Research On Dynamics Of Combined Contact Mode Of Wheel-ground On Planetary Rovers

The planetary rover is an important tool for exploring the moon and Mars,which requires it to be able to operate on the complex terrain of planets.The research of wheelground interaction dynamics model plays an important role in design of planetary rover,navigation control system design,performance evaluation and the dynamic simulation of planetary rover.The wheels of planetary rover can be divided into rigid-wheels and flexible-wheels.At present,the research on wheel-ground interaction dynamics models of planetary rovers mainly focuses on the interaction models of rigid-wheel and soft soil.The topography of the planet's surface is not just soft soil,but there are also rocks in some terrains.Therefore,it is extremely necessary to study wheel-ground interaction dynamics models of rigid-wheel and flexible-wheel of planetary rover in mixed terrain containing rocks.In order to establish an accurate planetary rovers' dynamics model with wheelground contact force,the theoretical models of rigid-wheel and soft soil,rigid-wheel and bedrock,flexible-wheel and bedrock,and flexible-wheel and soft soil interaction dynamics models were studied.Wong-Reece's interaction model was used as the pressure model in the dynamic model for wheel-soil contact.The sinkage and drawbar pull models were modified and then verified by experimental results.Janosi's model was used as the shear model.Based on Hertz contact theory,a friction nonlinear spring damping model was adopted as the wheel-bedrock interaction model.The deformation of the flexiblewheel was analyzed with the help of finite element software to obtain the radial equivalent stiffness of the flexible-wheel in the wheel-bedrock contact.Wong-Reece's interaction model was used as the pressure model in the dynamic model for wheel-soil contact.Janosi's model was used as the shear model.The contact area between the wheel-soil was divided into three sections for research.The model is further corrected.The Lagrange method was used to establish the dynamics equation of planetary rover with wheel-ground contact force,which provided a basis for establishing the dynamics model of the planetary rover with wheel-ground contact force.An additional terrain stiffness array was introduced for setting and recognition the mixed terrain in the ground mechanics parameters.Based on the co-simulation platform of navigation and dynamics on planetary rovers,the corresponding simulation program was programmed to form the dynamic simulation ability of the whole vehicle with four wheel-ground interaction models.Taking a planetary rover as an example,the whole vehicle model of planetary rover was established by Adams.The dynamic simulations of a planetary rover on the horizontal soft terrain,horizontal mixed terrain,soft terrain of slope and mixed terrain of slope were carried out respectively.Combining the performance indicators of planetary rover such as wheel velocity,normal force,drawbar pull force and driving resistance moment torque in simulation results,the mobile performance of the planetary rover on various terrains was studied.The results showed that the rover's velocity fluctuated greatly on the mixed terrain,the support force,drawbar pull force and driving resistance moment changed sharply,and the rover might gain greater drawbar pull force comparing with the results of traveling on only soil terrain.