JPH10217988A - Steering controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the flow of excessive drive currents for a steering shaft motor to prevent the overheating of the motor by limiting output of a drive motor based on the results of the detection on a side where shaft force is small when a deviation in shaft force detected by a pair of shaft force detection means, respectively, is out of a predetermined scope. SOLUTION: When steering a vehicle, steering reaction force F1 of a steering reaction force sensor 18a on a steering travelling wheel 14a side becomes a sufficiently large value when compared with steering reaction force F2 of a steering reaction force sensor 18b on a steering travelling wheel 14b side, if the directional steering travelling wheel 14a is in contact with a curb, etc. In this case, a deviation in detected values of two steering reaction force sensors 18a, 18b is out of a predetermined scope in a limiting circuit 27. If this condition continues for a fixed period of time, a steering control signal corresponding to F2 is output for steering reaction force having smaller absolute value of both steering reaction force by making a control displacement amount Ms of a steering shaft motor 11 equal to F2 so that output torque becomes equal in order to prevent the overheating of the steering shaft motor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device for turning a steered wheel in accordance with the rotation of a steering wheel, and more particularly, to a steering shaft coupled to the steering wheel and a steering mechanism for turning the steered wheel. Are mechanically separated from each other, and a steering control device in which these connecting mechanisms are replaced by an electric control device.

[0002]

2. Description of the Related Art An example of such a steering control device is shown in FIG. 3 (Japanese Patent Publication No. 6-98931). A steering shaft motor 122 is provided on the steering shaft 121 to which the steering handle 120 is attached.
, A steering reaction force is applied to the steering handle 120. When the steered shaft 132 is rotationally driven by the steered shaft motor 130, the pinion 131 at the tip of the steered shaft is rotated.
The rack shaft 134 meshed with is displaced along the axial direction,
The steered wheels 133 are steered in conjunction with the rack shaft 134. At this time, the turning axis is set so that the turning amount detected by the turning displacement sensor 137 matches the target control amount calculated by the steering displacement calculator 144 based on the detection result of the steering angle sensor 123. The drive of the steered shaft motor 130 is controlled by the motor control circuit 141.

[0003]

The conventional steering control is generally performed as described above. However, for example, in a situation where one of the steered wheels 133 is in contact with a curb or the like, if the driver continuously operates the steering wheel 120 to further steer the vehicle in this direction, the steering displacement amount Arithmetic unit 144
The drive signal is continuously output to the steered shaft motor 130 from the steered shaft motor control circuit 141 that has received the calculation result. Therefore, an excessive drive current is supplied to the turning shaft motor 130, and as a result, the motor may be overheated.

The present invention has been made to solve such a problem, and an object of the present invention is to prevent a situation in which an excessive drive current flows to a steered shaft motor and prevent overheating of the motor. It is to provide a steering control device.

[0005]

SUMMARY OF THE INVENTION Accordingly, a steering control device according to the present invention turns a steered wheel in conjunction with rotation of a steering wheel, and outputs a steering reaction force corresponding to the steering reaction force to the steering wheel. A steering control device for detecting a rotation angle of a steering shaft connected to a steering wheel, and a target control amount serving as a target of the steering control based on a detection result of the steering angle detection device. Target control amount calculating means for calculating the steering wheel, a steering means which is mechanically separated from the steering shaft, and has steered wheels connected to both sides, and a pair of detecting means for detecting an axial force applied to the steered means from each steered wheel. Axial force detecting means, a driving motor for driving the turning means, a turning control means for controlling the driving motor so that the turning amount of the steered wheels becomes the target control amount, and a pair of axial force detecting means, respectively. When the deviation of the detected axial force is out of the predetermined range, the axial force Based on the small side of the detection result,
Limiting means for limiting the output of the drive motor.

In the normal operation, the magnitude of the axial force (absolute value) applied to the turning means from the steered wheels on both sides is substantially equal, but if one steered wheel is in contact with a curb or the like. The axial force applied from the steered wheels is sufficiently larger than the axial force applied from the other steered wheels. Therefore,
In the limiting means, when the deviation of the axial force applied from the steered wheels on both sides to the steered means exceeds a certain range, it is determined that one steered wheel is in contact with the curb or the like and detected. The output of the drive motor is limited so that the motor output corresponds to the smaller axial force. As a result, it is possible to prevent a situation where an excessive drive current continues to flow through the drive motor.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the accompanying drawings.

FIG. 1 schematically shows a configuration of a steering control device according to the present embodiment. This steering control device includes a master unit A operated by a driver, a slave unit B for steering wheels,
And a control unit C for electrically controlling the master unit A and the slave unit B.

The master unit A includes a steering shaft 2 on which a steering wheel 1 is mounted, and a steering shaft motor 3 for rotating the steering shaft 2. The steering shaft 2 has a steering angle の of the steering shaft 2. A steering angle sensor 4 for detecting and a steering force sensor 5 for detecting a steering force are provided.

The slave section B includes a steered shaft motor 11 serving as a drive source when the steered shaft 13 is displaced and driven. A converter 12 is provided for converting the rotational motion of the rudder shaft motor 11 into a linear motion and displacing the steered shaft 13 in the axial direction. Steering shaft 1
3 are steered wheels 14a, 14a via tie rods 15a, 15b and knuckle arms 16a, 16b, respectively.
14b, and the steered shaft 13 is displaced along the axial direction, whereby the steered wheels 14a, 14b are steered according to the displacement amount and the displacement direction. I have. The tie rods 15a, 15b are connected to the left and right steering wheels 14a, 14b, respectively.
Turning reaction force sensors 18a and 18b for detecting an axial force (turning reaction force) applied to 15b are attached respectively. The turning shaft 13 is provided with a turning displacement sensor 17 for detecting the displacement of the turning shaft 13. The turning displacement sensor 17 detects the displacement of the turning shaft 13. Thus, the actual steering amount of the steered wheels 14a and 14b can be detected.

The control section C includes a steering shaft motor control circuit 21 for controlling the driving of the steering shaft motor 3 and a turning shaft motor control circuit 26 for controlling the driving of the steering shaft motor 11.
The drive control of both motors is performed based on the calculation result and the like given from each calculator.

The steering shaft motor control circuit 21 is provided with the calculation results of the steering force calculator 23 and the steering reaction force calculator 24. The steering force calculator 23 calculates the steering force T applied to the steering shaft 2 based on the detection result of the steering force sensor 5, and rotates the steering shaft 2 in the direction to which the steering force T is applied. Control amount aT (a is a coefficient corresponding to the steering force gear ratio)
Is calculated. The steering reaction force calculator 24 is provided with the steering reaction force sensor 1.
8a, 18b, based on the detection results F1, F2, F = (F
The steering reaction force F applied to the steering shaft 13 is calculated as 1 + F2) / 2. The steering shaft motor control circuit 21 calculates the rotation control amount Mm of the steering shaft 2 by the following equation (1) based on the calculation result of the steering force calculator 23 and the steering reaction force calculator 24, A reaction force control signal corresponding to the rotation control amount Mm is output to the steering shaft motor 3. In the expression (1), Gm is a gain coefficient indicating the gain of the output signal.

Mm = Gm · (aT−F) (1) The turning shaft motor control circuit 26 includes a turning displacement calculator 22.
And the calculation result of the target control amount calculator 25. The turning displacement calculator 22 obtains the displacement of the turning shaft 13 as the turning displacement X based on the detection result of the turning displacement sensor 17, and controls the control amount bX proportional to the turning displacement X. (B is a coefficient corresponding to the steering displacement transmission ratio). The target control amount calculator 25 calculates the steering angle Θ detected by the steering angle sensor 4.
Then, a target control amount θ to be a target when the steered wheels 14a and 14b are steered so as to correspond to the steering angle is calculated. The turning shaft motor control circuit 26 turns the steering wheels 14a and 14b based on the calculation results of the turning displacement amount calculator 22 and the target control amount calculator 25 so that the turning amount of the steered wheels 14a and 14b becomes the target control amount θ. The drive control of the rudder shaft motor 11 is performed. That is, the control displacement amount Ms of the turning shaft 13 is calculated by the following equation (2), and a turning control signal corresponding to the control displacement amount Ms is output to the turning shaft motor 11. (2)
In the equation, Gs is a gain coefficient indicating the gain of the steering control signal.

Ms = Gs · (θ−bX) (2) Also, the steered shaft motor control circuit 26 controls the steered shaft motor 11
Is provided with a limiting circuit 27 for limiting the output. The limiting circuit 27 is configured to detect the steering reaction force sensors 18a and 18b from the steering reaction force calculator 24 based on the detection results F1 and F2.
It is determined whether any of the steered wheels 14a and 14b is in contact with a curb or the like. In a situation where the steering is normally performed, the detection results of the two steering reaction force sensors 18a and 18b indicate that the output values of the sensors on the pulling side and the compression side have a difference in polarity, but the absolute values thereof are different. There is no significant difference. On the other hand, when the steering is performed, for example, if the steered wheel 14a is in contact with a curb or the like, the steered reaction force F1 detected from the steered reaction sensor 18a on the steered wheel 14a side generates the steered wheel F1. 14b
Steering reaction force F2 detected from the side steering reaction sensor 18b
This is a sufficiently large value compared to. In such a case, if the driver continues to operate the steering wheel 1 to steer the vehicle in this direction, the steering shaft motor 11
The excessively large drive current continues to flow, and the steered shaft motor 11 may be overheated. Then, in the limiting circuit 27, when the deviation between the detection values of the two turning reaction force sensors 18a and 18b is out of the predetermined range and the state is maintained for a certain period of time, of the detected both turning reaction forces, The output of the steered shaft motor 11 is limited so that the output torque becomes equal to the steered reaction force of the smaller absolute value. Specifically, in the above example, (2)
Without calculating the equation, the control displacement amount Ms is set to F2, and F2
And outputs a steering control signal corresponding to
The output torque of the steered shaft motor 11 is suppressed to F2, and overheating of the steered shaft motor 11 is prevented.

Here, the operation of the steering control device thus configured will be schematically described. Assuming that the steering wheel 1 is rotated while the vehicle is traveling straight, and the target control amount calculated at this time is θ, a control displacement amount Ms is generated by the equation (2), and the detected steering reaction force F1, If the deviation of F2 is within a predetermined range, the steering shaft motor control circuit 26
A steering control signal corresponding to the control displacement amount Ms is output. When the deviation between the detected turning reaction forces F1 and F2 is out of the predetermined range, a turning control signal corresponding to the turning reaction force having a smaller absolute value is output from the limiting circuit 27.

In response to the steering control signal, the steering shaft motor 1
1 is operated, the steered shaft 13 is displaced, and the steered wheels 14a, 1
4b is steered. The turning displacement X corresponding to the actual turning amount of the steered wheels 14a and 14b is given to the turning shaft motor control circuit 26 via the turning displacement calculator 22. Based on this, feedback control of the steered shaft motor 11 is performed. Then, when θ ≒ bX, the operation of the steered shaft motor 11 stops.

On the other hand, when the steered wheels 14a and 14b are steered, steering reaction forces F1 and F2 are generated, and the steering shaft motor control circuit 21 supplies the steering reaction force F obtained from these F1 and F2 to the steering shaft motor control circuit 21. And a control amount aT corresponding to the steering force T are given, and the drive control of the steering shaft motor 3, that is, the reaction force control given to the steering shaft 2 is performed based on the above formula (1). Then, when aT 軸 F, the operation of the steering shaft motor 3 stops.

Thereafter, when the steering wheel 1 is turned with a steering force T exceeding this reaction force, the target control amount θ also increases because the rotation angle of the steering shaft 2 increases. Therefore, the control displacement amount Ms in the equation (2) increases, and the steered shaft 13 is driven to be displaced by the steered shaft motor 11. When the turning shaft 13 is displaced, the turning reaction force F increases.
The steering shaft motor 3 is rotationally driven again so that m changes and the steering reaction force increases. By repeating this operation,
Steering wheels 14a, 14 corresponding to the steering angle of the steering wheel 1
The steering angle b is obtained, and a steering reaction force corresponding to the steering reaction force is obtained. Similarly, when the steering wheel 1 is returned, the steered wheels 1 corresponding to the return rotation angle of the steering wheel 1 are also set.
As the turning angles 4a and 14b follow, the steering force T of the steering wheel 1 also decreases corresponding to the turning reaction force F.

Although the steering control is continued in this way,
Here, a specific steering control process performed by the control unit C will be described based on the flowchart of FIG. This control process is started when the ignition switch is turned on, and is executed every predetermined time (for example, 2 msec.).

First, in step 100 (hereinafter, "step" is referred to as "S"), a coefficient a (a coefficient corresponding to the steering force transmission ratio) and a coefficient b (a coefficient corresponding to the steering displacement transmission ratio) stored in the ROM in advance. , Gm and Gs are read, and initialization is performed.

In S102, the target control amount θ corresponding to the steering angle Θ, the steering displacement X corresponding to the steering angles of the steered wheels 14a and 14b, and the steering force T calculated by the steering force calculator 23. The steering reaction forces F1 and F2 given to the steering reaction force calculator 24 are read.

In the following S104, it is determined whether or not the deviation between the read steering reaction forces F1 and F2 is within a predetermined range A. In this S104, the difference between the absolute values of the steering reaction forces F1 and F2 detected by the respective sensors is taken as {F1 |-| F2} ≦ A, and the absolute value of this difference is taken. Since the polarities of the output values of the sensors 18a and 18b are different between the tension side and the compression side, the polarity of the sensor output value is considered. In S104, if the deviation between the steering reaction forces F1 and F2 is within the predetermined range A (S1
04 (“Yes”), the process proceeds to S106.

In S106, the count value t of the timer is reset. This timer determines the steering reaction forces F1 and F2
Is a timer that counts the duration of the deviation from the predetermined range A.

At S108, S100 and S102
The control displacement amount Ms is calculated by the above equation (2) using the respective values read in step (1).

In the following S110, the steering reaction force F applied to the steering shaft motor control circuit 21 based on the steering reaction forces F1 and F2.
Is calculated as F = (F1 + F2) / 2. In S112, each value read in S100 and S102 and S11
Based on F calculated at 0, the rotation control amount Mm is calculated by the above equation (1).

In S114, a turning control signal corresponding to the control displacement amount Ms calculated in S108 is output to the turning shaft motor 11, and a reaction force control signal corresponding to the rotation control amount Mm calculated in S112 is output. Output to the steering shaft motor 3.

On the other hand, in S104, if the deviation between the steering reaction forces F1 and F2 is outside the predetermined range A ("No" in S104), the process proceeds to the steering control signal limiting process, and S116.
Then, the count value t of the timer is incremented.

In S118, the incremented count value t is compared with a predetermined value ts. This predetermined value ts is a value that defines the timing at which the restriction process is started, and when the deviation between the steering reaction forces F1 and F2 falls outside the predetermined range A exceeds the time ts, the actual rotation starts. The process proceeds to a process for limiting the rudder control signal. When the count value t of the timer is equal to or smaller than ts ("No" in S118), the deviation between the steering reaction forces F1 and F2 is outside the predetermined range A, but is less than the timing to start the limiting process. Therefore, the process proceeds to the normal steering control performed after S108.

On the other hand, if the count value t of the timer has exceeded ts ("Yes" in S118), the flow shifts to S120, where the magnitudes (absolute values) of the steering reaction forces F1 and F2 are compared. It is determined whether the steering abnormality has occurred on the side. As described above, a turning abnormality such as contact with a curb occurs on the side where the turning reaction force is large. For example, if the turning reaction force F1 is large ("Yes" in S120), a turning abnormality has occurred on the steered wheel 14a side, and in this case,
The control displacement amount Ms is set to the other steering reaction force F2 without calculating equation (2) (S122). If the steering reaction force F2 is large ("No" in S120), a steering abnormality has occurred on the steered wheel 14b side. In this case,
The control displacement amount Ms is set to the other steering reaction force F1 without calculating the equation (2) (S124).

Then, the flow shifts to S126, where an alarm for notifying the occurrence of abnormal steering is issued and a warning lamp is turned on to perform an alarm process for notifying the driver of the alarm.

Thereafter, the process proceeds to S110, where F is obtained from F1 and F2, and the rotation control amount Mm is calculated in S112 according to equation (1). And S114
Then, a steering control signal corresponding to the control displacement amount Ms set in S112 or S114 is output to the steering shaft motor 11, and a reaction force control signal corresponding to the rotation control amount Mm calculated in S112 is output to the steering shaft motor. Output to 3.

In the embodiment described above, the case where the drive control of the steered shaft motor 11 is performed by feeding back the output of the steered displacement sensor 17 is exemplified. However, the case where such feedback control is performed is limited. It does not do. For example, the turning shaft motor 11 is constituted by a step motor, and the rotation amount of the step motor is set to the target control amount θ.
, And the rotation of the step motor may be controlled based on the calculation result. In such a case, the feedback control becomes unnecessary.

[0033]

As described above, according to the steering control device of the present invention, when the deviation of the axial force detected by the axial force detecting means is out of the predetermined range, the axial force is large. It is determined that the steering abnormality is occurring on the side,
Since the output of the drive motor is limited based on the detection result on the side with the smaller axial force, an excessive drive current flows to the steered shaft motor even if a steering abnormality such as contact with a curb occurs. It is possible to prevent the situation from continuing, and it is possible to reliably prevent overheating of the motor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a steering control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a steering control process performed by a control unit.

FIG. 3 is a configuration diagram schematically showing a conventional steering control device.

[Explanation of symbols]

A: Master unit, B: Slave unit, C: Control unit, 1: Steering handle, 2: Steering shaft, 3: Steering shaft motor, 4: Steering angle sensor, 5: Steering force sensor, 11: Steering shaft motor ( Drive motor), 13 ... Steering shaft (steering means), 14a, 14b
... steered wheels (steered wheels), 18a, 18b ... steered reaction force sensors (axial force detecting means), 25 ... target control amount calculators, 21 ...
Steering shaft motor control circuit, 26: steering shaft motor control circuit (steering control means), 27: limiting circuit (limiting means).

Claims (1)

[Claims] 1. A steering control device for turning a steered wheel in conjunction with rotation of a steering wheel and applying a steering reaction force to the steering wheel in accordance with the steering reaction force, wherein the steering control device is connected to the steering wheel. Steering angle detection means for detecting a rotation angle of the steering shaft, and target control amount calculation means for calculating a target control amount to be a target of turning control based on a detection result of the steering angle detection means; A steering unit mechanically separated from a shaft, and the steered wheels connected to both sides; a pair of axial force detecting units configured to detect an axial force applied to the steered unit from the steered wheels; A drive motor for driving a steering unit, a steering control unit for controlling the drive motor so that the steering amount of the steered wheels becomes the target control amount, and shafts respectively detected by the pair of axial force detection units. When the deviation of force is out of the specified range, the axial force is small. Based on have side detection result, the steering control apparatus and a limiting means for limiting the output of the drive motor.