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Modeling and Control of Hybrid Systems Including Multirate Sampling

Samadi, Sediqeh | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42892 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Bozorgmehry Boozarjomehry, Ramin
  7. Abstract:
  8. Whenever continuous and discrete dynamics interact, hybrid systems arise. Basically, models of such systems consisted of differential or difference equations to represent continuous dynamics and automata or other discrete variables to describe behavioral mode of the systems. Our main concern is focused on two types of hybrid systems: Discrete controllers which are combined with continuous physical process like biological systems can often be well described by hybrid systems. Our approach in this thesis deals with optimal multiple daily insulin injections which are introduced as an offline control approach on a simulated patient with type I diabetes. Simulated patient is provided via GlucoSim model. In this thesis, multrate daily insulin injections are proposed and the required amount of insulin in each injection is calculated by genetic algorithm optimization. It is implemented on the various conditions such as fixed or variable amount of carbohydrate intake in each meal, insulin type, variable number of daily insulin injections and various patients’ body weights. According to the simulation results, the simulated patient’s blood glucose concentration avoids from dangerous low/high levels. Hybrid systems are especially profound in some industrial processes such as hybrid batch chemical plants which are characterized by a sequence of modes. The investigating plant is made up of several parallel working batch reactors sharing common resources. Hybrid automaton formalism, one of the methods for hybrid system modeling, has been applied for this plant modeling. The model simulator is Matlab-simulink-Stateflow environment which is a very useful tool for the design of optimal and sub-optimal periodic schedules. The plant behavior is analyzed under periodic schedules in the case where there are disturbances on the plant parameters. Disturbances may cause a drift in the hybrid system trajectory which can either lead to a convergence to a new sub-optimal schedule or to a resource conflict. A control policy based on a model predictive control (MPC) approach is used to avoid resource conflicts. Basically, the strategy is the computation and the allocation of the stand by times on for the next reactor cycle
  9. Keywords:
  10. Predictive Control ; Hybrid System ; Multirate Sampling Time ; Chemical Plants ; Biological Systems

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