Electric power steering system

• US 20070137924A1
• Filed: 12/15/2006
• Published: 06/21/2007
• Est. Priority Date: 12/15/2005
• Status: Abandoned Application

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Kawada, Hideaki
• Application Number:
  US11/639,253
• Publication Number:
  US 20070137924A1
• Time in Patent Office: Days
• US Class Current: 180/446
• CPC Class Codes: B62D 5/046 Controlling the motor

Abstract

An electric power steering system is provided which includes a current command value calculation unit 10 for calculating a current command value based on a steering torque signal and a vehicle speed signal and a motor driving unit 52 for controlling a motor 8 for imparting a steering assist force to a steering mechanism based on the current command value. The electric power steering system has further a voltage detection unit 17 for detecting a voltage of a power supply source 11 for supplying power to the motor driving unit 52 and a phase compensating unit 58 provided on the current command value calculation unit 10 and adapted to select characteristics based on a voltage of the power supply source.

Claims

1. An electric power steering system comprising:

a current command value calculation unit for calculating a current command value based on a steering torque signal and a vehicle speed signal;

a motor driving unit for controlling a motor for imparting a steering assist force to a steering mechanism based on the current command value;

a voltage detection unit for detecting a voltage of a power supply source for supplying power to the motor driving unit; and

a phase compensating unit provided on the current command value calculation unit and adapted to select characteristics based on a voltage of the power supply source.

2. An electric power steering system as set forth in claim 1, wherein the phase compensating unit is adapted to select the characteristics so as to suppress a turning follow-up capability when the voltage detection unit detects that the voltage of the power supply source is lower than a set voltage.

3. An electric power steering system as set forth in claim 1, wherein the phase compensating unit is adapted to select a characteristic to secure the turning follow-up capability when the value of a vehicle speed signal is a set value or larger, whereas with the value of the vehicle speed signal being smaller than the set value, the phase compensating unit is adapted to select a characteristic to suppress the turning follow-up capability when the voltage of the power supply source is lower than the set voltage.