Piezoelectric inchworm rotary actuator with high driving torque and self-locking ability

•A piezoelectric inchworm rotary actuator using a double layer structure is proposed.•A maximum driving torque of 245 Nmm is achieved by the prototype.•Reliable self-locking torque of up to 882 Nmm is provided when the power is cut off.•Rotary speed of 26.74 mrad/s and minimum step rotary angle of 4.79 μrad are achieved.