Condition Monitoring For Vehicle Suspension System Based On Vibration Modal Characteristic Analysis

In recent years,the demands for the vehicle ride comfort,security and other performance are getting higher and higher.Suspension system is an important component that directly affects vehicle safety,ride comfort and handling,and if it fails,that would cause serious economic losses.In the case of different types of faults,the failure ratio caused by the suspension components is very high.Therefore,the normal operation of the suspension system will directly affect the safety performance of the vehicle.Detecting suspension faults timely can effectively reduce the probability of accidents,and ensure traffic safety and improve ride comfort.However,due to the complex road conditions,its excitation of road unevenness to the tire is generally random excitation in a certain frequency band,so how to on-line monitor the operation of the suspension system has been difficult to study.The stochastic subspace identification is a kind of modal identification algorithm which takes the response signal as input,has the advantages of convenient test signal,suitability for stochastic vibration.Thus,more and more scholars began to pay attention to it.But its identification accuracy is much more affected by the damping ratio because the damping ratio of the suspension system is relatively high(between 20% and 30%),which limits the application of the stochastic subspace identification method in vehicle suspension system monitoring.Therefore,this paper proposes to apply the improved average correlation subspace method to the suspension on-line monitoring system,average correlation signal replace the raw signal as the input signal,thereby enhance the identification accuracy of the algorithm under complex conditions.Then,establish a seven-degree-of-freedom linear vehicle vibration model to identify the modal parameter under different damping ratio,road surface excitation and noise conditions.And effect of the average correlation random subspace algorithm on the suspension state monitoring is verified.The sensitivity of each modal parameter to fault is judged,and the online monitoring method based on vibration mode and modal energy difference method is established.Finally,design the sensor layout program to collect the data of vehicle body motion,including body vertical acceleration,pitch angle and roll angle.And the monitoring test of the different fault forms of the suspension is carried out,which verified the credibility of this online monitoring method.