Event-based control with communication delays and packet losses

Event-based control aims at reducing the information exchange over the communication network in feedback-control systems. This article extends a state-feedback approach to event-based control to cope with communication delays and packet losses in the feedback link. The main result is a bound for the maximum tolerable communication delay, which guarantees that the event-based state-feedback loop is stable in the sense that its state remains in a bounded surrounding of the state of a continuous-time state-feedback loop. This result is extended to communication links with additional packet losses. Simulation studies and experimental results illustrate the performance of the event-based control loop.     

Reconfigurable control of piecewise affine systems with actuator and sensor faults: Stability and tracking

A reconfigurable control approach for continuous-time piecewise affine (PWA) systems subject to actuator and sensor faults is presented. The approach extends the concept of virtual actuators and virtual sensors from linear to PWA systems on the basis of the fault-hiding principle that provides the underlying conceptual idea: the fault is hidden from the nominal controller and the fault effects are compensated. Sufficient linear matrix inequality (LMI) conditions for the existence of virtual actuators and virtual sensors are given that guarantee the recovery of closed-loop stability and the tracking of constant reference inputs. Since LMIs are efficiently solvable, this solution leads to a tractable computational algorithm that solves the reconfiguration problem. The approach is proven to be robust against model uncertainties and inaccurate fault diagnosis, and is evaluated using an example system of interconnected tanks.     

On the stability of qualitative models

This paper considers a discrete-time continuous-variable autonomous system for which only a quantised state measurement [x(k)] is available. The qualitative model of this system is a nondeterministic automaton thay describes, for a given quantised initial state [x(0)], the sequence of quantised states [x(k)]. The paper deals with the question for which stable linear systems is the qualitative model also stable. A necessary and sufficient condition on the qualitative model is proved under which the continuous-variable system is stable. This condition refers to the eventual boundedness of the nondeterministic automation. An example demonstrates that this stability criterion can be used only if a qualitative model of the system is available.