Development of rotary-linear piezoelectric actuator for MRI compatible manipulator

This paper presents the development of rotary and linear piezoelectric actuator (rotary-linear motor) for a surgical manipulator with MRI compatibility. The stator of the rotary-linear motor is fabricated as a single metallic cube with a through-hole and shaft is inserted to the through-hole. Four piezoelectric elements are bonded to the sides of the stator. When AC voltage at each resonant frequency is applied to the piezoelectric elements, the shaft can move to the rotary and linear directions. There are several control inputs such as the voltage, the frequency, and the phase difference of two AC voltages to control the motor. We have measured the characteristics of the control inputs. As the result, the control characteristics of voltages were linear and were better than those of the frequency and phase difference. On the other hand, the MRI compatibility test was conducted in 0.3 Tesla MRI. MRI image shows the practical quality of the image in the case of that the motor is placed at the center of the imaging volume of MRI while the motor is not driven.