Coupled and decoupled actuation of robotic mechanisms

In this paper, 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 a leg mechanism and gait control of the wall-climbing robot NINJA-II, and design of a multi-degrees-of-Freedom manipulator CT-Arm. Another is the gravitationally decoupled actuation (GDA). This is a design and control strategy to maximize energy efficiency of a robotic system by means of decoupled drive of the 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 three-dimensional terrain.