Study On Drum Brake Fault Diagnosis Expert System Based On Fault Tree

The brake is the key component to achieve lift-car braking for the traction lift.In recent years,the lift-car cannot be braked sometimes because of the faults of brake,which does not only endanger the safety of passengers,but also create a negative effect on society.Although the General Administration of Quality Supervision(AQSIQ)has taken several actions to avoid these accidents,the problems still cannot be solved effectively.The reason lies that the performance of brake is dynamically changing.Additionally,most brakes made in China are imitated from foreign products,the dynamic characteristics and the fault mechanism of which are not well identified.Based on above reasons,there is lake of effective supervising and diagnosing online system used in brake,thus the reliable operation of brake cannot be guarantee relying on the supervision and inspection of maintenance personnel.To fill the gap,the drum brake is chosen as the study object in this paper,the dynamic characteristics and the fault mechanism of which are investigated deeply.Meanwhile,the deep knowledge of drum brake is obtained.In addition,the shallow knowledge of drum brake is collected from experts.A fault diagnosis expert system is established on this basis,which can be used for supervising the motion states of the drum brake and diagnosing the faults online.It is of great importance to improve the safety level of lift,shorten the maintenance time,and reduce the resources on maintenance.The research contents are as follows:The frame structure of the expert system is established according to the mission requirements.Then,the construction methods of the diagnostic knowledge base and the inference engine are established.The knowledge of drum brake can be obtained by collecting the shallow knowledge and analyzing the deep knowledge and can be expressed based on rules.The reasoning method based on rules and the control method based on data can be used in the inference engine.The static characteristic on the working state and the dynamic characteristics on the motion state are investigated through the analysis of the basic structure and working principle of the drum brake.On this basis,a series of mathematical models are established.Among them,the braking torque is characterized the braking performance,the pick-up time of movable iron core is characterized the releasing time of drum brake,the releasing time of movable iron core is characterized the braking time of drum brake.Meanwhile,the internal relations between the whole performance of drum brake and the parameters of its components are revealed.The fault modes and corresponding mechanism of the drum brake are researched.On this basis,five fault trees are established,including the insufficiency of the braking torque,the braking or releasing response time outs,and two situations that the brake cannot brake or release.Meanwhile,the logical relations between the operation state of drum brake and the fault modes of its components are revealed.Five major modules of the expert system are designed based on the knowledge obtained,including dynamic parameter acquisition module,diagnostic knowledge base,dynamic database,inference engine and man-machine interface.Then the test system of expert system is developed in MATLAB.And the feasibility of the test system is verified,the results show that the test system can well identify the fault modes and mechanism,and gives reasonable maintenance strategies.