Reversible Formation Control of Multiple Miniature Robots Under Global Magnetic Stimuli in Confined Spaces

Multiple collaborative miniature robots are capable of performing more complex tasks and adapting to more dynamic environments than a single miniature robot. However, controlling the formation of multiple miniature robots in close proximity remains a challenge, as they are all driven by the same control input. In this paper, we propose a novel control strategy to achieve reversible formation transformation of three miniature robots under global rotating magnetic fields. The interaction dynamics of three identical magnetic robots at the air-water interface is analyzed for acquired interaction law. Based on this, a sequential controller is designed to assembly the robots into a straight line or a triangle as needed by regulating the frequency of the rotating magnetic field. Simulations and experimental results indicate that the multiple miniature robots can be reversibly assembled into the desired formation using the controller we designed. This control strategy provides a preliminary approach to solving the problem of controlling three or more identical magnetic miniature robots' formation, which is expected to enable multiple miniature robots to accomplish complex tasks collaboratively in unknown environments.