Bounded synchronous angle counter

• US 5,041,979 A
• Filed: 06/21/1989
• Issued: 08/20/1991
• Est. Priority Date: 04/08/1987
• Status: Expired due to Term

• Current Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kopec, James W., Zerrien, Donald W., Hirka, Gerald M.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Trans, V.
• Application Number:
  US07/370,158
• Time in Patent Office: 790 Days
• Field of Search: 364/559, 364/569, 364/431.04, 364/571.01, 123/414, 123/416, 123/417, 73/116, 718/600, 718/603, 340/870.19, 340/870.23, 340/870.24
• US Class Current: 701/102
• CPC Class Codes: F02P 7/0775 Electronical verniers
• CPC Class Codes: G01D 3/028 mitigating undesired influences, e.g. temperature, pressure
• CPC Class Codes: G01D 5/24404 Interpolation using high frequency signals
• CPC Class Codes: G01D 5/2457 Incremental encoders having reference marks
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors
• CPC Class Codes: H03M 1/308 with additional pattern means for determining the absolute position, e.g. reference marks

Abstract

An angle measuring device is described for accurately indicating the position of the rotor relative to the reference position in view of perceived changes of rotor speed. The measuring device includes a sensor for detecting the markings and generating a sensor signal in response thereto; an angle counter, responsive to the sensor, for generating a position signal; and a correction circuit, responsive to the sensor signal, for correcting the position signal. The position signal is corrected in response to the sensor signal so as to provide an accurate indication of the position of the rotor.

Claims

1. In a system for measuring angle of a rotating rotor having rotor markings including a reference marking at a reference position on the rotor and a plurality of other markings spaced about the rotor, an angle measuring device for accurately indicating angular position of the rotor relative to the reference position in view of perceived changes of rotor speed, comprising:

means for detecting each of at least said other rotor markings and generating a signal pulse in response thereto;

interpolation means, responsive to said signal pulses, for indicating relative angular position of said rotor by providing a plurality of interpolated angular position signal pulses, having a rate of occurrence, between each of said sensor signal pulses;

counting means responsive to said sensor signal pulses and said interpolated angular position signal pulses, for generating a position signal which includes a binary number corresponding to a unique position of the rotor relative to the reference position; and

correction means, responsive to time occurrences of said sensor signal pulses, for correcting said position signal by modifying the rate of occurrence of said interpolated angular position signal pulses;

whereby the position signal is corrected in response to the sensor signal pulses so as to provide accurate indication of the position of the rotor.

2. An angle measuring device for measuring the angle of a rotating rotor, according to claim 1, wherein said correction means includes means for detecting perceived accelerations and for forcing said position signal to spurt ahead, and includes means for detecting perceived decelerations and for forcing said position signal to stall.

3. An angle measuring device for measuring the angle of a rotating rotor, according to claim 1, further including reinitialization means for detecting the reference marking and for reinitializing said position signal in response to the reference marking being detected.

4. An angle measuring device for measuring the angle of a rotating rotor, according to claim 1, wherein said correction means includes timing means for measuring the time between said sensor signal pulses and comparison means for comparing at least one of said measured times against at least one predetermined value.

5. An angle measuring device for measuring the angle of a rotating rotor, according to claim 4, wherein said at least one predetermined value includes a value representative of a time period after which a sensor signal is expected.

6. An angle measuring device for measuring the angle of a rotating rotor, according to claim 4, wherein said at least one predetermined value includes a value representative of a previously measured time between sensor signals.

7. An angle measuring device for measuring the angle of a rotating rotor, according to claim 1, wherein said position signal is a binary number which is capable of reaching a number substantially greater than the number of markings on the rotor during one revolution thereof.

8. An angle measuring device for measuring the angle of a rotating rotor, according to claim 7, wherein said binary number comprises an integer part and a fractional part.

9. An angle measuring device for measuring the angle of a rotating rotor, according to claim 8, wherein said correction means includes means for stalling the fractional part of the binary number until another sensor signal is generated by the sensor means.

10. An angle measuring device for measuring the angle of a rotating rotor, according to claim 8, wherein said correction means includes means for spurting the fractional part of the binary number until the integer part of the binary number is incremented.

11. An angle measuring device for measuring the angle of a rotating rotor, according to claim 1, wherein said counting means includes;

timing means for measuring the time between said sensor signal pulses, and

interpolation means, responsive to said time measured between said sensor signal pulses, for generating a signal to said correction means indicative of relative angular position of the rotor between sensor signal pulses.

12. In a system for measuring angle of a rotating rotor having rotor markings including a plurality of markings spaced about the rotor and a missing marking reference position, an angle measuring device for accurately indicating angular position of the rotor relative to the reference position, comprising:

sensor means for detecting each of the rotor markings and generating a sensor signal pulse in response thereto;

interpolation means, responsive to said signal pulses, for indicating relative angular position of said rotor between sensor signal pulses by providing a plurality of interpolated angular position signal pulses, having a rate of occurrence, between each of said sensor signal pulses; and

counting means responsive to said sensor signal pulses and said interpolated angular position signal pulses, for generating a position signal which includes a binary number corresponding to a unique position of the rotor relative to the reference position; and

correction means, responsive to time occurrences of said sensor signal pulses, for correcting said position signal such that the position signal is compensated for perceived changes of rotor speed by modifying the occurrence rate of said interpolated angular position signal pulses, whereby the corrected position signal is accurately representative of the angular position of the rotor relative to the reference position.

13. An angle measuring device for measuring the angle of a rotating rotor, according to claim 12, wherein said correction means corrects said position signal based on time period between previous sensor signal pulses.

14. An angle measuring device for measuring the angle of a rotating rotor, according to claim 12, further including means, responsive to said sensor signal pulses, for detecting the missing marking reference position and resetting the position signal in response thereto.

15. An angle measuring device for measuring the angle of a rotating rotor, according to claim 12, wherein said counting means includes means for correcting said position signal at the missing marking reference position.