Control apparatus for electric power steering system

• US 20040056614A1
• Filed: 01/27/2003
• Published: 03/25/2004
• Est. Priority Date: 02/04/2002
• Status: Active Grant

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Kobayashi, Hideyuki
• Granted Patent: US 6,943,512 B2
• Time in Patent Office: Days
• US Class Current: 318/432
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0493 detecting processor errors, e.g. plausibility of steering direction
• CPC Class Codes: B62D 6/08 responsive only to driver input torque

Abstract

The present invention is a control apparatus for controlling an electric power steering system having steering assist force control means for controlling a motor that gives a steering assist force to a steering mechanism relying upon a main torque input value obtained by subjecting a main torque signal from a torque sensor to the A/D conversion, upon a gain-multiplied torque input value obtained by multiplying said main torque signal by a first gain times followed by the A/D conversion and upon a sub-torque signal from said torque sensor, in order to carry out a failsafe function, characterized by the provision of a gain multiplier for multiplying said main torque input value by a second gain times,. and switching means for changing the output of said gain multiplier and said gain-multiplied torque input value over to each other to input it to said steering assist force control means.

Claims

1. A control apparatus for an electric power steering system having a steering assist force control means for controlling a motor that gives a steering assist force to a steering mechanism relying upon a main torque input value obtained by subjecting a main torque signal from a torque sensor to an A/D conversion, upon a gain-multiplied torque input value obtained by multiplying said main torque signal by a first gain times followed by the A/D conversion and upon a sub-torque value from said torque sensor, in order to carry out a failsafe function,

characterized by the provision of a gain multiplier for multiplying said main torque input value by a second gain times, and a switching means for changing the output of said gain multiplier and said gain-multiplied torque input value over to each other to input it to said steering assist force control means.

2. A control apparatus for an electric power steering system according to claim 1, wherein when said main torque signal exceeds an input range of a control unit, said main torque input value is multiplied by said gain multiplier to be the same as by said first gain times through said switching means and is inputted to said steering assist force control means.

3. A control apparatus for an electric power steering system according to claim 1, wherein said gain multiplier and said switching means are realized by software functions.

4. A control apparatus for an electric power steering system according to claim 2, wherein said gain multiplier and said switching means are realized by software functions.

5. A control apparatus for an electric power steering system according to claim 1, wherein said gain multiplier is a digital type.

6. A control apparatus for an electric power steering system according to claim 1, wherein said main torque input value is formed in a A/D converter and said gain-multiplied torque input value is formed in a second A/D converter.

7. A control apparatus for an electric power steering system according to claim 6, wherein an output of said gain multiplier does not exceed a rate input region of said second A/D converter.

8. A control apparatus for an electric power steering system,

wherein a main torque input value obtained by A/D converting a main torque signal from a torque sensor is inputted to a center response improving unit, said main torque signal is gain-multiplied and then is A/D converted, the outputted gain-multiplied torque input value is inputted to a steering assist force command operation unit and said center response improving unit, a sub-torque signal from said torque sensor is A/D converted and then is utilized to a failsafe function, and a steering assist force is given to a steering mechanism based upon each output of said steering assist force command operation unit and said center response improving unit,

characterized by the provision of a gain multiplier for multiplying said main torque input value by a second gain times, and a switching means for changing the output of said gain multiplier and said gain-multiplied torque input value over to each other to input it to said center response improving unit.

9. A control apparatus for an electric power steering system according to claim 8, wherein when said main torque signal exceeds an input range of a control unit, said main torque input value is multiplied by said gain multiplier to be the same as by said first gain times through said switching means and is inputted to said center response improving unit.