KR20110075904A

KR20110075904A - Motor control method for motor driven power steering system

Info

Publication number: KR20110075904A
Application number: KR1020090132476A
Authority: KR
Inventors: 김령태
Original assignee: 현대모비스 주식회사
Priority date: 2009-12-29
Filing date: 2009-12-29
Publication date: 2011-07-06

Abstract

PURPOSE: A motor control method of a motor driven power steering system is provided to improve operational convenience, steering feel, operating stability of a steering handle by varying an auxiliary torque of a motor when a vehicle travels on an inclined road and providing the optimum steering assistant force. CONSTITUTION: A motor control method of a motor driven power steering system comprises the steps of: sensing a tilt angle of a chassis using a tilt angle sensor while a vehicle is running(S10); operating a gradient of a road surface on the basis of the sensed tilt angle, judging whether or not the operated gradient is an upward gradient, and if the gradient of the road surface is an upward gradient, reducing a motor torque inversely proportional to the size of the gradient(S20~S50); and if the gradient of the road surface is a downward gradient, increasing the motor torque proportional to the size of the gradient(S60).

Description

Motor control method for motor driven power steering system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus, and more particularly, to a motor control method of an electric power steering apparatus for varying steering torque compensation torques according to slopes of a driving road to improve steering feeling and steering stability.

Conventionally, as a steering device of a vehicle, a power steering device for assisting a steering force of a driver's steering wheel is widely used, and the power steering device has been generally applied to a hydraulic power steering device for generating hydraulic pressure to assist a driver's steering force. Recently, an eco-friendly electric power steering device is used to assist the driver's steering force by using the rotational force of the motor.

The electric power steering device drives the motor according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering angle sensor, so that the steering assistance force is increased while the steering wheel becomes lighter at the low speed of the vehicle. When driving, the steering assistance power is reduced so that the maneuvering power of the steering becomes heavy, and the driving stability is promoted, and in case of emergency, the steering assistance is always provided so that the steering assistance is optimally provided to the driver.

The electric power steering device as described above has a worm wheel gear integrally mounted to a steering column connected to the steering handle to be integrally rotated, and a worm gear is engaged to rotate the worm wheel gear, and the worm gear rotates to a drive motor. When the driver rotates the steering wheel, the motor generates a rotational torque to transmit power to the steering column through the worm gear and the worm wheel gear to assist the driving force of the driver's steering wheel. do.

1 shows a hardware configuration of a motor control method of an electric power steering apparatus according to the prior art. In order to detect driving information of a vehicle, a motor control unit (MCU) includes a battery voltage, a vehicle speed, The engine rotation speed and steering angle are read from each sensor, and the detected information is internally generated and applied to the driving motor by generating a motor control signal according to the programmed logic. The driving motor generates steering auxiliary torque. It assists the driver's steering wheel steering.

However, in the conventional motor control method of the electric power steering apparatus as described above, proper torque compensation according to the inclination of the road surface has not been achieved. In other words, when the driving surface is uphill, the steering weight becomes lighter because the weight of the vehicle is pulled backwards, whereas when the driving surface is downhill, the steering force becomes heavy because the weight of the vehicle is tilted forward. There was a drawback that the optimum steering assistance was not achieved because the auxiliary torque of the motor was not properly controlled according to the inclined conditions.

Accordingly, the present invention has been made in view of the above circumstances, and when the vehicle travels on a sloped road, unlike the case of flat driving, the auxiliary torque of the motor is varied to provide an optimum steering assistance force, thereby providing convenience in operating the steering wheel. It is an object of the present invention to provide a motor control method of an electric power steering apparatus that can improve steering control and steering stability.

The present invention for achieving the above object is to determine the inclination of the road surface by the inclination angle sensor while the vehicle is running, and to reduce the motor torque for providing steering assistance to the steering wheel when the inclination of the road surface is inclined upward. On the other hand, when the slope is inclined, the motor is controlled to increase the motor torque.

Preferably, the criterion for determining the inclination of the road surface is 5 m or more when the slope is upward, and -5 m or less when the slope is downward.

According to the motor control method of the electric power steering apparatus according to the present invention, the battery voltage and the vehicle speed, the engine speed, the steering angle and the inclination angle are detected and read through the respective sensors while the vehicle is traveling, and the driving detected by the inclination angle sensor When the road is on an inclined road, the motor torque is reduced, whereas when the road is on an inclined road, the motor torque is increased to provide optimum steering assistance torque according to the inclination of the road surface. There is an effect such as to improve the feeling of operation.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the accompanying drawings.

2 shows a hardware configuration for implementing the motor control method of the electric power steering apparatus according to the present invention, that is, the motor controller (MCU) is a battery voltage, vehicle speed, engine speed, The steering angle and the inclination angle are read and detected through the respective sensors, and the motor control signal is generated and applied to the MDPS drive motor based on the information read as described above according to the logic already programmed therein, and the drive motor is applied to the applied control. By acting on a signal, it generates the appropriate auxiliary torque and transmits it through the worm gear to the worm wheel gear, thereby assisting the driver when operating the steering wheel.

3 is a flow chart of the motor control method of the electric power steering apparatus according to the present invention, that is, the motor control device detects the inclination angle of the vehicle body through the inclination angle sensor while driving the vehicle (S10), so detected The inclination of the driving road surface is calculated based on the inclination angle (S20), and it is determined whether the calculated inclination is a predetermined inclination, for example, 5 m or more (uphill) (S30).

When the slope of the road surface determined in the above step is 5 ㅀ or more, the motor torque is reduced in inverse proportion to the magnitude of the slope (S40), and when the slope of the road surface is determined to be −5 ㅀ or less (downhill) (S50). The motor torque is increased in proportion to the size (S60).

As described above, the compensating motor torque is calculated by reflecting the increase / decrease value of the motor torque according to the slope of the road (S70), and the motor control signal is generated and applied to the driving motor according to the above. Optimal steering assistance is provided according to the inclination to improve the convenience of driving operation, and to improve steering stability and steering operation feeling.

On the other hand, the criterion for determining the inclination of the road surface is set to 5 ㅀ, or -5 ㅀ in the present invention, of course, the slope of the road surface can be determined based on more or less.

1 is a motor control configuration diagram of an electric power steering apparatus according to the prior art;

2 is a motor control configuration diagram of the electric power steering apparatus according to the present invention;

3 is a motor control flowchart of the electric power steering apparatus according to the present invention.

Claims

While driving the vehicle, the inclination of the road surface is determined by the inclination sensor, and when the inclination of the road is inclined upward, the motor torque that provides steering assistance to the steering wheel is reduced, while in the inclined direction, the motor torque is increased. Motor control method of an electric power steering system for controlling the motor to control the motor.

The motor control method of an electric power steering apparatus according to claim 1, wherein the criterion for determining the slope of the road surface is 5 kW or more when the slope is upward, and -5 kPa or less when the slope is downward.

The motor of the electric power steering apparatus of claim 2, wherein the worm wheel gear is integrally mounted to the steering handle, the worm gear is engaged with the worm wheel gear, and the motor is connected to the worm gear so as to transmit torque. Control method.