Electric power steering apparatus
First Claim
1. An electric power steering apparatus including an electric motor for providing an assist torque to a steering system, a steering torque detecting unit for detecting a steering torque exerted on said steering system to generate a steering torque signal, a target current determining unit for determining, on the basis of at least said steering torque signal, a target current to be supplied to said electric motor so as to generate a target current signal, a current detecting unit for detecting a current flowing through said electric motor to generate a motor current signal, an offset calculating unit for calculating an offset between said target current signal and said motor current signal to generate an offset signal, a motor operation control unit for generating, on the basis of said offset signal, a drive control signal to drive said electric motor, and a motor drive unit for driving said electric motor on the basis of said drive control signal, said electric power steering apparatus comprising:
- a judgment unit which passes a judgment that a condition in which one of said offset signal and said drive control signal exceeds a preset threshold has continued for a preset allowable time;
a forced drive control unit for generating a forced drive control signal tending to forcibly drive said electric motor when said judgment is passed by said judgment unit; and
a fault judgment unit which judges said current detecting unit to be at fault if said motor current signal does not vary even though said electric motor is forcibly driven.
1 Assignment
0 Petitions
Accused Products
Abstract
An electric power steering apparatus includes a judgment unit which passes a judgment that a condition, in which an offset signal indicative of the offset between a target current signal and a motor current signal, or a drive control signal used for controlling an electric motor is greater than a threshold, has continued for an allowable time. Based on this judgment, a forced drive control unit forcibly drives the electric motor. A fault judgment unit monitors the motor current in all times and judges a current detecting unit to be at fault if the motor current does not vary even though the electric motor is drive forcibly. Thus, even when a failure in the current detecting unit occurs during movement of a motor vehicle, such failure can reliably be detected. Additionally, since the judgment is performed after the electric motor is driven forcibly, misjudgment does not occur even when the judgement at the judgment unit results from continuous application of abrupt manual steering operation.
62 Citations
16 Claims
-
1. An electric power steering apparatus including an electric motor for providing an assist torque to a steering system, a steering torque detecting unit for detecting a steering torque exerted on said steering system to generate a steering torque signal, a target current determining unit for determining, on the basis of at least said steering torque signal, a target current to be supplied to said electric motor so as to generate a target current signal, a current detecting unit for detecting a current flowing through said electric motor to generate a motor current signal, an offset calculating unit for calculating an offset between said target current signal and said motor current signal to generate an offset signal, a motor operation control unit for generating, on the basis of said offset signal, a drive control signal to drive said electric motor, and a motor drive unit for driving said electric motor on the basis of said drive control signal, said electric power steering apparatus comprising:
-
a judgment unit which passes a judgment that a condition in which one of said offset signal and said drive control signal exceeds a preset threshold has continued for a preset allowable time; a forced drive control unit for generating a forced drive control signal tending to forcibly drive said electric motor when said judgment is passed by said judgment unit; and a fault judgment unit which judges said current detecting unit to be at fault if said motor current signal does not vary even though said electric motor is forcibly driven. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. An electric power steering apparatus including an electric motor for providing an assist torque to a steering system, a steering torque detecting unit for detecting a steering torque exerted on said steering system to generate a steering torque signal, a target current determining unit for determining, on the basis of at least said steering torque signal, a target current to be supplied to said electric motor so as to generate a target current signal, a current detecting unit for detecting a current flowing through said electric motor to generate a motor current signal, an offset calculating unit for calculating an offset between said target current signal and said motor current signal to generate an offset signal, a motor operation control unit for generating, on the basis of said offset signal, a drive control signal to drive said electric motor, and a motor drive unit for driving said electric motor on the basis of said drive control signal, said electric power steering apparatus comprising:
-
a judgment unit which passes a judgment that a variation of said motor current signal per unit time is smaller than a predetermined value when one of said offset signal and said drive control signal is greater than a preset threshold; a forced drive control unit for generating a forced drive control signal tending to forcibly drive said electric motor when said judgment unit has passed said judgment; and a fault judgment unit which judges said current detecting unit to be at fault if said motor current signal does not vary even though said electric motor is forcibly driven. - View Dependent Claims (10, 11, 12, 13)
-
-
14. An electric power steering apparatus including an electric motor for providing an assist torque to a steering system, a steering torque detecting unit for detecting a steering torque exerted on said steering system to generate a steering torque signal, a target current determining unit for determining, on the basis of at least said steering torque signal, a target current to be supplied to said electric motor so as to generate a target current signal, a current detecting unit for detecting a current flowing through said electric motor to generate a motor current signal, an offset calculating unit for calculating an offset between said target current signal and said motor current signal to generate an offset signal, a motor operation control unit for generating, on the basis of said offset signal, a drive control signal to drive said electric motor, and a motor drive unit for driving said electric motor on the basis of said drive control signal, said electric power steering apparatus comprising:
-
a first judgment unit which passes a judgment that a condition in which one of said offset signal and said drive control signal exceeds a first threshold has continued for a preset allowable time; a second judgment unit which passes a judgment that a variation of said motor current signal per unit time is smaller than a predetermined value when said drive control signal is greater than a second threshold; a forced drive control unit for generating a forced drive control signal tending to forcibly drive said electric motor when said judgment of said first judgment unit and said judgment of said second judgment unit have passed concurrently; and a fault judgment unit which judges said current detecting unit to be at fault if said motor current signal does not vary even though said electric motor is forcibly driven. - View Dependent Claims (15, 16)
-
Specification