A versatile, compact and collapsible resistance training device for on-orbit astronaut

• A novel, modular, cable-driven robot for on-orbit physical exercise that is both high-performance and easily storable is proposed. • The robot integrates multiple exercise modes within a compact and collapsible structure suit for the confined space station. • An intelligent human-machine safety strategy based on a Finite State Machine (FSM), which actively monitors the exercise state of the astronaut and provides real-time protection against hazardous movements. • A high-fidelity force control system, comprising a dynamic force distribution model and a force controller based on the principal of the structural invariance, which ensures accurate tracking of both constant and variable resistance loads. • A full-scale prototype is built and validated through human-machine interaction experiments, confirming its feasibility and performance. Substantial evidence demonstrates that long-term exposure to microgravity leads to physiological deconditioning in astronauts, including musculoskeletal dysfunction, loss of bone density, and decline in cardiovascular system function. Physical exercise is currently recognized as the most effective method to mitigate these adverse effects. This paper proposes a cable-driven resistance training device that offers multiple advantages, including integrated exercise modes and a compact, collapsible structure for efficient storage. A cable-driven unit (CDU) with controllable length, velocity, and force has been designed. Furthermore, a human-machine safety strategy based on a Finite State Machine (FSM) is proposed, and a corresponding force distribution model is established. A force controller based on the structure-invariant is introduced to achieve high-fidelity cable force. The efficacy of these components and the system configuration were verified through simulation studies. Finally, a hardware prototype was built. Validation and deep-squat experiment results demonstrate that the system configuration, safety strategy, force distribution model, and force controller are effective. This confirms that the device is a promising solution for helping astronauts conduct physical exercise during spaceflight.