Rover reconfiguration for body-mounted coring with slip

Active and passive approaches to accommodating moderate rover slip during coring, using a body mounted coring tool were studied. The work addresses the possibility of a 200 kg rover experiencing moderate slip such as 1 cm/minute while coring on a Martian slope using a body-mounted coring tool in a possible future Mars Sample Return mission. Rover slip while coring could be accommodated with passive compliance or active rover reconfiguration. A passive compliance device was designed that constrains the compliant motion of the tool relative to the rover to a plane with travel of approximately 1.5 cm. Active reconfiguration relies upon wheel motion and a transverse linear stage to provide actuation of the coring tool position in the nominal wheel plane. The rover actively reconfigures utilizing six axis force feedback of the forces and torques on the coring tool. Rover slip is measured using Absolute Motion Visual Odometry (AMVO). Rover reconfiguration is demonstrated while coring on a slope with slip. However, the implemented body mounted coring tool approach is fundamentally limited: First, no out-of-plane actuation is considered, negating the possibility of rover roll and pitch compensation. Second, wheel-ground interaction could cause unintended system responses when wheel motion occurs, including motion in the uncontrollable roll and pitch degrees-of-freedom.