Mechanical design of a hopper robot for planetary exploration using SMA as a unique source of power

Abstract

Planetary exploration will soon engulf the majority of space activities for many nations around the world. However, the cost related to this type of mission is extremely steep. Recently, the satellite business has been revolutionized by the advent of small satellites and micro-satellites. Such spacecrafts now provide space mission opportunities with price tags several orders of magnitude below classical satellites. It is for this reason that the Canadian Space Agency (CSA) has decided to investigate micro-planetary missions. The present work deals with mechanical design of a hopping robot prototype destined for the exploration of planets with a low gravitational environment (Mars for instance). This robot uses diurnal variations of temperature at Mars’ surface as a source of power. An “innovating” cylindrical mechanism with scissors used to transfer the energy needed by the robot's jump was designed, manufactured and tested. Moreover, an actuator with shape memory alloy (SMA) working with the sun's heat was designed, while a prototype was tested. The robot's design shows the following characteristics: a unique actuator is used to load the energy needed for the jump to torsion springs and to reposition the robot back on its feet after having hopped. The robot's structure, in the shape of tetrahedron, is confined to a 300 mm edge length cubic envelope, which corresponds to a status of “micro” robot. The target mass for the entire system is 1–2 kg. The proposed concept takes advantage of the Martian environment. In fact, the low gravity and the low atmospheric density favor jumping as a means of locomotion, while the important gradient of temperature (day versus night) at the surface of Mars enables the elongation of the SMA. Consequently, jumping lets us cover longer distances while crossing the numerous rocks that cover the hazardous surface of Mars. This article, based on experimental development, presents an overview of the important elements of the preliminary mechanical design.