JP5043804B2 - Vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle behavior control device attaining smooth steering control even when a wheel rides up a bump of a road surface. <P>SOLUTION: ECU 20 determines whether or not a difference &Delta;&delta;rl of a rear wheel target steering angle &delta;rlt and a rear wheel actual steering angle &delta;rlr exceeds an abnormality determination threshold value &delta;th in a step S2. When the left rear wheel 3rl rides up the bump or the like, a rear wheel steering actuator 8l generates failure of operation and the determination of the step S2 becomes Yes, the ECU 20 determines whether or not unsprung acceleration Gwl inputted from a unsprung G sensor 18 exceeds an acceleration determination threshold value Gwth in a step S3. When the determination is Yes, it outputs ground-contact load reduction instruction to an attenuation force correction part 32 of an attenuation force control part 22 in a step S4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a vehicle behavior control device mounted on a four-wheeled vehicle having a steering control means and a ground load increase / decrease means, and more specifically, realizes smooth steering control even when a wheel rides on a bump on a road surface. Related to technology.

  In recent years, instead of the traditional front-wheel-steered vehicle in which only the front wheels are steered according to the operation of the steering wheel, the front and rear wheels have been improved in order to improve steering stability during high-speed driving and reduce the turning radius during parking. Various four-wheel steering vehicles have been developed (see Patent Documents 1 and 2). As a four-wheel steering vehicle, for example, based on a rear wheel steering ratio characteristic in which a ratio of a rear wheel rudder angle (rear wheel toe angle) to a front wheel rudder angle is set in advance to be in reverse phase at low speed and in phase at high speed, In general, the vehicle is provided with a rear wheel steering control device that drives and controls the rear wheel steering actuator.

On the other hand, various types of cylindrical dampers that make up suspensions for automobiles have variable damping force types that can variably control the damping force according to the state of motion of the automobile, etc., in order to achieve both high handling stability and ride comfort. It has been developed (see Patent Document 3). In recent automobiles, active suspensions have appeared that use air springs as suspension springs and perform active control based on the Skyhook theory (see Patent Document 4). In the damping force variable damper and the active suspension, the ground contact load of the wheel can be changed by increasing / decreasing the damping force or increasing / decreasing the air pressure.
Japanese Patent Publication No. 5-33193 JP-A-7-33036 JP 2006-273223 A JP 2004-149046 A

  The rear wheel steering control device for a four-wheel steering vehicle sets the target rudder angle of the left and right rear wheels based on various control parameters (front wheel rudder angle, vehicle speed, target yaw rate, etc.), and then matches the actual rudder angle to the target rudder angle. In this manner, the rear wheel steering actuator is driven and controlled. However, when one of the left and right rear wheels rides on a bump on the road surface while steering control of the rear wheel is being performed, the ground load (that is, steering resistance) of the wheel increases, and the rear wheel steering actuator temporarily Could become inoperable. Then, there is a concern that the yaw rate may increase or decrease instantaneously due to the difference between the actual rudder angle and the target rudder angle, resulting in a decrease in running stability.

  The present invention has been made in view of such a background, and provides a vehicle behavior control device for realizing smooth steering control even when a wheel rides on a bump on a road surface.

The first invention is mounted on a four-wheel vehicle, and steering control means for steering control of at least one of the left and right front wheels and the left and right rear wheels; unsprung acceleration detection means for detecting or estimating unsprung acceleration of the wheels; a vehicle behavior control device having a grounding load adjusting unit for changing the vertical load of the wheel, the wheel by the steering control means is steering control, the difference between the target steering angle and the actual steering angle of the wheel is abnormal determination Load reduction command output means for outputting a load reduction command for reducing the ground load of the wheel to the ground load increase / decrease means when the unsprung acceleration of the wheel exceeds the acceleration determination threshold when the threshold is exceeded. It is characterized by.

According to a second aspect of the present invention, in the vehicle behavior control device according to the first aspect, the ground load increasing / decreasing means includes a damping force variable damper .

According to the first invention, even when the wheel rides on a bump or the like and the steering resistance increases, the ground contact load of the wheel decreases, thereby realizing a smooth operation of the steering actuator, and the target rudder angle and the actual rudder angle. The difference is less likely to occur. Further, since it can be determined whether or not the external force is generated by the vertical movement of the wheel, erroneous control due to a mechanical failure or the like of the steering actuator is suppressed. Further, according to the second invention, for example, when the one using a magnetorheological fluid is adopted, the contact load can be instantaneously reduced, and therefore, the decrease in running stability can be effectively suppressed.

  Hereinafter, an embodiment in which the present invention is applied to a four-wheel steering vehicle will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a four-wheel steering vehicle according to the embodiment, and FIG. 2 is a block diagram showing a main part of the ECU according to the embodiment.

<< Configuration of Embodiment >>
<Schematic configuration of automobile>
First, a schematic configuration of a four-wheel steered automobile (hereinafter simply referred to as an automobile) according to an embodiment will be described with reference to FIG. In the description, for the four wheels and members disposed therewith, that is, tires, suspensions, and the like, subscripts indicating front, rear, left, and right are attached to the numerals, respectively, for example, left front wheel 3fl, right front wheel 3fr. The left rear wheel 3 rl and the right rear wheel 3 rr are referred to as “wheel 3”.

  As shown in FIG. 1, a vehicle body 1 of an automobile (vehicle) V is provided with wheels 3 with tires 2 mounted on the front, rear, left and right thereof. These wheels 3 are suspension arms, springs, damping force variable dampers (hereinafter referred to as dampers). It is suspended on the vehicle body 1 by a suspension 5 consisting of 4). The vehicle V includes an ECU (Electronic) that drives and controls the left and right rear wheel steering mechanisms 6l and 6r used for steering the left and right rear wheels 3rl and 3rr, the dampers 4fl to 4rr, the rear wheel steering mechanisms 6l and 6r, and the like. Control Unit: Electronic Control Unit) 20 is installed.

  The damper 4 is a telescopic type using MRF (Magneto-Rheological Fluid) as a working fluid, and the ECU 20 controls the supply current to the magnetic fluid valve incorporated in the piston, so that the damping force is not present. Change in steps and instantly. The rear wheel steering mechanism 6 includes a direct-acting rear wheel steering actuator 8 interposed between the vehicle body 1 and the rear wheel side knuckle 7. The ECU 20 supplies current to the rear wheel steering actuator 8. By controlling the left and right rear wheels 3rl and 3rr independently.

  In the automobile V, a steering angle sensor 10 that detects a steering angle of a steering wheel, a vehicle speed sensor 11 that detects a vehicle speed, a lateral G sensor 12 that detects lateral acceleration, a longitudinal G sensor 13 that detects longitudinal acceleration, and a yaw rate are detected. A yaw rate sensor 14 and the like are installed at appropriate positions of the vehicle body 1, and a vertical G sensor (vertical momentum detecting means) 15 for detecting vertical acceleration near the wheel house and a stroke sensor 16 for detecting the stroke speed of the damper 4 are provided. Each wheel 3 is installed. Further, the rear wheel steering actuator 8 is provided with a position sensor (linear encoder) 17 for detecting the operation amount (that is, the actual steering angle of the left and right rear wheels 3rl, 3rr). The rear wheel knuckle 7 is provided with an unsprung G sensor 18 for detecting the vertical acceleration (unsprung acceleration) of the left and right rear wheels 3rl, 3rr.

<Schematic configuration of ECU>
The ECU 20 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and via a communication line (CAN (Controller Area Network in this embodiment)) as shown in FIG. The sensors 10 to 18, the damper 4, the rear wheel steering mechanism 8 and the like are connected. As shown in FIG. 2, the ECU 20 performs steering control of the rear wheel steering actuator 8, the input interface 21 to which the detection signals of the sensors 10 to 18 are input, the damping force control unit 22 that controls the damping force of the damper 4. The rear wheel steering control unit 23, the damping force control unit 22, and the output interface 24 used for output of drive current from the rear wheel steering control unit 23 are provided.

(Damping force control unit)
The damping force control unit 22 is based on the target damping force setting unit 31 that sets the target damping force of each of the dampers 4fl to 4rr based on the detection signals of the sensors 10 to 15 and the load reduction command input from the rear wheel steering control unit 23. A damping force correction unit 32 that corrects the target damping force of the rear wheel side dampers 4rl and rr, and a driving current output unit 33 that outputs a driving current of the damper 4 based on the target damping force and the stroke speed are provided.

(Rear wheel steering control unit)
The rear wheel steering control unit 23 is a target rudder angle setting unit 41 that sets a rear wheel target rudder angle based on detection signals from the steering angle sensor 10 and the yaw rate sensor 14. A target drive amount setting unit 42 that sets a target drive amount of the rear wheel steering actuator 8 based on the difference from the actual steering angle, a drive current output unit 43 that outputs a drive current of the rear wheel steering actuator 8 based on the target drive amount, A load reduction command output unit 44 that outputs a load reduction command based on the wheel target rudder angle, the rear wheel actual rudder angle, and the unsprung acceleration input from the unsprung G sensor 18 is provided.

<< Operation of Embodiment >>
<Normal control>
When the vehicle V starts driving, the ECU 20 executes the damping force control and the rear wheel steering control with a predetermined control interval (for example, 2 ms).

(Damping force control)
In the damping force control, the ECU 20 determines the motion state of the vehicle V based on the detection signals of the sensors 10 to 15 and then determines the skyhook control value, the roll control value, and the pitch control value for each wheel 3 from the determination result. Calculate each. Next, the ECU 20 selects a target damping force having the same sign as the stroke speed direction of the damper 4 and the largest absolute value from these three control values, and then selects a target damping force based on the target damping force and the stroke speed. A target current is set from the current map and output to each damper 4.

(Rear wheel steering control)
On the other hand, in the rear wheel steering control, the ECU 20 retrieves the target rudder angle (rear wheel target rudder angle) of the left and right rear wheels 3rl and 3rr from the target rudder angle map based on detection signals of the steering angle sensor 10 and the yaw rate sensor 14. The target drive amount of the rear wheel steering actuator 8 is set from the difference between the rear wheel target rudder angle and the actual rudder angle input from the position sensor 17 and is output to both rear wheel steering actuators 8.

<Ground load reduction control>
Next, with reference to a flowchart, the ground load reduction control according to the present embodiment will be described. The contact load reduction control is performed on the left and right rear wheels 3rl and 3rr in exactly the same procedure, but only the left rear wheel 3rl is referred to in order to prevent the explanation from becoming complicated.

  In parallel with the above-described damping force control and rear wheel steering control, the ECU 20 executes ground load reduction control whose procedure is shown in the flowchart of FIG. When the ground load reduction control is started, the ECU 20 determines whether or not a rear wheel steering command is output in step S1 of FIG. 3 (whether or not a driving current is output to the rear wheel steering actuator 8l). If No, return to the start without performing any processing.

  When the vehicle V performs turning or slalom traveling and a rear wheel steering command is output, the determination in step S1 is Yes, so that the ECU 20 determines the rear wheel target rudder angle δrlt and the actual rear wheel rudder angle δrrr in step S2. It is determined whether or not the difference Δδrl exceeds the abnormality determination threshold value δth. If this determination is No, the process returns to the start without performing any processing.

  When the left rear wheel 3rl rides on a bump or the like and the rear wheel steering actuator 8l malfunctions due to an increase in steering resistance and the determination in step S2 becomes Yes, the ECU 20 receives the spring input from the unsprung G sensor 18 in step S3. It is determined whether or not the lower acceleration Gwl has exceeded the acceleration determination threshold Gwth (that is, whether or not the cause of the increase in Δδrl is a bump or the like), and if this determination is No, no processing is performed. Return to start. This is because, when the mechanical failure of the rear wheel steering actuator 8l is the cause, there is no effect even if the ground load of the left rear wheel 3rl is reduced, and conversely, the vehicle posture may be deteriorated.

  If the determination in step S3 is also Yes, the ECU 20 outputs a ground load reduction command to the damping force correction unit 32 of the damping force control unit 22 in step S4. The ground load reduction command may be, for example, to uniformly reduce the target damping force to 1/10, or according to the difference Δδrl between the rear wheel target rudder angle δrlt and the actual rear wheel rudder angle δrlr from the correction gain map. A correction gain may be set. As a result, the damping force of the damper 4 instantaneously decreases upon the ride on the bump or the like, the ground load on the left rear wheel 3rl decreases rapidly, and the rear wheel steering actuator 8l is likely to operate normally. As a result, the yaw rate does not easily increase or decrease due to the difference between the rear wheel target rudder angle δrlt and the actual rear wheel rudder angle δrlr, and extremely stable traveling is possible even on an irregular road.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, although the above embodiment is an application of the present invention to a vehicle equipped with a variable damping force damper, it can also be applied to a vehicle equipped with an active control type air suspension, hydropneumatic suspension, etc. as a ground load increasing / decreasing means. It is. In the above embodiment, the rear wheel steering control has been described. However, the present invention can also be applied to the front wheel steering control if a steer-by-wire device, a variable gear ratio steering device, or the like is provided. In the above-described embodiment, the unsprung G sensor is used as the unsprung acceleration detecting means. However, the unsprung G sensor may be estimated by a method such as differentiating the stroke speed of the damper. In addition, as long as it does not deviate from the gist of the present invention, the specific configuration of the automobile and the control device, the specific procedure of control, and the like can be appropriately changed.

1 is a schematic configuration diagram of a four-wheeled vehicle according to an embodiment. It is a block diagram which shows the principal part of ECU which concerns on embodiment. It is a flowchart which shows the procedure of the ground load reduction control which concerns on embodiment.

Explanation of symbols

3 Wheel 4 Damping Force Variable Damper 6 Rear Wheel Steering Mechanism 8 Rear Wheel Steering Actuator 18 Unsprung G Sensor (Unsprung Acceleration Detection Means)
20 ECU
22 Damping force control unit (ground load increasing / decreasing means)
23 Rear wheel steering control unit (steering control means)
44 Load reduction command output section (load reduction command output means)
V 4-wheel steering car (4-wheel vehicle)

Claims (2)

A steering control means mounted on a four-wheel vehicle for steering control of at least one of the left and right front wheels and the left and right rear wheels, an unsprung acceleration detection means for detecting or estimating unsprung acceleration of the wheel, and a ground load of the wheel. A vehicle behavior control device having a ground load increasing / decreasing means for changing,
When the wheel is steered by the steering control means, the difference between the target rudder angle of the wheel and the actual rudder angle exceeds the abnormality determination threshold value, and the unsprung acceleration of the wheel exceeds the acceleration determination threshold value , the ground contact A vehicle behavior control device comprising a load reduction command output means for outputting a load reduction command for reducing the ground contact load of the wheel to the load increasing / decreasing means. The vehicle behavior control device according to claim 1, wherein the ground load increasing / decreasing means includes a damping force variable damper .

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