JP2010234819A - Vehicle rear wheel steering control device - Google Patents

Abstract

Provided is a control device for steering a rear wheel so that a vehicle moves straight when the vehicle is held in a roll-inclined state due to a control failure of an active suspension device.
A rear wheel steering control device for steering and controlling left and right rear wheels of a vehicle provided with an active suspension device for driving a suspension 7 for suspending a wheel on a vehicle body by an actuator. This apparatus includes state quantity detection means 17, 18, and 19 for detecting the movement state quantity of the vehicle. Then, when the vehicle is held in the state of tilting in the roll direction due to the control failure of the active suspension device, the roll angle is calculated based on the detected amount of motion state, and the vehicle goes straight according to the roll angle. Thus, the rear wheels are configured to be steered.
[Selection] Figure 2

Description

  The present invention relates to a rear-wheel steering control device for an automobile (hereinafter simply referred to as a vehicle) having an active suspension, and more specifically, the vehicle is held in a state of being inclined in the roll direction due to a control failure of the active suspension device. The present invention relates to a control device that steers a rear wheel so that a vehicle sometimes goes straight.

  2. Description of the Related Art There is known an active suspension device that controls the vehicle height and the support load of each wheel by changing the characteristics and stroke amount of the suspension device that suspends the wheel on the vehicle body (see Patent Documents 1 and 2). In addition, a technique for stabilizing the traveling state of the vehicle by providing a rear wheel steering device that steers the turning angle of the left and right rear wheels based on the vehicle state quantity such as the yaw rate when the vehicle turns is disclosed. (See Patent Document 3).

JP 2008-7033 A JP 2007-246058 A JP 2006-69497 A

  The technique disclosed in Patent Document 1 or Patent Document 3 is suitable for the driver who is driving when the vehicle is turning and traveling because the vehicle behavior intended by the driver can be realized. Further, as disclosed in Patent Document 2, in a vehicle equipped with an active suspension device, a mechanical type is usually used so that a minimum maneuverability can be ensured even when an actuator or an electronic control unit fails. The weight of the vehicle body is supported by the spring means, and the frictional force of the actuator is set to act as a damping force.

  However, if control is not applied to the active suspension device, the damping force of the damper will be minimum, so depending on the situation of control failure, the vehicle body may remain tilted in the roll direction, and the occupant steered the normal front wheels There was a risk that the vehicle would not be able to go straight ahead alone.

  The present invention has been made in view of the above background, and provides a control device for steering a rear wheel so that a vehicle travels straight when the vehicle is held in a tilted state in the roll direction due to a control failure of an active suspension device. The purpose is to provide.

  The present invention is a rear-wheel steering control device for steering-controlling the left and right rear wheels of a vehicle provided with an active suspension device that drives with an actuator a suspension that suspends wheels on a vehicle body. This apparatus includes a state quantity detection means for detecting the movement state quantity of the vehicle. Then, when the vehicle is held in a state tilted in the roll direction due to a control failure of the active suspension device, a roll angle is calculated based on the detected motion state quantity, and the vehicle is determined according to the roll angle. The rear wheels are steered so that the vehicle goes straight.

  According to the above configuration, if the roll control amount of the active suspension device, for example, the target sinking amount is compared with the detected actual stroke amount, it is determined that the vehicle is held in a state inclined in the roll direction. Both the rear wheels or the left and right rear wheels can be individually steered so as to cancel this inclination. The occupant can drive the vehicle straight by performing normal front wheel steering.

  In the above configuration, the state quantity detection means detects a stroke amount of the suspension, and determines a toe angle of the rear wheel according to the detected stroke amount based on a relationship between a preset stroke amount and a toe angle. The rear wheel camber angle can be set in accordance with the detected stroke amount based on the relationship between the stroke amount and the camber angle that are set or set in advance.

  Further, the present invention calculates a contribution ratio of the ground load of each of the left and right front and rear wheels based on the detected ground load of all the wheels of the vehicle, and calculates a correction amount of the contribution ratio so that the vehicle goes straight. The rear wheels may be steered so that the corrected contribution rate is obtained.

  When the active suspension device fails to control, the ground loads on the left and right front and rear wheels change. When the vehicle is tilted in the roll direction, the ground load between the left wheel and the right wheel is unbalanced when traveling straight. Therefore, according to the above configuration, the rear wheel is steered in a direction to cancel the unbalance according to the contribution ratio of the ground load of the left and right front and rear wheels, thereby balancing the ground load between the left wheel and the right wheel. The vehicle can go straight. However, since such rear wheel steering control is a fail-safe measure in the event of active suspension control failure, subsequent repair of the active suspension is required.

  According to the present invention, it is possible to provide a control device that steers the rear wheels so that the vehicle travels straight when the vehicle is held in a state tilted in the roll direction due to a control failure of the active suspension device.

1 is a schematic configuration diagram of a four-wheeled vehicle according to a first embodiment of the present invention. It is a functional block diagram which shows schematic structure of the principal part of the control apparatus concerning 1st Embodiment of this invention. It is an example of the map showing the relationship between the stroke amount concerning 1st Embodiment of this invention, and a toe angle. It is a functional block diagram which shows schematic structure of the control apparatus concerning 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, a first 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. These suspensions are active suspensions whose characteristics can be controlled or whose sinking amount can be controlled. The active means for changing the vehicle height or the supporting load with respect to the vehicle body can be configured to be incorporated into the shock absorber or the suspension spring in various known manners as disclosed in Patent Document 1.

  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. 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, a vehicle speed sensor 13, a front wheel steering angle sensor 14, a yaw rate sensor 15, a lateral acceleration sensor 16, and a stroke sensor as an observation amount related to active suspension. In addition to 18R, 18L, 19R, 19L, and load sensors 20R, 20L, 21R, 21L, various sensors (not shown) are installed, and detection signals from the sensors are input to the ECU 12 for vehicle control. The steering angle sensor 14 detects the steering amount of the steering wheel 8, and the turning angle of the front wheels 3 is calculated from the detected value. The lateral acceleration sensor 16 detects acceleration acting in the left-right direction of the vehicle. The stroke sensors 18 and 19 detect the vehicle height by detecting the amount of expansion and contraction, and the load sensors 20 and 21 detect the support load on the suspension. 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. In FIG. 1, the stroke sensors 18 and 19 and the load sensors 20 and 21 are shown as one sensor, but this is for avoiding complexity in the drawing.

  The ECU 12 includes a microcomputer, ROM, RAM, peripheral circuit, input / output interface, various drivers, and the like, and is connected to the sensors 13 to 21 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 21 and the like, determines the displacement amount of each actuator 11L, 11R, and executes the toe angle control of the rear wheel 5. Further, the ECU 12 calculates a roll control amount (for example, a target sinking amount), and executes roll control of the front suspensions 6L and 6R and the rear suspensions 7L and 7R, which are active suspensions.

  The actuators 11L and 11R are respectively provided with toe angle sensors 17L and 17R that acquire a toe angle by 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.

  FIG. 2 is a functional block diagram of a main part of the vehicle control device in the present embodiment. The rear wheel steering control 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.

  FIG. 2 shows a main part according to the present embodiment. For example, an instruction toe angle calculation means for setting a target toe angle of the left and right rear wheels of a vehicle disclosed in Patent Document 3, and a behavior of the vehicle And a rear wheel toe angle control device that changes a toe angle of the left and right rear wheels of the vehicle based on a deviation between the target toe angle and the detected actual toe angle. Description of the general configuration of may be omitted.

  Referring to FIG. 2, the active suspension failure diagnosis unit 120 of the ECU 12 includes, for example, stroke sensors 18 and 19 provided on the front suspension 6 and the rear suspension 7 that are active suspensions via an input interface (not shown). Get the signal and the signal of the operation amount of the active suspension. The active suspension failure diagnosis unit 120 compares both to diagnose whether or not the control related to the active suspension is abnormal.

  When it is diagnosed that the active suspension is in control failure, the active suspension failure diagnosis unit 120 sends a signal to that effect to the instruction toe angle correction unit 121. The command toe angle correction unit 121 acquires signals from the stroke sensors 18 and 19 and sets a command toe angle corresponding to the stroke expansion / contraction amount that determines the roll angle so that the vehicle travels straight. In setting the instruction toe angle, a map representing a relationship between a preset stroke amount and a toe angle as shown in FIG. 3 can be stored in the memory of the ECU 12 and can be referred to. As described above, in the present embodiment, the roll angle is determined based on the stroke amount which is one of the vehicle state quantities and the rear wheel toe angle control amount is calculated, but the roll angle is calculated from the stroke amount. The relationship between the calculated roll angle and toe angle can also be used as a map.

  Normally, the ECU 12 acquires or calculates or estimates the vehicle state amount from the vehicle speed sensor 13, the front wheel steering angle sensor 14, the yaw rate sensor 15, the lateral acceleration sensor 16, the in-cylinder pressure sensor (not shown), or the like. The driving force of the left and right rear wheels 5L and 5R is estimated based on the engine torque, the transmission gear ratio, and the like, and the instruction toe angle is set from the estimation result of the rear wheel driving force and the detection result of the lateral acceleration sensor 16. ing.

  However, in this embodiment, the rear wheel steering control is performed so that the vehicle goes straight when the vehicle is held in a state of tilting in the roll direction due to the control failure of the active suspension, and the normal control is stopped. The instruction toe angle set by the instruction toe angle correcting unit 121 is prioritized.

  Next, the ECU 12 subtracts the actual toe angle detected by the toe angle sensor 17 disposed in the actuator 11 from the indicated toe angle and sent to the ECU 12 via an input interface (not shown), and the deviation e. Is calculated. The deviation e is input to the FB controller 122, and the FB controller 122 generates a drive signal for driving the actuator 11 in a direction to eliminate the deviation via an output interface (not shown).

  According to the configuration of the first embodiment, when the roll control amount of the active suspension device, for example, the target sinking amount is compared with the detected actual stroke amount, the vehicle is held in a state inclined in the roll direction. If judged, both the rear wheels or the left and right rear wheels can be individually steered so as to cancel this inclination. The occupant can drive the vehicle straight by performing normal front wheel steering.

  In the first embodiment, the configuration has been described in which the stroke amount of the suspension is detected and the toe angle of the rear wheel is set according to the detected stroke amount based on the relationship between the preset stroke amount and the toe angle. Such control is not limited to the toe angle, and can also be achieved by correcting the camber angle. That is, based on the relationship between the preset stroke amount and the camber angle, a map similar to that in FIG. 3 is stored in the memory of the ECU 12, and the rear wheel camber angle is set according to the detected stroke amount. You can also However, since such rear wheel steering control is a fail-safe measure in the event of active suspension control failure, subsequent repair of the active suspension is required.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a functional block diagram showing a schematic configuration of the control device according to the present embodiment. In addition, description may be abbreviate | omitted about the structure which is common in above-described 1st Embodiment.

  Referring to FIG. 4, when it is diagnosed that the active suspension is in a control failure, the active suspension failure diagnosis unit 120 executes a similar process until a signal to that effect is sent to the instruction toe angle correction unit 121.

  When the instruction toe angle correction unit 121 receives a signal indicating that the active suspension is in control failure, the instruction toe angle correction unit 121 acquires a load signal of the left and right front and rear wheels detected by the load sensors 20 and 21. The vehicle is tilted in the roll direction due to the control failure of the active suspension, and the center of gravity of the vehicle traveling straight is decentered to the right or left. The command toe angle correcting unit 121 calculates a contribution rate to each wheel from the detected ground load.

If the vehicle body is tilted in the roll direction, the load increases on one of the front and rear wheels, and the load decreases on the other. This is generally called a load movement amount by a roll. It is known that the roll angles θrf and θrr of the front wheels and the rear wheels can be calculated as follows.
θrf = (ΔWf · Df−Gy · Ws · Lr · Hf / L) / Kf (1)
θrr = (ΔWr · Dr−Gy · Ws · Lf · Hr / L) / Kr (2)

  Here, ΔWf is the moving load of the left and right front wheels, ΔWr is the moving load of the left and right rear wheels, Df is the distance between the left and right front wheels, Dr is the distance between the left and right rear wheels, Gy is the lateral acceleration, Ws is the weight of the vehicle, and Lf is The distance from the center of gravity of the vehicle to the front wheel axle, Lr is the distance from the center of gravity of the vehicle to the rear wheel axle, L is the distance between the front and rear axles, Hf is the height of the roll center from the ground on the front wheel axle, and Hr is on the rear axle. The roll center height from the ground, Kf is the roll rigidity on the front wheel side, and Kr is the roll rigidity on the rear wheel side. The roll center is the instantaneous center of the vehicle body in a plane including the ground contact points of the left and right wheels perpendicular to the longitudinal direction of the vehicle when the wheels are rigid in the vertical and horizontal directions and do not move at the ground contact points.

  The moving loads ΔWf and ΔWr are calculated from the calculated contribution ratio of the ground load to each wheel, the lateral acceleration Gy is acquired from the detected motion state quantity, and the roll is started from the state where the active suspension is fixed due to the roll control failure. Since the stiffnesses Kf and Kr are estimated and the others can be calculated from the specifications of the vehicle, the instruction toe angle correcting unit 121 can calculate the roll angles θrf and θrr by the equations (1) and (2).

  The command toe angle correcting unit 121 sets the command toe angle according to the stroke amount so that the vehicle travels straight according to the calculated roll angles θrf and θrr. In setting the instruction toe angle, a map representing the relationship between a preset roll angle and a toe angle can be stored in the memory of the ECU 12 and can be referred to. In this embodiment as well, the rear wheel camber angle can be set according to the calculated roll angle instead of the toe angle as in the first embodiment.

  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 (active suspension)
10 Rear wheel toe angle control device 11 Actuator 12 ECU
16 Lateral acceleration sensor 17 Toe angle sensor 18, 19 Stroke sensor (active suspension)
20, 21 Load sensor 120 Active suspension failure diagnosis unit 121 Rear wheel toe angle correction unit 122 FB controller

Claims (4)

A rear wheel steering control device for steering control of left and right rear wheels of a vehicle provided with an active suspension device for driving a suspension for suspending a wheel on a vehicle body by an actuator,
Comprising a state quantity detecting means for detecting a motion state quantity of the vehicle;
When the vehicle is kept tilted in the roll direction due to control failure of the active suspension device, a roll angle is calculated based on the detected amount of motion state, and the vehicle goes straight according to the roll angle. A rear-wheel steering control device that steers the rear wheels in such a manner. The state quantity detecting means detects a stroke amount of the suspension,
The rear wheel steering control device according to claim 1, wherein a toe angle of a rear wheel is set in accordance with the detected stroke amount based on a relationship between a preset stroke amount and a toe angle. The state quantity detecting means detects a stroke amount of the suspension,
2. The rear wheel steering control device according to claim 1, wherein a rear wheel camber angle is set according to the detected stroke amount based on a relationship between a predetermined stroke amount and a camber angle. 3. A rear wheel steering control device for steering control of left and right rear wheels of a vehicle provided with an active suspension device for driving a suspension for suspending a wheel on a vehicle body by an actuator,
Comprising a state quantity detecting means for detecting a motion state quantity of the vehicle;
When the vehicle is held in a roll-inclined state due to the control failure of the active suspension device, the contribution ratio of the contact load of each of the left and right front and rear wheels is calculated based on the detected contact load of all the wheels of the vehicle. Then, a correction amount of the contribution rate is calculated so that the vehicle goes straight, and a rear wheel is steered so that the corrected contribution rate is obtained.

Images