Locomotion modes for a hybrid wheeled-leg planetary rover

This paper introduces locomotion modes for the planetary rover Sherpa1. The rover's locomotion system consists of four wheeled-legs, each providing a total of six degrees of freedom. The design of the active suspension system allows a wide range of posture and drive modes for the rover. Self-locking gears in the suspension system allow to maintain the body height without the need of actively driving the actuators. Thus, energy-efficient wheeled locomotion and at the same time high flexibility in ground adaption and obstacle negotiation are possible, as well as high payload capabilities. Furthermore, the rover will be equipped with a manipulator arm explicitly designed to be used for locomotion support. Thus, all degrees of freedom of the system can be used to enhance the locomotive capabilities. This paper gives an overview of the mechanical design of the rover, kinematic considerations for movement constraints on the wheel contact points are presented. Based on these constraints, the wheel motions due to the commanded velocities of the platform can be calculated, taking into account the flexible posture of the rover. A first set of possible locomotion modes for the rover is presented in this paper as well.