JP2007045227A - Vehicle turning control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle turning control device capable of stabilizing steering stability even at rear wheel steering abnormality of four-wheel steering. <P>SOLUTION: The vehicle turning control device is provided with front wheel steering means 2, 4, 5 for performing steering operation so as to turn the front wheels FR, FL of the vehicle; steering assist control means 8, 13 for applying steering assist force and steering attenuation force at steering operation of the front wheel steering means 2, 4, 5; rear wheel turning control means 9, 10, 13 for turning the rear wheels RR, RL of the vehicle; and neutral direction turning means 11, 13 for turning the rear wheels RR, RL in a neutral direction when an abnormality is detected on the rear wheel turning control means 9, 10, 13. The steering assist control means 8, 13 increase attenuation coefficient of steering attenuation force when turning in the neutral direction of the rear wheels RR, RL is tried by the neutral direction turning means 11, 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle turning control device capable of applying a steering assist force and a steering damping force during a steering operation.

A vehicle usually turns a front wheel by steering a steering wheel, and thereby turns. Here, in order to improve the maneuverability when the vehicle travels including turning, a four-wheel steering vehicle that steers the rear wheels has been put into practical use (the following [Patent Document 1]).
JP 2003-226127 A

  In the device described in [Patent Document 1], when the steering angle detection means of the rear wheel becomes abnormal, the rear wheel is driven back to the neutral position. In this case, since the steer characteristic is set on the assumption that the rear wheel is steered in a four-wheel steered vehicle, the vehicle tends to oversteer when the rear wheel is fixed at the neutral position (due to abnormal four-wheel steering) , Because the rear wheels are not steered in the same phase as the front wheels). As a result, the phase advance of the steering torque with respect to the steering angle of the steering wheel is reduced, and the feeling of response during steering is reduced. Accordingly, an object of the present invention is to provide a vehicle steering control device that can stabilize the operability even when the rear wheel steering of the four-wheel steering is abnormal.

  The vehicle steering control device according to claim 1 is a front wheel steering unit that performs a steering operation to steer a front wheel of a vehicle, and a steering assist control unit that applies a steering assist force and a steering damping force during a steering operation of the front wheel steering unit. And a rear wheel steering control means for steering the rear wheels of the vehicle, and a neutral direction steering means for steering the rear wheels in a neutral direction when an abnormality is detected in the rear wheel steering control means. The assist control means is characterized by increasing the damping coefficient of the steering damping force when the neutral direction turning means attempts to turn the rear wheel in the neutral direction.

  According to a second aspect of the present invention, in the vehicle steering control device according to the first aspect, when the steering assist control means does not return the rear wheel to the neutral position by the neutral direction steering means, the neutral position The greater the deviation from, the larger the attenuation coefficient.

  According to the vehicle steering control device of the first aspect, when an abnormality occurs in the rear wheel steering in the four-wheel steering vehicle, the rear wheel is returned to the neutral direction and the oversteer tendency (the phase of the steering torque with respect to the steering angle) By increasing the steering damping coefficient (steering force), the phase advance of the steering torque with respect to the steering angle is increased, and the feeling of steering response is improved.

  According to the vehicle steering control device of the second aspect, the greater the deviation from the neutral position, the greater the damping coefficient (damping force), the greater the feeling of responsiveness, and the steering feeling becomes more solid. To improve. The larger the deviation from the neutral position is, the larger the attenuation coefficient is. The change in the attenuation coefficient (damping force) with respect to the deviation amount may be increased linearly or exponentially. It may be increased in a saturation curve or stepwise.

  Hereinafter, an embodiment of a vehicle steering control device of the present invention will be described with reference to the drawings. In FIG. 1, the vehicle block diagram which mounts the vehicle steering control apparatus of this embodiment is shown. The vehicle 1 includes four wheels FR, FL, RR, and RL. The front wheels FR and FL are normal steered wheels, and the steering gear box 2 and the hub carrier 3 of each front wheel FR and FL are connected. A rack bar 2a is built in the gear box 2, and both ends of the rack bar 2a are connected to the hub carrier 3 described above via tie rods 2b.

  A steering shaft 4 in a steering column (not shown) is inserted into the gear box 2. A pinion gear at the front end of the steering shaft 4 meshes with the rack of the rack bar 2a to constitute a so-called rack and pinion 2c. A steering wheel 5 is attached to the other end of the steering shaft 4. In addition, a steering angle sensor 6 that detects a rotation angle (steering angle) of the steering shaft 4 and a steering torque sensor 7 that detects torque applied to the steering shaft 4 are also attached to the steering shaft 4.

  The electric power steering mechanism of the present embodiment includes a motor 8 that applies a rotational force to the steering shaft 4. By controlling the control amount of the motor 8, the power steering assist force or the steering system Damping torque can be added to attenuate the vibration of the. The steering gear box 2 also includes a stroke sensor 2d that detects the stroke amount (front wheel steering angle) of the rack bar 2a.

  Further, the vehicle 1 of the present embodiment is a four-wheel steering vehicle in which the rear wheels RR and RL are also steered. The steering amount of the rear wheels RR and RL is not as large as that of the front wheels FR and FL, and the steering of the rear wheels RR and RL is performed for the purpose of improving the maneuverability by the yaw control rather than the control of the vehicle traveling direction . For this reason, the gear box 9 is also connected to the hub carrier 3 of the rear wheels RR and RL. A shaft 9a is built in the gear box 9, and both ends of the shaft 9a are connected to the hub carrier 3 described above via tie rods 9b.

  The gear box 9 incorporates an actuator 10 that slides the shaft 9a. By driving the actuator 10, the shaft 9a can be slid in the axial direction, and as a result, the rear wheels RR and RL can be steered. The gear box 9 also has a built-in stroke sensor 9d that detects the stroke amount (rear wheel steering angle) of the shaft 9a.

  Further, the gear box 9 also incorporates a neutral position return mechanism 11 for returning the position of the shaft 9a to the neutral position. The neutral position return mechanism 11 returns the steered position of the rear wheels RR and RL to the neutral position when there is an abnormality in the rear wheel steering mechanism. Various mechanisms can be considered as the neutral position return mechanism 11. For example, the actuator 10 can be driven in the event of an abnormality such as when the rear wheel turning angle cannot be detected due to the abnormality of the stroke sensor 9d described above. Therefore, the actuator 10 is driven so that the rear wheels RR and RL are It can be returned to the neutral position.

  Alternatively, if a spring or the like that applies a force is applied so as to always return the rear wheels RR and RL to the neutral position and the actuator 10 cannot be driven due to disconnection of the actuator 10 or the like, The rear wheels RR and RL can be returned to the neutral position using force. In addition to the actuator 10, an actuator for returning to the neutral position may be incorporated.

  Further, a wheel speed sensor 12 is attached to each wheel FR, FL, RR, RL. The sensors 2d, 6, 7, 12 and the actuators 8, 10 described above are connected to an ECU 13 that controls the vehicle behavior in an integrated manner. The ECU 13 is an electronic control unit including a CPU, a ROM, a RAM, an input / output unit, and the like. The ECU 13 receives the output from each sensor and sends a control signal to each actuator. The ECU 13 can also diagnose the state of each actuator and sensor from the control signals of each actuator and sensor (for example, the actuator 10, the motor 8, and the stroke sensors 2d and 9d). Whether or not] can be determined).

  The power steering mechanism will be briefly described. The power steering mechanism applies the assist torque for reducing the steering operation force of the driver to the steering system by the motor 8, but the motor 8 also has a role of applying a damping torque for reducing the steering vibration. Here, the assist torque amount is calculated based on the steering torque detected by the steering torque sensor 7 and the vehicle speed detected by the wheel speed sensor 12.

  At the same time, a damping torque amount for attenuating steering vibration is calculated based on the steering angular velocity and the vehicle speed of the steering wheel 5 detected by the steering angle sensor 6. The attenuation coefficient at this time is Cst. Further, as described above, when the active stabilizer 9 is in failure (during failure), the attenuation coefficient is increased, and the correction coefficient therefor is set to Ksc (Cst ← Cst × Ksc). If Ksc = 1, no correction is performed. The torque output from the motor 8 is the sum of the assist torque and the damping torque.

  Next, an embodiment of steering attenuation control by the above-described apparatus will be described. A flowchart of this control is shown in FIG. As shown in FIG. 2, it is first determined whether or not the rear wheel steering mechanism is in an abnormal state (fail) due to an abnormality (step 200). The abnormality of the rear wheel steering mechanism includes the inability to detect the rear wheel turning angle due to the abnormality of the stroke sensor 9d described above, the failure of the actuator 10, and the like. When the rear wheel steering mechanism has not failed, Ksc = 1 is set (step 205), Cst = Cst × Ksc (step 210), and the steering damping torque amount calculated based on the steering angular speed and the vehicle speed is not corrected. (The attenuation coefficient Cst is not corrected).

  On the other hand, if step 200 is affirmed, control is performed to return the steered position of the rear wheels RR and RL to the neutral position by the neutral position return mechanism 11 described above (step 215). After step 215, it is determined whether or not the steered position of the rear wheels RR and RL is in a fixed state without returning to the neutral position (step 220). If step 220 is negative and the steered position of the rear wheels RR and RL has been returned to the neutral position, Ksc = Kscf (> 1) is set (step 225), and Cst = Cst × Ksc (step 215). ), The amount of steering damping torque calculated based on the steering angular velocity and the vehicle speed is corrected (the damping coefficient Cst is increased). Kscf is a correction coefficient when the rear wheel steering mechanism fails.

  As described above, when the rear wheel steering mechanism fails and rear wheel steering (in-phase steering) is not performed, the behavior of the vehicle tends to be oversteered (the phase of the steering torque with respect to the steering angle tends to be delayed). Therefore, by increasing the steering damping coefficient Cst (steering force), the phase advance of the steering torque with respect to the steering angle is increased, the feeling of steering response is improved, and the operability is improved.

  On the other hand, if step 220 is negative, that is, if the rear wheel steering mechanism fails and the rear wheels RR and RL cannot be returned to the neutral position, Ksc = αr × Kscf is set (step 230). Kscf is a correction coefficient larger than 1 described above. αr is a second correction coefficient determined according to the rear wheel turning angle in the fixed state. This correction coefficient also takes a value larger than 1, and takes a larger value as the rear wheel fixed turning angle increases.

  After step 230, the steering damping torque amount is corrected by Cst = Cst × Ksc (step 215) (the damping coefficient Cst is increased: further increased than when the rear wheels RR and RL are returned to the neutral position). ) By doing so, an oversteer tendency (the tendency of the steering torque phase to be delayed with respect to the steering angle) when the rear wheel steering mechanism fails is canceled to increase the feeling of response (effect of Kscf), and further, steering damping. Increase the torque to increase the feeling of responsiveness, improve the steering feeling by making the steering feeling more firm (effect of αr).

  The present invention is not limited to the embodiment described above. For example, in the above-described embodiment, the assist torque of the power steering generated by the actuator (motor 8) and the damping torque for damping the steering vibration are applied to the steering shaft 4. However, a system in which an actuator that generates assist torque or damping torque is attached to the steering gear box 2 and controls the sliding movement (sliding amount) of the rack bar 2a may be used.

It is a vehicle block diagram carrying one Embodiment of the vehicle steering control apparatus of this invention. It is a flowchart of steering damping torque correction control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Steering gear box (front wheel steering means), 2a ... Rack bar, 2b ... Tie rod, 2c ... Rack and pinion, 2d ... Stroke sensor, 3 ... Hub carrier, 4 ... Steering shaft (front wheel steering means), DESCRIPTION OF SYMBOLS 5 ... Steering wheel (front wheel steering means), 6 ... Steering angle sensor, 7 ... Steering torque sensor, 8 ... Motor (steering assist control means), 9 ... Gear box (rear wheel steering control means), 10 ... Actuator (rear wheel rotation) (Steering control means), 11 ... rear wheel neutral position return mechanism (neutral direction steering means), 12 ... wheel speed sensor, 13 ... ECU (steering assist control means, neutral direction steering means).

Claims (2)

Front wheel steering means for steering operation to steer the front wheels of the vehicle;
Steering assist control means for applying a steering assist force and a steering damping force during a steering operation of the front wheel steering means;
Rear wheel steering control means for steering the rear wheels of the vehicle;
In a vehicle steering control device comprising neutral direction steering means for steering the rear wheel in a neutral direction when an abnormality is detected in the rear wheel steering control means,
The steering assist control means increases the damping coefficient of the steering damping force when the neutral direction turning means attempts to turn the rear wheel in the neutral direction. apparatus. The steering assist control means sets the damping coefficient larger as the deviation from the neutral position is larger when the rear wheel is not returned to the neutral position by the neutral direction steering means. Item 2. The vehicle steering control device according to Item 1.

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