Modeling Analysis and Slip Estimation for Lunar Rovers
|School||Harbin Institute of Technology|
|Course||Control Science and Engineering|
|Keywords||lunar rover kinematics modeling dynamics modeling slip variable structure control|
The development of lunar rover is a complex systemic project involved many techniques of different areas. This thesis provides some primary development on the platform of eight-wheel rocker-bogie lunar rover with torsion bar. And these are the solid foundation for autonomous motion and control.Firstly,kinematics analysis of the lunar rover is presented in this thesis. Kinematics modeling which is suitable for uneven terrain is combined by tire-soil interaction modeling, rover structure modeling and slip modeling. Drive angle velocity and turning angle velocity can be calculated by inverse kinematics modeling for drive and turning problems. Optimization is being used in simulation with different types of terrains to testify the kinematics modeling in Matlab.Secondly, slip is the key factor in slip modeling. It can not be neglect in the motion of lunar rover on fine grained soil. Dynamics analysis is needed to solve this problem. Dynamics modeling is deduced from tire-soil interaction mechanics. Control modeling with slip ratio as state variable is simplified from dynamics modeling after its analysis.Finally, the exponent approaching sliding mode control is adopted in the controller of the slip control modeling. In order to reduce the chattering, the choice of the coefficient is discussed. Analysis is conducted after the simulation in Matlab. As the slip ratio could be controlled at the expected area, the slip can be calculated by the definition of the slip ratio. So the slip modeling is perfect and it provides important motion information.