Autonomous Navigation of Soft Rolling Microrobots Under a Helmholtz Coil System Across Fields of View Using Image Stitching

Under the guidance of an integrated control and imaging system, magnetic microrobots have the capability to navigate within narrow spaces to perform tasks such as cargo delivery and manipulations. However, due to the difficulty of balancing image resolution and width of the field of view (FOV), achieving accurate autonomous navigation of microrobots in large workspaces remains a significant challenge. This letter introduces a control strategy aided by image stitching to address this challenge. First, an image stitching algorithm based on key point matching, a motorized mobile platform, and a camera were used to obtain a global map that spanned multiple FOVs. Then, an A* global path planning algorithm was used to calculate the collision-free optimal path. Next, a key point matching method was used to calculate the local path in the FOV where the microrobot was located. Finally, a closed-loop control algorithm and the mobile platform were used to guide the microrobots to the endpoint in the global space. This control strategy was demonstrated in experiments using soft alginate microrobots in microchannels that spanned multiple FOVs. Experiments showed that this method was able to obtain global maps of large workspaces with high accuracy through image stitching and guide microrobots through different environments with different channel geometries. The results of this work demonstrated the possibility of using microrobots for automated tasks in more than one FOV, which can significantly widen the range of microrobotic applications.