Publications Search Results

Now showing 1 - 10 of 12
  • Publication
    Routing of curves with piecewise constant curvature applied to routing of preformed hoses
    ( 2021)
    Hermansson, T.
    ;
    Ablad, E.
    We present a method for routing of a preformed hose in a static surrounding of obstacles. Routing of a preformed hose is the process of finding a preformed design of the hose that connects a start and a goal point in a collision-free way. A preformed hose design is in this paper represented by a center curve on the form of a sequence of straight line segments joined by circular arcs. The method generates a set of center curves that are collision-free and satisfy minimum allowed straight length and radius of curvature constraints. Each center curve takes a topologically different path with respect to the surrounding geometry and is locally of minimum length. The main scientific contribution is the coupling of a generalized bi-directional grid search with local curve optimization and curve filtering. The method was applied to a set of benchmark cases from the automotive industry and relevant routing solutions were generated in the magnitude of seconds.
  • Publication
    Quasi-static path optimization for industrial robots with dress packs
    ( 2021)
    Hermansson, T.
    ;
    Carlson, J.
    ;
    Linn, J.
    ;
    Kressin, J.
    Problems with robot dress packs are a major reason for on-line adjustments of robot programs and down-time in robot stations. It is therefore of high value if the physical behaviour of the dress packs can be considered with simulation methods already during the off-line programming process for a robot station. This paper presents a method for quasi-static path optimization for an industrial robot with respect to its deformable dress pack. Given an initial collision-free path generated by an automatic path planner, the via point configurations of the path are optimized with respect to the performance aspects of the dress pack. The method is derived from a general framework for parameter optimization of a mechanical system subject to quasi-static motions and deformations. The optimal parameter values are obtained from numerical solutions to a non-linear programming problem in which the static equilibrium equations of the system hold at discrete times. Due to the large-scale nature of this problem, a dress pack is modelled as a discrete Cosserat rod, which is the preferred choice for modeling large spatial deformations of a slender flexible structure with coarse discretization. The method is applied to an industrial robot moving in-between stud welding operations in a stud welding station. The optimized path reduces the stress in the dress pack and keeps the dressed robot from the surrounding geometry with a prescribed safety clearance during the entire robot motion.
  • Publication
    Localized Helix Configurations of Discrete Cosserat Rods
    ( 2020)
    Dörlich, V.
    ;
    Hermansson, T.
    ;
    Linn, J.
    Cosserat rods are the prefered choice for modeling large spatial deformations of slender flexible structures at small local strains. Discrete Cosserat rod models based on geometric finite differences preserve essential properties of the continuum theory. In previous work kinetic aspects of discrete quaternionic Cosserat rods defined on a staggered grid were investigated. In particular it was shown that equilibrium configurations obtained by energy minimization correspond to solutions of finite difference type discrete balance equations for the sectional forces and moments in conservation form. The present contribution complements the numerical studies shown in by considering localized helix configurations of discrete Cosserat rods as more complex benchmark examples.
  • Publication
    Cable dynamics and fatigue analysis for digital mock-up in vehicle industry
    ( 2017)
    Schneider, Fabio
    ;
    Linn, J.
    ;
    Hermansson, T.
    ;
    Andersson, F.
    Numerical simulation has become an important aspect of modern industrial production processes. Very early in the process chain - even before first prototypes are built - simulation is used for digital mock-up in order to discover potential problems and to improve certain components and their assembling. In our work, we focus on the simulation of highly flexible components like cables and hoses, which is a challenging task in vehicle industry. Nowadays, complex harnesses with kilometers of cables can be found in every vehicle and the amount even increases for electric drivelines and hybrid cars. Especially for cables of safety-relevant equipment, high loads and contacts with high friction should be avoided, already during the assembling but also later in regular usage. We present the essential steps of a dynamic cable simulation and a subsequent comparative load data analysis. The latter allows to efficiently compare many different cable configurations in order to identify the best one in the sense of damage.
  • Publication
    Kinetic aspects of discrete cosserat rods based on the difference geometry of framed curves
    ( 2017)
    Linn, J.
    ;
    Hermansson, T.
    ;
    Andersson, F.
    ;
    Schneider, Fabio
    The theory of Cosserat rods provides a self consistent framework for modeling large spatial deformations of slender flexible structures at small local strains. Discrete Cosserat rod models [1, 2] based on geometric finite differences preserve essential properties of the continuum theory. The present work investigates kinetic aspects of discrete quaternionic Cosserat rods defined on a staggered grid within the framework of Lagrangian mechanics. Assuming hyperelastic constitutive behaviour, the Euler-Lagrange equations of the model are shown to be equivalent to the (semi)discrete balance equations of forces, moments and inertial terms obtained from a direct discretization of the continuous balance equations via spatial finite differences along the centerline curve. Therefore, equilibrium configurations obtained by energy minimization correspond to solutions of the quasi-static balance equations. We illustrate this approach by two academic examples (Euler's Elastica and Kirchhoff's helix) and highlight its utility for practical applications with a use case from automotive industry (analysis of the layout of cooling hoses in the engine compartment of a passenger car).
  • Publication
    Robot station optimization for minimizing dress pack problems
    ( 2016)
    Carlson, J.S.
    ;
    Kressin, J.
    ;
    Hermansson, T.
    ;
    Bohlin, R.
    ;
    Sundbäck, M.
    ;
    Hansson, H.
    Problems with robot dress packs are one of the major reasons for online adjustments of robot motions and for down time in robot stations. A factory study showed that many robots wear out more than one dress pack per year. The life length variation was in fact shown considerable, ranging from years to only months. The dress packs consist of attached cables and hoses which typically have significant impact on allowed robot configurations and motions in the station. In this paper, we present novel simulation methods for improving robot configurations and motions during off-line programming and optimization of robot stations. The proposed method is applied to a stud welding station resulting in the elimination of several problems related to the dress packs.
  • Publication
    Automatic routing of flexible 1D components with functional and manufacturing constraints
    ( 2016)
    Hermansson, T.
    ;
    Bohlin, R.
    ;
    Carlson, J.S.
    ;
    Söderberg, R.
    This article presents a novel and unifying method for routing of flexible one-dimensional components such as cables, hoses and pipes with geometric design constraints. A deterministic and resolution complete grid search is used to find a nominal configuration of the component that is collision-free and satisfies functional and manufacturing constraints. Local refinement is done in tandem with a computationally efficient and physically accurate simulation model based on Cosserat rod theory to ensure that the deformed configuration still satisfies functional constraints when influenced by gravity. Test results show that the method is able to solve industrial scenarios involving complex geometries and real constraints with different objectives in mere seconds.
  • Publication
    Identification of material parameters of complex cables from scanned 3D shapes
    ( 2016)
    Hermansson, T.
    ;
    Vajedi, S.
    ;
    Forsberg, T.
    ;
    Ekstedt, F.
    ;
    Kressin, J.
    ;
    Toft, C.
    ;
    Carlson, J.S.
    Simulation of flexible components is becoming an integral part of virtual product design. However, for a simulation model to predict physically correct deformations, it is crucial that the material parameters are authentic. Conventional methods to acquire these parameters involve extensive force-displacement measurements, which may be unpractical or too expensive to perform. We propose an alternative method to identify the material parameters of a flexible one-dimensional component, such as a cable or a hose, from a scanned set of deformed reference shapes. The method finds the model parameters that give the best geometric fit between the model and the reference shapes.
  • Publication
    Geometric variation simulation and robust design for flexible cables and hoses
    ( 2013)
    Hermansson, T.
    ;
    Carlson, J.S.
    ;
    Björkenstam, S.
    ;
    Söderberg, R.
    This article presents how to do stability analysis, variation simulation and tolerance envelopes for deformable cables and hoses. In this way, the well-established methods for analyzing and minimizing the propagation of geometric variation are extended from rigid and sheet metal assemblies to large deformations of slender parts. This extension is highly motivated, not at least, by the increased amount of cables and hoses in electrified and hybrid solutions in the automotive industry. To secure the geometric correctness of the analysis, we use a nonlinear rod approach in the implementation of a simulation model of flexible cables that accounts for large deformations and supports a wide range of common cable clip types, cable joints and branches. A selection of measures and visualizations that reflect the spatial effects of geometric variation in deformable cables is incorporated in established variation analysis techniques. In particular, the concept of tolerance envelopes for rigid parts has been extended to also handle system of slender parts such as cables and hoses. This article extends previous research on robust design and variation simulation to cables subject to large deformations and has been successfully applied on two typical industrial cases: a wiring harness attached with various types of clips to a static surrounding and a cooler hose subjected to a high-frequency sampled engine motion.
  • Publication
    Automatic assembly path planning for wiring harness installations
    ( 2013)
    Hermansson, T.
    ;
    Bohlin, R.
    ;
    Carlson, J.S.
    ;
    Söderberg, R.
    The automotive industry of today is becoming more focused on electrified and hybrid solutions, where both conventional combustion engines and battery supplied electrical engines need to fit in an already densely packed vehicle. Many quality problems are related do flexible parts. In particular, the assembly of electric cables and wiring harnesses is difficult due to its concealed routing, multiple branching points, weights and the flexibility in the material. To avoid late detection of assembly problems, the assembly aspect must be considered early during conceptual design and production preparation with respect to both feasibility and ergonomics. Development of automatic path planning methods in virtual manufacturing tools supporting deformable parts is therefore highly motivated. This article presents a novel method for automatically planning and finding a smooth and collision-free mounting of connectors in a wiring harness installation. Automatic path planning for de formable objects in general is widely acknowledged as a very difficult problem. To overcome this challenge, we propose a low-dimensional path planning algorithm that operates in the following way: constraint relaxation, handle path planning, unfolding, path smoothing and handle supplementation. The method has been implemented and successfully applied to an industrial test case.