Nonlinear Model Predictive Control for Free Floating Soft Space Robot System

The growing demand for space exploration has intensified interest in the performance and capabilities of space robotic systems. Traditional rigid space robotics are often hindered by limitations such as structural rigidity, limited adaptability, and suboptimal safety characteristics. In contrast, bioinspired robotic systems, constructed from compliant materials, offer significant advantages, including reduced mass, enhanced flexibility, and improved adaptability to unstructured environments. This paper presents a Nonlinear Model Predictive Control (NMPC) framework for trajectory tracking in a cable-driven soft space manipulator considering a free-floating scenario. The dynamic model of the soft robotic system was formulated using the Euler-Lagrange method to capture the coupled dynamics between the manipulator and the spacecraft base. Based on the derived model, an NMPC strategy was developed to achieve precise end effector trajectory tracking. Numerical simulations demonstrated the effectiveness of the proposed control approach, with a maximum deviation of less than 0.04 m and a final error on the order of $10^{-6} \mathrm{~m}$. In addition, this paper presents a soft robot prototype and a preliminary grasping experiment. The grasping experiment, conducted on a flat surface under Earth’s gravity, demonstrates that it is capable of grasping a 1U CubeSat.