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Item type:Publication, Access status: without files , Dynmanto: A Matlab Toolbox for the Simulation and Analysis of Multibody Systems(2020-08); ; The Dynamic Modeling and Analysis Toolbox DYNMANTO is an acedemic MATLAB code which allows the modeling, simulation and sensitivity analysis of spatial multibody systems. The kinematics of rigid and flexible bodies is described by the floating frame of reference formulation and the body properties are provided by standard input data files. In this way the evaluation of the equations of motion is computationally efficient and an arbitrary parameterization of the system can be achieved. The latter is important in the automated adjoint sensitivity analysis of multibody systems, which yields gradient information for system analyses, parameter identifications or gradient-based optimizations. The capabilities of DYNMANTO are demonstrated by the application examples of a flexible two-arm manipulator and Chebyshev's Lambda Mechanism.Publicationtype: Conference Paper365 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adjoint sensitivity analysis of flexible multibody systems in differential-algebraic form(2020-02); ; In the analysis and optimization of flexible multibody systems, an efficient sensitivity analysis can be performed using the adjoint variable method. Thereby, the procedure strongly depends on the equations of motion, which can be formulated either by minimal or by redundant coordinates yielding in turn a system of ordinary or differential-algebraic equations. In the current work, redundant coordinates are used to set an adjoint system for the sensitivity analysis of flexible multibody systems with kinematic loops, which are modeled using the floating frame of reference formulation. The procedure is tested by computing the structural gradient for the flexible crank of a slider-crank mechanism and compared with a reference procedure, where the adjoint system is formulated using minimal coordinates.Publicationtype: Journal Article106 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Topology optimization of flexible multibody systems using a parametrized level set methodPublicationtype: Conference Paper95 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Contributions to topology optimization in flexible multibody dynamics(2019); This work contributes to the development of the topology optimization of flexible multibody systems. The conventional coupling strategies of the topology optimization and the flexible multibody systems exhibit two limitations regarding its applicability in real-life and industrial application: the high computational cost that limits the optimization size, and the restricted capability of considering nonlinear effects such as contact in flexible structures. These limitations are both addressed in this work, and steps toward the modelling of nonlinearities and the large-scale topology optimization of flexible multibody systems are introduced.Publicationtype: Doctoral Thesis1072 1356 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Gradient Approximation in Flexible Multibody Systems Using a Multigrid ApproachThe approximation of gradients with a multigrid approach is presented in the framework of flexible multibody systems, in which the flexible bodies are modeled using finite element method. For the cases where the number of design variables are high, for example, in topology optimization where the density of each element is chosen as a design variable, the gradient computation becomes computationally infeasible. The proposed approximation, in which the gradients are computed simultaneously on a fine grid and a coarse grid, can significantly reduce the computation time without hindering the accuracy of the gradients.Publicationtype: Conference Paper63 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Topology optimization of members of flexible multibody systems under dominant inertia loading(2018-04-01); ; The topology optimization of members of flexible multibody systems is considered for energy-efficient lightweight design, where the gradient calculation has an essential role. In topology optimization of flexible multibody systems, where the function evaluations are very time consuming, the gradient information is necessary to accelerate the optimization process. Different approaches have been introduced and tested for the gradient calculation in the fully coupled topology optimization of flexible multibody systems. However, the computation and implementation costs of these methods are high, which limits the optimization size and the possible number of design variables. In this work, we present a modified gradient calculation based on the equivalent static load (ESL) method, which combines the time efficiency of gradient calculation of the ESL method with the higher accuracy of gradient calculation in the fully coupled methods. This modified approach, which takes into account the linear dependencies of inertial loads on acceleration, is tested on the application example of a flexible slider-crank mechanism, and the results are compared with the weakly coupled ESL method and a fully coupled optimization where gradients are calculated using the adjoint variable method.Publicationtype: Journal Article189 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adjoint variable method for the sensitivity analysis of flexible multibody systems in differential-algebraic formPublicationtype: Conference Paper87 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Modeling of revolute joints in topology optimization of flexible multibody systems(American Society of Mechanical Engineers (ASME), 2016-09-09); ; In recent years, topology optimization has been used for optimizing members of flexible multibody systems to enhance their performance. Here, an extension to existing topology optimization schemes for flexible multibody systems is presented in which a more accurate model of revolute joints and bearing domains is included. This extension is of special interest since a connection between flexible members in a multibody system using revolute joints is seen in many applications. Moreover, the modeling accuracy of the bearing area is shown to be influential on the shape of the optimized structure. In this work, the flexible bodies are incorporated in the multibody simulation using the floating frame of reference formulation, and their elastic deformation is approximated using global shape functions calculated in the model order reduction analysis. The modeling of revolute joints using Hertzian contact law is incorporated in this framework by introducing a corrector load in the bearing model. Furthermore, an application example of a flexible multibody system with revolute joints is optimized for minimum value of compliance, and a comparative study of the optimization result is performed with an equivalent system which is modeled with nonlinear finite elements.Publicationtype: Journal Article130 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the influence of model reduction techniques in topology optimization of flexible multibody systems using the floating frame of reference approach(Springer, 2016-01-01); ; ; ; Employing the floating frame of reference formulation in the topology optimization of dynamically loaded components of flexible multibody systems seems to be a natural choice. In this formulation the deformation of flexible bodies is approximated by global shape functions, which are commonly obtained from finite element models using model reduction techniques. For topology optimization these finite element models can be parameterized using the solid isotropic material with penalization (SIMP) approach. However, little is known about the interplay of model reduction and SIMP parameterization. Also securing the model reduction quality despite major changes of the design during the optimization has not been addressed yet. Thus, using the examples of a flexible frame and a slider-crank mechanism this work discusses the proper choice of the model reduction technique in the topology optimization of flexible multibody systems.Publicationtype: Journal Article134 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Topology optimization of bearing domains in flexible multibody systemsTopology optimization can be used for optimizing members of flexible multibody systems to enhance different characteristics of these systems. Here, a topology optimization scheme for flexible multibody systems is presented in which a more accurate model of bearing domains is included in the optimization. This is especially of interest since a connection between flexible members in a multibody system using bearings is widely seen in many application. Moreover, the modeling accuracy of the bearing area is shown to be influential on the shape of the optimized structure. As an application example, a flexible slider-crank is optimized here for minimum value of compliance in its nonrigid part. The flexible body is incorporated in the multibody simulation using the floating frame of reference formulation and its elastic deformation is approximated using shape functions calculated in the model order reduction analysis. The bearing loads are incorporated in this framework by introducing a corrector load in the bearing model. The results of the optimization is compared with an equivalent system which is modeled using nonlinear finite elements.Publicationtype: Conference Paper74