Mechanical System Reliability Optimal Allocation Based On Dynamic Programming And Software Development

Mechanical systems reliability allocation is one of the most important parts of systems reliability design. It can guide the mechanical systems reliability design. Whichever reliability allocation method to be adopted, the purpose is to make the indexes of the system cost, weight, volume, and so on, as low as possible, when adopting the limit condition of the minimum system reliability, or is to make the system reliability as high as possible when adopting the limit conditions of the system cost, weight, volume, and so on. The process of the system reliability allocation is the process of the system reliability optimization substantially. This paper adopts a reliability allocation method which guarantees the minimum costs and the minimum system reliability. Then, the method is used for assigning the system reliability to each subsystem, then to each part.This paper describes the independent failure system reliability model, the dependent failure mechanisms and the dependent failure system reliability model(the load- strength interference model in system level). It analyses the principles of the system reliability allocation, and then modified and supplemented the principles of the dependent failure system reliability allocation. It expounds a reasonable cost function. The cost function quantifies the external impact factors of the system reliability optimal allocation. Using the system reliability model function, it quantifies the intrinsic impact factors of the system reliability optimal allocation. Then, it establishes the system reliability optimal allocation comprehensive basis based on these two factors. This paper adopts the dynamic programming algorithm to optimize the multi-objective variables, and then calculates the each unit reliability optimization value. Further, it optimizes the part reliability index in the strength distribution level based on the part load and strength variation coefficient, to achieve the full allocation. Due to the universality of the parts dependent failure, this paper focuses on analysis and research of the parts failure dependent system reliability optimal allocation. Based on the stress- strength interference model and the stress- strength interference model in system level, it takes the part mean strength as the optimization variable, and translates the problem of the part reliability value allocation into the programming problem of the part strength distribution. Thus, it can avoid the irrational results which arise from the system reliability optimal allocation under the independent failure assumption. The optimal results are more realistic and easier to design.This paper uses VC++6.0 to develop the corresponding mechanical system reliability optimal allocation software. The software includes the parameter input module, the reliability optimization module, results display module and the data storage module. It can achieve the reliability optimal allocation of the series system, parallel system, series-parallel system and parallel-series system.