Michel Lauria, Roland Siegwart
During recent years the European Space Agency (ESA) has started to develop concepts for micro-rovers for planetary missions. An ESA Technology Research Program (TRP) activity "Micro-Robots for Scientific Applications" has been dedicated to this subject. Within an interdisciplinary group of space companies and research labs new designs of micro-rovers have been investigated. Two concepts, a simple and robust one and an innovative one, have been selected and functional breadboard models of them are currently built. After a discussion of the key issues for robust locomotion the present paper will focus on the design, implementation and control of SpaceCat, the more innovative solution selected as breadboard model B whereas the complementary work on breadboard model A is described in detail in [1]. It consists of 6 independently driven wheels arranged in two triangles. It therefore allows not only for efficient rolling on flat surfaces but also to step on obstacles. Additionally the center of mass and the instrumentation carrousel is adjustable, allowing to optimally balance the micro-rover in almost every situation. Even after flipping over the robot will always be able to get back on its wheels. To navigate the rover autonomously within a range of about 10 to 20 meters from the lander, an active vision system is used with a camera on the lander. It allows to control the robot through a very user-friendly interface. Local piloting and obstacle avoidance is based on various on board sensors. This enables robust and collision free operation even in rough terrain. ESA defined the following main requirements and constraints: o Stowed dimensions envelope (cm): 30 x 20 x 20 o Net mass of the robot system:max. 2 kg o Mass of the scientific payload:2 kg o Electrical power provided by lander:max. 2 Watt average, max. 3 Watt peak o Possibility to position the on board sensors: accuracy around 1 mm o Maximum speed: 5 m/h The rover must overcome obstacles of 0.1 m height and holes of 0.1 m width. It has to be able to climb slopes of 15° upwards and 20° downwards. Simple maneuvers like turning and moving backward is required too. Moreover, to ensure mission success the following requirements have been identified: o No risk of sinkage and getting stuck in the sand o Flip-over stability o Recovery after flip-over and after having been buried by a sand storm
1998
