Design of a novel rotary-linear pneumatic actuator integrated with ultrasonic motion control mechanism

The rotary-linear actuator is a main type of multi-degree of freedom actuators and it has been widely applied in the fields like robotics, drilling process, and so on. To realize the rotary-linear output movement, the status transformation of screw locking/unlocking is controlled based on ultrasonic friction reduction. A novel Rotary-Linear Pneumatic Actuator (RLPA) is proposed in this paper. The actuator mainly includes a cylinder, a decoupling mechanism and an ultrasonic motion control mechanism. In order to excite the effect of ultrasonic friction reduction, an ultrasonic vibrator by attaching 12 rectangular PZT plates on the surfaces of flange nut with cantilever structure is designed. The dimensions of PZT plate are 15 mm × 6 mm × 1 mm (length × width × thickness). The vibration performance of ultrasonic motion control mechanism is analyzed by finite element method. The analysis results indicate that the second bending vibration mode of ultrasonic vibrator is excited at a resonant frequency 22.78 kHz. A prototype of the actuator is fabricated and the vibration characteristics are tested. The results state that the vibration performance of the actuator with screw is in good agreement with the actuator without screw.