Toward Improved Electromagnetic Tracking for Handheld Robotics.

We describe early efforts in design and development of an In-Loop Electromagnetic Tracker (ILEMT), designed to meet the demanding latency and resolution requirements for handheld robotic systems that perform active stabilization of hand motion during microsurgery. The objective is to surpass the best commercial electromagnetic trackers in latency while matching them in root-bandwidth/resolution. The concept is to use frequency-domain multiplexing for fast measurement and high accuracy during rapid motion, and bifrequency dual-path eddy-current compensation (reducing distortion from metals without sacrificing speed). The use of two widely spaced carrier frequencies (e.g., 300 Hz and 10 kHz) enables a particularly simple way of reducing the eddy-current interference caused by nonferrous metals. Previously, metal compatibility has come at the price of reduced measurement speed.