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1

Analysis and application of real-time compensation of positioning precision of the turntable with a harmonic function

Zhou Yi, Zhu Weibin, Shu Yi, Huang Yao, Zou Wei, Xue Zi

Metrology and Measurement Systems

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2022

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Vol. 29, nr 3

553--571

EN

In order to guarantee the accuracy of turntable angle measurement, a real-time compensation method for turntable positioning precision based on harmonic analysis is proposed in this paper. Firstly, the principle and feasibility of the real-time compensation method are analysed, and a detailed description of harmonic compensation is provided herein. Secondly, we analyse the relationships between the surface number of the polygon with the compensation order of the harmonic function and its corresponding compensation accuracy. The effects of the iterations number and the data width on calculation accuracy in the coordinate rotation digital computer (CORDIC) algorithm are analysed and the quantization models of the approximation error and rounding error of the CORDIC algorithm are established. Then, the calculation of the harmonic error function and real-time compensation processes are implemented on a field programmable gate array (FPGA) chip. The resource occupation and time delay of the phase angle calculation and the harmonic component calculation are discussed separately. Finally, the validity of the harmonic compensation method is proven through comparing the compensation effect with that of linear interpolation and the polynomial compensation method. The influences of the compensation order, the iterations number and the data width on the compensation results are demonstrated by simulation. A test platform with a laboratory-made FPGA circuit is built to evaluate the effect of real-time compensation with the harmonic function and the positioning error compensation can be performed within 760 ns. The results confirmed the effectiveness of the harmonic compensation method, revealing an improvement of the positioning precision from 54.21ʹʹ to 1.63ʹʹ, equivalent to 96.99% reduction in positioning error.

2

Parallel computing in automation of decoupled fluid-thermostructural simulation approach

Glänzel Janine, Naumann Andreas, Kumar Tharun Suresh

Journal of Machine Engineering

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2020

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Vol. 20, No. 2

39--52

EN

Decoupling approach presents a novel solution/alternative to the highly time-consuming fluid-thermal-structural simulation procedures when thermal effects and resultant displacements on machine tools are analyzed. Using high dimensional Characteristic Diagrams (CDs) along with a Clustering Algorithm that immensely reduces the data needed for training, a limited number of CFD simulations can suffice in effectively decoupling fluid and thermal-structural simulations. This approach becomes highly significant when complex geometries or dynamic components are considered. However, there is still scope for improvement in the reduction of time needed to train CDs. Parallel computation can be effectively utilized in decoupling approach in simultaneous execution of (i) CFD simulations and data export, and (ii) Clustering technique involving Genetic Algorithm and Radial Basis Function interpolation, which clusters and optimizes the training data for CDs. Parallelization reduces the entire computation duration from several days to a few hours and thereby, improving the efficiency and ease-of-use of decoupling simulation approach.

3

Parameterization of environmental influences by automated characteristic diagrams for the decoupled fluid and structural-mechanical simulations

Glänzel Janine, Kumar Tharun Suresh, Naumann Christian, Putz Matthias

Journal of Machine Engineering

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2019

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Vol. 19, No. 1

98--113

EN

Thermo-elastic effects contribute the most to positioning errors in machine tools especially in operations where high precision machining is involved. When a machine tool is subjected to changes in environmental influences such as ambient air temperature, velocity or direction, then flow (CFD) simulations are necessary to effectively quantify the thermal behaviour between the machine tool surface and the surrounding air (fluid). Heat transfer coefficient (HTC) values effectively represent this solid-fluid heat transfer and it serves as the boundary data for thermo-elastic simulations. Thereby, deformation results can be obtained. This two-step simulation procedure involving fluid and thermo-structural simulations is highly complex and time-consuming. A suitable alternative for the above process can be obtained by introducing a clustering algorithm (CA) and characteristic diagrams (CDs) in the workflow. CDs are continuous maps of a set of input variables onto a single output variable, which are trained using data from a limited number of CFD simulations which is optimized using the clustering technique involving genetic algorithm (GA) and radial basis function (RBF) interpolation. The parameterized environmental influences are mapped directly onto corresponding HTC values in each CD. Thus, CDs serve as look-up tables which provide boundary data (HTC values along with nodal information) under several load cases (combinations of environmental influences) for thermo-elastic simulations. Ultimately, a decoupled fluid-structural simulation system is obtained where boundary (convection) data for thermo-mechanical simulations can be directly obtained from CDs and would no longer require fluid simulations to be carried out again. Thus, a novel approach for the correction of thermo-elastic deformations on a machine tool is obtained.

4

Efficient quantification of free and forced convection via the decoupling of thermo-mechanical and thermo-fluidic simulations of machine tools

Glaenzel J., Ihlenfeldt S., Naumann C., Putz M.

Journal of Machine Engineering

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2018

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Vol. 18, No. 2

41--53

EN

Thermo-elastic deformations represent one of the main reasons for positioning errors in machine tools. Investigations of the thermo-mechanical behaviour of machine tools, especially during the design phase, rely mainly on thermo-elastic simulations. These require the knowledge of heat sources and sinks and assumptions on the heat dissipation via convection, conduction and radiation. Forced convection such as that caused by moving assemblies has both a large influence on the heat dissipation to the surrounding air. The most accurate way of taking convection into account is via computational fluid dynamics (CFD) simulations. These simulations compute heat transfer coefficients for every finite element on the machine tool surface, which can then be used as boundary conditions for accurate thermo-mechanical simulations. Transient thermo-mechanical simulations with moving assemblies thus require a CFD simulation during each time step, which is very time-consuming. This paper presents an alternative by using characteristic diagrams to interpolate the CFD simulations. The new method uses precomputed thermal coefficients of a small number of load cases as support points to estimate the convection of all relevant load cases (i.e. ambient conditions). It will be explained and demonstrated on a machine tool column.

5

Linear positioning errors of 3-axis machine tool

Józwik J., Mazurek P., Wieczorek M., Czwarnowski M

Applied Computer Science

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2015

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Vol. 11, no 2

86--94

EN

This paper presents results of 3-axis CNC machine tool diagnostics performed with XL-80 laser interferometer and XC-80 environmental compensation unit, including pressure, humidity and temperature sensors. Furthermore, the paper includes the methodology and results of conducted measurements of linear positioning errors, which supplied data for further analysis. The conclusion section presents important results of conducted experiments. Measurement results were presented in figures, charts and tables.

6

Supervision of production of metal roof tiles

Płaska S., Cechowicz R., Wolszczak P.

Advances in Manufacturing Science and Technology

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2013

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Vol. 37, nr 4

61--68

EN

This paper presents the characteristic of the production of sheet metal roofing tiles. The basic problem affecting the quality of the product was identified to be the repeatability of the metal sheet positioning and the cross ribbing. A measurement and control system was proposed for controlling the movement of the metal sheet and to automatically correct positioning errors. Presented results illustrate the effects of the solutions in the industrial environment.

PL

W pracy przedstawiono charakterystykę produkcji pokryć dachowych z blachy – blachodachówki. Wskazano podstawowe kryterium oceny jakości wyrobów: uzyskanie powtarzalności podziałki przetłoczeń poprzecznych. Przedstawiono rozwiązania układu do pomiaru przemieszczenia podawanej blachy, pomiaru podziałki przetłoczeń oraz rozwiązania automatycznego korygowania błędów pozycjonowania i nadzorowania linii wytwórczej. Przeprowadzono analizę efektów zastosowanych rozwiązań w warunkach przemysłowych.