JP5303333B2 - Vehicle rear wheel steering control device - Google Patents

Description

  The present invention relates to a rear wheel steering control device for an automobile (hereinafter simply referred to as a vehicle), and more specifically, while a vehicle equipped with an active front steering device is turning, the front wheels are steered in a direction opposite to the turning direction (counter steer). The present invention relates to a control device that steers rear wheels so that a vehicle travels stably when control is performed.

  A technique is disclosed in which, when the vehicle is turning, when the front wheels are steered in the direction opposite to the turning direction (counter steer), the rear wheels are steered at a phase opposite to the steering angle of the counter steer (see Patent Document 1). ). According to such a technique, the amount by which the rear wheel steering angle is steered in the opposite phase during the countersteering is increased so that the vehicle behavior intended by the occupant is obtained. On the other hand, an automatic counter steering control technique (active front steering device) is known that steers the front wheels of a vehicle independently of the steering operation of an occupant in accordance with the motion state of the vehicle that is turning.

JP 2007-69844 A

  When the vehicle turns at a low speed, the rear wheel steering control device steers the rear wheel of the vehicle in a phase opposite to that of the front wheel to improve turning performance. When the behavior of the vehicle becomes unstable while turning, the rear wheels are steered so as to be in a stable direction by feeding back the detected yaw rate. However, when the feedback control amount of the yaw rate becomes excessive, the behavior of the vehicle may be destabilized, so that the gain is not greatly amplified.

  On the other hand, when automatic counter steer control is performed, when the occupant steers the steering during the automatic counter steer control, control may be performed in which the front wheels are not steered to the opposite phase that causes counter steer.

  In the technique disclosed in Patent Document 1, when countersteering is performed, the rear wheels are steered at a phase opposite to the steering angle of the countersteer, and the steering amount in the opposite phase is further increased. However, when an automatic counter-steer control signal is detected, the vehicle may spin if control is performed to steer the rear wheels in the opposite phase while the front wheels are not steered in the counter-steer direction.

  The present invention has been made in view of the above-described background, and stabilizes the vehicle when the active front steering device provided in the vehicle controls to steer the front wheels in the direction opposite to the turning direction (counter steer) while the vehicle is turning. An object of the present invention is to provide a control device that steers the rear wheels so as to travel.

  The present invention is a rear wheel steering control device that is provided in a vehicle on which an active front steering device is mounted and that controls steering of the left and right rear wheels of the vehicle. The apparatus calculates a state quantity detection unit that detects a movement state quantity of the vehicle including a yaw rate, calculates an instruction toe angle based on the detected movement state quantity of the vehicle, and drives an actuator according to the instruction toe angle. And rear wheel toe angle control means for changing the toe angle of the left and right rear wheels of the vehicle. The active front steering device performs counter-steer control when a basic front wheel steering angle based on a driver's steering amount and a target front wheel steering angle based on a vehicle motion state amount do not match, and transmits a counter steering signal to the rear wheel When the counter steer is input, the rear wheel toe angle control unit amplifies the yaw rate gain and decreases the instruction toe angle setting gain. Yes.

  When a counter steer signal is input, the present apparatus does not steer the rear wheels to the opposite phase of the front wheels depending on the situation, but amplifies the gain of the yaw rate and decreases the set gain of the instruction toe angle. According to the above configuration, even when the rear wheel steering angle control corresponding to the counter steer is executed in a state where the front wheels are not steered in the counter steer direction when the automatic counter steer control signal is detected. The vehicle spin can be suppressed.

  According to the present invention, the active front steering device provided in the vehicle controls the rear wheels so that the vehicle can stably travel when controlling the front wheel to be steered (counter steer) in the direction opposite to the turning direction while the vehicle is turning. A control device for steering can be provided.

1 is a schematic configuration diagram of a four-wheeled vehicle according to an embodiment of the present invention. It is a functional block diagram which shows schematic structure of the main part of the rear-wheel steering control apparatus concerning one Embodiment of this invention. It is a functional block diagram which shows schematic structure of the active front steering apparatus principal part concerning one Embodiment of this invention. It is a flowchart of the rear-wheel steering control in the counter steer control concerning one Embodiment of this invention.

  Hereinafter, an embodiment in which a rear wheel steering control device according to the present invention is applied to a vehicle will be described with reference to the drawings. In the description, for the wheels and members arranged for them, that is, tires, electric actuators, etc., subscripts L or R indicating left and right are attached to the numerals, respectively, for example, rear wheel 5L (left), For example, the rear wheel 5R (right) is referred to as the rear wheel 5.

  FIG. 1 is a schematic configuration diagram of an automobile V to which a rear wheel steering control device 10 according to the present embodiment is applied. The vehicle V includes front wheels 3L and 3R to which tires 2L and 2R are attached, and rear wheels 5L and 5R to which tires 4L and 4R are attached. These front wheels 3L and 3R and rear wheels 5L and 5R are It is suspended from the vehicle body 1 by left and right front suspensions 6L, 6R and rear suspensions 7L, 7R.

  In addition, the vehicle V is provided for the front wheel steering device 9 that directly steers the left and right front wheels 3L and 3R via the rack and pinion mechanism and the left and right rear suspensions 7L and 7R by steering the steering wheel 8. The left and right actuators 11L and 11R are extended and retracted to provide a rear wheel steering control device 10 that individually changes the toe angles of the rear wheels 5L and 5R. Between the steering wheel 8 and the front wheel steering device 9, an active front steering device 18 (which can steer the front wheels of the vehicle independently of the occupant's steering operation according to the state of motion of the turning vehicle) ( Active Front Steer: hereinafter referred to as “AFS”). An electric actuator can be applied to the actuators 11L and 11R.

  The vehicle V includes an ECU (Electronic Control Unit) 12 that performs overall control of various systems, and a vehicle speed sensor 13, a steering angle sensor 14, a yaw rate sensor 15, a lateral acceleration sensor 16, a front wheel angle sensor 19, and the like are not shown. Various sensors are installed, and a detection signal of each sensor is input to the ECU 12 to be used for vehicle control. The steering angle sensor 14 detects the steering amount of the steering wheel 8. The lateral acceleration sensor 16 detects acceleration acting in the left-right direction of the vehicle. The front wheel rudder angle sensor 19 detects the steered angle of the front wheel 3. Here, these sensors, a toe angle sensor described later, and the like constitute state quantity detection means for detecting a vehicle state quantity relating to the behavior of the vehicle.

  The ECU 12 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and is connected to each of the sensors 13 to 16, 19 and the actuator 11 via a communication line. The ECU 12 calculates the rear wheel toe angle based on the detection results of the sensors 13 to 16, 19 and the like, determines the displacement amount of the actuators 11L and 11R, and executes the toe angle control of the rear wheel 5.

  The actuators 11L and 11R are respectively provided with toe angle sensors 17L and 17R for detecting the stroke position of the output rod. When the signals of the toe angle sensors 17L and 17R are input to the ECU 12, feedback control of the actuators 11L and 11R is performed. As a result, the actuators 11L and 11R expand and contract by a predetermined amount determined by the ECU 12 to accurately change the toe angles of the rear wheels 5L and 5R.

  According to the vehicle V configured in this way, the left and right actuators 11L, 11R are simultaneously symmetrically displaced to freely control toe-in / to-out of both rear wheels 5L, 5R under appropriate conditions. In addition, if one of the left and right actuators 11L and 11R is extended and the other is contracted, both rear wheels 5L and 5R can be steered left and right. For example, the vehicle V changes the rear wheel 5 to toe-out when accelerating, changes the rear wheel 5 to toe-in during braking, and changes the rear wheel 5 to the front wheel steering angle during high-speed turning, based on the motion state of the vehicle grasped by various sensors. In the same phase, the rear wheel 5 is controlled to the toe angle (turning) in the opposite phase to the front wheel rudder angle during low-speed turning, and the rear wheel toe angle control is performed in order to improve the maneuverability.

  Next, functions of the present embodiment will be described with reference to FIGS. FIG. 2 is a functional block diagram showing a schematic configuration of a main part of the rear wheel steering control device according to the present embodiment. FIG. 3 is a functional block diagram showing a schematic configuration of a main part of the active front steering apparatus according to the present embodiment. Control of the rear wheel steering control device and the active front steering device of this embodiment can be realized by the ECU 12.

  The ECU 12 is a kind of computer, a processor (CPU) that executes calculations, a storage area that temporarily stores various data, a random access memory (RAM) that provides a work area for calculations performed by the processor, and a program executed by the processor And a read-only memory (ROM) in which various data used for the operation are stored in advance, and a rewritable storage for storing the result of the operation by the processor and the data obtained from each part of the engine system A non-volatile memory is provided. The nonvolatile memory can be realized by a RAM with a backup function that is always supplied with a voltage even after the system is stopped.

  Referring to FIG. 2, the rear wheel toe angle setting unit 120 of the ECU 12 obtains and calculates the vehicle state quantity from the vehicle speed sensor 13, the yaw rate sensor 15, the front wheel steering angle sensor 19, an in-cylinder pressure sensor (not shown), and the like. Alternatively, the driving force of the left and right rear wheels 5L and 5R is estimated based on the estimated engine torque, the transmission gear ratio, and the like, and the instruction torque is calculated from the estimation result of the rear wheel driving force and the detection result of the lateral acceleration sensor 16. The angle k2 × θDT is set. k2 is a coefficient, the content of which will be described later.

  The ECU 12 subtracts the actual toe angle θTR detected by the toe angle sensor 17 disposed in the actuator 11 from the indicated toe angle k2 × θDT and sent to the ECU 12 via an input interface (not shown). Deviation e is calculated. The deviation e is input to the FB controller 123, and the FB controller 124 generates a drive signal for driving the actuator 11 in a direction to eliminate the deviation via an output interface (not shown).

  The rear wheel toe angle setting unit 120 and a rear wheel toe angle calculation unit 122 that calculates an instruction toe angle from the motion state quantity of the vehicle, and a yaw rate that amplifies the gain of the detected yaw rate when a counter steer signal is input. A gain adjustment unit 121 and a toe angle gain adjustment unit 123 that decreases the set gain of the instruction toe angle are provided. The counter steer signal is a control gain output from a counter steer control unit 130 (see FIG. 3), which will be described later, and steers the front wheels in the counter steer direction by the active front steering device in accordance with the motion state amount of the vehicle V. Control amount.

  More specifically, the yaw rate gain adjustment unit 121 sets a coefficient k1 corresponding to a control gain that is a counter steer signal, and k1 × γ obtained by multiplying the coefficient k1 by the yaw rate γ detected by the yaw rate sensor 15 is the rear wheel toe angle. Output to the calculation unit 122. The coefficient k1 is a coefficient for amplifying the gain of the yaw rate. The toe angle gain adjusting unit 123 sets a coefficient k2 corresponding to the control gain that is a counter steer signal, and k2 × θDT obtained by multiplying the coefficient k2 by the instruction toe angle θDT calculated by the rear wheel toe angle calculating unit 122. Is calculated as a toe angle control amount. The coefficient k2 is a coefficient for decreasing the set gain of the instruction toe angle θDT.

  Next, the active front steer counter steer control will be described with reference to FIG. The counter control unit 130 of the ECU 12 includes a counter steer calculation unit 131, a comparator 132, and a control amount calculation unit 133. The counter steer calculation unit 131 acquires motion state quantity signals from the vehicle speed sensor 13, the yaw rate sensor 15, the lateral acceleration sensor 16, and the like via an input interface (not shown) of the ECU 12, and based on these motion state quantities. The countersteer steering angle θSA is calculated. The calculated counter steering angle θSA is compared with the steering angle θSD operated by the occupant detected by the front wheel angle sensor 14 in the comparator 132. If they are different, the control amount calculation unit 133 calculates the control gain of the counter steer as will be described later in the process.

  The ECU 12 is detected by the front wheel steering angle sensor 19 disposed in the front wheel steering device 9 that is operated by the active front steering device 18 from the steering angle θSC that is the control gain calculated by the control amount calculation unit 133, and an input interface (FIG. The deviation e is calculated by subtracting the actual front wheel steering angle θSR sent to the ECU 12. The deviation e is input to the AFSFB controller 134, and the AFSFB controller 134 generates an operation signal for operating the active front steering apparatus 18 in a direction to eliminate the deviation via an output interface (not shown).

  On the other hand, the control gain of the counter steer calculated by the counter control unit 130 is sent to the yaw rate gain adjustment unit 121 and the toe angle gain adjustment unit 123 (see FIG. 2).

  Next, an example of a control process in the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart for setting the coefficients k1 and k2 for the rear wheel steering control in the counter steer control according to the present embodiment. Referring to FIG. 4, the counter steer control unit 130 of the ECU 12 acquires motion state amount signals from the vehicle speed sensor 13, the yaw rate sensor 15, the lateral acceleration sensor 16, and the like (step S <b> 101), and based on these motion state amounts. The steering angle θSC is calculated.

  Based on the calculated steering angle θSC and the steering angle θSD operated by the occupant, it is determined whether or not the vehicle is a counter steer where the front wheels are steered in the direction opposite to the turning direction while the vehicle is turning (step S102). When the steering angle (basic front wheel rudder angle) based on the driver's steering amount does not match the rudder angle (target front wheel rudder angle) calculated based on the vehicle motion state quantity, counter steer control is performed. When it is not counter steer (step S102: NO), the coefficients k1 and k2 are both set to 1 (steps S107 and S108), and this process is terminated.

  When it is determined that the steering angle is counter steer (step S102: YES), a counter steer signal that is a control amount of the counter steer is sent to the yaw rate gain adjustment unit 121. The yaw rate gain adjustment unit 121 sets the coefficient k1 with reference to the map MAP1 (step S104) set in advance and stored in the memory of the ECU 12, for example, according to the control gain that is a counter steer signal (step S103). .

  The counter steer signal is also sent to the toe angle gain adjusting unit 123. The toe angle gain adjusting unit 123, for example, according to the control gain that is the counter steer signal, for example, a map MAP2 (preset and stored in the memory of the ECU 12). Referring to step S106), coefficient k2 is set (step S105), and the process ends. As shown in FIG. 2, the set coefficients k1 and k2 are multiplied by the observation amount and the control amount as proportional coefficients for the amplification of the yaw rate gain and the decrease of the indicated toe angle gain, respectively.

  As described above, in the prior art, the rear wheels are steered in the opposite phase to the front wheels based on the signal that counter control has been executed. However, there is a case where the counter steer control is performed, and when the occupant steers the steering during the counter steer control, the front wheels may not be steered to the opposite phase that causes the counter steer. The feedback control of the yaw rate in the rear wheel steering control steers the rear wheel in the direction opposite to the direction in which the yaw rate is generated, so a large difference occurs with respect to the standard steering angle, and a large amount of control is required. The control amount could not be increased from the viewpoint of safe driving of the vehicle.

  On the other hand, in the configuration of the present embodiment, the gain of the yaw rate is increased and the set gain of the indicated toe angle is decreased according to the control amount of the counter control. Even in this case, it is possible to realize stable traveling of the vehicle.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and can be modified and used without departing from the spirit of the present invention.

V Automobile 1 Car body 3 Front wheel 5 Rear wheel 6 Front suspension 7 Rear suspension 10 Rear wheel toe angle control device 11 Actuator 12 ECU
13 Vehicle speed sensor 14 Front wheel rudder angle sensor 15 Yaw rate sensor 16 Lateral acceleration sensor 17 Toe angle sensor 18 Active front steering device 120 Rear wheel toe angle setting unit 121 Yaw rate gain adjustment unit 122 Instruction toe angle calculation unit 123 Toe angle gain adjustment unit 124 FB Controller 130 Countersteer controller 131 Countersteer calculator 132 Comparator 133 Control amount calculator 134 AFSFB controller

Claims (1)

A rear wheel steering control device that is provided in a vehicle equipped with an active front steering device and controls steering of the left and right rear wheels of the vehicle,
State quantity detecting means for detecting a movement state quantity of the vehicle including a yaw rate;
A command toe angle is calculated based on the detected amount of motion of the vehicle, and an actuator is driven according to the command toe angle so that the front wheel rudder is at the same time as the front wheel rudder angle at high speed turning by driving an actuator. Rear wheel toe angle control means for changing the toe angle of the left and right rear wheels of the vehicle so as to be in opposite phase to the angle,
The active front steering device performs counter-steer control when a basic front wheel steering angle based on a driver's steering amount and a target front wheel steering angle based on a vehicle motion state amount do not match, and transmits a counter steering signal to the rear wheel Output to toe angle control means,
When the counter steer signal is input, the rear wheel toe angle control means amplifies the gain of the yaw rate according to the control amount of the counter steer control by the active front steering device , and sets the indicated toe angle gain. A rear-wheel steering control device characterized in that

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