WO2006131813A1 - Monitoring device for a rotatable shaft - Google Patents

Monitoring device for a rotatable shaft Download PDF

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Publication number
WO2006131813A1
WO2006131813A1 PCT/IB2006/001487 IB2006001487W WO2006131813A1 WO 2006131813 A1 WO2006131813 A1 WO 2006131813A1 IB 2006001487 W IB2006001487 W IB 2006001487W WO 2006131813 A1 WO2006131813 A1 WO 2006131813A1
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WO
WIPO (PCT)
Prior art keywords
monitoring device
signals
shaft
saw resonator
saw
Prior art date
Application number
PCT/IB2006/001487
Other languages
French (fr)
Inventor
Marc Lambrechts
Original Assignee
Melexis Nv
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Melexis Nv filed Critical Melexis Nv
Publication of WO2006131813A1 publication Critical patent/WO2006131813A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L3/00—Measuring torque, work, mechanical power, or mechanical efficiency, in general
    • G01L3/02—Rotary-transmission dynamometers
    • G01L3/04—Rotary-transmission dynamometers wherein the torque-transmitting element comprises a torsionally-flexible shaft
    • G01L3/10—Rotary-transmission dynamometers wherein the torque-transmitting element comprises a torsionally-flexible shaft involving electric or magnetic means for indicating
    • G01L3/106—Rotary-transmission dynamometers wherein the torque-transmitting element comprises a torsionally-flexible shaft involving electric or magnetic means for indicating involving electrostatic means

Definitions

  • the present invention relates to a monitoring device for a rotatable shaft and particularly to such a monitoring device adapted to sense torque applied to a shaft and most particularly to such a monitoring device comprising one or more surface acoustic wave (SAW) resonators.
  • SAW surface acoustic wave
  • SAW resonators may be used in the measurement of many physical or chemical properties including pressure, temperature, tensile strain or compressive strain, one particular application being to measure the torque transmitted by a rotating shaft. This is of particular importance in an internal combustion engine, as in order to manage the operation of an internal combustion engine in an effective and environmentally efficient manner, the engine management unit requires accurate information from sensors mounted on the drive shaft providing information relating to torque transmitted by the drive shaft.
  • two or more SAW resonators are mounted on a shaft such that torque transmitted by the shaft applies a strain to the SAW resonators.
  • the applied strain causes the fundamental frequency of the SAW resonators to vary.
  • the SAW resonator is driven by an input pulse and the resulting oscillations are detected and analysed.
  • the input pulse is generated by stationary pulse generating means and coupled into the SAW via an antenna arrangement.
  • the output is coupled from the SAW resonator to processing means via an antenna arrangement.
  • a pair of SAW resonators are attached to the rotating shaft in an arrangement such that whenever the shaft is rotating, one of the
  • SAW resonators is exposed to strain in a first orientation such as to increase the fundamental frequency and other is exposed to the strain in a second orientation such as to decrease the fundamental frequency.
  • a first orientation such as to increase the fundamental frequency
  • second orientation such as to decrease the fundamental frequency.
  • Such an arrangement produces two sets of relaxing oscillations at different frequencies.
  • the difference between the increased frequency and the decreased frequency is double the difference between any one of the frequencies and the natural unstrained frequency.
  • Such doubling assists in accurately determining a change in frequency and thus a representation of the strain and thus the torque.
  • the energy coupled into the SAW resonators via the antenna arrangement must be of sufficient magnitude and sufficiently accurate in frequency to excite a selected one of the SAW resonators.
  • the relaxation oscillations of the SAW resonators generate small signals which must be detected amongst noise and/or distortion coupled back via the antenna arrangement. Determining the frequency of the SAW oscillations demands an analogue or increasingly a digital processing capability arranged to overcome as far as practical any noise or distortion on the signals received from the antenna arrangement.
  • the antenna coupling between the static and the rotating parts of the antenna may also be affected adversely as the shaft rotates.
  • a monitoring device for a rotatable shaft comprising: SAW resonator means; signal generating means connected to said SAW resonator means for inputting a test signal to said SAW resonator means; signal processing means connected to the output of said SAW resonator means for measuring variation in the resonant frequency of said SAW resonator means, antenna means for transmitting RF signals indicative of the data output by said signal processing means and for receiving RF signals; and energy scavenging means connected to said antenna means and operable to extract energy from said received RF signals wherein all the above components are mounted on said shaft.
  • This provides an improved device for monitoring a shaft as by generating signals for input to the SAW resonators on the shaft and by processing signals output from the SAW resonator means on the shaft, noise in the signals resulting from imperfect coupling is reduced and thus more accurate monitoring of the shaft can be achieved.
  • the SAW resonator means may be a pair of SAW resonators mounted on a shaft substantially perpendicular to each other and substantially at 45 degrees to the axis of rotation of the shaft. This enables each SAW resonator to experience a strain when the shaft transmits torque said strain being indicative of said torque.
  • each of said pair of SAW resonators has a different non-related resonant frequency.
  • said generating means, said signal processing means, said antenna means and said energy scavenging means are mounted on said shaft such that the torque in the shaft does not affect their operation.
  • said generating means may comprise reference SAW resonators for generating a reference signal to be input to said SAW resonator means.
  • said pair of reference SAW resonators are substantially identical to said pair of SAW resonators forming said SAW resonator means and thus have a substantially identical natural resonance frequencies.
  • said reference SAW resonators are maintained at substantially at the same temperature and pressure as the SAW resonator means and exhibit the same temperature and pressure dependencies.
  • said signal generating means is adapted to act as an interface means for said SAW resonator means.
  • said signal processing means is operable to receive signals output by said SAW resonator means and output said signals to said signal processing means.
  • the signal generator is operable as a frequency agile signal generator by switching between the pair of reference SAW resonators.
  • said signal processing means comprises an analogue to digital converter and a digital signal processing means.
  • the signal processing means may be adapted to output signals indicative of the torque applied to the shaft in addition to or in place of signals indicative of the variation in the resonant frequency of the SAW resonator means.
  • the antenna means may be provided with a signal transmitting means operable to receive electrical signals from said signal processing means and to convert said electrical signals into RF signals suitable for transmission by said antenna means.
  • the antenna means may be operable to receive control signals from a remote source and output said control signals to said signal generating means and/or said signal processing means.
  • said antenna means comprises two antenna means, a first antenna means for transmitting RF signals and a second antenna means for receiving RF signals.
  • the monitoring device is adapted to operate with remote (non-shaft mounted) circuitry.
  • the non-shaft mounted circuitry is adapted to receive signals transmitted by said antenna means.
  • the non-shaft mounted circuitry is preferably also operable to transmit RF signals to said antenna means.
  • the transmitted RF signals may be for energy scavenging purposes but may additionally or alternatively comprise control signals for said signal generating means and/or said signal processing means.
  • Said energy scavenging means may additionally be operable to scavenge energy from vibration of the shaft.
  • Figure 1 is a schematic block diagram of a shaft monitoring arrangement according to the current state of the art.
  • Figure 2 is a schematic block diagram of a shaft monitoring arrangement according to the present invention.
  • a known shaft monitoring arrangement comprises a pair of SAW resonators 101 each with different non-related resonant frequencies mounted on a rotating shaft such that their axes are substantially perpendicular to one another and substantially at 45 degrees to the rotation axis of the shaft.
  • This arrangement means that when the shaft is transmitting torque one of the SAW resonators 101 is exposed to strain in a first orientation such as to increase its resonant frequency and other SAW resonator 101 is exposed to the strain in a second orientation such as to decrease its resonant frequency.
  • the torque applied to the shaft can be determined.
  • energy is coupled 103 into the SAW resonators 101 via an antenna arrangement 102, 104 at sufficient magnitude and sufficiently accurate in frequency to excite a selected one of said SAW resonators 101.
  • the relaxation oscillations of the excited SAW resonator 101 generate relatively small output signals.
  • the output signals are coupled via the antenna arrangement 102, 104 to a digital processing means 106 through analogue to digital converter 105.
  • the processing means 105 processes the signal to measure the variation in the resonant frequency of the SAW resonator 101 and hence determine the torque applied to the shaft.
  • the processor must be adapted to overcome as far as practical noise or distortion on the signals as a consequence of transmission via the antenna arrangement 102, 104. This noise/distortion may be exacerbated by the quality of the antenna coupling varying as the shaft rotates.
  • FIG. 2 shows a monitoring device according to the present invention.
  • the device comprises an SAW resonator means being a pair of SAW resonators 201, each with different non-related resonant frequencies, mounted on a rotating shaft such that their axes are substantially perpendicular to one another and substantially at 45 degrees to the rotation axis of the shaft.
  • This arrangement means that when the shaft is transmitting torque one of the SAW resonators 201 is exposed to strain in a first orientation such as to increase its resonant frequency and the other SAW resonator 201 is exposed to the strain in a second orientation such as to decrease its resonant frequency.
  • the torque applied to the shaft can be determined.
  • a frequency agile signal generating means 202 is also mounted on the shaft and is arranged to generate and apply to the SAW resonator means a signal at the resonant frequency of a selected one of the SAW resonators 201 such as to excite it.
  • the signal generating means 202 is also operable to receive the relaxation oscillation signals output by said SAW resonator 201 and to act as an interface means to pass the signals to a signal processing means 203 also mounted on said shaft.
  • the signal processing means 203 is operable to process the signals output by said SAW resonator 201 and to output a signal indicative of the variation in frequency of these signals from the resonant frequency of the SAW resonator 201.
  • the signal processing means 203 may be adapted to further process the signals output by the SAW resonator 201 and thereby output a signal indicative of either the strain applied to said SAW resonator 201 or the torque applied to the shaft.
  • the signal processing means processes signals received from both SAW resonators 201 as their orientations ensure that their respective variations in frequency should be equal and opposite.
  • the output of said signal processing means 203 is converted into an RF signal 205 and transmitted to non-shaft mounted circuitry 207 via antenna arrangement 204, 206, antenna 204 being mounted on said shaft and antenna 206 being non-shaft mounted.
  • the shaft mounted components are powered by an energy scavenging means
  • the energy scavenging means may be any suitable form of energy scavenging means but is preferably operable to extract energy from received RF signals 210.
  • a second antenna arrangement 209, 211 is provided, antenna 209 being mounted on said shaft and antenna 211 being non-shaft mounted.
  • An energy generator 212 is connected to antenna 211 causing antenna 211 to transmit a relatively high energy RF signal 210.
  • the high energy signal 210 is received by antenna 209 and passed to said energy scavenging means 208.
  • the energy scavenging means is then operable to extract energy from said high energy signal 210 and supply electrical energy to power said signal generating means 202, said signal processing means 203 and said antenna means 204.
  • the non-shaft mounted components 206, 207, 211, 212 are preferably mounted in close proximity to said rotating shaft for best results.
  • the non-shaft mounted circuitry 207 is operable to control the energy generator 212 and may also be operable to interface with further circuitry via connection means 213.
  • the monitoring device could be used to monitor the torque applied to a rotating shaft of a vehicle. In such situations, the connection means 213 would enable the monitoring device to interface with a vehicle control unit.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

A monitoring device comprises an SAW resonator means being a pair of SAW resonators (201), each with different non-related resonant frequencies, mounted on a rotating shaft such that their axes are substantially perpendicular to one another and substantially at 45 degrees to the rotation axis of the shaft. By measuring the variation in the resonant frequency of each of the SAW resonators (201) the torque applied to the shaft can be determined. A frequency agile signal generating means (202) is also mounted on the shaft and is arranged to generate and apply to the SAW resonator means a signal at the resonant frequency of a selected one of the SAW resonators (201) such as to excite it. The signal generating means (202) is also operable to receive the relaxation oscillation signals output by said SAW resonator (201) and to act as an interface means to pass the signals to a signal processing means (203) also mounted on said shaft. The signal processing means (203) is operable to process the signals output by said SAW resonator (201) and to output a signal indicative of the variation in frequency of these signals from the resonant frequency of the SAW resonator (201) and/or to further process the signals output by the SAW resonator (201) and thereby output a signal indicative of either the strain applied to said SAW resonator (201) or the torque applied to the shaft. By generating signals for input to the SAW resonators on the shaft and by processing signals output from the SAW resonator means on the shaft, noise in the signals resulting from imperfect coupling is reduced and thus more accurate monitoring of the shaft can be achieved.

Description

Monitoring Device for a Rotatable Shaft
The present invention relates to a monitoring device for a rotatable shaft and particularly to such a monitoring device adapted to sense torque applied to a shaft and most particularly to such a monitoring device comprising one or more surface acoustic wave (SAW) resonators.
SAW resonators may be used in the measurement of many physical or chemical properties including pressure, temperature, tensile strain or compressive strain, one particular application being to measure the torque transmitted by a rotating shaft. This is of particular importance in an internal combustion engine, as in order to manage the operation of an internal combustion engine in an effective and environmentally efficient manner, the engine management unit requires accurate information from sensors mounted on the drive shaft providing information relating to torque transmitted by the drive shaft.
In such applications two or more SAW resonators are mounted on a shaft such that torque transmitted by the shaft applies a strain to the SAW resonators. The applied strain causes the fundamental frequency of the SAW resonators to vary. In order to measure this variation in frequency, the SAW resonator is driven by an input pulse and the resulting oscillations are detected and analysed. In known arrangements, the input pulse is generated by stationary pulse generating means and coupled into the SAW via an antenna arrangement. Similarly, the output is coupled from the SAW resonator to processing means via an antenna arrangement. In a practical arrangement a pair of SAW resonators are attached to the rotating shaft in an arrangement such that whenever the shaft is rotating, one of the
SAW resonators is exposed to strain in a first orientation such as to increase the fundamental frequency and other is exposed to the strain in a second orientation such as to decrease the fundamental frequency. Such an arrangement produces two sets of relaxing oscillations at different frequencies. The difference between the increased frequency and the decreased frequency is double the difference between any one of the frequencies and the natural unstrained frequency. Such doubling assists in accurately determining a change in frequency and thus a representation of the strain and thus the torque.
Whilst such an arrangement has an attractive simplicity it suffers from a number of disadvantages. The energy coupled into the SAW resonators via the antenna arrangement must be of sufficient magnitude and sufficiently accurate in frequency to excite a selected one of the SAW resonators. The relaxation oscillations of the SAW resonators generate small signals which must be detected amongst noise and/or distortion coupled back via the antenna arrangement. Determining the frequency of the SAW oscillations demands an analogue or increasingly a digital processing capability arranged to overcome as far as practical any noise or distortion on the signals received from the antenna arrangement. The antenna coupling between the static and the rotating parts of the antenna may also be affected adversely as the shaft rotates. The need for a frequency agile accurate frequency generator, a low noise transceiver to drive and interface with the antenna, coupling, and a signal processor capable of handling low amplitude signals can add considerably to the cost of a practical sensor. Difficulties in accurately calibrating such an arrangement can also increase the cost of the final sensor.
It is therefore an object of the present invention to provide a torque measuring means which overcomes or alleviates the above problems.
According to a first aspect of the present invention there is provided a monitoring device for a rotatable shaft comprising: SAW resonator means; signal generating means connected to said SAW resonator means for inputting a test signal to said SAW resonator means; signal processing means connected to the output of said SAW resonator means for measuring variation in the resonant frequency of said SAW resonator means, antenna means for transmitting RF signals indicative of the data output by said signal processing means and for receiving RF signals; and energy scavenging means connected to said antenna means and operable to extract energy from said received RF signals wherein all the above components are mounted on said shaft.
This provides an improved device for monitoring a shaft as by generating signals for input to the SAW resonators on the shaft and by processing signals output from the SAW resonator means on the shaft, noise in the signals resulting from imperfect coupling is reduced and thus more accurate monitoring of the shaft can be achieved.
The SAW resonator means may be a pair of SAW resonators mounted on a shaft substantially perpendicular to each other and substantially at 45 degrees to the axis of rotation of the shaft. This enables each SAW resonator to experience a strain when the shaft transmits torque said strain being indicative of said torque. Preferably, each of said pair of SAW resonators has a different non-related resonant frequency.
Preferably said generating means, said signal processing means, said antenna means and said energy scavenging means are mounted on said shaft such that the torque in the shaft does not affect their operation. In such embodiments, said generating means may comprise reference SAW resonators for generating a reference signal to be input to said SAW resonator means. Preferably, said pair of reference SAW resonators are substantially identical to said pair of SAW resonators forming said SAW resonator means and thus have a substantially identical natural resonance frequencies. Preferably said reference SAW resonators are maintained at substantially at the same temperature and pressure as the SAW resonator means and exhibit the same temperature and pressure dependencies.
Preferably, said signal generating means is adapted to act as an interface means for said SAW resonator means. Additionally or alternatively, said signal processing means is operable to receive signals output by said SAW resonator means and output said signals to said signal processing means. The signal generator is operable as a frequency agile signal generator by switching between the pair of reference SAW resonators.
Preferably said signal processing means comprises an analogue to digital converter and a digital signal processing means. The signal processing means may be adapted to output signals indicative of the torque applied to the shaft in addition to or in place of signals indicative of the variation in the resonant frequency of the SAW resonator means.
The antenna means may be provided with a signal transmitting means operable to receive electrical signals from said signal processing means and to convert said electrical signals into RF signals suitable for transmission by said antenna means. The antenna means may be operable to receive control signals from a remote source and output said control signals to said signal generating means and/or said signal processing means. Optionally, said antenna means comprises two antenna means, a first antenna means for transmitting RF signals and a second antenna means for receiving RF signals.
Preferably, the monitoring device is adapted to operate with remote (non-shaft mounted) circuitry. Preferably the non-shaft mounted circuitry is adapted to receive signals transmitted by said antenna means. The non-shaft mounted circuitry is preferably also operable to transmit RF signals to said antenna means. The transmitted RF signals may be for energy scavenging purposes but may additionally or alternatively comprise control signals for said signal generating means and/or said signal processing means.
Said energy scavenging means may additionally be operable to scavenge energy from vibration of the shaft.
The invention will now be described further below, by way of example only, and with reference to the accompanying drawings, in which:-
Figure 1 is a schematic block diagram of a shaft monitoring arrangement according to the current state of the art; and
Figure 2 is a schematic block diagram of a shaft monitoring arrangement according to the present invention.
Referring to Figure 1, a known shaft monitoring arrangement comprises a pair of SAW resonators 101 each with different non-related resonant frequencies mounted on a rotating shaft such that their axes are substantially perpendicular to one another and substantially at 45 degrees to the rotation axis of the shaft. This arrangement means that when the shaft is transmitting torque one of the SAW resonators 101 is exposed to strain in a first orientation such as to increase its resonant frequency and other SAW resonator 101 is exposed to the strain in a second orientation such as to decrease its resonant frequency. By measuring the variation in the resonant frequency of each of the SAW resonators 101 the torque applied to the shaft can be determined. In use, energy is coupled 103 into the SAW resonators 101 via an antenna arrangement 102, 104 at sufficient magnitude and sufficiently accurate in frequency to excite a selected one of said SAW resonators 101. The relaxation oscillations of the excited SAW resonator 101 generate relatively small output signals. The output signals are coupled via the antenna arrangement 102, 104 to a digital processing means 106 through analogue to digital converter 105. The processing means 105 processes the signal to measure the variation in the resonant frequency of the SAW resonator 101 and hence determine the torque applied to the shaft. The processor must be adapted to overcome as far as practical noise or distortion on the signals as a consequence of transmission via the antenna arrangement 102, 104. This noise/distortion may be exacerbated by the quality of the antenna coupling varying as the shaft rotates.
Figure 2 shows a monitoring device according to the present invention. The device comprises an SAW resonator means being a pair of SAW resonators 201, each with different non-related resonant frequencies, mounted on a rotating shaft such that their axes are substantially perpendicular to one another and substantially at 45 degrees to the rotation axis of the shaft. This arrangement means that when the shaft is transmitting torque one of the SAW resonators 201 is exposed to strain in a first orientation such as to increase its resonant frequency and the other SAW resonator 201 is exposed to the strain in a second orientation such as to decrease its resonant frequency. By measuring the variation in the resonant frequency of each of the SAW resonators 201 the torque applied to the shaft can be determined. A frequency agile signal generating means 202 is also mounted on the shaft and is arranged to generate and apply to the SAW resonator means a signal at the resonant frequency of a selected one of the SAW resonators 201 such as to excite it. The signal generating means 202 is also operable to receive the relaxation oscillation signals output by said SAW resonator 201 and to act as an interface means to pass the signals to a signal processing means 203 also mounted on said shaft.
The signal processing means 203 is operable to process the signals output by said SAW resonator 201 and to output a signal indicative of the variation in frequency of these signals from the resonant frequency of the SAW resonator 201. In some embodiments, the signal processing means 203 may be adapted to further process the signals output by the SAW resonator 201 and thereby output a signal indicative of either the strain applied to said SAW resonator 201 or the torque applied to the shaft. For best results, the signal processing means processes signals received from both SAW resonators 201 as their orientations ensure that their respective variations in frequency should be equal and opposite.
The output of said signal processing means 203 is converted into an RF signal 205 and transmitted to non-shaft mounted circuitry 207 via antenna arrangement 204, 206, antenna 204 being mounted on said shaft and antenna 206 being non-shaft mounted.
The shaft mounted components are powered by an energy scavenging means
208 provided on said shaft. The energy scavenging means may be any suitable form of energy scavenging means but is preferably operable to extract energy from received RF signals 210. To this end, a second antenna arrangement 209, 211 is provided, antenna 209 being mounted on said shaft and antenna 211 being non-shaft mounted. An energy generator 212 is connected to antenna 211 causing antenna 211 to transmit a relatively high energy RF signal 210. the high energy signal 210 is received by antenna 209 and passed to said energy scavenging means 208. the energy scavenging means is then operable to extract energy from said high energy signal 210 and supply electrical energy to power said signal generating means 202, said signal processing means 203 and said antenna means 204.
The non-shaft mounted components 206, 207, 211, 212 are preferably mounted in close proximity to said rotating shaft for best results. The non-shaft mounted circuitry 207 is operable to control the energy generator 212 and may also be operable to interface with further circuitry via connection means 213. hi some embodiments, it is possible for the non-shaft mounted circuitry to transmit control signals to said signal generating means 202 or said signal processing means 203 either via antenna arrangement 204, 206 or antenna arrangement 209, 211, as appropriate. Typically, the monitoring device could be used to monitor the torque applied to a rotating shaft of a vehicle. In such situations, the connection means 213 would enable the monitoring device to interface with a vehicle control unit.
It is of course to be understood that the present invention is not to be restricted to the details of the above embodiments which are described by way of example only.

Claims

Claims
1. A monitoring device for a rotatable shaft comprising: SAW resonator means; signal generating means connected to said SAW resonator means for inputting a test signal to said SAW resonator means; signal processing means connected to the output of said SAW resonator means for measuring variation in the resonant frequency of said SAW resonator means, antenna means for transmitting RF signals indicative of the data output by said signal processing means and for receiving RF signals; and energy scavenging means connected to said antenna means and operable to extract energy from said received RF signals wherein all the above components are mounted on said shaft.
2. A monitoring device as claimed in any preceding claim wherein the SAW resonator means is a pair of SAW resonators mounted on a shaft substantially perpendicular to each other and substantially at 45 degrees to the axis of rotation on the shaft.
3. A monitoring device as claimed in claim 2 wherein said pair of SAW resonators each have different non-related resonant frequencies.
4. A monitoring device as claimed in any preceding claim wherein said generating means, said signal processing means, said antenna means and said energy scavenging means are mounted on said shaft such that the torque in the shaft does not affect their operation.
5. A monitoring device as claimed in any preceding claim wherein said signal generating means comprises reference SAW resonators for generating a reference signal to be input to said SAW resonator means.
6. A monitoring device as claimed in claim 5 wherein said pair of reference SAW resonators are substantially identical to said pair of SAW resonators forming said SAW resonator means.
7. A monitoring device as claimed in claim 5 or claim 6 wherein said reference SAW resonators are maintained at substantially at the same temperature and pressure as the SAW resonator means.
8. A monitoring device as claimed in any preceding claim wherein said signal generating means is adapted to act as an interface means for said SAW resonator means.
9. A monitoring device as claimed in any preceding claim wherein said signal processing means is operable to receive signals output by said SAW resonator means and output said signals to said signal processing means.
10. A monitoring device as claimed in any preceding claim when dependent upon any one of claims 5 to 7 wherein the signal generator is operable as a frequency agile signal generator by switching between the pair of reference SAW resonators.
11. A monitoring device as claimed in any preceding claim wherein said signal processing means comprises an analogue to digital converter and a digital signal processing means.
12. A monitoring device as claimed in any preceding claim wherein the signal processing means is adapted to output signals indicative of the torque applied to the shaft.
13. A monitoring device as claimed in any preceding claim wherein the signal processing means is adapted to output signals indicative of the variation in the resonant frequency of the SAW resonator means.
14. A monitoring device as claimed in any preceding claim wherein the antenna means is provided with a signal transmitting means operable to receive electrical signals from said signal processing means and to convert said electrical signals into RF signals suitable for transmission by said antenna means.
15. A monitoring device as claimed in any preceding claim wherein the antenna means is operable to receive control signals from a remote source and output said control signals to said signal generating means and/or said signal processing means.
16. A monitoring device as claimed in any preceding claim wherein said antenna means comprises two antenna means, a first antenna means for transmitting RF signals and a second antenna means for receiving RF signals.
17. A monitoring device as claimed in any preceding claim wherein the monitoring device is adapted to operate with remote (non-shaft mounted) circuitry.
18. A monitoring device as claimed in any preceding claim wherein the non-shaft mounted circuitry is adapted to receive signals transmitted by said antenna means.
19. A monitoring device as claimed in any preceding claim wherein the non-shaft mounted circuitry is operable to transmit RF signals to said antenna means.
20. A monitoring device as claimed in claim 19 wherein the transmitted RF signals are for energy scavenging purposes.
21. A monitoring device as claimed in claim 19 or claim 20 wherein the transmitted RF signals comprise control signals for said signal generating means and/or said signal processing means.
22. A monitoring device as claimed in any preceding claim wherein said energy scavenging means are operable to scavenge energy from vibration of the shaft.
PCT/IB2006/001487 2005-06-06 2006-06-06 Monitoring device for a rotatable shaft WO2006131813A1 (en)

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GB0511458A GB0511458D0 (en) 2005-06-06 2005-06-06 Monitoring device for a rotatable shaft

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US8281856B2 (en) 2006-04-27 2012-10-09 Weatherford/Lamb, Inc. Torque sub for use with top drive
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EP2320577A3 (en) * 2009-11-05 2012-06-06 Maeda Metal Industries, Ltd. Antenna switching method of wireless communication system
TWI481214B (en) * 2009-11-05 2015-04-11 Maeda Metal Ind Antenna switching method of wireless communication system

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