Characterization of impedance rendering with a cable-driven agonist-antagonist haptic device

The majority of industrial robots come with position/velocity control architectures which allow precise positioning and accurate path-following, but they fail when performing contact tasks for finishing stages. To address this issue, impedance and force control have been proposed as an alternative to the position/velocity control paradigm. However, while the former requires torque control and hence cannot be applied to most of the position/velocity-based industrial robots, the latter comes with issues such as limited bandwidth and instability. A more recent approach consists of mounting an active pneumatic tool on the robot end-effector with the aim of regulating the contact force independently from the robot control architecture. Nevertheless, such active tools are bulky and hence require robots with high payload. In this paper we present a prototype of a novel agonist-antagonist (A-A) cable-driven active tool that is light-weight and it has been conceived to control the impedance at the contact interface. In order to estimate and analyze the bandwidth, the A-A system will reproduce the behavior of elastic band which have a perfect bandwidth with a known stiffness. Preliminary experiments and results are presented in order to evaluate the goodness of the rendered impedance.