Study On Riding Dynamics Of Motorcycles And All Terrain Vehicles

Riding dynamics performances, including ride quality and stability, are the main performances for motorcycles and All Terrain vehicles. The researches on this are not still maturity. In this dissertation, the key technologies of motorcycles and All Terrain Vehicles riding dynamics are studied, including research on the evaluation and assessment method for riding comfort, the development and application of the measurement system for riding comfort, the research on the dynamic characteristic of the body, the research on the modeling method of riding comfort, the research on All Terrain Vehicle stability.The researches on the evalution and assessement about human exposure to vibration are studied in-depth, the characteristic of motorcycles and All Terrain Vehciles riding comfort are found through lots of road testings, in trun the objective evalution method of riding comfort is built for motorcycles and All Terrain vehicles, where the weighted root-mean-square of accelerations is used as index to evaluate the vibration at hand and seat respectively. The objective elaluation method is feasible by the validation of lots of tests. However the subjective feeling is the finnaly assessment of the riding comfot, so a subjective evaluation method for riding comfort is also presented. The investigation on the riding comfort, with five grades, is carried out through more than ten reprensative motorcycles rode by several ten drivers and customers. The fuzzy evaluation model of motorcycles riding comfort is built through mathematics statistics and fuzzy logic method, and the relationship between the vibration magnitude (at seat and hand) and human feeling are presented.The portable measurement system which is suitable for the testing of motorcycles and All Terrain Vehicles riding comfort is developed by assembling the hardware equipments which could work independent of computer and by the development of the analyzing software for riding comfort which is programmed through time-domain and frequency-domain. Using this testing system, the character of riding comfort that the vibration in high-frequecy is big, the influence of engine is difference, the crest factors of vibration is about 5, and the side vibration except that of All Terrain Vehicle hand is little and could be ignored, is analyzed by tens of motorcycles and All Terrain vehicles.The dynamic characteristic of the frame is important for the riding comfort of motorcycles and All Terrain Vehicles, the modal analysis of motorcycle and All Terrain Vehicle frame is completed by finite element method and experimental method. An effective and simply finite element modeling method of the frame with engine, where engine is considered as a mass point connected with the frame by MSC.Nastran RBE2 element, is presented and validated by experiments. The influence of engine on the structure characteristic of the frame is great, so the modal characteristic of the frame with engine is more significant than the frame without engine for studying the motorcycle and All Terrain Vehicle riding comfort. Combing the modal analysis of the body and the road testing of the riding comfort, the relationship between the modal characteristic of the body and riding comfort is discussed, and then two improvement examples of the riding comfort by improving the dynamic character of the body are presented and validated.The vehicle mutli-body dynamical model is set up with MSC.Adams, where the influence of the impacts from both road and engine is considered. The analyses show that the 2 dof model and the flexible frame are necessary for the analysis of riding comfort. The influence of the stiffness and damping of front spring, rear spring and seat cushion are analyzed by orthogonal tests. The seat cushion is the most important for the seat vibration, and the the front spring is more important for seat vibration of the motorcycle and hand vibration of both motorcycle and All Terrain Vehicle than the rear spring, but the rear spring is more important for seat vibration of the All Terrain Vehicle than the front spring, meanwhile the influence of the interaction between factors should be pay attentioned.According to the controllability and stability testing procedures for automobiles, steady static circular test is completed. The results indicated that the All Terrain Vehicle had under-steering behavior at the range of low lateral accelerations, over-steering at middle lateral acceleration and under-steering at high lateral acceleration, due to its single rocker rear suspension and single driving axle. The simulation with muti-body dynamic model is consistent with the test. The steering behavior of the All Terrain Vehicle could be changed by body shifting of the driver. The steering transient response test (steering wheel angle pulse input) show that the resonance of All Terrain Vehicle is about 1.2 Hz.