Method for analytical reconstruction of digital signals via stitched polynomial fitting

• US 9,715,480 B1
• Filed: 03/20/2013
• Issued: 07/25/2017
• Est. Priority Date: 06/24/2011
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Swanson, Paul David, Tally, Charles H., Waters, Richard L.
• Primary Examiner(s): Saxena, Akash
• Assistant Examiner(s): KU, SHIUH-HUEI P
• Application Number:
  US13/847,521
• Time in Patent Office: 1,588 Days
• Field of Search: 703 2, 703 6, 703 7
• CPC Class Codes: G01C 7/04 involving a vehicle which moves along the profile to be traced
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator

Abstract

A method for approximating the behavior of a periodic parameter of a time-domain device in response to a perturbation, the method comprising the following steps: collecting data points at discreet times, wherein each data point represents a measurement of the parameter; dividing the time domain into intervals, each given interval containing at least one data point sampled during the given interval; fitting a polynomial function to the data points of each interval such that each interval has a corresponding polynomial function that is time-centered on the interval'"'"'s center point and that accurately describes the parameter behavior over that interval; and stitching together the polynomial functions piece-wise to create an analytic approximation of the behavior of the system parameter over the entire time domain.

Claims

1. A method for approximating the behavior of a periodic parameter of a time-domain proximity switch accelerometer in response to a perturbation, the method comprising the following steps:

generating a triggering event when a first element of a switch within the time-domain proximity switch accelerometer passes a second element of the switch, wherein the first element is in oscillation and the second element is located at a fixed trigger position of one or more fixed trigger positions within the amplitude range of the oscillation, wherein the fixed trigger positions are predefined physical locations with respect to a reference position of the first element;

determining at least one time period between successive triggering events;

using the at least one time period and the fixed trigger position of the second element to determine the periodic parameter;

collecting data points at discrete times, wherein each data point represents a measurement of the parameter;

forming a preliminary approximation of the behavior of the system parameter by calculating an offset bias of the time-domain proximity switch accelerometer due to the perturbation;

dividing the time domain into intervals, each given interval containing at least one data point sampled during the given interval;

fitting a polynomial function to the data points of each interval such that each interval has a corresponding polynomial function that is time-centered on the interval'"'"'s center point and that accurately describes the parameter behavior over that interval;

stitching together the polynomial functions piece-wise to create an analytic approximation of the behavior of the periodic parameter over the entire time domain; and

altering a navigational course of a moving vehicle based on the preliminary approximation and correcting the altered navigational course based on the analytic approximation.

2. The method of claim 1, wherein the stitching step is performed by summing the polynomial functions of each interval.

3. The method of claim 2, wherein the parameter is a time-dependent system variable x(t) of the time-domain proximity switch accelerometer.

4. The method of claim 2, wherein the parameter is a measurable system variable y(z) which depends on a measurable system variable other than time.

5. The method of claim 1, wherein the parameter is a closed switch state.

6. The method of claim 2, wherein the intervals are not uniform but are of arbitrary length.

7. The method of claim 2, wherein the intervals are of equal length.

8. The method of claim 2, wherein the data points are collected at a non-constant sampling rate.

9. The method of claim 2, wherein the data points are collected at a constant sampling rate.

10. The method of claim 2, wherein the perturbation is a physical acceleration of the time-domain proximity switch accelerometer.

16. The method of claim 1, wherein the first element and the second element comprise electron tunneling electrodes and the triggering event is a tunneling current between the first element and the second element.

17. The method of claim 1, wherein the step of using the at least one time period to determine the periodic parameters comprises using a time period between successive triggering events with respect to the same fixed trigger position.

18. The method of claim 1, wherein the first element is disposed on a proof mass assembly and the second element is disposed on a frame fixed in location with respect to the proof mass assembly.

11. A method for approximating the behavior of a system parameter x(t) of a time-domain proximity switch accelerometer in response to a perturbation, the method comprising the following steps:

generating a triggering event when a first element of a switch within the time-domain proximity switch accelerometer passes a second element of the switch, wherein the first element is in oscillation and the second element is located at a fixed trigger position of one or more fixed trigger positions within the amplitude range of the oscillation, wherein the fixed trigger positions are predefined physical locations with respect to a reference position of the first element;

determining at least one time period between successive triggering events;

measuring the parameter at discrete times, [x_i, t_i];

forming a preliminary approximation of the behavior of the system parameter by calculating an offset bias of the time-domain proximity switch accelerometer due to the perturbation;

dividing the time domain into n time intervals of length Δ

t, each given interval containing at least k+1 discrete measurements of parameter x(t), wherein k and n are both positive integers greater than 1;

fitting a k^th order polynomial function P_n^k(t) to the measurements of each interval such that each interval has a corresponding polynomial function P_n^k (t), thereby approximating parameter x(t) during each interval;

stitching together the polynomial functions piece-wise to create a smooth, analytic approximation of the behavior of the system parameter x(t) over the entire time domain; and

altering a navigational course of a moving vehicle based on the preliminary approximation and correcting the altered navigational course based on the analytic approximation.

12. The method of claim 11, wherein the polynomial function P_n^k(t) is defined as follows:

13. The method of claim 12, wherein stitching step is accomplished by time shifting each polynomial fit to its corresponding interval'"'"'s center point (T_n) and summing the time-centered polynomials as follows:

14. A method for approximating the behavior of a system parameter of a time-domain proximity switch accelerometer in response to a perturbation, the method comprising the following steps:

generating a triggering event when a first element of a switch within the time-domain proximity switch accelerometer passes a second element of the switch, wherein the first element is in oscillation and the second element is located at a fixed trigger position of one or more fixed trigger positions within the amplitude range of the oscillation, wherein the fixed trigger positions are predefined physical locations with respect to a reference position of the first element;

determining at least one time period between successive triggering events;

collecting data points at discrete times while the first element is at a known reference position and while the device is subjected to the perturbation, wherein each data point represents a measurement of the parameter;

forming a preliminary approximation of the behavior of the system parameter by calculating an offset bias of the time-domain proximity switch accelerometer due to the perturbation;

dividing the time domain into intervals, each given interval containing at least three data points sampled during the given interval;

fitting a polynomial function to the data points of each interval such that each interval has a corresponding polynomial function;

stitching together the polynomial functions piece-wise to create an analytic approximation of the behavior of the system parameter over the entire time domain;

correcting the preliminary behavior approximation by comparing it to the analytic behavior approximation; and

altering a navigational course of a moving vehicle based on the preliminary approximation and correcting the altered navigational course based on the analytic approximation.

15. The method of claim 14, wherein the step of calculating the offset bias is accomplished by assuming the parameter behaves exactly as a cosine function with a fixed offset and by comparing time periods between successive data points measured while the device is in the reference position to successive data points measured while the device is subjected to the perturbation.