Entwicklung eines echtzeitfähigen Rimless-Wheel-Modells zur Beschreibung des Rimless-Wheel-Walking für einen modularen elastischen Explorationsrover

Abstract

At the present time, space exploration is dominated by wheeled rovers. Being able to investigate planetary surfaces close up, these rovers are a keystone for further exploration of extraterrestrial bodies. Their operation range is however limited to areas of relatively smooth surfaces. To access areas of tougher terrains like caves, the German Aerospace Center (DLR) has developed a rover based on an alternative locomotion concept: the rimless wheel. By removing the wheel’s rim, the spokes are getting used as legs. Therefore the resulting locomotion is a combination of rolling and walking. The rover’s legs consist of compliant spokes and foot elements. This brings numerous advantages. However, it makes the analysis of the rimless wheel walking complex. In the context of this thesis, assuming quasi-static conditions, a method for describing an entire revolution of the wheel’s deformation conditions on a flat surface is developed. The spokes’ deformation is modeled by using nonlinear Euler-Bernoulli beam theory. A calculation method is derived for the deformation behavior of the foot elements based on a series of measurements. The derived model equations are solved numerically using a MATLAB algorithm. The developed calculation model is validated using a measurement on the Terramechanics Robotic Locomotion Laboratory testbench at DLR. This shows potential for improvement, particularly in the description of the compliant foot elements. Parameter studies are carried out on the basis of the calculation model to investigate the relation between the holding torque, the weight force, the actuating angle and the deformation. Based on these results, an approximation method for real-time calculation of the deformation states is developed. This uses linear interpolation to generate results for all equilibrium states. The developed model still offers potential for improvement, but appears to be a suitable method for describing the rolling process of compliant rimless wheels. The calculation model presented can therefore serve as a basis for further investigations.