ1 * to the second target rear wheel steering angle δ2 * in the target value switching unit 5049.

  In step S15, servo control is executed based on the switched target rear wheel steering angle.

  The operation of the yaw rate feedback steer control at the time of detecting the counter steer will be described.

  First, a scene that requires counter steer will be described. FIG. 8 is a diagram showing the relationship between the lateral acceleration G and the vehicle speed Vsp during steady circle turning. Until the tire grip limit, the lateral acceleration G increases linearly to the vehicle speed Vsp in accordance with the vehicle speed Vsp and the circular turning angular acceleration ω. However, if the tire grip limit is exceeded, the cornering force and the centrifugal force cannot be balanced, and skidding begins to occur (indicated by V1 in FIG. 8).

  For example, in the case of a rear-wheel drive vehicle, the driving force is transmitted to the rear wheels, so the tire grip force must share the driving force and the cornering force. On the other hand, since the driving force is not transmitted to the steering wheel on the front side, only the cornering force needs to be shared with the grip force of the tire. For this reason, the cornering force on the front side is inevitably larger than the cornering force on the rear side, and a large yaw is generated, so that the vehicle tends to oversteer. The cornering force has a correlation with the side slip angle between the tire and the road surface, and may be considered to be proportional to a certain level. That is, when the side slip angle is decreased, the cornering force is decreased, and when the side slip angle is increased, the cornering force is increased.

  This oversteer tendency can be suppressed by reducing the front cornering force. Therefore, when the driver gives the counter steer, the side slip angle acting on the steered wheel is small or reverse, and the front cornering force is small or reverse. As a result, the yaw rate generated in the vehicle can be suppressed, the balance with the cornering force on the rear side can be balanced, and the oversteer tendency can be suppressed. The above is a scene that requires counter steer.

(Counter steer when brake braking control is not activated)
FIG. 7 is a time chart showing the change in yaw rate when the driver applies counter-steer. This time chart represents a case where the vehicle starts on a low μ road with the steering angle θ1 applied since the vehicle stopped. In FIG. 7, the thin line represents the actual yaw rate of the prior art, the thick line represents the actual yaw rate γ of Example 1, and the thick dotted line represents the target yaw rate γ *. Further, the steering angle θ, the vehicle speed Vsp, and the lateral acceleration G at this time are represented.

  As shown in the time chart of FIG. 7, in the conventional technology, the rear wheel steering angle (first target rear wheel steering angle δ1 *) opposite in phase to the steering angle θ in a low vehicle speed range such as when starting. ) Is given. At this time, if a yaw rate γ greater than the target yaw rate γ * occurs, the rear wheel steering angle coefficient is set to a small value, and the reverse-phase rear wheel steering angle is set to a small value, thereby suppressing the generation of the yaw rate. . Therefore, even if the driver hits the counter steer, the rear wheel rudder angle in reverse phase with respect to the steering angle θ is small, the rear side slip angle cannot be obtained sufficiently, and the cornering force cannot be increased. The yaw suppression effect by steer cannot be obtained sufficiently.

  Therefore, in the first embodiment, when the driver hits the countersteer, the rear wheel steering angle opposite in phase to the steering angle is sufficiently given (second target rear wheel steering angle δ2 *). The side slip angle of the wheel was set to be large, and the cornering force on the rear side was secured sufficiently. Thereby, the yaw rate γ can be more quickly converged to the target yaw rate γ * side.

(Counter steer when brake braking control is activated)
Next, the operation at the time of brake braking control operation will be described. As described above, when the vehicle is oversteered, the driver applies a countersteer to operate the vehicle to maintain its posture. In the case of ABS control, etc., the conventional technology reduces the rear-wheel steering angle in reverse phase, so even if the driver applies counter-steer during ABS control, the cornering force of the rear wheels can be secured. It was difficult.

  On the other hand, in the first embodiment, even during the ABS control, when the actual yaw rate γ is larger than the target yaw rate γ * and the counter steer is applied, the rear wheel steering angle that is a large reverse phase is used. Two target rear wheel rudder angle δ2 * was given. As a result, when the vehicle behavior is disturbed during ABS control and the driver is trying to stabilize the posture, the yaw rate can be converged more quickly to the target yaw rate side by making it easier to secure the cornering force of the rear wheels. .

  Further, not only ABS control but also similar effects can be obtained when performing VDC control. Basically, in VDC control, the braking force of each wheel is controlled so as to obtain a target yaw rate. In general, the VDC control reduces the generated yaw rate and achieves a driving state in accordance with the driver's intention. In this state, for example, when the reverse phase control is executed in the low vehicle speed range, the control is performed in the direction in which the yaw rate is generated. Wheel steering is stopped and VDC control is preferentially executed.

  At this time as well, when the driver feels that the behavior control by the VDC control is insufficient and the counter steer is applied, the vehicle behavior can be converged more quickly by applying a reverse-phase rear wheel steering angle.

Hereinafter, the effects of the first embodiment will be listed.
(1) When counter steer is detected, the target rear wheel steering angle is switched from the first target rear wheel steering angle δ1 * to the second target rear wheel steering angle δ2 *. In other words, since the amount by which the rear wheel steering angle is turned in the opposite phase simultaneously with the countersteer is increased, it becomes possible to obtain a yaw opposite to the yaw to be canceled according to the driver's intention, and to stabilize the vehicle behavior. Can be planned.

  (2) The first target rear wheel rudder angle calculation unit 5045 calculates the first target rear wheel rudder angle δ1 * smaller than that during non-ABS control when the ABS control is executed. At this time, the second target rear wheel steering angle calculation unit 5048 calculates the second target rear wheel steering angle δ2 * regardless of the execution state of the ABS control. Therefore, even when the ABS control is executed, when the counter steer is applied, it is possible to give the rear wheel steering angle having a large phase opposite to the steering angle θ, and the vehicle behavior in accordance with the driver's intention. Can be stabilized.

  (3) The first target rear wheel rudder angle calculation unit 5045 calculates the first target rear wheel rudder angle δ1 * smaller than that during non-VDC control when executing VDC control. At this time, the second target rear wheel steering angle calculation unit 5048 calculates the second target rear wheel steering angle δ2 * regardless of the execution state of the VDC control. Therefore, even when yaw that cannot be suppressed by VDC control occurs, it is possible to give a large rear wheel steering angle that is opposite in phase to the steering angle θ when the counter steer is applied. The vehicle behavior can be stabilized according to the intention of the person.

  (4) The second target rear wheel rudder angle calculation unit 5048 increases the second target rear wheel rudder angle δ2 * when the steering angle θ during counter steering is large. That is, when the steering angle θ at the time of countersteering is large, it can be determined that the intention to suppress the excessive yaw rate γ with an excessive oversteer tendency is strong. Therefore, by setting the second target rear wheel steering angle δ2 * to a large value, The behavior can be quickly converged. Not only the steering angle θ but also the vehicle speed Vsp, the accelerator pedal opening degree, etc. may be set. Specifically, when the vehicle speed Vsp is high, a large yaw rate γ is likely to be generated, so the reverse-phase rear wheel steering angle may be set large. Further, when the accelerator pedal opening is small, it may be determined that the degree of urgency is higher and a large reverse-phase rear wheel steering angle may be set.

  Next, Example 2 will be described. In the first embodiment, the vehicle that gives the auxiliary steering angle only to the rear wheels has been described. On the other hand, in the second embodiment, a vehicle that gives auxiliary steering angles to the front and rear wheels will be described.

  The basic control concept is the same as that of the first embodiment when the auxiliary steering angle is given to the front and rear wheels. Specifically, when it is desired to generate the yaw rate in the low vehicle speed range, the auxiliary steering angle control gain with respect to the steering angle θ is set large. As a result, the steering angle θ is controlled to be added to the front wheels, and the yaw rate is more effectively generated by giving the rear wheels the rear wheel steering angle opposite in phase to the steering angle θ. On the other hand, when it is desired to suppress the yaw rate in the high vehicle speed range, the auxiliary steering angle control gain with respect to the steering angle θ is set small. As a result, the steering angle θ is controlled to be subtracted from the front wheels, and the rear wheel steering angle in phase with the steering angle θ is given to the rear wheels, thereby suppressing the occurrence of yaw rate more effectively.

  That is, the yaw rate is generated by increasing the auxiliary steering angle control gain with respect to the steering angle θ, and the yaw rate is suppressed by reducing the auxiliary steering angle control gain. In addition, since an auxiliary steering angle can be given to the front and rear wheels in this way, two vehicle states such as yaw rate and lateral acceleration can be controlled simultaneously, but there is no particular limitation.

  In addition, as a mechanism that gives the auxiliary steering angle to the front wheel, that is, the steering wheel, the type using a planetary gear, the type using a harmonic drive, etc., the steering angle of the steering wheel by the motor and the pinion shaft of the rack and pinion mechanism Since a known technique capable of adding and subtracting the relationship with the rotation angle may be used as appropriate, the description is omitted.

  This vehicle is equipped with a brake control system capable of controlling the vehicle behavior as in the first embodiment. When the yaw rate γ is larger than the target yaw rate γ *, the auxiliary steering angle control gain for providing the auxiliary steering angle is reduced. To reduce the auxiliary rudder angle. Thereby, generation | occurrence | production of a yaw rate is suppressed and also vehicle behavior is stabilized by VDC control.

FIG. 9 is a flowchart showing the contents of yaw rate feedback steer control according to the second embodiment.
In step S21, the steering angle θ, the vehicle speed Vsp, and the yaw rate γ are read. In step S22, it is determined whether the yaw rate γ is larger than the target yaw rate γ *. If larger, the process proceeds to step S23. Proceed to S25.

  In step S23, a low auxiliary steering angle control gain is set, and the process proceeds to step S24 to start VDC control.

  In step S25, it is determined whether or not the counter steer is applied. If the counter steer is applied, the process proceeds to step S26 to set a high auxiliary steering angle control gain. Otherwise, go to step S29.

  In step S27, a normal auxiliary rudder angle control gain is set, and the process proceeds to step S28. If the VDC control is being executed, the control is terminated, and if not, the state is maintained as it is.

  In step S29, front and rear wheel target auxiliary steering angles are calculated based on the set auxiliary steering angle control gain.

  That is, when an oversteer tendency is detected in step S22, the auxiliary steering angle control gain is set to be small and VDC control is executed. When the counter steer is detected in this state, it is determined that the vehicle behavior is not sufficiently stabilized even by the VDC control, and the auxiliary steering angle control gain is increased to increase the auxiliary steering angle. Thereby, it becomes possible to obtain the same effect as described in the first embodiment, and the vehicle behavior can be effectively stabilized.

(Other examples)
In the first and second embodiments, the configuration in which the yaw rate generated in the vehicle is detected and the auxiliary steering angle is given based on the yaw rate has been described. For example, the auxiliary steering angle is given based on the steering angle θ and the vehicle speed Vsp. You may apply to the vehicle provided with the active steering control system and VDC control. At this time, the auxiliary steering angle control gain of the active steering control system is set to be small at the time of VDC control, but when the counter steer is detected, the auxiliary steering angle control gain is set to be set to a large value. Similar to Examples 1 and 2, the vehicle behavior can be stabilized effectively according to the driver's intention.

1 is a system configuration diagram illustrating a vehicle control system in Embodiment 1. FIG. 1 is a system diagram illustrating a configuration of a rear wheel steering system in Embodiment 1. FIG. It is a system diagram showing the structure of the ABS / TCS / VDC control system in Example 1. It is a block diagram showing the control structure of the target value calculating part in Example 1. 3 is a map showing a relationship between a vehicle speed, a steering angle coefficient, and a yaw rate coefficient in the first embodiment. 3 is a flowchart illustrating a yaw rate feedback steer control process according to the first embodiment. 6 is a time chart showing the yaw rate at the time of counter steering in Example 1 and the yaw rate at the time of counter steering in the prior art. It is a figure showing the relationship between the vehicle speed and lateral acceleration at the time of steady circle turning, and the grip limit of a tire. 12 is a flowchart illustrating a yaw rate feedback steer control process in the second embodiment.

Explanation of symbols

1 Engine controller (ECU)
2 Automatic transmission controller (ATCU)
3 Meter controller (MCU)
4a Front wheel 5a Rear wheel 5 Rear wheel controller 6 Brake controller 7 Steering angle sensor 8 Integrated sensor 9 Brake controller 50 Rear wheel steering unit 60 Brake unit

Claims (6)

A rear wheel steering actuator for providing a steering angle to the rear wheels of the vehicle;
A turning state amount detecting means for detecting a turning state amount of the vehicle;
A target turning state amount calculating means for calculating a target turning state amount of the vehicle based on the steering angle;
First target rear wheel steering angle calculating means for calculating a first rear wheel steering angle at which the detected turning state quantity becomes the target turning state quantity;
Rear wheel steering angle servo control means for controlling the rear wheel steering actuator to obtain a target rear wheel steering angle;
In a steering control device with
Counter steer detection means for detecting counter steer in which the detected turning state amount and the steering direction are opposite;
Second target rear wheel steering angle calculating means for calculating a second rear wheel steering angle larger than the first rear wheel steering angle in reverse phase with respect to the steering angle;
Switching means for switching the target rear wheel steering angle from the first target rear wheel steering angle to the second target rear wheel steering angle when the counter steer is detected;
A steering control device comprising: The steering control device according to claim 1, wherein
A braking force control actuator for controlling the braking force of each wheel;
A first braking force control means for executing a braking force control for avoiding the locking of the braking control actuator when the wheel lock is detected;
Provided,
The first target rear wheel rudder angle calculating means is a means for calculating the first target rear wheel rudder angle smaller than that during non-braking force control when the first braking force control is executed.
The second target rear wheel steering angle calculation means calculates the second target rear wheel steering angle regardless of the execution state of the first braking force control. The steering control device according to claim 1 or 2,
A braking force control actuator for controlling the braking force of each wheel;
A second braking force control means for calculating a target braking force at which the detected turning state amount becomes the target turning state amount, and executing a braking force control so as to obtain a target braking force for the braking control actuator;
Provided,
The first target rear wheel rudder angle calculating means is a means for calculating the first target rear wheel rudder angle smaller than that during non-braking force control when executing the second braking force control.
The second target rear wheel steering angle calculation means calculates the second target rear wheel steering angle regardless of the execution state of the second braking force control. The steering control device according to any one of claims 1 to 3,
The second target rear wheel rudder angle calculating means increases the target second rear wheel rudder angle when the steering angle during counter steering is large. In a steering control method for performing rear wheel steering so as to feed back a turning state amount of a vehicle and obtain a desired vehicle behavior,
When a counter steer in which the detected turning state quantity and the steering direction are opposite is detected, a rear-wheel steering angle opposite in phase to the steering angle is given regardless of the turning state quantity of the vehicle. Steering control method. An auxiliary steering angle actuator capable of giving an auxiliary steering angle to each wheel of the vehicle;
Auxiliary steering angle control gain setting means for setting an auxiliary steering angle control gain based on the running state of the vehicle;
Target value calculating means for calculating a target auxiliary steering angle based on the auxiliary steering angle control gain;
Rudder angle servo control means for outputting a drive signal to the auxiliary rudder angle actuator so as to be the calculated target value;
A braking force control means that feeds back a turning state amount of the vehicle and executes braking force control so as to obtain a desired vehicle behavior;
In a vehicle steering control device comprising:
A counter steer detection means for detecting a counter steer in which the detected turning state amount and the steering direction are opposite to each other is provided;
The auxiliary rudder angle control gain setting means sets the auxiliary rudder angle control gain to a smaller gain than when the braking force control is not executed when the braking force control is executed, and when the braking force control is executed and a counter When steering is detected, the auxiliary steering angle control gain is set to be greater than the small gain.

Images