Research On Fault-tolerant Technology For Advanced Programmable Control Systems

Fault-tolerant control has opened up a new path for raising reliability of complex systems, and the fault-tolerant controller has become the key safety-component in industrial areas, including oil, chemistry, power and metallurgy. At present, the triple-modular redundant fault-tolerant controller, which owns the function of redundancy, is designed for industrial control system. The controller is mainly used in emergency shutdown system, safety interlock system and other applications. In our country, technologies and researches in this field are still inadequate, compared to advanced ones in developed countries. Therefore, it has practical significance to develop the safety controller with the function of redundancy for achieving the industrial automation as well as the localization of equipment.As the leading-edge products, programmable automation controllers(PAC) have excellent performance, which can be applied as hardware platform to realize redundant and fault-tolerant control. In addition, the ability to tolerate faults for controllers can be achieved by voting redundant logic algorithm. This means voting algorithm is the major one in fault-tolerant control, and also the key factor in reliability of controller systems. In this paper, based on introducing the structure of triple-modular redundant controller, it discusses fault-tolerant mechanism and focuses on the influence of fault types and system performance for different voting algorithm. According to the voting mechanism of double2-out-of-2,2-out-of-3, and3-out-of-4redundant structures, the thesis lists all the combinations of fault possibilities and utilizes the Markov model to establish the system status switching graph. With the help of solving the matrix equation and MATLAB Simulation program, the influence of parameters as failure rate, failure detection coverage rate and maintenance rate on system reliability and safety is studied. As a result, it suggests that the research charts can be used as reference or scheme for designing different redundant structures in automation systems.At the end of this paper, a triple-bus structure of triple-modular redundant system is designed, aiming to data synchronization and the function of2-out-of-3voting. At the same time, triple-modular redundant signal acquisition model and logic signal model of3-out-of-4redundant structure are built by using embedded control system software to realize simple signal processing and fault-tolerant voting, preparing for developing the software running platform of triple-modular redundant system later.