Motion Control for a Planetary Exploration Rover with Six Steerable Wheels

IARES is a highly flexible planetary exploration demonstration rover developed mainly for autonomous navigation and locomotion studies. It has 19 degrees of freedom, including six active, steerable wheels. The rover has software for autonomous navigation, including stereo camera perception, path planning and motion control. It is complemented by a visual simulator that can substitute the real rover for practical purposes. The goal of this MSc thesis, carried out at CNES in Toulouse, has been to make the most of the locomotion capabilities of this rover. Given the hardware platform and and the software environment, the partly developed motion control system had to be studied. It was decided to improve parts of the existing motion control system by fixing smaller problems and doing adjustments to the behaviour. Extensions in form of so-called crab-like movements were also studied and developed. This includes using the steering capabilities of all six wheels of the rover in order to obtain a translational movement. The extensions were implemented into the existing control algorithm. The studies were conducted on a Solaris platform. Code was developed in C. The new performance was tested in the simulator and the results were analysed. The six-wheel steering extensions provided more flexibility to the motion control, by allowing position and heading deviations to be corrected independently. The rover managed to correct its position deviations more quickly, and to increase its locomotion speed.