RoboMag: A Magnetic Actuation System Based on Mobile Electromagnetic Coils With Tunable Working Space

Magnetic field is regarded as a safe and efficient method for controlling minimally invasive medical robots remotely, and magnetic actuation system based on mobile electromagnetic coils are preferred due to the enlarged working space and fast response. Enhanced flexibility on coils' positions will further enable the system to deal with possible constraints inside the workspace, while design and control of such flexible systems remain challenging. In this work, a magnetic actuation system based on three mobile electromagnetic coils with decoupled movements is designed and the performance is demonstrated. The system consists of three 4-axis robotic arms that can adjust the relative positions of three mobile coils independently. The prototype of RoboMag is designed and able to program magnetic field at a required point inside a hemispherical space with a diameter of 152 mm. A method to drive the mobile-electromagnetic-coil-based systems with flexible movements is proposed. To begin with, a model of the robotic platform is built to place the coils to demanded position. A numerical model of a single coil is constructed and average error of magnetic field is reduced to 3.30% after calibration. Afterwards, a method based on coordinate transformation is proposed for the entire system to produce demanded magnetic torque and force at a required position. Experiments are conducted to demonstrate the system's capability on generating magnetic torque and force to actuate medical device analog.