Research On Dynamical Property For Handling Lunar Roving Vehicle

Lunar roving vehicle(LRV) is of great significance for the manned lunar exploration, and is an indispensable detection tool. It is important for the astronauts to know the dynamical property well to ensure the safety of them, because the environment of lunar surface is harsh and unknown, and the astronauts need to handle the LRV to avoid the obstacles and craters. Thus, before the astronauts landed on the moon, they must be trained driving LRV on earth. However, there are big deviations of the dynamical property for handling LRV because of the different gravities of the moon and earth, and the drivers will have different driving sense on the moon after training on earth using the same vehicle. Therefore, to eliminate these deviations and give some driving advices for the astronauts, it is necessary to have the research on the different handling dynamical properties caused by different gravities and to find a training method on earth without different driving senses for the astronauts.Because the lunar surface is paved the loose soil, the mechanical model between wheel and soil is the base to study the dynamical property of the LRV and to establish the visual simulation model. By deducing the forced-slip solving method of a single wheel and whole vehicle’s wheels, the solving method of lateral force for the LRV’s wheel is obtained, and it is revised by the equivalent terramechanical calculating coefficiencies for the elastic and mech pattern. Then, an experiment system with error compensating algorithm for the LRV’s wheel is established, and the vertical load is loaded by a torsion spring. Finally, the equivalent terramechanical calculating coefficiencies are obtained by the experiment and parameter identification method, and the relative cornering stiffness of the LRV’s wheel can be calculated. The acquisition of the cornering stiffness is the theory support and experiment evidence for the vechiel dynamical model and visual simulation model.It is the base for the research of dynamical property for handling the LRV to deduce dynamical functions, establish dynamical system, and integrate relative cornering stiffness of LRV’s wheel. In addition, the equivalent roll stiffness and damp in the dynamical model cannot be obtained directly. Thus, the calculation method for the equivalent roll stiffness and damp, which is validated in the simulation, is deduced, and the accuracy of the dynamical model is improved. The yaw velocity, slip angle, lateral acceleration, moving path, roll angle, roll velocity, and lateral transfer ratio of the vertical load are analyzed, and the results show that the LRV under the lunar gravity has the lower handling flexibility and stability, more obvious lateral slip, and more rollover danger for the driver than the vehicle moving under the earth gravity.The dynamical inverse system based on radial basis function neural networks for handling the LRV is establish using the dynamical system which has been deduced above. The mathematical models of moving path for the input of the inverse system are deduced, and the solving method of driver handling input for the same moving path under different gravities is obtained. The driver handling input when moving specific path can be obtained using the inverse system of the LRV, and the deviations of driver handling inputs under different gravities and soil parameters are analyzed. The solving results of the inverse system show that the astronauts on the lunar surface need to handle the LRV with higher steering speed and magnitude, more frequent handling switch, and more difficult than driving on earth.After analyzing the deviations of dynamical property caused by different gravities using dynamical and inverse system, the necessity to training astronaut driving an LRV on earth without different driving sense has been proved. Two imitating method has been proposed: physical parameter imitating method and control method based on H￥ theory. The former method need to use a imitating vehicle with specific parameter, but this method need a specific vehicle and specific soil parameter which is hard to construct. The latter method uses an imitating vehicle with imitating control method and without specific vehicle parameter. Therefore, the latter method has the better applicability, and the high imitating accuracy has been proved by calculating.The virtual dynamical simulation model of the LRV is established, and the LRV’s handling dynamical system, inverse system, imitating control method based on H￥ theory is validated. The simulation results proved the correctness of the system and imitating method.The handling dynamical property of the LRV under different gravities and soil parameters has been analyzed, the imitating method based on H￥ theory to imitating vehicle moving on lunar surface under the earth gravity has been proposed, and the virtual simulation model has been established to validating the correctness of the dynamical system and the imitating method. The dynamical property analysis and imitating control method provide good solution plan for training astronauts driving an LRV on earth, and give driving advices for the drivers on the lunar surface.