Fault tolerant field oriented control for electric power steering

Patent metadata

Field	Value
Publication number	US-10960922-B2
Application number	US-201715420260-A
Country	US
Kind code	B2
Filing date	Jan 31, 2017
Priority date	Jan 31, 2017
Publication date	Mar 30, 2021
Grant date	Mar 30, 2021

Abstract

A control system for monitoring operation of an electric motor includes a plurality of position sensors configured to measure a position of the electric motor, an indirect position estimation module configured to indirectly estimate the position of the motor, and an error monitoring module. The error monitoring module is configured to perform at least one of: comparing a measured position from the plurality of position sensors to an estimated position from the sensor position estimation module, and detecting a failure of at least one of the one or more position sensors based on the comparison; and calculating a difference between the measured position from one of the plurality of position sensors and the measured position from another of the plurality of position sensors, and causing the indirect position estimation module to initiate estimation of the position of the motor based on the difference.

First claim

Having thus described the invention, it is claimed:

1. A control system for monitoring operation of an electric motor, the control system comprising:
a plurality of position sensors each configured to output a measured position of the electric motor;
the control system operable to
operate the electric motor based on the measured position of the electric motor,
determine an estimated position of the electric motor using a model-based observer; and
responsive to a difference, between a first measured position output from a first one of the plurality of position sensors and a second measured position output from a second one of the plurality of position sensors, exceeding a predetermined threshold, operate the electric motor based on the estimated position of the electric motor; and

the control system configured to perform at least one of:
generating a triggering flag based on the difference exceeding a first threshold, the triggering flag causing initialization of an indirect estimation of the motor position, comprising prediction of an initial position at a time prior to the difference exceeding the first threshold; and
generating a transition flag based on the difference exceeding a second threshold that is greater than the first threshold, the transition flag causing the control system to transition from a first control mode to a second control mode, the first control mode causing the control system to control the motor based on one of the first measured position and the second measured position, the second control mode causing the control system to control the motor based on the indirect estimation of the motor position.

2. The control system of claim 1 , wherein the control system is operable to generate a comparison health status flag that indicates whether at least one of the plurality of position sensors has failed or will potentially fail.

3. The control system of claim 1 , wherein the control system is further configured to operate the electric motor based on the estimated position of the electric motor when an estimated difference between one of the first measured position and the second measured position and the estimated position exceeding a selected threshold.

4. The control system of claim 1 , wherein the estimated position of the electric motor is based on a stator flux linkage, the stator flux linkage calculated based on voltage and current signals from the electric motor.

5. The control system of claim 1 , wherein the control system is configured to estimate a time duration between the difference exceeding the first threshold and the initialization.

6. The control system of claim 5 , wherein the control system is configured to identify which of the first one of the plurality of position sensors and the second one of the plurality of position sensors is faulty based on the time duration.

7. A method of monitoring operation of an electric motor, comprising:
receiving a first measured position of the electric motor from a first position sensor and receiving a second measured position of the electric motor from a second position sensor;
generating a position estimate of the motor based on a stator flux linkage, and using a model-based observer;
comparing the first measured position to the second measured position;
detecting a failure of at least one of the first position sensor and the second position sensor based on the comparison of the first measured position and the second measured position;
responsive to the failure, operating the electric motor based on the position estimate;
wherein the position estimate is based on an initial position prediction based on at least one of the first measured position and the second measured position.

8. The method of claim 7 , further comprising generating a comparison health status flag that indicates whether at least one of the first position sensor and the second position sensor has failed or will potentially fail.

9. The method of claim 7 , further comprising detecting the failure is based on a difference between at least one of the first measured position and the second measured position and the position estimate exceeding a selected threshold.

10. The method of claim 7 , wherein the initial position prediction is based on the first measured position when a comparison between the second measured position and the position estimate exceeds a selected threshold.

11. A method of monitoring operation of an electric motor, the method comprising:
measuring a position of the electric motor by each of a plurality of position sensors during a field oriented control (FOC) operation mode;
calculating, by an error monitoring module, a difference between a first measured position output from a first one of the plurality of position sensors and a second measured position output from a second one of the plurality of position sensors, the calculating the difference comprising:
comparing the first measured position from the first one of the plurality of position sensors to the second measured position from the second one of the plurality of position sensors; and

based on the difference exceeding a predetermined threshold, causing an indirect position estimation module to initiate an indirect estimation of the position of the motor using a model-based observer;
operating the electric motor with a control system; and
at least one of:
generating a triggering flag based on the difference exceeding a first threshold, the triggering flag causing initialization of the indirect estimation of the position of the motor, comprising prediction of an initial position at a time prior to the difference exceeding the first threshold; and
generating a transition flag based on the difference exceeding a second threshold that is greater than the first threshold, the transition flag causing the control system to transition from a first control mode to a second control mode, the first control mode causing the control system to control the motor based on one of the first measured position and the second measured position, the second control mode causing the control system to control the motor based on the indirect estimation of the position of the motor.

12. The method of claim 11 , further comprising generating an error condition flag based on the difference between the first measured position and the second measured position.

13. The method of claim 11 , further comprising estimating a time duration between the difference exceeding the first threshold and the initialization.

14. The method of claim 13 , further comprising identifying which of the first one of the plurality of position sensors and the second one of the plurality of position sensors is faulty based on the time duration.

Assignees

• Steering Solutions Ip Holding

Inventors

• Pramod Prerit
• Mitra Rakesh
• Zuraski Jeffery A
• Chandy Ashok
• Kleinau Julie A

Classifications

• H02P6/181

  using different methods depending on the speed · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P21/13

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• B62D5/049 Primary

  detecting sensor failures · CPC title