Analysis Of Vibration And Noise Of Automobile Air Conditioning System Based On OTPA

Under certain conditions,the automobile air conditioning system causes interior noise and reduce the comfort of drivers and passengers.In order to solve this problem,it is necessary to find out the main noise sources and vibration sources that affect the abnormal sound of the target points in the car,and to optimize and improve them,so as to achieve the purpose of reducing vibration and noise.The research on vibration and noise problems is mainly from three aspects: source,transfer path and receiver.No matter what the form of abnormal noise is,the incentive is transmitted to the target point through the propagation path and the transmission path of the air sound,resulting in interior noise of the target.First,control the generation of abnormal noise from the source.For the air conditioning system,all forms of energy are derived from the compressor and are also affected by the main parts on the front end of the engine,generator and other front wheels.But because compressor,engine and so on have been strictly designed and debugged before coming out of the factory,it is difficult to make any changes.Therefore,the idea of controlling from the source is not feasible.Second,control and improvement from the receiver side,which is passive control and temporary solution.Therefore,the most effective and direct way is to diagnose and control the propagation path.Based on this,this article takes a domestic SUV as a prototype vehicle and proposes an analysis method based on operational transfer path anslysis to quickly find out the main excitation source and transfer path that affect the target point noise.First,the noise signals collected in different working conditions are analyzed,such as steady power spectrum analysis,speed rise spectrum array analysis,order analysis and so on,to determine the approximate rotational speed,frequency and frequency spectrum characteristics of the vehicle's internal noise,and to authenticate the abnormal sound target through interactive filtering and subjective evaluation.Secondly,the working noise of the compressor is passed through the working noise of the compressor.The possibility of the air acoustic transmission path in the vehicle is investigated.The sound transfer function from the engine cabin to the vehicle is studied and used as the criterion for the evaluation of the level of the automobile acoustic packaging.Then,the transmission path analysis is carried out to find out the difference in the transmission path of some non independent vibration components and measuring points in the air conditioning system.Vibration components and measuring points with maximum contribution frequency are avoided,thus avoiding the influence of non independence.Then the experimental modal analysis and theoretical modal simulation are carried out on the generator bracket and the armature of the compressor,and the process of influencing the screaming of the compressor work and causing the abnormal sound of the speed in the vehicle is expounded.Finally,the crosstalk elimination experiment is carried out on the basis of the traditional transmission path analysis.The Cholesky decomposition and least square method are used to eliminate the crosstalk of the vibration source and optimize the transfer path to obtain more realistic source data.Through experiments and data processing,the data before and after optimization are compared and analyzed.It is found that the crosstalk cancellation method achieves certain optimization results.