Sensing Physiological Tremor in a Hand-held Microsurgical Instrument

INTRODUCTION Physiological tremor is an involuntary, approximately rhythmic and roughly sinusoidal movement [1]. It is inherent in all humans. The characteristics of physiological tremor are highly dependent on the body parts [2]. For instance, the frequency of tremor in the elbow ranges from 3 to 5 Hz while it ranges from 8 to 12 Hz in the wrist. Physiological tremor is benign for everyday tasks such as walking or eating. However, tasks that require fine muscle control such as microsurgery or military targeting are susceptible to physiological tremor. The imprecision in positioning the tool-tip due to the tremor makes some ophthalmological, neurological and inner ear microsurgeries difficult [3]. Therefore, real-time compensation of physiological tremor would enable surgeons to accurately perform microsurgeries. A handheld microsurgical device, Accuracy Improvement Device (AID), has been developed to actively compensate for the physiological tremor in the hand. The device senses its own motion using inertial sensors and differentiates between voluntary motion and motion incurred due to the tremor followed by compensating for the tremor by deflecting its tool-tip in the equal but opposite direction to that of the tremor. The sensor module of the device containing the inertial sensors is presented in this abstract followed by a description of the algorithm to estimate the displacement of the needle-tip due to the tremor. SYSTEM DESIGN A. Sensor Module Fig. 1 shows the prototype of AID built at CSTAR. It weighs 23.56 gm and is 192 mm long (including the needle). It consists of three parts: sensor module, manipulator module and body. The sensor module of AID is located at the distal end of the device as shown in Fig. 1 and senses the hand motion in six degrees of