Power steering control apparatus for motor vehicle

• US 6,009,364 A
• Filed: 10/05/1993
• Issued: 12/28/1999
• Est. Priority Date: 10/09/1992
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Tsutsumi, Kazumichi, Naitou, Yasuo, Wada, Shunichi
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/131,684
• Time in Patent Office: 2,275 Days
• Field of Search: 364/424.05, 364/424.01, 364/426.03, 364/426.02, 180/79.1, 180/141, 180/142, 180/443, 180/408, 180/411, 303/95, 303/109, 701/41, 701/71, 701/74, 701/80, 701/84
• US Class Current: 701/43
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear
• CPC Class Codes: B60T 8/885 using electrical circuitry
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 6/00 Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits means for initiating a change in direction B62D1/00; steering valves B62D5/06; combined with means for inclining the vehicle body or wheels on bends B62D9/00
• CPC Class Codes: B62D 6/006 using a measured or estimated road friction coefficient
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications

Abstract

A power steering control apparatus for a motor vehicle which ensures an appropriate steering force conforming to the prevailing road condition and hence the safety for the motor vehicle even when the wheels are locked due to hard brake applied on a slippery road. The apparatus includes a first microcomputer for determining a driving torque of a steering assist motor on the basis of steering torque information generated upon steering of a steering wheel and pseudo vehicle speed information to thereby generate and output a driving signal for the steering assist motor on the basis of the driving torque, and a second microcomputer for generating the pseudo vehicle speed signal on the basis of wheel rotation speed signals and acceleration/deceleration signal of the motor vehicle to thereby generate and output a brake actuation signal for wheels of the motor vehicle on the basis of the pseudo vehicle speed signal, the acceleration/deceleration information and brake application information. The first microcomputer may further include a memory for storing steering assist characteristics according to which the torque of the assist motor is changed.

Claims

1. A power steering control apparatus for a motor vehicle, comprising:

first control means for determining a driving torque for a steering assist motor on the basis of steering torque information, indicative of a steering torque of a steering wheel generated upon operation of the steering wheel by a driver of the motor vehicle, and pseudo vehicle speed information indicative of an estimated vehicle speed, and then generating a driving signal for said steering assist motor on the basis of said driving torque; and

second control means for generating said pseudo vehicle speed information indicative of an estimated speed of said motor vehicle which is calculated on the basis of wheel rotation speed information indicative of a rotation speed of wheels of said motor vehicle and acceleration/deceleration information of said motor vehicle indicative of an acceleration/deceleration of said motor vehicle, said second control means also generating a brake actuation signal for said wheels of said motor vehicle on the basis of said pseudo vehicle speed signal, said acceleration/deceleration information, and brake application information indicative of brake application by a driver of the motor vehicle;

wherein said second control means comprises a part of an anti-skid brake system for said motor vehicle;

and wherein said anti-skid brake system includes a vehicle speed estimating circuit for generating said pseudo vehicle speed information on the basis of outputs of rotation speed sensors which are provided in association with wheels of said motor vehicle for detecting rotation speeds thereof, respectively, and an output signal of a deceleration/acceleration sensor for detecting a deceleration/acceleration of said motor vehicle;

and wherein said pseudo vehicle speed information defines a locking state and a ready-to-lock state of the wheels of said motor vehicle, and said first control means decreases said driving torque in response to the pseudo vehicle speed information which indicates a locking state or alternatively a ready-to-lock state of the wheels of said motor vehicle.

2. A power steering control apparatus for a motor vehicle comprising:

first control means for determining a driving torque of a steering assist motor on the basis of steering torque information, which is generated upon steering of a steering wheel and indicative of a steering torque imparted to said steering wheel by a driver of said motor vehicle, and vehicle speed information to thereby generate a driving signal for said steering assist motor on the basis of said driving torque;

second control means for generating a brake actuation signal for wheels of said motor vehicle on the basis of wheel rotation speed information and brake application effort detection information indicative of brake application by a driver of the motor vehicle;

road friction coefficient estimating means for estimating coefficient of friction of a road surface on the basis of said wheel rotation speed information;

means for storing a plurality of said steering control data representing relations between a motor current and a driving torque of said steering assist motor by using predetermined road friction coefficients as parameters; and

means for changing said steering control data in dependence on the road friction coefficient estimated by said road coefficient estimating means by referencing said storing means;

wherein said first control means comprises a plurality of steering control data, each of which being changed for correspondingly controlling said steering assist motor in response to said brake actuation application signal output from said second control means;

and wherein said first control means comprises a plurality of steering control data, and whereby the friction coefficient of the road surface estimated by said road friction coefficient estimating means is communicated to said first control means to correspondingly change said steering control data.