Research On Performance Degradation Assessment And Fault Diagnosis Method Of Mine Hoist Brake System

In the process of mining production,hoist is responsible for transporting personnel,equipment,coal and all kinds of materials.It is an important link between the whole production system above ground and underground.As an indispensable and important part of hoist,braking system is the safety guarantee for stable and efficient operation of hoist,and plays an important role in mining production system.If the brake system of hoist breaks down,the production efficiency will be affected slightly,resulting in economic losses,and the casualties will be caused seriously,affecting social harmony and stability.Therefore,it is very important to evaluate the performance degradation and fault diagnosis of hoist brake system to ensure the safety,stability and efficiency of hoist operation,both in theory and in practice.At present,the maintenance of brake system failure of mine hoist still adopts the traditional periodic maintenance mode,which is increasingly unable to meet the needs of modern development of mining enterprises for upgrading equipment management level.Intelligent maintenance based on active maintenance is an inevitable trend to improve the efficiency of equipment maintenance and enhance the efficiency of enterprises.Performance degradation assessment and fault diagnosis is an important part of intelligent maintenance,which is one of the research focuses of our group.One of the key points and difficulties of this research is performance degradation and fault related data acquisition,so a brake system simulation platform is built to solve this problem.On the basis of summarizing the related research theory and technology application status at home and abroad,this paper uses dynamic analysis to establish mathematical models,build a simulation platform to simulate system faults,and research on performance degradation and fault diagnosis of brake system by combining simulation and experimental verification.The specific research work is as follows:Firstly,based on the dynamic analysis of the braking system,the mathematical model of the main components of the braking system is established.The dynamic analysis of brake and hoist constant deceleration brake is carried out,the state equation of brake and the mathematical model for calculating deceleration of hoist are established.The mechanical analysis of electromagnetic proportional directional valve,the core hydraulic component of constant deceleration brake system,the flow balance equation and force balance equation are listed,and the transfer function of voltage and displacement of electro-hydraulic proportional directional valve is obtained.Each orifice of proportional directional valve is regarded as a variable non-linear damper,and the mathematical model of displacement and flow of valve core is obtained by using flow equation.The distribution parameter model of pipeline is analyzed,and the approximate model of Tirkha first-order inertia is selected to approximate the series impedance,and the hyperbolic function is calculated according to the series expansion of infinite product of hyperbolic function proposed by Oldenburger.According to the mathematical model of proportional directional valve,the mathematical model of proportional directional valve controlling brake and the mathematical model of hoist deceleration,the transfer function of constant deceleration brake system is obtained.Secondly,a simulation platform of constant deceleration braking system based on Simulink is built.The E141A constant deceleration braking system of JKMD4.5*4 mine hoist is selected as the research object,and the simulation platform of constant deceleration braking system is built based on the modeling idea of nodal chamber method.The reliability of the simulation platform is verified by comparing the theoretical calculation with the simulation results of constant deceleration braking.The dynamic characteristics of the braking system during braking process,such as system pressure,hoist deceleration and opening clearance,are studied by using the simulation platform.The typical performance degradation of the braking system,such as the reduction of spring stiffness,the decrease of friction coefficient of brake shoe and the entry of hydraulic oil into air,is simulated.The simulation analysis of typical performance degradation shows that when the performance of main components decreases,it will not cause the braking system failure immediately,but the system performance degradation.These degradation manifests as the system pressure decreases,the opening clearance increases,and the closing time becomes longer when the braking system constant deceleration braking;when the system performance decreases to a certain extent,it will show that the braking deceleration does not meet the requirements.The pressure-time curve of the brake system during constant deceleration braking contains abundant information of operation status,which can be used as a characterization parameter of performance degradation and fault of the brake system to extract characteristic parameters for performance degradation assessment and fault diagnosis of the brake system as a whole.Thirdly,the performance degradation evaluation method of braking system based on safety braking test is proposed.Based on the simulation data of the simulation platform,the extraction and selection methods of characteristic parameters are studied to obtain the characteristic vectors of performance degradation assessment with high sensitivity.The complex wavelet kernel function based on wavelet theory can approximate any interface in the feature space,with high evaluation accuracy,and the variable step size Fruit Fly optimization algorithm has fast optimization speed and can effectively avoid falling into a trap.The performance evaluation model of VSFOA-CGWSVDD braking system is constructed,and the performance score is defined as the performance degradation measurement index.In order to make the research method carry out the engineering transformation smoothly,the safety braking test is first proposed and defined.The safety braking test is a feasible alternatives for performance test of the braking system stipulated in Coal Mine Safety Regulation.The performance degradation degree of brake system is regularly detected by using VSFOA-CGWSVDD performance degradation model.A fault diagnosis method for braking system based on BP neural network with feature selection is proposed.Firstly,29 feature parameters,such as percentile,mean,kurtosis factor and energy entropy,are extracted from the pressure-time curve of safety braking test to form an alternative feature set.Then,based on the average distance between classes,the comprehensive distance between classes and within classes,and Fisher score,data variance and correlation coefficient are used to synthetically evaluate the characteristic parameters.The fault sensitive characteristic parameters are selected.After the dimensionality reduction of principal component features,the feature vectors of fault diagnosis are formed.Finally,the BP neural network is used for fault diagnosis.The reliability of the proposed method is verified by simulation and experimental data.A performance degradation assessment method of TLFCA-BPNN braking system based on multi-sensor monitoring data is proposed,which realizes real-time performance degradation assessment of braking system.The multi-time point data of single sensor is used for time fusion and multi-sensor data is used for space fusion.According to the structure of the braking system and the function of each sensor,factors are divided into domains.According to the degree of performance degradation,evaluation sets are set up.Combining the methods of fuzzy mathematics,subjective and objective weight determination,comprehensive evaluation and artificial neural network,the performance degradation state of the braking system is finally obtained.The performance index is in the range of[0,1].1 indicates that the performance is good,the equipment operates in the optimum condition.0 indicates that the performance is seriously degraded,reaching the limit value stipulated in the "Coal Mine Safety Regulations",and equipment needs to be stopped and repaired immediately.Through the comprehensive evaluation of monitoring data of various sensors,the multi-dimensional operation status information of the equipment is transformed into the performance degradation index of the braking system,which is helpful for operators and managers to know the degradation degree of the equipment performance in time.It is helpful for making scientific and effective maintenance decision and provide technical support for intelligent maintenance of brake system.Finally,the brake system management platform is developed.The hardware of the upper integrated machine,gate detection box,hydraulic station control module and other platforms are developed.The management platform of performance degradation assessment and fault diagnosis method of the braking system is developed based on Lab VIEW platform software.Real-time dynamic monitoring of important parameters of braking system and fault alarm are realized,performance degradation assessment of braking system based on condition monitoring data,periodic performance degradation assessment and fault diagnosis of braking system based on safety braking test data,modification and fault reset of some specific parameters in braking system,and check fault records and historical data.Industrial tests were carried out on the elevator test bench to verify the feasibility of the safety braking test scheme,as well as the validity and feasibility of the methods described above.In summary,the research on performance degradation assessment and fault diagnosis method of hoist brake system can not only grasp the degradation degree of brake system performance in time,but also analyze the cause and severity of performance degradation through fault diagnosis.This research is of great significance to ensure the safe and efficient operation of brake system and realize intelligent maintenance.