Robustness Evaluation of Internal Model Principle-based Controller in a Magnetically Actuated Surgical System

The local magnetic actuation (LMA) surgical method has gained popularity among medical practitioners and researchers in the field of abdominal surgery. The procedure requires the use of magnets on both sides of the abdominal cavity to anchor devices onto abdominal wall while magnetic sources on the external side generate actuation signals to drive robotic manipulators inside the cavity. Due to the transmission of magnetic fields across the abdominal wall and the interactions among multiple LMA units within the vicinity, magnetic interference will affect the performance of the intended rotor driving the degree-of-freedom (DOF) on the robotic manipulator. Since the disturbances due to the neighbouring magnetic sources are found to be sinusoidal signals with a known frequency, they can be rejected by using the internal model principle (IMP) technique. The disturbance due to the abdominal wall tissue dynamics during magnetic actuation causes oscillations on the internally anchored surgical device, which has generally been ignored in the implementation of LMA application. The focus of this paper is to provide a model that incorporates tissue dynamics in the LMA system. Moreover, the robustness of IMP controller in the presence of tissue dynamics is discussed. Simulations are performed and the results demonstrate effective rejection of both disturbances when they are taken into account in the IMP disturbance model.