Fault detection in an electric power-assisted steering system
First Claim
1. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
- determining a voltage vector of an electric power-assisted steering motor;
measuring a current vector of the electric power-assisted steering motor;
defining an acceptable angular relationship between the voltage vector and the current vector;
comparing an angle between the measured current vector and the determined voltage vector;
indicating a fault if the angle does not meet the acceptable angular relationship; and
detecting a rotational direction of the electric power-assisted steering motor,wherein the defining step includes a first acceptable angular relationship for a positive motor rotational direction where the angle of the voltage vector must lead the angle of the current vector, a second acceptable angular relationship for a negative motor rotational direction where the angle of the voltage vector must lag the angle of the current vector, and a third acceptable angular relationship for a substantially zero motor rotational direction where the angles of the voltage and current vectors are substantially in-phase.
3 Assignments
0 Petitions
Accused Products
Abstract
A method and system for detecting faults in an electric power-assisted steering system includes determining a voltage vector of an electric power-assisted steering motor and measuring a current vector of the motor. Acceptable angular relationships are defined between the voltage vector and the current vector, which are then compared to find a fault if the angle does not meet the acceptable angular relationship. Additionally, motor direction and position can also be used against an angular check of the voltage and/or current vector. Similarly, torque direction can be used. In this way, several different faults can be determined dynamically under transient conditions.
-
Citations
17 Claims
-
1. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
-
determining a voltage vector of an electric power-assisted steering motor; measuring a current vector of the electric power-assisted steering motor; defining an acceptable angular relationship between the voltage vector and the current vector; comparing an angle between the measured current vector and the determined voltage vector; indicating a fault if the angle does not meet the acceptable angular relationship; and detecting a rotational direction of the electric power-assisted steering motor, wherein the defining step includes a first acceptable angular relationship for a positive motor rotational direction where the angle of the voltage vector must lead the angle of the current vector, a second acceptable angular relationship for a negative motor rotational direction where the angle of the voltage vector must lag the angle of the current vector, and a third acceptable angular relationship for a substantially zero motor rotational direction where the angles of the voltage and current vectors are substantially in-phase. - View Dependent Claims (2, 3)
-
-
4. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
-
determining a voltage vector of an electric power-assisted steering motor, wherein the determining step includes the substeps of measuring a voltage pulse width output from the electric power-assisted steering motor and checking the measured pulse width against a commanded pulse width; measuring a current vector of the electric power-assisted steering motor; defining an acceptable angular relationship between the voltage vector and the current vector; comparing an angle between the measured current vector and the determined voltage vector; and indicating a fault if at least one of the following occurs;
the angle does not meet the acceptable angular relationship, or if a difference in the measured and commanded pulse widths exceeds a predetermined error limit. - View Dependent Claims (5)
-
-
6. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
-
determining a voltage vector of an electric power-assisted steering motor; measuring a current vector of the electric power-assisted steering motor; defining an acceptable angular relationship between the voltage vector and the current vector; comparing an angle between the measured current vector and the determined voltage vector; indicating a fault if the angle does not meet the acceptable angular relationship; and detecting a position of the electric power-assisted steering motor, wherein the defining step includes defining an acceptable angular relationship between the motor position and the current vector, and wherein the comparing step includes comparing an angle between the measured current vector and the detected motor position, and further comprising indicating a fault if the angle between the measured current vector and the motor position does not meet the acceptable angular relationship for the measured current vector and the motor position. - View Dependent Claims (7)
-
-
8. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
-
determining a voltage vector of an electric power-assisted steering motor; measuring a current vector of the electric power-assisted steering motor, wherein the measuring step includes the substeps of measuring a torque drive current to the motor and checking the torque drive current against a commanded torque drive current; defining an acceptable angular relationship between the voltage vector and the current vector; comparing an angle between the measured current vector and the determined voltage vector; and indicating a fault if at least one of the following occurs;
the angle does not meet the acceptable angular relationship, orif a difference in the measured and commanded torque drive currents exceeds a predetermined error limit.
-
-
9. A fault detection system for an electric power-assisted steering motor, the fault detection system comprising:
-
a voltage vector detector coupled to the motor that determines a voltage vector of the motor; a current vector detector coupled to the motor that measures a current vector of the motor; a processor coupled to the detectors, the processor defines an acceptable angular relationship between the voltage vector and the current vector, and inputs the voltage and current vectors from the associated detectors to compare an angle therebetween, wherein the processor indicates a fault if the angle does not meet the acceptable angular relationship; and a motor rotational direction detector coupled between the motor and the processor, wherein the processor further defines a first acceptable angular relationship for a positive motor rotational direction where the angle of the voltage vector must lead the angle of the current vector, a second acceptable angular relationship for a negative motor rotational direction where the angle of the voltage vector must lag the angle of the current vector, and a third acceptable angular relationship for a substantially zero motor rotational direction where the angles of the voltage and current vectors are substantially in-phase. - View Dependent Claims (10)
-
-
11. A fault detection system for an electric power-assisted steering motor, the fault detection system comprising:
-
a voltage vector detector coupled to the motor that determines a voltage vector of the motor, wherein the voltage vector detector operates to measures a voltage pulse width output from the motor to determine the output voltage vector; a current vector detector coupled to the motor that measures a current vector of the motor; and a processor coupled to the detectors, the processor defines an acceptable angular relationship between the voltage vector and the current vector, inputs the voltage and current vectors from the associated detectors to compare an angle therebetween, and indicates a fault if the angle does not meet the acceptable angular relationship, and wherein the processor further operates to check the measured pulse width against a commanded pulse width from the processor, and if a difference in the measured and commanded pulse widths exceeds a predetermined error limit, the processor indicates a fault.
-
-
12. A fault detection system for an electric power-assisted steering motor, the fault detection system comprising:
-
a voltage vector detector coupled to the motor that determines a voltage vector of the motor; a current vector detector coupled to the motor that measures a current vector of the motor; a processor coupled to the detectors, the processor defines an acceptable angular relationship between the voltage vector and the current vector, and inputs the voltage and current vectors from the associated detectors to compare an angle therebetween, wherein the processor indicates a fault if the angle does not meet the acceptable angular relationship; and a motor position detector coupled between the motor and the processor, wherein the processor further defines an acceptable angular relationship between the motor position and the current vector, inputs the motor position and the current vector and compares an angle therebetween, and indicates a fault if the angle between the measured current vector and the motor position does not meet the acceptable angular relationship for the measured current vector and the motor position. - View Dependent Claims (13)
-
-
14. A fault detection system for an electric power-assisted steering motor, the fault detection system comprising:
-
a voltage vector detector coupled to the motor that determines a voltage vector of the motor; a current vector detector coupled to the motor that measures a current vector of the motor, wherein the current sensor includes torque detection; and a processor coupled to the detectors, the processor defines an acceptable angular relationship between the voltage vector and the current vector, inputs the voltage and current vectors from the associated detectors to compare an angle therebetween, indicates a fault if the angle does not meet the acceptable angular relationship, and wherein the processor further inputs a detected torque from the torque detection and checks the torque drive current against a commanded torque drive current, and wherein if a difference in the measured and commanded torque drive currents exceeds a predetermined error limit, the processor indicates a fault.
-
-
15. A method for detecting a fault in an electric power-assisted steering system, the method comprising the steps of:
-
measuring a pulse width of an output voltage to an electric power-assisted steering motor; comparing the measured pulse width against a commanded pulse width; and indicating a fault if a difference in the measured and commanded pulse widths exceeds a predetermined error limit. - View Dependent Claims (16, 17)
-
Specification