High-fidelity landing modeling of small-body probes: Considering solar panel deformation and soil properties

A high-fidelity dynamical model that can depict the touchdown of a probe on a small body is fundamental for precise control and is critical to the success of a landing mission. However, such models are lacking in the literature, and existing models fail to adequately account for soil properties on the small body or flexible parts (solar panels) on the probe. In this study, we develop a dynamical model with dynamics, contact, and control modules to simulate a legged probe with solar panels landing on a small body with weak gravity, unknown soil properties, and rugged terrain. The dynamical equations for the probe landing are derived by considering the solar panel deformation. A valid method for calculating the penetration depth is proposed to address the contact between the probe and soft soil based on Polygonal Contact Model (PCM). Theories of terra-mechanics and Coulomb friction are introduced to characterize the physical properties of the soil. Numerical examples illustrate the natural/controlled landing sequence and demonstrate the validity of the dynamical model. Compared to the rigid-body dynamical model, flexible solar panels increase energy dissipation and thus make the controlled-landing probe less prone to bounce repeatedly on a small body. In the natural landing mode, the solar panels cause the probe to fluctuate continuously. For the physical properties of the soil, both larger friction moduli and smaller internal friction angles are detrimental to the stable landing of the probe on a small body.