Littérature scientifique sur le sujet « Flex-multibody »

The dynamics of multibody systems with deformable components has been a subject of interest in many different fields such as machine design and aerospace. Traditional rigid-flexible systems often take a lot of computer resources to get accurate results. Accuracy and efficiency of computation have been the focus of this research in satisfying the coupling of rigid body and flex body. The method is based on modal analysis and linear theory of elastodynamics: reduced modal datum was used to describe the elastic deformation which was a linear approximate of the flexible part. Then rigid-flexible multibody system was built and the highly nonlinearity of the mass matrix caused by the limited rotation of the deformation part was approximated using the linear theory of elastodynamics. The above methods were used to establish the drop system of the leaf spring type landing gear of a small UAV. Comparisons of the drop test and simulation were applied. Results show that the errors caused by the linear approximation are acceptable, and the simulation process is fast and stable.

The motion of a semisubmersible drilling rig must be checked in advance to satisfy the safety criteria of the rig. However, the complexity of the rig's connections makes it difficult to analyze the rig motion during the drilling operation because it is connected to the seabed by the blow-out preventer (BOP). The rig's connections consist of several pieces of risers, a telescopic joint, and a riser tensioner system. Also, from a macroscopic perspective, the risers should be regarded as flexible threads. Therefore, this study developed a rig motion analysis program considering the deformable effects of flexible risers and the full connectivity of the drilling rig. Flexible multibody dynamics (FMBD) based on the absolute nodal coordinate formulation (ANCF) is adapted for the mathematical modeling of the risers and joints. Acting as an external disturbance, a hydrodynamic force and current force are exerted on the drilling rig and the risers, respectively. The drilling rig is fully modeled including the riser tensioner system, telescopic joint, flexible risers, and upper and lower flex joints. The motion analysis with and without connections was fulfilled to verify the effect of connectivity. Moreover, we observed that the movement of the drilling rig increases as the current speed increases. Finally, the simulation is successfully applied to check the motions and tensions of the drilling rig in moderate and storm conditions.

La tesi mira a studiare il comportamento rotordinamico di cuscinetti a strisciamento innovativi in diamante policristallino. E' stato creato un banco prova strumentato per valutare orbite, accelerazioni e coppia assorbita e parallelamente è stato implementato un modello flex-multibody su piattaforma Matlab/Simulink con lo scopo di prevedere la dinamica del banco successivamente a una sua calibrazione sulla base dei dati sperimentali acquisiti.

In this paper, an effective method in dynamic modeling of spatial flexible-link robots under large displacements and small deformations is discussed and a generic Matlab™ software simulator based on it is presented and validated. The adopted method is based on an Equivalent Rigid Link System (ERLS) that enables to decouple the kinematic equations of the ERLS from the compatibility equations of the displacements at the joints allowing an easy and recursive procedure to build the robot dynamic matrices. The simulator is suitable for dynamic modelling of generic 3D serial flexible-link robots. The Matlab™ software simulator is validated with respect to the Adams-Flex™ commercial software, which implements Floating Frame of Reference (FFR) formulation, one of the most used methods for dynamic modeling of multibody flexible-link mechanisms with large displacements and small deformations.