I²mpedance - A Passivity Based Integrative Impedance Controller for Precise and Compliant Manipulation and Interaction

Abstract

Sophisticated manipulation requires both compliance and accuracy. While tactile robots excel at being compliant, their accuracy is often inadequate for complex manipulation. Contact-rich assembly tasks, such as the insertion and manipulation of objects with small tolerances pose an enormous challenge. Complex, highly integrated assemblies, especially in high-tech areas such as robotics, sensors, or machines, still require human personnel, as they cannot be automated in a satisfactory way. To automate such tasks, especially in the context of labor shortage and Industry 4.0, these limitations must be overcome. Robots need to guarantee force limits for active environments in order to avoid harm or damage. Therefore, in this work, we adapt standard Cartesian impedance control by introducing an integration term for position accuracy and wrench limits for safe compliant interaction with unknown and active environments. We combine this with a virtual energy tank to guarantee the general passivity of the controller. Our controller is benchmarked against standard impedance control for absolute positioning accuracy across the robot workspace. Furthermore, we show its applicability to an industrial insertion task. We demonstrate absolute positioning accuracy (residual error| Ax| < 4e – 4) comparable to rigid robots while preserving compliant behavior.