Research On Driving Performance Of Lunar Rover Wheel And Its Comprehensive Evaluation

Wheel of the lunar rover, which contacts directly on the moon, can carry the whole weight of rover, generate traction force and feedback the necessary terrain information on the moon. It also has very important influence on moving ability, steering flexibility and adaptability on terrain. Thus, research on mechanical properties of wheel-terrain contact and actuating properties of wheel deeply has important significance to develop wheel with high performance. And it also is important for dynamic analysis, simulation, path planning, and relative technology of the whole rover. The dissertation mainly research on the actuating properties theory, simulation and experiment of the rover on homologous terrain. Evaluation method on actuating properties of the wheel is also a main part in it.To provide necessary sand parameters for the research on actuating properties and simulation analysis of the wheel, theoretical expression between sand parameters and confined characteristics and shear properties of sand is established. According to the specification of each parameter in equation on the test system, integrated test system for actuating properties of wheel and sand parameters is put up. The system is employed for confined and shear test. Then sand parameters are obtained through regression statistics of test data.Based on the theory of terrain mechanics, the mathematical model between wheel configuration, sand mechanical parameters, load, slip coefficient, traction performance and steering performance of wheel are built up. And the influence of wheel configuration parameters on the traction performance and steering performance are analyzed. Validity of the theory model is verified by experiments for predicting the drawbar force, steering torque and turning resistance torque. The theoretical model will be basis for optimization design of wheel configuration parameters and the evaluation system on wheel actuating properties.Sand distortion and force status has been analyzed utilizing the limit equilibrium theory of granular mechanics when the grouser and sand contact. Based on it, mechanical model of interaction between grousers and sand is analyzed. And then the model for traction performance of wheel with grousers is derivation. Relation of rational combination between grouser height and number is established through analyzing best state of cutting sand while multi-tooth contacting sand simultaneously. Influence on traction performance and steering performance of wheel by grouser parameters has been studied through experiments with various slip coefficients. Then influence on the wheel actuating performance by parameters of straight grouser, oblique grouser and mutual-angle grouser is obtained. Simultaneously, to provide reference experiment data for selection of slip coefficients when control the wheel actuating, variation relationship wheel actuating performance and traction efficiency with slip coefficients is studied. The research can provide the reference data and theory basis for analyzing the influence on actuate performance of grouser parameters, establishing the contact mechanics simulation model between grousers and sand, and rational selection of grouser parameter.To reflect perturbation properties of wheel on sand directly when wheel contacting with the sand with various slip coefficients and grouser parameters, simulation model of wheel moving properties based on discrete element is built up through imitating the influence of grousers on wheel actuating performance under low gravity. Stress distribution and moving characteristics are obtained through simulation when the wheel contacts with sand. The validity of simulation model is verified by experiments. As a method for researching on wheel actuating performance, this model perfects the method for analyzing t mechanical properties of wheel-terrain contact.Finally, the research on actuating performance evaluation methods and indexes of wheel is proposed in this dissertation based on theoretical research, simulation and experiments of wheel actuating performance. Evaluation indexes of wheel actuating performance and dimensionless relation among parameters of wheel-terrain contact system are determined based on the dimensional analysis method. And the comprehensive evaluation system for actuating performance of wheel is built. Actuating performance of wheels with various width-radius ratios are evaluated comprehensively based on this evaluation system, which provides theory basis for design of wheel configuration.