Traction Control Design and Integration Onboard the Mars Science Laboratory Curiosity Rover

The Mars Science Laboratory (MSL) Curiosity rover
experienced increasing wheel damage beginning in October
2013. While the wheels were designed to operate with considerable
damage, the rate at which damage was occurring was
unexpected and raised concerns regarding wheel lifetime. The
Jet Propulsion Laboratory (JPL) has now developed and deployed
new software on Curiosity that reduces the forces acting
on the wheels. Our new Traction Control algorithm adapts each
wheel’s speed to fit the terrain it drives over. It does not rely on
any a priori knowledge of the terrain, and instead leverages the
rover’s measured attitude rates and suspension angles, together
with a rigid-body kinematics model, to estimate the real-time
wheel-terrain contact angles and ideal, no-slip wheel angular
rates. In addition, free-floating “wheelies” are detected and autonomously
corrected. In this paper, we describe the algorithm,
its ground testing campaign and associated challenges, and
finally its validation and performance in flight. Ground test data
demonstrates reductions in the forces acting on the wheels and
validates the wheelie-damping capability. Secondary benefits in
some terrains include a reduction in heading deviations while
climbing rocks, with a reduction in slip in certain sandy terrains.
Preliminary validation from flight data confirms these findings.