Adaptive observer-based controller design for a class of nonlinear systems with application to image guided control of steerable needles

Flexible needles with a bevel tip (steerable needles) promise to enhance targeting accuracy and maneuver inside the human body in order to avoid collision with delicate organs. Contributing image feedback to needle insertion tasks greatly improves such objectives. An important issue in 2D motion planning tasks is stabilizing the needle in a desired plane. Any divergence from the plane leads to the inefficiency of the motion planning scheme. Hence, a control scheme is proposed in this paper which guides the needle to a desired plane. The system of such task is subject to parametric uncertainty. Although the original system is linearly parametrized, the feedback linearized form is not, which prevents the application of conventional adaptive control schemes. Moreover, all state variables of the system could not be measured and a nonlinear observer is necessary to observe the system states. In this paper, the previously proposed adaptive state feedback controller for such systems is modified to an adaptive output feedback controller and the proposed scheme is applied to the problem of needle guidance. Simulation results are presented to illustrate the enhanced performance of the proposed controller methodology as compared to previously proposed feedback linearization scheme.