Passivity Based Control

Passivity is a fundamental property of many physical systems which may be roughly defined in terms of energy dissipation and transformation. It is an inherent Input-Output property in the sense that it quantifies and qualifies the energy balance of a system when stimulated by external inputs to generate some output. Passivity is therefore related to the property of stability in an input-output sense, that is, we say that the system is stable if bounded “input energy” supplied to the system, yields bounded output energy. This is in contrast to Lyapunov stability which concerns the internal stability of a system, that is, how “far” the state of a system is from a desired value. In other words, how differently a system behaves with respect to a desired performance.