Method for acoustic distance time of flight compensation

1. A method comprising:

generating an acoustic signal for an acoustic transducer at a first time, wherein the acoustic transducer transmits the acoustic signal to determine a first position of an obstacle;

detecting a pulse at the acoustic transducer in response to the acoustic signal encountering the obstacle within a predetermined distance;

detecting a second time in response to a rising edge of the pulse intersecting a determined threshold, the determined threshold having a first magnitude;

detecting a peak magnitude of the pulse; and

determining a time of flight of the acoustic signal within the predetermined distance by extracting a compensation time from a correction look up table in response to detecting the first magnitude and the peak magnitude, and subtracting the compensation time from the second time to determine the time of flight, wherein the determining comprises determining a correction ratio of the determined threshold to the peak magnitude of the pulse, and wherein the correction look up table determines the compensation time corresponding to the correction ratio.

2. The method of claim 1 , further comprising:

estimating the first position of the obstacle within the predetermined distance, wherein the time of flight corresponds to a detection of the first position of the obstacle.

3. The method of claim 1 , further comprising:

detecting the rising edge of the pulse; and

in response to detecting the rising edge of the pulse at the determined threshold, storing the first time and the first magnitude.

4. The method of claim 3 , further comprising:

in response to detecting the peak magnitude, storing the peak magnitude.

5. The method of claim 4 , further comprising:

determining a ratio of the first magnitude and the peak magnitude.

6. The method of claim 5 , wherein determining the ratio further comprises providing the ratio of the first magnitude and the peak magnitude, multiplied by a factor of one hundred to the correction look up calculation table.

7. The method of claim 6 , further comprising:

extracting the compensation time from the correction look up table, wherein the compensation time corresponds to the ratio of the first magnitude and the peak magnitude within the correction look up table.

8. The method of claim 1 , further comprising:

detecting a start of the pulse in response to the acoustic signal intersecting the obstacle; and

in response to receiving the first magnitude when the pulse intersects the determined threshold, determining a quality factor time delay, wherein the quality factor time delay determines a maximum time to receive transmission of a pulse measurement before a time-of-flight measurement is provided to a controller.

9. The method of claim 8 , further comprises:

determining when the quality factor time delay is greater than a peak detection time;

in response to the quality factor time delay being less than the peak detection time, dynamically increasing the quality factor time delay thereby increasing a response time of a corresponding digital filter; and

providing a corrected quality factor time delay to the controller as an adjusted maximum time of flight.

10. The method of claim 1 , further comprising:

receiving programmable values corresponding to the determined threshold, wherein the determined threshold is a time varying threshold.

11. The method of claim 1 , further comprising:

filtering the acoustic signal from the acoustic transducer to provide a filtered signal; and

detecting the obstacle in response to receiving the filtered signal.

12. A method for acoustic distance measurement, comprising:

generating an acoustic signal with an acoustic transducer at a first time;

detecting a pulse with the acoustic transducer in response to the acoustic signal encountering an obstacle within a predetermined distance, wherein detecting the pulse comprises:

detecting a second time relative to the first time when a magnitude of the pulse rises above a predetermined threshold, and

detecting a peak magnitude of the pulse;

determining a correction ratio as a ratio of the predetermined threshold to the peak magnitude of the pulse;

determining a compensation time in response to the correction ratio; and

determining a corrected time of flight by subtracting the compensation time from the second time.

13. The method of claim 12 , wherein determining the compensation time in response to the correction ratio comprises:

using the correction ratio to index into a correction look up table; and

determining the compensation time as an output of the correction look up table.

14. The method of claim 13 , wherein determining the correction ratio comprises multiplying the ratio of the predetermined threshold to the peak magnitude of the pulse by a factor of one hundred.

15. The method of claim 12 , further comprising:

in response to the pulse intersecting the predetermined threshold, determining a quality factor time delay, wherein the quality factor time delay indicates a maximum time to receive transmission of a pulse measurement; and

providing a time-of-flight measurement to a controller in response to the quality factor time delay.

16. The method of claim 15 , further comprises:

determining when the quality factor time delay is greater than a peak detection time;

in response to the quality factor time delay being less than the peak detection time, dynamically increasing the quality factor time delay thereby increasing a response time of a corresponding digital filter; and

providing a corrected quality factor time delay to the controller as an adjusted maximum time of flight.

17. The method of claim 12 , further comprising:

measuring background noise; and

varying the predetermined threshold in response to the background noise.

18. The method of claim 12 , further comprising:

converting a signal received from the acoustic transducer to a digital signal;

filtering the digital signal to provide a filtered signal; and

detecting the obstacle in response to the digital signal.

19. The method of claim 12 , wherein:

detecting the second time relative to the first time comprises detecting the second time with a rising edge detector circuit; and

detecting the peak magnitude of the pulse comprises detecting the peak magnitude using a peak detector circuit.

20. The method of claim 12 , wherein adjusting the second time by the compensation time comprises subtracting the compensation time from the second time.