Predictive maintenance of exercise machines with time-of-flight sensors

1. A method of determining a need for maintenance of an associated exercise machine including a time-of-flight sensor and a reflective element, the method comprising:

obtaining a measurement signal from the time-of-flight sensor at a predefined operating condition of the exercise machine;

determining, based on the measurement signal, a measured distance between the time-of-flight sensor and the reflective element; and

determining the need for maintenance based on detecting a decrease in the measured distance over time.

2. The method of claim 1 , wherein the determining the need for maintenance comprises checking the measured distance with respect to a reference distance.

3. The method of claim 2 , further comprising:

receiving a further measurement signal generated by the time-of-flight sensor at a reference time when the exercise machine is in the predefined operating condition; and

determining the reference distance as a function of the further measurement signal generated by the time-of-flight sensor at the reference time.

4. The method of claim 2 , wherein said obtaining comprises obtaining the measurement signal for a first range setting of the time-of-flight sensor, the method further comprising:

receiving a further measurement signal from the time-of-flight sensor for a second range setting of the time-of-flight sensor at the predefined operating condition of the exercise machine, the second range setting being different from the first range setting; and

determining the reference distance based on the further measurement signal received from the time-of-flight sensor for the second range setting.

5. The method of claim 2 , wherein the reference distance is a predefined distance associated with the predefined operating condition of the exercise machine.

6. The method of claim 2 , wherein the need for maintenance is detected when a difference between the measured distance and the reference distance exceeds a threshold.

7. The method of claim 1 , wherein at least one of the time-of-flight sensor and the reflective element is moveable during use of the exercise machine, and wherein the predefined operating condition comprises the time-of-flight sensor and the reflective element being immobile.

8. The method of claim 1 , wherein the predefined operating condition corresponds to a maximum or minimum distance between the time-of-flight sensor and the reflective element.

9. The method of claim 1 , further comprising: performing said obtaining responsive to a signal indicative of the predefined operating condition of the exercise machine.

10. The method of claim 1 , wherein the maintenance comprises cleaning a signal transmissive surface of the time-of-flight sensor.

11. The method of claim 1 , wherein the time-of-flight sensor is configured to generate the measurement signal as a function of a phase difference between outgoing and incoming signals.

12. An apparatus configured to determine a need for maintenance of an associated exercise machine including a time-of-flight sensor and a reflective element, the apparatus comprising:

an input for receiving a measurement signal from the time-of-flight sensor; and

logic configured to:

obtain the measurement signal via the input, the measurement signal being generated by the time-of-flight sensor at a predefined operating condition of the exercise machine;

determine, based on the measurement signal, a measured distance between the time-of-flight sensor and the reflective element; and

determine the need for maintenance based on detecting a decrease in the measured distance over time.

13. A method of determining a need for maintenance of an associated exercise machine including a time-of-flight sensor and a reflective element, the method comprising:

obtaining, by the time-of-flight sensor during a measurement period, a plurality of measurement values indicative of measured distance between the time-of-flight sensor and the reflective element, each of the measurement values corresponding to a respective signal pulse emitted by the time-of-flight sensor;

computing one or more evaluation parameters as a function of the plurality of measurement values; and

determining the need for maintenance based on detecting a decrease in the measured distance over time.

14. The method of claim 13 , wherein the one or more evaluation parameters represent a distribution of the plurality of measurement values.

15. The method of claim 14 , wherein the computing comprises determining a count of measurement values that are indicative of distances that fall within a distance interval which is a subset of a total measurement range of the time-of-flight sensor.

16. The method of claim 15 , wherein the distance interval is located at a lower end of the total measurement range of the time-of-flight sensor.

17. The method of claim 15 , wherein the computing further comprises determining a peak value in a histogram of the plurality of measurement values.

18. The method of claim 17 , wherein the determining the need for maintenance further comprises evaluating the count in relation to the peak value.

19. The method of claim 14 , wherein the determining the need for maintenance further comprises evaluating the distribution in relation to a reference distribution.

20. The method of claim 13 , wherein the obtaining is performed when an actual distance between the time-of-flight sensor and the reflective element is known to be outside of a distance interval.