Automated 3-D Electromagnetic Manipulation of Microrobot With a Path Planner and a Cascaded Controller

Manipulating microrobots to move in a 3-D space is a basic requirement for their in vivo medical applications. In this study, the automatic manipulation of a microrobot in a liquid 3-D space via an electromagnetic coil system is investigated. A path planner is designed to search an optimal path in a 3-D space with obstacles automatically, and a cascaded control algorithm is developed to control the microrobot's movement along the planned path. The path is generated by combining the A-star and minimum jerk methods. The collision of the generated path with the obstacles is prevented and the hysteresis caused by the current change is minimized by reducing the jerk of the movement with a passable path from the starting point to the endpoint. In the cascaded control algorithm, the incremental nonlinear dynamic inversion (INDI) method and a proportional control are used as the inner and outer loops to guide the microrobot's movement along the desired trajectory with an appropriate velocity while eliminating the influence of system uncertainty and external disturbances. Simulation and experiments are performed to verify the effectiveness of the proposed control strategy.