Design and experimental validation of a disturbing force application unit for simulating spacecraft separation

Abstract

The separation of the heatshield and backshell as the spacecraft enters the atmosphere and decelerates is a highly challenging task during the exploration of an exoplanet. Owing to its high complexity, few experimental validations have been performed so far for this separation process. In this paper, a novel disturbing force application unit is designed, which can simulate the disturbing forces and disturbing moments. It is deployed in a cable-driven parallel mechanism which is used to simulate the heatshield and backshell separation. This cable-driven parallel mechanism is presented from the aspects of mechanical design, kinematic analysis, dynamic analysis, numerical simulation, and experimental validation. First, the kinematic and dynamic model of the cable-driven parallel mechanism is established. Then, the definition of disturbing force controllable workspace is proposed. The workspace quality coefficient, which checks whether the end-effector is close to the workspace boundary, is presented. The configuration design is discussed. Third, numerical simulations are implemented to investigate the effects of axial forces, disturbing forces and disturbing moments on the end-effector position and orientation. Finally, an experimental platform is built. Experimental verification of the separation of the heatshield and backshell in different conditions are implemented. A series of experimental results show that both heatshield and backshell are safely separated from the lander. The proposed cable-driven parallel mechanism can accurately simulate the disturbing force during the separation process of the heatshield and the backshell.