Theoretical Analysis And Application Of Manufacturing System Brittleness

Nowadays,the manufacturing system has become increasingly complex,precise,large-scale,automatic and flexible.In addition,the system is subject to complex,changeable and uncertain internal and external interference in the operation process,which makes the probability of failure of the manufacturing system higher and higher.Often a small disturbance will lead to the collapse of the whole system,which will cause serious consequences.Therefore,how to ensure the operation safety of manufacturing system is the focus of manufacturing enterprises.Brittleness is the inherent property of manufacturing system.Once the brittleness of the system is excited,the system will collapse.In-depth study of manufacturing system brittleness is of great practical significance to ensure the safety of system operation,and also expands a new vision for the research of safe operation of manufacturing system.Taking the workshop-level manufacturing system as the research object,and based on the existing research results related to brittleness of other complex systems,this paper defines the definition and characteristics of manufacturing system brittleness,and expounds in detail the structure model,stimulated mechanism and propagation model of manufacturing system brittleness.Meanwhile,based on the relevant research theories,the framework of manufacturing system brittleness analysis is formed,and the problems of the modeling of manufacturing system brittleness,evaluation of brittleness,identification of key brittleness factor,health assessment and maintenance strategy optimization based on brittleness are systematically studied,which provides new ideas and theoretical support for the safe operation of manufacturing system.The specific research content of this paper includes the following aspects:(1)This paper discusses the research status and existing problems in the research fields of other complex system brittleness,manufacturing system brittleness,health evaluation of manufacturing system,the maintenance strategy optimization of manufacturing system.Based on the existing complex system brittleness theory,the definition and characteristics of manufacturing system brittleness are clarified,and the structure model,stimulated mechanism and propagation model of manufacturing system brittleness are deeply studied.Combined with the main research contents of this paper,the research framework of manufacturing system brittleness is formed.(2)Aiming at the problem that it is difficult to identify the key brittleness factors of manufacturing system,a key brittleness factor identification method of manufacturing system based on interpretative structural modeling(ISM)and complex network is proposed.Firstly,in view of the 5M1 E analysis method(man,machine,material,method,environment and measure),the factors affecting the brittleness of the system are summarized and extracted through expert screening,and the correlation between brittleness factors is determined.Based on the complex network theory,the complex network model of manufacturing system brittleness factor is constructed,and from the perspective of node itself,the important network characteristic parameters of nodes in complex networks are analyzed.Secondly,based on ISM theory,the complex network is divided into levels,the hierarchical structure relationship of each node in the whole network is clarified,and the hierarchical digraph of network based on ISM is drawn.Thirdly,the key nodes of directed complex network are identified and analyzed based on ISM model,and a calculation method of comprehensive value of node importance for directed complex network is proposed.The node importance is analyzed from the perspectives of node local and network global,and the key brittleness factors in manufacturing system are identified.Finally,an example is given to verify the effectiveness of the proposed method.(3)Aiming at the problem that it is difficult to quantitatively evaluate the brittleness of manufacturing system,through the combination of polymorphism theory and brittleness theory,the brittle risk entropy measurement model of equipment and the calculation model of system brittleness are constructed from equipment layer to system layer,which effectively completes the quantitative measurement of manufacturing system brittleness.Firstly,By establishing the mapping relationship between performance parameters and equipment performance state,various performance states of equipment are divided,and the probability of equipment state is determined in real time according to the division of equipment performance state,which makes up for the deficiency that the traditional method is often based on obeying a specific random distribution process assumption when calculating the probability value of equipment state.Secondly,constructing the equipment brittleness risk entropy measurement model from the two aspects : the probability of the equipment state and the impact of the state on the equipment itself,and then completes the brittleness measurement in the process of equipment operation.Thirdly,based on the system equivalent division principle and the brittleness calculation principle of series-parallel equipment,the system brittleness calculation model is constructed to measure and analyze the brittleness in the operation process of the manufacturing system.Finally,a practical engineering case is used to verify the effectiveness of the proposed model and method.(4)Aiming at the randomness and fuzziness in the process of manufacturing system health status evaluation,a new method of manufacturing system health status evaluation based on brittleness and cloud model is proposed.Firstly,Based on the construction principles and methods of health status evaluation index,and combined with the actual system station layout and data collection of each station,an evaluation index system representing the health status of the system is constructed.Secondly,according to the health status evaluation index system,the level of system health status is effectively divided by using brittleness,and then a cloud center of gravity evaluation method based on cloud theory is proposed to effectively evaluate the health status of the system.Thirdly,combined with the theory of brittleness and polymorphism,based on the above system brittleness calculation model,the above evaluation results are verified and analyzed according to the real-time brittleness value of the system.Finally,the correctness and effectiveness of the method are verified by a specific practical case.(5)Aiming at the problems of unreasonable selection of maintenance measures and high maintenance cost,a maintenance strategy optimization method of manufacturing system combined brittleness theory with condition-based maintenance is proposed.Firstly,according to the deterioration process and state evolution relationship model of equipment,a health state prediction method of equipment based on brittleness is proposed.From the perspective of brittleness,based on historical and measured data,a support vector machine regression prediction model is constructed to predict the brittleness value and health state of equipment at a certain time in the future.Secondly,aiming at minimizing the total maintenance cost,a maintenance decision model is established based on the equipment health state.By solving the model,the optimal maintenance measures corresponding to each health state of the equipment under the minimization of the total maintenance cost are sought.Finally,the effectiveness of the proposed method is verified by an actual case.