Shaft feedback sensor error detection

• US 7,263,453 B1
• Filed: 01/19/2005
• Issued: 08/28/2007
• Est. Priority Date: 01/21/2004
• Status: Active Grant

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Deka Products Limited Partnership
• Inventors: Robinson, David W., Sachs, Jason M., Kaufman, Michael Field, Gansler, Michael Thomas, Manthiri, Soundararajan
• Primary Examiner(s): Barlow; John
• Assistant Examiner(s): TEIXEIRA MOFFAT, JONATHAN CHARLES
• Application Number:
  US11/038,777
• Time in Patent Office: 951 Days
• Field of Search: 702/104, 702/150, 702/151, 702/152, 702/153, 702/154, 702/95
• US Class Current: 702/104
• CPC Class Codes: G01D 5/24457 Failure detection

Abstract

Methods and apparatus for detecting a sensor angle error in a system in which a measured quantity is determined on the basis of a phase of a signal. A signal derived from the measurement of multiple sensors is ascribed to a vector in a two-dimensional space, and a norm is calculated characterizing that vector. A value is calculated characterizing variation of that norm over a specified period of time and that value is compared with a threshold in order to identify a sensor fault.

Claims

1. A method for detecting a sensor angle error in a system employing a rectangular-to-polar coordinate conversion, the method comprising:

a. ascribing multiple sensor measurements to a vector in a two-dimensional space;

b. calculating a norm characterizing the vector;

c. determining a single scalar value characterizing variation of the norm over a specified period of time, the single scalar value amenable to scalar comparison; and

d. comparing the single scalar value characterizing variation of the norm to a specified threshold value; and

e. enabling fault-handling procedures in case of variation of the norm exceeding the specified threshold.

2. A method in accordance with claim 1, wherein the step of determining a single scalar value characterizing variations of the norm includes:

i. determining a first value characterizing a time-averaged minimum of the norm;

ii. determining a second value characterizing a time-averaged maximum of the norm; and

iii. calculating the single scalar value characterizing variation of the norm as a function of the maximum and minimum of the norm.

3. A method in accordance with claim 2, wherein the function of the maximum and the minimum of the norm is a ratio of the maximum to the minimum.

4. In a sensor system of the type employing a rectangular-to-polar coordinate conversion, an improvement comprising;

a. a plurality of sensors for generating analog sensor signals together defining a vector in a two-dimensional space;

b circuitry for combining the analog sensor signals to create a plurality of demodulated signals of known phase relationship;

c. a norm processor for combining the plurality of demodulated signals to derive a single scalar norm characterizing the vector; and

d. a comparator for comparing a function of the single, scalar norm to a specified threshold, wherein the function characterizes behavior of the norm over a specified period of time.

5. The improvement of claim 4, wherein the function is a ratio of a maximum to a minimum of the norm over the course of a cycle.