Precision positioning of an object relative to a reference point is a common task in many activities of production engineering. Sensor technologies for single axis measurement, either linear or rotary, which form the fundamentals of measurement technologies for precision positioning, are reviewed. Multi-axis coordinate measurement methods such as triangulation and multilateration, as well as Cartesian and polar systems for specifying the position in a plane or three-dimensional (3D) space are then presented, followed by a discussion on traceability and standards. Some advanced applications of measurement technologies for precision positioning in manufacturing industries are also demonstrated.

Measurement technologies for precision positioning

Large-Scale Metrology – An Update

On-machine and in-process surface metrology for precision manufacturing

This paper first reviews different methods of designing thermal error models, before concentrating on employing ANFIS models.The GM(1, N) model and fuzzy c-means clustering are used for variable selection, which is capable of simplifying the system prediction model.The results of the study show that the ANFIS-FCM model is superior in terms of the accuracy of its predictive ability with the benefit of fewer rules. Thermal errors can have significant effects on CNC machine tool accuracy. The errors come from thermal deformations of the machine elements caused by heat sources within the machine structure or from ambient temperature change. The effect of temperature can be reduced by error avoidance or numerical compensation. The performance of a thermal error compensation system essentially depends upon the accuracy and robustness of the thermal error model and its input measurements. This paper first reviews different methods of designing thermal error models, before concentrating on employing an adaptive neuro fuzzy inference system (ANFIS) to design two thermal prediction models: ANFIS by dividing the data space into rectangular sub-spaces (ANFIS-Grid model) and ANFIS by using the fuzzy c-means clustering method (ANFIS-FCM model). Grey system theory is used to obtain the influence ranking of all possible temperature sensors on the thermal response of the machine structure. All the influence weightings of the thermal sensors are clustered into groups using the fuzzy c-means (FCM) clustering method, the groups then being further reduced by correlation analysis.A study of a small CNC milling machine is used to provide training data for the proposed models and then to provide independent testing data sets. The results of the study show that the ANFIS-FCM model is superior in terms of the accuracy of its predictive ability with the benefit of fewer rules. The residual value of the proposed model is smaller than ?4µm. This combined methodology can provide improved accuracy and robustness of a thermal error compensation system.

The application of ANFIS prediction models for thermal error compensation on CNC machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.

A review on spindle thermal error compensation in machine tools

Thermal issues in machine tools

Measuring large 3D structures using four portable tracking laser interferometers

The paper reports on the development of a new guideline for acceptance and verification of optical 3-D measuring system, e.g. photogrammetric systems or fringe-projection systems. The work has started in 1996, initiated by the working group “Close-range Photogrammetry” of the German Society for Photogrammetry and Remote Sensing (DGPF) and by the working group “Co-ordinate measuring machines” of the German Society for measurement and automatic control (VDI/VDE-GMA). A new VDI working group has been established joining almost all important users and manufacturers of optical 3-D systems. The new guideline VDI 2634 proposes procedures for the acceptance of point-wise photogrammetric systems (part 1), and area-based surface measurement systems (part 2). For both groups of systems the “error of length measurement” has been selected as the most significant criterion for an over all performance assessment. Surface measurement systems shall also be checked according to “error of flatness measurement” and “probing error”. Suitable calibrated reference objects are proposed as well.

https://www.isprs.org/proceedings/XXXIII/congress/part5/493_XXXIII-part5.pdf

Recommendations for an acceptance and verification test of optical 3-d measurement systems

A new procedure and reference standards for specifying the structural resolution in coordinate metrology traceable to the SI unit the metre are proposed. With the definition of the structural resolution, a significant gap will be closed to complete 'acceptance and verification tests' of the coordinate measuring systems (CMSs) which are specified in the ISO 10360 series dealing with tactile sensors, optical sensors, and x-ray computed tomography measurement systems (CTs). The proposed new procedure uses reference standards with circular rounded edges. The idea is to measure the radius of curvature on a calibrated round edge structure. From the deviation between the measured and the calibrated radius, an analogue Gaussian broadening of the measurement system is determined. This value is a well-defined and easy-to-apply measure to define the structural resolution for dimensional measurements. It is applicable to CMSs which are based on different sensing principles, e.g. tactile, optical and CT systems. On the other hand, it has a physical meaning similar to the classical optical point-spread function. It makes it possible to predict which smallest details the CMS is capable of measuring reliably for an arbitrary object shape. The theoretical background of the new procedure is given, an appropriate reference standard is described and comparative, quantitative measurement data of CMSs featuring different sensors are shown.

https://iopscience.iop.org/article/10.1088/0957-0233/25/6/064015/pdf

Procedure and reference standard to determine the structural resolution in coordinate metrology

The method involves using one or more hinged length-measuring systems (1). A large number of lengths are measured optically to a reference element fixed to the tool or co-ordinate measuring device. A two-dimensional network is determined from the lengths by trilateration. The network is used to determine the geometry variations of the axes of the device to be tested.

Method to detect geometrical variations of co-ordinate measuring devices or tools; involve measuring large number of lengths optically and determining two-dimensional network by trilateration

Klaus Wendt

Papers

Thermal issues in machine tools

Measuring large 3D structures using four portable tracking laser interferometers

Recommendations for an acceptance and verification test of optical 3-d measurement systems

Procedure and reference standard to determine the structural resolution in coordinate metrology

Method to detect geometrical variations of co-ordinate measuring devices or tools; involve measuring large number of lengths optically and determining two-dimensional network by trilateration