Performance oriented control over networks - Switching controllers and switched time delay

The stability and performance of a networked control system (NCS) strongly depends on the communication quality, e.g. of the communication time delay. Aiming at performance oriented control over networks in the presence of piecewise constant time delay, two novel control approaches are investigated. In the first approach, the time delay is monitored and an appropriate controller is selected. The second approach is based on the Quality-of-Service communication concept, where the time delay is adjustable and related to the network cost. Aiming at an optimal trade-off between network cost and control performance the controller together with the time delay is switched. Both approaches result in a switched system with switched (piecewise constant) delays. Sufficient stability conditions for the resulting switched time delay system are presented using a piecewise continuous Lyapunov-Razumikhin function. A common Lyapunov function is derived for linear time-invariant symmetric subsystems. The performance benefits for both approaches are demonstrated in numerical examples.