Johannes Gerstmayr

• Univ.-Prof. DI Dr. techn.
• Professor (Full) at University of Innsbruck

The precision, stability, and performance of lightweight high-strength steel structures in heavy machinery is affected by their highly nonlinear dynamics. This, in turn, makes control more difficult, simulation more computationally intensive, and achieving real-time autonomy, using standard approaches, impossible. Machine learning through data-driv...

This work focuses on compliant joints in autonomous cells. These cells are able to preserve the underlying geometry of a mesh and enable self-reconfiguration through the utilization of six-bar linkages. The six-bar linkages, essential for maintaining triangular mesh geometry, are realized as 3D-printable compliant mechanisms. However, challenges ar...

The algorithms identifying machine health and predicting maintenance needs require accurate information about the machine’s state. Because of the great amount of collected data and limited data buffering and data transfer capabilities in many hydraulic machinery applications, the data should be processed in real time. The real-time requirement dema...

Understanding particle motion in snow avalanches is essential for unravelling the driving processes behind transport phenomena and mobility. Our approach to investigating avalanche dynamics at the particle level combines data from a novel inflow sensor system, the AvaNodes, with radar measurements and simulation results from the thickness integrate...

In computational engineering, enhancing the simulation speed and efficiency is a perpetual goal. To fully take advantage of neural network techniques and hardware, we present the SLiding-window Initially-truncated Dynamic-response Estimator (SLIDE), a deep learning-based method designed to estimate output sequences of mechanical or multibody system...

Laminated plates have a wide range of applications in engineering, and their flexibility becomes increasingly significant with the development of lightweighting technology. The absolute nodal coordinate formulation (ANCF) has emerged as a promising approach for modeling flexible multibody dynamics. However, researches on thick laminated plates with...

The present contribution introduces the task-dependent comfort zone as a base placement strategy for mobile manipulators using different manipulability measures. Four different manipulability measures depending on end-effector velocities, forces, stiffness, and accelerations are considered. By evaluating a discrete subspace of the manipulator works...

The present contribution introduces the task dependent comfort zone as a base placement strategy for mobile manipulators using different manipulability measures. Four different manipulability measures depending on end-effector velocities, forces, stiffness, and accelerations are considered. By evaluating a discrete subspace of the manipulator works...

Over the years, complex control approaches have been developed to control the motion of a bicycle. Reinforcement Learning (RL), a branch of machine learning, promises easy deployment of so-called agents. Deployed agents are increasingly considered as an alternative to controllers for mechanical systems. The present work introduces an RL approach to...

The present contribution introduces the task dependent comfort zone as a base placement strategy for mobile manipulators using different manipulability measures. Four different manipulability measures depending on end-effector velocities, forces, stiffness, and accelerations are considered. By evaluating a discrete subspace of the manipulator works...

Modular self-reconfigurable robots hold the promise of being capable of performing a wide variety of tasks. However, many systems fall short of either delivering this promised functionality due to constraints in system architecture or validating it on functional hardware prototypes. This paper demonstrates the functional capabilities of the Planar...

As commonly known, standard time integration of the kinematic equations of rigid bodies modeled with three rotation parameters is infeasible due to singular points. Common workarounds are reparameterization strategies or Euler parameters. Both approaches typically vary in accuracy depending on the choice of rotation parameters. To efficiently compu...

Computational models are conventionally created with input data, script files, programming interfaces, or graphical user interfaces. This paper explores the potential of expanding model generation, with a focus on multibody system dynamics. In particular, we investigate the ability of Large Language Model (LLM), to generate models from natural lang...

Reinforcement learning (RL) is one of the emerging fields of artificial intelligence (AI) intended for designing agents that take actions in the physical environment. RL has many vital applications, including robotics and autonomous vehicles. The key characteristic of RL is its ability to learn from experience without requiring direct programming o...

Computational models are conventionally created with input data, script files, programming interfaces, or graphical user interfaces. This paper explores the potential of expanding model generation, with a focus on multibody system dynamics. In particular, we investigate the ability of Large Language Models (LLMs), to generate models from natural la...

Motion reconstruction and navigation require accurate orientation estimation. Modern orientation estimation methods utilize filtering algorithms, such as the Kalman filter or Madgwick's algorithm. However, these methods do not address potential sensor saturation, which may occur within short time periods in highly dynamic applications, such as, e.g...

This work focuses on the modeling of contact between sheaves and flexible axially moving beams. A two-dimensional beam finite element is employed, based on the absolute nodal coordinate formulation (ANCF) with an improved selective reduced integration for the virtual work of elastic and viscous damping forces. For the efficient modeling of contact...

The present contribution introduces the design, methods, functionalities, and capabilities of the open-source multibody dynamics code Exudyn, which has been developed since 2019. The code has been designed for rigid and flexible multibody systems, with a focus on performance for multicore desktop processors. It includes script-language-based modeli...

Programmable mechanical structures are formed by autonomous and adaptive cells and can reproduce meshes known from the finite element method. Furthermore, they can change their structure not only through morphing, but also by self-reconfiguration of the cells. A crucial component of the cells, which can preserve the underlying geometry of a triangu...

Reinforcement Learning (RL) is one of the emerging fields of Artificial Intelligence (AI) intended for designing agents that take actions in the physical environment. RL has many vital applications, including robotics and autonomous vehicles. The key characteristic of RL is its ability to learn from experience without requiring direct programming o...

Corotational formulations play an important role for flexible multibody dynamics systems, because they reflect the nature of many technical systems undergoing arbitrarily large rigid body motions but small deformations within each body. This paper defines flexible multibody dynamics and corotational formulations in this context. Furthermore, the «i...

This work focuses on the modeling of contact between sheaves and flexible axially moving beams. A two-dimensional beam finite element is employed, based on the absolute nodal coordinate formulation (ANCF) with an improved selective reduced integration for the virtual work of elastic and viscous damping forces. For the efficient modeling of contact...

This paper presents the approach of the RoboCup@Work team tyrolics of the university of Innsbruck to design, develop and build a mobile manipulator with 10 degrees of freedom. The mobile manipulator LeoBot uses Mecanum wheels to enable omnidirectional movement and includes a Franka Emika Panda serial manipulator. This paper focuses on hardware deve...

The present contribution introduces the design, methods, functionalities and capabilities of the open source multibody dynamics code Exudyn, which has been developed since 2019. The code has been designed for rigid and flexible multibody systems, with focus on performance for regular multi-core CPUs. It includes script language based modeling and i...

The dynamics of linearly-elastic multibody (MB) systems is conventionally modeled via the floating frame of reference formulation (FFRF); however, its equations of motion (EOMs) involve significantly more nonlinear terms and quantities than alternative formulations, such as the absolute coordinate formulation (ACF) and generalized component mode sy...

Motion reconstruction for rigid bodies and rigid-body frames using data from inertial measurement units (IMUs) is a challenging task. Position and orientation determination by means of IMUs is erroneous, as deterministic and stochastic errors accumulate over time. The former of which errors can be minimized by standard calibration approaches, howev...

The distribution of the contact pressure occurring under the edge of a snowboard during a carved turn is a key factor influencing the riding behaviour. These interface loads are determined by the structural design, and in particular by the sidecut geometry of the edge line. In this study, the following inverse problem was set under investigation: i...

The Nordkette laboratory has been home to various aspects of avalanche research due to its proximity and accessibility. Lately performed inflow avalanche measurements at the Nordkette laboratory were evaluated to investigate the internal dynamics of avalanches and provide data to test corresponding simulation models. The used measuring system, call...

This paper presents the approach of the RoboCup@Work team tyrolics of the university of Innsbruck to design, develop and build a mobile manipulator with 10 degrees of freedom. The mobile manipu-lator LeoBot uses Mecanum wheels to enable omnidirectional movement and includes a Franka Emika Panda serial manipulator. This paper fo-cuses on hardware de...

Mithilfe sogenannter Mecanumräder kann ein omnidirektionaler Antrieb realisiert werden. Diese oftmals in Robotersyste- men und fahrerlosen Transportsystemen eingesetzten Räder ermöglichen es Fahrzeugen sowohl eine ebene translatorische Bewegung als auch eine Drehung um die Hochachse auszuführen. Dies ermöglicht beliebige Trajektorien und eine freie...

The accuracy of a multibody model to predict the behavior of a real physical system depends heavily on the correct choice of model parameters. Identifying unknown system parameters that cannot be computed or measured directly is usually time-consuming and costly. If measurement data is available for the physical system, the parameters in the corres...

The present work addresses pipes conveying fluid and axially moving beams undergoing large deformations. A novel two dimensional beam finite element is presented, based on the Absolute Nodal Coordinate Formulation (ANCF) with an extra Eulerian coordinate to describe axial motion. The resulting formulation is well known as Arbitrary Lagrangian Euler...

Three rotation parameters are commonly used in multibody dynamics or in spacecraft attitude determination to represent large spatial rotations. It is well known, however, that the direct time integration of kinematic equations with three rotation parameters is not possible in singular points. In standard formulations based on three rotation paramet...

The present paper investigates the static equilibrium of a thin elastic structure with concave sidecut pressed against a flat rigid surface, as an idealization of a ski or snowboard undergoing the conditions of a carved turn. An analytical model is derived to represent the contact behaviour and provide an explanation for concentrated loads occurrin...

In this paper, we present a reconfiguration algorithm for shape-shifting modular robots with a triangular structure. The algorithm is derived from a novel description of the configuration space based on extended binary trees. Extended binary trees representing the same configuration are grouped into equivalence classes, which allows for a one-to-on...

The ability of a multibody dynamics model to accurately predict the behavior of a real system depends heavily on the correct choice of model parameters. The identification of unknown system parameters, which cannot be directly computed or measured is usually time consuming and costly. If experimental measurement data of the real system is available...

Mobile robots and autonomous guided vehicles have become an indispensable part of modern industrial environments and are used for a wide range of handling operations. To fully use the potential of mobile platforms, omnidirectional platforms are a good choice. A prominent and widely used variant in the industry are Mecanum wheels, which allow arbitr...

The present paper addresses axially moving beams with co-moving concentrated masses while undergoing large deformations. For the numerical modeling, a novel beam finite element is introduced, which is based on the absolute nodal coordinate formulation extended with an additional Eulerian coordinate to represent the axial motion. The resulting formu...

The goal of the present paper is to investigate inertial measurement systems for the ability to reconstruct the short time rigid body motion of objects, e.g. clumps in snow avalanches. While strapdown inertial navigation is well established, special algorithms are needed for the accurate motion reconstruction for short time motion with partially kn...

Team Description Paper for the mobile manipulator Leobot, build by the RoboCup@work team Tyrolics from the Univercity of Innsbruck

We consider the trajectory tracking optimization for an elastic joint robot with noisy joint-velocity readings and actuation torque limits. We propose an approach targeting the minimization of the trajectory tracking error, of the velocity noise amplification on the control commands, and of the trajectory execution time. We integrate the use of a f...

In a recent paper of the authors, a novel nodal-based floating frame of reference formulation (FFRF) for solid finite elements has been proposed. The nodal-based approach bypasses the unhandy inertia shape integrals ab initio, i.e. they neither arise in the derivation nor in the final equations of motion, leading to a surprisingly simple derivation...

Flexible multibody dynamics systems based on 3D continuum finite elements are important for industrial research but usually require time consuming implementations in research codes. The conventional continuum-mechanics-based floating frame of reference formulation (FFRF) is usually employed for these applications. However, the conventional approach...

Rigid bodies are an essential part of multibody systems. As there are six degrees of freedom in rigid bodies, it is natural but also precarious to use three parameters for the displacement and three parameters for the rotation parameters - since there is no singularity-free description of spatial rotations based on three rotation parameters. Standa...

Programmable structures are formed by autonomous and adaptive triangular cells. However, they are composed of a large number of parts, specifically bearings, which make them laborious to manufacture and expensive. An essential part of these programmable structures are six-bar linkages, which allow to build cells that can preserve the underlying geo...

The conventional continuum-mechanics-based floating frame of reference formulation involves unhandy so-called inertia-shape-integrals in the equations of motion, which is why, commercial multibody software codes resort to a lumped mass approximation to avoid the evaluation of these integrals in their computer implementations. This paper recaps the...

The Floating Frame of Reference Formulation (FFRF) is one of the most widely used methods to analyze flexible multibody systems subjected to large rigid-body motion but small strains and deformations. The FFRF is conventionally derived via a continuum mechanics approach. This tedious and circuitous approach, which still attracts attention among res...

EXUDYN is a C++ based Python library for efficient simulation of flexible multibody dynamics systems. It is designed to easily set up complex multibody models, consisting of rigid and flexible bodies with joints, loads and other components. It shall enable automized model setup and parameter variations, which are often necessary for system design b...

Motivated by an application example, the comfort zone for mobile kinematically redundant manipulators is defined. The position and orientation of the mobile platform (=base of the manipulator) and the joint angles are selected in such a way that selected target functions are minimized. These objective functions are derived from known measures such...

EXUDYN Documentation

A novel formulation for the description of spatial rigid body motion using six non-redundant, homogeneous local velocity coordinates is presented. In contrast to common practice, the formulation proposed here does not distinguish between a translational and rotational motion in the sense that only translational velocity coordinates are used to desc...

This paper presents a novel system‐level model order reduction scheme for flexible multibody simulation, namely the system‐level affine projection (SLAP). Contrary to existing system‐level model order reduction approaches for multibody systems simulation, this methodology allows to obtain a constant reduced order basis which can be obtained in a no...

In this paper, we present a formulation for the dynamic analysis of multibody systems using non‐redundant unified local velocity coordinates. The motivation for the present work is the result of an earlier investigation of unified local velocity coordinates of Holzinger et al. [1]. The equations of motion presented by the authors allow the descript...

The trend away from physical towards virtual prototyping as well as increasing industrial demands require advanced simulation tools for dynamical systems. Virtually all engineering systems are assemblies and are associated with stresses, noise and vibrations; therefore, flexible multibody simulations are inevitable for accurate predictions. However...

Zusammenfassung Für die auditive und visuelle Wahrnehmung bieten sogenannte „Virtual Reality“-Systeme eine hochauflösende Nachbildung der Wirklichkeit bei gleichzeitig niedrigen Kosten. Um digitalisierte Objekte noch näher an die Realität zu bringen, werden in dieser Arbeit programmierbare Strukturen vorgestellt, welche neben der visuellen auch die...

Rigid body models are only sufficient for rough estimates of the dynamics of real world systems, such as machines, robots and vehicles. Although, deformations are usually small compared to a rigid body motion, they need to be taken into account in many cases; e.g., to determine vibrations, resonance effects and stresses. So far, there are two main...

The purpose of this study was to define a method for the validation of a numerical model representing a snowboard structure undergoing the conditions of a carved turn. A static load bench was developed to expose a snowboard to in-situ conditions. The deformed shape of the structure was measured with the use of retro-reflective markers, whose positi...

An increasing focus on the optimization of products to higher levels of reliability and efficiency in combination with the growing complexity of our technology dominated world pushes industry away from physical towards virtual prototyping. Which is why, advanced engineering simulation tools have become indispensable to master today's challenges. T...

The reduction in the number of coordinates for flexible multibody systems is necessary in order to achieve acceptable simulation times of real-life structures and machines. The conventional model order reduction technique for flexible multibody systems is based on the floating frame of reference formulation (FFRF), using a rigid body frame and supe...

The use of multibody simulation tools allows complex machinery to be described in detail while still providing a solution for the system in real time. As mechanical components are often accompanied by other dynamical systems, such as hydraulics, description of each subsystem is required to fully describe the dynamics of complex machinery. A potenti...

Increasing industrial demands on reliability and efficiency require advanced simulation models of dynamical systems. Virtually all engineering systems are assemblies made out of multiple components which interact with each other during operation. The forces required to execute desired motions are associated with stresses, noise and vibrations, whic...

Increasing industrial demands require advanced simulation models of dynamical systems. Virtually all engineering systems are assemblies and associated with stresses, noise and vibrations. Hence, flexible multibody simulations are inevitable for accurate predictions. Most real-world FE models contain numerous DOFs that cannot be handled without mode...

A new approach for the transient simulation of idealized ropeway systems is proposed. Therefore, common numerical tools known from flexible multibody dynamics are adapted. The running cable is modelled by means of flexible beam elements in an arbitrary Lagrangian-Eulerian manner. That is, the deformational motion of the cable corresponds to the mot...

A new approach for the transient simulation of idealized ropeway systems is proposed. Therefore, common numerical tools known from flexible multibody dynamics are adapted. The running cable is modelled by means of flexible beam elements in an arbitrary Lagrangian-Eulerian manner. That is, the deformational motion of the cable corresponds to the mot...

The aim of the present paper is to evaluate six particular beam finite elements based on the absolute nodal coordinate formulation (ANCF). Specifically, accuracy, computational efficiency and numerical stability are compared for those beam finite elements. The finite elements under consideration are planar as well as spatial beams, which are formul...

Light-weight structures and high-performance mechanical systems lead to an increasing amount of vibrations. In order to comply with standards in noise and vibration limits, the simula- tion of flexible multibody systems is inevitable. Due to the size of the finite element models of real-life mechanical systems, a model order reduction is necessary...

The paper is concerned with the modeling of the planar motion of a horizontal sheet of metal in a rolling mill. Inhomogeneous velocity profiles, with which the material is generated at one roll stand and enters the next one, lead to the time evolution of the deformation of the metal strip. We propose a novel kinematic description in which the axial...

In industrial practice, the floating frame of reference formulation (FFRF)-often combined with the component mode synthesis (CMS) in order to reduce the number of flexible degrees-of-freedom-is the common approach to describe arbitrarily shaped bodies in flexible multibody systems. Owed to the relative formulation of the flexible deformation with r...

The key idea of the absolute nodal coordinate formulation (ANCF) is to use slope vectors in order to describe the orientation of the cross-section of structural mechanics components, such as beams, plates or shells. This formulation relaxes the kinematical assumptions of Bernoulli–Euler and Timoshenko beam theories and enables a deformation of the...

As the need to model flexibility arose in multibody dynamics, the floating frame of reference formulation was developed, but this approach can yield inaccurate results when elastic displacements becomes large. While the use of three-dimensional finite element formulations overcomes this problem, the associated computational cost is overwhelming. Co...

Modeling the interaction of fluids with moving, flexible structures is a major and still very challenging subject in the field of multi-physics problems. In this work, an efficient computational approach based on the coupling of modally reduced flexible multibody systems with fluids modeled by means of smoothed particle hydrodynamics is outlined.

An established postprocessing procedure for the determination of interlaminar shear and normal stresses based on the results of a conventional shell finite element analysis is generalized for arbitrarily curved laminated shells. The method relies on the three-dimensional equilibrium conditions and an extended lamination theory. Underlying approxima...

Optimizing mechatronic components is of increasing importance, e.g. for minimizing energy consumption and the use of rare materials. MagOpt is a modular software tool for the simulation and optimization of mechatronic components. Parametric design optimization can be carried out with various different optimization strategies like gradient-based met...

The aim of this paper is to highlight and identify the influencing parameters of the nonlinear behavior of highly deformable structures. Therefore, as an example, a large deformable square frame consisting of four slender members of equal length has been investigated experimentally. Based on highly resolving measurements using the digital image cor...

Due to the increase in speed and lightweight construction, modern robots vibrate significantly during motion. Thus, accurate mechanical modeling and detailed controller behavior is essential for accurate path planning and control design of robots. For the suppression of undesired vibrations detailed models are used to develop robust controllers. Le...

An extension of Reissner’s geometrically exact theory for the plane deformation of beams allows a consistent constitutive modeling of various types of material behavior. In the present paper, such formulation is used to describe the coupled response of slender piezoelectric structures. Starting from the local equilibrium relations and the geometric...

In this paper the influencing factors of the nonlinear behavior of a highly deformable square frame are aimed to highlight and identify. Therefore, in a first step a square frame consisting of four slender members of equal length has been investigated experimentally. Subsequently to these investigations, a numerical model is set up with a beam fini...

Simulations of the behaviour of complex mechatronic systems require optimal simulation parameters for obtaining realistic results. For highly accurate mechatronic simulations, an algorithm for searching the optimal parameters is required. In the field of robotics the identification based on minimization of the residuum with least square methods is...