Initial design characteristics, testing and performance optimisation for a lunar exploration micro-rover prototype

In the field of space and planetary missions, the use of robotic systems for exploration tasks has become quite common. The recent emergence of private ventures will increase the number of missions in the upcoming years, but the budget for each one of them will have to be considerably lower than that of government based projects. With celestial bodies the size of the moon, sending a single rover has become inefficient for full surface exploration, mapping and resource prospecting. To achieve these objectives, two main fields require further research. Firstly, reducing single rover cost by making them smaller and simplifying their on-board equipment. Secondly, collaboration strategies for large groups of rovers should be devised to enable faster surface exploration. We are currently working on a 1 kg, three-wheeled rover prototype called Koguma. This platform is, first and foremost, to demonstrate the potential of deploying small rovers for planetary exploration. The simple design and low manufacturing cost associated with it will enable the integration of a larger number of prototypes, opening up more possibilities of field testing the collaboration software. The main concern surrounding this category of rovers is to determine the limits of their motion performances. In order to qualify for planetary missions, traversal capability over loose soils of various steepness has to be assessed. In this paper, we present the design characteristics of this initial prototype. Inherited from previous generations of two and three-wheeled rovers, we start by explaining the main motivations towards this model. From mass budget to dimensions, materials and system architecture, we will explain the ideas and reasoning behind our choices. We will then present the results surrounding initial performance tests on the Koguma platform. We conducted slope climbing experiments using an orientation controllable sandbox. Mobility performance is assessed by evaluating the relationship between wheel key parameters and capabilities. These parameters are: radius, width, and grouser size of the front wheels. Through this, we propose a first approach of design recommendations for the development of light, three-wheeled rovers.