Resonant SAW torque sensor for wind turbines

A novel plate torque transducer based on UHF SAW resonant sensing elements has been developed allowing an easy aftermarket installation of passive wireless torque sensors on large diameter shafts by means of clamping. A design of a large diameter RF rotary coupler for wireless interrogation of the transducer was proposed that had a gap of 20 mm between the stator and the rotor and was insensitive to axial and radial misalignment as well as the rotation angle. The two plate transducers and the RF coupler were installed on a high-speed shaft of a wind turbine gearbox. The torque sensor accuracy achieved after calibration on a test shaft was better than 1% full range within the temperature range from +20°C to +80°C.