Stiffness Modeling and Force Distribution for the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE)

Abstract

The All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) is a six limbed vehicle designed for both mobility and manipulation. Each limb has six active degrees-of-freedom, plus a powered wheel. Along the axis if each wheel is a mechanical interface that allows the integration of tools that can make use of the wheel actuator. Thus each limb can act as a leg for walking, an active suspension for a driven wheel, or a manipulator with an actuated tool. Fundamental to the operation of the system is the ability to control limb pose, overall body pose, as well as regulate limb forces. Joint torques are estimated from the difference between the incremental and absolute encoder readings on each joint. Forces are then computed from joint torques and force regulation is performed by modifying the limb positions. Force regulation allows the vehicle to lift larger payloads and traverse terrain while actively complying to terrain features.