Torque monitoring system for a rotatable shaft

A torque monitoring system includes a rotatable measurement interface and a stationary data receiver. The measurement interface is configured to be attached to a rotatable shaft. The measurement interface includes a strain gauge, a processor, and a near field communication (NFC) transceiver coil. The stationary data receiver is stationary with respect to the rotating shaft. The stationary data receiver includes a processor and an NFC transceiver coil. The rotatable measurement interface receives operating power via its NFC transceiver coil that is derived from a radio signal wirelessly transmitted by the NFC transceiver coil in the stationary data receiver. The processor in the rotatable measurement interface is configured to receive strain gauge signals from the strain gauge indicative of torque on the rotatable shaft and wirelessly transmit digital data indicative of the strain gauge signals through the NFC transceiver coils to the processor in the stationary data receiver.

BACKGROUND

Many types of systems include a rotating shaft. For example, electric motors and internal combustion engines drive shafts and/or transmissions of vehicles, crafts, manufacturing systems, and other devices. While a rotating shaft may be exposed to normally occurring resistive loads, cyclic and intermittent forces may be fed back into the shafts and transmissions from other components and loads. Combined with the normally occurring forces, such additional forces may reduce the service life of the rotating shaft. Further, such abnormal forces and vibrations may result in a failure of the shaft that may damage other components as well.

SUMMARY

In one embodiment, a torque monitoring system includes a rotatable measurement interface and a stationary data receiver. The measurement interface is configured to be attached to a rotatable shaft. The measurement interface includes a strain gauge, a processor, and a near field communication (NFC) transceiver coil. The stationary data receiver is stationary with respect to the rotating shaft. The stationary data receiver includes a processor and an NFC transceiver coil. The rotatable measurement interface receives operating power via its NFC transceiver coil that is derived from a radio signal wirelessly transmitted by the NFC transceiver coil in the stationary data receiver. The processor in the rotatable measurement interface is configured to receive strain gauge signals from the strain gauge indicative of torque on the rotatable shaft and wirelessly transmit digital data indicative of the strain gauge signals through the NFC transceiver coils to the processor in the stationary data receiver.

In another embodiment, a torque monitoring and feedback system includes a rotatable drive shaft, a rotatable measurement interface, a stationary data receiver, and an electronics control unit (ECU). The rotatable measurement interface is attached to the rotatable drive shaft so as to rotate in unison with rotatable drive shaft. The measurement interface including a strain gauge, a processor, and a transceiver coil. The stationary data receiver is contained in a housing and stationary with respect to the rotating drive shaft. The stationary data receiver includes a processor and a transceiver coil. The ECU is configured to communicate with the stationary data receiver. The rotatable measurement interface receives operating power via its transceiver coil that is derived from a radio signal wirelessly transmitted by the transceiver coil in the stationary data receiver. The processor in the rotatable measurement interface is configured to receive strain gauge measurement data from the strain gauge and wirelessly transmit data indicative of the measurement data through the transceiver coils to the processor in the stationary data receiver.

In yet another embodiment, a system includes a main drive shaft, a parallel drive shaft, and a transmission mechanically linking the main drive shaft to the parallel drive shaft. A first rotatable measurement interface is attached to the main drive shaft so as to rotate in unison with main drive shaft. The first measurement interface includes a strain gauge and a transceiver coil. A first stationary data receiver is contained in a housing and stationary with respect to the main drive shaft. The first stationary data receiver includes a transceiver coil for wireless communication with the transceiver coil of the first rotatable measurement device. A second rotatable measurement interface is attached to the parallel drive shaft so as to rotate in unison with parallel drive shaft. The second measurement interface includes a strain gauge and a transceiver coil. A second stationary data receiver is contained in a housing and stationary with respect to the parallel drive shaft. The second stationary data receiver includes a transceiver coil for wireless communication with the transceiver coil of the second rotatable measurement device. The first and second rotatable measurement interfaces receive power from and provide data communications to their respective first and second stationary data receivers via the corresponding transceiver coils.

DETAILED DESCRIPTION

This disclosure relates to systems and methods for monitoring the torque of one or more rotatable shafts for use in any of a variety of systems. Examples of such systems include manufacturing systems and drive systems. One non-limiting example of a drive system is a drive rotor of a helicopter. In some systems, cyclic and/or intermittent forces and/or vibrations may feed back to the shaft and/or transmission from other components so that the shaft and/or transmission not only experience the normally anticipated forces of driving resistive rotation loads but also cyclic and/or intermittent variations in rotational loading. In some systems, as components such as bearings wear or otherwise degrade, the forces required to rotate the shaft may gradually increase. The systems and methods disclosed herein monitor the effect of the forces applied to the shafts and the transmissions in a manner configured to provide notice and/or information regarding changes in cyclic, transient, or gradually changing of torque loads so that the monitoring and collection of data regarding loading of a shaft and/or transmission may be utilized to mitigate cyclic fatigue failures, resonant loading failures, inefficient operation, or other types of undesirable outcome related to an undesirable torque loading of a shaft. Accordingly, a torque monitoring and feedback system is disclosed below that may be operated according to a variety of methods and embodiments described herein.

FIG. 1illustrates a torque monitoring and feedback system100in accordance with various embodiments. In the non-limiting example shown, the torque monitoring and feedback system100includes a rotatable measurement interface102attached to a rotatable shaft90. The rotatable shaft may be any type of rotating shaft, such as a drive shaft usable in, for example, a vehicle or a manufacturing system. The rotatable measurement interface102is rigidly attached to the shaft90so that the rotatable measurement interface rotates with the shaft. The rotatable measurement interface90may include a variety of components such as a strain gauge, a processor, and a transceiver coil. In some embodiments, the components of the rotatable measurement interface102may be distributed radially about shaft90to minimize unbalancing forces that may be generated by rotation of the rotatable measurement interface102along with the shaft.

The system100also includes a stationary data transceiver104, which may surround a circumference of shaft90but is not rigidly attached to the shaft. Thus, as the shaft90rotates, the stationary data transceiver does not rotate. The stationary data transceiver104may be contained in a housing that is separate and apart from the rotatable shaft90. The stationary data transceiver104may include various components such as a processor and a transceiver coil.

The stationary data transceiver104remains in a fixed position longitudinally relative to the rotatable measurement interface102so that the spacing L1between the stationary data transceiver and the rotatable measurement interface generally is constant despite the rotation of the shaft and rotatable measurement interface relative to the stationary data transceiver.

The transceivers coils of the stationary data transceiver104and the rotatable measurement interface102are used to transfer power from the stationary data transceiver to the rotatable measurement interface to provided operating power for the components of the rotatable measurement interface. The transceiver coils are also used as a wireless data communication link between rotatable measurement interface and stationary data transceiver. For example, the rotatable measurement interface102may transmit digital data encoding information of the strain gauge to the stationary data receiver104.

An electronics control unit (ECU)110also is shown in communication with the stationary data receiver104. The stationary data receiver104may forward to the ECU110data, alerts, etc. related to the operation of and events detected by the stationary data receiver and/or the rotatable measurement interface102. Examples of such detected events include one or more of a vibration event, a tension event, a compression event, a bending event, a resonance event, and a torque event. The rotatable measurement interface102may include multiple strain gauges and other types of sensors to be able to detect such events. These various events may be a vibration, tension, compression, bending, resonance, or torque level detected in excess of a corresponding threshold. For example, a strain gauge may output a voltage proportional the strain detected by the gauge. The voltage can then be translated by processor126,136to a strain measurement. This measurement can then be compared against a user-specified threshold strain level. As a result of the wireless communication between the rotatable measurement interface102and stationary data receiver104which in turn is coupled to the ECU110, any of these events may be determined to exist by the processor126in the rotatable measurement interface102, the processor136in the stationary data receiver104, and/or the ECU110. The threshold value may be determined by the system designer and can be loaded into memory in the stationary data receiver104and/or rotatable measurement interface102(e.g., loaded into storage integrated in the processors126,136). Strain on a shaft can be caused by any of the events (vibration, tension, etc.) described above. Depending on gauge configuration (e.g., how the gauge is mounted to the shaft90), different events can be measured. The voltage output from the gauge will be proportional to the amplitude of the event and this output voltage will be translated into a strain measurement.

For example, the processor126in the rotatable measurement interface102may process the strain gauge signal and determine that a mechanical event has occurred, or is occurring. The processor126in the rotatable measurement interface102can then transmit a signal through the NFC interface to the stationary data receiver104that a mechanical event has occurred or is occurring. Through the ECU110, the stationary data receiver104can then cause the drive unit115to adjust the torque and/or speed of a motor driving the shaft90(in the example in which the shaft is actively driven). Alternatively, the stationary data receiver104sends a signal to other system logic that a mechanical event has occurred and such system logic will take appropriate action commensurate with the specifics of the particular system. In other embodiments, the rotatable measurement interface102sends digital data indicative of the strain gauge signal across the NFC interface to the stationary data receiver104, and the stationary data receiver104processes such data to determine that a mechanical event has occurred or is occurring. Further still, the digital data indicative of the strain gauge signal may be transmitted from the rotatable measurement interface to the stationary data receiver and on to the ECU110(or other system logic) for the ECU110to process and determine whether a mechanical event has occurred or is occurring.

A drive unit115is provided to actively turn the shaft90in embodiments in which the shaft90is desired to be actively rotated. In other embodiments, the shaft90is not actively rotated and thus the drive unit115may not be included in such embodiments. For the example of an actively driven shaft90, upon detection of any of the events listed above, the ECU110may cause the drive unit115to control the speed of rotation of the shaft90and/or the torque on the shaft. For example, the shaft90can be stopped completely upon detection of an excessive vibration, tension, etc. on the shaft, rather then risk damage to the shaft90and other components in the vicinity of the shaft. The latency between receiving a signal from a strain gauge, to detecting a problem with the shaft, to adjusting the speed and/or torque of the shaft is relatively small with this system, particular because of the speed of processors126and136coupled with the NFC interface. In some implementations, the latency is in the range of 1-20 ms. As such, the latency is small enough that the operation of the shaft can be adjusted in real time, or near real-time. As such, the system can react quickly enough to provide, for example, minute adjustments in the timing feed and part synchronization to avoid the costly jams and misfeeds.

FIG. 2shows a block diagram of the rotatable measurement interface102in accordance with various embodiments. As shown in the example ofFIG. 2, the rotatable measurement interface102includes a strain gauge, am amplifier (AMP)122, an analog-to-digital converter (ADC)124, a processor126, a rectifier128, and a transceiver coil130. The strain gauge120may be a torsional strain gauge. More than one strain gauge may be included in the rotatable measurement interface102and a separate amplifier122may be provided for each strain gauge to increase the magnitude of the signal from the corresponding strain gauge. The ADC124converts the analog signal from the strain gauge120to a digital equivalent value and provides the digital equivalent value to the processor126.

The transceiver coil130in the rotatable measurement interface102receives radiated energy from a corresponding transceiver coil in the stationary data receiver102. The rectifier128rectifies the alternating current (AC)-received energy and provides rectified power to those components in the rotatable measurement interface102that are to be actively powered, such as the processor126. The ADC124and amplifier also may receive rectified power for their operation as well as the strain gauge120itself. The rectifier may be a half or full bridge rectifier such as a diode-based rectifier. A voltage regulator may be included if desired to regulate the power to the various components of the rotatable measurement interface102.

The processor126also may transmit data back to the stationary data receiver104through the transceiver coil130. Thus, the transceiver coil130receives radiation from the stationary data receiver104for powering the rotatable measurement interface102, and transmits data in the opposite direction from the rotatable measurement interface102to the stationary data receiver104.

FIG. 3shows an example of a block diagram of the stationary data receiver104. As shown, the stationary data receiver104includes a processor136coupled to a transceiver coil140. The processor136also includes a data interface for the ECU110. The stationary data receiver104may be battery-operated, may have a dedicated power connection, or may be powered through the connection with the ECU110.

In one embodiment, the stationary data receiver104and the rotatable measurement interface102wirelessly interface with each other in accordance with Near Field Communication (NFC). As such, the transceiver coils130and140are NFC transceiver coils. Other wireless interface standards can be used as well.

FIG. 4illustrates an example of the torque monitoring and feedback system100. Referring toFIG. 4, the data receiver104is shown on the left and the rotatable measurement interface102is shown on the right. The data receiver104includes a processor136coupled to the transceiver coil140. Additional components may be provided as well.

The rotatable measurement interface102includes the transceiver coil130as noted above, as well as the processor126and rectifier128. The ADC124(not specifically shown inFIG. 4) may be included as part of the processor126or may be a separate component. A capacitor C1is shown connected in parallel across the transceiver coil130. The combination of the transceiver coil130and capacitor C1forms a tank circuit which functions an electrical resonator storing energy received from the transceiver coil140at the tank circuit's resonant frequency. Power transfer from stationary data receiver104to rotatable measurement interface102by having both transceiver coils130and136tuned to resonate at the same frequency.

Communications from the remotely powered rotatable measurement interface102may be accomplished by taking advantage of changes in impedance with resonant frequency. Shifting the series resonance of transceiver coil130toward series resonance or toward parallel resonance provides a substantial change in power drawn by the transceiver coil130, which in turn changes the loading on the transceiver coil136in the stationary data receiver104. When tuned to series resonance, transceiver coil130is in an absorptive state where it places a heavy load on transceiver coil140, which reduces the Q of its resonance and reduces the voltage across transceiver coil140. When tuned to parallel resonance, transceiver coil130is in a reflective state where it reduces the load on transceiver coil140in the stationary data receiver104, raising the Q of its resonance, and increase the voltage across the transceiver coil140. Thus, by changing the reactance (and consequently the resonant frequency) of transceiver coil130in the rotatable measurement interface102relative to transceiver coil136in the stationary data receiver104, the voltage across the stationary data receiver's transceiver coil140can be made to vary so as to encode digital data transmitted by the processor126of the rotatable measurement interface102.

The resonant frequency of the transceiver coil130in the rotatable measurement interface102can be tuned by a switched reactive element. In the embodiment shown inFIG. 4, capacitor C2is an example of such a switched reactive element. Capacitor C2is switched in and out of the tank circuit by switch SW2, whose state is controlled by processor126via control signal129. When closed switch SW2puts capacitor C2in parallel to tune the coil to the reflective state. When switch SW2is open, capacitor C2is removed from the tank circuit and the tank circuit is in the absorptive state. Binary data is sent in this manner, and induces binary encoded amplitude modulation in the stationary data receiver's coil. The switched reactive element may include at least one of a selectable capacitor (or a capacitive divider network).

FIG. 5shows an example of a capacitive divider network comprising capacitors C3and C4connected in series across transceiver coil130and a capacitor C5provided as shown. Depending on whether a logic 1 or a logic 0 is to be transmitted, the processor126can select whether or not to include capacitor C5and thus can vary the capacitance across the transceiver coil. Other techniques may be implemented as well for varying the impedance across the resonant tank circuit of transceiver coil130and capacitor C1.

FIG. 4also shows the use of multiple selectable taps66for impedance matching. Either tap66can be selected by processor126asserting a control signal131to a switch SW1to provide the selected tap to the rectifier128. By selecting a desired tap, the effective length of the transceiver coil130can be varied.

Referring now toFIG. 6, a cut-away view is shown showing the rotatable shaft90and a housing210provided about the shaft. The housing210includes the stationary data receiver104. The rotatable measurement interface102is shown attached to the shaft90.

Referring now toFIG. 7, a representation of a drive system300is shown. In some embodiments, the drive system300may comprise a portion of, for example, a helicopter. The drive system300generally comprises a primary drive shaft302, a parallel drive shaft304that takes power from the primary drive shaft302, and a plurality of intermediate drive shafts306that similarly take power to power loads308. The loads may comprise rotor hub components, electrical generators, fans, blowers, pumps, or any other rotationally resistive loads. The reference numerals100inFIG. 7represent pairs of rotatable measurement interfaces102and corresponding stationary data receivers102. The locations at which each rotatable measurement interface/stationary data receiver100are shown indicate non-limiting possible locations to be utilized with drive system300to ensure proper operation of all the various branches of such a drive system300. Each stationary data receiver of each rotatable measurement interface/stationary data receiver pair is communicatively coupled to an ECU110(not shown inFIG. 7). By including multiple rotatable measurement interface/stationary data receiver pairs, the relative torque levels of the various branches (e.g., each of drive shaft302, parallel drive shaft304, and intermediate drive shafts306) of the transmission system can be monitored by the ECU110. Such data can provide real-time or near real-time information on a multitude of driveline parameters including bearing condition, component alignment, lubrication conditions, improper shaft speeds and/or aging gearboxes. The rotatable measurement interface/stationary data receiver pairs similarly may be applied to any other complex machine, automobile, aircraft, production line system and/or power transmission systems that combine and divide the supplied rotational power at multiple points through a drive system.

The efficiency of the transmission system can be computed based on the signals from the various strain gauges. The transmission efficiency may be computed by the ECU110based on strain gauge data received from at least two pairs of rotatable measurement interfaces102and stationary data receivers104.

In some embodiments, the management of operation of system300may comprise operating the system to avoid and/or reduce overlap between (1) resonant/natural frequencies and/or harmonics of the resonant/natural frequencies of one or more components of the drive system300and (2) the frequencies of potentially damaging stresses, strains, forces, torques, powers, and the like. In alternative embodiments, the rotatable measurement interface/stationary data receiver pairs and associated components may utilize measured strain and estimated transmitted torque with information about a shaft rotational speed to estimate a transmitted power of the shaft so that the transmitted power data may be utilized by operators and/or electronics106and/or a computer to evaluate how to operate the drive system300more efficiently, thereby potentially saving fuel and/or other energy costs of operating the drive system300.

The embodiments described herein are examples only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.