| The purpose of this thesis is to analyze the PLC software redundant design in a vast lab environmental control engineering. On the base of reliability theory and the actual experiences in project about a vast lab environmental automatic control system, the redundant hardware-architectures of control system is designed; the software redundant programme is achieved. Through debugging the redundant programme in the site and stimulating,running and analyzing about the performance parameters of control system,the conclusion that the reliability and availability ratio of system can be enhanced obviously by PLC software redundant design is drawn.First of all,in the thesis, introduce the application meaning of PLC redundant design and its development status both in domestic and abroad. Second, discuss demand analysis about vast lab environmental control system and according to that to choose the design platform of control system. Third, based on the S7-300PLC design platform of SIEMENS company, design the redundant hardware architectures of the system and realize the software redundant program. At last, analyze the working performance of system.focus on the analysis of the reliability and availability ratio of control engineering.It is inevitable that the redundant design increases units in system, This often makes system more complex and brings about cost rise, but the system performance in reliability and stead availability are enhanced dramatically. In many applications which are not restricted to switch time (usually below millsecond), the PLC design of software redundancy is capable of optimizing performance and reducing efficiently the partial redundant units, through which significant economic benefit can be obtained. |
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