Research Of The In-situ Dynamic Sinkage And Mechanics Between Planetary Exploration Rovers And Soil

As China’s lunar exploration project continues and the Mars exploration program established, the role of planetary exploration rovers is becoming more and more important. It can carry a variety of scientific instruments and autonomous mobile on the planet’s surface, which becomes an important way in planetary exploration. Researching on the dynamic rules between rovers’ wheels and soft terrain can avoid rovers from failure in motion, which is caused by slip and lateral skid, and it is the foundation of wheel’s designing and rover’s control strategy. This article studies the influence on the dynamic sinkage and mechanical characteristics in one of the driving wheels, which is based on the interrelated theory of terramechanics and used semi-empirical method.Wheels’ in-situ steering experiments are selected as it is done by researchers and wheels’ in-situ slipping experiments are carried out. The influence of vertical load and lug height are analyzed. It draws conclusion that vertical load, lug height and initial conditions of the experiments affect the results very much.Basing on the interrelated theory of terramechanics, wheels’ in-situ steering dynamic sinkage model is calculated by making integral of the stress between wheels and soil. And by analyzing the experimental data, two sinkage exponent formulas are got which are functions of the wheels’ steering angle. The steering moment model is built, and the reason of the existence of the error between the model and experiments’ results is analyzed. An improved steering moment model is obtained after changing the distribution of the stress of the wheels, and the model can reflect lug effects. By bringing in the concept of the wheel’s equivalent concentrated force, a simplified model of the moment is derived.Wheels’ in-situ slipping dynamic mechanics model is established. According to the experimental data, the sinkage exponent calculation formula is obtained, which is function of the wheels’ rotation angle. Through this model, the in-situ slipping dynamic sinkage model’s accuracy is highly improved. The expression form of the shear displacement of wheel is calculated. The dynamic mechanical models of the driving torque and drawbar pull are optimized. Further, in order to meet the real-time computation, the time-changing models of wheel sinkage, driving torque and drawbar pull is carried out through the way of data fitting. The functions that affect the relationships between driving torque and wheel sinkage and between drawbar pull and driving torque are got out.The maximum relative error of each model and determine coefficient are calculated and analyzed. The terramechanics_based models’ maximum relative errors are all within 10%, and determine coefficients more than 0.95. The numbers are 20% and 0.80 to the simplified models, despite some extreme situation. By comparing the models’ calculation results and experimental results, models have high precision, which means models can satisfy both calculation speed and accuracy.