Abstract-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 allow robust control of the desired speed and torque of the internal rotor and this is demonstrated through experiments.
Abstract-This paper introduces Non-collocated Stator-Rotor Synchronous Motor (NSRSM) as a novel actuation system for cases where the stator and rotor are required to interact across a physical barrier. The main motivation for NSRSM is in the area of laparoscopic robotic surgery whereby it is desired to actuate the manipulators across the abdominal wall, but it also has potential application in other robotic surgery procedures. The configuration of NSRSM is similar to that of permanent magnet synchronous motor (PMSM) although due to asymmetric structure of the windings around the rotor, the electromechanical model of PMSMs was developed to obtain the dynamic model of NSRSM. The field oriented control method is used to develop an appropriate model for control purposes. Then two widely used control algorithms (PI controller and linear quadratic regulator (LQR)) are used to control the rotor speed in the presence of the modelling uncertainties and load disturbances. Simulation results show that these two methods are robust.
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