LRU - LIGHTWEIGHT ROVER UNIT A. Wedler (1) , B. Rebele (1) , J. Reill (1) , M. Suppa (1) , H. Hirschmüller (1) , C. Brand (1) , M. Schuster (1) , B. Vodermayer (1) , H. Gmeiner (1) , A. Maier (1) , B. Willberg (1) , K. Bussmann (1) , F. Wappler (1) , M. Hellerer (2) , R. Lichtenheldt (2) (1) DLR - German Aerospace Center, Institute of Robotics and Mechatronics (Germany) , armin.wedler@dlr.de (2) DLR - German Aerospace Center, Institute of System Dynamics and Control (Germany), matthias.hellerer@dlr.de ABSTRACT This paper presents the novel Lightweight Rover Unit (LRU) developed at DLR-RMC Robotic and Mechatronic Center. The LRU rover is a terrestrial prototype based on the experiences gained with the mobile payload element (MPE) rover which has been originally developed for the ESA lunar lander mission. The small MPE lunar rover was foreseen for collecting and fetching samples on the lunar surface. This paper describes the development of the small and lightweight LRU rover prototype with respect to kinematic aspects, the electronic perspective and the control point of view. The LRU is equipped with a highly sophisticated autonomous navigation system, which is also briefly described in this paper. The LRU paves the way towards a small space qualified exploration rover. The technology readiness level (TRL) of its incorporated substantial robotic modules has been increased and the components and technologies developed for the LRU can be reused for future developments. 1. INTRODUCTION The Lightweight Rover Unit LRU from DLR–RMC is a new innovative mobility device tailored to the needs of planetary exploration and terrestrial search and rescue applications. It is designed to operate and to manipulate objects on moderate to challenging terrain e.g. for fetching and handling samples and it allows exploration of large areas in a fast and efficient manner. Due to its lightweight design and total mass of less than 30 kg, it is a promising additional payload for any future lunar mission. The rover concept is strongly inspired by the Lunar Lander Mobile Payload Element (MPE) and is in line with similar intended international planetary exploration missions e.g. ongoing Russian or Indian plans for small lunar mobility vehicles. The design of the rover system is based on DLR’s long experience in designing lightweight actuator units and robotic systems. The overall design process is continuously supported by simulation and a detailed evaluation of the performance even before hardware is available. The concurrent engineering workflow allows efficient and reliable design. The LRU rover locomotion subsystem (LSS) and its potential suitability for space applications have been given highest priority. The LSS has therefore been designed in a space qualifiable manner and a future upgrade to a fully space qualified version has been considered from the very beginning respectively. The four wheeled LSS system is fully steerable. All LSS actuator units are based on a combination of a powerful brushless DC motor and a harmonic drive gear box. In addition to the four wheel actuators and four steering actuators two serial elastic bogie actuators allow to actively control the front and rear bogie joints. This allows e.g. controlling the load distribution to the wheels and the body orientation while maintaining the advantages of passive suspension. The wheels design, also a combination of rigid (e.g. tire tread) and flexible (spokes) elements, is additionally supporting fast and efficient driving in rough terrain. The lightweight design, the advanced kinematics and the unique combination of active and passive chassis elements result in a very high traffic ability, terrainability and overall mobility performance. Figure 1: The LRU in rough terrain. The rover body and related remaining subsystems like power electronics, battery and communication are designed for terrestrial applications and based on reliable and cost-efficient commercially available components-off-the-shelf (COTS) as development time and performance have been the main design drivers. Finally a commercially available complete robotic arm is integrated to enable mobile manipulation with the rover. In order to fully exploit the capacity of the mobile system, an appropriate navigation algorithm and autonomy is implemented. Such high level control algorithms, e.g. the implemented autonomous way point navigation, are key elements for future exploration missions. As they strongly rely on perception sensors like cameras, the rover system includes a novel PanTilt