SYSTEM AND METHOD FOR ESTIMATING DISTANCE BETWEEN A MOBILE UNIT AND A VEHICLE USING A TOF SYSTEM

• US 20160077200A1
• Filed: 11/20/2015
• Published: 03/17/2016
• Est. Priority Date: 04/12/2011
• Status: Active Application

• Current Assignee: Magna Electronics Incorporated (Magna International Incorporated)
• Original Assignee: Magna Electronics Incorporated (Magna International Incorporated)
• Inventors: HASSAN, Hasib, Benton, Dale R., Lu, John, Gorman, Brian A.
• Granted Patent: US 10,288,724 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 11/08 using synchronised clocks

Abstract

A method of estimating a distance between a mobile unit and a vehicle includes providing a time of flight subsystem including circuitry incorporated in the mobile unit and circuitry incorporated in the vehicle, and generating a time of flight distance signal by periodically transmitting a time of flight signal between the mobile unit and the vehicle and measuring the time taken for transmission of the time of flight signal therebetween. A travel sensor is disposed at the mobile unit and generates a travel sensor signal. A value of a distance estimate signal is initialized based on the time of flight distance signal. A movement of the mobile unit is determined based on variance in the travel sensor signal. The initialized value of the initialized distance estimate signal is changed or increased or decreased based upon determination of movement of the mobile unit.

Claims

1. A method of estimating distance between a mobile unit and a vehicle, said method comprising:

providing a time of flight subsystem including circuitry incorporated in the mobile unit and circuitry incorporated in the vehicle;

generating a time of flight distance signal by periodically transmitting a time of flight signal between the mobile unit and the vehicle and measuring the time taken for transmission of the time of flight signal between the mobile unit and the vehicle;

disposing a travel sensor at the mobile unit;

generating a travel sensor signal using the travel sensor;

initializing a value of a distance estimate signal based on the time of flight distance signal;

determining movement of the mobile unit based on variance in the travel sensor signal; and

changing the initialized value of the initialized distance estimate signal based upon determination of movement of the mobile unit, wherein the value of the initialized distance estimate signal is increased responsive to the time of flight distance signal being greater than the initialized distance estimate signal, and wherein the value of the initialized distance estimate signal is decreased responsive to the time of flight distance signal being less than the initialized distance estimate signal.

2. The method of claim 1, including passing a raw time of flight distance signal generated by the time of flight subsystem through a smoothing filter to thereby generate a smoothed time of flight distance signal utilized by said changing step.

3. The method of claim 2, wherein the smoothing filter comprises a digital biased median filter that is biased low.

4. The method of claim 2, wherein whether the smoothed time of flight distance signal is greater than or less than the initialized distance estimate signal is determined based on the value of the smoothed time of flight distance signal at substantially the same instant in time when movement of the mobile unit is determined.

5. The method of claim 2, wherein whether the smoothed time of flight distance signal is greater than or less than the initialized distance estimate signal is determined based on an average of the smoothed time of flight distance signal as generated over a period of time.

6. The method of claim 1, including passing a raw travel sensor signal generated by the travel sensor through a smoothing filter.

7. The method of claim 6, wherein the smoothing filter comprises a digital median filter.

8. The method of claim 6, wherein determining movement of the mobile unit includes examining the smoothed travel sensor signal for the occurrence of two serial local peaks, each of which exceeds an amplitude and occurs within a range of time periods indicative of human gait.

9. The method of claim 8, wherein determining movement of the mobile unit further includes examining the smoothed travel sensor signal for a slope within a predetermined range of slopes indicative of human gait.

10. The method of claim 1, wherein the value of the initialized distance estimate signal is changed by a different amount depending on whether the initialized distance estimate signal is being increased or decreased.

11. A method of estimating distance between a mobile unit and a vehicle, said method comprising:

providing a time of flight subsystem including circuitry incorporated in the mobile unit and circuitry incorporated in the vehicle;

generating a time of flight distance signal by periodically transmitting a time of flight signal between the mobile unit and the vehicle and measuring the time taken for transmission of the time of flight signal between the mobile unit and the vehicle;

disposing a travel sensor at the mobile unit;

generating a travel sensor signal using the travel sensor;

initializing a value of a distance estimate signal based on the time of flight distance signal;

determining movement of the mobile unit based on variance in the travel sensor signal;

changing the initialized value of the initialized distance estimate signal based upon determination of movement of the mobile unit, wherein the value of the initialized distance estimate signal is increased responsive to the time of flight distance signal being greater than the initialized distance estimate signal, and wherein the value of the initialized distance estimate signal is decreased responsive to the time of flight distance signal being less than the initialized distance estimate signal;

wherein whether the time of flight distance signal is greater than or less than the initialized distance estimate signal is determined based on an average of the time of flight distance signal as generated over a period of time; and

wherein determining movement of the mobile unit includes examining the travel sensor signal for the occurrence of two serial local peaks, each of which exceeds an amplitude and occurs within a range of time periods indicative of human gait.

12. The method of claim 11, including passing a raw time of flight distance signal generated by the time of flight subsystem through a smoothing filter to thereby generate a smoothed time of flight distance signal utilized by said changing step.

13. The method of claim 11, including passing a raw travel sensor signal generated by the travel sensor through a smoothing filter.

14. The method of claim 11, wherein whether the time of flight distance signal is greater than or less than the initialized distance estimate signal is determined based on the value of the time of flight distance signal at substantially the same instant in time when movement of the mobile unit is determined.

15. The method of claim 11, wherein determining movement of the mobile unit further includes examining the travel sensor signal for a slope within a predetermined range of slopes indicative of human gait.

16. The method of claim 11, wherein the value of the initialized distance estimate signal is changed by a different amount depending on whether the initialized distance estimate signal is being increased or decreased.

17. A method of estimating distance between a mobile unit and a vehicle, said method comprising:

providing a time of flight subsystem including circuitry incorporated in the mobile unit and circuitry incorporated in the vehicle;

generating a time of flight distance signal by periodically transmitting a time of flight signal between the mobile unit and the vehicle and measuring the time taken for transmission of the time of flight signal between the mobile unit and the vehicle;

disposing a travel sensor at the mobile unit;

generating a travel sensor signal using the travel sensor;

initializing a value of a distance estimate signal based on the time of flight distance signal;

determining movement of the mobile unit based on variance in the travel sensor signal;

changing the initialized value of the initialized distance estimate signal based upon determination of movement of the mobile unit, wherein the value of the initialized distance estimate signal is increased responsive to the time of flight distance signal being greater than the initialized distance estimate signal, and wherein the value of the initialized distance estimate signal is decreased responsive to the time of flight distance signal being less than the initialized distance estimate signal;

passing a raw time of flight distance signal generated by the time of flight subsystem through a smoothing filter to thereby generate a smoothed time of flight distance signal utilized by said changing step; and

passing a raw travel sensor signal generated by the travel sensor through another smoothing filter.

18. The method of claim 17, wherein whether the smoothed time of flight distance signal is greater than or less than the initialized distance estimate signal is determined based on at least one of (i) the value of the smoothed time of flight distance signal at substantially the same instant in time when movement of the mobile unit is determined, and (ii) an average of the smoothed time of flight distance signal as generated over a period of time.

19. The method of claim 17, wherein determining movement of the mobile unit includes at least one of (i) examining the smoothed travel sensor signal for the occurrence of two serial local peaks, each of which exceeds an amplitude and occurs within a range of time periods indicative of human gait, and (ii) examining the smoothed travel sensor signal for a slope within a predetermined range of slopes indicative of human gait.

20. The method of claim 17, wherein the value of the initialized distance estimate signal is changed by a different amount depending on whether the initialized distance estimate signal is being increased or decreased.