Quantization Effect Analysis Of Digital Control System And Its Design Based On Cell Mapping

This thesis discusses the quantiation effect in digital control system and its finite-precise design problem. The quantization research is proposed with the coming into being of digital system, but most research and actual design just simply neglect the quantization effect. Recently, the networked control and full digital control becomes the main stream of control system design. This topic attracts more and more attentions again. This thesis investigates the impact of quantization effect to stability, controllability and other dynamical characteristics applying the cell mapping method. A new direct finite-precise design method is also proposed based on cell model.Our research is mainly concerned with the quantization effect in the interface of digital controller and plant. For example, the quantization arises due to the use of A/D and D/A converters, the siginal transmission via digital communication network, etc. The finite word length problem in digital controller is also briefly discussed.Building the model of quantization is the first step and key issue for quantization research. Different models will deduce different analysis and design method. Some representative models are introduced. Then we analysis the basic disadvantages of dominant perturbation model by some typical examples. We point out that the variable quantization/ discretization make most analytical methods unavailable. It's just the main difficult of quantization research. In this thesis, we don't slide over this basic problem and directly inspect the dynamics of discrete state space. Then the cell mapping model for quantization and related research method are introduced based on this principle.Some special quantization effect features the essential characterisitics of quantzation. A main principle to judge a quantization model is whether it could successfully explain these special phenomena. We detail how to describe the dynamics of quantized system based on cell mapping method and give the new explaination for some quantization effects. Then based on this description, we develop the evaluation method for stability, robustness, controllability of digital system.The following discussion is the design and synthesis part. For quantizion system, we need design the system considering the state and input quantization. Here a direct finite-precise design method is proposed based on cell method. This method takes full consideration for the state/input quantization. The linear and nonlinear system could be dealt with by the same way. This method treats the quantization as the precondition of design, but not the phenomena need to be mitigated. The software and hardware realization for this method are also detailed.Quantization also arises in system identification process. We mainly discuss the impact of quantization to identification experiment design and common identification methods. The identification of closed-loop system is also analyzed based on cell mapping model. Moreover, we also discuss the application of grey system theory in quantization research, mainly for quantization of controller itself.The last part of this thesis belongs to interdisciplinary research. We apply the theory and method in our paper to some hot topics. In fact, it's also the basic trend in control theory research area. Here we select two kinds of dynamical systems as our research object. The first is the climate modification system. We mainly analyze some climate modification methods in the view of control theory. Then for spider system of Internet search engine, a new crawl strategy is designed based on its cell mapping description.