Hardware-independent control for partial gravity simulation using a 2-DOF robotic device

A variety of physiological changes in the human body have been observed to occur under the microgravity conditions of space. 3D clinostat devices capable of implementing time-averaged simulated microgravity (taSMG) have been widely used to predict these changes on Earth and to identify their underlying mechanisms. Recently, the concept of time-averaged simulated partial gravity (taSPG), which mimics the gravitational environments of the Moon (0.17 g) and Mars (0.38 g), has been proposed as an extension of taSMG, and clinostat control algorithms capable of implementing it have been developed. However, existing taSPG algorithms are dependent on specific hardware, limiting their versatility. Further, they are unable to generate taSPG levels exceeding 0.44 g. To address this limitation, we propose an improved control algorithm and validate it through both simulation and experiments. By applying an algorithm that does not depend on the characteristics of individual clinostat hardware, we confirmed the accurate implementation of taSPG up to 0.809 g. By adjusting the parameters, taSPG levels approaching 1 g can also be achieved. Notably, for taSPG in the range of 0.265 g to 0.635 g, the experimental values demonstrated refined accuracy with approximately 1% or less deviation from the simulation results.