JP2005313701A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of stabilizing control without using a torque sensor. <P>SOLUTION: In the power steering device, steering torque is estimated based on a value related to a detected steering angle, a target motor current of a steering auxiliary motor 1 is determined based on the estimated steering torque, and the steering auxiliary motor 1 is driven so that a detected motor current of the steering auxiliary motor 1 is to be the target motor current. The power steering device is provided with a motor output calculating means 27 for calculating output of the steering auxiliary motor 1 based on a rotary angular speed of the steering auxiliary motor 1 detected by a rotary angular speed detection means 13 and the motor current, a target motor output means 23 for determining target output of the steering auxiliary motor 1 based on the estimated steering torque, and a deviation calculating means 24 for calculating a deviation of the determined target output and the calculated output; and a target motor current determining means 25 determines the target motor current based on the calculated deviation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention estimates a steering torque based on a value related to a steering angle at which a steering shaft rotates, determines a target motor current of a steering assist motor based on the estimated steering torque, and the detected motor current is a target motor current. Thus, the present invention relates to an electric power steering apparatus that drives a steering assist motor.

Steering torque is estimated from the rudder angle, rudder angle and rudder angular speed, or rudder angle, rudder angular speed, and rudder angle acceleration with which the steering shaft is rotated, and the target motor current of the steering assist motor is determined based on the estimated steering torque. Patent Document 1 discloses an electric power steering device that does not use a torque sensor and drives a steering assist motor so that the current becomes a determined target motor current.
In this electric power steering device, a potentiometer that outputs a voltage signal V (θ) corresponding to the steering angle is used as the steering angle sensor, and the steering angular velocity ω (θ) is calculated from the difference of the voltage signal V (θ) for each sampling. The rudder angular acceleration α (θ) is obtained from the difference between the rudder angular velocities ω (θ) obtained for each sampling. Next, a theoretical value TE ′ of the torque TE for turning the steering wheel is calculated by the equation (1).

TE ′ = J · Gr · (d / dt) · ω (θ)
= J · Gr · (d / dt) · α (θ) (1)
Here, J is the moment of inertia of the armature of the steering assist motor, and Gr is the gear ratio of the speed reduction mechanism of the steering assist motor.
The torque that a theoretical person overcomes the disturbance torque of a tire and turns the steering wheel
TA ′ = TE ′ − (KT × I) (2)
Thus, TA ′ is the estimated steering torque. Here, KT is a motor torque constant, and I is a motor current.
Japanese Patent No. 2969701 Japanese Patent Laid-Open No. 11-59447

  In the electric power steering apparatus described above, the steering angle is also operated by the steering assist motor. However, since the steering angle is not included in the feedback signal KT × I, the control may be unstable. There is.

The present invention has been made in view of the circumstances as described above, and it is an object of the first invention to provide an electric power steering apparatus that is stable in control and does not use a torque sensor.
It is an object of the second invention to provide an electric power steering apparatus that does not require direct detection of the rotational angular velocity of the steering assist motor, that is stable in control, and that does not use a torque sensor.

  An electric power steering apparatus according to a first aspect of the present invention is a steering angle detection means for detecting a steering angle of a steering shaft, a torque estimation means for estimating a steering torque based on a value related to the steering angle detected by the steering angle detection means A target motor current determining means for determining a target motor current of the steering assist motor based on the steering torque estimated by the torque estimating means; and a motor current detecting means for detecting the motor current of the steering assist motor, In the electric power steering apparatus that drives the steering assist motor so that the motor current detected by the motor current detection means becomes the target motor current determined by the target motor current determination means, the rotation of the steering assist motor is performed. Rotational angular velocity detection means for detecting angular velocity, rotational angular velocity detected by the rotational angular velocity detection means, and detected by the motor current detection means Motor output calculation means for calculating the output of the steering assist motor based on the motor current, target motor output determination means for determining the target output of the steering assist motor based on the steering torque, and the target motor output determination A target output determined by the means, and a deviation calculation means for calculating a deviation of the output calculated by the motor output calculation means, the target motor current determination means based on the deviation calculated by the deviation calculation means It is characterized in that the motor current is determined.

  The electric power steering apparatus according to a second aspect of the invention is characterized in that the rotational angular velocity detection means detects a rotational angular velocity of the steering assist motor based on a value related to the steering angle.

  According to the electric power steering apparatus according to the first aspect of the present invention, it is possible to realize an electric power steering apparatus that is stable in control and does not use a torque sensor.

  According to the electric power steering apparatus according to the second aspect of the present invention, it is possible to realize an electric power steering apparatus that is stable in control and does not use a torque sensor. In addition, a sensor for directly detecting the rotational angular velocity of the steering assist motor is not required, and it is possible to reduce the size and the cost of parts.

Hereinafter, the present invention will be described with reference to the drawings showing embodiments thereof.
(Embodiment 1)
FIG. 1 is a schematic diagram showing a main configuration of the electric power steering apparatus according to Embodiment 1 of the present invention. This electric power steering device includes, for example, a steering wheel (steering member) 7 for steering, a steering assisting electric motor 1 driven in accordance with the steering of the steering wheel 7, and a reduction gear mechanism for rotating the electric motor 1. 2 is provided with transmission means 4 for transmitting to the steering mechanisms 3 and 3 via 2 and a control unit 6 for controlling the drive circuit 5 of the electric motor 1.

The electric motor 1 is provided with a motor rotation angular velocity sensor (rotation angular velocity detection means) 13 for detecting the rotation angular velocity, and a motor current sensor 26 for detecting a motor current flowing in the electric motor 1, and the rotation angular velocity detected by each of them. The motor current is supplied to the control unit 6.
The steering wheel 7 is connected to a steering shaft 8, and the transmission means 4 is connected to a steering shaft 8, a pinion shaft 11 connected to the steering shaft 8 via a connecting shaft 9 such as a universal joint, and a pinion of the pinion shaft 11. The rack shaft 12 has rack teeth that mesh with each other and is connected to the left and right steered wheels A and A via the steering mechanisms 3 and 3.

A steering angle sensor (steering angle detection means) 10 that detects the rotation angle (steering angle) is provided at the tip of the pinion shaft 11, and the steering angle detected by the steering angle sensor 10 is given to the control unit 6. The control unit 6 is also provided with a detection signal from a speed sensor 14 that detects the speed of the vehicle.
The reduction gear mechanism 2 includes a worm (not shown) connected to the output shaft of the electric motor 1 and a worm wheel (not shown) fitted in the middle of the steering shaft 8. The transmission is transmitted to the steering shaft 8 at a reduction ratio Gr.

  In the electric power steering apparatus having such a configuration, the steering operation force by the operation of the steered wheels 7 is transmitted to the rack shaft 12 via the steering shaft 8, the connecting shaft 9, and the pinion shaft 11, and the rack shaft 12 is moved in the axial direction. And the steering mechanisms 3 and 3 are operated. At the same time, the controller 6 controls the drive circuit 5 to drive the electric motor 1 based on the detected steering angle, motor rotation angular velocity, and motor current, and the driving force of the electric motor 1 is applied to the steering shaft 8. By transmitting, the steering operation force is assisted and the driver's labor burden for steering is reduced.

  FIG. 2 is a block diagram showing a configuration example of a main part of the electric power steering apparatus shown in FIG. In this electric power steering apparatus, the control unit 6 is given a voltage signal V (θ) corresponding to the steering angle θ detected by the steering angle sensor 10 as a potentiometer, and the steering angular velocity acceleration calculation unit 20 receives V (θ). = Steering angular velocity θ ′ and steering angular acceleration θ ″ are calculated as = θ. The calculated steering angular velocity θ ′ and steering angular acceleration θ ″ are given to the target motor output control unit 21.

The target motor output controller 21 includes a steering torque estimator 22 and a target motor output determiner 23. The steering torque estimator 22 calculates and estimates the steering torque T (θ) according to the equation (1). This is given to the output determination unit 23. The target motor output determination unit 23 includes a table indicating the relationship between the steering torque, the vehicle speed, and the target motor output Wobj (motor current × motor torque constant × motor rotational angular velocity), and the given estimated steering torque T (θ), Based on the vehicle speed signal given from the vehicle speed sensor 14, the target motor output Wobj is determined and output.
The target motor output Wobj output by the target motor output determining unit 23 is given to the deviation calculating means 24.

On the other hand, the motor rotation angular velocity θm ′ of the electric motor 1 detected by the motor rotation angular velocity sensor 13 and the motor current Im of the electric motor 1 detected by the motor current sensor 26 are given to the motor output calculation unit 27, and the motor output calculation unit 27 calculates the motor output Wm (motor current Im × motor torque constant × motor rotational angular velocity θm ′) and gives it to the deviation calculating means 24.
The deviation calculating means 24 calculates the deviation between the given target motor output Wobj and the motor output Wm, and gives it to the target motor current determining unit 25. The target motor current determination unit 25 includes a table indicating the relationship between the target motor output Wobj and the deviation of the motor output Wm and the target motor current Iobj of the electric motor 1, and based on the given deviation, the target motor current Iobj is obtained. It is determined and given to the deviation calculating means 28.

The deviation calculating means 28 is also supplied with the motor current Im from the motor current sensor 26, calculates the deviation between the target motor current Iobj and the motor current Im, and supplies it to the motor current control unit 29.
The motor current control unit 29 determines the duty ratio of the PWM control based on the given deviation, performs PWM control of the drive circuit 5 with the determined duty ratio, and drives the electric motor 1.

Hereinafter, an operation related to motor driving of the electric power steering apparatus having such a configuration will be described with reference to a flowchart of FIG.
First, the control unit 6 samples and reads the voltage signal V (θ) corresponding to the steering angle θ detected by the steering angle sensor 10 in the steering angular velocity acceleration calculation unit 20 (S2). Next, the steering angular velocity θ ′ = ω (θ), which is the difference between the voltage signal Vb (θ) sampled and read last time, and the voltage signal V (θ) is calculated (S4). Next, the angular acceleration θ ″ = α (θ), which is the difference between the previously calculated steering angular velocity ωb (θ) and the steering angular velocity ω (θ), is calculated (S6).

Next, the control unit 6 calculates and estimates the steering torque T (θ) using the equation (1) by the steering torque estimation unit 22 (S8), and calculates the target by using the estimated steering torque T (θ) and the vehicle speed signal. The motor output determination unit 23 refers to the table to determine the target motor output Wobj (S10).
Next, the controller 6 reads the motor current Im from the motor current sensor 26 (S12) and reads the motor rotational angular velocity θm ′ of the electric motor 1 from the motor rotational angular velocity sensor 13 (S13). . Next, the motor output calculation unit 27 calculates the motor output Wm (motor current Im × motor torque constant × motor rotation angular velocity θm ′) (S14).

Next, the control unit 6 calculates the deviation Wd = Wobj−Wm by the deviation calculating means 24 (S16), and the target motor current determining unit 25 determines the target motor current Iobj by referring to the table by the deviation Wd. (S18).
Next, the control unit 6 calculates the deviation Id = Iobj−Im by the deviation calculating means 28 (S20), and the motor current control unit 29 determines the duty ratio of the PWM control based on the deviation Id (S22). Then, the drive circuit 5 is subjected to PWM control with the determined duty ratio to drive the electric motor 1 (S24) and return.

(Embodiment 2)
FIG. 4 is a block diagram showing the main configuration of Embodiment 2 of the electric power steering apparatus according to the present invention. In the second embodiment, the control unit 6 includes a motor rotation angular velocity calculation unit 30 (rotation angular velocity detection unit) instead of the motor rotation angular velocity sensor 13 as the rotation angular velocity detection unit.

  The motor rotation angular velocity calculation unit 30 is provided with the steering angular velocity θ ′ from the steering angular velocity acceleration calculation unit 20 and calculates a motor rotation angular velocity θm′≈θ ′ × Gr (Gr: reduction ratio of the reduction gear mechanism 2). This is given to the output calculation unit 27. Thereby, it is not necessary to provide the motor rotation angular velocity sensor 13, and it is possible to reduce the size and the cost of parts. Since other configurations and operations are the same as the configurations and operations of the electric power steering apparatus according to the present invention described in the first embodiment, the description thereof will be omitted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a main configuration of an embodiment of an electric power steering apparatus according to the present invention. It is a block diagram which shows the principal part structural example of the electric power steering apparatus shown in FIG. It is a flowchart which shows the operation | movement which concerns on the motor drive of the electric power steering apparatus which concerns on this invention. It is a block diagram which shows the principal part structure of embodiment of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Reduction gear mechanism 5 Drive circuit 6 Control part 7 Steering wheel (steering member)
8 Steering shaft 10 Steering angle sensor (steering angle detection means)
13 Motor rotation angular velocity sensor (rotation angular velocity detection means)
DESCRIPTION OF SYMBOLS 20 Steering angular velocity acceleration calculating part 21 Target motor output control part 22 Steering torque estimation part 23 Target motor output determination part 24,28 Deviation calculation means 25 Target motor current determination part 26 Motor current sensor 27 Motor output calculation part 29 Motor current control part 30 Motor rotation angular velocity calculation unit (rotation angular velocity detection means)

Claims (2)

Steering angle detection means for detecting the steering angle of the steering shaft, torque estimation means for estimating steering torque based on a value related to the steering angle detected by the steering angle detection means, and the steering torque estimated by the torque estimation means Based on the target motor current determining means for determining the target motor current of the steering assist motor, and the motor current detection means for detecting the motor current of the steering assist motor, and the motor current detected by the motor current detection means is determined. In the electric power steering apparatus for driving the steering assist motor so as to achieve the target motor current determined by the target motor current determining means,
Based on the rotational angular velocity detected by the rotational angular velocity detecting means, the rotational angular velocity detected by the rotational angular velocity detecting means, and the motor current detected by the motor current detecting means, the output of the steering auxiliary motor is obtained. Motor output calculating means for calculating; target motor output determining means for determining a target output of the steering assist motor based on the steering torque; target output determined by the target motor output determining means; and the motor output calculating means Deviation calculating means for calculating a deviation of the calculated output, wherein the target motor current determining means is adapted to determine the target motor current based on the deviation calculated by the deviation calculating means. Electric power steering device.   2. The electric power steering apparatus according to claim 1, wherein the rotational angular velocity detection means detects a rotational angular velocity of the steering assist motor based on a value related to the steering angle.

Images