Sensing and Cancellation of Tremors in Surgeon's Hands during Microsurgery

摘要

Physiological tremors reduce the precision of surgeons during microsurgery. Active cancellation of tremor will improve the results of microsurgery. It will also lead to the development of more sophisticated surgical procedures, previously considered difficult to perform. Tele-robotic systems, steady-hand robot and Micron active hand-held instrument are currently existing techniques for tremor cancellation. We propose the design of an active glove, capable of sensing the surgeon’s hand tremors and compensate them by generating counter forces on the surgeon’s fingers. The proposed mechatronic system for the active glove consists of inertial sensors (accelerometers and gyroscopes) and actuators, to be mounted on the fingers, both interfaced with custom-designed microcontroller board. This work presents the design and development of various aspects of the proposed system. First, a prototype board was designed and developed specifically for this application, using dsPIC33F family microcontroller. The design allows interfacing multiple sensors and actuators, and also provides on-board power management and safety features. Interfacing of inertial sensors and implementation of a complementary filter for estimation of finger tip orientation is successfully demonstrated. Further, the challenge of isolating tremor motion from voluntary surgeon motions is accomplished by implementing an adaptive filter. Future algorithms would need these for efficient cancellation of tremors. The development of actuators (either pneumatic or electro-active polymer-based) to be mounted at the finger nodes was outside the scope of this project. Therefore, an existing single-axis flexure-based manipulator system with voice coil actuator was modified to implement the proposed control algorithm. The proportional plus derivative (PD) control shows promising results in reducing tremors at the surgeon’s tool tip by 92%, when holding at a point and by 31% while carrying out a voluntary motion.