Movement and presence detection systems and methods using sonar

1. A method for detecting presence of a person, comprising:

emitting, by a speaker of a device, a plurality of ultrasonic ping signals;

receiving, by a microphone of the device, a plurality of reflected ultrasonic ping signals; and

processing the received reflected signals to determine a presence of a person within a predetermined distance of the device, wherein the processing comprises:

determining changes in the reflected signals relative to the emitted signals by:

generating an impulse response by cross-correlating the received signals and the emitted signals;

averaging the cross-correlated impulse response over a set time period; and

generating a detection signal by subtracting the averaged cross-correlated impulse response from an instantaneous impulse response;

applying a time gating function to select a portion of the detection signal corresponding to the reflected signal from the predetermined distance from the device; and

applying gain compensation to the time gated detection signal to compensate signal falloff.

2. The method of claim 1 , further comprising providing an indication that a person is present within the predetermined distance of the device in response to the gain compensated signal being within a set threshold.

3. The method of claim 1 , wherein the cross-correlating the received signals and the emitted signals comprises matched filtering.

4. The method of claim 1 , wherein the impulse response comprises signals reflected from the person and objects in the environment.

5. The method of claim 1 , wherein the averaging the cross-correlated impulse response comprises exponential decay averaging.

6. The method of claim 1 , wherein the plurality of ultrasonic ping signals is a sine sweep signal comprising about 5 to about 20 pings per second, has a frequency of about 15 to about 24 kHz, and each ping is about 10 to about 15 milliseconds.

7. The method of claim 6 , further comprising filtering the sine sweep signal through a bandpass chebyshev filter.

8. The method of claim 1 , further comprising:

receiving, by the microphone, environmental sounds; and

discriminating the reflected ultrasonic ping signal from the environmental sounds.

9. The method of claim 1 , wherein the set time period of averaging the cross-correlated impulse response corresponds to a latency of the emitted signal to return as the reflected signal.

10. The method of claim 9 , further comprising determining the latency by an initialization process, wherein the initialization process comprises:

emitting an ultrasonic test signal;

receiving the ultrasonic test signal reflected from objects in an environment of the device; and

computing the reflected ultrasonic test signal to determine the latency.

11. A system, comprising:

a non-transitory memory; and

one or more hardware processors coupled to the non-transitory memory and configured to read instructions from the non-transitory memory to cause the system to perform operations comprising:

emitting, by a speaker of a device, a plurality of ultrasonic ping signals;

receiving, by a microphone of the device, a plurality of reflected ultrasonic ping signals; and

processing the received reflected signals to determine a presence of a person within a predetermined distance of the device, wherein the processing comprises:

determining changes in the reflected signals relative to the emitted signals by:

generating an impulse response by cross-correlating the received signals and the emitted signals;

averaging the cross-correlated impulse response over a set time period; and

generating a detection signal by subtracting the averaged cross-correlated impulse response from an instantaneous impulse response;

applying a time gating function to select a portion of the detection signal corresponding to the reflected signal from the predetermined distance from the device; and

applying gain compensation to the time gated detection signal to compensate signal falloff.

12. The system of claim 11 , wherein the processing the received reflected ultrasonic ping signals further comprises providing an indication that a person is present within the predetermined distance of the device in response to the gain compensated signal being with a set threshold.

13. The system of claim 11 , wherein the cross-correlating the received signals and the emitted signals comprises matched filtering.

14. The system of claim 11 , wherein the impulse response comprises signals reflected from the person and objects in the environment.

15. The system of claim 11 , wherein the averaging the cross-correlated impulse response comprises exponential decay averaging.

16. The system of claim 11 , wherein the plurality of ultrasonic ping signals is a sine sweep signal comprising about 5 to about 20 pings per second, has a frequency of about 15 to about 24 kHz, and each ping is about 10 to about 15 milliseconds.

17. The system of claim 16 , wherein the operations further comprise filtering the sine sweep signal through a bandpass chebyshev filter.

18. The system of claim 11 , wherein the operations further comprise:

receiving, by the microphone, environmental sounds; and

discriminating the reflected ultrasonic ping signal from the environmental sounds.

19. The system of claim 11 , wherein the set time period of averaging the cross-correlated impulse response corresponds to a latency of the emitted signal to return as the reflected signal.

20. The system of claim 19 , wherein the operations further comprises determining the latency by an initialization process, wherein the initialization process comprises:

emitting an ultrasonic test signal;

receiving the ultrasonic test signal reflected from objects in an environment of the device; and

computing the reflected ultrasonic test signal to determine the latency.