Road and track irregularities have an important influence on the dynamic behaviour of vehicles.Knowledge of their characteristics and magnitude is essential for the design of the vehicle but also for comparable homologation and acceptance tests as well as for the planning and management of track maintenance. Irregularities of tracks and roads are regularly measured using various measurement technologies. All have advantages and weaknesses and require several processing steps. Characterisation of irregularities is done in the distance as well as in the wavelength domain. For rail irregularities, various distance domain description methods have been proposed and are in use. Methods have been analysed and compared with regard to their processing steps. Several methods have been analysed using measured irregularity and vehicle response data. Characterisation in the wavelength domain is done in a similar way for track and road irregularities. Here, an important issue is the estimation of the power spectral densities and the approximation by analytical formulas. For rail irregularities, periodic defects also play an important role. The use of irregularities in simulations requires various processing steps if measured irregularities are used, as well as if synthetic data are utilised. This paper gives a quite complete overview of rail irregularities and points out similarities and differences to the road.
Advanced requirements for quality and functions, reduced development time, and increasing international competition motivate fundamental changes of the development processes. This puts much attention on the potentials of numerical simulation, i.e. experiments on the virtual product, while experiments on real prototypes will always remain an important part of the development process, for example to fulfill legal requirements, to achieve parameters for the simulation work, and to validate intermediate results and of course the final tuning. One step towards the virtual development of ride and handling characteristics of passenger cars is to achieve accuracy of simulation results which can be compared to what can be achieved with carefully selected experiments. This paper will present the state-of-the-art of current simulation technologies, their already available potentials and some remarks on current limitations. With this type of advanced simulation technologies, engineers are enabled to develop complex mechatronic chassis systems like active suspensions or stability control systems in relatively short periods of time to a high degree of maturity. A second use of these virtual prototypes is for extensive parameter studies or even optimizations, which will also give more insight in the complex nonlinear interactions of the chassis systems. This can even yield to a complete change of development processes from an analytical incremental setup to more target driven work.
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