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Most papers present analyses of dynamic interactions between vehicle and flexible guideway that presuppose constant vehicle forward velocity, but that supposition precludes the analysis of the interaction between guideway and vehicle suspension and forward movement. This work presents the modelling of a magnetically levitated vehicle, a elevated, flexible guideway, which may have grades, considering the forward dynamic and including a very simplified model of a linear synchronous motor. The LQG-LTR method is used to design the magnetic levitation control system and numerical simulations are used in system analyses. The developed model is suitable for the proposed studies, and it is verified that the reduction of guideway stiffness has a negative impact in stability of magnetic levitation system and in ride comfort.

A great interest in active and semi-active suspensions has been arised, and that poses the problem of design a control system, and the first step is the modelling of the vehicle, its suspension, and its interaction with the guide-way. In this paper the multiport model approach and its associcited bond graph representation are suggested to perform the modelling task, since it can cope with a wide range of energy domains, offers clear and succint representation of systems and devices, allows an organized way to develop the system model and is suitable for development as a computer aided modelling software.

This work presents preliminary results from a research about active suspension control regarding vehicle body flexibility. At first we are examining the use of LQG-LTR method, which allows to consider unstructured uncertanties in the compensator design if the model has the same number of inputs and outputs. The method used makes an inverse of the plant, so it must not have transmission zeros with positive real parts. These requirements create some difficulties, leading to observability problems (probably) in the particular system used in the numerical analisys.