System and method for generating a high speed estimated position output for a position encoder

• US 7,094,978 B2
• Filed: 11/15/2002
• Issued: 08/22/2006
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Skurnik, David
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): DHARIA, PRABODH M
• Application Number:
  US10/298,339
• Publication Number:
  US 20040094338A1
• Time in Patent Office: 1,376 Days
• Field of Search: 345/157, 345/163, 345/156, 345173-183, 345/700, 345/706, 345/473, 178/18.01, 178/18, 178/19, 715/700, 250/231.13, 114/312, 713/323, 600/450, 324/207.17, 340/679
• US Class Current: 178/18.01
• CPC Class Codes: G01D 5/24495 using previous values
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means

Abstract

A system and method for generating an approximated position signal that is updated and output at a rate higher than a base rate of actual position signals measured using a position transducer. The actual position signals are determined and/or stored by a transducer signal processing circuit at discrete time intervals. The approximated position signals are generated by a high frequency estimated position generating circuit. A rate of incrementing the approximated position signals is adjusted for use during the next discrete time interval by an error correction feedback loop, based on a difference between certain approximated and actual position values. The accuracy of the system may be further improved by utilizing a latch signal to ensure that the approximated and actual position values that are compared by the error feedback loop correspond to the same time.

Claims

1. A position monitoring system, comprising:

a position transducer;

a transducer signal processing circuit operably connectable to the position transducer; and

an interface circuit that includes an estimated position signal generating circuit operably connectable to the transducer signal processing circuit;

wherein;

the transducer signal processing circuit generates a transducer sample position output value corresponding to the actual position of the position transducer, according to a transducer sample position value output interval that is not less than a minimum transducer sample position output interval;

the estimated position signal generating circuit generates an approximated position output approximating the position of the position transducer, at a plurality of times between the generating of a transducer sample position output value corresponding to the actual position of the position transducer, according to an approximated position output cycle interval which is shorter than the minimum transducer sample position output interval;

the approximated position output is incremented by a prescribed increment amount during each approximated position output cycle;

the prescribed increment amount is adjusted when a new transducer sample position output value corresponding to the actual position of the position transducer becomes available; and

the adjustment of the prescribed increment amount is based at least partially on a determined difference between a particular approximated position output and the new transducer sample position value.

2. The position monitoring system of claim 1, wherein at least one of the position transducer and the transducer signal processing circuit and the estimated position signal generating circuit is operably connectable to at least one other of the position transducer and the transducer signal processing circuit and the estimated position signal generating circuit, through one of a wireless communication interface circuit and a wired connection.

3. The position monitoring system of claim 1, wherein the determined difference is based on a particular approximated position output that is selected by one of the transducer signal processing circuit and the estimated position signal generating circuit, based on timing information corresponding to the timing of the new transducer sample position.

4. The position monitoring system of claim 3, wherein the timing information corresponding to the timing of the new transducer sample position is a value-latching signal output by the transducer signal processing circuit and input by the estimated position signal generating circuit.

5. The position monitoring system of claim 3, wherein the timing information corresponding to the timing of the new transducer sample position is one of serially-transmitted timing data and parallel-transmitted timing data, output by the transducer signal processing circuit and input by the estimated position signal generating circuit.

6. The position monitoring system of claim 1, wherein;

the interface circuit includes elements that determine the timing of the particular approximated position output;

the transducer sample position value output interval is determined by one of the transducer signal processing circuit and the interface circuit based at least partially on timing information generated in the interface circuit corresponding to the timing of the particular approximated position output.

7. The position monitoring system of claim 6, wherein the timing information corresponding to the timing of the particular approximated position output is a timing signal output by the estimated position signal generating circuit and input by the transducer signal processing circuit.

8. The position monitoring system of claim 1, wherein the ratio of the nominal approximated position output cycle interval to the minimum transducer sample position output interval allows at least 500 approximated position outputs during the minimum possible transducer sample position output interval.

9. The position monitoring system of claim 8, wherein the ratio of the nominal approximated position output cycle interval to the minimum possible transducer sample position output interval allows at least 1800 approximated position outputs during the minimum possible transducer sample position output interval.

10. The position monitoring system of claim 1, wherein the position transducer comprises an inductive position transducer and the approximated position output approximating the position of the position transducer comprises a quadrature output.

11. The position monitoring system of claim 10, wherein the inductive position transducer comprises an absolute inductive position transducer.

12. The position monitoring system of claim 10, wherein the transducer signal processing circuit comprises a symmetric sampling transducer signal processing circuit.

13. The position monitoring system of claim 10, wherein the approximated position output cycle interval corresponds to a maximum quadrature signal frequency, and the maximum quadrature signal frequency is greater than 500 Kilohertz, corresponding to a quadrature counting frequency of 2 million counts per second.

14. The position monitoring system of claim 13, wherein the maximum quadrature signal frequency is greater than 2.5 megahertz, corresponding to a quadrature counting frequency of 10 million counts per second.

15. A position monitoring system, comprising:

a position transducer;

a transducer signal processing circuit operably connectable to the position transducer; and

an interface circuit operably connectable to the transducer signal processing circuit, the interface circuit including an estimated position generating circuit that generates approximated position outputs approximating the position of the position transducer, at a plurality of times between the times that the transducer signal processing circuit generates discrete transducer sample position output values corresponding to the actual position of the position transducer;

wherein;

the transducer signal processing circuit generates a discrete transducer sample position value output, corresponding to the actual position of the position transducer, at a particular time;

the transducer signal processing circuit generates a timing information signal corresponding to the particular time; and

the transducer sample position value output and the corresponding timing information signal corresponding to the particular time are output to the estimated position generating circuit.

16. The position monitoring system of claim 15, wherein the timing information signal corresponding to the particular time is one of a signal usable to operate a value-latching circuit, a serially-transmitted timing data signal and a parallel-transmitted timing data signal.

17. The position monitoring system of claim 15, wherein the timing information signal corresponding to the particular time is output at a time which is not the particular time.

18. The position monitoring system of claim 15, wherein:

the estimated position generating circuit generates the approximated position outputs according to a nominal approximated position output cycle interval which is shorter than a minimum transducer sample position value output interval of the transducer signal processing circuit;

the transducer signal processing circuit is operably connected to the position transducer and to the estimated position generating circuit;

the transducer signal processing circuit outputs the generated discrete transducer sample position value output corresponding to the actual position of the position transducer at a particular time, and the generated timing information signal corresponding to the particular time, to the estimated position generating circuit;

the estimated position generating circuit generates a first plurality of approximated position outputs that are incremented at a first rate prior to receiving one of the generated discrete transducer sample position value outputs corresponding to the actual position of the position transducer at a particular time and the generated timing information signal corresponding to the particular time; and

the estimated position generating circuit generates a second plurality of approximated position outputs that are incremented at a second rate after receiving the one of the generated discrete transducer sample position outputs corresponding to the position of the position transducer at the particular time and the generated timing information signal corresponding to the particular time, the second rate based at least partially on the one of the generated discrete transducer sample position value outputs corresponding to the actual position of the position transducer at the particular time, the generated timing information signal corresponding to the particular time, and an approximated position output corresponding to the particular time.

19. The position monitoring system of claim 18, wherein the position generating circuit is remotely located from the transducer signal processing circuit.

20. The position monitoring system of claim 18, wherein the estimated position generating circuit comprises at least a portion of one of a special-purpose custom digital circuit, a programmed commercial gate array, a programmed commercial digital signal processing circuit, a programmed general-purpose computer, a programmed motion-controller, a general-purpose computer, and a programmed computer used as a motion control system host.

21. A method for operating a position monitoring system, the position monitoring system comprising:

a position transducer;

a transducer signal processing circuit operably connectable to the position transducer; and

an interface circuit including an estimated position signal generating circuit operably connectable to the transducer signal processing circuit;

the method comprising;

generating a transducer sample position value output corresponding to the actual position of the position transducer, according to a transducer sample position output interval that is not less that a minimum transducer sample position output interval, using the transducer signal processing circuit;

generating approximated position outputs using the estimated position signal generating circuit, according to an approximated position output cycle interval which is shorter than the minimum transducer sample position output interval, at a plurality of times between the generating of transducer sample position value outputs corresponding to the actual position of the position transducer;

incrementing the approximated position output by a prescribed increment amount during each approximated position output cycle;

adjusting the prescribed increment amount when a new transducer sample position value output corresponding to the actual position of the position transducer is available, wherein the adjustment of the prescribed increment amount is based at least partially on a determined difference between a particular approximated position output and the new transducer sample position value.

22. The method of claim 21, further comprising selecting the particular approximated position output based on timing information corresponding to the timing of the new transducer sample position value corresponding to the actual position.

23. The method of claim 22, wherein the timing information corresponding to the timing of the new transducer sample position value is a value-latching signal, and selecting the particular approximated position output comprises outputting the value-latching signal from the transducer signal processing circuit, inputting the value-latching signal to the estimated position signal generating circuit, and latching an approximated position output that is used as the particular approximated position output.

24. The position monitoring system of claim 22, wherein the timing information corresponding to the timing of the new transducer sample position is one of serially-transmitted timing data and parallel-transmitted timing data, output by the transducer signal processing circuit and input by the estimated position signal generating circuit, and selecting the particular approximated position output comprises selecting an approximated position output that is used as the particular approximated position output, based on the one of serially-transmitted timing data and parallel-transmitted timing data.

25. The method of claim 21, wherein generating approximated position outputs using the estimated position signal generating circuit, according to an approximated position output cycle interval which is shorter than the minimum transducer sample position output interval comprises generating at least 500 approximated position outputs during the minimum possible transducer sample position output interval.

26. The method of claim 21, wherein generating approximated position outputs comprises generating at least 1800 approximated position outputs during the minimum possible transducer sample position output interval.

27. The method of claim 21, wherein generating approximated position outputs comprises generating quadrature outputs.

28. The position monitoring system of claim 21, wherein the position transducer is an inductive position transducer and the operation of generating a transducer sample position value output corresponding to the actual position of the position transducer comprises generating an absolute position value.

29. The position monitoring system of claim 21, wherein the transducer signal processing circuit operably connectable to the position transducer comprises a symmetric sampling transducer signal processing circuit.