Dynamics modeling and stability analysis of lunar crew vehicles on uneven terrain

The lunar crew vehicle (LCV) is crucial for the safe and efficient mobility of astronauts on the lunar surface. However, the low-gravity environment and rugged terrain of the Moon present unique and significant challenges to LCV operations. With gravitational acceleration approximately one-sixth that of Earth, uneven terrain greatly affects the vehicle's dynamic performance, often causing pronounced pitching and, at higher speeds, wheel-ground separation, which increases instability risks. This paper introduces three dynamically switching pitch dynamics models based on an adaptive footprint wheel-ground contact model to study wheel-ground contact and pitch stability over convex obstacles. Each model, comprising one sprung and two unsprung masses, captures dynamics during wheel-ground contact and separation. A finite state machine (FSM) is employed to switch between different models and manage state transitions based on the contact status of the wheels with the ground. Stability is assessed using two indicators: the time all wheels are off the ground (t_off) and the maximum change in the vehicle's pitch angle (θ_M). Simulations under various conditions show that driving parameters and vehicle configurations significantly affect LCV dynamics. This work offers theoretical insights for optimizing LCV design to improve safety and stability during lunar surface operations.