A Sequential Hermaphrodite Coupling Mechanism for Lattice-based Modular Robots

Lattice-based modular robot systems have been envisioned for large-scale construction in extreme environments, such as space. To optimize system weight and power consumption, heterogeneous approaches combining active and passive coupling interfaces have been explored. Coupling mechanisms for heterogeneous structural modules must satisfy challenging requirements: maintaining flat surfaces when uncoupled, enabling single-sided coupling and decoupling, and compatibility with passive interfaces. We propose a novel mechanical coupling mechanism that addresses these challenges by actively transitioning between male and female states. The design integrates multiple practical features: 90° rotational symmetry, electrical pathways for communication and power supply, and mechanical hooks that maintain secure connections even without power. Experimental validation demonstrated the reliability and practicality of the mechanism, confirming its tolerance to misalignment, the sufficient load capacity, and effectiveness of its current-based failsafe system. This coupling mechanism represents the first solution to simultaneously achieve these capabilities, enabling efficient and reliable reconfiguration of heterogeneous modular robotic systems.