Control of multi-dof ultrasonic actuator for dexterous surgical instrument

For surgical devices used in minimally invasive surgery, compact multi-degree-of-freedom (multi-dof) actuators are required due to a small work space in the patient body. With conventional single-dof actuators such as electromagnetic motors, a multiple number of actuators are required to generate multi-dof motion. Moreover, additional transmission mechanisms make the total system even larger and heavier. In contrast, a single unit of multi-dof ultrasonic actuator can generate multi-dof rotation of a spherical rotor by utilizing three natural vibration modes of a bar-shaped stator. In our previous work we designed and built a surgical forceps with a wrist capable of two-dof motion, using a single multi-dof ultrasonic motor. The present study proposes a novel control scheme to generate three-dof motion of the surgical instrument for minimally invasive surgical procedures. Through experiments we have confirmed the system performance of the developed device.