Disturbance Rejection in Multi-DOF Local Magnetic Actuation for Robotic Abdominal Surgery

The potential of multi-degrees-of-freedom (DOFs) local magnetic actuation (LMA) has been established in recent years for dexterous minimally invasive surgical manipulations. Nonetheless, having multiple magnetic based units, one for each DOF, within a close vicinity to each other leads to magnetic field interaction among the magnetic sources, hence resulting in a disturbance to a given LMA unit. It is further realised that the disturbance is a result of actuation effort by the neighbouring magnetic sources forming the LMA units, and that the actuation command to all LMA units is a known information to the controller. Therefore, partial information of the disturbance is known and can be exploited in a disturbance rejection strategy. In this paper, this disturbance is modelled and used to augment a simplified model of the systems dynamics of the LMA-based surgical manipulators. The internal model principle (IMP) strategy is therefore selected in which an observer is designed to estimate the disturbance to be rejected. Numerical simulation as well as experimental validation were performed to validate the efficacy of the IMP. The results serve to remove another significant technical hurdle in bringing the new emerging technique of Local Magnetic Actuation into practical reality for abdominal surgeries