JP4639796B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus, and more particularly to a steering apparatus that performs steer-by-wire control with a backup system.

2. Description of the Related Art Conventionally, an electric power steering apparatus that applies assist torque by a motor based on steering torque is known. In such a conventional technique, when the ignition is turned on while rotating the steering wheel, the system is started in a state where steering torque is generated. At this time, an assist force is suddenly generated corresponding to the steering torque, and there is a risk of shocking the steering system. Therefore, in the techniques described in Patent Documents 1 and 2, the current command value of the electric power steering is gradually increased by fade-in control to avoid sudden generation of assist force (for example, Patent Documents 1 and 2). Patent Document 2).
Japanese Patent Laid-Open No. 11-263239 JP 2004-130903 A

  In recent years, the steering wheel and steering wheel are mechanically separated, and the steering amount of the steering wheel is controlled by a steering actuator etc. Hereinafter, it is described as SBW). In this SBW, a steering actuator is driven based on the steering wheel steering angle of the driver to control the steering amount of the steered wheels. Here, since the steering wheel and the steering wheel are not mechanically connected, when the ignition is turned on while operating the steering wheel, a state in which the relationship between the steering angle and the steering amount does not match occurs. . If a large current command value is generated in the steered actuator in order to match this relationship, the steered wheels may start to move at a stretch, giving a sense of discomfort. Therefore, it can be considered that the uncomfortable feeling is suppressed by applying the fade-in control described in the above prior art to the current command value to the steering actuator. However, the current command value of the steering actuator is suppressed more than necessary, and the steering actuator does not operate at the initial stage when the ignition is ON, and there is a possibility of giving a sense of incongruity due to a mismatch between the steering angle and the steering amount.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a vehicle steering apparatus capable of smoothly starting a system without giving a driver a sense of incongruity in a vehicle equipped with an SBW. There is.

In order to achieve the above object, in the present invention, a steering means to which a driver's steering angle is input, a steering means for turning steered wheels, a traveling condition detecting means for detecting a traveling condition of a vehicle, and the steering Steering amount control means for controlling the turning amount of the turning means to a target turning amount based on the steering angle input to the means and the running situation detected by the running situation detection means. In the vehicle steering apparatus, the turning amount control means is detected by a first turning amount calculation unit that calculates a first turning amount based on a steering angle input to the steering means, and the traveling state detection means. a second steering amount calculating unit for calculating the second steering amount for correcting the first steering amount based on the running condition is based on said first steering amount and the second steering amount a third turning amount calculating unit for calculating a target steering amount, and the said target steering amount and the actual turning amount deviates Have time to calculate a fade-correction coefficient for correcting the so that gradually increases toward the second steering amount to a value calculated by the second steering amount calculating unit, the correction by the fade-in correction factor And a fade-in control unit that outputs the second steered amount to the third steered amount calculating unit.

  Therefore, by performing the fade-in control only for the second turning amount, smooth turning amount control can be achieved while ensuring the turning amount by the first turning amount.

  Hereinafter, an embodiment for realizing a vehicle steering system of the present invention will be described based on Example 1 shown in the drawings.

[System configuration of vehicle steering system]
First, the configuration will be described. FIG. 1 is a system configuration diagram of the vehicle steering system according to the first embodiment. As a steering means for a driver to input a steering amount, a steering wheel 1 and a steering shaft 2 rotatably supported on the vehicle body side and connected to the steering wheel 1 are provided. A steering angle sensor 8 that detects a steering angle as a driver's steering amount and a steering-side torque sensor 9 that detects a steering torque as a driver's steering amount are provided on the steering shaft 2.

  Further, the steering wheel 20 side of the steering angle sensor 8 and the steering side torque sensor 9 has a reaction force motor 3 that applies a steering reaction force to the driver (the steering wheel 1). The reaction force motor 3 includes a steering side resolver 10 that detects a motor rotation angle of the reaction force motor 3. On the steered wheel 20 side of the reaction force motor 3, an electromagnetic clutch 6 capable of physically engaging and releasing the steering shaft 2 and the backup mechanism 7 is provided.

  The backup mechanism 7 is a cable-type column, one end of which is a steering side cable pulley 7a connected to the electromagnetic clutch 6, the other end of the steering wheel side cable pulley 7b connected to the pinion shaft 15, and both cable pulleys 7a and 7b. The two cables 7c and 7d are connected in a state where they are wound in opposite directions. When the electromagnetic clutch 6 is released, the rotation of the steering shaft 2 is not transmitted to the pinion shaft 15.

  On the other hand, when the steering wheel 1 is rotated in one direction while the electromagnetic clutch 6 is engaged, one of the two cables 7c and 7d transmits a steering torque input from the driver, The other cable is configured to exhibit a function equivalent to that of the column shaft by transmitting a reaction torque input from the steering wheel 20.

  As a steering means for steering the steered wheel 20, it has a pinion shaft 15 supported rotatably on the vehicle body side and connected at one end to the steered wheel side cable pulley 7b. The pinion shaft 15 is provided with a turning motor 5, a turning side resolver 11, a turning side torque sensor 12, and a rotary encoder 13.

  Two steered motors 5 are arranged on both sides of the pinion shaft 15. The steered motor 5 outputs a steered torque to the pinion shaft 15, and the steered side resolver 11 detects the rotation angle of the steered motor 5. The steered side torque sensor 12 is provided between the steered motor 5 and the steered wheel 20 and detects the rotational torque of the pinion shaft 15. The rotary encoder 13 detects the rotation angle of the pinion shaft 15 (corresponding to the turning angle δ).

  A rack and pinion mechanism (not shown) is provided at the steered wheel side end of the pinion shaft 15, and the steered wheel 20 is steered by moving the steering rack 4 in the axial direction.

  The vehicle steering apparatus is provided with a first control unit 100, a second control unit 200, and a third control unit 300. FIG. 2 is a block diagram showing the configuration of the first to third control units 100, 200, 300.

  The third control unit 300 includes a steering angle θ from the steering angle sensor 8, a steering torque from the steering torque sensor 9, a steering torque from the steering torque sensor 12, a pinion angle from the rotary encoder 13, and The vehicle speed detected by the vehicle speed sensor 14 is input.

  The first control unit 100 receives the motor rotation angle from the steering-side resolver 11 and the steering angle command value from the third control unit 300. Similarly, the second control unit 200 receives the motor rotation angle from the steering-side resolver 11 and the steering angle command value from the third control unit 300.

  In the third control unit 300, a turning angle command value is calculated based on each input sensor value, and the turning angle command value is output to the first and second control units 100, 200, and the turning torque, etc. Based on the above, the drive control of the reaction force motor 3 is performed. The first and second control units 100 and 200 execute steering motor drive control by feedback control based on the input steering angle command value.

  FIG. 3 is a block diagram showing the control configuration of the third control unit 300. The third control unit 300 outputs a first steering amount calculation unit 360 that outputs the actual steering angle θd detected by the steering angle sensor 8 in a one-to-one relationship (the first steering amount calculation described in the claims). A VGR map 310 (corresponding to the second turning amount calculation unit described in the claims), a fade-in control unit 320, and an addition unit 330 (corresponding to the third rotation amount described in the claims). A controller 340, and a reaction force calculator 350.

As shown in the steering angle ratio-vehicle speed map of FIG. 4, the VGR map 310 is based on the steering angle ratio (the ratio of the steering angle to the steering angle θ) set in accordance with the traveling state of the vehicle such as the vehicle speed. The steering angle θd is corrected. Specifically, at low vehicle speeds, the amount of steering with respect to the driver's steering angle is corrected to be large, and at high vehicle speeds, correction is made so that the steering angle with respect to the driver's steering angle is small. The steering load is reduced. Then, the second steering amount θs ^* for correcting the actual steering angle θd based on the steering angle ratio is calculated and output to the fade-in control unit 320.

The fade-in control unit 320 performs fade-in control that gradually increases the second turning amount θs ^* output from the VGR map 310. The fade-in control unit 320 according to the first embodiment is configured to execute the fade-in control when the system is started, such as when the ignition is turned on, but may be executed during normal SBW control. The fade-in control unit 320 calculates a fade-in correction coefficient γ that is corrected so as to gradually increase the second turning amount θs ^* , and outputs the corrected second turning amount γθs ^* to the adding unit 330. In a case other than when the ignition is on, specifically, after the actual turning angle θs substantially coincides with the target turning angle θ _ref ^* from the time the power is turned on, the second turning amount θs is set with the fade-in correction coefficient γ being 1. ^* Is output as is.

The adding unit 330 adds the corrected second turning amount γθs ^* to the first turning amount θd (actual steering angle θd), and outputs the target turning angle θ _ref ^* to the controller 340. The controller 340 converts the target turning angle θ _ref ^* into a turning angle command value i _ref that is a current command value, and outputs it to the first and second control units 100 and 200.

  The reaction force calculation unit 350 calculates a steering reaction force Fd corresponding to the turning torque of the turning torque sensor 12 and the actual turning angle θs input from the turning side resolver 11 and applies the steering reaction force to the reaction force motor 3. Command value Sd is output.

[Response delay avoidance by fade-in control]
The operation and effect in the above control configuration will be described by comparing the comparative example when the fade-in control is performed on the turning angle command value and the first embodiment with reference to the time chart of FIG.

  (When fade-in control is performed on the turning angle command value)

FIG. 5 is a control block diagram of a comparative example. This comparative example is an example in which a fade-in control unit is set to the turning angle command value θ _ref ^* immediately before being input to the turning motor 5 in a vehicle equipped with SBW. Hereinafter, description will be made based on the time chart of FIG.

When the ignition is turned on at time t1 and the driver starts steering the steering wheel 1, the first turning amount θd corresponding to the actual steering angle θd is output, and the second turning amount θs ^* is output. Is done. As described in the steering angle ratio-vehicle speed map of FIG. 4, when the ignition is turned on when the vehicle is stopped, the steering angle ratio is set to a large value, so the second steering amount θs ^* is also output to a large value. .

When γθ _ref ^* is output as the turning angle command value at time t2, the actual turning angle θs corresponding to the value is output. When the fade-in control is performed on the turning angle command value θ _ref ^* immediately before being input to the turning motor 5, the fade-in control is performed on both the first turning amount θd and the second turning amount θs ^*. Become.

Here, as shown by the solid line in the time chart of the comparative example of FIG. 6, when the correction coefficient γ in the fade-in control is set to a small value, the first turning amount θd and the second turning amount θs ^* are output. However, there is a possibility that the steering is not performed by outputting a small steering angle command value. In addition, it takes time t5 until the turning angle command value γθ _ref ^* substantially coincides with the uncorrected turning angle command value θ _ref ^* . In SBW, since the steering wheel 1 and the steered wheel 20 are not mechanically connected, there is a possibility that the driver may feel uncomfortable.

Therefore, a case where a large correction coefficient γ is given in order to improve responsiveness is considered. In the SBW, when the ignition is turned on while steering the steering wheel 1, the steer-by-wire control may be started with a large deviation between the actual steering angle θd and the turning angle. At this time, in addition to the deviation of the first turning amount θd, the deviation of the second turning amount θs ^* is also added. Then, as indicated by the dotted line in the time chart of the comparative example of FIG. 6, the steering angle command value γθ _ref ^* may overshoot (particularly at time t3), and although responsiveness can be ensured, it also gives a sense of discomfort. It will end up.

  The SBW system according to the first embodiment is configured to include a plurality of control units 100, 200, and 300. In this case, the so-called initialization timing at which the power supply voltage is supplied by the ignition ON and each control unit starts control is not necessarily coincident with the order of several tens of msec. Then, the deviation between the actual steering angle θd and the actual turning angle θs accumulated during this time may cause the above-described overshoot, which is not preferable.

On the other hand, in the first embodiment, as shown in FIG. 3, a fade-in control unit 320 is provided between the VGR map 310 and the addition unit 330 in order to reduce the response delay of the current command value i _ref due to the fade-in control. The controller 340 calculates the current command value i _ref after multiplying the steering angle θd by the fade-in correction coefficient γ.

  Thereby, even if it performs fade-in control at the time of steer-by-wire control in which the steering wheel 1 and the steering wheel 20 are mechanically separated, a turning angle command value based on the first turning amount θd is secured. Therefore, it is possible to reliably steer in the early stage of steering. Further, even when the ignition is turned on while turning the steering wheel 1 in the steer-by-wire-equipped vehicle, smooth turning can be achieved without causing the driver to feel uncomfortable.

  The fade-in control unit 320 multiplies the correction coefficient γ when the system is started, such as when the ignition is ON, and outputs the correction coefficient as 1 in other cases. Thereby, even when the deviation between the target turning angle and the actual turning angle is large when the ignition is ON, the steer-by-wire control can be started without a sense of incongruity. Further, during normal control after the system is started, fade-in control is not performed, and responsiveness can be ensured.

(Other examples)
As mentioned above, although the vehicle steering device of the present invention has been described on the basis of the embodiments, the specific configuration is not limited to these, and it does not depart from the gist of the invention according to each claim of the claims. Design changes and additions are allowed. For example, in the first embodiment, the values of the first turning amount calculation unit 360 and the fade-in control unit 320 are added in the adding unit 330. However, in the VGR map 310, the steering angle ratio is simply set and faded. The in-control unit 320 may be configured to multiply the steering angle ratio by a correction coefficient and output the corrected steering angle ratio. At this time, the first turning amount calculation unit 360 is not necessary, and is simply configured by changing the adding unit 330 to a multiplying unit and multiplying the actual steering angle θd by the corrected steering angle ratio. Also good.

It is a system configuration figure showing a steering device for vehicles. It is a block diagram which shows the control structure of a 1st thru | or 3rd control unit. It is a control block diagram of a 3rd control unit. It is a control block diagram of the power assist type steering device of a prior art example. FIG. 5 is a control block diagram in which fade-in control is performed on a command current immediately before being input to a steering motor in a steer-by-wire vehicle. 6 is a time chart in the configuration of each of FIGS. 4 and 5 and the embodiment of the present application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 2 Rotation angle sensor 3 Reaction force motor 4 Steering rack 5 Steering motor 6 Electromagnetic clutch 7 Backup mechanism 7a Steering side cable pulley 7b Steering wheel side cable pulley 7c, 7d Cable 8 Steering angle sensor 9 Steering side Torque sensor 10 Steering side resolver 11 Steering side resolver 12 Steering side torque sensor 13 Rotary encoder 14 Control unit 15 Pinion shaft 20 Steering wheel
100 1st control unit
200 Second control unit
300 3rd control unit
310 VGR map
320 Fade-in controller
330 Adder
340 controller
350 Reaction force calculator

Claims (4)

Steering means for inputting the steering angle of the driver;
Steering means for steering the steering wheel;
Based on the traveling condition detection means for detecting the traveling condition of the vehicle, the steering angle input to the steering means, and the traveling condition detected by the traveling condition detection means, the turning amount of the steering means is set as the target turning A steering amount control means for controlling the amount,
In a vehicle steering apparatus comprising:
The turning amount control means is
A first turning amount calculation unit for calculating a first turning amount based on a steering angle input to the steering means;
A second turning amount calculation unit that calculates a second turning amount that corrects the first turning amount based on the traveling state detected by the traveling state detection means;
A third turning amount calculation unit for calculating the target turning amount based on the first turning amount and the second turning amount;
When said target steering amount and the actual turning amount is deviated, corrected to so that gradually increases toward the second steering amount to a value calculated by the second steering amount calculating section A fade- in control unit that calculates a fade-in correction coefficient and outputs the second turning amount corrected by the fade-in correction coefficient to the third turning amount calculation unit;
A vehicle steering apparatus comprising: The vehicle steering control device according to claim 1,
The second steering amount calculation unit reduces the second steering amount as the vehicle speed increases. The vehicle steering control device according to claim 1 or 2,
The vehicle steering apparatus according to claim 1, wherein the fade-in control unit is executed from when the turning amount control is started to when the actual turning amount and the target turning amount substantially coincide with each other . Steering means for inputting the steering angle of the driver;
Steering means for steering the steering wheel;
Based on the traveling condition detection means for detecting the traveling condition of the vehicle, the steering angle input to the steering means, and the traveling condition detected by the traveling condition detection means, the turning amount of the steering means is set as the target turning A steering amount control means for controlling the amount,
The steering amount control means calculates a first turning amount based on a steering angle input to the steering means, and is based on the running situation detected by the running situation detecting means. The second turning amount for correcting the first turning amount is calculated, and when the target turning amount and the actual turning amount are deviated, the second turning amount is set to the calculated value. A fade-in correction coefficient that is corrected so as to gradually increase toward the target is calculated, and the target turning amount is calculated based on the second turning amount corrected by the fade-in correction factor and the first turning amount. A vehicle steering apparatus characterized by the above.

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