Design of the networked predictive control method for wired and wireless networked systems

The closed-loop control of processes over networks has in recent years become an increasingly popular research topic. This is a very viable solution for a wide variety of applications due to the rapid developments in communication network technologies and the widespread expansion of network devices and users. The convergence of communication networks technologies and advanced control methods do have a great potential to replace traditional control systems. The research programme presented in this thesis led to a development of networked predictive control algorithms over wired local area networks, general packet radio service wireless networks and wireless local area networks. Since the network is taken as a part of a control system, the network-induced time delay and data dropout are unavoidable. How to compensate for these issues is the main challenge in designing control methodologies for networked control systems. Five solutions were presented in this thesis to address these problems and were termed as recursive predictive control method I, inner loop predictive control method, outer loop predictive control method, modified generalised predictive control method and recursive predictive control method II. Irrespective of the different implementations of the networked control methods used, there is a common structure for each method which consists of a predictive control generator, a network delay compensator, a buffer and a plant output predictor. The predictive control generator and network delay compensator were used to compensate for the network delay and data dropout in the forward channel. The network delay and data dropout in the feedback channel was compensated for by using the plant output predictor, buffer and network delay compensator. The relationship between the sampling rate, packet size, network delay and data dropout were examined by using a round trip time delay method. Two network delay measurement methods were also presented and analysed in this thesis. The results of the real-time measurement of the network delay were used in an offline simulation. A networked servo system was built to test the system performance for an approximately linear, open-loop stable system and a networked inverted pendulum system was used to illustrate the system performance for an open-loop unstable system. The stability of each method was also considered. In order to simplify the software development, the Matlab/Simulink/Real-time workshop integrated development suit was used in the practical control system. The simulation block diagram in the Simulink environment was translated to the standard C language by using the real-time workshop. The ARMLINUX-GCC 3.4.4 was used to compile the generated C language file into the executable file running on an embedded board. In order to monitor the status of the control system and change the parameters of the controller, a network-based supervisory program was also developed using Microsoft Visual C++ 6.0.