JPH092315A - Steering control device for vehicle - Google Patents

Abstract

PURPOSE: To ensure suitable initial reponsiveness, and improve controllability at the time of stopping the device even when steering angle-deviation of a target steering angle value from an actual steering angle value is small. CONSTITUTION: A target steering angle value of a steering wheel is set by a target steering angle setting means, actual steering angle values of the steering wheel are measured by measuring means 61, 62, the steering angle deviation of the actual steering angle from the target steering angle is calculated by a steering angle deviation calculating means 24, and a steering angle control means is driven in response to the duty set by a duty setting means 31 to control the steering angle. When the deviation of the steering angle is below a specified value, the rate of increasing the duty is set larger compared to that at the time when the deviation of the steering angle exceeds the specified value, and when the differentiated value of the steering angle deviation is below zero, output obtained by a steering angle deviation differentiating means is allowed to have the property that it is smaller than that in a case where it is greater than zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device, and more particularly to a front wheel steering device for correcting the steering angle of the front wheels of a four-wheel vehicle and a rear wheel steering device for adjusting the steering angle of the rear wheels. Involved in various steering control devices.

[0002]

2. Description of the Related Art Conventionally, there are known front wheel steering systems for correcting the steering angles of the front wheels of four-wheeled vehicles and rear wheel steering systems for adjusting the steering angles of the rear wheels. For example, in Japanese Unexamined Patent Publication No. 2-200573, when an auxiliary steering wheel is steered to a target steering angle in accordance with a steering angle of a main steering wheel, a pulse to an electric motor is generated according to an actual steering angle of a secondary steering wheel and a vehicle speed. A four-wheel steering control device is disclosed in which the duty ratio of current is changed to control the steering wheels. As a result, in the high vehicle speed range, the steered wheels are reliably steered to the target steering angle, and in the low vehicle speed range, vibrations are prevented from occurring in the steered wheels, and the steered wheels are stably steered. It is what makes me.
Specifically, as shown in FIG. 6 of the publication, the duty ratio increases as the deviation between the target steering angle of the rear wheels and the actual steering angle increases, and this relationship is changed depending on the vehicle speed. ing.

[0003]

In the four-wheel steering control device described in the above publication, the duty ratio is small when the deviation between the target steering angle and the actual steering angle is small, so that the current for driving the actuator such as the electric motor is reduced. Get smaller. Therefore, it is difficult to start the actuator with a large static friction force, but once it is started, there is a problem that the duty becomes too large after the start and it is difficult to stop it. It was.

Therefore, the present invention secures an appropriate initial responsiveness in the vehicle steering control device even when the deviation between the target steering angle and the actual steering angle is small, and even when the vehicle is once started, the initial value is set to the desired value. An object of the present invention is to provide a device for stopping an electric motor and improve controllability of the electric motor.

[0005]

In order to achieve the above object, in claim 1 of the present invention, a target rudder angle setting means (21) for setting a target rudder angle value of a steered wheel to be controlled; Measuring means (61, 62) for measuring the actual steering angle value of the steered wheels
And a steering angle deviation calculating means (30) for calculating a steering angle deviation between the actual steering angle value and the target steering angle value by the measuring means, and a duty setting for setting a duty according to an output from the steering angle deviation calculating means. In a vehicle steering control device comprising means (32) and steering angle control means for controlling the steering angle of the steered wheels according to the output of the duty setting means, the output by the steering angle deviation computing means is differentiated. Steering angle deviation differentiating means (3
1), the duty setting means, when the output from the steering angle deviation differentiating means is larger than zero, when the steering angle deviation is equal to or less than a predetermined value, the duty angle setting means exceeds the predetermined value. Is set to a large value and the output by the steering angle deviation differentiating means is less than or equal to zero, the output by the duty setting means is smaller than that when the output by the steering angle deviation differentiating means is greater than zero. The characteristic is that

Further, in claim 2, a target rudder angle setting means (21) for setting a target rudder angle value of the steered wheels to be controlled.
And a measuring means (61, 61) for measuring the actual steering angle value of the steered wheels.
62), a steering angle deviation calculating means (30) for calculating a steering angle deviation between the actual steering angle value and the target steering angle value by the measuring means, and a duty is set according to the output by the steering angle deviation calculating means. In a steering control device for a vehicle, which comprises a duty setting means (32) and a steering angle control means for controlling the steering angle of the steered wheels according to the output of the duty setting means, the output of the duty setting means is differentiated. A duty differentiating means (31a), and the duty setting means,
When the output from the duty differentiating means is greater than zero, when the steering angle deviation is less than or equal to a predetermined value, the duty increase rate relative to the steering angle deviation is set to be larger than when the output exceeds the predetermined value. When the output from the duty differentiating means is less than or equal to zero, the output from the duty setting means is set to a value smaller than that when the output from the duty differentiating means is greater than zero.

Further, in claim 3, target rudder angle setting means (21) for setting a target rudder angle value of the steered wheels to be controlled.
And a measuring means (61, 61) for measuring the actual steering angle value of the steered wheels.
62), a steering angle deviation calculating means (30) for calculating a steering angle deviation between the actual steering angle value and the target steering angle value by the measuring means, and a duty is set according to the output by the steering angle deviation calculating means. A steering control device for a vehicle, comprising: a duty setting means (32); and a steering angle control means for controlling a steering angle of the steered wheels in accordance with an output of the duty setting means. It is characterized in that a predetermined duty is added to the output by the duty setting means and the result is outputted.

[0008]

In the vehicle steering control device having the above structure,
The target rudder angle setting means sets the target rudder angle value of the steered wheel to be controlled, and the measuring means measures the actual rudder angle value of the steered wheel. A steering angle deviation between the actual steering angle value and the target steering angle value is calculated by the steering angle deviation calculation means, and the duty is set by the duty setting means by this deviation,
The steering angle control means is driven according to the duty to control the steering angle. In the duty setting means, when the steering angle deviation is less than or equal to a predetermined value, the increase rate of the duty with respect to the steering angle deviation is set to be larger than when it exceeds the predetermined value. Therefore, even when the steering angle deviation is small, the steering angle control means Is controlled with a large duty. Therefore, even when an actuator having a large static friction force is used, the initial driving force can be secured. On the other hand, when the output value by the steering angle deviation differentiating means is less than or equal to zero, the duty first sharply decreases and then gradually decreases. Due to this decrease in duty, the current flowing through the electric motor decreases,
The electric motor slows down, shifts to the stop direction, and is in a state where it is easy to stop.

As described in claim 2, when the output value by the duty differentiating means is less than or equal to zero, the duty is sharply reduced at first and then gradually reduced. The decrease in the duty causes a decrease in the current flowing through the electric motor, and the electric motor lowers the rotation speed, shifts to the stop direction, and is in a state where it is easy to stop.

Further, as described in claim 3, by adding the duty of a predetermined value to the value corresponding to the output of the steering angle deviation calculating means only when the steering angle control is started and outputting the value, the initial responsiveness is improved. As a result, the electric motor becomes easier to move and the controllability is improved.

[0011]

The present embodiment relates to a rear wheel steering control device for steering rear wheels in response to steering of front wheels of a vehicle, and FIG. 2 shows an overall configuration of a vehicle equipped with the steering control device. The front wheels 13 and 14 are steered by the front wheel steering mechanism 10 in response to a turning operation of a steering wheel 19. The front wheel steering mechanism 10 is provided with a front wheel steering angle sensor 17, which is a potentiometer for detecting the steering angle amounts of the front wheels 13 and 14, and the output thereof is input to the electronic control unit 20.

A vehicle speed sensor 9 for detecting the speed of the vehicle
Is provided, and its output is input to the electronic control unit 20. The vehicle speed sensor 9 may be configured to detect the vehicle speed in two systems by a pair of sensors and output the average value or the maximum value thereof as the vehicle speed. With such a configuration, a sensor abnormality can be easily detected. can do.

A rear wheel steering angle mechanism 18 is connected to the rear wheels 15 and 16 and steered according to the rotation of the electric motor 12. In the present embodiment, the electric motor 12 is a three-phase brushless motor, and a relative steering angle sensor 61 for detecting the rotation angle is provided at the axial end portion thereof. Relative steering angle sensor 61
As the above, a magnetic pole sensor that outputs a magnetic pole signal according to a change in the magnetic pole of the electric motor 12 is provided, and the output signal represents the relative steering angle. Further, an absolute steering angle sensor 62 of a potentiometer for detecting the steering angle amounts of the rear wheels 15 and 16 is provided, and the relative steering angle sensor 61 and the absolute steering angle sensor 62 constitute a rear wheel steering angle sensor 60. The actual steering angles of the wheels 15 and 16 are detected.

As shown in FIG. 3, the rear wheel steering mechanism 18 has a cover 52 fixed to a housing 51, and a motor housing 53 of the electric motor 12 and a relative steering angle sensor 61 are provided integrally with the cover 52. Has been. As is apparent from FIG. 4, a rack shaft 55 is provided at a right angle to the traveling direction of the vehicle, and both ends of the rack shaft 55 are connected to knuckle arms of rear wheels via ball joints 58. A tube 59 is provided at the right end of the housing 51 in FIG.
Even if the rack shafts 55 are fitted in and the rack shafts 55 having different lengths are provided, the tube 57 can be replaced without changing the housing 51. A rack 56 is formed on the rack shaft 55, and the rack 56 is configured to mesh with a pinion 57 extending in the front-rear direction of the vehicle.

As shown in FIG. 4, a pinion 12p is provided at the tip of the motor shaft 12s of the electric motor 12.
A gear 12g meshes with the pinion 12p to form a hypoid gear. This hypoid gear is the motor shaft 12
Although the rotation of s is transmitted as the rotation of the gear 12g, when a rotational force is applied to the gear 12g from the rack shaft 55 side,
The reverse efficiency is zero so that the motor shaft 12s of the electric motor 12 does not rotate. Although the static friction force is small in the rear wheel steering mechanism 18 having such a configuration, a large static friction force may be generated depending on the design or assembly.

The electric motor 12 is controlled by a signal from the electronic control unit 20. This electronic control unit 20
Outputs of the rear wheel steering angle sensor 60 including the vehicle speed sensor 9, the front wheel steering angle sensor 17, the relative steering angle sensor 61, and the absolute steering angle sensor 62 are input to the rotation of the electric motor 12 according to these outputs. The amount is set.

FIG. 5 shows the configuration of the electronic control unit 20. A battery 41 is connected to the electronic control unit 20. The battery 41 is connected to the motor driver 44 via the power supply terminal IP1, and the motor driver 4 is connected via the ignition switch 42 and the power supply terminal IP2.
4 and a constant voltage regulator 43 that outputs a constant voltage Vcc
Connected to.

The electronic control unit 20 has a microprocessor 45 which is a control means.

The vehicle speed sensor 9 and the front wheel steering angle sensor 1 described above.
7, the signal from the rear wheel steering angle sensor 60 is the interface 46
Is input to the microprocessor 45 via. The terminals of each phase of the electric motor 12 are connected to the motor driver 44 of the electronic control unit 20, and the motor driver is supplied with power from power supply terminals IP1 and IP2. Then, a control signal is output from the microprocessor 45 to the motor driver 44.

In the microprocessor 45, FIG.
The target rudder angle is set according to the control block diagram shown in (1) and the servo control of the electric motor 12 is performed. In the target value setting unit 21, the target steering angle value θa of the rear wheels 15 and 16 is set according to the steering angles of the front wheels 13 and 14 and the vehicle speed. Specifically, the target steering angle value θa is calculated based on the product of the coefficient set by the target value setting unit 21 according to the output of the front wheel steering angle sensor 17 and the coefficient set by the output of the vehicle speed sensor 9. Is set.

For example, when the vehicle is stopped, the rear wheels 1
5 and 16 are proportional to the steering angles of the front wheels 13 and 14
Target steering angle value θ so that steering is performed in the opposite direction to 3 and 14
a is set, which reduces the turning radius of the vehicle. When the vehicle is traveling at high speed, the target steering angle value θa is the front wheel 1
It is set so as to be proportional to the steering angle of 3, 14 and the rear wheels 1
Since the steering wheels 5, 16 are steered in the same direction as the front wheels 13, 14, steering stability is ensured when the vehicle turns.

The target steering angle value θa set as described above
Is differentiated by the differentiating unit 22, and the differential gain setting unit 23 obtains the differential gain Gθa according to a predetermined characteristic from the differential value Dθa. That is, when the absolute value of the differential value Dθa is less than or equal to the predetermined value (0.12 deg), the differential gain Gθa is set to zero, and when the absolute value of the differential value Dθa is greater than or equal to the predetermined value (0.48 deg), the differential value is differentiated. The gain Gθa is set to a predetermined value (4). Therefore, as shown in FIG. 8, the absolute value of the differential value Dθa is 0.12 to 0.47 de
When it is in the range of g, the differential gain Gθa becomes a value of 0 to 4.

On the other hand, the rotation angle θm of the electric motor 12 is detected by the relative steering angle sensor 61, is output as the actual steering angle value θr via the steering angle conversion unit 34, and is supplied to the subtraction unit 24.

The output of the relative steering angle sensor 61 is a relative steering angle value and does not represent the actual steering angle value, but is corrected by the steering angle conversion unit 34 based on the output of the absolute steering angle sensor 62. Therefore, the actual steering angle value θr is output from the steering angle conversion unit 34. In the subtraction unit 24, the actual steering angle value θr is subtracted from the target steering angle value θa to obtain the steering angle deviation Δθa. This steering angle deviation Δθa is processed as follows via the steering angle deviation dead zone applying unit 25.

As shown in FIG. 6, the steering angle deviation dead zone applying section 25 processes the output steering angle deviation value θd as zero when the absolute value of the steering angle deviation Δθa is less than or equal to a predetermined value α. Thus, the control is configured to stop when the value of the steering angle deviation Δθa is small. The steering angle deviation θd thus obtained is sent to the differentiating section 26 and the proportional section 28. The proportional portion 28 multiplies the steering angle deviation value θd by a predetermined proportional gain to obtain a proportional term Ps. Further, the differentiator 26 differentiates the steering angle deviation value θd to obtain the steering angle deviation differential value Dθd.

The steering angle value θc is limited by the steering angle deviation limiter 30. The steering angle deviation limiter 30 is shown in FIG.
The control amount Oc is set in proportion to the steering angle value θc, and the control amount Oc is set to a predetermined upper limit value (1.5 de
g) or more or a predetermined lower limit value (-1.5 deg) or less is set. This control amount Oc is differentiated by a steering angle deviation differentiating unit 31 which is a steering angle deviation differentiating unit to obtain a steering angle deviation differential value DOc. Is converted into a duty Dy by the pulse width modulation (PWM) unit 33.
Is supplied to. In the pulse width modulator 33, a pulse signal Pw corresponding to the duty Dy is formed and output to the motor driver 44.

In the deviation-duty converter 32, the duty Dy is set based on the deviation-duty characteristic shown by the solid line in FIG. 9, for example. According to the control amount Oc corresponding to the steering angle deviation, when the steering angle deviation Oc is equal to or less than the predetermined value Kc, the increase rate of the duty Dy is set to be larger than that when the steering angle deviation Oc exceeds the predetermined value Kc. Predetermined value Kc
Is set to a value that cancels the static friction force generated when the actuator starts driving, so that even when the electric motor 12 is started with respect to the static friction force with a small steering angle deviation, the predetermined drive current is The obtained driving force can be secured. In this way, the actuator including the electric motor 12 has a proper initial response. Further, by providing a characteristic that the duty is rapidly reduced when the value DOc obtained by differentiating the steering angle deviation is zero, and then the duty is gradually reduced, the current flowing through the electric motor is rapidly reduced, and Since the state shifts to the stop direction of the motor 12, the electric motor 12 easily stops.

Further, as shown in the second embodiment of FIG. 10, in the deviation-duty converter 32, the duty Dy is set based on the deviation-duty characteristic. According to the control amount Oc corresponding to the steering angle deviation, when the steering angle deviation Oc is equal to or less than the predetermined value Kc, the increase rate of the duty Dy is set to be larger than that when the steering angle deviation Oc exceeds the predetermined value Kc. The predetermined value Kc is set to a value that cancels the static friction force generated when the actuator starts driving, and thus the predetermined value Kc is set even when the electric motor 12 is started with respect to the static friction force with a small steering angle deviation. A driving current can be obtained and a desired driving force can be secured. In this way, the actuator including the electric motor 12 has a proper initial response. Furthermore, by providing a characteristic that the duty is rapidly reduced when the value DDy obtained by differentiating the duty Dy is zero, and then the duty is gradually reduced, the current flowing through the electric motor is rapidly reduced, Since the state shifts to the stop direction of 12, the electric motor 12 easily stops.

Further, as shown in the third embodiment of FIG. 11, the detection unit 34 determines when the output θr of the steering angle conversion unit 34 is not zero, that is, whether or not the electric motor 12 is being started.
Then, the selection unit 32a selects whether to add a constant duty α to the duty. In this manner, the initial controllability may be improved by adding the constant duty α and outputting the duty only when the selection unit 32a is switched and the electric motor is started when the electric motor 12 starts moving in the detection unit 34a. However, the deviation-duty characteristic may be set as shown by the chain double-dashed line in FIG. According to this characteristic, when a slight steering angle deviation occurs, the predetermined duty value Kd is immediately set, and thereafter the inclination value increases with the same inclination as in the conventional example.

In this way, the motor driver 44 operates the electric motor 12 in accordance with the pulse signal Pw supplied.
Are servo-controlled and driven. An integral term may be added to the PD control, and the rotation angle θ of the electric motor 12 may be added.
Since m also changes depending on the fluctuation of the power supply voltage, the battery voltage may be measured and the pulse signal Pw may be corrected according to the voltage.

[0031]

According to the present invention, the steering angle control means controls the steering angle with respect to the steered wheel to be controlled, and the steering angle control amount is calculated by calculating the steering angle deviation between the actual steering angle value and the target steering angle value. When the steering angle deviation is small, the duty setting means is configured to set the duty ratio to the steering angle deviation to a large value when the steering angle deviation is less than or equal to a predetermined value compared to when it exceeds the predetermined value. In addition, the steering angle control means can be controlled with a large duty to ensure the desired driving force. Therefore, even when the static friction force is large, the appropriate desired responsiveness can be obtained, and once the electric motor starts to be driven. Since it is easy to stop, controllability can be improved.

[Brief description of drawings]

FIG. 1 is a control block diagram relating to servo control of an electric motor according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a vehicle steering control device according to an embodiment of the present invention.

FIG. 3 is a front view of a rear wheel steering mechanism according to an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a rear wheel steering mechanism according to an embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of an electronic control unit according to an embodiment of the present invention.

FIG. 6 is a graph showing the input / output characteristics of the steering angle deviation dead zone imparting section in the embodiment of the present invention.

FIG. 7 is a graph showing the input / output characteristics of the steering angle deviation limiter in one embodiment of the present invention.

FIG. 8 is a graph showing the input / output characteristics of the differential gain setting unit in the embodiment of the present invention.

FIG. 9 is a graph showing an input / output characteristic of a deviation-duty converter in one example of the present invention.

FIG. 10 is a control block diagram relating to servo control of an electric motor according to a second embodiment of the present invention.

FIG. 11 is a control block diagram relating to servo control of an electric motor according to a third embodiment of the present invention.

[Explanation of symbols]

9 Vehicle speed sensor 12 Electric motor 17 Front wheel steering angle sensor 20 Electronic control unit 22 Differentiating part 23 Differential gain setting part 24 Subtracting part 25 Steering angle deviation dead zone applying part 26 Differentiating part 27 Multiplying part 28 Proportional part 29 Addition part 30 Steering angle deviation limiter 31 Differentiator 32 Deviation-Duty Converter 33 Pulse Width Modulator (PWM) 34 Steering Angle Converter 43 Constant Voltage Regulator 44 Motor Driver 45 Microprocessor 46 Interface 60 Rear Wheel Steering Angle Sensor 61 Relative Steering Angle Sensor 62 Absolute Steering Angle Sensor

Claims (3)

[Claims] 1. A target steering angle setting means for setting a target steering angle value of a steered wheel to be controlled, a measuring means for measuring an actual steering angle value of the steered wheel, an actual steering angle value by the measuring means, and Rudder angle deviation calculation means for calculating the rudder angle deviation of the target rudder angle value, duty setting means for setting a duty according to the output from the rudder angle deviation calculation means, and the steered wheels according to the output of the duty setting means In a steering control device for a vehicle, comprising: a steering angle control means for controlling the steering angle, the steering angle deviation differentiating means for differentiating the output by the steering angle deviation calculating means, and the duty setting means, When the output from the differentiating means is greater than zero, the duty ratio with respect to the steering angle deviation is set to be larger when the steering angle deviation is less than or equal to a predetermined value, and when the steering angle deviation is greater than the predetermined value, the steering angle deviation differential is set. By means When the output of the steering angle deviation is smaller than zero, the duty is set to a value smaller than that when the output of the steering angle deviation differentiating means is larger than zero. 2. A target rudder angle setting means for setting a target rudder angle value of a steering wheel to be controlled, a measuring means for measuring an actual rudder angle value of the steered wheel, an actual rudder angle value by the measuring means and the Rudder angle deviation calculation means for calculating the rudder angle deviation of the target rudder angle value, duty setting means for setting a duty according to the output from the rudder angle deviation calculation means, and the steered wheels according to the output of the duty setting means In a steering control device for a vehicle, comprising: a steering angle control means for controlling the steering angle of the vehicle, a duty differentiating means for differentiating an output from the duty setting means is provided, and the duty setting means has a zero output from the duty differentiating means. When the steering angle deviation is larger than the predetermined value, the duty increase ratio with respect to the steering angle deviation is set to be large when the steering angle deviation is equal to or smaller than the predetermined value. When the output from the means is less than or equal to zero, the duty is set to a smaller value than when the output from the duty differentiating means is greater than zero. 3. A target rudder angle setting means for setting a target rudder angle value of a steering wheel to be controlled, a measuring means for measuring an actual rudder angle value of the steered wheel, the actual rudder angle value and the target rudder angle. Steering angle deviation calculating means for calculating a steering angle deviation of a value, duty setting means for setting a duty according to an output from the steering angle deviation calculating means, and a steering angle of the steered wheels according to an output of the duty setting means In a vehicle steering control device including a steering angle control means for controlling, the duty setting means sets a predetermined value to a value corresponding to the output of the steering angle deviation calculation means only when control by the steering angle control means is started. A steering control device for a vehicle, which adds and outputs a duty.