Computational Optics for Mobile Terminals in Mass Production Chen, Shiqi; Lin, Ting; Feng, Huajun ...
IEEE transactions on pattern analysis and machine intelligence,
2023-April-1, 2023-Apr, 2023-4-1, 20230401, Letnik:
45, Številka:
4
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Correcting the optical aberrations and the manufacturing deviations of cameras is a challenging task. Due to the limitation on volume and the demand for mass production, existing mobile terminals ...cannot rectify optical degradation. In this work, we systematically construct the perturbed lens system model to illustrate the relationship between the deviated system parameters and the spatial frequency response (SFR) measured from photographs. To further address this issue, an optimization framework is proposed based on this model to build proxy cameras from the machining samples' SFRs. Engaging with the proxy cameras, we synthetic data pairs, which encode the optical aberrations and the random manufacturing biases, for training the learning-based algorithms. In correcting aberration, although promising results have been shown recently with convolutional neural networks, they are hard to generalize to stochastic machining biases. Therefore, we propose a dilated Omni-dimensional dynamic convolution (DOConv) and implement it in post-processing to account for the manufacturing degradation. Extensive experiments which evaluate multiple samples of two representative devices demonstrate that the proposed optimization framework accurately constructs the proxy camera. And the dynamic processing model is well-adapted to manufacturing deviations of different cameras, realizing perfect computational photography. The evaluation shows that the proposed method bridges the gap between optical design, system machining, and post-processing pipeline, shedding light on the joint of image signal reception (lens and sensor) and image signal processing (ISP).
The additive manufacture of parts using extrusion-based techniques such as 3D Concrete Printing (3DCP) offers an alternative to traditional moulding processes. The precision to which the desired ...shape can be produced, however, is limited by the extrusion process and layer thickness, exacerbated by the deformation that occurs in the wet material during manufacture. Quantifying manufacturing precision is a critical part of defining process capability and quality control procedures, but this has yet to be explored for these technologies. To address this, this paper presents the problem of evaluating the geometrical precision of manufactured parts and then proposes an approach based on geometric dimensioning and tolerancing (GD&T), commonly used in manufacturing. This is then applied in a case study in order to demonstrate the application of the technique for understanding and defining process capability, to enable more effective design rules that lead to greater confidence in the viability of part designs, and to provide the reliable performance metrics necessary for process improvement and control. The work concludes that the outlook for such techniques is positive and that the application will be beneficial in the future development of quality control procedures for 3DCP.
•A GD&T framework is developed to inspect the manufacturing precision of 3D printed concrete parts for process calibration.•Methods for the evaluation of the reproduction precision of features are presented through a test case study.•Sensitivity to process, material and design parameters was demonstrated, thus enabling process calibration and monitoring.•It is argued that methods based on GD&T are likely to underpin future quality control standards for 3D Concrete Printing.
This paper depicts a new CAT (Computer Aided Tolerancing) system called Quick GPS (Geometrical Product Specification), for assisting the designer when specifying the functional tolerances of a single ...part included in a mechanism, without any required complex function analysis.
The mechanism assembly is first described through a positioning table formalism. In order to create datum reference frames and to respect assembly requirements, an ISO based 3D tolerancing scheme is then proposed, thanks to a set of rules based on geometric patterns and TTRS (Technologically and Topologically Related Surfaces). Since it remains impossible to determine tolerance chains automatically, the designer must impose links between the frames. The CAT system that we developed here proposes ISO based tolerance specifications to help ensure compliance with the designer’s intentions, saving on time and eliminating errors.
This paper will detail both the set of tolerancing rules and the designer’s approach. The Quick GPS system has been developed in a CATIA V5 environment using CATIA VBA and CATIA CAA procedures.
Metal additive manufacturing (AM) has become a predominant process for manufacturing complex metal parts. However, research on controlling the geometric tolerances of the metal AM printed parts and ...assemblies is scarce. This paper presents a methodology to conduct a geometric tolerance and manufacturing assemblability study of the parts manufactured by metal AM. An assembly benchmark test artifact (ABTA) is designed to include mating features with given assembly conditions based on geometric tolerancing quantifiers. For virtual analysis, prediction phase ABTA samples are generated by using systematic and random field theory deviations. The prediction phase deviations are then calibrated using deviations from a numerical simulation based on thermo-mechanical finite element model of the part. These samples or ‘skin model shapes’ are subjected to geometric tolerance and assemblability study. For experimental validation of the method, geometric tolerance quantification and actual assembly was conducted on laser powder bed fusion (LPBF) fabricated parts. The comparative analysis of the experimental and virtual results validates the new methodology and its ability to provide reliable information regarding assemblability, size dimensions and geometric tolerances. The method can be extended to any AM process for performing a virtual tolerance and manufacturing assemblability study.
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•Benchmark designed with mating components to conduct experimental geometric tolerance and manufacturing assemblability study.•A hybrid approach presented for geometric tolerance estimation of the benchmark using random field theory and thermo-mechanical simulations.•The method is used to extract standardized geometric dimensioning and tolerancing (GD&T) quantifiers.•The method is validated with experimental GD&T characteristics and manufacturing assemblability.
This paper documents a novel fast method, named the Iterative Minimum Zone Algorithm (IMZA), for the evaluation of cylindricity deviation on a large number of measurement points, which plays a ...crucial role in the quality control of high-value products and components when a measurement is undertaken by a modern instrument, such as roundness tester, 3D laser/CT scanner. Firstly, the cylindricity deviation model and the minimum zone’s theoretical basis are presented. Secondly, the Six-point-subset (SPS) and the replacement strategy are introduced, together with the detailed algorithm. The method strictly adheres to the latest ISO definition. A comparison between the proposed method and the typical approaches is carried out on both simulated data and measured data. The results show that IMZA can fast and accurately evaluate the cylindricity deviation with a large number of measurement points.
•A fast iterative algorithm to evaluate cylindricity deviation.•Handling a large number of measurement points in a limited time.•Dealing with the data from various sampling strategies.•Outperforming other algorithms in comparison.
Weight reduction requirements in aerospace and automotive industry lead to an increased use of composite materials. However, composite parts cannot be bent like sheet metal parts. Hence, only low ...forces can be applied to close gaps between parts, caused by geometrical variation in parts and assembly fixtures. Shimming is therefore used to compensate for bad fitting, with increase cost as a consequence. This paper investigates how variation in assembly fixtures and parts give rise to variation in gaps and thereby also to variation in stress. Monte Carlo simulations are used to find the distribution of stress, which supports shimming strategies.
The purpose of this paper is to highlight current fundamental assumptions in the ISO Geometrical Product Specification (GPS) system and indicate recent trends in the GPS area standardization as well ...as point out selected new tools that are available for designers, manufacturing engineers, and quality staff. ISO/TC 213 systematic approach to developing a coherent system of the ISO GPS standards is shown. The content of the main fundamental standards that establish the base of the ISO GPS system is analysed. Limitations and lack of some standards are indicted. The relations between base concepts like features, operations, characteristics, and uncertainties are shown. Next global standards that refer to dimensioning and geometrical tolerancing are indicated and discussed. The current attempt to develop those standards as rule-based standards, not case-based standards is highlighted and advantages as well as drawbacks of such an approach are underlined. New projects and works on selected standards under development are also reported.
The cost and quality of an assembly depend on the processes used to manufacture its components. The specific processes and process settings are often dictated by the tolerances on the components. One ...long-standing challenge is allocating the assembly tolerance to components. Many methods have been proposed, most of which endeavor to minimize cost. We propose a tolerance allocation method that minimizes cost by jointly considering process variation and tolerance specifications. A cost model including processing cost, scrap cost, and quality loss is employed. The cost is minimized by a heuristic strategy. An overrunning clutch assembly case study is used to evaluate the method.
Applying the concept of Digital Twin in production processes supports the manufacturing of products of optimal geometry quality. This concept can be further supported by a strategy of finding the ...optimal combination of individual parts to maximise the geometrical quality of the final product, known as selective assembly technique. However, application of this technique has been limited to assemblies where the final dimensions are just function of the mating parts' dimensions and this is not applicable in sheet metal assemblies. This paper develops a selective assembly technique for sheet metal assemblies and investigates the effect of batch size on the improvements. The presented method utilises a variation simulation tool (Computer-Aided Tolerancing tool) and an optimisation algorithm to find the optimal combination of the mating parts. The approach presented is applied to three industrial cases of sheet metal assemblies. The results show that using this technique leads to a considerable reduction of the final geometrical variation and mean deviation for these kinds of assemblies. Moreover, increasing the batch size reduces the amount of achievable improvement in variation but increases the amount of achievable improvement in the mean deviation.
Product design requires the consideration of geometric models and representations that reflect shape deviations and support tolerance management issues. Computer-Aided Tolerancing (CAT) systems have ...been developed as simulation tools for modelling the effects of tolerances on digital product simulation. However, geometric variations cannot be addressed efficiently with regard to form deviations. This paper investigates the concepts of Skin Model Shapes, which provide a finite describability and the digital representation of the Skin Model concept, and their unified discrete geometry representation. New contributions to tolerance representation and analysis are presented. Applications and perspectives for CAT systems are highlighted as well.
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