A novel Terramechanics testbed setup for planetary Rover wheel-soil Interaction

Abstract

For planetary rovers, demonstration of the overall mobility performance on soft soil is a demand to guarantee for mission success. Since several years, DLR’s Institute of Robotics and Mechatronics is strongly engaged in planetary mobile system developments. For the very important wheel-soil interaction a 3D-MBS tool for modeling and simulation of the overall terramechanics behavior, making use of Bekker’s well-known terramechnical equations, has been developed. Currently, major applications are followed within ESA’s Exomars mission. For the purpose of verification and validation of the 3D-MBS tool intensive hand in hand rover testing in a lab environment is necessary. Therefore, a new facility for planetary locomotion systems including a large testbed and a novel, high-precision bevameter to characterize the soil on which the tests are to be carried out is presented. For precise rover pose estimation inside the testbed a high-level position tracking system is used, and for proper soil surface determination on an in-house developed digital elevation mapping system is relied on. For the Bekker parameter determination, a portable and lightweight bevameter equipped with a state-of-the-art sensor technology is designed. Different design concepts are analysed open minded without any orientation on existing bevameter designs. This leads to a tripod design with electromechanical actuators and sensors integrated in a real-time computing environment to develop own control algorithms. Besides soil testing and soil preparation influence detection, the bevameter is mainly used for identifying soil parameters of the testbed. Finally, for correlation purposes, these parameters are taken as inputs to the 3D-MBS tool for simulating the drive manoeuvres performed inside the testbed. Results obtained from bevameter testing are presented together with the testbed setup design.