Modelling and Control of Local Electromagnetic Actuation for Robotic-Assisted Surgical Devices

This paper proposes an electromagnetic based Local Magnetic Actuation (LMA) as a novel actuation system for cases where it is required to actuate a mechanical system across a physical barrier. The main motivation for LMA is in the area of minimally invasive robotic surgery where it is desired to actuate the surgical manipulators across the abdominal wall. In the Local ElectroMagnetic Actuation (LEMA) approach, it is proposed that the magnetic field is produced by a pair of electromagnetic stators, acting across a physical barrier (the abdominal wall) and interacts with the magnetic field of the permanent magnet rotor on the other side of the barrier. The mathematical model of the electromechanical system is developed by exploiting the principles of synchronous motors. Control strategy was then developed to regulate the rotor speed in the presence of model uncertainties, load disturbances and axes misalignment. Furthermore, the performance of the controllers is evaluated in two cases: with Hall effect sensor embedded internally in the abdominal cavity close to the permanent magnet rotor and placed externally to the abdominal cavity close to the stators. The main contribution is the application of electromagnetic strategies in the unique setting of rotor actuation across a physical wall, focusing mainly on the dynamics modelling of the resulting structure and evaluation of its performance for surgical application. The proposed model and actuation strategies allows robust control of the desired speed and torque of the internal rotor and this is demonstrated through experiments.