Development of closed loop coordinated control of a robot guided SMA actuated flexible active needle with multimodal sensory feedbacks

An experimental evaluation of a two loop coordinated control strategy of a robot guided shape memory alloy (SMA) actuated flexible needle system is presented in this paper. The control of the flexible needle is deployed as the inner loop and the robot driving the needle in correspondence with the needle's movement is deployed as the outer loop. These two control loops are coordinated in such a way that the desired curvilinear trajectory for the needle tip is achieved with an acceptable accuracy. The control performance in trajectory tracking with three feedback modalities, i.e. Electromagnetic (EM) sensor, Vision and Ultrasound (US) imaging is presented. Results from the experiments reveal that the control performance with EM sensory feedback has smaller error (RMSE =0.04mm) compared to the other two feedbacks. However, tracking performance with US imaging feedback is comparable to EM sensory feedback, thereby, may be a good option for imaging based robot-assisted needle intervention for clinical applications.