Electric power steering control apparatus

• US 5,878,360 A
• Filed: 06/07/1995
• Issued: 03/02/1999
• Est. Priority Date: 06/09/1994
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Takatsuka, Yuji, Wada, Shunichi, Nishino, Kazuhisa
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/474,653
• Time in Patent Office: 1,364 Days
• Field of Search: 364/44.051, 364/424.052, 180/6.28, 180/443, 180/446, 180/412, 180/413, 180/415, 180/421, 180/422, 180/423, 180/444, 701/41, 701/42
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0466 for returning the steering wheel to neutral position

Abstract

An electric power steering control apparatus is intended to improve the convergence and control stability of a returning motion of a steering wheel when a driver of a vehicle on which the apparatus is installed lets his or her hands free from the steering wheel, and to reduce a burden to the driver when an excessive steering torque occurs during the returning motion. The apparatus includes a steering torque sensor 8 for detecting a steering torque of a steering system of the vehicle, a motor rotational-speed detector 7 for detecting a rotational speed of the electric motor, and a rotational-speed controller for controlling the electric motor based on output signals from the steering torque sensor and the motor rotational-speed sensor so that when the steering torque as detected is less than a predetermined torque value, the rotational speed of the electric motor does not exceed a predetermined speed value corresponding to the predetermined torque value.

Claims

1. An electric power steering control apparatus comprising:

a steering torque sensor for detecting a steering torque of a steering system of a vehicle and generating a corresponding output signal;

a D.C. motor having a pair of terminals for generating a power assisting force to reduce a steering force of a driver of the vehicle required to be imparted to said steering system;

motor drive means for driving said electric motor in a direction of reducing said driver'"'"'s steering force according to at least the output signal of said steering torque sensor;

motor rotational-speed estimating means for estimating the rotational speed of said motor from an electromotive force generated when the terminals of said D.C. motor are opened; and

control means for alternatively operating said motor drive means to drive said motor and said motor rotational-speed estimating means to estimate the motor-rotational speed when said steering torque is less than a predetermined torque value, so that said estimated rotational speed of said motor does not exceed a predetermined speed value.

2. An electric power steering control apparatus comprising:

a steering torque sensor for detecting a steering torque of a steering system of a vehicle and generating a corresponding output signal;

a vehicle speed sensor for detecting a speed of the vehicle and generating a corresponding output signal;

a D.C. motor having a pair of terminals for generating a power assisting force to reduce a steering force of a driver of the vehicle required to be imparted to said steering system;

motor drive means for driving said electric motor in a direction of reducing said steering force according to at least the output signal of said steering torque sensor;

motor rotational-speed detection means for detecting a rotational speed of said electric motor and generating a corresponding output signal;

motor rotational-direction detection means for detecting a direction of rotation of said electric motor; and

drive-quantity control means for determining a quantity of drive of said motor from at least one of the vehicle speed and the motor rotational speed, drive-quantity control means being operable to drive said electric motor in a direction opposite to said direction of rotation thereof detected by said motor rotational-direction detection means by said quantity of drive when said steering torque is less than a predetermined value.

3. An electric power steering control apparatus comprising:

a steering torque sensor for detecting a steering torque of a steering system of a vehicle and generating a corresponding output signal;

a vehicle speed sensor for detecting a speed of the vehicle and generating a corresponding output signal;

a D.C. motor having a pair of terminals for generating a power assisting force to reduce a steering force of a driver of the vehicle required to impart to said steering system;

motor drive means for driving said electric motor in a direction of reducing said driver'"'"'s steering force according to at least the output signal of said steering torque sensor;

motor rotational-speed estimating means for estimating the rotational speed of said motor from an electromotive force generated when the terminals of said D.C. motor are opened;

motor rotational-direction estimating means for estimating the rotational direction of said motor from an electromotive force generated when the terminals of said D.C. motor are opened; and

control means for alternatively operating said motor drive means to drive said motor and said motor rotational-speed estimating means to estimate the motor rotational speed and determining a quantity of drive of said motor from at least one of the vehicle speed and the estimated motor rotational speed when said steering torque is less than a predetermined value, so that motor is thereby driven to rotate in a direction opposite to said direction of rotation thereof detected by said motor rotational-direction detection means by said quantity of drive.

4. An electric power steering control apparatus comprising:

a steering torque sensor for detecting a steering torque of a steering system of a vehicle and generating a corresponding output signal;

a vehicle speed sensor for detecting a speed of the vehicle and generating a corresponding output signal;

a D.C. motor having a pair of terminals for generating a power assisting force to reduce a steering force of a driver of the vehicle required to impart to said steering system;

motor drive means for driving said electric motor in a direction of reducing said driver'"'"'s steering force according to at least the output signal of said steering torque sensor;

motor rotational-speed estimating means for estimating the rotational speed of said motor from an electromotive force generated when the terminals of said D.C. motor are opened;

duty-ratio decision means for deciding a duty ratio from at least one of the output signals of said motor rotational-speed estimating means and said vehicle speed sensor when said steering torque is less than a predetermined value; and

control means for short-circuiting said motor according to a PWM signal of said duty ratio decided by said duty-ratio decision means, said control means being operable to alternatively perform short-circuiting of said motor and operate said motor rotational-speed estimating means to estimate said motor-rotational speed.