Detection of contamination status for refrigerator ultrasonic sensor assembly

1. A refrigerator, comprising:

a sensor assembly comprising:

a first ultrasonic sensor configured to transmit an ultrasonic signal; and

a second ultrasonic sensor configured to receive the ultrasonic signal;

wherein the refrigerator is configured to perform operations comprising:

operating the sensor assembly to send and receive the ultrasonic signal;

comparing an amount of received crosstalk to a threshold value; and

determining the contamination status of the sensor assembly based on the comparison of the amount of received crosstalk to the threshold value;

wherein determining a contamination status of the sensor assembly based on the comparison comprises detecting that the sensor assembly is contaminated when the amount of received crosstalk is greater than the threshold value.

2. The refrigerator of claim 1 , wherein the refrigerator is configured to perform further operations comprising performing a calibration routine upon a system initialization to obtain the threshold value.

3. The refrigerator of claim 1 , wherein the refrigerator is configured to perform further operations comprising:

determining the amount of received crosstalk, wherein determining the amount of received crosstalk comprises determining a first amplitude of the received ultrasonic signal at a first time, the first time being before a predetermined amount has elapsed since a time of transmission of the ultrasonic signal from the first ultrasonic sensor.

4. The refrigerator of claim 3 , wherein the refrigerator is configured to perform further operations comprising determining the threshold value by performing a calibration routine upon a system initialization.

5. The refrigerator of claim 1 , wherein the refrigerator is configured to perform further operations comprising providing a user alert when it is detected that the sensor assembly is contaminated.

6. The refrigerator of claim 1 , wherein the refrigerator is configured to perform further operations comprising:

analyzing a portion of the ultrasonic signal received after a deadband delay to detect the presence of an object within a proximity of the sensor assembly, the deadband delay comprising an amount of time after a time of transmission of the ultrasonic signal from the first ultrasonic sensor; and

increasing the deadband delay when it is detected that the sensor assembly is contaminated.

7. The refrigerator of claim 1 , wherein the first ultrasonic sensor comprises an ultrasonic transducer and the second ultrasonic sensor comprises an ultrasonic detector.

8. A method for determining a contamination status of an ultrasonic sensor assembly included in a refrigerator appliance, the method comprising:

operating the ultrasonic sensor assembly to send and receive one or more ultrasonic signals;

comparing an amount of received crosstalk to a threshold value; and

determining the contamination status of the ultrasonic sensor assembly based on the comparison of the amount of received crosstalk to the threshold value;

wherein determining the contamination status of the ultrasonic sensor assembly based on the comparison comprises detecting that the ultrasonic sensor assembly is contaminated when the amount of received crosstalk is greater than the threshold value.

9. The method of claim 8 , wherein:

the ultrasonic sensor assembly comprises:

a chassis;

an ultrasonic transducer; and

an ultrasonic detector; and

the received crosstalk comprises vibrations transmitted from the ultrasonic transducer to the ultrasonic detector via the chassis.

10. The method of claim 8 , wherein:

the ultrasonic sensor assembly comprises:

an ultrasonic transducer; and

an ultrasonic detector; and

the amount of received crosstalk comprises a first voltage generated by the ultrasonic detector at a first time following transmission of the one or more ultrasonic signals by the ultrasonic transducer.

11. The method of claim 8 , wherein:

operating the ultrasonic sensor assembly to send and receive the one or more ultrasonic signals comprises:

respectively transmitting a plurality of ultrasonic signals, each ultrasonic signal having a pulse amplitude; and

respectively receiving the plurality of ultrasonic signals, the plurality of received ultrasonic signals respectively exhibiting a plurality of received crosstalk amplitudes; and

comparing the amount of received crosstalk to the threshold value comprises respectively comparing the plurality of received crosstalk amplitudes to a plurality of threshold values.

12. The method of claim 11 , wherein determining the contamination status of the ultrasonic sensor assembly based on the comparison comprises detecting that the ultrasonic sensor assembly is contaminated when a majority of the plurality of received crosstalk amplitudes are greater than their respective threshold values.

13. The method of claim 11 , wherein:

respectively comparing the plurality of received crosstalk amplitudes to a plurality of threshold values comprises respectively determining a plurality of variances for the plurality of received crosstalk amplitudes, each variance for each received crosstalk amplitude describing a difference between such received crosstalk amplitude and the respective threshold value to which it was compared; and

determining the contamination status of the ultrasonic sensor assembly based on the comparison comprises:

summing the plurality of variances to obtain a global variance; and

detecting that the ultrasonic sensor assembly is contaminated when the global variance is greater than a global threshold value.

14. The method of claim 8 , further comprising increasing a deadband delay value when the ultrasonic sensor assembly is determined to be contaminated, the deadband delay value describing an interval of time after transmission of each of the one or more ultrasonic signals in which the corresponding received ultrasonic signal is not analyzed for object detection.