Analyse degenerativer Bewegungseinschränkungen durch Einbindung empathokinästhetischer Sensordaten in biomechanische Menschmodelle
(Third Party Funds Group – Sub project)Overall project: Empatho-Kinaesthetic Sensor Technology
Term: 2021-07-01 - 2025-06-30
Funding source: DFG / Schwerpunktprogramm (SPP)
Modelling, optimisation and control of Stirlingcycle devices in a port-Hamiltonian framework
(Own Funds)Term: since 2020-01-01
Electromechanically coupled beam models for stacked dielectric elastomer actuators
(Third Party Funds Single)Term: 2020-01-01 - 2022-12-31
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
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 number of model degrees of freedom, reduced and problem specific actuator models are superior to general but cost-intensive finite element models.
Joint Training on Numerical Modelling of Highly Flexible Structures for Industrial Applications
(Third Party Funds Single)Term: 2019-10-01 - 2023-09-30
Funding source: EU - 8. Rahmenprogramm - Horizon 2020
URL: https://thread-etn.euHighly 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 and mathematicians who will develop mechanical models and numerical methods for designing highly flexible slender structures, and support the development of future virtual prototyping tools for products where such structures have a key role in functional system performance.
THREAD is a unique network of universities, research organisations and industry which by addressing fundamental modelling problems will ultimately enable the field to better meet the needs of different industries. A group of 14 Early Stage Researchers (ESRs) will receive comprehensive training covering state-of-the-art research topics along the modeling of highly flexible slender structures for industrial applications as well as valuable transferable skills. They will benefit from close cooperation with twelve industrial partner organisations implementing a comprehensive programme of research secondments and contributing their experience.
High order variational integrators for continuum mechanics, constrained mechanical systems and optimal control
(Own Funds)Term: since 2019-08-15
A mechano-geometric framework to characterize macromolecular ensembles
(Third Party Funds Single)Term: 2019-06-01 - 2021-05-31
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
Teilprojekt P2 - Atomistics of Crack-Heterogeneity Interactions
(Third Party Funds Group – Sub project)Overall project: Skalenübergreifende Bruchvorgänge: Integration von Mechanik, Materialwissenschaften, Mathematik, Chemie und Physik (FRASCAL)
Term: 2019-01-02 - 2023-06-30
Funding source: DFG / Graduiertenkolleg (GRK)
The fracture of a brittle solid is crucially determined by material heterogeneities directly at the crack front where the stress field diverges and the usual homogenization strategies are no longer applicable. While this problem has attracted significant interest, currently no consistent theory that relates local changes in properties to the local fracture behavior and macroscopic failure criteria exists. In contrast to the long-range elastic interactions, the direct interaction of the crack front with heterogeneities cannot be described by continuum methods but requires an atomistic treatment.
The aim of this project is to study the influence of various types of heterogeneities on the energy dissipation mechanisms in different classes of materials.
Teilprojekt P9 - Adaptive Dynamic Fracture Simulation
(Third Party Funds Group – Sub project)Overall project: Fracture across Scales: Integrating Mechanics, Materials Science, Mathematics, Chemistry, and Physics (FRASCAL)
Term: 2019-01-02 - 2023-06-30
Funding source: DFG / Graduiertenkolleg (GRK)
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.
Computational and experimental biomechanics
(Own Funds)Term: since 2017-09-01
Muscle paths in the biomechanical simulation of human movement and MBS integration
(Third Party Funds Group – Sub project)Overall project: 05M2016 - DYMARA: A dynamic manikin with fibre-based modelling of skeletal musculature
Term: 2016-12-01 - 2020-06-30
Funding source: BMBF / Verbundprojekt
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 muskulären Bereich und zur Gestaltung von Prothesen und Orthesen eingesetzt werden können. Um die Dynamik des muskuloskeletalen Systems hinreichend genau zu erfassen, wird ein Modellierungsansatz verfolgt, der auf der Methode der mechanischen Mehrkörpersysteme (MKS) basiert. Solche Modelle sind durch die Robotik inspiriert und werden bereits heute in vielen biomechanischen Anwendungsfeldern eingesetzt. Die Modellierung der Muskulatur stellt jedoch nach wie vor eine große Herausforderung dar, insbesondere wenn Aspekte wie Rechenzeit auf der einen und Berücksichtigung der anatomischen und physiologischen Gegebenheiten auf der anderen Seite zu beachten sind. Hier setzen wir mit unserem Projekt an: Ein neu zu entwickelndes eindimensionales Kontinuumsmodell, das einzelne Muskelfaserbündel realitätsnah beschreibt, soll die bisher üblichen diskreten Kraftelemente im MKS-Modell ersetzen und mit schnellen, problemangepassten numerischen Algorithmen zur Berechnung von Bewegungssequenzen und zur Steuerung des Manikins kombiniert werden.
Establishment of a heart support system as a contractile membrane based on the pericardium
(Third Party Funds Single)Term: 2016-05-01 - 2021-03-31
Funding source: Stiftungen
This projectcontains the establishment of a heart support system as a contractile membrane based on the pericardium to minimize theconsequences of severe heart disease and to maintain proper cardiacfunction. The project is a research cooperation between the Chair ofApplied Dynamics and the Pediatric Cardiology at the Friedrich-Alexander-Universität Erlangen-Nürnberg and is funded by the Klaus Tschira Foundation.
The project includes the study ofcardiac function under pathological and normal conditions by developingcomputer models of the heart, which are validated with experimental data ofpediatric cardiology of the University of Erlangen Nuremberg. The clinicalmeasurements and experimental data, as well as the simulation model are basedon rat hearts. Subsequently, a cardiac support system based on a membrane is tobe designed to improve or at least maintain heart function under pathologicalconditions.
In particular atthe Chair of Applied Dynamics, we are focusing on the development of theunderlying computational heart model including the anatomy, morphology,electrophysiology and also the fluid-structure interaction to be able to buildup the optimized heart support system but also to better understand thefunction of the heart and thus to predict or early detect cardiac dysfunctions andbring new treatments to the clinic.
Dynamic analysis of prosthetic structures with polymorphic uncertainty
(Third Party Funds Group – Sub project)Overall project: SPP 1886: Polymorphic uncertainty modelling for the numerical design of structures
Term: 2016-01-01 - 2020-09-30
Funding source: DFG / Schwerpunktprogramm (SPP)
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 experimentally acquire material properties and model them as uncertain parameters and capture a walking motion to create an uncertain human leg model. The main part of the proposed research work comprises the further development of the fuzzy simulation methods for forward dynamics and optimal control problems to the presence of polymorphic uncertainty for the analysis of prosthetic structures during design and life cycle. This involves in particular the formulation and solution of uncertain optimisation problems. To keep the computational effort manageable, approximations of the uncertain problems are formulated.
Prosthesis models of increasing material complexity and different types of uncertainty are derived from experimental and computational analysis. The investigation of polymorphic uncertainty on the microstructure and its propagation to the macroscale is planned.
Furthermore, using the LTD's motion capture laboratory, uncertain quantities on model and parameter level, will be determined from analysing human gait trials. For the gait cycle simulation to encompass the entire gait cycle, ground contact, heel strike and toe-off have to be modelled for the complex precurved geometrically exact beam model of the carbon spring foot prosthesis.
Being one of the few projects so far in the SPP 1886 dealing with dynamical systems, the other subprojects will profit from the developed methods when focussing on time-dependent parameters and the change of a structure during its life cycle.
Variational integrators of higher order for constrained systems and variational integrators of mixed order for dynamical systems with multiple time scales
(Own Funds)Term: 2016-01-01 - 2020-10-31
Optimal control of biomechanical MBS-Digital Human Models for simulation in the virtual assembly planning
(Third Party Funds Single)Term: 2015-11-01 - 2018-03-31
Funding source: Industrie
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 instructions are predicted with the help of optimal control, where an objective function accounting for physiological quantities that are relevant for humans is minimized. This new approach enables the user to make quantitative statements about muscle forces and joint loads during assembly, which are important indicators for ergonomic assessment.
Optimal feedback control for constrained mechanical systems
(Own Funds)Term: 2015-01-01 - 2017-01-01
Protein flexibility and conformational ensembles from kino-geometric modeling and sampling to motion planning
(Own Funds)Term: 2014-06-01 - 2019-03-31
Proteins are dynamic macromolecules that perform their biological functions by exchanging between different conformational substates on a broad range of spatial and temporal scales. As the underlying energy landscapes that govern these conformational changes are very rough and often contain high energy barriers, efficient, yet atomically detailed simulations to understand and predict biophysically relevant motions remain challenging.
This project aims at providing functional insights into protein molecular mechanisms from simplified kinematic and geometric modeling. Guided by the covalent bond structure of the molecule, we construct kinematic multi-body systems with dihedral degrees of freedom and non-covalent interactions as constraints, which allows us to efficiently analyze conformational flexibility and deform the protein while maintaining secondary structure. Our analyses show convincing agreement with experimental data from various resources and more detailed Molecular Dynamics simulations, demonstrating the power of kino-geometric models for fast insights into protein flexibility and functional mechanisms, with broad implications for drug design and human health.
Development of artificial muscles as actors and sensors on the basis of dielectric elastomers
(Third Party Funds Group – Sub project)Overall project: bionicum research
Term: 2012-10-01 - 2018-03-31
Funding source: Bayerisches Staatsministerium für Umwelt und Gesundheit (StMUG) (bis 09/2013), Bayerisches Staatsministerium für Umwelt und Verbraucherschutz (StMUV) (ab 10/2013)
The aim of the research project is to provide the basis for a new generation of robotic solutions through the use of Dielectric Elastomer Actuators (DEA) as artificial muscles, covering a broad range of applications from intrinsically safe service robots to highly dynamic mobile kinematics to bionic prostheses. For this purpose, the subareas of automated production of actuators, control electronics and simulation are considered in more detail. On the basis of the aerosol jet printing, a process can be qualified which produces additive and planarized dielectric elastomer actuators and sensors. In the field of power electronics, a simultaneous evaluation and control of DEA based on a central energy source is being developed. This allows the use of multiple DEA as self-sensing actuators. An electromechanically coupled simulation model allows the investigation and optimal control of robotic kinematics that are driven by artificial muscles.
Multiobjective optimal control of hybrid systems
(Own Funds)Term: 2012-01-01 - 2016-01-01
Numerical investigations on optimal control and variational integrators for multirate systems
(Own Funds)Term: 2012-01-01 - 2017-12-31
Space time discretization for flexible multibody systems and multisymplectic variational integrators
(Own Funds)Term: 2011-10-01 - 2018-09-30
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 are carried over to the discrete setting which leads to the conservation of the associated discrete momentum maps. Furthermore, variational integrators show a very good energy behaviour, i.e. they do not artificially dissipate or gain total energy in a conservative system.
Phase lag analysis of variational integrators using interpolation techniques
(Own Funds)Term: 2011-01-01 - 2013-01-01
Complex frequency response for linear viscoelastic beams of Kelvin-Voigt type
(Own Funds)Term: since 2011-01-01
Simulation and optimal control of the dynamics of multibody systems in biomechanics and robotics
(Third Party Funds Single)Term: 2008-12-01 - 2011-12-01
Funding source: DFG-Einzelförderung / Emmy-Noether-Programm (EIN-ENP)
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, the energy required to perform a motion is a criterion of interest, the use of an energy consistent method is crucial. In purely forward dynamical simulations, here mechanical integrators are widely accepted. This project aims to develop and investigate new efficient and robust methods for the dynamic optimisation of movements that guarantee the inheritance of the real solution’s relevant properties by the approximated solution. The developed methods are applied to varying fields. Multirate integrators are developed that simulate different system parts with individual time steps saving computational time while accuracy remains unchanged. To realistically simulate motions of the human arm, Hill-type muscle models actuate the limbs. A semi-analytic algorithm approximating the muscle path allows its use in optimal control problems with physiologically motivated cost functions. Everyday motions like operating a steering wheel or lifting a weight, as well as sports motions like long throw and shot put, are optimised. Another main point is the simulation of the lower extremities. The modelled limbs are actuated by joint torques and contact problems where inelasticities and friction are taken into account. Monopedal jumping and human gait are investigated. Changing between open and closed kinematic loops (double stance phase versus swing phase) is described by different holonomic constraints that are active or passive in different phases. For the example of optimising a pole vault, the introduced method is applied to a flexible multibody system. It is shown that the developed methods are very effective and flexible and therefore a variety of problems can be investigated ranging from robotics over everyday human motion to athletics’ high performance motions.