Valve-based Virtual Energy Tanks: A Framework to Simultaneously Passify Controls and Embed Control Objectives

In this paper, we show how virtual energy tanks can be used for passivity-based control schemes beyond ensuring passivity of the system, but respecting power-related control objectives. For this, we introduce the concept of valve-based virtual energy tanks. We show how these can be designed to handle several potentially non-passive ports based on their associated task priorities. Moreover, several practically useful policies are introduced for tank design. Finally, as a case study, a common potentially non-passive robotics system is elaborated to which a thorough passivity analysis as well as valve-based tank augmentation is applied. Several experiments with a force-impedance controlled robot in interaction with the environment underline the real world applicability of our approach.