Saw-based Sensor Design For Applications Of Ship Propeller Shaft Torque Detection

Information of rotary torque is of significant importance in someapplications, for example, it can be used to assess the efficiency ofmechanical equipment, to improve handling and braking of trucks and cars,and so forth. In comparison to other torque sensors, including resistive straingauges, optical transducers, and torsion bars, surface acoustic wave (SAW)torque sensors offer lower cost, higher reliability even with strongelectromagnetic interference, and contactless slip ring free operation.A wireless torque sensor, based on two one-port SAW resonators, ispresented in the paper, which is suit for propeller shaft on ship. Differentialmeasurement based on double SAW resonators structure is employed tomodel the physical relation between differential frequency and strain due totorque. The effects of temperature, installation and alternation of radiodistances can be reduced as much as possible. Design of the sensor allows foreliminating the influences from an installation error and additional stresseseffects, and then reducing them with by measuring the change of differencefrequency. The equivalent circuit model approach has been used to researchantenna impedance matching in order to get maximum transmit power. Andthe interrogation and efficient signal processing technologies are discussed.Some power spectrum estimation algorithms with high frequencyresolution from the reflective sensor echo are discussed in detail. The effectiveness of BURG algorithm is verified by MATLAB simulation. Thefrequency resolution is up to700Hz in the practical digital signal processingsystem.