Research On The Dynamic Reliability Modeling Theory And Simulation For Construction Equipment's Hydraulic System

As a graphical and mathematical modeling tool, Petri net has become a powerful tool for modeling and simulation. Using the Petri net, system structure and behavior can be described commendably. Due to these points, applying Petri net to system reliability analysis has become research hotspot in this field. In this paper, the methods of system dynamic reliability modeling and their application in construction machinery hydraulic system are researched. The main contributions of this thesis are as follows:1. The definition and the main modeling methods of dynamic reliability are summarized. The modeling elements, processes and typical application of these methods are illuminated. It provides a favorable groundwork for the following research.2. Considering the advantages of Petri net and actual needs of system failure analysis, an advanced form of Petri net—Fault Petri net is put forward. Taking the case of digging machine's hydraulic system, the Fault Petri net model is constructed based on the system failure ratiocination. Compared with the traditional FTA, Fault Petri nets can express the logic relation and transform process in a more concise and compact way. At the same time, the numerical calculation for system reliability based on Fault Petri net is more convenient.3. In order to describe the dynamic behavior in hydraulic system, the General Stochastic Petri net (GSPN) is applied to dynamic reliability modeling in respect that the process of failure and repair can be simulated by the timed transition. Furthermore, the reliability model of typical repairable system and their state transfer matrix are presented.4. Aiming at the state space explosion problem in the actual application, a new method which combines the Fault Petri net and GSPN is put forward to analyze system dynamic reliability based on the modularization concept. An example is given to demonstrate that the new method can minish the state-space of GSPN to a considerable degree and provides an available way for the complicated system reliability analysis.5. Monte Carlo simulation can effectively solve the GSPN model which includes the non-exponentially distributed transition. The key points of Monte Carlo simulation in reliability index computing for GSPN model are discussed in detail.6. Based on the modeling theory of GSPN, the PetriTool software package which is used to simulate and analyze system reliability is developed. PetriTool provides a perfect virtual-reliability environment for system reliability analysis. The development steps and function modules of PetriTool are introduced briefly. Finally, the reliability model of the digging machine's hydraulic system is constructed with Petri net and simulated by PetriTool.