Dealing with network complexity in real-time networked control

Abstract

This paper addresses complex real-time networked control systems (NCSs). From our recent effort in this area, a general framework is developed to deal with network complexity. When the complex traffic of real-time NCSs are treated as stochastic and bounded variables, simplified yet improved methods for robust stability and control synthesis can be developed to guarantee the stability of the systems. From the perspective of network design, over-provisioning of network capacity is not a general solution as it cannot provide any guarantee for predictive communication behaviour, which is a basic requirement for many real-time applications. Co-design of network and control is an effective approach to simplify the network behaviour and consequently to maximize the performance of the overall NCSs. To implement such a co-design, a queuing protocol is applied to obtain predictable network traffic behaviour. Then, the predictable network-induced delay is compensated through the controller design, and any dropped control packet is also estimated in real-time using past control packets. In this way, the network-induced delay can be limited within a single control period, significantly simplifying the network complexity as well as system analysis and design.