Research On Electrostatic Integrated Monitoring Technique For Wear Condition Of Gear Drives

As one of the key components in machinery and equipment,gear transmission system is important to transmit power which always need to continuous operate under the condition of high speed and heavy load in industry.The performance degradation or failure of the system will affect the condition of the whole machine and even lead to the unplanned shutdown,which will make for economic losses or even heavy casualties.The failure rate is relatively high and the friction/wear is one of the main factors leads to these serious faults.The existing regular monitoring techniques such as vibration and temperature can detect the server faults such as surface cracks,spalling and tooth break etc.While the time from fault symptoms to the final failure is relatively short which makes it difficult to have sufficient time establishing suitable maintenance strategies,also the abominable working conditions will greatly reduce the capability of fault detection.In view of the drawbacks of the situation,the novel electrostatic monitoring technique is worth investigating in order to have a better condition monitoring.The researches in modeling,simulation,calibration of the electrostatic sensor and feature extraction,parameters fusion of the electrostatic signal combined with the characters of the gear transmission system,supporting software and hardware equipment design and construction with actual engineering experiments have important reference values and guiding significances for the improvement of condition monitoring in mechanical systems.The main contents of this thesis are as follows:(1)The electrostatic charging mechanisms of mechanical friction and wear are summarized with five origins: tribocharging,triboemission,triboelectrification,surface charging and debris charging.The electrostatic sensing principles and two basic electrostatic sensors,oil-line sensor and wear-site sensor,are introduced.The researches of the technique directions,application areas,advantages and characteristics are analyzed in details.(2)With the special electrostatic monitoring mechanisms,it is difficult to describe and measure the characters of the electrostatic sensors.New mathematical models are established for both OLS and WSS,and a series of suitable parameters are offered to indicate the electrostatic sensor characteristics.On the basis of induction simulation,the change principles and factors are plotted and pointed out,which provides the basis for accurate description and experimental verification of the performance for the electrostatic sensor.(3)An essential sensor calibration rig and an effective validation method are need to calibrate the electrostatic sensor.The rig is designed and established to make a series of calibration tests with several manufactured electrostatic sensors.The results show a good accordance with theoretical simulations which validate both the correctness of the established mathematical model and simulation results,and more informations were calculated.The origin calibration work for existing electrostatic sensors are completed which offers a good reference to the following sensor design and optimization.(4)An effective way to improve the accuracy and reliability of condition monitoring is to use more sensors with integrated methods.On the basis of feature extraction with time domain and complexity measure methods,a suitable algorithm called 'moving window local outlier factor' with multi-condition time variation considered is applied to the multi-sensor of electrostatic signals.It is validated through the modified rolling bearing and pin-on-disk electrostatic integrated monitoring platforms.The experiment results show a good applicability and effectiveness of the fusion method for electrostatic integrated monitoring.(5)The comprehensive electrostatic monitoring software system and hardware equipment are the premise for the actual application of the gear drives and mechanical tribological systems.A suitable framework of the hardware equipment based on the NI PXI system is established,while a software called 'Gear-Driven Health Electrostatic Monitoring System' shorten for GDHEMS is developed.The detailed equipments which are used and the function of the software modules are introduced and analyzed.The system accomplishes the comprehension of three parts i.e.gear drives,electrostatic monitoring and data processing.(6)The ultimate aim of these researches is to make the technique applied in the actual industrial manufacture.Basing on the series of previous investigations,the electrostatic integrated monitoring system is equipped on the actual rail transport vehicle gear transmission system and wind turbine gear transmission system.According to the experimental processes and procedures,the experiments were taken through the load fatigue test,accelerated life test and failure test respectively.The feasibility and accuracy of the electrostatic integrated monitoring for gear drives are validated successfully.