Design and Control Strategy of a Non-Gravity Axes Tracking System for a Rigid Suspension-Type Astronaut Operational Training System

Low-gravity and microgravity simulation devices for training astronauts to manipulate objects under terrestrial conditions are critical for improving operational performance and efficiency in extraterrestrial environments while minimizing risk. To this end, a rigid-suspension-type astronaut operational training system (RSAOTS) was developed, which can precisely simulate the motion characteristics of target objects in low/microgravity environments. In the RSAOTS, to realize rapid and extensive inertial motion of the target object along non-gravity axes, we designed a non-gravity axes tracking system (NGATS). The NGATS adopts an X-Y-X Cartesian robot configuration and is driven by timing belt linear modules. The composite compliance control strategy of NGATS comprises two loops: the inner loop uses active disturbance rejection control to precisely control motion, whereas the outer loop integrates human–robot interaction admittance control with constraint disturbance force control. This control strategy effectively minimizes the constraint disturbance force exerted by the NGATS on the target object, retaining only its inertial characteristics along the non-gravity axes. The feasibility of the NGATS configuration and composite control strategy was validated through microgravity environment simulation experiments conducted along the non-gravity axes. Experimental results show that for target objects with a mass of 37.5 kg, the NGATS adopts the proposed control strategy, the root mean squared errors of the constraint disturbance force are 0.1828 N in the X-axis and 0.3321 N in the Y-axis.