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

• US 20040094338A1
• Filed: 11/15/2002
• Published: 05/20/2004
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Skurnik, David
• Granted Patent: US 7,094,978 B2
• Time in Patent Office: Days
• 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 output signals for a position encoder is provided. The system produces an approximated position signal that is updated at a rate higher than a base rate of the measured transducer position signals. The approximated position signals may be utilized to produce quadrature outputs that are compatible with existing control systems. The measured transducer position signals are processed and/or stored by a signal processing circuit at discrete time intervals. The approximated position values are generated by a high frequency position estimation circuit. The approximated position signal is then compared by an error correction feedback loop to the measured transducer position signal and the resulting difference stored in an error register for use by the error correction feedback loop during the next discrete time interval. In one embodiment, the accuracy of the system may be further improved by utilizing a latch signal to ensure that the approximated position signal and the measured transducer position signal 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

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

wherein;

the transducer signal processing circuit generates a transducer sample position output corresponding to the 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; and

the position signal generating circuit generates an approximated position output approximating the position of the position transducer, according to an approximated position output cycle interval which is shorter than the minimum transducer sample position output interval; and

wherein the approximated position output is incremented by a prescribed increment amount during the approximated position output cycle, and the prescribed increment amount is adjusted when a new transducer sample position output becomes available, and the adjustment is based at least partially on a difference between a difference-determining approximated position output and the new transducer sample position.

2. The position monitoring system of claim 1, wherein at least one of the position transducer and the transducer signal processing circuit and the position signal generating circuit is operably connectable to at least one other of the position transducer and the transducer signal processing circuit and the 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 difference-determining approximated position output is selected by one of the transducer signal processing circuit and the 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 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 position signal generating circuit.

6. The position monitoring system of claim 1, wherein the transducer sample position output interval corresponding to the sample timing of the new transducer sample position is determined by one of the transducer signal processing circuit and the position signal generating circuit based on timing information corresponding to the timing of the difference-determining approximated position output.

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 operably connectable to the position transducer 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.

7. The position monitoring system of claim 7, wherein the timing information corresponding to the timing of the difference-determining approximated position output is an approximated position timing signal output by the position signal generating circuit and input by the transducer signal processing circuit.

15. A position monitoring system, comprising:

a position transducer;

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

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

wherein;

the transducer signal processing circuit generates a discrete transducer sample position output corresponding to the 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 output and the corresponding timing information signal corresponding to the particular time are outputtable to the position generating circuit.

16. The position monitoring system of claim 15, wherein the corresponding 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 corresponding 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, further comprising an approximated position generating circuit that generates an approximated position output approximating the position of the position transducer according to a nominal approximated position output cycle interval which is shorter than a minimum transducer sample position output interval of the position transducer, wherein:

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

wherein;

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

the approximated 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 outputs corresponding to the position of the position transducer at a particular time and the generated timing information signal corresponding to the particular time; and

the approximated 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 position transducer at a 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 outputs corresponding to the position of the position transducer at a 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 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.