Study On Motorcycle Ride Comfort Based On Road Simulation

Ride comfort is an important characteristic of motorcycle. At present, the domestic-made motorcycle's performance in NVH has a large gap with foreign products. In terms of simulation of motorcycle ride comfort, the excitation is standard signals, such as sine, step and grade B road, which has much difference to actual situation. Road simulation can reproduce motorcycle vibration of actual running conditions, and has good repeatability and high security characteristics. So study on motorcycle comfort combined with CAD/CAE and road simulation is necessary and meaningful whether theorily or practically.The thesis consulted lots of research literatures home and abroad, and analyzed research focuses and problems of road simulation test technique, virtual prototype technique and evaluation method of motorcycle. Based on this, the method of motorcycle road simulation test was optimized, and the simulation method based on road simulation and evaluation method based on speed and frequency weighting of motorcycle ride comfort were put forward. Studies have provided an effective way for motorcycle development.Firstly, by analyzing the principle of remote parameter control and key technology of road simulation test in detail, the platform of motorcycle road simulation test, which is two channels tire-coupling type, was developed, and motorcycle road simulation test was optimized. With the optimized test project, the precision and stability of iteration were greatly improved, and the road load spectrum was accurately reproduced in doors. Through disposing transducer of acceleration and strain, the road load spectrums of several motorcycles were acquired when running on Hainan Proving Ground, typical gravel and concrete road at different speed, then database of motorcycle road load spectrum was established. Using statistcal algorithm and filter to analyze load spectrum, and selecting acceleration of front and rear axles as despired response signal, simulation iteration and simulation test were implemented, at the same time excition spectrum of road simulation which represents actual road was obtained.Secondly, taking some 125 motorcycle as example, the 5-DOF vibration model and rigid-flexible coupling simulation platform of motorcycle were developed by combined with virtual protype and road simulation. On the one hand, the 5-DOF multi-body dynamic model was built. Also, the differential equation of motion and state-space formulation were derived according to Lagrange Equation, which provided an important theoretical fundament for vibration analysis of motorcycle. On the other hand, the 3-D finite element model of frame was built. By using Lanczos method, the flexible model of frame was obtained, and the analysis of frenquecy correlation and modal assurance criteria showed that the flexible model is correct. Taking into account non-linear characteristic of frame, absorber and tire, the rigid-flexible coupling simulation model of motorcycle ride comfort was developed, then the simulation platform which can reproduce actual vibration condition of motorcycle was created finally.On the basis of 5-DOF vibration model and rigid-flexible coupling simulation platform, the ride comfort of motorcycle was simulated with the pulse road and actual road spectrum as excitation respectively, at the same time the verification and evaluation methods were put forward. Through inputing same excitation into road simulator, the experiments were implemented, and the simulation results were qualitatively and quantitatively evaluated with PSD curve, maximum absolute value and average power. The study showed that simulation results and experimental results matched very well. According to the response signals, the vibration characteristic of the motorcycle was discussed, and some improving suggestions about ride comfort were presented.Finally, the thesis analyzed existing evaluation method of motorcycle ride comfort and relation between motorcycle speed and response in detail. Then a new evaluation method of motorcycle ride comfort based on speed and frequency weighting was put forward, which solved the conflict that the evaluation result is different when speed varieties. Lots of test datum showed that when motorcycle runs on gravel and concrete road, the speed obeys 3 distribution, and the parameters ofβdistribution were estimated by experimental datum. Combined with ISO 2631 and ISO 5349, the speed and frequency weighted RMS of acceleration was computed by MATLAB program, and ride comfort of the motorcycle was estimated effectively. The result showed that speed and frequency weighted RMS of acceleration is the synthetical reflection of RMS of acceleration at different speed.