JP4382345B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus.
[0002]
[Prior art]
2. Description of the Related Art There is known a vehicle steering device called a steer-by-wire system (hereinafter referred to as an SBW device) configured such that a driver's operating device and a tire are interlocked by electrical coupling. In this SBW device, a target value of a tire turning angle is calculated based on an operation amount given by a driver to a steering wheel, a joystick, and the like, and a steering actuator such as an electric motor that drives a steering linkage is feedback-controlled according to the target value. Thus, the tire turning angle is controlled.
[0003]
In this SBW device, since the steering wheel and the tire are not mechanically connected, it is virtually impossible for the driver to directly feel the road surface reaction force applied to the tire from the steering wheel. For this reason, there is a concern that a driver who is accustomed to riding a conventional vehicle may feel a great sense of incongruity.
[0004]
As a method for dealing with such inconvenience, a pseudo reaction force torque is electrically driven according to the deviation between the rotation angle of the steering wheel and the tire turning angle, that is, the steady deviation generated between the target value and the actual value in feedback control. It is known to generate a reaction force actuator such as a motor and add it to the steering wheel to give a response to the driver (see Japanese Patent Publication No. 6-98931).
[0005]
On the other hand, the operation of these steering actuators and reaction force actuators is generally controlled by an electronic control device (hereinafter referred to as ECU) equipped with a CPU. A fail-safe system is required to avoid it (see Japanese Patent No. 3313979).
[0006]
As a fail-safe system, conventionally, a plurality of ECUs are usually provided, and the main ECU generally controls the whole, and the sub-ECU replaces the control function only when the main ECU breaks down. The ECU controls the steering actuator and the other ECU individually controls the reaction force actuator. If either of the functions is missing, the normal one takes over that function. Are known.
[0007]
[Patent Document 1]
Japanese Patent Publication No. 6-98931 [Patent Document 2]
Japanese Patent No. 3313979 [0008]
[Problems to be solved by the invention]
However, for example, in a conventional failure diagnosis system in which watchdog pulses (hereinafter referred to as WDP) generated by the main ECU and the sub ECU are monitored with each other, one of the ECUs may have failed due to WDP abnormality. However, since it cannot be determined whether the WDP abnormality is caused by a failure on the transmission side or a failure on the reception side, it is impossible to know which ECU has failed.
[0009]
Therefore, it is conceivable to prepare a third ECU for monitoring the states of the main ECU and the sub ECU, and to determine the ECU for performing malfunction compensation or identifying the malfunctioning ECU by mutual data communication between the three. However, according to this, since three or more ECUs or CPUs are required, it is inevitable that the manufacturing cost increases due to the complicated system configuration.
[0010]
The present invention has been devised to solve such problems of the prior art, and its main purpose is to perform more reliable fault diagnosis without complicating the system configuration. Another object is to provide a vehicle steering apparatus.
[0011]
[Means for Solving the Problems]
To achieve the above objects, the present onset Ming, a steering means operated by the driver (for example, the steering wheel 2), driving means for providing a steering angle to the tire (6) according to the operation amount of the steering means ( For example, an electric motor 10), a steering reaction force applying means (for example, an electric motor 4) for applying a reaction force against the operating force of the driver to the steering means, and an output instruction function for at least the driving means. In the vehicle steering apparatus having one control means (ECU21) and at least a second control means (ECU22) having an output instruction function for the steering reaction force applying means, the first control means and the second control each a unit with emitting the watchdog pulse, the watchdog pulses to detect the abnormality I monitoring if one another, the anti-lock brake mounted on the vehicle (ABS) control means provided in the device (ECU 23) is provided with a function to determine an abnormality of the first and second control means, one of said first control means and said second control means It is determined whether or not an abnormality has occurred, and the result of the abnormality determination performed by the control means provided in the anti-lock brake device is the result of either the first control means or the second control means. It is made effective only when an abnormality of the watchdog pulse is detected .
[0012]
In this way, since the existing control means is used for failure diagnosis, it is not necessary to newly provide a dedicated monitoring means.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0014]
FIG. 1 shows a schematic configuration of an SBW apparatus to which the present invention is applied. The SBW device 1 includes a steering wheel 2 operated by a driver, a steering angle sensor 3 attached to the steering wheel 2, a steering reaction force applying motor 4, a steering torque sensor 5, and left and right tires 6 and knuckle arms 7 And a steering rod 9 connected via a tie rod 8, a steering motor 10 that drives the steering rod 9 in the axial direction to give a cutting angle to the tire 6, a vehicle speed sensor 11 that outputs a vehicle speed, and a shaft of the steering rod 9 It includes a turning angle sensor 12 that outputs a turning angle of the tire 6 from a directional position, and a control device 13 that controls the steering reaction force applying motor 4 and the steering motor 10. The steering wheel 2 is always elastically biased toward the neutral position by an appropriate spring mechanism (not shown).
[0015]
As shown in FIG. 2, the control device 13 includes a steering reaction force control unit 14 that controls the steering reaction force application motor 4 based on signals from the steering torque sensor 5 and the vehicle speed sensor 11, the steering angle sensor 3, and the vehicle speed sensor 11. And a steering control unit 15 that controls the steering motor 10 based on a signal from the turning angle sensor 12, and the steering reaction force applying motor 4 and the steering motor 10 can be individually controlled. .
[0016]
In the steering reaction force control unit 14, the target steering reaction force setting unit 16 sets a target based on a deviation signal between the vehicle speed signal from the vehicle speed sensor 11 and the target value and actual value of the tire turning angle from the turning control unit 15. The drive current of the steering reaction force motor 4 is controlled so that the steering reaction force matches the output value (actual steering torque) of the steering torque sensor 5. Thereby, a force (reaction force) in the direction opposite to the operation direction of the driver is applied to the steering wheel 2. The steering reaction force is continuously variably controlled so as to increase as the turning angle of the tire 6 increases, or to be relatively large during high speed traveling and relatively small during low speed traveling. 2 and the tire 6 are added so as to obtain a steering feeling as if they are mechanically directly connected.
[0017]
On the other hand, in the turning control unit 15, the target turning angle setting unit 17 determines the target turning angle based on the operation amount signal including the operation direction of the steering wheel 2 from the steering angle sensor 3 and the vehicle speed signal from the vehicle speed sensor 11. The integral controller 18, the proportional controller 19, and the differential control are set so that the deviation between the target angle value and the actual tire angle value output from the angle sensor 12 is optimized according to the driving state at that time. The driving current of the steering motor 10 is controlled after appropriately compensating by the device 21. As a result, the optimum turning angle of the tire 6 corresponding to the driving state at that time is determined with respect to the operation amount of the steering wheel 2 by the driver, and the steering motor 10 is feedback-controlled.
[0018]
The control device 13 is provided with two ECUs, a main ECU 21 and a sub ECU 22 (see FIG. 3). As shown in FIG. 4, these two ECUs 21 and 22 constantly transmit a WDP (watchdog pulse) having a predetermined frequency, and both ECUs monitor each other by bidirectional communication. If any abnormality occurs in the ECU, normal WDP cannot be communicated. At this time, a failure determination flag is set.
[0019]
Here, it is not possible to determine whether there is an abnormality in the transmission of WDP or an abnormality in the reception simply by performing the WDP abnormality detection with each other. That is, it cannot be determined which ECU has failed. Therefore, in the present invention, the normal workload is relatively small, for example, the control ECU 23 of the ABS device (anti-lock brake device) is made to determine which ECU has failed, and only the normal ECU is operated. A switching signal is issued so that the
[0020]
If the ECUs 21 and 22 of the SBW device 1 ignore the signal from the ECU 23 of the ABS device unless the failure determination flag is set, the operation of the SBW device 1 is affected when the ECU 23 of the ABS device is abnormal. There is no effect. The ECU used for the failure diagnosis is not limited to the ABS device, and an ECU of another on-vehicle device such as a fuel supply system or an airbag control ECU can be appropriately used.
[0021]
【The invention's effect】
As described above in detail, according to the present invention, the existing ECU for controlling other in-vehicle devices is used as the ECU for determining the soundness of the ECU for the steering device. Therefore, it is only necessary to add data communication means. Therefore, it is not necessary to add a dedicated ECU for fail-safe of the SBW device, and a more reliable fail-safe system can be constructed without causing an increase in cost.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a steer-by-wire steering apparatus to which the present invention is applied. FIG. 2 is a control block diagram of a steer-by-wire steering apparatus to which the present invention is applied. Fig. 4 Schematic time chart for fault diagnosis [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steer-by-wire steering apparatus 2 Steering wheel 3 Steering angle sensor 4 Steering reaction force addition motor 6 Steering wheel 10 Steering motor 13 Control apparatus 15 Steering control part 16 Target steering reaction force setting part 21-23 ECU

Claims (1)

Steering means operated by the driver, driving means for giving a steering angle to the tire according to the operation amount of the steering means, and steering reaction force for giving the steering means a reaction force against the operating force of the driver A vehicle steering apparatus comprising: an imparting unit; a first control unit having an output instruction function for at least the driving unit; and a second control unit having an output instruction function for at least the steering reaction force applying unit. ,
Wherein with each emit watchdog pulse from the first control means and said second control means detects the abnormality What if monitoring the watchdog pulse from each other,
Control means provided in the anti-lock brake system mounted on a vehicle, the first and abnormalities comprising a function of discriminating the second control means, said first control means and said second control means To determine whether an abnormality has occurred in either
The result of the abnormality determination performed by the control means provided in the anti-lock brake device is only when one of the first control means and the second control means detects an abnormality of the watchdog pulse. A vehicle steering system characterized by being effective .

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