An Active Hand-held Instrument for Enhanced Microsurgical Accuracy

This paper presents the first prototype of an active hand-held instrument to sense and compensate physiological tremor and other unwanted movement during vitreoretinal microsurgery.  The instrument incorporates six inertial sensors (three accelerometers and three rate gyros) to detect motion of the handle.  The movement of the instrument tip in three dimensions is then obtained using appropriate kinematic calculations.  The motion captured is processed to discriminate between desired and undesired components of motion.  Tremor canceling will be implemented via the weighted-frequency Fourier linear combiner (WFLC) algorithm, and compensation of non-tremorous erroneous motion via an experimental neural-network technique.  The instrument tip is attached to a three- degree-of-freedom parallel manipulator, actuated by three piezoelectric stacks.  The actuators move the tool tip in opposition to the motion of the tremor or other erroneous motion, thereby suppressing the error. Experimental results show that the prototype is able to follow one-dimensional and three-dimensional trajectories with rms error of 2.5 μm and 11.2 μm respectively.