JP2007137283A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of improving a convergence property of steering without spoiling a follow-up property in automatic steering angle control. <P>SOLUTION: A steering angle control computing part 24 is furnished with a position control computing part 25 to compute a position control component ε_L to make an actual steering angle of a steering wheel follow up a target steering angle and a damping control computing part 26 to compute a damping control component ε_D to damp rotation of the steering following a change of the steering angle, and the damping control computing part 26 computes the damping control component ε_D by multiplying rotating speed ωs of the steering with a damping gain Kd. Additionally, the damping control computing part 26 has a damping gain variable computing part 35, and the damping control computing part 26 practices damping control computation in accordance with the damping gain Kd computed at this damping gain variable computing part 35. Thereafter, the damping gain variable computing part 35 computes the damping gain Kd which becomes larger as target steering angle variation ωs* to be input becomes smaller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus.

In recent years, the steering angle of the steered wheels is automatically controlled regardless of the steering operation based on the vehicle state quantity detected by various sensors, or the situation signal around the vehicle such as the inter-vehicle distance and the white line detection signal. There has been proposed a vehicle steering apparatus that enables the above. For example, in the vehicle steering apparatus described in Patent Document 1, the driving force of a brushless motor arranged coaxially with the steering shaft is transmitted to the steering wheel via the steering shaft in the same manner as the steering force input by the steering operation. And if it has a drive means which can give drive force for changing the rudder angle of a steered wheel to a steering system, such as an electric power steering device (EPS) etc. The automatic steering function can be realized through control.
JP-A-10-264837

  By the way, in the vehicle steering device having such an automatic steering function, a position control component for causing the actual steering angle of the steered wheels to follow the target rudder angle, and the rotation of the steering accompanying the change of the steered angle of the steered wheels are attenuated. Some of them generate a steering angle control command for the driving means by superimposing a damping control component for the driving means. That is, at the end of such automatic steering angle control, it is desirable that the steering that rotates with the change of the steering angle of the steered wheels also stop immediately. Therefore, the convergence is improved by superimposing the attenuation control component as described above on the position control component.

  However, originally, the convergence of the steering and the followability of the actual steering angle with respect to the target steering angle are mutually contradictory, and it is extremely difficult to achieve both. That is, if the gain (position control gain) is increased in the position control calculation in order to improve the followability, the convergence is impaired. Conversely, if the gain (attenuation gain) is increased in the attenuation control calculation, the followability is increased. Will be damaged. For this reason, conventionally, it has been necessary to set the attenuation gain low with an emphasis on followability, and thus, for example, during relatively slow control with a small change in the target rudder angle, or temporarily during rudder angle control. When the target rudder angle is suddenly fixed due to a general stop, there remains a problem in the convergence.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a vehicle steering apparatus capable of improving the convergence of the steering without impairing the followability in the automatic steering angle control. Is to provide.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a drive means capable of applying a drive force for changing a steering angle of a steered wheel to a steering system, and a control for controlling the operation of the drive means. A position control component for causing the actual steering angle of the steered wheel to follow a target rudder angle, and an attenuation control for attenuating the rotation of the steering accompanying the change of the steered angle of the steered wheel. A steering apparatus for a vehicle that generates a steering angle control command for the drive means by superimposing a component, wherein the control means calculates the attenuation control component by multiplying the rotational angular velocity of the steering by an attenuation gain. In addition, the attenuation gain is increased as at least one of a change amount of the target rudder angle, a differential value of the change amount, and a deviation between the target rudder angle and the actual rudder angle becomes smaller. And

  That is, when the target steering angle is abruptly fixed due to a relatively slow steering angle control in which the convergence of the steering (rotation) is reduced, or when the steering angle control is temporarily stopped, these state quantities Becomes small. Therefore, according to the above configuration, the stronger the tendency, that is, the closer to the state in which the rotation of the steering is stopped, the higher the convergence of the steering can be. By making the attenuation gain small, it is possible to ensure high followability. Then, by using these state quantities in combination, it is possible to achieve both the followability and the convergence at a higher level.

  According to the second aspect of the present invention, the control means is used for the threshold determination when at least one of the change amount, the differential value, and the deviation is smaller than a threshold corresponding to each of the state quantities. The gist is to change the attenuation gain based on at least one of the state quantities other than the state quantity.

According to the above configuration, it is possible to more effectively achieve both high followability and improved steering convergence.
According to a third aspect of the present invention, there is provided drive means capable of applying a drive force for changing the steering angle of the steered wheels to the steering system, and control means for controlling the operation of the drive means. By superimposing a position control component for causing the actual steering angle of the steered wheel to follow a target rudder angle and an attenuation control component for attenuating the rotation of the steering accompanying the change of the steered angle of the steered wheel, A steering apparatus for a vehicle that generates a steering angle control command of a driving means, wherein the control means calculates the attenuation control component by multiplying the rotational angular velocity of the steering by an attenuation gain, and changes the target steering angle. When at least one of the amount, the differential value of the change amount, and the deviation between the target rudder angle and the actual rudder angle is smaller than a threshold corresponding to each of these state quantities, the attenuation gain is increased. thing, The gist.

  According to the above configuration, it is possible to improve the convergence of the steering only when the rotation of the steering is close to the stop state. Therefore, the convergence of the steering can be improved without impairing the followability.

  ADVANTAGE OF THE INVENTION According to this invention, the steering apparatus for vehicles which can aim at the improvement of the convergence property of steering can be provided, without impairing the followable | trackability in automatic steering angle control.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a vehicle steering apparatus 1 according to the present embodiment. As shown in the figure, the steering shaft 3 to which the steering wheel 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4, and the rotation of the steering shaft 3 accompanying the steering operation is performed by the rack and pinion mechanism 4. Is converted into a reciprocating linear motion of the rack 5. The steering angle of the steered wheels 6, that is, the turning angle is varied by the reciprocating linear motion of the rack 5, thereby changing the traveling direction of the vehicle.

  The vehicle steering apparatus 1 according to this embodiment includes an EPS actuator 10 that applies an assist force for assisting a steering operation to a steering system using a motor 9 as a drive source, and a control unit that controls the operation of the EPS actuator 10. An electric power steering apparatus (EPS) including an EPS ECU 11.

  The EPS actuator 10 of this embodiment is a so-called rack assist type EPS actuator in which the motor 9 and the rack 5 are coaxially arranged, and the assist torque generated by the motor 9 is transmitted via a ball feed mechanism (not shown). It is transmitted to the rack 5. Note that the motor 9 of the present embodiment is a brushless motor, and rotates by receiving supply of three-phase (U, V, W) driving power from the EPS ECU 11. On the other hand, a torque sensor 14 and a vehicle speed sensor 15 are connected to the EPSECU 11. The EPS ECU 11 controls the assist torque generated by the motor 9, that is, the assist force applied to the steering system, based on the steering torque τ and the vehicle speed V detected by the torque sensor 14 and the vehicle speed sensor 15, respectively (power assist). control).

  In addition, the vehicle steering apparatus 1 of the present embodiment has an automatic steering function that automatically controls the steering angle (steering angle) of the steered wheels 6 using the driving force that the EPS actuator 10 applies to the steering system. is doing. Here, in the vehicle steering apparatus 1 of the present embodiment, the turning angle and the steering angle θs have a predetermined gear ratio, the turning angle is changed based on the rotation of the steering 2, and the steering is performed. 2 also rotates as the steering angle of the steered wheels 6 changes. Therefore, in this embodiment, the automatic steering angle control is performed so that the actual steering angle (steering angle) of the steered wheels 6 follows the target steering angle by position control on the steering side (steering angle base). It has become.

  Specifically, in the present embodiment, a steering sensor 16 is connected to the EPS ECU 11, and the steering angle θs detected by the steering sensor 16 is input together with the steering torque τ and the vehicle speed V. Then, the EPS ECU 11 controls the operation of the EPS actuator 10 so that the detected steering angle θs follows the target steering angle θs * input as a value indicating the target steering angle from a host ECU (not shown). The automatic steering angle control described above is executed.

Next, a control mode of the vehicle steering device of the present embodiment will be described.
FIG. 2 is a control block diagram of the vehicle steering apparatus of the present embodiment. Each control block shown below is realized by a computer program executed by the microcomputer 21 described later.

  As shown in the figure, the EPS ECU 11 includes a microcomputer 21 that outputs a motor control signal, and a drive circuit 22 that supplies three-phase drive power to the motor 9 that is a drive source of the EPS actuator 10 based on the motor control signal. I have.

  More specifically, the microcomputer 21 according to the present embodiment calculates a steering angle control command Iq_L * for automatic steering angle control in addition to the assist control calculation unit 23 that calculates an assist force command Iq_A * for power assist control. And a steering angle control calculation unit 24. In the present embodiment, the steering torque τ and the vehicle speed V are input to the assist control calculation unit 23, and the steering angle θs and the target steering angle θs * are input to the steering angle control calculation unit 24. Based on the input state quantity, an assist force command Iq_A * and a steering angle control command Iq_L * are calculated. The microcomputer 21 generates a current command Iq * that is a target current value of the motor 9 by superimposing the calculated assist force command Iq_A * and the steering angle control command Iq_L *.

  More specifically, in the present embodiment, the steering angle control calculation unit 24 calculates a position control component ε_L for causing the actual steering angle of the steering wheel 6 to follow the target steering angle, and the steering wheel. And an attenuation control calculating unit 26 for calculating an attenuation control component ε_D for attenuating the rotation of the steering wheel 2 associated with the change of the steering angle 6. A deviation Δθs between the target steering angle θs * and the actual steering angle θs is input to the position control calculation unit 25, and the position control calculation unit 25 performs feedback based on the input deviation Δθs. The position control component ε_L is calculated by the control. Specifically, the position control calculation unit 25 of the present embodiment includes a proportional control calculation unit 25a and an integral control calculation unit 25b, and the proportional control calculation unit 25a multiplies the deviation Δθs by the proportional term gain Kp. The integral control calculation unit 25b calculates the integral term control component εi by multiplying the integral value of the deviation Δθs by the integral term gain Ki. The position control calculation unit 25 superimposes the proportional term control component εp and the integral term control component εi, that is, calculates the position control component ε_L by proportional / integral control (PI control). On the other hand, in this embodiment, the differential value of the steering angle θs, that is, the rotational angular velocity ωs of the steering wheel 2 is input to the damping control calculation unit 26. Then, the attenuation control calculation unit 26 calculates the attenuation control component ε_D by multiplying the rotation angular velocity ωs by the attenuation gain Kd.

  In the present embodiment, the position control component ε_L calculated by the position control calculation unit 25 and the attenuation control component ε_D calculated by the attenuation control calculation unit 26 are input to the subtractor 27 and superimposed (subtracted) by the subtractor 27. Is done. The steering angle control calculation unit 24 outputs a value obtained by subtracting the damping control component ε_D from the position control component ε_L as a steering angle control command Iq_L *.

  In the present embodiment, the steering angle control command Iq_L * calculated by the steering angle control calculation unit 24 and the assist force command Iq_A * calculated by the assist control calculation unit 23 as described above are input to the adder 28, and the same The value added (superposed) in the adder 28 is input to the motor control signal output unit 29 as the current command Iq *. The motor control signal output unit 29 generates a motor control signal to be output to the drive circuit 22 by feedback based on the current command Iq * and the actual current value supplied to the motor 9.

  Specifically, the motor control signal output unit 29 includes the current command Iq *, the phase current values Iu, Iv, Iw detected by the current sensors 30 u, 30 v as the actual current values, and the rotation angle sensor 31. The detected motor rotation angle θm is input. The motor control signal output unit 29 then supplies a current amount to the motor 9 by current control in the d / q coordinate system based on the current command Iq *, the phase current values Iu, Iv, Iw, and the motor rotation angle θm. A motor control signal is generated so that (actual current value) follows the current command Iq * which is the control target amount. The drive circuit 22 supplies three-phase drive power to the motor 9 in response to the motor control signal output from the motor control signal output unit 29, whereby the operation of the motor 9, that is, the EPS actuator 10 is performed. To be controlled.

(Attenuation gain variable control)
Next, variable attenuation gain control in the vehicle steering apparatus of the present embodiment will be described.
As described above, in the configuration in which the steering angle control command Iq_L * is calculated by superimposing the position control component ε_L and the damping control component ε_D that are inherently opposite to each other, the position control gain (proportional in the present embodiment) is calculated. It is extremely difficult to optimize the term gain Kp and the integral term gain Ki) and the attenuation gain Kd. For this reason, normally, it is unavoidable to set the attenuation gain low with an emphasis on follow-up performance. For this reason, for example, at the time of relatively slow rudder angle control where the change in the target rudder angle is small, or rudder angle control. When the target rudder angle is suddenly fixed due to a temporary stop, the problem remains in its convergence.

  Considering this point, in the vehicle steering apparatus 1 of the present embodiment, the attenuation gain Kd is changed according to the state of the automatic steering angle control. More specifically, in the present embodiment, the attenuation control calculation unit 26 includes an attenuation gain variable calculation unit 35, and the attenuation control calculation unit 26 calculates the attenuation gain Kd calculated by the attenuation gain variable calculation unit 35. Based on the above, the above attenuation control calculation is executed. The variable attenuation gain calculator 35 changes the calculated attenuation gain Kd according to the state of the automatic steering angle control.

  Specifically, in the present embodiment, a target steering angle change amount ωs *, which is a change amount of the target steering angle θs *, is input to the attenuation gain variable calculation unit 35. Then, the attenuation gain variable calculation unit 35 calculates a larger attenuation gain Kd as the input target steering angle change amount ωs * becomes smaller. As shown in FIG. 3, the attenuation gain variable calculation unit 35 of the present embodiment has a map 35a in which the target rudder angle change amount ωs * and the attenuation gain Kd are associated with each other. The attenuation gain Kd is set to increase as the target rudder angle change amount ωs * decreases. Then, the attenuation gain variable calculation unit 35 calculates the attenuation gain Kd by referring to the input target rudder angle change amount ωs * in the map 35a.

  In other words, the target rudder angle is relatively slow during rudder angle control where the convergence of the steering (rotation) is reduced, or when the target rudder angle is suddenly fixed due to a temporary stop of the rudder angle control. The change amount ωs * is small. Accordingly, by adopting the above-described configuration, as the tendency becomes stronger, that is, the closer to the state where the rotation of the steering wheel 2 is stopped, the convergence can be improved, and at the same time, the target rudder angle change amount ωs. In normal times when * is large, by setting the attenuation gain Kd to be small, it is possible to ensure high followability.

In addition, you may change this embodiment as follows.
In the present embodiment, the EPS actuator 10 is used as a driving unit that can apply a driving force for changing the steering angle of the steered wheels. However, the present invention is not limited to this, and as long as the steering 2 is configured to rotate in accordance with the change in the steering angle of the steered wheels 6, like the vehicle steering apparatus described in Patent Document 1, the driving means separate from the power steering apparatus. You may actualize to the structure provided with. In this case, the power steering device is not limited to the electric type, and may be a hydraulic type.

  In the present embodiment, the automatic steering angle control is performed by the position control on the steering side (steering angle base), but not limited to this, the automatic steering angle control is performed on the steering wheel side (steering angle base). It is good also as a structure to perform.

  In the present embodiment, the attenuation gain variable calculation unit 35 calculates the attenuation gain Kd based on the map 35a in which the target rudder angle change amount ωs * and the attenuation gain Kd are associated with each other. However, the present invention is not limited to this, and the attenuation gain Kd may be increased when the target rudder angle change amount ωs * is smaller than the predetermined threshold value α.

  That is, as shown in the flowchart of FIG. 4, it is determined whether or not the input target rudder angle change amount ωs * is equal to or greater than a predetermined threshold value α (step 101), and the target rudder angle change amount ωs * is equal to or greater than the threshold value α. (Ωs * ≧ α, step 101: YES), the attenuation gain Kd is calculated as the normal value Kd0 (Kd = Kd0, step 102). When the target rudder angle change amount ωs * is smaller than the threshold value α (ωs * <α, Step 101: NO), the attenuation gain Kd is set to a stop value Kd1 (Kd1> Kd0) larger than the normal value Kd0. It is good also as a structure which calculates (Kd = Kd1, step 103). Even with such a configuration, it is possible to improve the convergence of the steering while ensuring high followability.

  In the present embodiment, the attenuation gain Kd is changed based on the target steering angle change amount ωs * that is the change amount of the target steering angle θs *. However, the present invention is not limited to this, and the attenuation gain Kd is changed based on the differential value of the change amount (target steering angle change amount ωs *) or the deviation (Δθs) between the target steering angle and the actual steering angle. Also good. Further, the attenuation gain Kd may be changed based on any combination of these state quantities, that is, at least one of them.

  Note that the form of “change” in this case is a case where the attenuation gain Kd increases as the state quantities become smaller as in the above embodiment, but the state quantities are smaller than the corresponding threshold values. The attenuation gain Kd may be increased. Further, when at least one of these state quantities is smaller than the corresponding threshold value, the attenuation gain Kd may be increased based on at least one of the other state quantities. Specifically, for example, when the differential value of the target rudder angle change amount ωs * is smaller than a predetermined threshold, the attenuation gain may be increased as the target rudder angle change amount ωs * is smaller.

The schematic block diagram of the steering apparatus for vehicles. The control block diagram of the steering device for vehicles. The schematic block diagram of a map. The flowchart which shows the control aspect of the attenuation gain of another example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering device for vehicles, 2 ... Steering, 6 ... Steering wheel, 10 ... EPS actuator, 11 ... EPSECU, 21 ... Microcomputer, 25 ... Position control calculating part, 26 ... Attenuation control calculating part, 35 ... Damping gain variable calculating part 35a ... Map, Iq_L * ... Steering angle control command, ε_L ... Position control component, ε_D ... Damping control component, Kd ... Damping gain, Kd0 ... Normal value, Kd1 ... Stop value, θs ... Steering angle, θs * ... Target steering Angle, Δθs: Deviation, ωs: Rotational angular velocity, ωs *: Target rudder angle change amount, α: Threshold value.

Claims (3)

Drive means capable of applying a driving force for changing the steering angle of the steered wheels to the steering system; and control means for controlling the operation of the drive means, wherein the control means determines the actual steered angle of the steered wheels. A steering angle control command for the drive means is generated by superimposing a position control component for following the target rudder angle and an attenuation control component for attenuating the rotation of the steering wheel as the steering angle is changed. A vehicle steering system that
The control means calculates the attenuation control component by multiplying the rotational angular velocity of the steering by an attenuation gain, changes the target rudder angle, a differential value of the amount of change, and the target rudder angle and the actual rudder. A vehicular steering apparatus, wherein the attenuation gain is increased as at least one of deviations from a corner becomes smaller. The vehicle steering apparatus according to claim 1,
When at least one of the amount of change, the differential value, and the deviation is smaller than a threshold corresponding to each of these state quantities, the control means is at least one of state quantities other than the state quantity used for the threshold determination. Changing the attenuation gain based on
A vehicle steering apparatus characterized by the above. Drive means capable of applying a driving force for changing the steering angle of the steered wheels to the steering system; and control means for controlling the operation of the drive means, wherein the control means determines the actual steered angle of the steered wheels. A steering angle control command for the drive means is generated by superimposing a position control component for following the target rudder angle and an attenuation control component for attenuating the rotation of the steering wheel as the steering angle is changed. A vehicle steering system that
The control means calculates the attenuation control component by multiplying the rotational angular velocity of the steering by an attenuation gain, changes the target rudder angle, a differential value of the amount of change, and the target rudder angle and the actual rudder. If at least one of the deviations from the corner is smaller than the threshold corresponding to each of these state quantities, increasing the attenuation gain;
A vehicle steering apparatus characterized by the above.

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