Measuring Torque and Temperature in a Rotating Shaft Using Commercial SAW Sensors

Abstract

Real-time monitoring of torque in a rotating shaft is not easy to implement with technologies such as optic fiber sensors or strain gages. Surface acoustic wave (SAW) sensors are wireless and passive and can be used to monitor strain in moving parts. Commercial solutions (sensors, antennas and interrogation unit) can easily be purchased from some companies; however, they are not customized and may not meet the specificity of the measurements. In order to evaluate the adequacy of commercial off-the-shelf (COTS) solutions, temperature and strain sensors fabricated by SENSeOR (Besançon, France) were mounted on a load cell. The sensors were calibrated using a thermal chamber and a universal testing machine. The load cell was then assembled together with a steel shaft that rotated at different speeds inside an oven. The commercial antennas were replaced with an RF (radio frequency) coupler and the sensors were interrogated with the commercial interrogation unit. The influence of rotation in the accuracy on the measurements, as well as the adequacy of the sensors structure, was evaluated. It can be concluded that SAW sensors can be used to measure temperature or torque in a rotating environment; however, some customization of the components is required in order to overcome the limitations posed by COTS sensing solutions.

Reader Architectures for Wireless Surface Acoustic Wave Sensors

“…Last but not least, influences from the environment, such as multiple reflections, or the interface, when using, e.g., a rotational coupler, make a fair comparison even more difficult. Nevertheless, the realized FDS SAW reader systems presented so far [ 49 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ] show exactly the previously discussed architecture-specific advantages and limitations.…”

Ring-Shaped Sensitive Element Design for Acceleration Measurements: Overcoming the Limitations of Angular-Shaped Sensors

“…To exclude the mutual synchronization of the two self-excited oscillators (5) and (6), the resonant frequencies of the single-cavity resonators should be sufficiently separated. The output signals of the oscillators (5) and (6) are multiplied by a frequency mixer (7). Application of external acceleration leads to the cantilever bending, such that the SE surfaces experience stress-strained deformations.…”

“…In recent years, integrated micromechanical solutions based on surface acoustic waves (SAW) resonance principles have attracted broad interest and suggested several potential applications, including biomedical and/or sports wearable devices [1,2]; vehicular designs, [3,4] including UAVs [5]; and temperature sensors [6][7][8]. In the current literature, various aspects of SAW sensor design and its manufacturing technology have been investigated thoroughly.…”

Comparison of AlN vs. SIO2/LiNbO3 Membranes as Sensitive Elements for the SAW-Based Acceleration Measurement: Overcoming the Anisotropy Effects

“…Recent developments based on monolithic solid-state constructionsare characterized by relatively high stability of parameters, low energy consumption (0.5-1 W) [1]. Although SAW-based micromechanical accelerometers (MMA) are currently still under development, commercially available SAW sensors are widely used in other applications ranging from medicine and life safety to unmanned devices exemplified by vapor and gas analyzers [2][3][4], temperature control systems [5,6] as well as pressure detection systems [7].…”