The Research On Lunar Rover Dynamics Based On Elastoplastic Wheel-terrain Mechanics And Viscoelastic Kinematic Pair

To develop and test the guidance, navigation and control system of the lunarrover, a simulation platform is necessary to simulate the kinematic behaviors anddynamic performance of the rover. But the low-gravity environment and special soilparameters of lunar surface bring strict demanding for rover modeling, model re-solving, and rover control. According to the model machine of lunar rover used inChinese lunar exploration, a dynamic model is developed, based on the elastoplasticrigid wheel-soft terrain mechanics and viscoelastic kinematic pair constraints,with the resolution of system constraint discussed in depth. An independent tractioncontrol system is designed based on the model.The special soil character parameters of lunar surface are researched. With asimplified equivalent wheel-terrain contact model, and linearized stress equation, thenormal force, the tangent force and the lateral force between the wheels and the ter-rain are derivated. A method based on virtual points detection is presented to detectthe contact relationship and evaluate the geometrical parameters between the wheelsand the terrain.Combined with the wheel-terrain contact model, the lunar rover dynamic modelis established, with the dynamic state equation is analyzed, uses position, gesturequaternion, linear momentum and angular momentum of each part as the state vector,and the dynamic state equation was resolved by numerical integration, to get the ve-locity, angular velocity, position and attitude of all parts of the rover. The viscoelas-tic motion constraints of the joints are analyzed, and the resolution of the classifiedconstraints are discussed. As a keynote, the Dantzig method based on Lagrange mul-tiplier is discussed, to solve nomal and lateral constraints of contact joint.An closed-loop traction control system is designed. The velocity cooperativecontrol considering the slip of wheels is used for the traction control, with the goalto track rover direction velocity and angular velocity from the strategy system.According to the model machine of lunar rover, a3D visualization simulationplatform is developed, to evaluate the dynamic model, the wheel-terrain model, theresolving algorithm of constraints, and the traction control system. Experiment re-sults show that the model is accurate and steady-going, the wheel-terrain contact andmotion can be factually simulated, the joint constraints are fulfilled and resolved fast, the decision motion can be tracked accurately, which denote importance academicand practical meaning for the lunar rover to accomplish the detect mission and fu-ture work of improvement.