Development of point-symmetric modular legged mobile robot capable of operation after falling

This study presents a legged mobile robot based on a regular polyhedral structure that achieves a point-symmetric body configuration. The proposed framework enables dynamic allocation of manipulator roles based on a single reference vector (e.g., gravity), allowing consistent functionality across different body orientations without posture-specific control. The approach was validated through simulations on three polyhedral structures (octahedral, dodecahedral, and icosahedral) and hardware experiments using an octahedral robot. Experimental results demonstrate that the robot can perform grasping and crouching behaviors in all six stable orientations, while locomotion is achieved in two orientations under the current actuator constraints, with an average locomotion speed of 0.092m/s across 10 independent trials. In addition, stable posture recovery was confirmed across 10 independent fall-recovery trials with an average recovery time of 2.26s. The results further showed that the same posture representation and role assignment algorithm could be consistently applied across different polyhedral geometries without modification of the control structure. These findings indicate that point-symmetric design provides a viable framework for achieving orientation-independent operation while maintaining a minimal and generalized control structure.