To fulfill success of the space mission, the traversability of lunar/planetary exploration rover is a key aspect of mission success. However, lunar surfaces are covered with loose regolith and has numerous steep slopes in certain area to be explored. So that achieving mobility and improving tractive performance of rover are indispensable and are also difficult problem. Also the wheel design and traction control for minimizing driving resistance/energy losses and maximizing tractive performance are required.
Chapter 2 describes the modeling of operation environment for lunar/planetary exploration rover. For lunar and planetary exploration rover, solar panels are promising candidate of power generation sources. The amount of obtained power depends on sun’s position such as solar altitude and azimuth angles. Thus, we considered the solar radiation condition for the modeling of operation environment and proposed conceptual design of exploration rover considering operation environment. Also, to identify the accurate terrain parameter in lunar simulant, two experimental methods were described. First, pressure-sinkage test was performed to identify the parameters of normal pressure and sinkage based on lunar simulant. And the terrain parameters concerning the shear stress are used the experimental data of Korea Institute of Civil Engineering and Building Technology. From the experimental data, the Levenberg-Marquardt method was utilized to derive the terrain parameters associated with normal and shear stresses.
Chapter 3 proposes the design and modeling for optimal shape of rover wheel. First, to design optimal shape of rover wheel and derive optimal driving conditions of rover based on operation environment, wheel-soil interaction model is described. Using this model and operation environment for lunar/planetary exploration rover, wheel design methodology provides optimal shape of rover wheel with limited power consumption.
The preliminary experiment of mobility performance for validating wheel-soil interaction model is presented in Chapter 4. For the evaluation of driving performance according to slip ratio and width of wheel in lunar simulant, we constructed a test bed of the rover wheel consists of the driving part of the rover wheel and sensing part of the various parameters. Using the test bed, the preliminary experiment of the sinkage, drawbar pull and tractive coefficient according to variation of the slip ratio and wheel width were carried out and evaluated. In addition, the experimental results were compared and discussed with the simulation results based on the wheel-soil interaction model.