Research On Measurement And Simulation For Characteristics Of Engine Front End Accessory Drive System

Front End Accessory Drive(FEAD)system of automotive is a torque transmission belt drive system.Various types of vibration and noise generated by the irregularities of crankshaft’s rotary speed,the variables driving torque of the accessory pulleys,and the components’ processing errors and installation errors When engine in running,which will greatly affect the efficiency of the accessory system,as well as the operating life of the belt and bearing and the vehicle NVH performance.Therefore,simulation and testing of the performance of FEAD system has important implication for an accurate assessment of the state of the engine.The FEAD Testing and Analysis System based on Virtual Instrument can use the common acquisition equipment and programmable test and analysis software to complete the testing tasks quickly and easily,with low cost and high accuracy.Users have the ability to customize their own signal analysis method and to provide rich results display and output interface.The methodology for the study of the dynamical behavior of FEAD system is based on the techniques of multi-body numerical simulation by AVL Excite TD,which are sufficient for the reliable prediction of belt’s forces,lateral vibration,tensioner’ hysteretic behaviors,pulley’s rotational vibration and load.The main research contents of this paper are as following:1.A theoretical study for the performance of FEAD system is first carried out to choose the practical test method,and then completed the hardware selection,including sensors and data acquisition system selection.2.Analyze software requirements of the daily test and analysis according to the principles of project management,preliminary plan the software functional modules;code the software based on queue-based state machine and the producer/consumer framework,which can ensure the integrity of the data when online analysis with large-scale calculation,but also take into account the good user interface responsiveness and Secondary development.3.Introduce the principles and the software implementation of the main function modules: including the signal pre-processing module,the torsional vibration calculation module,the signal analysis module(including time domain analysis,frequency domain analysis and harmonic analysis time);calibrate the angular vibration calculation module by the torsional vibration calibrator,the calibration results shows: the relative error for the single-order angular vibration simulation signal is less than 3.52%,the absolute error for the mixed-order angular vibration simulation signal is less than 0.015 deg,the angular vibration calculation accuracy can meet the needs of field testing.4.Test the static and dynamic parameters of the seven pulley-belt FEAD system,including the static tension of the belt,angular vibrations of the pulleys,the swing angle of tensioner arm,the load force of tensioner pulley and transverse vibration of the belt span;calculate the dynamic tensions of the two belt spans adjacent to tensioner pulley with the load force of tensioner pulley,the slip ratio is estimated by the relative velocity between pulleys.The test conditions includes external characteristic condition,partial load condition,continuous load run-up condition and engine start condition.5.This paper presents a comprehensive multi-body dynamics(MBD)model and the relevant simulation environment(AVL Excite TD),which takes into account the entire seven belt-pulley FEAD system as a fully coupled system.The measured crankshaft rotary motion data used as the excitation of the model.Simulation results and their comparison with experimental data are presented for the belt drive system,which indicate that the prediction of the angular vibrations of the pulleys and the swing angle of tensioner arm have high accuracy,and the belt tension also match the experimental data.There are large gap of the belt transverse vibration between simulation results and experimental data,while the trajectory display of belt segment can determine the serious fault of FEAD system caused by belt transverse vibration.