Electric power steering apparatus and control method thereof

Patent metadata

Field	Value
Publication number	US-11524717-B2
Application number	US-201916556337-A
Country	US
Kind code	B2
Filing date	Aug 30, 2019
Priority date	Sep 5, 2018
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

An electric power steering apparatus and a control method thereof. A motor includes a first motor providing power to move a rack and a second motor providing power to move the rack in synchronization with the first motor. A sensor includes a torque angle sensor detecting a torque value and a steering angle in response to manipulation of a steering wheel and an angle sensor detecting an angle of rotation of a sector shaft. A controller controls the motor in response to the manipulation of the steering wheel, calculates an amount of compensation rotation of the motor by comparing the steering angle and the angle of rotation, and controls an amount of rotation of the motor in accordance with an amount of compensation rotation. The amount of rotation of a vehicle's wheel is controlled, so that actual intention of the driver in steering is accurately reflected.

First claim

What is claimed is:

1. An electric power steering apparatus comprising:
a motor comprising a first motor coupled to a worm wheel of a steering shaft and configured to rotate the worm wheel to move a rack and a second motor coupled to the worm wheel of the steering shaft and configured to rotate the worm wheel to move the rack in synchronization with the first motor;
a sensor comprising a torque angle sensor configured to detect a torque value and a steering angle in response to manipulation of a steering wheel and an angle sensor configured to detect an angle of rotation of a sector shaft; and
a controller configured to control the first and second motors, respectively, in response to the manipulation of the steering wheel,
wherein the controller is configured to calculate an amount of compensation rotation of the motor based on the detected steering angle and the detected angle of rotation, and control an amount of rotation of the motor in accordance with the calculated amount of compensation rotation, and
wherein the controller is configured to,
when the calculated amount of compensation rotation is less than a predetermined value, only drive the first motor to move the rack in accordance with the calculated amount of compensation rotation, and
when the calculated amount of compensation rotation is equal to or greater than the predetermined value, drive both of the first motor and the second motor to move the rack in accordance with the calculated amount of compensation rotation.

2. The electric power steering apparatus according to claim 1 , wherein the motor is driven to transfer power to a ball screw of a second reducer having a power transmission structure comprised of the ball screw and a ball nut via a first reducer having a power transmission structure provided by engagement of worm gears and a worm wheel, so that the power is transferred to the rack.

3. The electric power steering apparatus according to claim 2 , wherein the torque angle sensor is connected to the steering shaft, in a location between the steering wheel and the first reducer, to detect the torque value and the steering angle due to torsion and rotation of the steering shaft.

4. The electric power steering apparatus according to claim 2 , wherein the angle sensor is disposed on the sector shaft to detect the angle of rotation of the sector shaft, the sector shaft rotating in response to sliding of the ball nut of the second reducer.

5. The electric power steering apparatus according to claim 4 , wherein the angle sensor includes:
one or more magnets disposed on surface portions of a sector gear provided on an outer circumferential surface of the sector shaft to be engaged with the ball nut; and
a magnetic sensor detecting magnetic force generated by the magnets, response to the sector gear rotating along with the sliding of the ball nut.

6. The electric power steering apparatus according to claim 5 , the magnetic sensor disposed in a housing to face the magnets, the housing surrounding the sector shaft and the sector gear.

7. The electric power steering apparatus according to claim 1 , wherein the controller configured to calculate a first amount of rotation of a vehicle's wheel in accordance with the detected steering angle and a second amount of rotation of the vehicle's wheel in accordance with the detected angle of rotation, calculate the amount of compensation rotation by comparing the first amount of rotation and the second amount of rotation, and apply a compensation current based on the amount of compensation rotation to the motor.

8. The electric power steering apparatus according to claim 7 , wherein the controller is configured to perform position control to the motor by proportional integral control.

9. A control method of an electric power steering apparatus of a vehicle, the method comprising:
controlling a motor in response to manipulation of a steering wheel, wherein the motor comprising a first motor coupled to a worm wheel of a steering shaft and configured to rotates the worm wheel to move a rack and a second motor coupled to the worm wheel of the steering shaft and configured to rotate the worm wheel to move the rack in synchronization with the first motor;
detecting a torque value and a steering angle in response to the manipulation of the steering wheel;
detecting an angle of rotation of a sector shaft;
calculating an amount of compensation rotation of the motor by comparing the steering angle and the angle of rotation; and
controlling, in accordance with the amount of compensation rotation, a first amount of rotation of the first motor and a second amount of rotation of the second motor, respectively
wherein the controller,
when the calculated amount of compensation rotation is less than a predetermined value, only drives the first motor to move the rack in accordance with the calculated amount of compensation rotation, and
when the calculated amount of compensation rotation is equal to or greater than the predetermined value, drives both of the first motor and the second motor to move the rack in accordance with the calculated amount of compensation rotation.

10. The control method according to claim 9 , wherein the detection of the torque value and the steering angle comprises detecting the torque value and the steering angle in response to torsion and rotation of the steering shaft.

11. The control method according to claim 10 , wherein the detection of the angle of rotation of the sector shaft comprises detecting the angle of rotation of the sector shaft by detecting magnetic force generated by one or more magnets disposed on the sector shaft.

12. An electric power steering apparatus comprising:
a motor comprising a first motor coupled to a worm wheel of a steering shaft and configured to rotate the worm wheel to move a rack and a second motor coupled to the worm wheel of the steering shaft and configured to rotate the worm wheel to move the rack in synchronization with the first motor;
a sensor comprising a vehicle speed sensor configured to obtain a vehicle speed of a host vehicle, a steering angle sensor configured to obtain a steering angular velocity due to manipulation of a steering wheel, and a front sensor configured to obtain a distance to a preceding vehicle; and
a controller configured to control an operation of the first motor and an operation of the second motor, respectively, so that the vehicle's wheel is steered in response to the manipulation of the steering wheel,
wherein the controller is configured to:
determine a normal mode and an emergency mode to drive the motor in accordance with at least one selected from among the vehicle speed, the steering angular velocity, the distance to a preceding vehicle, or combinations thereof,
only drive the first motor in the normal node, and
drive both the first motor and the second motor in an emergency mode.

13. The electric power steering apparatus according to claim 12 , wherein the motor is configured to drive to transfer power to a ball screw of a second reducer having a power transmission structure comprised of the ball screw and a ball nut via a first reducer having a power transmission structure provided by engagement of worm gears and a worm wheel, so that the power is transferred to the rack.

14. The electric power steering apparatus according to claim 13 , wherein the sensor further comprises an angle sensor disposed on a sector shaft to detect an angle of rotation of the sector shaft, the sector shaft rotating in response to sliding of the ball nut.

15. The electric power steering apparatus according to claim 14 , wherein th

Assignees

• Mando Corp

Inventors

• Kim Jung-Yeol

Classifications

• B62D5/046

  Controlling the motor · CPC title

• B62D3/06

  with screw and nut · CPC title

• B62D15/021

  Determination of steering angle · CPC title

• B62D5/04

  electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear · CPC title

• B62D6/002

  computing target steering angles for front or rear wheels (B62D7/159 takes precedence) · CPC title