Torsional actuator based on mechanically amplified shear piezoelectric response

A torsional actuator, based on the concept of mechanical amplification of piezoelectric shear strain and capable of generating large angular displacement, was proposed and studied experimentally. The actuator is a tube consisting of an even number of the segments poled along the length, which are adhesively bonded together, and the joints act as electrodes to apply the driving voltage. The experimental data measured on the prototype actuators (i) prove the proposed concept of mechanical amplification of small piezoelectric shear strain to generate large torsional motion, (ii) show that the actuator functions well both without load and under the torque load and (iii) demonstrate that the actuator can operate continuously for a long period of time without drop in its performance. Also, the results demonstrated that the proposed torsional actuator is capable of producing both large torque and large angular displacement in a compact package, sufficient to meet many smart structures requirements, and can be tailored for a variety of application requirements. Finally, one of the obvious advantages of the present design of the actuator is its simplicity: the piezoelectric shear strain is transformed directly into the angular displacement, whereas in the previously reported actuators, the conversion mechanism into the torsional motion was rather complicated which thus required a sophisticated design of the whole system.