Research On Experimental And Model Of Wheel-soil Interaction For Planetary Exploration Rover Wheels With High Slip-sinkage

Since the 21 st century,deep space exploration has developed rapidly,China is expected to carry out the first Mars exploration mission in 2020.The future deep space exploration will face more complex terrain and more challenging exploration tasks.The wheel-leg rover can combine the advantages of high energy efficiency of wheeled motion and high adaptability of gait motion,and become the optimal scheme of Mars rover in China.The more complex exploration environment and the new structure of Mars rover will bring the high slip condition of the wheel.The serious high slip motion will make the wheel lose the traction ability,and then cause the occurrence of rover stuck.However,the previous research on high slip is relatively less.The terramechanics with high slip motion is a bottleneck problem in the future deep space exploration.Experimental study is an effective method to study the terramechanics.The stress state of wheel movement in soil is analyzed,and the wheel sinkage,drawbar pull,driving torque,traction coefficient and resistance coefficient are used as test evaluation indexes.Single wheel test is carried out by using single wheel test bed and test wheel.The effects of speed effect,load effect,wheel lug effect and the effect of slip ratio are studied.It is found that the dynamic sinkage of the wheel will occur under the condition of high slip,and the change rule of the evaluation indexes such as drawbar pull is different from that under the condition of low slip.A three-wheel planetary vehicle is used for the whole vehicle test.The experimental study provides the experimental basis for the subsequent mechanism analysis and model establishment.The key to improve the prediction accuracy of the dynamic mechanical model of wheel-ground interaction is to analyze the dynamic mechanism of the wheel sinkage based on the macroscopic test phenomenon and the terramechanics knowledge.The experimental results show that the drawbar pull increases first and then decreases with the increase of the sinkage under the condition of high slip,and the causes of the slipsinkage phenomenon are explained from the perspective of macro mechanics.Based on the resistance force theory,the static bearing capacity of soil is modeled,and the flow pattern of soil particles in the process of wheel dynamic sinkage is analyzed.Finally,the stress distribution in the process of wheel movement is calculated theoretically by the terramechanics model,and the influence of soil flow on the stress distribution of wheel is analyzed.The derivation of the mechanical model of wheel-ground interaction is the basis of the application of the theory of terramechanics.According to the change rule of wheel sinkage,the time-varying fitting model for dynamic sinkage is established,and based on the analysis of soil pressure bearing characteristics,the basic framework of the sinkage prediction model is formed.The sinkage index in the wheel-ground interaction model is identified,and the time-varying fitting model of sinkage index is obtained.By analyzing the prediction performance of the wheel-ground interaction model under low slip,the shortcomings and improvement direction of the existing model are found.By modifying the wheel stress distribution,the wheel-ground interaction model for dynamic mechanical under high slip is finally established.In this paper,the mechanism of wheel dynamic sinkage is analyzed from three aspects: test macroscopic phenomenon,soil mechanics theory and terramechanics theory.A dynamic mechanics prediction model of wheel-ground interaction under high slip is established.It provides a mechanical basis for further deep space exploration and the development and application of the wheel-step rover.