A new Input-Output qualitative notion, closely related to passivity, is introduced for general nonlinear systems with inputs and outputs and its usefulness in proving convergence in positive feedback interconnections is investigated. This property, roughly speaking, plays for positive feedback the natural counter-part of what passivity is for negative feedback interconnections.
On systems with counter-clock-wise Input/Output dynamics / Angeli, D. - CD-ROM. - (2004), pp. 2527-2532. (Intervento presentato al convegno IEEE Conference on Decision and Control) [10.1109/CDC.2004.1428820].