Frequency hopping for smart air springs
The subject invention relates to an air spring height sensor comprising a transmitter unit ( 102 ) for transmitting a height measuring signal, a receiver unit ( 101 ) for sensing a height signal, a carrier frequency switching unit ( 103 ), and an evaluation unit ( 200 ). The receiver unit and the transmitter unit are adapted for being mounted to opposing mounting elements ( 10, 20 ) of an air spring ( 1 ). The transmitter unit is switchable between different carrier frequencies ( 121, 122 ) of a height measuring signal. The evaluation unit comprises a frequency filter ( 213 ) being switchable between different carrier frequencies, wherein the carrier frequency switching unit is adapted for switching the carrier frequency of the frequency filter at a predetermined first point of time and the corresponding carrier frequency of the transmitter unit at a predetermined second point of time, wherein the first point of time is prior to the second point of time.
1. An air spring height sensor comprising:
a transmitter unit for transmitting a height measuring signal,
a receiver unit for sensing a height signal,
a carrier frequency switching unit, and
an evaluation unit,
wherein the transmitter unit is switchable between a first carrier frequency and a second carrier frequency of the height measuring signal,
wherein the evaluation unit comprises a frequency filter being switchable between the first carrier frequency and the second carrier frequency,
wherein the carrier frequency switching unit is adapted for switching the frequency filter at the receiver unit from the first carrier frequency to the second carrier frequency at a predetermined first point of time (t 1 ) and for switching a carrier frequency of the transmitter unit from the first carrier frequency to the second carrier frequency at a predetermined second point of time (t 2 ),
wherein the first point of time is prior to the second point of time,
wherein the evaluation unit is adapted for detecting, after the first point of time but prior to the second point of time, whether the first carrier frequency or the second carrier frequency is sufficiently free of interferences for subsequent evaluation of the height measuring signal, and
wherein the first carrier frequency or the second carrier frequency is sufficiently free of interferences when a signal to noise ratio of the sensed height signal meets or exceeds a threshold.
2. The air spring height sensor according to claim 1 , wherein the receiver unit and the transmitter unit are adapted for being mounted to opposing mounting elements of an air spring.
3. The air spring height sensor according to claim 1 , wherein the evaluation unit is adapted for detecting after the first point of time and before the second point of time whether the second carrier frequency is sufficiently free of interferences for subsequent evaluation of the height measuring signal.
4. The air spring height sensor according to claim 1 , wherein the evaluation unit is adapted for detecting after the first point of time and before the second point of time whether the first carrier frequency is sufficiently free of interferences for subsequent evaluation of the height measuring signal.
5. The air spring height sensor according to claim 1 , wherein the carrier frequency switching unit is adapted for alternately switching the carrier frequency of the frequency filter and the transmitter unit between the first carrier frequency and the second carrier frequency.
6. The air spring height sensor according to claim 1 , wherein the carrier frequency switching unit is adapted for periodically switching the frequency filter from the first carrier frequency to the second carrier frequency of the receiver unit at a periodic predetermined first point of time (t 1 ) and for switching the carrier frequency of the transmitter unit from the first carrier frequency to the second carrier frequency at a respective predetermined second point of time (t 2 ).
7. The air spring height sensor according to claim 1 , wherein the air spring height sensor is adapted for interrupting a transmission of the transmitter unit at least partially between the first point of time and the second point of time.
8. The air spring height sensor according to claim 1 , wherein the air spring height sensor is adapted for interrupting a transmission of the transmitter unit between the first point of time and the second point of time.
9. The air spring height sensor according to claim 1 , wherein the carrier frequency is between 1 kHz and 1 MHz, in particular the carrier frequency is between 10 kHz and 100 kHz.
10. The air spring height sensor according to claim 5 , wherein an alternating rate from the first carrier frequency to the second carrier frequency or from the second carrier frequency to the first carrier frequency between 1 Hz and 1 kHz.
11. The air spring height sensor according to claim 10 , wherein the alternating rate is within the range of 10 Hz to 100 Hz.
12. The air spring height sensor according to claim 1 , wherein a ratio of a duration between the first point of time and the second point of time and a duration where the carrier frequency of the transmitter unit corresponds to the carrier frequency of the frequency filter is between 0.2 and 5.
13. The air spring height sensor according to claim 1 , wherein a ratio of a duration between the first point of time and the second point of time and a duration where the carrier frequency of the transmitter unit corresponds to the carrier frequency of the frequency filter is between 0.5 and 2.
14. The air spring height sensor according to claim 1 , wherein a ratio of a duration between the first point of time and the second point of time and a duration where the carrier frequency of the transmitter unit corresponds to the carrier frequency of the frequency filter is between 0.8 and 1.2.
15. An air spring comprising:
a first mounting element being adapted for being mounted to a first vehicle portion;
a second mounting element being adapted for being mounted to a second vehicle portion being movable with respect to the first vehicle portion;
an air volume limited by a resilient belly having a first edge and a second edge, which belly with the first edge is sealed to the first mounting element and with the second edge is sealed to the second mounting edge;
the air spring height sensor of claim 1 ,
wherein the transmitter unit is mounted to the first mounting element, and wherein the receiver unit is mounted to the second mounting element as to sense the height signal with respect to the first mounting element.
16. An air spring height measuring method, the method comprising:
switching at a predetermined first point of time a carrier frequency of a frequency filter of an evaluation unit from a first carrier frequency to a second carrier frequency, the second carrier frequency being different from the first carrier frequency;
evaluating a sensed height signal of a receiver unit being mounted to a first mounting element of an air spring from the first carrier frequency to the second carrier frequency or from the second carrier frequency to the first carrier frequency;
switching at a predetermined second point of time the first carrier frequency of a transmitter unit for transmitting a height measuring signal to the second carrier frequency of the frequency filter,
wherein the transmitter unit is mounted to a second mounting element of the air spring;
detecting, by the evaluation unit after the first point of time but prior to the second point of time, whether the first carrier frequency or the second carrier frequency is sufficiently free of interferences for subsequent evaluation of the sensed height signal, and
wherein the first carrier frequency or the second carrier frequency is sufficiently free of interferences when a signal to noise ratio of the sensed height signal meets or exceeds a threshold.
17. The air spring height measuring method according to claim 16 , wherein switching the carrier frequency of the frequency filter comprises periodically switching the carrier frequency at a periodic predetermined first point of time and switching the carrier frequency of the transmitting unit comprises periodically switching the carrier frequency at a respective periodic predetermined second point of time.
18. The air spring height measuring method according to claim 16 , further comprising interrupting the transmission of the transmitter unit at least partially between the first point of time and the second point of time.
19. The air spring height measuring method according to claim 17 , further comprising interrupting the transmission of the transmitter unit at least partially between the first point of time and the second point of time.
20. A method comprising:
switching, at a first point of time, a carrier frequency of a frequency filter of an evaluation unit from a first carrier frequency to a second carrier frequency different from the first carrier frequency;
detecting a sensed height signal of a receiver unit of an air spring switched from the first carrier frequency to the second carrier frequency or from the second carrier frequency to the first carrier frequency;
detecting, by an evaluation unit after a first point of time but prior to a second predetermined point of time, whether the first carrier frequency or the second carrier frequency is sufficiently free of interferences for subsequent evaluation of the sensed height signal; and
switching at the predetermined second point of time the carrier frequency of a transmitter unit for transmitting a height measuring signal to a corresponding carrier frequency of the frequency filter, wherein the transmitter unit is mounted to a second mounting element of the air spring,
wherein the first carrier frequency or the second carrier frequency is sufficiently free of interferences when a signal to noise ratio of the sensed height signal meets or exceeds a threshold.