| 1. |
- Lööf, Johan, 1979, et al.
(författare)
-
An Efficient Solution to the Discrete Least-Cost Tolerance Allocation Problem with General Loss Functions
- 2007
-
Ingår i: Models for Computer Aided Tolerancing Design and Manufacturing. - Dordrecht : Springer Netherlands. - 1402054378
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The tolerance allocation problem consists of choosing tolerances on dimensions of a complex assembly so that they combine into an optimal state while retaining certain requirements. This optimal state often coincides with the minimum manufacturing cost of the product. Sometimes it is balanced with an artificial cost that the deviation from target induces on the quality of the product.This paper analyses and suggests a solution to the discrete allocation problem. It also extends the problem to include treating general loss functions. General loss in this paper means an arbitrary polynomial function of a certain degree. We also briefly review the current work that has been made on solving the tolerance allocation problem.
|
|
| 2. |
- Lööf, Johan, 1979, et al.
(författare)
-
An Efficient Solution to the Discrete Least-Cost Tolerance Allocation Problem With General Loss Functions
- 2005
-
Ingår i: The 9th CIRP International Seminar on Computer Aided Tolerancing, April 11-12, Tempe, Arizona, USA.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The tolerance allocation problem consists of choosing tolerances on dimensions of a complex assembly so that they combine into an optimal state while retaining certain requirements. This optimal state often coincides with the minimum manufacturing cost of the product. Sometimes it is balanced with an artificial cost that the deviation from target induces on the quality of the product.This paper analyses and suggests a solution to the discrete allocation problem. It also extends the problem to include treating general loss functions. General loss in this paper means an arbitrary polynomial function of a certain degree. We also briefly review the current work that has been made on solving the tolerance allocation problem.
|
|
| 3. |
|
|
| 4. |
- Carlson, Johan, 1972, et al.
(författare)
-
Robot Station Optimization for Minimizing Dress Pack Problems
- 2016
-
Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 44, s. 389-394
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 5. |
- Dörlich, Vanessa, et al.
(författare)
-
Localized Helix Configurations of Discrete Cosserat Rods
- 2019
-
Ingår i: Proceedings of the 9th ECCOMAS Thematic Conference on Multibody Dynamics. - Cham : Springer International Publishing. ; , s. 191-198
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 6. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Automatic assembly path planning for wiring harness installations
- 2013
-
Ingår i: Journal of Manufacturing Systems. - : Elsevier BV. - 0278-6125. ; 32:3, s. 417-422
-
Tidskriftsartikel (refereegranskat)abstract
- 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-freemounting of connectors in a wiring harness installation. Automatic path planning for deformable objectsin general is widely acknowledged as a very difficult problem. To overcome this challenge, we propose alow-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 implementedand successfully applied to an industrial test case.
|
|
| 7. |
|
|
| 8. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Automatic routing of flexible 1D components with functional and manufacturing constraints
- 2016
-
Ingår i: CAD Computer Aided Design. - : Elsevier BV. - 0010-4485. ; 79, s. 27-35
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 9. |
- Hermansson, Tomas, 1979
(författare)
-
Computational Methods for Deformable 1D Objects in Virtual Product Realization
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In industry today, virtual design tools are used in the realization of a new product. As changes in the design and planning concepts are extremely costly in the later verification and production phases, much can be gained if a product design can be optimized and verified with respect to the assembly process with simulation tools as early as possible. A topic of special interest is the virtual preparation of deformable 1D objects such as electrical cables and wiring harnesses, hoses, pipes and tubes. They are geometrically characterized as one-dimensional in the sense that one dimension is significantly larger than the other two and can deform when subject to external forces and moments. These types of flexible components are usually located where there is restricted design space and are often associated with quality problems and late on-line adjustments due to geometrical interference. Hence, there is a strong motivation to further strengthen the virtual product realization process in this area. This thesis will present three computational methods for geometrical design and verification of deformable 1D objects. The main scientific challenge is to deal with the complexity of coupling a simulation model with iterative algorithms for optimization, path planning and variation simulation in an efficient way. The methods rely on a simulation model based on Cosserat rod theory that enables efficient and accurate computations of large spatial deformations of flexible 1D objects. The first method solves the problem of routing a deformable 1D object with respect to geometrical design constraints. The method is segregated in a deterministic grid search step and a simulation-based local optimization step. The second method solves the assembly verification problem for a deformable 1D object with a given design. If the verification is true, the method produces a smooth manipulation of a set of grip points that installs the object in the target configuration. The third and final method is in fact a methodology for performing analysis and visualization of geometrical variation in a deformable 1D object. Here, the main innovation is the construction of a discrete envelope for given tolerances based on convex hull computations and silhouette generation. Together, the three methods form a powerful tool set for geometrical design and verification. Quality problems and geometrical interference in the assembled product can now to a larger extent be addressed in the concept phase, thus saving significant development time and reducing the number of iterations between the design phase and the planning and verification phases. The methods are implemented as an integral part in the commercial software IPS Cable Simulation as of version 3.1 (2016).
|
|
| 10. |
- Hermansson, Tomas, 1979
(författare)
-
Computational Methods for Design, Planning and Verification regarding Deformable 1D Objects
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The industry of today is focused on using virtual tools in the realization of new products. As late changes in a design and planning concept can be extremely costly, there are many benefits to discovering and addressing problems as early as possible: fewer iterations between the different product realization phases and shorter lead-times, reduced numbers of physical prototypes and test series, fewer on-line adjustments in the production system and, in the end, a product of a higher quality. A topic of special interest is design, planning and verification regarding deformable 1D objects, such as electrical cables, wiring harnesses, hoses, pipes and tubes. These objects are geometrically characterized as one-dimensional (1D) in the sense that one dimension is significantly larger than the other two. Therefore, they usually exhibit large deformations when subject to external forces and moments, which may cause quality problems and unexpected geometrical interference between objects both in production and during the life-span of a product. Hence, it is of great industrial impact if problems with deformation can be addressed early in the virtual product realization process. This thesis presents five computational methods for design, planning and verification regarding deformable 1D objects. The first two methods are targeted at routing design, i.e. finding a reference design and a routed configuration: one method for objects such as cables that may be significantly deformed due to gravity in their routed configurations and another method for preformed hoses that are not significantly deformed. The third method is in fact a methodology for performing variation analysis that in particular includes a method for generating tolerance envelopes. The fourth method is aimed at assembly verification, whereas the fifth method is aimed at production planning by performing path optimization for an industrial robot with a deformable dress pack. In summary, the methods allow for automatically finding a routed design, verifying the routed design with respect to both geometrical variation and assembly and improving operations in production with respect to deformation. The main research challenge in developing the methods is to combine simulation of deformable 1D objects with iterative algorithms for path planning, variation simulation and optimization. For this purpose, a discrete Cosserat rod model is used to enable efficient and accurate computations of large deformations.
|
|
| 11. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Geometric variation simulation and robust design for flexible cables and hoses
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. - : SAGE Publications. - 0954-4054 .- 2041-2975. ; 226:5, s. 681-689
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents how to do stability analysis, variation simulation and tolerance envelopes for deformable cables andhoses. In this way, the well-established methods for analyzing and minimizing the propagation of geometric variation areextended from rigid and sheet metal assemblies to large deformations of slender parts. This extension is highly moti-vated, not at least, by the increased amount of cables and hoses in electrified and hybrid solutions in the automotiveindustry. To secure the geometric correctness of the analysis, we use a nonlinear rod approach in the implementation ofa simulation model of flexible cables that accounts for large deformations and supports a wide range of common cableclip types, cable joints and branches. A selection of measures and visualizations that reflect the spatial effects of geo-metric variation in deformable cables is incorporated in established variation analysis techniques. In particular, the con-cept of tolerance envelopes for rigid parts has been extended to also handle system of slender parts such as cables andhoses. This article extends previous research on robust design and variation simulation to cables subject to large defor-mations and has been successfully applied on two typical industrial cases: a wiring harness attached with various types ofclips to a static surrounding and a cooler hose subjected to a high-frequency sampled engine motion.
|
|
| 12. |
|
|
| 13. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Identification of Material Parameters of Complex Cables from Scanned 3D Shapes
- 2016
-
Ingår i: Procedia CIRP: 14th CIRP CAT 2016 - CIRP Conference on Computer Aided Tolerancing. - : Elsevier BV. - 2212-8271. ; 43, s. 280-285
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 14. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Quasi-static path optimization for industrial robots with dress packs
- 2021
-
Ingår i: Robotics and Computer-Integrated Manufacturing. - : Elsevier BV. - 0736-5845. ; 68
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 15. |
- Hermansson, Tomas, 1979, et al.
(författare)
-
Routing of curves with piecewise constant curvature applied to routing of preformed hoses
- 2021
-
Ingår i: CAD Computer Aided Design. - : Elsevier BV. - 0010-4485. ; 139
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 16. |
- Karlsson, Tobias, et al.
(författare)
-
Automatic Cable Harness Layout Routing in a Customizable 3D Environment
- 2024
-
Ingår i: CAD Computer Aided Design. - 0010-4485. ; 169
-
Tidskriftsartikel (refereegranskat)abstract
- Designing cable harnesses can be time-consuming and complex due to many design and manufacturing aspects and rules. Automating the design process can help to fulfil these rules, speed up the process, and optimize the design. To accommodate this, we formulate a harness routing optimization problem to minimize cable lengths, maximize bundling by rewarding shared paths, and optimize the cables’ spatial location with respect to case-specific information of the routing environment, e.g., zones to avoid. A deterministic and computationally effective cable harness routing algorithm has been developed to solve the routing problem and is used to generate a set of cable harness topology candidates and approximate the Pareto front. Our approach was tested against a stochastic and an exact solver and our routing algorithm generated objective function values better than the stochastic approach and close to the exact solver. Our algorithm was able to find solutions, some of them being proven to be near-optimal, for three industrial-sized 3D cases within reasonable time (in magnitude of seconds to minutes) and the computation times were comparable to those of the stochastic approach.
|
|
| 17. |
- Linn, Joachim, et al.
(författare)
-
Kinetic Aspects of Discrete Cosserat Rods
- 2017
-
Ingår i: Proceedings of the 8th ECCOMAS Thematic Conference on Multibody Dynamics.
-
Konferensbidrag (refereegranskat)abstract
- 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 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).
|
|
| 18. |
- Schneider, Fabio, et al.
(författare)
-
Cable Dynamics and Fatigue Analysis for Digital Mock-Up in Vehicle Industry
- 2017
-
Ingår i: Proceedings of the 8th ECCOMAS Thematic Conference on Multibody Dynamics.
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
