Measurement Assisted Assembly Research Articles

A Coordination Space Model for Assemblability Analysis and Optimization during Measurement-Assisted Large-Scale Assembly

The assembly process is sometimes blocked due to excessive dimension deviations during large-scale assembly. It is inefficient to improve the assembly quality by trial assembly, inspection, and accuracy compensation in the case of excessive deviations. Therefore, assemblability prediction by analyzing the measurement data, assembly accuracy requirements, and the pose of parts is an effective way to discover the assembly deviations in advance for measurement-assisted assembly. In this paper, a coordination space model is constructed based on a small displacement torsor and assembly accuracy requirements. An assemblability analysis method is proposed to check whether the assembly can be executed directly. Aiming at the incoordination problem, an assemblability optimization method based on the union coordination space is proposed. Finally, taking the space manipulator assembly as an example, the result shows that the proposed method can improve assemblability with a better assembly quality and less workload compared to the least-squares method.

A heuristic cabin-type component alignment method based on multi-source data fusion

In cabin-type component alignment, digital measurement technology is usually adopted to provide guidance for assembly. Depending on the system of measurement, the alignment process can be divided into measurement-assisted assembly (MAA) and force-driven assembly. In MAA, relative pose between components is directly measured to guide assembly, while in force-driven assembly, only contact state can be recognized according to measured six-dimensional force and torque (6D F/T) and the process is completed based on preset assembly strategy. Aiming to improve the efficiency of force-driven cabin-type component alignment, this paper proposed a heuristic alignment method based on multi-source data fusion. In this method, measured 6D F/T, pose data and geometric information of components are fused to calculate the relative pose between components and guide the movement of pose adjustment platform. Among these data types, pose data and measured 6D F/T are combined as data set. To collect the data sets needed for data fusion, dynamic gravity compensation method and hybrid motion control method are designed. Then the relative pose calculation method is elaborated, which transforms collected data sets into discrete geometric elements and calculates the relative poses based on the geometric information of components. Finally, experiments are conducted in simulation environment and the results show that the proposed alignment method is feasible and effective.

Assessment of large-scale assembly coordination based on pose feasible space

The characteristics of large-scale products, such as large size, multi coordination features, and deformation, often lead to the difficulty of satisfying assembly requirements which reduces the assembly efficiency. In the domain of measurement-assisted assembly, assembly is realized by pose adjustment. Geometric constraints form a set of assembly poses which satisfy all constraints. The pose set shows whether the parts can be assembled and whether they are easy to assemble. In this paper, small displacement torsor (SDT) is used to express the coordinated pose variation, and the inequalities constructed by geometric constraints are formulated. The pose feasible space (PFS) is proposed as the assessment index of assembly coordination. The pose relations of different assembly features are considered to analyze multi-features constraints. Finally, a simulation analysis of the wing-fuselage joints assembly is carried out. A Monte Carlo method based on SDT is used to solve PFS. Besides, the best-fit method is taken to calculate the optimal pose and to analyze the geometric constraints. The result shows the PFS can reflect the degree of assembly coordination.

A self-adaptive alignment strategy for large components based on dynamic compliance center

PurposeAiming at the problems of geometric precision misalignment and unconsidered physical constraints between large components during the measurement-assisted assembly, a self-adaptive alignment strategy based on the dynamic compliance center (DCC) is proposed in this paper, using force information to guide alignment compliantly.Design/methodology/approachFirst, the self-adaptive alignment process of large components is described, and its geometrical and mechanical characteristics are analyzed based on six-dimensional force/torque (F/T). The setting method of DCC is studied and the areas of DCC are given. Second, the self-adaptive alignment platform of large components driven by the measured six-dimensional F/T is constructed. Based on this platform, the key supporting technologies, including principle of self-adaptive alignment, coordinate transfer, calculation of six-dimensional F/T and alignment process control, are illustrated.FindingsUsing the presented strategy, the position and orientation of large component is adjusted adaptively responding to measured six-dimensional F/T and the changes of contact states are consistent with the strategy. Through the setting of DCC, alignment process runs smoothly without jamming.Practical implicationsThis strategy is applied to the alignment experiment of large components muff coupling. The experimental results show that the proposed alignment strategy is correct and effective and meets the real-time requirement.Originality/valueThis paper proposed a novel way to apply force information in large component self-adaptive alignment, and the setting method of DCC was presented to make the alignment process more feasible.

Feasibility of measurement-assisted assembly of ship hull blocks

Quality and productivity enhancement of large-scale assembly processes in ship construction can be obtained by introducing measurement-assisted assembly (MAA). MAA consists in using advanced 3D measurement systems to enable direct, fast and sometimes even automatic part-to-part assembly without iteration. This experimental research project aims to develop, demonstrate and evaluate the MAA concept for the assembly of hull blocks of medium- and large-sized vessels. An indoor GPS (iGPS) and a robotic total station are used as measurement systems. Experiments have been carried out to evaluate aspects related to metrological performance, functionality and robustness of the measurement systems. An automatic MAA process was simulated with a Stewart Platform. The results indicate that MAA is generally applicable to the assembly of ship hulls and that both iGPS and robotic total station are suitable measurement systems for this application. The advantages and drawbacks of both systems are discussed.

INDUSTRIAL PHOTOGRAMMETRY - ACCEPTED METROLOGY TOOL OR EXOTIC NICHE

New production technologies like 3D printing and other adaptive manufacturing technologies have changed the industrial manufacturing process, often referred to as next industrial revolution or short industry 4.0. Such Cyber Physical Production Systems combine virtual and real world through digitization, model building process simulation and optimization. It is commonly understood that measurement technologies are the key to combine the real and virtual worlds (eg. [Schmitt 2014]). <br><br> This change from measurement as a quality control tool to a fully integrated step in the production process has also changed the requirements for 3D metrology solutions. Key words like MAA (Measurement Assisted Assembly) illustrate that new position of metrology in the industrial production process. <br><br> At the same time it is obvious that these processes not only require more measurements but also systems to deliver the required information in high density in a short time. Here optical solutions including photogrammetry for 3D measurements have big advantages over traditional mechanical CMM’s. <br><br> The paper describes the relevance of different photogrammetric solutions including state of the art, industry requirements and application examples.

INDUSTRIAL PHOTOGRAMMETRY - ACCEPTED METROLOGY TOOL OR EXOTIC NICHE

Abstract. New production technologies like 3D printing and other adaptive manufacturing technologies have changed the industrial manufacturing process, often referred to as next industrial revolution or short industry 4.0. Such Cyber Physical Production Systems combine virtual and real world through digitization, model building process simulation and optimization. It is commonly understood that measurement technologies are the key to combine the real and virtual worlds (eg. [Schmitt 2014]). This change from measurement as a quality control tool to a fully integrated step in the production process has also changed the requirements for 3D metrology solutions. Key words like MAA (Measurement Assisted Assembly) illustrate that new position of metrology in the industrial production process. At the same time it is obvious that these processes not only require more measurements but also systems to deliver the required information in high density in a short time. Here optical solutions including photogrammetry for 3D measurements have big advantages over traditional mechanical CMM’s. The paper describes the relevance of different photogrammetric solutions including state of the art, industry requirements and application examples.

The measurement-aided welding cell—giving sight to the blind

This article introduces the concept of a measurement-aided welding cell (MAWC). It then focuses on developing the MAWC for body and chassis components in the automotive industry. Industry 4.0 requires flexibility and reconfigurability from manufacturing systems, which has been addressed by cellular manufacturing systems (CMS). Traditional automotive welding technology is not flexible enough to be used as a CMS. So, the core of automotive production does not meet the needs of next-generation manufacturing and Industry 4.0. For the first time, this demand has been answered—by the MAWC. The MAWC is based on two handling robots, a welding robot and an optical measurement system, all integrated into one welding cell. The measurement system controls guides and gives feedback to the handling and welding robots. This way, accurate welding is based on actual part-to-part adjustment, rather than hard mechanical tooling. The lack of hard mechanical tooling allows flexibility. Measurement-assisted assembly and machining is not new. However, it has not previously been applied to complex welding processes, because traditional measurement technologies have not been satisfactory. A newly developed system using multi-camera measurement technology meets the flexibility requirements. The technology required for a MAWC is reviewed and found to be in common use in the automotive industry. Three development projects are presented in which the main functions of a MAWC are successfully demonstrated. Two of these projects were done with BMW. A MAWC allows the manufacturing process to immediately swap to a different product on the same line, increasing the production line utilisation rate and making it possible to produce several low-volume products in one manufacturing system. So, the MAWC will not only yield benefits from its scalable capacity and global decentralization, but it will also open new business opportunities for manufacturing low-volume luxury car parts or post-production spare parts.

A framework of measurement assisted assembly for wing-fuselage alignment based on key measurement characteristics

Wide employments of large scale digital metrologies have promoted the development of digital aircraft assembly technologies, which are changing traditional processes of wing-fuselage alignment to high precision and more efficient digital alignment based on measurement assisted assembly (MAA). MAA is a systematic technique and relies on the integration of digital measurement with assembly process, which is not only the integration of operations, but also data fusion and propagation from product design, through digital inspection to components assembly. In order to direct and support the applications of advanced approaches in MAA for wing-fuselage alignment, a novel framework of measurement assisted assembly methodology is proposed to realise the process integration and data fusion based on key measurement characteristics (KMCs). Firstly, definition, classification and mathematical model of KMCs are presented; then, the framework is constructed on the basis of integrated process model, measurement data model and data process kernel. Finally, a case of wing-fuselage alignment simulation is carried out to illuminate the application of measurement assisted assembly technique with the framework. [Received 28 April 2013; Revised 25 February 2014; Accepted 26 April 2014]

Corrigendum

‘Review of the application of flexible, measurement-assisted assembly technology in aircraft manufacturing’ by Zhongyi Mei and Paul G Maropoulos published in Journal of Engineering Manufacture, Volume 228, Issue 10 (2014). DOI: 10.1177/0954405413517387

Review of the application of flexible, measurement-assisted assembly technology in aircraft manufacturing

Aircraft assembly is the most important part of aircraft manufacturing. A large number of assembly fixtures must be used to ensure the assembly accuracy in the aircraft assembly process. Traditional fixed assembly fixture could not satisfy the change of the aircraft types, so the digital flexible assembly fixture was developed and was gradually applied in the aircraft assembly. Digital flexible assembly technology has also become one of the research directions in the field of aircraft manufacturing. The aircraft flexible assembly can be divided into three assembly stages that include component-level flexible assembly, large component-level flexible assembly, and large components alignment and joining. This article introduces the architecture of flexible assembly systems and the principles of three types of flexible assembly fixtures. The key technologies of the digital flexible assembly are also discussed. The digital metrology system provides the basis for the accurate digital flexible assembly. Aircraft flexible assembly systems mainly use laser tracking metrology systems and indoor Global Positioning System metrology systems. With the development of flexible assembly technology, the digital flexible assembly system will be widely used in current aircraft manufacturing.

A new paradigm in large-scale assembly—research priorities in measurement assisted assembly

This paper presents for the first time the concept of measurement assisted assembly (MAA) and outlines the research priorities of the realisation of this concept in the industry. MAA denotes a paradigm shift in assembly for high value and complex products and encompasses the development and use of novel metrology processes for the holistic integration and capability enhancement of key assembly and ancillary processes. A complete framework for MAA is detailed showing how this can facilitate a step change in assembly process capability and efficiency for large and complex products, such as airframes, where traditional assembly processes exhibit the requirement for rectification and rework, use inflexible tooling and are largely manual, resulting in cost and cycle time pressures. The concept of MAA encompasses a range of innovativemeasurement- assisted processes which enable rapid partto- part assembly, increased use of flexible automation, traceable quality assurance and control, reduced structure weight and improved levels of precision across the dimensional scales. A full scale industrial trial of MAA technologies has been carried out on an experimental aircraft wing demonstrating the viability of the approach while studies within 140 smaller companies have highlighted the need for better adoption of existing process capability and quality control standards. The identified research priorities for MAA include the development of both frameless and tooling embedded automated metrology networks. Other research priorities relate to the development of integrated dimensional variation management, thermal compensation algorithms as well as measurement planning and inspection of algorithms linking design to measurement and process planning. © Springer-Verlag London 2013.

Achieving Low Cost and High Quality Aero Structure Assembly through Integrated Digital Metrology Systems

Measurement assisted assembly (MAA) has the potential to facilitate a step change in assembly efficiency for large structures such as airframes through the reduction of rework, manually intensive processes and expensive monolithic assembly tooling. It is shown how MAA can enable rapid part-to-part assembly, increased use of flexible automation, traceable quality assurance and control, reduced structure weight and improved aerodynamic tolerances. These advances will require the development of automated networks of measurement instruments; model based thermal compensation, the automatic integration of’live’ measurement data into variation simulation and algorithms to generate cutting paths for predictive shimming and drilling processes. This paper sets out an architecture for digital systems which will enable this integrated approach to variation management.