PID Controller Design in Networked Control Systems

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Helsinki University of Technology | Diplomityö
Degree programme
79 s. + liitt.
Networked control systems (NCS) and sensor networks, where the process and the controller are separated by a network, are discussed in this thesis and new problems in control are pointed out. Traditional tuning methods can not handle the varying time-delay in NCS. New controller tuning techniques are needed. The thesis consists of two parts: 1) Discrete-time PID controller tuning for varying time-delay systems, including NCS, and 2) development of the MoCoNet system. The controller design in the thesis focuses on an optimisation by simulation tuning technique. The tuning is tested with the MoCoNet system. The MoCoNet system enables students to conduct remote laboratory experiments over the Internet. The interface is an applet and can be run with any Java enabled browser. The MoCoNet system supports rapid control prototyping, where controllers built with MATLAB/Simulink can be easily tested on a .real process. With a network simulator control design of NCS can be investigated in the MoCoNet system with a real process. The other part of the thesis takes advantage of this feature. Optimal PID tuning results are presented for a general process model in different cases of constant, state- and time-dependent or random delays. The results are displayed as functions of process time constant and controller sampling time. A discrete-time PID controller is tuned for an example process and the tuning is verified with the MoCoNet system. The optimisation tuning is shown to perform better, both in simulations and in practice with runs on the MoCoNet system, than other traditional tuning methods investigated in the thesis.
Koivo, Heikki
Thesis advisor
Eriksson, Lasse
networked control systems, styrsystem över nätverk, discrete-time PID controller, diskret-tid PID regulator, tuning, justering, varying time-delay, varierande tidstördröjning, remote laboratory, fjärrlaboratorium
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