Research On The Piezoelectric Sensors Array Based Aircraft Structural Health Monitoring And Management System

Aircraft structural health monitoring and management (PHM) technology is a key component ofaircraft PHM system, which has been the core technology for advanced aircraft to realizeself-maintenance. It utilizes sensors and monitoring equipments to monitor and evaluate the healthstatus of the aircraft structure and estimate the remaining life, so as to guide the task decision andlogistics maintenance to ensure the application of new materials and reduce maintenance costs. Theconfiguration of the technology has become one of the hallmarks of advanced aircraft. Theengineering applications of the technology is urgently needed in the large civil aircraft, advancedcombat aircraft being developed in our country as well as in-service aircraft.Piezoelectric sensors array based aircraft structural health monitoring and management(Piezoelectric structural PHM) method is of structure modeling independent, regional monitoringfeatures and it is suitable for composite and metal structure. Therefore it has become an importantresearch direction of current aircraft structural PHM technology. For aviation engineering applications,this dissertation focuses on the key technical issues of piezoelectric structural PHM method and theestablishment of aircraft structural PHM system architecture. The main researches and innovation areas follows.1) On research of health monitoring theory of aircraft complex structure, two issues are studiedfor reliable monitoring of the health status of aircraft complex structures and composite structures.Firstly, on the signal processing method, the continuous Shannon complex wavelet transform isproposed to apply its feature of equal amplitude and frequency window to extract the narrow bandsignal and single frequency signal of Lamb wave signal and to calculate the group and phasevelocities of Lamb wave. This avoids the damage and the impact localization error caused by thegroup and phase velocity differences of different frequency signals and solves the problem ofextracting the narrow band signal from the wide band signal caused by impact. Secendly, on thedamage and impact monitoring method, a phase synthesis time reversal focusing method of Lambwave response signal acquired by piezoelectric sensors array is proposed by using group and phasevelocities. It uses group velocity to realize the phase synthesis in time domain and phase velocity torealize the phase synthesis in frequency domain, so as to realize the imaging and localization ofdamage and impact. This method solves the problem that conventional methods depend on structuraltransfer function and is easy to engineering applications. Based on this method, a phase synthesis time reversal focusing baseline free damage imaging and localization method is proposed.2) On piezoelectric structural PHM sensors and systems integration, only a few researches arecurrently applied on the design methods and development of piezoelectric structural PHM sensorswith the engineering applicability of aviation field. Research on the piezoelectric structural PHMsystem integration method and system development is still blank. Two issues are studied to addressthese problems. Firstly, A reliability design method of piezoelectric smart layer is proposed based onhybrid technology of welding and bonding, rigid-flexible combination and line spacing against theelectromagnetic interference is proposed. Based on this method, the piezoelectric smart layer isdeveloped and passes the engineering applicability tests. Secondly, from two perspectives of overallsystem integration and airborne application, two system integration methods are proposed. First, a busbased integration method of piezoelectric structural PHM system is put forward. It realizes thesynthesized integration of piezoelectric sensors network management, signal processing, healthmonitoring and PHM data management. A first international portable multi-channel piezoelectricsensors array scanning system is developed. Second, a miniature, all-digital and airborne impactmonitoring system integration method for regional monitoring of composite impact is put forward andthe system is also developed. It solves the contradiction between the urgent requirement of impactmonitoring and maintenance for large-scale composites and the additional weight and high powerconsumption of PHM system.3) On functional verification and application of the piezoelectric structural PHM system, comparedto the research abroad, the research of functional verification of the piezoelectric structural PHMsystem in China on real aircraft structure, especially on large and complex aircraft structures is little.The engineering application is still blank. To research the problem, the multi-channel piezoelectricsensors array scanning system is applied to an un-manned aerial vehicle (UAV) composite wing boxfor ground static strength experiment, during which the stability and the effectiveness of damagemonitoring of the system is validated. A synthesized functional demonstration and validation platformof the piezoelectric structural PHM system is built on a wing box, which validates the damage andimpact monitoring function for complex composite structures and data management function of thepiezoelectric structural PHM system.4) On research of aircraft structural PHM system architecture and validation, to research theestablishment problem of the architecture of the aircraft structural PHM system, a kind of two-levelarchitecture of aircraft structural PHM system that includes a vehicle-level and a fleet-level isproposed. A vehicle-level distributed aircraft structural PHM system architecture of airborne-groundcombination, member-level and regional-level hierarchical, multi-structural parts, multi-regional, multi-damage patterns is realized. A functional demonstration and validation platform is establishedfor regional-level aircraft structural PHM system of the vehicle-level aircraft structural PHM system.The developed piezoelectric smart layer passes the engineering applicability tests which areperformed by Aircraft Strength Research Institute of China. The main technical specifications ofpiezoelectric smart layer and multi-channel piezoelectric sensors array scanning system are tested byJiangsu Institute of Metrology. The research results achieved in this dissertation are applied tosituations such as advanced new aircraft development, life extension of in-service aircraft, large civilaircraft composite structure design and pipeline vibration monitoring by Chengdu Aircraft DesignInstitute, Institute of Air Force Equipment, Commercial Aircraft Corporation of China, Ltd., AircraftStrength Research Institute of China and so on.