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Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
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Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
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Asian Journal of Biotechnology     Open Access   (Followers: 8)
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Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
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Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
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Beyond : Undergraduate Research Journal     Open Access  
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Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
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Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
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Canadian Geotechnical Journal     Hybrid Journal   (Followers: 31)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 42)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Thermal Engineering     Open Access   (Followers: 5)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
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Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 7)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal  
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 3)
CienciaUAT     Open Access   (Followers: 1)
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 13)
City, Culture and Society     Hybrid Journal   (Followers: 21)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 1)
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Coastal Engineering Journal     Hybrid Journal   (Followers: 6)
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Cogent Engineering     Open Access   (Followers: 2)
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        1 2 3 4 5 6 7 | Last

Journal Cover Assembly Automation
  [SJR: 0.657]   [H-I: 26]   [2 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0144-5154
   Published by Emerald Homepage  [335 journals]
  • A variational model for 3D tolerance analysis with manufacturing signature
           and operating conditions
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this work is to present a variational model able to deal with form tolerances and assembly conditions. The variational model is one of the methods proposed in literature for tolerance analysis, but it cannot deal with form tolerances and assembly conditions that may influence the functional requirements of mechanical assemblies. Design/methodology/approach This work shows how to manage the actual surfaces generated by the manufacturing process and the operating conditions inside the variational model that has been modified to integrate the manufacturing signature left on the surfaces of the parts and the operating conditions that arise during an actual assembly, such as gravity and friction. Moreover, a geometrical model was developed to numerically simulate what happens in a real assembly process and to give a reference value. Findings The new variational model was applied to a three-dimensional case study. The obtained results were compared to those of the geometrical model and to those of the variational model to validate the new model and to show the improvements. Research limitations/implications The proposed approach may be extended to other models of literature. However, its limitation is that it is able to deal with a sphere–plane contact. Practical implications Tolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly before getting the physical assembly. It involves a decrease in the manufacturing costs. Originality/value The main contributions of the study are the insertion of a systematic pattern characterizing the features manufactured by a process, assembly operating conditions and development of a geometrical model to reproduce what happens in a real assembly process.
      Citation: Assembly Automation
      PubDate: 2018-01-10T12:09:50Z
      DOI: 10.1108/AA-01-2017-006
  • C2-continuous orientation trajectory planning for robot based on spline
           quaternion curve
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose To realize the smooth interpolation of orientation on robot end-effector, this paper aims to propose a novel algorithm based on the unit quaternion spline curve. Design/methodology/approach This algorithm combines the spherical linear quaternion interpolation and the cubic B-spline quaternion curve. With this method, a C2-continuous smooth trajectory of multiple teaching orientations is obtained. To achieve the visualization of quaternion curves on a unit sphere, a mapping algorithm between a unit quaternion and a point on the spherical surface is given based on the physical meaning of the unit quaternion. Findings Finally, the curvature analysis of a practical case shows that the orientation trajectory (OT) constructed by this algorithm satisfied the C2-continuity. Originality/value This OT satisfies the requirement of smooth interpolation among multiple orientations on robots in industrial applications.
      Citation: Assembly Automation
      PubDate: 2018-01-10T11:52:47Z
      DOI: 10.1108/AA-04-2017-050
  • Research and design of a multi-fingered hand made of hyperelastic material
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this study is to provide a novel multi-fingered hand made of hyperelastic material. This kind of hand has the advantage of less mechanical parts, simpler control system. It can greatly cut down the complexity and cost of the hands under conditions of ensuring enough flexibility of grasping. Design/methodology/approach Based on the principle of virtual work, the equations of pulling force and grasping force are derived. To get the max grasping force, the optimal structural dimensions of the hand are obtained by finite element simulations. Hand’s grasping experiment is conducted. Findings The factors influencing grasping force and grasping stability are identified, and they are the length between short poles around the knuckles and the height of short poles. Experimental results show that the max strain of knuckles is less than the elastic limit of hyperelastic material, and the presented hand is practicable. The adaptive ability and grasping stability of the presented hand are demonstrated. Originality/value A novel multi-fingered hand made of hyperelastic material is presented in this paper. By designing the thickness of every section of a hyperelastic plate, the knuckle sections will bend and other sections of the plate will remain straight, and thus, the multi-fingered hand will grasp.
      Citation: Assembly Automation
      PubDate: 2018-01-08T03:03:54Z
      DOI: 10.1108/AA-03-2017-042
  • A multi-vision-based system for tube inspection
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose Geometric errors are common in metallic bent tubular parts. Thus, tubes should be inspected and fixed before welding with the joints first. After welding, the relative position of the joints is also necessary to be inspected to judge whether the tube can be assembled reliably. Therefore, the inspection plays an important role in the tube’s assembly. The purpose of this paper is to propose a multi-vision-based system designed to inspect the tube and the relative position of the joints. Design/methodology/approach For the tube inspection, the small cylinders are taken as the primitives to reconstruct the tube using the multi- vision-based system. Then, any geometric error in the tube can be inspected by comparing the reconstructed models and designed ones. For joints’ inspection, authors designed an adapter with marked points, by which the system can calculate the relative position of the joints. Findings The reconstruction idea can recognise the line and arc segments of a tube automatically and resolve the textureless deficiency of the tube’s surface. The joints’ inspection method is simple in operation, and any kinds of joints can be inspected by designing the structure of the adapters accordingly. Originality/value By experimental verification, the inspection precision of the proposed system was 0.17 mm; the inspection time was within 2 min. Thus, the system developed can inspect a tube effectively and automatically. Moreover, authors can determine how the springback of the arcs behaves, allowing in-process springback prediction and compensation, which can reduce geometric errors in the tubes given the present bending machine accuracy.
      Citation: Assembly Automation
      PubDate: 2018-01-08T03:00:12Z
      DOI: 10.1108/AA-07-2016-082
  • A simple assembly planner for the insertion of ring-shaped deformable
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The aim of this work is to develop a simple planner that is able to automatically plan the motion for a dual-arm manipulator that assembles a ring-shaped elastic object into a cylinder. Moreover, it is desirable to keep the amount of deformation as small as possible, because stretching the object can permanently change its size thus failing to perfectly fit in the cylindrical part and generating undesired gaps between the object and the cylinder. Design/methodology/approach The assembly task is divided in two parts: assembly task planning and assembly step planning. The first one computes key configurations of the robot’s end-effectors, and it is based on a simple heuristic method, whereas the latter computes the robot’s motion between key configurations using an optimization-based planner that includes a potential-energy-based cost function for minimizing the object’s deformation. Findings The optimization-based planner is shown to be effective for minimizing the deformation of the ring-shaped object. A simple heuristic approach is demonstrated to be valid for inserting deformable objects into a cylinder. Experimental results show that the object can be kept without deformation for the first part of the assembly task, thus reducing the time it is being stretched. Originality value A simple assembly planner for inserting ring-shaped deformable objects was developed and validated through several experiments. The proposed planner is able to insert ring-shaped objects without using any sensor (visual and/or force) feedback. The only feedback used is the position of the robot’s end-effectors, which is usually available for any robot.
      Citation: Assembly Automation
      PubDate: 2018-01-08T02:56:31Z
      DOI: 10.1108/AA-12-2016-181
  • Object-oriented design of product assembly feature data requirements in
           advanced assembly planning
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose This paper introduces a schema for the product assembly feature data in an object-oriented and module-based format using Unified Modeling Language (UML). To link production with product design, it is essential to determine at an early stage which entities of product design and development are involved and used at the automated assembly planning and operations. To this end, it is absolutely reasonable to assign meaningful attributes to the parts’ design entities (assembly features) in a systematic and structured way. As such, this approach empowers processes such as motion planning and sequence planning in assembly design. Design/methodology/approach The assembly feature data requirements are studied and definitions are analyzed and redefined. Using object-oriented techniques, the assembly feature data structure and relationships are modeled based on the identified requirements as five UML packages (Part, three-dimensional (3D) models, Mating, Joint and Handling). All geometric and non-geometric design data entities endorsed with assembly design perspective are extracted or assigned from 3D models and realized through the featured entity interface class. The featured entities are then associated (used) with the mating, handling and joints features. The AssemblyFeature interface is realized through mating, handling and joint packages related to the assembly and part classes. Each package contains all relevant classes which further classify the important attributes of the main class. Findings This paper sets out to provide an explanatory approach using object-oriented techniques to model the schema of assembly features association and artifacts at the product design level, all of which are essential in several subsequent and parallel steps of the assembly planning process, as well as assembly feature entity assignments in design improvement cycle. Practical implications The practical implication based on the identified advantages can be classified in three main features: module-based design, comprehensive classification, integration. These features help the automation and solution development processes based on the proposed models much easier and systematic. Originality/value The proposed schema’s comprehensiveness and reliability are verified through comparisons with other works and the advantages are discussed in detail.
      Citation: Assembly Automation
      PubDate: 2018-01-08T02:48:50Z
      DOI: 10.1108/AA-07-2016-084
  • Propagation analysis of variation for fuselage structures in multi-station
           aircraft assembly
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose This paper aims to present a modeling and analysis approach for multi-station aircraft assembly to predict assembly variation. The variation accumulated in the assembly process will influence the dimensional accuracy and fatigue life of airframes. However, in digital large aircraft assembly, variation propagation analysis and modeling are still unresolved issues. Design/methodology/approach Based on an elastic structure model and variation model of multistage assembly in one station, the propagation of key characteristics, assembly reference and measurement errors are introduced. Moreover, the reposition and posture coordination are considered as major aspects. The reposition of assembly objects in a different assembly station is described using transformation and blocking of coefficient matrix in finite element equation. The posture coordination of the objects is described using homogeneous matrix multiplication. Then, the variation propagation model and analysis of large aircraft assembly are established using a discrete system diagram. Findings This modeling and analysis approach for multi-station aircraft assembly reveals the basic rule of variation propagation between adjacent assembly stations and can be used to predict assembly variation or potential dimension problems at a preliminary assembly phase. Practical implications The modeling and analysis approaches have been used in a transport aircraft project, and the calculated results were shown to be a good prediction of variation in the actual assembly. Originality/value Although certain simplifications and assumptions have been imposed, the proposed method provides a better understanding of the multi-station assembly process and creates an analytical foundation for further work on variation control and tolerance optimization.
      Citation: Assembly Automation
      PubDate: 2018-01-03T08:32:23Z
      DOI: 10.1108/AA-03-2017-031
  • A modification of DMVs based state space model of variation propagation
           for multistage machining processes
    • Pages: 381 - 390
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 381-390, September 2017.
      Purpose Complicated workpiece, such as an engine block, has special rough locating datum features (i.e. six independent datum features) due to its complex structure. This locating datum error cannot be handled by current variation propagation model based on differential motion vectors. To extend variation prediction fields, this paper aims to solve the unaddressed variation sources to modify current model for multistage machining processes. Design/methodology/approach To overcome the limitation of current variation propagation model based on differential motion vectors caused by the unaddressed variation sources, this paper will extend the current model by handling the unaddressed datum-induced variation and its corresponding fixture variation. Findings The measurement results of the rear face with respect to the rough datum W and the pan face with respect to the hole Q by coordinate measuring machine (CMM) are −0.006 mm and 0.031 mm. The variation results for rear face and pan face predicted by the modified model are −0.009 mm and 0.025 mm, respectively. The discrepancy of model prediction and measurement is very small. Originality/value This paper modifies the variation propagation model based on differential motion vectors by solving the unaddressed variation sources, which can extend the variation prediction fields for some complicated workpiece and is useful in the future work for many fields, such as process monitoring, fault diagnosis, quality-assured setup planning and process-oriented tolerancing.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:47Z
      DOI: 10.1108/AA-06-2016-052
  • Improving decision making in product flow-based tiling automation for
           custom mosaic design
    • Pages: 391 - 399
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 391-399, September 2017.
      Purpose The purpose of this paper is to present a new tile dispensing decision-making to improve a row formation of a product flow-based tiling automation that has been being developed to support tile placement for custom mosaic design. Design/methodology/approach A new tile dispensing decision-making combines maximum tile loading and simple cycle strategies to minimize time for forming rows of tiles. The maximum tile loading strategy is for minimizing the number of loading rounds, while the simple cycle strategy is for minimizing the movement during the row formation. Findings This proposed decision-making has been developed; implemented in LabVIEW software; linked with other LabVIEW-based programs to control the system; and tested. The results showed the tile dispensing with the proposed decision-making performed better than the previous one. Research limitations/implications The tiling automation is being developed and is currently on a prototyping stage. Originality/value Tile dispensing is critical for this row by row automated assembly, but the existing shortest distance strategy does not guarantee the best performance for a row formation. Therefore, the combination of the maximum tile loading and simple cycle strategies has been developed to improve the performance of the product flow-based tiling automation to better support assembly of custom mosaic design that requires individual tesserae to be assembled to particular positions to illustrate an image properly.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:57Z
      DOI: 10.1108/AA-07-2016-085
  • Implementation and evaluation of a model processing pipeline for assembly
    • Pages: 400 - 410
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 400-410, September 2017.
      Purpose The paper aims to present the processing pipeline of an assembly immersive simulation application which can manage the interaction between the virtual scene and user using stereoscopic display and haptic devices. A new set of elements are integrated in a Collaborative Virtual Environment (CVE) and validated using an approach based on subjective and objective users’ performance criteria. The developed application is intended for Assembly/Disassembly (A/D) analysis, planning and training. Design/methodology/approach A mobility module based on contact information is used to handle the assembly components’ movements through real-time management of collision detection and kinematically constraint guidance. Information on CVE architecture, modules and application configuration process are presented. Impact of device type (3 degrees of freedom (DoFs) vs 6 DoFs) over user’s experience is evaluated. Parameters (number of assembled components and components assembly time) are measured for each user and each haptic device, and results are compared and discussed. Findings Test results proved the efficiency of using a mobility module based on predefined kinematic constraints for reducing the complexity of collision detection algorithms in real-time assembly haptic simulations. Also, experiments showed that, generally, users performed better with 3 DoFs haptic device compared to 6 DoFs haptic equipment. Originality/value The proposed immersive application automates the kinematical joints inference from 3D computer-aided design (CAD) assembly models and integrates it within a haptic-based virtual environment, for increasing the efficiency of A/D process simulations.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:12:07Z
      DOI: 10.1108/AA-11-2015-104
  • Agility in assembly systems: a comparison model
    • Pages: 411 - 421
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 411-421, September 2017.
      Purpose This paper aims at analyzing different possible assembly systems, including innovative potential configurations such as the fully flexible assembly systems (FAS), by defining a novel analytical model that focuses on the concept of agility and its impact on the whole system performance, also evaluating the economic convenience in terms of the unit direct production cost. Design/methodology/approach The authors propose a comparison model derived by Newton’s second law, introducing a quantitative definition of agility (acceleration), resistance of an assembly system to any change of its operative state (inertia) and unit direct production cost (force). Different types of assembly systems (manual, flexible and fully FAS) are analyzed and compared using the proposed model, investigating agility, system inertia and their impact on the unit direct production cost. Findings The proposed agility definition and the proposed comparison model have been applied considering different sets of parameters as independent variables, such as the number of components to assemble (product model complexity) and the target throughput of the system. The main findings are a series of convenience areas which either, for a given target unit direct production cost (force), defines the most agile system to adopt or, for a given target agility (acceleration), defines the most economical system to adopt, as function of the independent variables. Originality/value The novelty of this work is, first, the analytical definition of agility applied to assembly systems and contextualized by means of the definition of the new comparison model. The comparison between different assembly systems on the basis of agility, and by using different sets of independent variables, is a further element of interest. Finally, the resulting convenience areas represent a desirable tool that could be used to optimally choose the most suitable assembly system according to one or more system parameters.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:49Z
      DOI: 10.1108/AA-10-2016-128
  • An assembly gap control method based on posture alignment of wing panels
           in aircraft assembly
    • Pages: 422 - 433
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 422-433, September 2017.
      Purpose The purpose of this paper is to present an optimal posture evaluation model to control the assembly gaps in aircraft wing assembly. The gaps between two mating surfaces should be strictly controlled in precision manufacturing. Oversizing of gaps will decrease the dimensional accuracy and may reduce the fatigue life of a mechanical product. To reduce the gaps and keep them within tolerance, the relative posture (orientation and position) of two components should be optimized in the assembly process. Design/methodology/approach Based on the step alignment strategy, i.e. preliminary alignment and refined alignment, the concept of a small posture transformation (SPT) is introduced. In the preliminary alignment, an initial posture is estimated by a set of auxiliary locating points, with which the components can be quickly aligned near each other. In the refined alignment, the assembly gaps are calculated and the formulation of the gaps with component posture is derived by the SPT. A comprehensive weighted minimization model with gap tolerance constraints is established for redistributing the gaps in multi-regions. Powell-Hestenes-Rockafellar optimization, Singular Value Decomposition and K-Dimensional tree searching are introduced for the solution of the optimal posture for localization. Findings Using the SPT, the trigonometric posture transformation is linearized, which benefits the iterative solution process. Through the constrained model, overall gaps are minimized and excess gaps are controlled within tolerance. Practical implications This method has been tested with simulated model data and real product data, the results of which have shown efficient coordination of mating components. Originality/value This paper proposed an optimal posture evaluation method for minimizing the gaps between mating surfaces through component adjustments. This will promote the assembly automation and variation control in aircraft wing assembly.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:12:04Z
      DOI: 10.1108/AA-04-2016-031
  • Optical scanner assisted robotic assembly
    • Pages: 434 - 441
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 434-441, September 2017.
      Purpose This paper aims to propose the method of automatic robotic assembly of two or more parts placed without fixing instrumentation and positioning on the pallet. Design/methodology/approach Assembly tasks performed by industrial robots are usually based on a constant program, extensive tooling, fixing objects in a given place and a relatively limited sensory system. In this study, a different approach is presented. The industrial robot program is adjusted to the location of parts for assembly in the work space. This leads to a transition from a clearly defined assembly sequence realized by the industrial robot to the one in which the order of execution of the assembly operations can be determined by the mutual position of parts to be assembled. Findings The method presented in this study combines many already known algorithms. The contribution of the authors is to test and select the appropriate combination of methods capable of supporting robotic assembly process based on data from optical 3D scanners. The sequence of operations from scanning to place the parts in the installation position by an industrial robot is developed. A set of parameters for selected methods is presented. The result is a universal procedure that determines the position of the preset models in partial measurements performed at a fixed relative position of the sensor, the measurement object. Originality/value The developed procedure for determining the position of the parts is essential to develop a flexible robotic assembly system. It will be able to perform the task of assembly on the basis of appropriate search algorithms taking into account the selected and implemented sequence of assembly position and orientation of parts, particularly the base unit freely placed on an assembly pallete. It is also the basis of a system for testing different algorithms to optimize the flexible robotic assembly.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:55Z
      DOI: 10.1108/AA-07-2016-068
  • A hybrid technology for assembly sequence planning of reflector panels
    • Pages: 442 - 451
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 442-451, September 2017.
      Purpose The purpose of this study is to guarantee assembly quality and reduce the number of manufacturing cycles required for an reflector of the large reflector antenna. An optimal approach combining a finite element method (FEM) with a genetic algorithm (GA) is developed to simulate and optimize reflector assembly before the assembly stage. Design/methodology/approach The chromosomes of GA are encoded with the consideration of the factors that affect the assembly of reflector. The fitness function of the GA consists of the assembly accuracy obtained from simulation, with evaluation of the assembly time consumption and labor cost. The algorithm will terminate when the GA is finished or the simulation results meet the permissible accuracy. Taking the assembly process of the reflector into account, an FEM based on a “life – death element” technique is introduced to quickly and precisely simulate reflector assembly. Findings A case study is presented, to which the proposed approach is applied. The results of finite element simulation demonstrate that the proposed FEM can simulate the reflector assembly process with oversimplified modeling and accurate simulation results. The optimal approach provides an accurate and efficient method for reflector assembly sequence planning indicated by the comparison of the measurements and calculation results. Originality/value The results also demonstrate that the proposed approach has practical significance for guiding reflector assembly in engineering practice.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:59Z
      DOI: 10.1108/AA-12-2016-171
  • A novel discrete particle swarm algorithm for assembly line balancing
    • Pages: 452 - 463
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 452-463, September 2017.
      Purpose The purpose of this paper is to develop a feasible sequence-oriented new discrete particle swarm optimization (NDPSO) algorithm with novel particles’ updating mechanism for solving simple assembly line balancing problems (SALBPs). Design/methodology/approach In the NDPSO, a task-oriented representation is adopted to solve type I and type II SALBPs, and a particle directly represents a feasible task sequence (FTS) as a permutation. Then, the particle (permutation) is updated as a whole using the geometric crossover based on the edit distance with swaps for two permutations. Furthermore, the fragment mutation with adaptive mutation probability is incorporated into the NDPSO to improve exploration ability. Findings Case study illustrates the effectiveness of the NDPSO. Comparative results between the NDPSO and existing real-encoded PSO (CPSO) and direct discrete PSO (DDPSO) against benchmark instances of type I SALBP and type II SALBP show promising higher performance of the proposed NDPSO. Originality/value A novel particles’ updating mechanism for FTS-encoded particle is proposed to solve the SALBPs. The comparative results indicate that updating of FTS as a whole seems superior to existing updating of FTS by fragment with respect to exploration ability for solving SALBPs. The novel particles’ updating mechanism is also applicable to generalized assembly line balancing problems.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:12:00Z
      DOI: 10.1108/AA-08-2016-104
  • Vibration prediction of pellet mills power transmission by artificial
           neural network
    • Pages: 464 - 470
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 464-470, September 2017.
      Purpose The purpose of this study is to establish a vibration prediction of pellet mills power transmission by artificial neural network. Vibration monitoring is an important task for any system to ensure safe operations. Improvement of control strategies is crucial for the vibration monitoring. Design/methodology/approach As predictive control is one of the options for the vibration monitoring in this paper, the predictive model for vibration monitoring was created. Findings Although the achieved prediction results were acceptable, there is need for more work to apply and test these results in real environment. Originality/value Artificial neural network (ANN) was implemented as the predictive model while extreme learning machine (ELM) and back propagation (BP) learning schemes were used as training algorithms for the ANN. BP learning algorithm minimizes the error function by using the gradient descent method. ELM training algorithm is based on selecting of the input weights randomly of the ANN network and the output weight of the network are determined analytically.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:44Z
      DOI: 10.1108/AA-06-2016-060
  • Shimming design and optimal selection for non-uniform gaps in wing
    • Pages: 471 - 482
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 471-482, September 2017.
      Purpose This paper aims to provide a shimming method based on scanned data and finite element analysis (FEA) for a wing box assembly involving non-uniform gaps. The effort of the present work is to deal with gap compensation problem using hybrid shims composed of solid and liquid forms. Design/methodology/approach First, the assembly gaps of the mating components are calculated based on the scanned surfaces. The local gap region is extracted by the seed point and region growth algorithm from the scattered point cloud. Second, with the constraints of hole margin, gap space and shim specification, the optional shimming schemes are designed by the exhaustive searching method. Finally, the three-dimensional model of the real component is reconstructed based on the reverse engineering techniques, such as section lines and sweeping. Using FEA software ABAQUS, the stress distribution and damage status of the joints under tensile load are obtained for optimal scheme selection. Findings With the scanned mating surfaces, the non-uniform gaps are digitally evaluated with accurate measurement and good visualization. By filling the hybrid shims in the assembly gaps, the joint structures possess similar load capacity but stronger initial stiffness compared to the custom-shimmed structures. Practical implications This method has been tested with the interface data of a wing tip, and the results have shown good efficiency and automation of the shimming process. Originality/value The proposed method can decrease the manufacturing cost of shims, shorten the shimming process cycle and improve the assembly efficiency.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:11:45Z
      DOI: 10.1108/AA-02-2017-021
  • Investigation of ball screw’s alignment error based on dynamic modeling
           and magnitude analysis of worktable sensed vibration signals
    • Pages: 483 - 489
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 483-489, September 2017.
      Purpose The alignment precision of existing methods is limited by the precision of detecting element and worker’s experience, which the parallelism between ball screw and guide way is not guaranteed effectively. Thus, this paper aims to propose a method of detecting ball screw’s alignment error (BSAE) via monitoring the average vibration magnitude induced by rotational frequency of ball screw (VMRFBS). Design/methodology/approach In this study, the ball screw is simplified as a freely supported beam. A mathematical model of the effect of BSAE on the contact angle of the ball and screw is established. The change of contact angle has effect on the deformation and contact stiffness according to the Hertz contact theory. To improve the accuracy of the experimental results, the VMRFBS are analyzed by using average method, and the average values of the VMRFBS at different BSAEs are calculated by using the least squares method. Findings The experimental results show that the average VMRFBS increases with the increasing of BSAE under the BSAE from 0 to 0.2 mm, while the other conditions are unchanged. Originality/value This method provides an approach to monitor the BSAE and improve the alignment accuracy of machine tools and automation equipment, which has a certain guide for improving the alignment accuracy of ball screw.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:12:05Z
      DOI: 10.1108/AA-08-2016-088
  • A novel LLSDPso method for nonlinear dynamic parameter identification
    • Pages: 490 - 498
      Abstract: Assembly Automation, Volume 37, Issue 4, Page 490-498, September 2017.
      Purpose This paper aims to propose a novel method to identify the parameters of robotic manipulators using the torque exerted by the robot joint motors (measured by current sensors). Design/methodology/approach Previous studies used additional sensors like force sensor and inertia measurement unit, or additional payload mounted on the end-effector to perform parameter identification. The settings of these previous works were complicated. They could only identify part of the parameters. This paper uses the torque exerted by each joint while performing Fourier periodic excited trajectories. It divides the parameters into a linear part and a non-linear part, and uses linear least square (LLS) parameter estimation and dual-swarm-based particle swarm optimization (DPso) to compute the linear and non-linear parts, respectively. Findings The settings are simpler and can identify the dynamic parameters, the viscous friction coefficients and the Coulomb friction coefficients of two joints at the same time. A SIASUN 7-Axis Flexible Robot is used to experimentally validate the proposal. Comparison between the predicted torque values and ground-truth values of the joints confirms the effectiveness of the method. Originality/value The proposed method identifies two joints at the same time with satisfying precision and high efficiency. The identification errors of joints do not accumulate.
      Citation: Assembly Automation
      PubDate: 2017-09-18T11:12:02Z
      DOI: 10.1108/AA-08-2016-106
  • Direct teaching of industrial manipulators using current sensors
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The aim of this paper is to implement direct teaching of industrial manipulators using current sensors. The traditional way to implement teaching is either to use a teaching pedant, which is time consuming, or use force sensors, which increases system cost. To overcome these disadvantages, a novel method is explored in the paper by using current sensors installed at joints as torque observers. Design/methodology/approach The method uses current sensors installed at each joint of a manipulator as torque observers and estimates external forces from differences between joint-driven torque computed based on the values of current sensors and commanded values of motor-driven torque. The joint-driven torque is computed by cancelling out both pre-calibrated gravity and friction resistance (compensation). Also, to make the method robust, the paper presents a strategy to detect unexpected slowly drifts and zero external forces and stop the robot in those situations. Findings Experimental results demonstrated that compensating the joint torques using both pre-calibrated gravity and friction resistance has performance comparable to a force sensor installed on the end effector of a manipulator. It is possible to implement satisfying direct teaching without using force sensors on 7 degree of freedom manipulators with large mass and friction resistance. Originality/value The main contribution of the paper is that the authors cancel out both pre-calibrated gravity and friction resistance to improve the direct teaching using only current sensors; they develop methods to avoid unsafe situations like slow drifts. The method will benefit industrial manipulators, especially those with large mass and friction resistance, to realize flexible and reliable direct teaching.
      Citation: Assembly Automation
      PubDate: 2017-12-28T02:52:27Z
      DOI: 10.1108/AA-02-2017-027
  • Assembly sequence planning for motion planning
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to develop a planner for finding an optimal assembly sequence for robots to assemble objects. Each manipulated object in the optimal sequence is stable during assembly. They are easy to grasp and robust to motion uncertainty. Design/methodology/approach The input to the planner is the mesh models of the objects, the relative poses between the objects in the assembly and the final pose of the assembly. The output is an optimal assembly sequence, namely, in which order should one assemble the objects, from which directions should the objects be dropped and candidate grasps of each object. The proposed planner finds the optimal solution by automatically permuting, evaluating and searching the possible assembly sequences considering stability, graspability and assemblability qualities. Findings The proposed planner could plan an optimal sequence to guide robots to do assembly using translational motion. The sequence provides initial and goal configurations to motion planning algorithms and is ready to be used by robots. The usefulness of the proposed method is verified by both simulation and real-world executions. Originality/value The paper proposes an assembly planner which can find an optimal assembly sequence automatically without teaching of the assembly orders and directions by skilled human technicians. The planner is highly expected to improve teachingless robotic manufacturing.
      Citation: Assembly Automation
      PubDate: 2017-12-20T11:50:13Z
      DOI: 10.1108/AA-01-2017-009
  • A united kinematic calibration method for a dual-machine system
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose This paper aims to propose a united kinematic calibration method for a dual-machine system in automatic drilling and riveting. The method takes both absolute and relative pose accuracy into account, which will largely influence the machining accuracy of the dual-machine system and assembly quality. Design/methodology/approach A comprehensive kinematic model of the dual-machine system is established by the superposition of sub-models with pose constraints, which involves base frame parameters, kinematic parameters and tool frame parameters. Based on the kinematic model and the actual pose error data measured by a laser tracker, the parameters of coordinated machines are identified by the Levenberg–Marquardt method as a multi-objective nonlinear optimization problem. The identified parameters of the coordinated machines will be used in the control system. Findings A new calibration method for the dual-machine system is developed, including a comprehensive kinematic model and an efficient parameter identification method. The experiment results show that with the proposed method, the pose accuracy of the dual-machine system was remarkably improved, especially the relative position and orientation errors. Practical implications This method has been used in an aircraft assembly project. The calibrated dual-machine system shows a good performance on system coordination and machining accuracy. Originality/value This paper proposes a new method with high accuracy and efficiency for the dual-machine system calibration. The research can be extended to multi-machine and multi-robot fields to improve the system precision.
      Citation: Assembly Automation
      PubDate: 2017-12-20T11:46:50Z
      DOI: 10.1108/AA-02-2017-029
  • A novel spring-back model by considering assembly contact
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to present a novel assembly spring-back model which takes surface contact conditions between sheet metal parts into consideration so that the assembly dimensions and variations can be more precisely predicted than existing assembly simulation models. Design/methodology/approach Because an assembly process is composed of four essential steps, i.e. locating, clamping, joining and tool releasing, the mechanistic models associated with these steps are developed in the paper. In particular, the surface contact between the weld flanges (in folding joint configuration) and the overlapping surfaces (in lap joint configurations) is included in the models. Sensitivity models are developed. Findings Two cases studies are presented, i.e. the cantilever beams assembly and the Z-plates assembly. More precise prediction results are shown. Research limitations/implications The model developed in this paper is based upon analytical elastic beam theories. Therefore, the results and case studies are limited only to workpieces that can be approximately represented by beam geometries. However, the methods can be broadened to generic workpiece geometries by using finite element methods; thus, the developed method is highly valuable to a broad range of applications such as automotive body assembly and aerospace industries. Originality/value The novelty of this research lies in its inclusion of surface contact conditions in an assembly simulation model by using analytical beam mechanistic models to achieve more accurate assembly variation predictions.
      Citation: Assembly Automation
      PubDate: 2017-12-20T11:43:14Z
      DOI: 10.1108/AA-08-2016-097
  • Compliant assembly variation analysis of thin-walled structures based on
           the absolute nodal coordinate formulation
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose Thin-walled structures inevitably always have manufacturing deviations, which affects the assembly quality of mechanical products. The assembly quality directly determines the performances, reliability and service life of the products. To achieve the automatic assembly of large-scale thin-walled structures, the sizing force of the structures with deviations should be calculated, and its assembling ability should be studied before assembly process. The purpose of this study is to establish a precise model to describe the deviations of structures and to study the variation propagation during assembly process. Design/methodology/approach Curved thin-walled structures are modeled by using the shell element via the absolute nodal coordinate formulation. Two typical deviation modes of the structure are defined. The generalized elastic force of shell elements with anisotropic materials is deduced based on a continuum mechanics approach to account for the geometric non-linearity. The quasi-static method is introduced to describe the assembly process. The effects of the deviation forms, geometrical parameters of the thin-walled structures and material properties on assembly quality are investigated numerically. Findings The geometric non-linearity of structure and anisotropy of materials strongly affect the variation propagation and the assembly quality. The transformation and accumulation effects of the deviations are apparent in the multiple assembly process. The constraints on the structures during assembly can reduce assembly deviation. Originality/value The plate element via the absolute nodal coordinate formulation is first introduced to the variation propagation analysis. Two typical shape deviation modes are defined. The elastic force of structures with anisotropic materials is deduced. The variation propagation during the assembly of structures with various geometrical and material parameters is investigated.
      Citation: Assembly Automation
      PubDate: 2017-12-20T11:37:50Z
      DOI: 10.1108/AA-05-2016-046
  • A new method of precise orientation adjustment based on matrix similarity
           for large-scale component
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose In the assembly process of the satellite, there will be multiple installation and disassembly operations for the solar wing and the main satellite body (or simulator). However, the traditional method of orientation adjustment by theodolite and two-axis turntable is difficult to coordinate three rotation angles of yaw, pitch and roll, which leads to the complexity of actual operation and dependency on manual experience. Therefore, this paper aims to propose a new method to achieve rapid and precise orientation adjustment. Design/methodology/approach The similarity relation of the orientation variation matrix in a different coordinate system is studied, and a mapping model of the similarity relation is established. By using multiple element matrices to construct the original rotation matrix, the mapping is solved in quaternion form. Taking the theodolite as a measuring instrument and the Stewart platform as a control equipment, an experiment on installing the solar wing is performed to validate the effectiveness of the algorithm. Findings Based on the solving algorithm, the orientation adjustment process is simplified to a three-step fixed mode, which is three adjustments to get the parameter of the mapping model, one to adjust the component in place and another to further fine tuning. The final orientation deviation is less than 0.003° and close to the level of using a laser tracker, achieving the required accuracy of 0.0115°. Originality/value This paper reveals the similarity relation of the variation matrix in the process of orientation adjustment and presents a new method to achieve rapid and precise orientation adjustment for the large-scale component.
      Citation: Assembly Automation
      PubDate: 2017-12-18T09:40:59Z
      DOI: 10.1108/AA-01-2017-010
  • Workload smoothing in two-sided assembly lines
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to define new criteria for measuring workload smoothness of two-sided assembly lines and propose an algorithm to solve a two-sided assembly line balancing problem focusing on distributing the idle time and the workload as evenly as possible among the workstations. Design/methodology/approach This paper points out that the mean absolute deviation (MAD) and the smoothness index (SI) used to measure the workload smoothing in one-sided assembly lines are both inappropriate to evaluate the workload balance among workstations in two-sided assembly lines, as the idle time occur at the beginning and in the middle of a cycle within workstations. Then, the finish-time-based SI and MAD (FSI and FMAD) are defined, and a heuristic procedure based on the core mechanism of Moodie and Young method is proposed to smooth the assembly workload in two-sided assembly lines. Findings The computational results indicate that the proposed heuristic algorithm combined with the FMAD is effective in distributing the idle time and the workload among workstations as evenly as possible in two-sided assembly lines. Practical implications The two-sided assembly line balancing problem with the objective of the line efficiency can be effectively solved by the proposed approach. Originality/value The FMAD is proposed to effectively improve the workload smoothing in two-sided assembly lines.
      Citation: Assembly Automation
      PubDate: 2017-12-15T02:37:55Z
      DOI: 10.1108/AA-09-2016-112
  • Generating disassembly tasks for selective disassembly using
           ontology-based disassembly knowledge representation
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose This paper aims to develop methods for generating disassembly tasks for selective disassembly. The disassembly task contains the disassembly information, namely, disassembly direction, disassembly tool and selective disassembly sequence. Design/methodology/approach Ontology is adopted to represent the product, and ontology rules are used to represent the disassembly knowledge. A product ontology model (POM) is introduced on the basis of material, connection matrix and interference matrix. Two types of disassembly knowledge are taken into account, one is the disassembly knowledge of disassembly tool selection and the other is the disassembly knowledge of special connections. Based on the POM and the disassembly knowledge, decision support methods are designed to generate disassembly tasks. Findings A centrifugal pump is used to demonstrate the proposed methods, and the result shows that the methods work well. Research limitations/implications The methods developed in this study are fundamental approaches. The ontology and the ontology rules can be extended with more disassembly knowledge. Originality/value The main contribution of this research is the development of methods for representing disassembly knowledge based on ontology rules and the decision support methods for generating disassembly tasks.
      Citation: Assembly Automation
      PubDate: 2017-12-15T02:35:55Z
      DOI: 10.1108/AA-04-2016-034
  • Task planning for mobile painting manipulators based on manipulating space
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose To paint large workpieces automatically, painting manipulators with hollow wrists must be transported by mobile platforms to different positions because of their limited workspaces. This paper aims to provide a visualization method for finding appropriate base positions (BPs) and maximum painting areas for manipulators. Design/methodology/approach This paper begins by analyzing the motion characteristics of manipulators possessing a spherical wrist and summarizing them into three constraints – positioning, orientation and singularity avoidance. The hollow wrist is simplified and considered as spherical by introducing the concepts of an inner wrist center and an outer wrist center. Taking the three constraints into consideration, the boundaries of the manipulating space are formulated analytically. Finally, to verify the method, the space obtained is applied to determine the maximum painting areas for flat, cylindrical and conical surfaces. Experiments of robotic painting were used to confirm the results. Findings Compared with previous studies, the maximum areas obtained using the proposed method increased by 17-131 per cent with an algorithm of lower complexity, and the process remained visually intuitive, thereby demonstrating that the method of manipulating space is more effective. Originality/value Such a method allows individuals to visualize the entire painting area at the current BP, thereby maximizing painting areas or optimizing BPs. It opens a black box that is the relationship between BPs and blocks. The method can also be used to choose the best configuration for painting manipulators, select the end-effector structure parameters, split surfaces into blocks, etc.
      Citation: Assembly Automation
      PubDate: 2017-12-15T02:32:54Z
      DOI: 10.1108/AA-04-2017-044
  • Self-classification of assembly database using evolutionary method
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of the paper is to develop a method of automatic classification of the components of the assembly units. The method is crucial for developing an automatic ship assembly planning tools. The proposed method takes into account the assumptions specific for shipbuilding technology processes: high complexity of structures, difficult expert-based classification of components, fixed priority relations between connections resulting from geometrical constraints and demands of welding processes. Design/methodology/approach The set of ex post determined liaisons and assembly sequences constitutes the database of structures which have been made-up earlier. The components classification problem is solved using matrix coding of graphs. Information in such form is stored in the database. The minimization of number of cycles in the graph of classes sequence and minimization of diversity of classes within all constructions has been proposed as criteria of optimization. The genetic algorithm has been proposed as a solution method. Findings The proposed method solves the problem of components’ classifications. It allows setting the pattern of priorities between classes of various connections. This gives a chance to determine the relationship constraints between the connections of new structures for which assembly sequences are not established. Research limitations/implications Mathematical formulation of the database is quite laborious. The possibility of partial automation of this process should be considered. Owing to the complexity of the problem, a relatively simple objective function has been proposed. During a ship hull assembly, additional criteria should be taken into account, what will be the direction of further research. Practical implications Automatic classification of components is dedicated for implementation in shipyards and similar assembly systems. Tests performed by the authors confirm efficiency of presented method in supporting management of the database and assembly of new structures planning. Suggested activity-oriented approach allows for easy conversion of any assembly unit structure to the form of a matrix. Originality/value The new approach for components classification according to its assembly features distinguishes the proposed method from others. The use of nilpotent matrix theory in an acyclicity of graphs analysis is also a unique achievement. Original crossover and mutation operators for assembly sequence were proposed in the article.
      Citation: Assembly Automation
      PubDate: 2017-12-15T02:29:54Z
      DOI: 10.1108/AA-06-2017-071
  • Fastener identification and assembly verification via machine vision
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The study aims to evaluate the capability of a machine vision camera and software to recognize fasteners for the purpose of assembly verification. This will enable the current assembly verification system to associate torque verfication with a specific fastener. Design/methodology/approach A small camera is installed at the head of a tool near the socket. The camera is used to capture images surrounding the fastener, and feeding them into machine vision recognition software. By recognizing unique features around the fastener, the fastener can be uniquely identified and therefore verified to be assembled. Additional filtering and multiple frame recognition will improve the reliability of the recognition. Findings The machine vision technology is found to be adequately reliable in identifying fasteners after tuning key threshold parameters and requiring multiple positively recognized frames. The time to verify can be kept around a fraction of a second to prevent impacting assembly speed. Research limitations/implications This experiment was run under simulated assembly line lighting conditions. It also does not explore industrial remote head industrial camera hardware. Practical implications By using a remote-mounted camera in combination with electric tools, a reliable assembly verification system can be used to eliminate torque check processes of critical fasteners, thereby reducing the cost of assembly. Originality/value Currently, assembly verification is done only using the torque values. In automated assembly line, each process might involve fastening multiple fasteners. Using this system, a new level of assembly verification is achieved by recording the assembled fastener and its associated torque.
      Citation: Assembly Automation
      PubDate: 2017-12-14T09:59:55Z
      DOI: 10.1108/AA-08-2016-093
  • Physical deformation configuration of a spatial clamped cable based on
           Kirchhoff rods
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose In this study, a modeling method for a clamped deformable cable simulation based on Kirchhoff theory is proposed. This methodology can be used to describe the physical deformation configuration of any constrained flexible cable in a computer-aided design/manufacturing system. The modeling method, solution algorithm, simulation and experimental results are presented to prove the feasibility of the proposed methodology. The paper aims to discuss these issues. Design/methodology/approach First, Kirchhoff equations for deformable cables are proposed based on the nonlinear mechanics of thin elastic rods, and the general solution of the equations described by the Euler angles is given in the arc coordinate system. The parametric form solution of the Kirchhoff equations, which is easy to use, is then obtained in a cylindrical coordinate form based on Saint Venant’s theory. Finally, mathematical expressions that reflect the clamped cable configuration are given, and the deformable process is simulated based on an open source geometry kernel and is then tested by a 3D laser scanning technology. Findings The method presented in this paper can be adapted to any boundary condition for constrained cables as long as the external force and torque are known. The experimental results indicate that both the model and algorithm are efficient and accurate. Research limitations/implications A more comprehensive study must be executed for the physical simulation of more complicated constrained cables, such as the helical spring and asymmetric constraint. The influence of the material properties of the cable on the calculation efficiency must be considered in future analysis. Originality/value The semi-analytical algorithm of the cable simulation in cylindrical coordinates is a novel topic and is more accurate and efficient than the common numerical solution.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:51:27Z
      DOI: 10.1108/AA-08-2016-098
  • A force rendering model for virtual assembly of mechanical parts with
           clearance fits
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose Realistic force sensation can help operators better feel and manipulate parts for virtual assembly (VA). Moreover, for VA of mechanical parts, it is necessary to consider their tolerance levels so as to apply proper assembly forces. Out of the three common assembly fit types, the type of clearance fit is the focus of virtual manual assembly, as parts with such fit type require precise force feedback to assist users’ assembly operations. Design/methodology/approach This study proposes a novel force rendering model for VA of mechanical parts with clearance fits. By decomposing an actual assembly operation into three consecutive states, the corresponding forces are formulated. Findings A prototype system is designed and developed to implement the model, and comparative case studies are conducted to investigate the users’ performance with the other three common approaches, namely, a typical WIMP (window-icon-menu-pointer) interface with CAD software, a physics simulation with collision detection and the approach that combines physics simulation and geometric constraints restriction. The results have shown that the proposed model is more realistic by providing continuous and realistic force feedback to the users. Originality/value The users’ feeling of immersion and their operational efficiency are greatly enhanced with the force sensation provided.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:49:05Z
      DOI: 10.1108/AA-12-2016-175
  • Analysis of chaotic dynamics for aircraft assembly lines
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to investigate the nonlinear dynamics of the aircraft assembly lines. An approach for modeling and analyzing the production rate of an aircraft assembly line is introduced using the chaos theory. Design/methodology/approach First, two key system variables including reliability and learning ability are considered to control the dynamics model. The discrete-time dynamics equation of the production rate is established as a function of the reliability and the learning rate. Then an improved Gauss-learning curve is proposed and applied to aircraft assembling condition. Finally, the bifurcation diagrams and the maximal Lyapunov exponents are used and applied to the experimental study to analyze the dynamic behavior under different combinations of parameters. Findings On the basis of the experimental study, it is shown that chaotic behavior really exists in the aircraft assembly lines. The reliability and the Gauss-learning curve can nonlinearly affect the production rate. Originality/value This paper applied nonlinear dynamics and chaotic theory to the production analyses of the aircraft assembly lines for the first time. The proposed model has been successfully applied to a practical case, and the result justifies its advantage as well as feasibility to both theory and engineering application.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:46:05Z
      DOI: 10.1108/AA-08-2016-086
  • Assembly modelling approach for special purpose machines
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to develop an assembly modelling approach to be applied with a software package, to assist in the design and assembly of special purpose machines (SPMs). Design/methodology/approach A database of SPM elements was established, and an assembly relationships graph was created. Mating conditions were identified between the SPM elements, and their assembly constraints were extracted and implemented in SolidWorks application programming interface. Findings The implementation of this assembly modelling approach was validated by selecting SPM layouts as examples. A significant reduction in the assembly time was achieved compared to the traditional assembly procedure for the same examples. Originality/value This is a new application of assembly modelling that assists engineers and designers in the design and assembly processes of SPMs. This approach can also be applied to other machine tools with similar attributes.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:43:43Z
      DOI: 10.1108/AA-12-2016-170
  • Detection and estimation of mental fatigue in manual assembly process of
           complex products
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose This paper aims to investigate an approach for mental fatigue detection and estimation of assembly operators in the manual assembly process of complex products, with the purpose of founding the basis for adaptive transfer and demonstration of assembly process information (API), and eventually making the manual assembly process smarter and more human-friendly. Design/methodology/approach The proposed approach detects and estimates the mental state of assembly operators by electroencephalography (EEG) signal recording and analysis in an engine assembly experiment. When the subjects perform assembly tasks, their EEG signal is recorded by a portable EEG recording system called Emotiv EPOC+ headset. The feature set of the EEG signal is then extracted by calculating its power spectrum density (PSD), followed by data dimension reduction based on principal component analysis (PCA). The dimension-reduced data are classified by using support vector machines (SVMs), and hence, the mental state of assembly operators can be estimated during the assembly process. Findings The experimental result shows that the proposed approach is able to estimate the mental state of assembly operators within an acceptable accuracy range, and the PCA-based dimension reduction method performs very well by representing the high-dimensional EEG feature set with just a few principal components. Originality/value This paper provides theoretical and experimental basis for the API transfer and demonstration based on human cognition. It provides a new idea to seek balance between the improvement of production efficiency and the sustainable utilization of human resources.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:38:03Z
      DOI: 10.1108/AA-03-2017-040
  • Tolerance analysis of assemblies with sculptured components in composites
           materials: comparison between an analytical method and a simulation
    • Abstract: Assembly Automation, Ahead of Print.
      Purpose The purpose of this paper is to compare two different tools for tolerance analysis. Tolerance analysis is an important task to design and manufacture high-precision mechanical assemblies; it has received considerable attention in the literature. Many are the tools required to carry out a tolerance analysis, and may be divided into two categories: the analytical models and the statistical software packages. No comparison exists in the literature among these two categories. Design/methodology/approach This work presents a comparison between two different approaches to tolerance analysis: an analytical method, the variational model, and a statistical software, eM-Tolmate. The comparison has been developed on the same aeronautical case study that constitutes an actual product. Findings The proposed approach has been applied to an aeronautical case study. The results of the case study show how, when 2D tolerance analysis problems need to be solved, the two adopted tools give the same results. When the complexity of the tolerance analysis problems increases, the statistical software becomes the only choice to use. The new findings of the present paper are related to the fact that computer-aided tolerance analysis software packages remain the only choice to approach actual complex industrial products despite the extensive development of theoretical research. Research limitations/implications This paper deals with a unique case study. However, the two adopted approaches and the obtained results are general, that is, they may be applied to any assembly. Practical implications Tolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly, before getting the physical assembly. It involves a decrease of the manufacturing costs. Originality/value Many are the tools for tolerance analysis, such as different analytical models and different commercial software packages. Some are the comparisons among the different tools in the literature, but they are not exhaustive. Therefore, when a user has to solve an assembly problem to foresee the geometric interferences during the design stage, he/she does not know what to choose. The original contribution of the paper is to address the user’s choice through a comparison between an analytical model and a statistical software to solve the tolerance analysis problems of an actual aeronautical assembly.
      Citation: Assembly Automation
      PubDate: 2017-12-14T08:35:03Z
      DOI: 10.1108/AA-07-2016-064
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