| Walking beam reheat furnace is a large multi-phase heat treatment equipment mainly used for the annealing process for slabs or billets in metallurgy field. It has lots of advantages such as flexible heating mode and no limits for billet size etc. With the improved requirements for hot milling product quality and more national policies being pushed out due to energy conversation and environment protection, higher demands are put forward concerning the combustion efficiency, temperature accuracy and pollutant emission for the furnace. Thus optimizing control technologies, ensuring the billet heating quality and cost saving have big significance during the furnace engineering design. A walking beam reheat furnace built in Ningxia zhongse group co., Ltd. is considered in the dissertation. The following work is investigated.1. A mathematical model of furnace temperature is built up. Using the practical engineering data, the model parameters are identified with transient response interpolation method. The model is tested and verified by comparing its output with the actural industrial data by Matlab software.2. Basing on the heat transfer mechanism in the furnace, the transient heat conduction equation for the billet is simplified. The model is discretized with finite element method. The temperature distribution inside a billet is computed and simulated.Its effectiveness is verified by the buried thermocouple test method. Then basing on the energy conservation law, a practical method is presented for optimizing the furnace gas setting trajectory when a billet top surface temperature curve is given. It can decrease temperature setting margin, save fuel consumption and reduce temperature deviation inside a billet.3. Considering the model parameter uncertainties, the H? robust stabilization for the system is researched. The Lyapunov stabilization theory and LMI method are used to deduce the robust stabilization conditions. The system performances are simulated and analyzed for the furnace model. The results can be used to predict the temperature performance when it has model parameter uncertainties and disturbance.4. Concerning thermocouple failure, a sensor fault mathematical model is given.Non-fragile fault-tolerant controller is designed considering system uncertainties and time-delayed characteristics. By choosing the proper Lyapunov-Krasovskii functional,sufficient conditions to guarantee such a system to have robust fault-tolerant capability and non-fragility are obtained. The effectiveness is verified by numerical simulation and engineering experiment.5. Considering external disturbance and sensor faults possibly existing in the furnace temperature system, the multi-state time-delay model is considered to design a robust guaranteed cost fault-tolerant controller. By using a new composite Lyapunov-Krasovskii functional and LMI method, the quadratic robust stabilization fault-tolerant law is obtained which can maintain the furnace temperature system certain performance and H? interference suppression capability. Moreover, a solving shceme for an optimal guaranteed cost fault-tolerant control law is given. The algorithm effectiveness is verified by numerical simulation and engineering experiment.6. In view of the combustion process, a programmable multi-phase pulse combustion controller is developed by software cooperating with regular combustion devices. It can replace the hardware pulse combustor and save cost. The corresponding burner working procedure in different flame sizes can be implemented automatically by the computed time series. Application effects show the new scheme can improve temperature accuracy and distribution uniformity. |
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