Colloquia

Summary

Multibody dynamics is the evaluation of systems consisting of multiple mechanical bodies that are connected by joints that constrain their relative motion. This method, based on classical mechanics, was first used in satellites in the mid-sixties. Nowadays it is used for analysis of many different types of structures through modelling of such systems.

By including flexibility in a model, an even more accurate description of a system can be obtained. This gives insight in certain system parameters that can be changed according to these results. The result is a design for the system that is possibly cheaper and/or more reliable.

Different methods exist for modelling flexible multibody systems. In this project is made use of flexible bodies, discretized by the finite element method, for which the movement through space is described with the floating frame of reference approach. Many authors discussed the theory that is the basis of this method or used it (in commercially available software) to model specific systems. However, no general approach is available for making a spatial flexible multibody model from a concept idea. Therefore describing this approach is the main goal of this project and its application is best motivated by simulating a real-life case. The system to which the method is applied is the Pagode, a fairground ride in Dutch amusement park Efteling.

First, a rigid multibody model is made for the Pagode. This includes a description of the kinematics and kinetics of the system. This model is thereafter extended to a flexible one by incorporating a finite element model. A model reduction technique is applied to make the model less computationally expensive. For a complete discussion of the flexible model, the stability of the model is analyzed and the equilibrium position is computed. The effect of including flexibility to the model of the Pagode is analyzed trough a comparison of the positions, velocities, accelerations and actuation forces of both models. The main difference is in vibrations that are not present in the rigid model.

For a conclusion on the accuracy of the results, these are compared to the results of a model in the commercially available flexible multibody software, ADAMS. The difference in the models is mainly in the amount and shape of the elements. The underlying software cannot be compared, but results are comparable. This makes that can be concluded that the approach is well suited for giving a dynamic description of the Pagode.