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Percutaneous intervention has attracted significant interest in recent years, but many of today's needles and catheters can only provide limited control of the trajectory between an entry site and soft tissue target. In order to address this fundamental shortcoming in minimally invasive surgery, we describe the first prototype of a bioinspired multipart probe that can steer along planar trajectories within a compliant medium by means of a novel “programmable bevel,” where the steering angle becomes a function of the offset between interlocked probe segments. A kinematic model of the flexible probe and programmable bevel arrangement is derived. Several parameters of the kinematic model are then calibrated experimentally with a fully functional scaled-up prototype, which is 12 mm in diameter. A closed-loop control strategy with feed-forward and feedback components is then derived and implemented in vitro using an approximate linearization strategy that was first developed for car-like robots. Experimental results demonstrate satisfactory 2-D trajectory following of the prototype (0.68 mm tracking error, with 1.45 mm standard deviation) using an electromagnetic position sensor that is embedded at the tip of the probe.
Date of Publication: Oct. 2011