Study On Integrated Digital Watermarking Based On HVS Of Contourlet Domain

With rapid economic growth, automotive market expanding, and continuous improvementsof technical regulations, the competition becomes increasingly fierce, which requiresengineers to develop higher quality, cheaper automotive products. Heavy-dutytrucks,especially large-tonnage heavy-duty trucks are the most important road transport tool,with advantages of low transport costs，high safety and transport efficiency. Selectingefficient，accurate methods and tools to study the performance of heavy-duty trucks is vitallyimportant.In the past, engineers regarded the frame as a rigid body when they studied performance oftrucks, with little concerning the influence of flexibility of frame, but heavy-duty trucks havethe characteristics of long body, large wheelbase and large bearing quality, and frame is themain bearing parts of heavy-duty trucks, accounting for about one tenth of the entire truckquality and carrying most of the load. The flexibility of frame is very obvious, it can not beignored, and it plays a very important role on the performance of heavy-duty truck.Regarding the frame as main study object, getting modal parameters of the frame by modalanalysis, and converting it to flexible frame, the full rigid-flexible coupling truck model canbe established, and then the performance simulation analysis can be conducted. By doing so,the influence of frame flexibility on the performance of truck can be analyzed；theperformance simulation analysis can reflect the actual situation, theoretical basis ofimproving the performance of heavy-duty truck can be provided； the coupling andinteraction between the flexible body and rigid body of truck system can be revealed； a newmethod of performance analysis and prediction can be provided in the heavy-duty truckproduct development and design stage.The main contents are as follows:(1) Finite element modeling and modal analysis of the frameThe Hypermesh software were intrduced briefly at first, then the key modeling techniques inHypermesh were studied and summarized, including geometry cleanup, meshing elements,choice of element type, element quality inspection, etc.; after that, the finite element modelwas established based on the CAD model enterprise provided; Setting analysis parameters,the free modal analysis and modal synthesis analysis was conducted, and the results wereanalyzed as well; lastly, the MNF file of frame was generated by using Motionview moduleof Hyperworks package.(2) Establishment of heavy-duty truck model The ADAMS/Car module, basic methods of modeling in ADAMS/Car and methods ofgenerating flexible bodies in ADAMS were introduced briefly; then the frame MNF filewhich had been generated was verified, after that, the flexible frame templates andsubsystems were built by using the second method based on the frame MNF file; with othersubsystems built, the rigid-flex coupling truck model was established by assembling all ofsubsystems; lastly, the quality and moment of inertia of established model was adjustedbased on the real quality and moment inertia of truck.(3) Handling stability and ride comfort simulation analysis of the heavy-duty truckBased on national standards of handling stability, six simulation conditions and settingmethods of simulation parameters were introduced, after that, the corresponding simulationswere conducted; then the pavement composition principle, methods of building random roadexcitation and pulse road excitation and setting methods of ride comfort simulation werestudied, two kinds of ride comfort simulation were conducted based on established truckmodel; the influence of frame flexibility on the two kinds of performance was analyzed bycomparing the simulation results.Based on rigid multi-bodies truck dynamic model which research group has established, themethod of establishment of flexible frame was studied, then full rigid-flexible coupling truckmodel was established, reference to the national standard of handling stability and ridecomfort, setting corresponding simulation conditions and conduct two kinds of performancesimulation, the influence of frame flexibility on handling stability and ride comfort ofheavy-duty truck was analyzed by comparing the simulation results. By summarizing keymodeling techniques in Hypermesh, such as geometry clean-up, meshing elements, elementtype and element quality inspection, and summarizing the method of generating MNF file inthe Motionview module of Hyperworks package and the methods of generating flexiblebodies in ADAMS, lay the foundation to establish a sound rigid-flexible coupling vehicledynamic model by using both finite element analysis software and multi-body dynamicssoftware.