Networked Control Systems with Time-Varying Delay – Stability through Input-Output Transformation (Netzwerkregelungssysteme mit variabler Totzeit – Stabilität durch Eingangs-Ausgangs-Transformation)

Abstract

With the increasing complexity of modern automation systems, Networked Control Systems (NCS) gain more and more importance due to their modularity and simplified diagnosis. In NCS, plant and controller are spatially separated and the control loop is physically closed through a communication network. Communication time delay in a NCS degrades the performance and may lead to instability. In this article we propose a novel approach for time-varying delay applicable to the class of input-feedforward-output-feedback-passive (IF-OFP) systems. The proposed approach is based on an input-output transformation; instead of direct communication a linear transformation of the plant and controller input and output is sent through the communication network. Asymptotic stability is guaranteed for arbirarily large time delay with bounded rate of change. The control performance is superior compared to alternative approaches. Simulations show the validity of the proposed approach.