structure preserving simulation and optimal control

Research is focused on the structure-preserving simulation and optimal control of flexible multibody dynamics, including nonlinear elastodynamics and geometrically accurate models for beams. The practical application deals with nonlinear beams, large deformation problems, long-term simulations and coupled multiphysics multibody systems.

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Variational integrators are based on the discretization of the variational principle. It is applied to an approximation of the action functional and results in the discrete Euler-Lagrange equations. If space time is discretized in one step, the resulting integrator is multisymplectic, i.e. symplectic in both space and time.Those integrators are suitable for the simulation of flexible multibody systems including beams, shells and 3D continua. Some of the symmetries present in the continuous system…

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Within the framework of the research work of the Bayerische Bionikzentrum, the project requested for this project aims to develop and operate energy-saving actuators modeled on natural muscle tissue and used in kinematics with multiple degrees of freedom. The focus should be on the functional principle of Dielectric Elastomer Actuators (DEA) for the construction of individual muscle cells and their linking to artificial muscles. In order to achieve the goal of an energy-efficient and energy-storing as well as flexible and highly dynamic actuator system, methods for producing the muscle stacks, microcontroller circuits for actuating the actuators, measuring principles and methods for determining joint positions, and finally simulation and control models for these actuators and kinematics must be developed become. In the long term, the described research will form the basis for a new generation of robotic solutions with a broad application spectrum from intrinsically safe service robots to highly dynamic mobile kinematics to bionic prostheses. In addition, the technology to be developed opens up the possibility of reproducing the most diverse forms of movement and physiological processes of living beings through the use of complexly distributed microactuators. Thus, the transfer of principle mechanisms to technical problem solutions from a wide range of different life forms can be realized.

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Simulation is of great importance when studying everyday or athletic motions with regard to improvements in ergonomics and performance. In particular for medical problems like analysing gait or optimising prostheses as well as for planning robot manoeuvres, simulation is often the only way to estimate the actuating and applied forces and torques. An approximate solution can only be as accurate as the underlying numerical method represents the system’s characteristic properties. If, for example, t…

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The overarching goal of this project (phases I and II) is the development of models and structure preserving solution methods for biomechanical optimal control problems involving uncertainty to enable the reliable prediction of human motion with prostheses and their analysis. To be able to get close to the consideration of a real world scenario when simulating the uncertain motion with prosthesis, we want to exemplarily focus on one particular foot prosthesis and perform measurements. We will…

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Das Verbundprojekt DYMARA hat die Entwicklung eines innovativen digitalen Menschmodells (Manikins) mit  detaillierter Modellierung der Skelettmuskulatur und schnellen numerischen Algorithmen zum Ziel. Mit diesem Manikin soll es möglich werden, den Menschen simulationsgestützt auf optimale Weise in sein Arbeitsumfeld zu integrieren und Ermüdungen, Erkrankungen sowie Unfälle am Arbeitsplatz zu vermeiden. Neben diesen ergonomischen Gesichtspunkten soll das Menschmodell auch zur Therapieplanung im m…

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The goal of this project is to apply techniques of biomechanics and optimal control to generate realistic human-like motions of the DHM from generic working instructions like for example move a box from A to B. Such a model would enable the engineers to take into account physical workloads and reachability issues in virtual assembly planning.

The digital human is modeled as a biomechanical multibody system with muscles as actuators. The motions of the DHM for specific working…

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In the simulation of continuum mechanical problems of materials with
heterogeneities caused e.g. by a grained structure on a smaller scale
compared to the overall dimension of the system, or by the propagation
of discontinuities like cracks, the spatial meshes for finite element
simulations are typically consisting of coarse elements to save
computational costs in regions where less deformation is expected, as
well as finely discretised areas to be able to resolve discontinuities
and small scale phenomena in an accurate way. For transient problems,
spatial mesh adaption has been the topic of intensive research and many
strategies are available, which refine or coarsen the spatial mesh
according to different criteria. However, the standard is
to use the same time step for all degrees of freedom and adaptive time
step controls are usually applied to the complete system.

The aim of this project is to investigate the kinetics of heterogeneous,
e.g. cracked material, in several steps by developing suitable
combinations of spatial and temporal mesh adaption strategies.

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Stacked dielectric elastomer actuators bear analogy to the behaviour of human muscles in terms of contracting in length direction when stimulated. They are suitable for point-by-point application of a force. Therefore, dielectric elastomers allow for a sophisticated, efficient and noiseless actuation of systems. However, the use of elastic actuators is also accompanied by new control challenges. As the computational cost for solving optimal control problems is significantly affected by the num…

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Highly flexible slender structures like yarns, cables, hoses or ropes are essential parts of high-performance engineering systems. The complex response of such structures in real operational conditions is far beyond the capabilities of current modelling tools that are at the core of modern product development cycles.

Addressing this requires a new generation of brilliant scientists. Marie Skłodowska-Curie funding of the THREAD project will bring together young mechanical engineers …

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For a list of publications related to structure preserving simulation and optimal control, please look here.