Dynamics Analysis and Stability Control of a Lunar Unicycle Self-Balancing Robot

The one-wheeled self-balancing mobile system has superior mobility and flexibility due to its unique configuration and single-wheel grounding feature, and can autonomously perform exploration and delivery missions on narrow, rough and unstructured surfaces. In this paper, a one-wheeled self-balancing robot traveling on the lunar surface is proposed for autonomous exploration on the lunar surface. Firstly, a multi-body dynamics model of the robot is derived using the quasi-coordinate-Hamilton equations. Wheels in soft ground not only generate velocity deviations due to slip and slide, but also introduce additional travel resistance moments at the dynamics level due to soil deformation during wheel sliding. Therefore, a three-dimensional terramechanics model is used to characterize the coupling between the robot wheel and the soil. To achieve stability control of the robot's attitude, a series PID method is used for pitch self-balancing and velocity control. A model predictive control (MPC) method is used to control the lateral balance of the robot. The whole robot model and control strategy are built in MATLAB/Simulink, and the traveling stability of the robot is verified on flat soil terrain and rough soil terrain.