| Thanks to the development of the Internet of Things technology,the smart home system has become the most fashionable life concept.The smart home system involves a lot of information processing and control.To ensure that the system’s function is in the optimal state and can quickly respond to the user’s dynamic power demand,the reliability modeling and analysis of the smart home system are essential steps in the process of reliability design.With the integration of informatization and industrialization,intelligent machinery has become the mechanical field trend.This thesis takes the smart home system as the research object,but the combined analysis method proposed is also applicable to the reliability assessment of the intelligent mechanical systems.This thesis conducts a hierarchical reliability analysis of the smart home system,including physical layer modeling and analysis that consider multi-stage task dynamic behavior,backup redundancy and functional dependence,and network layer modeling and analysis that consider failure propagation time and effects of competition failures.The validity of the method is verified by numerical simulation.The specific research content is as follows:(1)Physical layer reliability: The difficulty of physical layer reliability modeling is to address the dynamic behaviors of the physical subsystem,such as phased task behavior caused by environmental changes,backup redundancy,and functional dependence.This work expands the general combinatorial method: divide the physical level into static modules and dynamic modules,and use the multi-value decision graph method and continuous-time Markov method to solve the reliability problem of the static and dynamic modules,respectively.On this basis,integration of module reliabilities is performed to obtain the reliability of the entire physical level.(2)Communication layered reliability: The communication layer is a wireless network composed of sensors,relay nodes.In the system undergoing the functional dependence behaviors,competitions exist in the time domain between the failure isolation of corresponding dependent components and the failure propagation effect of trigger.This thesis establishes the reliability analysis model of probabilistic competitive failure by considering the failure propagation time and isolation factors.The accuracy of the method is verified by comparing it with the Monte Carlo simulation results.(3)The reliability optimization of the smart home system physical layer and communication layer is studied considering selecting different component suppliers.Three types of optimization problems are considered: system reliability maximization with constraints;System reliability maximization under cost constraints,System cost minimization under reliability constraints.Through numerical simulation,it is proved that different component combinations can achieve the optimal balance between system cost and reliability.It has positive guiding significance to actual production. |
