Autonomous Navigation of Magnetic Microrobots With Improved Planning and Control in Complex Environments

Yueyue Liu, Haoyu Wang, Xiaoyu Wu, Juntian Qu, Xinyu Liu, Qigao Fan

Abstract: Magnetic field-driven microrobots have shown high potential in the field of medical applications. Autonomous navigation is a crucial concern for magnetic microrobots, however, the path planning, actuation and control of magnetic microrobots still remain challenging, especially for complex and large-workspace human body environments. Depending on the specific task and environmental conditions, it is important to employ appropriate planning and control architectures for the magnetic navigation systems. In light of this objective, this paper introduces a novel navigation framework, using an improved path planning and following control method. An evolutionary strategy based RRT (ES-RRT) planner is designed to achieve a shorter, smoother and safer path. Furthermore, an extended state observer (ESO)-based controller is specifically designed for the path tracking process of the microrobots. This controller enables the microrobots to accurately follow the computed path. Experiments demonstrate the effectiveness of the proposed strategy: Feasible path in different conditions and environments can be obtained with short and smooth enough, and autonomous navigation following of microrobots is realized with satisfactory path tracking control accuracy. Note to Practitioners—In contrast to macroscale robots, microrobots face challenges when it comes to integrating onboard components such as processors and power sources. Consequently, alternative methods have been developed, including optical, chemical, and biological actuation. Among these approaches, the utilization of magnetic fields is particularly favorable due to its ability to penetrate deep tissues while ensuring high safety. Additionally, magnetic fields offer diverse propulsion options, such as rotating fields and oscillating fields, along with excellent controllability. Despite significant advancements in the fabrication, functionalization, and locomotion of magnetic microrobots, autonomous navigation remains an area that requires further development. In the medical application, the planning path of the microrobots needs to be short and smooth enough. Besides, considering the unknown dynamics and external disturbances of the system, it is extremely important for microrobots to complete the precise path following control of the planned path. The motivation of this work is to develop an effective navigation scheme for microrobots which consisting of a path planner and motion controller. A shorter and smoother path will be planned based on a novel improved RRT planner. The precise control of the path following then will be achieved by adopting an extended state observer (ESO) controller. The proposed methods would enable microrobots to act safely and greatly enhance robots’ capabilities.