Design of a Manipulator for Planetary Rovers

Abstract

This paper addresses the stages for selecting the concept of an arm suited to carry out the various scientific operations of planetary robotic explorations: sample recovery, supply of the on-board analysers, soil drilling and testing capabilities, rock inspection, probe/beacon deposit, tool manipulation, etc. After a study of these requirements from a geometrical point of view, the comparison of the various candidate designs leads us to retain a 3 dof pantographic system. It should cooperate with a redundant parallel wrist. The location of the base, the lengths of the links and the joint ranges are then optimised with respect to the operational and folding constraints, given a sketch of the vehicle. A stiffness analysis allows us to select the link rigidities. Finally, the actuators and the drive mechanisms characteristics are derived. The result is a trade-off for taking into account the maximum allowed bending error, the mass and the energy consumption. The preliminary design described in this paper is devised to exert a 20 N force and to allow a 0.5 cm/s tip velocity for 30 W peak power. The arm can fold within a volume smaller than 20 liters. Its estimated mass is about 5 kg, and the control is simple, thanks to the pantographic arrangement.