Acoustic sensing of proximate obstacles
An illustrative controller includes: a transmitter to drive an acoustic transducer to generate a first acoustic burst and a second acoustic burst; a receiver coupled to the acoustic transducer to sense a first response to the first acoustic burst and a second response to the second acoustic burst; and a processing circuit to derive output data from the first and second responses in part by determining an offset frequency difference between the first and second responses, wherein the first acoustic burst has a first characteristic frequency and the second acoustic burst has a second characteristic frequency different from the first characteristic frequency.
1. A controller for an acoustic transducer, the controller comprising:
a transmitter to drive the acoustic transducer to generate a first acoustic burst and a second acoustic burst;
a receiver coupled to the acoustic transducer to sense a first response to the first acoustic burst and a second response to the second acoustic burst; and
a processing circuit to derive output data from the first response and the second response in part by determining an offset frequency difference between the first response and the second response, wherein the first acoustic burst has a first characteristic frequency and the second acoustic burst has a second characteristic frequency different from the first characteristic frequency.
2. The controller of claim 1 , wherein the transmitter is configured to drive the acoustic transducer to generate a third acoustic burst, the third acoustic burst having the first characteristic frequency, wherein the receiver is configured to sense a third response to the third acoustic burst, and wherein the processing circuit is configured to determine an aligned frequency difference between the first response and the third response.
3. The controller of claim 2 , wherein the processing circuit is configured to compare a magnitude of the offset frequency difference and a magnitude of the aligned frequency difference to a threshold to detect any nearby obstacles.
4. The controller of claim 1 , wherein a third response is obtained from the second acoustic burst, the third response accounting for an offset between the first characteristic frequency and the second characteristic frequency, wherein the processing circuit is configured to determine an aligned frequency difference between the first response and the third response, and wherein the processing circuit is configured to compare a magnitude of the offset frequency difference and a magnitude of the aligned frequency difference to a threshold to detect any nearby obstacles.
5. The controller of claim 1 , wherein the processing circuit is configured to compare a magnitude of the offset frequency difference to a threshold to detect any nearby obstacles.
6. The controller of claim 1 , wherein the processing circuit is configured to compare a magnitude of the offset frequency difference to a threshold to determine a distance to an obstacle.
7. The controller of claim 1 , wherein the first acoustic burst and the second acoustic burst are adjacent in a series of acoustic bursts having characteristic frequencies that alternate between the first characteristic frequency and the second characteristic frequency.
8. The controller of claim 1 , wherein the first acoustic burst and the second acoustic burst each have a burst length that is shorter than acoustic bursts generated by the acoustic transducer to detect more distant obstacles.
9. A sensing method that comprises:
sensing the response of an acoustic transducer to each acoustic burst in a series of acoustic bursts, the series including a first acoustic burst and a second acoustic burst;
determining an offset frequency difference between a response to the first acoustic burst and a response to the second acoustic burst, wherein the first acoustic burst has a first characteristic frequency and the second acoustic burst has a second characteristic frequency different from the first characteristic frequency; and
operating on the offset frequency difference to determine whether an obstacle is nearby.
10. The sensing method of claim 9 , wherein the series includes a third acoustic burst, the third acoustic burst having the first characteristic frequency, and the method further comprises:
determining an aligned frequency difference between the response to the first acoustic burst and the third response; and
operating on the aligned frequency difference to determine whether an obstacle is nearby.
11. The sensing method of claim 10 , wherein said operating on the offset frequency difference includes comparing a magnitude of the offset frequency difference to a threshold and said operating on the aligned frequency difference includes comparing a magnitude of the aligned frequency difference to the threshold.
12. The sensing method of claim 9 , further comprising:
obtaining a compensated response to the second acoustic burst, the compensated response accounting for an offset between the first characteristic frequency and the second characteristic frequency; and
determining an aligned frequency difference between the response to the first acoustic burst and the compensated response; and
operating on the aligned frequency difference to determine whether an obstacle is nearby.
13. The sensing method of claim 9 , wherein said operating on the offset frequency difference includes comparing a magnitude of the offset frequency difference to a threshold.
14. The sensing method of claim 9 , wherein said operating includes determining a distance to the obstacle.
15. The sensing method of claim 9 , wherein the series includes acoustic bursts of at least two different burst lengths for obstacle detection at different distances.
16. A sensor that comprises:
an acoustic transducer; and
a controller coupled to the acoustic transducer to generate a series of acoustic bursts having alternating offsets in frequency and to measure a response of the acoustic transducer to each acoustic burst in the series, the controller configured to determine an offset frequency difference between each pair of responses to adjacent acoustic bursts in the series, the offset frequency difference having a magnitude sensitive to any obstacles proximate to the sensor.
17. The sensor of claim 16 , wherein the controller is configured to determine said magnitude.
18. The sensor of claim 17 , wherein the controller is configured to compare the magnitude to a threshold.
19. The sensor of claim 16 , wherein each of the acoustic bursts are up-chirps or down-chirps.
20. The sensor of claim 16 , wherein each of the acoustic bursts are amplitude modulated or phase modulated pulses.
21. The sensor of claim 16 , wherein the controller is configured to determine said offset frequency difference in each of multiple channels.