A Novel Discretely Actuated Steerable Probe for Percutaneous Procedures

We have developed a discretely actuated steerable probe for percutaneous procedures. We propose use of shape memory alloy (SMA) actuators in our design due to their small size and high power density. SMAs are attractive actuators when large forces or displacements are required and limited spaces are available. SMA actuators are shape-setted to an arc shape and mounted on the outer surface of the probe to generate bending action upon thermal actuation. SMA can recover large deformation on thermal activation and recovery strain of SMA is related to its temperature. Hence, we propose controlling the temperature of the SMA actuators for position control of the probe by heating up the SMA wires at each joint. Pulse width modulation (PWM) based control scheme is used to be able to control all SMA wires simultaneously. PWM is implemented via use of a switching circuit. Proposed controller is validated through an experiment to heat up the SMA wires to a desired temperature. Another experiment is carried out inside gelatin to mimic the motion of the probe inside soft tissue. PWM control was successfully implemented and we were able to demonstrate local actuation of the steerable probe.