CompAct Arm™: a Compliant Manipulator with Intrinsic Variable Physical Damping

Humans exploit compliance in their biomechanical muscle-tendon-bone actuation structure to enable robust and safe interaction with the environment and utilize the elastic energy stored into muscles and tendons to obtain large energy efficiency or high output mechanical power peaks at their limbs. From the robotic/mechatronic point of view it is clear that emulating such a property in robotic actuation systems enables the achievement of performance which is not possible with classical stiff designs. In contrast to this, transmission compliance introduces some disadvantages as e.g. typically underdamped modes which reduce the achievable control bandwidth, stability margin and accuracy of the controlled system. These limitations are solved in mammalians by means of physical damping which clarifies why these biological systems are able of performing fast and smooth yet accurate motions in their limbs. This motivates this work which consists in the analysis and development of the CompActTM Arm, a novel compliant manipulator with intrinsic variable damping. This is probably the first robotic system to exhibit these diverse bio inspired characteristics. A motivation analysis is initially presented to show how the drawbacks introduced by compliance can be overcome by means of physical damping. The second part of the paper presents the mechatronic development of the robotic manipulator and preliminary experimental results.