Papers by Keyword: Calibration

Abstract: This article provides information about in-flight measurement of a small sport aircraft. The strain gauges were used as sensors for load monitoring on the nose landing gear structure. To obtain overall forces it was necessary to do the calibration procedure. After the calculation of strain gauge coefficients the equations for calculating of total force, total force direction and individual force components were determined. During test flights the data acquisition system was installed into the aircraft. The data from strain gauges were collected together with other flight parameters like speed, altitude and data from inertial measurement unit which determined the exact movements of the aircraft before landing. The data recorded during fifty-six flights were analysed to obtain loads acting in the aircraft structure. These results were compared with calculated values.

Abstract: The objective of this paper is to describe the calibration test method and conditions for MEMS-based IMUs including accelerometers and gyroscopes. This method is mainly used to derive deterministic error bounds within the acceptable range of accuracy. After a detailed description of the error model, the calibration process, test procedure, and test results as well as practical challenges are discussed. The presented method is simple, cheap and fast that takes only a few hours for calibration and validation of these sensors.

Abstract: When using the laser displacement sensor to measure distance, there is a deflection angle which exites between the direction of the laser beam and the direction of axis, this deflection angle has an impact on the final measurement result. This paper presented a calibration method of the laser beam’s direction, designed calibration device and ceramic calibration plate. In the process of calibrating, laser displacement sensor moves along Z-axis and Y-axis of machine, CCD camera takes the image of the spot projected by laser beam on the calibration plate, then calculate the laser beam’s direction based on the movement distance of laser displacement sensor and the spot’s position on calibration plate. Depend on the Mikron five-axis CNC machine tools, this paper describes the whole calibration process in details, the feasibility and accuracy of the method has been verified by experiment. Experimental results show that when the machine tool’s accuracy is within 0.002mm, the calibration error of laser beam’s direction can be controlled within the range of 0.05°.

Abstract: Dimensional inspections in manufactured workpieces allow assess the quality of the manufacturing process, in this context the quality and development of measurement systems are issues addressed by many researchers. The coordinate measuring machines (CMMs) are versatile systems, can measure complex geometries quickly and accurately. Positional errors are parts of volumetric error and affect the correct positioning of probe in CMMs or of the tool in machine tools. Faced with this, the purpose this investigation is show a method to calibrate the positional errors in a bridge-type coordinate measuring machine, this method collects data in dynamic mode and reduces cyclic errors. The calibration of positional errors was performed using laser interferometry in the “on-the-fly” mode and a method to reduce cyclic errors was applied. The highest value of position error occurred in x axis with value positive of 10μm in the position of 220mm, while in the y and z axis the higher absolute values were 2μm and 6μm respectively. From calibration and compensating of positional errors it is possible to reduce the effects of the volumetric errors in machines with axis of linear displacements as the CMMs and machine tools.

Abstract: The CMM (coordinate measuring machines) are able to perform dimensional inspections in workpieces with complex geometries, in a short time compared to conventional methods, however, errors on volume of CMM harm the performance of measurement. Faced with this, the purpose this investigation is to identify regions in the machine with large and small values of volumetric errors. The mapping of volumetric error is performed by optimization of objective function with SQP method. The objective function is defined by modeling errors of the CMM using a method of the homogeneous transformation, and, by calibration curves of individual errors. The optimization allowed to obtain the smallest value of volumetric error, 1.1796 μm, located near the linear encoder of the y axis. The mapping the volumetric error by optimization allows to know regions with minor harm the performance of measurement, therefore, it's possible to select regions of measurement to obtain reliable results.

Abstract: Modern production technology comprises automatic devices with numerically controlled driving axes in a large extent. Those devices – so called CNCs - are financially available not only to large factories but to small and medium enterprises as well. When selecting the CNC machine to be purchased, ratio between the financial aspects and the machine performance is evaluated very thoroughly. This brings a constant pressure on CNC machines producers who seek for modern approaches enhancing performance of their products. The following paper introduces some theoretical aspects dealing with the positioning accuracy of numerically controlled axes.

Abstract: Diathermy is commonly used treatment method for pain relief in musculoskeletal tissue, rheumatisms, inflammation etc., by which the increased temperature in tissue induces better blood perfusion and quickens the healing process. But improper maintenance and incorrect handling might lead to degrade the output power or may cause serious burns, respectively. So correct regular QA measurements for the output power would be necessary, in order to give the correct and safe treatment plan. A suitable tissue phantom is then needed to accomplish this task. For this purpose, a glycerol-based solid tissue phantom has been self-fabricated with insertion of four precission temperature sensors (LM 35) at locations of of 1.0 cm, 1.5 cm, 2.0 cm, and 2.5 cm from the surface (each of which are 2 cm laterally separated). Prior calibration of these four sensors for temperature range of 20 - 50°C (using a calibrated temperature calibrator) show very good accuracy and precission properties. The phantom is then tested by exposing it with RF waves output of SWD unit with time variation of 2-14 min (step 2 min), and output power variation of 20% - 80% of its maximum power (incremental step of 20%).

Abstract: A new test method of set fibre concrete homogeneity in finished steel fibre-concrete structure is described in this contribution. The method is based on measurements of the changes in magnetic field strength of permanent magnets which are induced by a change of wire distribution in steel fibre-concrete structure. It is evident from the method described in this contribution that the test is characterized as a local failure test using small diameter core drill. It is a semi-destructive method. Its application in practice does not affect safety and reliability of steel fibre-concrete structures.Additionally to the method described, an example of its application for the assessment of fibre concrete homogeneity of the segmental tunnel lining parts is described. The results of partial measurements give both information about fibre concrete homogeneity in a segment and a number and a selection of points for homogeneity measurements which are subject to the size and the production method of such segment.

Abstract: The ANFIS algorithm was first applied to calibration modeling of the multi-hole pitot tube in this study. Owing to its capability of efficient learning, easy implementation and excellent explanation through fuzzy rules, ANFIS can help identify the dominant parameters and construct fuzzy learning system. After determination of the ANFIS structure from the calibration data, the network of pitot tube calibration parameters was established and the correlation among non-dimensional pressure coefficients, flow angle and flow velocity were constructed as well. Meanwhile, the air velocity can be predicted based on the measurements of flow angles and flow angle coefficients. It can reach to a high consistency of 0.0068 with the original data after iteration. Eventually, ANFIS can be integrated with real-time data acquisition system and wind tunnel due to its programmability. A large database consisting of flow properties, flow angles and the non-dimensional pressure coefficients can be efficiently established and will be helpful for shortening the calibration procedures.

Abstract: We propose a tool to calibrate the coefficient variables of the Steinhart–Hart equation, which are used in temperature measurement with a negative temperature coefficient thermistor. The previous method modifies the coefficient variables manually, but the proposed tool takes a measured temperature and automatically modifies the coefficient variable. The proposed calibration tool provides a graphical user interface program for the convenience of users. It is applied to the 4-point temperature measurement of polymerase chain reaction and has a degree of precision of ±0.1 °C in the temperature measurement evaluation