H∞ Output Feedback Controller Design for Flexible Needles Guidance

Precise and reliable needle insertion into human body, especially soft and inhomogeneous tissues, in order to keep away the needle from sensitive organs is a controversial issue for medical tasks, such as percutaneous interventions, biopsy and some kinds of radiation therapy (brachytherapy). Steerable or flexible bevel-tip needles have an asymmetric tip that causes the needle to bend, and needles can reach the target by deflection over insertion. Getting feedback from imaging devices can improve the objectives. In 2D motion planning it is so important to keep and stabilize the needle in a desired plan. Since the tissue type changes during insertion that causes uncertainty parameter so it is a big problem to keep the needle in the desired plan. In this paper we propose a robust controller with the H-infinity output feedback approach to overcome the uncertainty and disturbances. This controller is applied to a linearized model of steerable needles. Simulation results are presented to show the feasibility of the scheme.