There has been an increasing interest in the use of mechanical dynamics, (e.g., passive, elastic, and viscous dynamics) for energy efficient and agile control of robotic systems. Despite the impressive demonstrations of behavioural performance, the mechanical dynamics of this class of robotic systems is still very limited as compared to those of biological systems. For example, passive dynamic walkers are not capable of generating joint torques to compensate for disturbances from complex environments. In order to tackle such a discrepancy between biological and artificial systems, we present the concept and design of an adaptive clutch mechanism that discretely covers the full-range of dynamics. As a result, the system is capable of a large variety of joint operations, including dynamic switching among passive, actuated and rigid modes. The main innovation of this paper is the framework and algorithm developed for controlling the trajectory of such joint. We present different control strategies that exploit passive dynamics. Simulation results demonstrate a significant improvement in motion control with respect to the speed of motion and energy efficiency. The actuator is implemented in a simple pendulum platform to quantitatively evaluate this novel approach.
