Circumventing Conceptual Flaws in Classical Interaction Control Strategies

This paper studies the problem of interaction control based on force and velocity measurements. Without restricting ourselves to fixed control structures such as admittance or impedance control, we consider the general topology of the problem. Adopting the idea of Youla-based 2DOF control, we reveal a generic control architecture that splits the problem into two independent parts: nominal admittance shaping and disturbance rejection. This pinpoints conceptual flaws in classical interaction control architectures and suggests a way to circumvent them. As a by-product, a complete and compact parameterization of all achievable admittances is derived. The potential of the proposed architecture for analysis and controller design is demonstrated and validated experimentally.