A novel piezoelectric rotary actuator with a constant contact status between the driving mechanism and rotor

Taking advantage of simple structure and control, stick-slip piezoelectric actuators have been widely employed to realize precision positioning in precision machinery and instrument. However, their output characteristics could be significantly affected by the contact status between the driving mechanism and the mover (or rotor). If the contact status changes in the motion process, strong nonlinearity will appear in the displacement-time curve, deteriorating the performances. To achieve a constant contact status, the gravity of the rotor was used in this paper, and accordingly, a novel stick-slip piezoelectric rotary actuator was developed. The structure design, motion principle, as well as output characteristics of the actuator were addressed and discussed in detail. Experimental results indicated that when the driving frequency was below 350 Hz, stable stepping motions with quite small backward motion could be achieved. By changing the driving frequency, voltage and radius, various stepping rotation angles and speeds were easily obtained. The output characteristics changing with the vertical load were further characterized. Furthermore, by simply changing the direction of the driving waveform, forward and reverse rotation motions showing good linearity with time were achieved in a very large motion range, corresponding to a millimeter scale linear displacement. Comparative experiments with a normal stick-slip actuator further confirmed the validity and advancement of the proposed strategy for keeping a constant contact status, which will be beneficial to the subsequent motion control and mass production.