Electric power steering apparatus

• US 6,226,580 B1
• Filed: 10/29/1999
• Issued: 05/01/2001
• Est. Priority Date: 12/28/1998
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Hironaka, Shinzi, Mukai, Yoshinobu, Noro, Yoshiki, Kawashima, Mitsunori
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US09/429,276
• Time in Patent Office: 550 Days
• Field of Search: 180/443, 180/446, 701/41, 701/42, 701/43, 318/52, 318/587
• US Class Current: 701/42
• CPC Class Codes: B62D 5/0493 detecting processor errors, e.g. plausibility of steering direction

Abstract

Control unit in an electric power steering apparatus includes a motor drive inhibition section for inhibiting output of a motor control signal on the basis of at least a steering torque signal supplied from a steering torque sensor. The control unit also includes a zero-value setting section for, when drive inhibition signals are output by the motor drive inhibition section, setting a target motor current signal to a zero value irrespective of a value of the steering torque signal, and an inhibition cancellation section for cancelling the drive inhibition signals when an offset between the target motor current signal and the detected motor current signal becomes zero after the target motor current signal is set to the zero value by the zero-value setting section. With this arrangement, instructions can be communicated bidirectionally from the motor drive inhibition section to a main power steering control where an anomaly has occurred and from the main power steering control to the inhibition cancellation section, so that the inhibition of the motor drive can be canceled promptly.

Claims

1. An electric power steering apparatus for a vehicle comprising:

an electric motor for imparting an electric steering assist to a steering system of the vehicle;

a steering torque sensor for detecting steering torque manually applied to the vehicle steering system to output a steering torque signal;

a motor current detector for detecting a motor current actually flowing through said electric motor to output a detected motor current signal;

a control unit including a target motor current setting section for setting a target motor current signal on the basis of at least the steering torque signal output by said steering torque sensor, an offset calculator section for calculating an offset between the target motor current signal set by said target motor current setting section and the detected motor current signal output by said motor current detector to thereby output an offset signal indicative of the offset calculated thereby, a drive control section for generating a motor control signal on the basis of the offset signal output by said offset calculator section, and a motor drive inhibition section for, on the basis of at least the steering torque signal output by said steering torque sensor, outputting drive inhibition signals to inhibit output of the motor control signal by said drive control section; and

a motor driver circuit for driving said electric motor in accordance with the motor control signal output by said drive control section,

wherein said control unit further includes;

a zero-value setting section for, when the drive inhibition signals are output by said motor drive inhibition section, setting the target motor current signal to a zero value irrespective of a value of the steering torque signal; and

an inhibition cancellation section for cancelling the drive inhibition signals when the offset signal output by said offset calculator section becomes zero after the target motor current signal is set to the zero value by said zero-value setting section.

2. An electric power steering apparatus as recited in claim 1 wherein said zero-value setting section includes:

a zero-value generator section for, on the basis of the drive inhibition signals output by said motor drive inhibition section, detecting a motor drive inhibition condition where driving of said electric motor is to be inhibited and outputting a prestored coefficient signal of value 0 upon detection of the motor drive inhibition condition; and

a multiplier for, when the motor drive inhibition condition is detected by said zero-value generator section, multiplies the target motor current signal by the coefficient of value 0 to thereby compulsorily set the target motor current signal to the zero value.

3. An electric power steering apparatus as recited in claim 2 wherein said zero-value generator section includes:

a first storage section prestoring a value 1 as a coefficient;

a second storage section prestoring a value 0 as a coefficient;

a logic operator section for performing an exclusive OR operation on the drive inhibition signals output by said motor drive inhibition section, to detect whether or not said motor drive inhibition section is signaling the motor drive inhibition condition; and

a selector section for selecting between the coefficient of the value 1 stored in said first storage section and the coefficient of the value 0 stored in said second storage section, to supply the coefficient of the value 1 or the coefficient of the value 0 to said multiplier for multiplication with the target motor current signal.

4. An electric power steering apparatus as recited in claim 1 wherein said inhibition cancellation section includes:

a first inverter for inverting the coefficient signal of value 0 output by said zero-value setting section;

a second inverter for inverting the offset signal of value 0 output by said offset calculator section; and

an AND circuit for performing an AND operation on the coefficient signal inverted by said first inverter and the offset signal inverted by said second inverter,

wherein an output from said AND circuit is supplied to said motor drive inhibition section as an inhibition cancellation signal, so as to cancel inhibition of the driving of said electric motor.

5. An electric power steering apparatus as recited in claim 1 wherein said motor drive inhibition section includes:

a drive-inhibition-condition determination section for making a comparison between the steering torque signal output by said steering torque sensor and prestored reference torque values and outputs the drive inhibition signals when a result of the comparison indicates that the driving of said electric motor is to be inhibited; and

an output inhibition section for, when said drive-inhibition-condition determination section determines that the driving of said electric motor is to be inhibited, inhibiting output of the motor control signal from said motor drive section in accordance with the drive inhibition signals.

6. An electric power steering apparatus as recited in claim 1 wherein said motor drive inhibition section inhibits output of the motor control signal on the basis of at least the steering torque signal and the detected motor current signal.