The Study On Model_Based Accident Alarm Method For Mechanical Devices

Mechanical devices are the important compose of Gross National Economy factors. "How to ensure the devices to work normally, prevent the fatal accident to happen and prolong their remain life time?is the important question for discussion in every countries. The accident alarm method for mechanical devices is studied in this paper. The key of reducing false alarm is selecting the sensitive characteristic parameter, detecting early symptom of fault in time, establishing reasonable alarm criterion, alarming at drawing near dangerous accident. In this paper, based on the analysis of the fault mechanism, the model of fault degradation and evolvement is found, and it is simulated and analyzed, thus, the sensitive parameters have been selected and alarm criterion has been established. The occuxrence of fault usually has complicated causality. In this paper, based on the analysis of the fault mechanism, the dynamic system is introduced to establish the cause and effect network map of single fault, confirm the structure of system, and establish the equation of system dynamic model. The simulation soft-ware STELLA is applied to simulate the system model, the dynamic behavior and characteristic of the system have been analyzed. The model of system dynamics is not susceptive to many parameters of the system, but it is susceptive to very few parameters. If these parameters have been changed, their effect will be spread quickly among the system. The sensitivities testing of system model includes changing parameters and changing initial value. By testing the model of system dynamics of the fault, the change of the system behavior indicates that which parameters are sensitive to the system model, accordingly, these parameters can be used for sensitive parameters of the fault alarm. Simulating the system model with the simulation software can describe the dynamic behavior of the system factors, forecast their developing trend, therefore, it reflects the actual state of the machine more truly and is propitious to establish the exact alarm criterion. Single parameter provides little message and sometimes it is difficult to make an exact evaluate. In this paper, by testing the sensitivity of the system model, three parameters are selected as sensitive parameters, and based on simulation result of the system model, three dimension failure surface is used for alarm criterion and arithmetic of the alarm is carried out. In this paper, system dynamics method is first applied to accident alarm for mechanical devices. The sliding bearing is chosen as the research object, and its system dynamics model of the heat plane and agglutination State are found. The three-dimension failure surface of temperature-verity-load is put forward as alarm criterion. With this method, the developing trend of fault can be forecasted truly, then the veracity of fault alarm can be improved.