JP2006131074A - Electric steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric steering device excellent in astringency of steering, with high return speed. <P>SOLUTION: In the electric steering device comprising a steering torque sensor 30 for detecting steering torque to be inputted in a steering system; a steering angle calculating part 63 for detecting a steering angle of the steering system; a rotation speed calculating part 61 for detecting steering speed of the steering system; and a basic damper compensation current calculating part 62 for applying damping to the steering system based on the steering speed detected by the rotation speed calculating part 61, for driving a motor 11 and turning steering wheels based on the steering torque detected by the steering torque sensor 30, the electric steering device is provided with a damper ratio calculating part 64 for changing a damper gain of the basic damper compensation current calculating part 62 according to the steering angle detected by the steering angle calculating part 63, and the damper ratio calculating part 64 increases the damper gain as the steering angle becomes smaller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric steering apparatus.

An electric power steering device is known as a vehicle steering device. In the electric power steering apparatus, a steering shaft coupled to a steering wheel and a steering mechanism for turning a steered wheel are mechanically coupled, and a motor for assisting a steering force is linked to the steering mechanism. In general, the driving current of the motor is controlled such that the steering assist force increases as the steering input (for example, steering torque) of the driver applied to the steering wheel increases.
Some of these electric steering devices control the drive current of the motor so as to give damping to the steering shaft in accordance with the steering speed of the steering wheel.
Further, Patent Document 1 discloses a technique for controlling a steering return speed in a so-called steer-by-wire in which a steering wheel and a steering mechanism are mechanically separated.
Japanese Patent Laid-Open No. 10-264833

By the way, when damping is applied to the steering shaft, conventionally, the damping control amount of the steering shaft is determined in accordance with the steering speed. When the steering speed is the same, the same damping control amount is obtained regardless of whether the steering angle is large or small. It was set to. Therefore, if the damping control amount is set large, the convergence of the steering (the property that the steering system converges to the neutral point) will be improved, but the steering return will be slow. On the other hand, if the damping control amount is set small, the steering return will be Faster but less astringent. In other words, the convergence and return speed of the steering are in a trade-off relationship, and it was difficult to satisfy both at the same time.
Note that the technique disclosed in Patent Document 1 does not achieve both the convergence of the steering and the return speed.
Accordingly, the present invention provides an electric steering device that has excellent steering convergence and a high return speed.

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a steering input detection means (for example, a steering torque sensor 30 in an embodiment described later) for detecting a steering input input to the steering system, and the steering system. Steering angle detecting means for detecting a steering angle (for example, a steering angle calculating section 63 in an embodiment described later) and steering speed detecting means for detecting a steering speed of the steering system (for example, a rotational speed calculating section in an embodiment described later) 61) and damper means for applying damping to the steering system based on the steering speed detected by the steering speed detection means (for example, a basic damper compensation current calculation unit 62 in an embodiment described later), and the steering Based on the steering input detected by the input detection means, the motor (for example, the motor 11 in the embodiment described later) is driven. In an electric steering device (for example, an electric power steering device 100 in an embodiment to be described later) that steers a steered wheel (for example, a front wheel 10 in an embodiment to be described later), the steering angle is detected according to the steering angle detected by the steering angle detecting means. Damper gain changing means for changing the damper gain of the damper means (for example, a damper ratio calculating unit 64 in an embodiment to be described later) is provided, and the damper gain changing means increases the damper gain as the steering angle decreases.
With this configuration, when the steering speed is the same and the steering angle is small and large, the damper gain when the steering angle is small is set to a larger value than the damper gain when the steering angle is large. Can be set.

The invention according to claim 2 is a steering input detection means for detecting a steering input input to the steering system (for example, a steering torque sensor 30 in an embodiment described later), and a steering angle detection for detecting a steering angle of the steering system. Means (for example, a steering angle calculation unit 63 in an embodiment to be described later), steering speed detection means for detecting a steering speed of the steering system (for example, a rotation speed calculation unit 61 in an embodiment to be described later), and the steering speed detection And a damper means (for example, a basic damper compensation current calculation unit 62 in an embodiment to be described later) for applying damping to the steering system based on the steering speed detected by the means, and the steering input detected by the steering input detection means The motor (for example, the motor 11 in the embodiment described later) is driven based on the In an electric steering apparatus (for example, an electric power steering apparatus 100 in an embodiment to be described later) that steers the front wheels 10 in the example, the damper gain of the damper means is changed according to the steering angle detected by the steering angle detection means. A damper gain changing unit (for example, a damper ratio calculating unit 64 in an embodiment described later) includes a damper gain changing rate when the steering angle is equal to or smaller than a predetermined value, and a damper gain when the steering angle is larger than the predetermined value. An electric steering apparatus characterized by being set to be larger than a change rate.
By configuring in this way, when the steering speed is the same, comparing the case where the steering angle is small and the case where the steering angle is small, the damper gain when the steering angle is less than or equal to the predetermined value, the steering angle is larger than the predetermined value It can be set to a value larger than the damper gain at the time.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the motor is a brushless motor, and the motor position detecting means (for example, a resolver 14 in an embodiment described later) of the brushless motor A steering angle is detected.
With this configuration, the steering angle can be detected without using a steering angle sensor or the like.

  According to the first aspect of the present invention, when the steering speed is the same and the steering angle is small and large, the damper gain when the steering angle is small is larger than the damper gain when the steering angle is large. Since it can be set to a value, in a region where the steering angle is large (that is, when it is far from the neutral point), the return of the steering can be made faster, and as the steering angle becomes smaller (that is, it approaches the neutral point). As a result, the convergence of the steering is extremely improved, and both the return speed of the steering and the convergence of the steering can be achieved.

  According to the second aspect of the present invention, when the steering angle is equal to or less than a predetermined value when the steering speed is the same, the damper gain when the steering angle is equal to or less than the predetermined value Since it can be set to a value larger than the damper gain when the angle is larger than the predetermined value, the steering return can be made faster in the region where the steering angle is larger than the predetermined value (that is, when the steering angle is far from the neutral point). When the angle is equal to or smaller than a predetermined value (that is, when approaching the neutral point), the convergence of the steering is extremely improved, and both the return speed of the steering and the convergence of the steering can be achieved.

  According to the third aspect of the present invention, the steering angle can be detected without using a steering angle sensor or the like, so the number of parts can be reduced.

Embodiments of an electric steering apparatus according to the present invention will be described below with reference to the drawings of FIGS.
As shown in FIG. 1, the vehicle electric power steering device (electric steering device) 100 includes a steering shaft 1 connected to a steering wheel (steering means) 2.
The steering shaft 1 is configured by connecting a main steering shaft 3 integrally coupled to a steering wheel 2 and a pinion shaft 5 provided with a pinion 7 of a rack and pinion mechanism by a universal joint 4.
The lower part, the middle part, and the upper part of the pinion shaft 5 are supported by bearings 6 a, 6 b and 6 c, and the pinion 7 is provided at the lower end part of the pinion shaft 5. The pinions 7 mesh with the rack teeth 8a of the rack shaft 8 that can reciprocate in the vehicle width direction, tie rods 9 are connected to the rack ends 8b provided at both ends of the rack shaft 8, and the front wheels as steered wheels are connected to the tie rods 9. 10 are linked. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 2 is steered, and the front wheels 10 and 10 can be steered to change the direction of the vehicle. Here, the rack shaft 8 and the tie rod 9 constitute a turning mechanism.

In addition, the electric power steering apparatus 100 includes a brushless motor (hereinafter abbreviated as a motor) 11 that generates a steering assist force for reducing the steering force by the steering wheel 2, and the torque generated by the motor 11 is reduced. It is boosted by the device 12 and transmitted to the pinion shaft 5. The speed reduction device 12 includes a worm gear 12a provided on the output shaft of the motor 11 and a worm wheel gear 12b provided on the pinion shaft 5 and meshing with the worm gear 12a.
The motor 11 includes a resolver (motor position detecting means) 14 for detecting a rotation angle, and the resolver 14 outputs an electric signal corresponding to the rotation angle of the motor 11 to a steering electronic control unit (ECU) 50.

In the pinion shaft 5, a magnetostrictive steering torque sensor (steering) that detects a steering torque (steering input) based on a change in magnetic characteristics caused by magnetostriction is provided between the intermediate bearing 6b and the upper bearing 6c. (Torque detection means, steering input detection means) 30 is arranged.
The steering torque sensor 30 includes two magnetostrictive films 31 and 32 provided on the outer peripheral surface of the pinion shaft 5, two detection coils 33 and 34 disposed opposite to the magnetostrictive films 31 and 32, and each detection coil 33, The detection circuits 35 and 36 are respectively connected to 34, and the detection circuits 35 and 36 convert changes in inductance of the detection coils 33 and 34 caused by magnetostriction into voltage changes and output them to the ECU 50. The ECU 50 calculates a steering torque that acts on the steering shaft 1 based on the outputs of the detection circuits 35 and 36.
The pinion shaft 5, the rack 8, the motor 11, and the speed reducer 12 are accommodated in the steering gear box 20.

A vehicle speed sensor 15 for detecting the vehicle speed is attached to an appropriate position of the vehicle body, and the vehicle speed sensor 15 outputs an electric signal corresponding to the vehicle speed to the ECU 50.
The ECU 50 determines a target current to be supplied to the motor 11 based on a control signal obtained by processing input signals from the resolver 14, the vehicle speed sensor 15, the steering torque sensor 30, and the like, and the current flowing through the motor 11 is the target current. By performing control (for example, PID control) so as to match, the output torque of the motor 11 is controlled, and the steering assist force is controlled.

Next, current control for the motor 11 in this embodiment will be described with reference to the control block diagram of FIG.
The ECU 50 includes a base current calculation unit 51, an inertia compensation current calculation unit 52, and a damper compensation current calculation unit 53.
The base current calculation unit 51 refers to a base current map (not shown) based on the steering torque detected by the steering torque sensor 30 and the vehicle speed detected by the vehicle speed sensor 15, and the base current corresponding to the steering torque and the vehicle speed. Is calculated. The base current map of this embodiment is set so that the gain of the base current increases as the steering torque increases, and the gain of the base current decreases and the dead zone increases as the vehicle speed increases. Is set to As a result, a firm feeling of steering torque is given as the vehicle speed increases.

Further, the steering torque detected by the steering torque sensor 30 is time-differentiated in the filter 54, and a time differential value of the steering torque is calculated.
The inertia compensation current calculation unit 52 refers to the inertia compensation current map (not shown) based on the time differential value of the steering torque output from the filter 54 and the vehicle speed detected by the vehicle speed sensor 15, and the time differential of the steering torque. The inertia compensation current according to the value and the vehicle speed is calculated. This inertia compensation current is a current that flows through the motor 11 in order to cancel the moment of inertia of the motor 11 and the steering system. The inertia compensation current map of this embodiment is set so that the gain of the inertia compensation current decreases as the vehicle speed increases.

The damper compensation current calculation unit 53 calculates a damper compensation current based on the rotation speed of the motor 11, the vehicle speed, and the steering angle of the steering wheel 2. The damper compensation current is an element that reduces the steering assist force by applying damping to the steering system.
The calculation of the damper compensation current in the damper compensation current calculation unit 53 will be described in detail. The damper compensation current calculation unit 53 includes a rotation speed calculation unit (steering speed detection unit) 61, a basic damper compensation current calculation unit (damper unit) 62, a steering angle calculation unit (steering angle detection unit) 63, and a damper ratio calculation unit (damper gain change). Means) 64.

  The rotation angle of the motor 11 detected by the resolver 14 is time-differentiated in a rotation speed calculation unit (steering speed detection means) 61, and a time differential value of the rotation angle, that is, the rotation speed of the motor 11 is calculated. In this electric power steering apparatus 100, since the output shaft of the motor 11 and the steering shaft 1 are connected by a speed reducer 12 (worm gear 12a and worm wheel gear 12b), the steering rotational speed of the steering wheel 2 is the rotation of the motor 11. Proportional to speed.

  The basic damper compensation current calculation unit 62 refers to the basic damper compensation current table shown in FIG. 3 based on the rotation speed of the motor 11 calculated by the rotation speed calculation unit 61 and the vehicle speed detected by the vehicle speed sensor 15. A basic damper compensation current corresponding to the rotational speed of the motor 11 and the vehicle speed is calculated. In the basic damper compensation current table shown in FIG. 3, the gain of the basic damper compensation current is set to continuously increase as the rotational speed of the motor 11 increases. That is, the damper gain of the basic damper compensation current is continuously increased as the steering speed increases.

  Further, in this electric power steering apparatus 100, the output shaft of the motor 11 and the steering shaft 1 are connected by the speed reducer 12, and the rotation angle (steering angle) of the steering wheel 2 is proportional to the rotation angle of the motor 11. The steering angle calculation unit 63 calculates the steering angle of the steering wheel 2 based on the rotation angle of the motor 11 detected by the resolver 14.

  The damper ratio calculation unit 64 refers to the damper ratio table shown in FIG. 4 based on the absolute value of the steering angle calculated by the steering angle calculation unit 63, and calculates the damper ratio (damper gain change rate) according to the absolute value of the steering angle. calculate. In the damper ratio table shown in FIG. 4, when the absolute value of the steering angle is zero (that is, the neutral point of the steering wheel 2), the damper ratio becomes the maximum value, and gradually increases in a linear function as the absolute value of the steering angle increases. Is set to decrease. In other words, the damper ratio is set to gradually increase as the steering angle decreases.

The damper compensation current calculator 53 calculates the damper compensation current by multiplying the basic damper compensation current calculated by the basic damper compensation current calculator 62 by the damper ratio calculated by the damper ratio calculator 64. That is, the gain (damper gain) of the damper compensation current is changed by multiplying the basic damper compensation current by the damper ratio.
Therefore, basically, the higher the vehicle speed and the higher the rotational speed (steering speed) of the motor, the larger the damper compensation current is set. However, the damper ratio set in accordance with the steering angle is multiplied. As a result, when the vehicle speed and the steering speed are the same, comparing when the steering angle is small and when the steering angle is small, the damper compensation current when the steering angle is small is larger than the damper compensation current when the steering angle is large Will be set to the value.

  Then, the ECU 50 adds the base current calculated by the base current calculation unit 51 and the inertia compensation current calculated by the inertia compensation current calculation unit 52, and subtracts the damper compensation current calculated by the damper compensation current calculation unit 53. Calculate the current. This target current is input to the drive circuit 56. In the drive circuit 56, for example, PID control is performed so that the current flowing through the motor 11 matches the target current, the output torque of the motor 11 is controlled, and the steering assist force is controlled. To do.

As described above, in this embodiment, basically, the higher the vehicle speed and the higher the motor rotation speed (steering speed), the larger the damper compensation current is set. Comparing when the steering angle is small and when the steering angle is small under the same condition, the damper compensation current when the steering angle is small is set to a value larger than the damper compensation current when the steering angle is large.
Therefore, when the steering system is returned to the neutral point by self-aligning torque or the like, the damper compensation current is set to be small in a region where the steering angle is large (that is, when the steering wheel 2 is away from the neutral point). So the steering returns quickly. Then, as the steering angle becomes smaller (that is, as the steering wheel 2 approaches the neutral point), the damper compensation current is set larger, so that the steering convergence is extremely improved. That is, in the electric power steering apparatus 100, it is possible to achieve both the return speed of the steering and the convergence of the steering.

Note that the damper ratio table is not limited to that shown in FIG. 4, and may be those shown in FIGS. 5 to 7, for example.
The damper ratio table shown in FIG. 5 is an example in which the damper ratio is set to gradually increase in a quadratic function as the absolute value of the steering angle decreases.
In the damper ratio table shown in FIG. 6, when the absolute value of the steering angle is equal to or smaller than a predetermined value, the damper ratio is set to a constant value. When the absolute value of the steering angle becomes larger than the predetermined value, the damper ratio decreases rapidly, and thereafter This is an example in which the degree of decrease in the damper ratio is set moderately.
In the damper ratio table shown in FIG. 7, the increase ratio of the damper ratio with respect to the decrease in the absolute value of the steering angle is larger than the area where the absolute value of the steering angle is greater than the predetermined value with the absolute value of the steering angle as a boundary. This is a set example.
The damper ratio tables shown in FIGS. 6 and 7 set the damper ratio (damper gain change rate) when the absolute value of the steering angle is equal to or smaller than a predetermined value to be larger than the damper ratio when the absolute value of the steering angle is larger than the predetermined value. It is an example of a damper ratio table.

  In the above-described embodiment, the steering angle is detected based on the output signal of the resolver 14 as the motor position detecting means, but an encoder can be used instead of the resolver 14. Further, the steering angle detecting means can be constituted by a steering angle sensor that detects the rotation angle of the steering wheel 2 or a rack stroke sensor that detects the stroke length of the rack shaft 8.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, the steering input detected by the steering input detection means is not limited to the steering torque, and a steering angle can also be adopted.
The electric steering device according to the present invention is not limited to the application to the electric power steering device of the above-described embodiment, and the present invention can also be applied to a steering device of a steer-by-wire system. The steer-by-wire system is a mechanism in which the steering wheel and other controls and the steering mechanism are mechanically separated, and a reaction force motor that applies a reaction force to the controls and a steering mechanism. And a steering motor that generates a force for turning the steered wheels.

It is a lineblock diagram of the electric steering device concerning this invention. It is a block diagram of the current control with respect to the motor of the said electric steering device. It is a figure which shows an example of a basic damper compensation current table. It is a figure which shows an example of a damper ratio table. It is a figure which shows the other example of a damper ratio table. It is a figure which shows another example of a damper ratio table. It is a figure which shows another example of a damper ratio table.

Explanation of symbols

10 Front wheels (steering wheels)
11 motor 14 resolver (motor position detecting means)
30 Steering torque sensor (steering input detection means)
61 Rotational speed calculation unit (steering speed detection means)
62 Basic damper compensation current calculation unit (damper means)
63 Steering angle calculation unit (steering angle detection means)
64 Damper ratio calculation unit (Damper gain changing means)
100 Electric power steering device (electric steering device)

Claims (3)

Steering input detection means for detecting steering input input to the steering system;
Steering angle detection means for detecting the steering angle of the steering system;
Steering speed detecting means for detecting the steering speed of the steering system;
Damper means for applying damping to the steering system based on the steering speed detected by the steering speed detection means,
In the electric steering device that drives the motor based on the steering input detected by the steering input detection means to steer the steered wheels,
Damper gain changing means for changing the damper gain of the damper means according to the steering angle detected by the steering angle detecting means is provided, and the damper gain changing means increases the damper gain as the steering angle decreases. Electric steering device. Steering input detection means for detecting steering input input to the steering system;
Steering angle detection means for detecting the steering angle of the steering system;
Steering speed detecting means for detecting the steering speed of the steering system;
Damper means for applying damping to the steering system based on the steering speed detected by the steering speed detection means,
In the electric steering device that drives the motor based on the steering input detected by the steering input detection means to steer the steered wheels,
Damper gain changing means for changing the damper gain of the damper means according to the steering angle detected by the steering angle detecting means, and the damper gain changing means determines the damper gain change rate when the steering angle is a predetermined value or less as the steering angle. The electric steering apparatus is set to be larger than a damper gain change rate when is larger than the predetermined value.   The electric steering apparatus according to claim 1 or 2, wherein the motor is a brushless motor, and the steering angle is detected by a motor position detection unit of the brushless motor.

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