Automated control of muffle furnace

Zahir Mujanović (2011) Automated control of muffle furnace. EngD thesis.

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Abstract

The thesis presents a solution for controlling the heating process of a muffle furnace. The solution consists of a control cabinet, which houses the physical elements required for controlling the furnace, a program which controls the heating process and a user interface for interaction. The thesis primarily focuses on the field of control theory, as it uses a PID controller, a common controller in the field of automation. For the purpose of determining the correct parameters of the controller I used the Ziegler-Nichols method on a model of the furnace. The control cabinet includes fuses, soft starters and similiar elements to allow the furnace and it's actuators to function safely and to protect them from unintended use. The control program runs on a Siemens programmable logic controller. It is written in Step 7 using ladder diagrams, and uses sensors to protect the furnace and it's environment, allows users to dynamically change the heating program and communicates with the PID controller. The user interface is robust and easy to use. The PID parameters and additional control algorithms are tuned in such a way that the difference between the setpoint and process value is generally less than 1 °C.

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