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SUMMARYIn medical interventional procedures such as brachytherapy, biopsy and radio-frequency ablation, precise tracking through the preplanned desired trajectory is very essential. This important requirement is critical due to two major reasons: anatomical obstacle avoidance and accurate targeting for avoiding undesired radioactive dose exposure or damage to neighboring tissue and critical organs. Therefore, a precise control of the needling device in the unstructured environment in the presence of external disturbance is required to achieve accurate target reaching in clinical applications. In this paper, a shape memory alloy actuated active flexible needle controlled by an adaptive sliding mode controller is presented. The trajectory tracking performance of the needle is tested while having its actual movement in an artificial tissue phantom by giving various input reference trajectories such as multi-step and sinusoidal. Performance of the adaptive sliding mode controller is compared with that of the proportional, integral and derivative controller and is proved to be the effective method in the presence of the external disturbances.

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In this paper, closed loop nonlinear control of a shape memory alloy (SMA) actuated flexible needle is presented. Merits of different modalities of sensory feedbacks are studied. In order to track the given desired trajectory, the actual position of the needle tip is controlled using three different feedback signals (i) Vision, (ii) Electromagnetic (EM), and (iii) Ultrasound (US) imaging feedback signals are considered independently. From the experimental results it appeared that the EM sensor feedback control of the flexible needle has the best tracking performance compared to the other two feedbacks.  Index Terms-first term, second term, third term, fourth term, fifth term, sixth term