Coupled and decoupled actuation of robotic mechanisms

We describe two types of seemingly opposing design and control concepts for the realization of a high performance robotic system. One of them is the "coupled drive". It is a design and control strategy to maximize the output power of the robotic system by actively coupling the drive of installed actuators. We show two design examples of the coupled drive; design of leg mechanism and gait control of the wall climbing robot NINJA-II and design of a multi-DOF manipulator CT-Arm. Another is the "GDA", or gravitationally decoupled actuation. This is a design and control strategy to maximize energy efficiency of robotic systems by means of decoupled drive of installed actuators. We show two design examples based on the GDA; design of leg mechanism and control of quadruped walking robots. In the final part of the paper, we discuss a methodology to merge the two above-mentioned seemingly contradictory design methods, and apply the merged concept to posture control of a walking robot on a 3D terrain.