Systems and methods for extracting system parameters from nonlinear periodic signals from sensors

• US 9,910,061 B2
• Filed: 06/26/2015
• Issued: 03/06/2018
• Est. Priority Date: 06/26/2014
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Lumedyne Technologies Incorporated (Alphabet Inc.)
• Inventors: Waters, Richard Lee, Jacobs, John David, Tally, IV, Charles Harold, Huang, Xiaojun, Zhang, Yanting, Fralick, Mark Steven
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US14/751,465
• Publication Number:
  US 20150377917A1
• Time in Patent Office: 984 Days
• CPC Class Codes: G01C 19/5705 using masses driven in reciprocating rotary motion about an axis
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

Systems and methods are disclosed herein for extracting system parameters from nonlinear periodic signals from sensors. A sensor such as an inertial device includes a first structure and a second structure that is springedly coupled to the first structure. The sensor is configured to generate an output voltage based on a current between the first and second structures. Monotonic motion of the second structure relative to the first structure causes a reversal in direction of the current.

Claims

1. A method of processing a nonlinear periodic signal, the method comprising:

receiving a nonlinear periodic input signal from an inertial sensor comprising a fixed element that includes a first plurality of equally spaced teeth and a moveable element that includes a second plurality of equally spaced teeth, the nonlinear periodic input signal experiencing a nonmonotonic change responsive to monotonic motion of the second plurality of equally spaced teeth relative to the first plurality of equally spaced teeth;

converting the nonlinear periodic input signal to a two-valued signal having first and second values, based at least in part on the nonmonotonic change;

determining first and second transition times between the first and second values;

applying a trigonometric function to a time signal comprising the first and second transition times to determine a trigonometric result; and

extracting an inertial parameter of the inertial sensor from the trigonometric result.

2. The method of claim 1, wherein applying the trigonometric function to the time signal comprising the first and second transition times further comprises:

determining a first time interval between the first and second transition times; and

applying the trigonometric function to the time signal comprising the first time interval to determine the trigonometric result.

3. The method of claim 1, wherein receiving the nonlinear periodic input signal comprises:

receiving a first nonlinear periodic signal;

receiving a second nonlinear periodic signal; and

combining the first and second nonlinear periodic signals to result in the nonlinear periodic input signal.

4. The method of claim 1, wherein converting the nonlinear periodic input signal into the two-valued signal comprises:

comparing a value of the nonlinear periodic input signal to a threshold;

if the value of the nonlinear periodic input signal is above the threshold, assigning a first value to the two-valued signal to correspond to the value of the nonlinear periodic input signal; and

if the value of the nonlinear periodic input signal is below the threshold, assigning a second value to the two-valued signal to correspond to the value of the nonlinear periodic input signal.

5. The method of claim 4, wherein determining a plurality of transition times comprises:

comparing the two-valued signal to an immediately previous value of the two-valued signal;

if the two-valued signal is above the immediately previous value, determining that the first transition time corresponds to a rising edge of the two-valued signal; and

if the two-valued signal is below the immediately previous value, determining that the first transition time corresponds to a falling edge of the two-valued signal.

6. The method of claim 2, wherein applying the trigonometric function to the time signal comprising the first time interval further comprises:

receiving a second time interval;

determining a sum of the first and second time intervals;

determining a ratio of one of the first and second time intervals to the sum;

determining an argument based on the ratio; and

applying a trigonometric function to the argument.

7. The method of claim 1, wherein extracting the inertial parameter from the trigonometric result comprises:

determining a physical displacement of an oscillating element based on the trigonometric result; and

determining the inertial parameter based on the physical displacement.

8. The method of claim 7, wherein the physical displacement is determined based on a plurality of trigonometric results.

9. The method of claim 8, wherein the physical displacement is determined based on a ratio including the plurality of trigonometric results.

10. The method of claim 7, wherein determining the inertial parameter comprises:

determining an offset in the physical displacement; and

determining the inertial parameter based on the offset.

11. The method of claim 10, wherein:

the inertial parameter is an acceleration of the inertial sensor; and

the offset is proportional to the acceleration.

12. A system for processing a nonlinear periodic signal, the system comprising:

an inertial sensor comprising a fixed element that includes a first plurality of equally spaced teeth and a moveable element that includes a second plurality of equally spaced teeth, the moveable element disposed proximate to the fixed element to enable monotonic motion of the second plurality of equally spaced teeth, relative to the first plurality of equally spaced teeth, to cause a nonmonotonic change in a nonlinear periodic input signal; and

control circuitry configured for;

receiving the nonlinear periodic input signal from the inertial sensor;

converting the nonlinear periodic input signal to a two-valued signal having first and second values, based at least in part on the nonmonotonic change;

determining first and second transition times between the first and second values;

applying a trigonometric function to a time signal comprising the first and second transition times to determine a trigonometric result; and

extracting an inertial parameter of the inertial sensor from the trigonometric result.

13. The system of claim 12, wherein applying the trigonometric function to the time signal comprising the first and second transition times further comprises:

determining a first time interval between the first and second transition times; and

applying the trigonometric function to the time signal comprising the first time interval to determine the trigonometric result.

14. The system of claim 12, wherein the control circuitry is configured for receiving the nonlinear periodic input signal by:

receiving a first nonlinear periodic signal;

receiving a second nonlinear periodic signal; and

combining the first and second nonlinear periodic signals to result in the nonlinear periodic input signal.

15. The system of claim 12, wherein the control circuitry is configured for converting the nonlinear periodic input signal into the two-valued signal by:

comparing a value of the nonlinear periodic input signal to a threshold;

if the value of the nonlinear input periodic signal is above the threshold, assigning a first value to the two-valued signal to correspond to the value of the nonlinear periodic input signal; and

if the value of the nonlinear periodic input signal is below the threshold, assigning a second value to the two-valued signal to correspond to the value of the nonlinear periodic input signal.

16. The system of claim 15, wherein the control circuitry is configured for determining a plurality of transition times by:

comparing the two-valued signal to an immediately previous value of the two-valued signal;

if the two-valued signal is above the immediately previous value, determining that the first transition time corresponds to a rising edge of the two-valued signal; and

if the two-valued signal is below the immediately previous value, determining that the first transition time corresponds to a falling edge of the two-valued signal.

17. The system of claim 13, wherein the control circuitry is configured for applying the trigonometric function to the time signal comprising the first time interval further by:

receiving a second time interval;

determining a sum of the first and second time intervals;

determining a ratio of one of the first and second time intervals to the sum;

determining an argument based on the ratio; and

applying a trigonometric function to the time signal.

18. The system of claim 12, wherein the control circuitry is configured for extracting the inertial parameter from the trigonometric result by:

determining a physical displacement of an oscillating element based on the trigonometric result; and

determining the inertial parameter based on the physical displacement.

19. The system of claim 18, wherein the control circuitry is configured for determining the physical displacement based on a plurality of trigonometric results.

20. The system of claim 19, wherein the control circuitry is configured for determining the physical displacement based on a ratio including the plurality of trigonometric results.

21. The system of claim 18, wherein the control circuitry is configured for determining the inertial parameter by:

determining an offset in the physical displacement; and

determining the inertial parameter based on the offset.

22. The system of claim 21, wherein:

the inertial parameter is an acceleration of the inertial sensor; and

the offset is proportional to the acceleration.