Automatic calibration system for micro-displacement devices

With the industrial development and the advances in micro - displacement technology, the demands on piezo transducers are increasing. For piezo transducers, the error inspections of the non-linearity and the hysteresis are necessary procedure before piezo transducers utilized. Due to the possible decline or damage during the employment of the transducers, it is important to provide the automatic calibration system. In this investigation, a self-developed automatic calibration system for micro-displacement devices is proposed. The automatic system according to the international specification of ASTM-E2309 has been developed. This system designed for the calibration of piezo transducers is based on the interferometric structure of the common optical path and possesses the resolution of the nanometer order. The experimental verifications demonstrate that the repeatability of the Fabry-Perot interferometer is less than 11 nm. Experimental results of the synchronic measurement with the self-developed interferometer and a commercial interferometer reveal that the differences of the maximum nonlinearity error and maximum hysteresis error are less than 1%. With the proposed correct equations, the maximum non-linearity error can be minimized to 1% and the maximum hysteresis error will be less than 5.2%

An Online Simultaneous Measurement of the Dual-Axis Straightness Error for Machine Tools

Vertical straightness errors are the key factor that affects the flatness of the workpiece during vertical machining. Traditionally, the individually measured and fitted vertical straightness errors of the X and Y axes are used to compensate the Z axis and, thus, obtain the flatness of the working table of the machine tool. However, it is difficult to measure and compensate the vertical straightness error of the desired position on the working table, not to mention the centroid variation effect of the working table on the measured data. In this study, an online dual-axis measurement system with repeatability (3σ) of 2.46 μm is developed to simultaneously measure X-axis and Y-axis straightness errors of the desired position of a working table. Furthermore, the measured data are utilized to establish a flatness error model to reduce the vertical straightness error of the working table such that the repeatability (3σ) of the measured flatness may be kept within a range of 0.65 μm

An Online Simultaneous Measurement of the Dual-Axis Straightness Error for Machine Tools

Vertical straightness errors are the key factor that affects the flatness of the workpiece during vertical machining. Traditionally, the individually measured and fitted vertical straightness errors of the X and Y axes are used to compensate the Z axis and, thus, obtain the flatness of the working table of the machine tool. However, it is difficult to measure and compensate the vertical straightness error of the desired position on the working table, not to mention the centroid variation effect of the working table on the measured data. In this study, an online dual-axis measurement system with repeatability (3σ) of 2.46 μm is developed to simultaneously measure X-axis and Y-axis straightness errors of the desired position of a working table. Furthermore, the measured data are utilized to establish a flatness error model to reduce the vertical straightness error of the working table such that the repeatability (3σ) of the measured flatness may be kept within a range of 0.65 μm

Thermal displacement prediction model with a structural optimized transfer learning technique

Thermal deformation of the spindle accounts for a large proportion of existing errors. After gathering data on thermal deformation through an experiment with a machine tool, AI algorithms were used in this study to predict the displacement of a cutting tool caused by heat deformation. Thermal displacement and temperature data were entered into models constructed using several machine learning algorithms. These models were then quantitatively evaluated in terms of their accuracy and compared to each other. Subsequently, transfer learning and hyperparameter tuning were conducted to produce a model with optimal prediction capability. The experimental results revealed that after machine learning models were trained using data collected on the first day of the experiments, their predictions based on data collected on the second day of the experiments were rife with severe prediction errors. This outcome indicated that experimental data gathered at different times weakened the models’ predictive abilities. Thus, to increase the prediction accuracy and prevent time from being wasted on repeated training, transfer learning were incorporated with model optimization. Finally, this approach achieved excellent R2 scores of 0.99941, 0.99964, and 0.99902 for the prediction of displacement in the x-, y-, and z-directions

Mixed convective heat-transfers in a porous channel with sintered copper beads

For a fixed porosity, a higher flow rate causes an increase in the efficiency of the heat exchange between the fluid and the solid phases for the heat sink. As the porosity of the sintered porous medium decreases, the specific contact surface of the fluid increases. This causes a higher heat-transfer rate between the fluid and the solid phases for a constant flow-rate. The sintered test section is made of three diameters of copper beads of 0.71, 0.84 or 1.15 mm. The characteristics of the wall temperature-distribution with a constant heat-flux were measured. This study also reveals the local wall temperature-distributions and heat-transfer coefficients for various Reynolds numbers and heat fluxes.Convective heat-transfer Sintered porous channel Heat-transfer coefficient

A Geometric Error Measurement System for Linear Guideway Assembly and Calibration

Geometric errors, such as straightness, perpendicularity, and parallelism errors are determinant factors of both the accuracy and service life of a linear guideway. In this study, a multipurpose geometric error measurement system was mainly composed of a laser source and an in-lab-developed optical module is proposed. Two adjustment methods were used for the in-lab-developed optical module to calibrate the altitude angle of the pentaprism: The first one is designed for ease of operation based on Michelson principle using a laser interferometer as the light receiver, and the second is aimed at high calibration repeatability based on the autocollimator principle using the quadrant detector (QD) to replace the light receiver. The result shows that the residual errors of the horizontal straightness and the vertical straightness are within ±1.3 µm and ±5.3 µm, respectively, when referred to as the commercial laser interferometer. Additionally, the residual errors of perpendicularity and parallelism are within ±1.2 µm and ±0.1 µm, respectively, when referred to as the granite reference block

Investigation on the Differential Quadrature Fabry–Pérot Interferometer with Variable Measurement Mirrors

Due to the common path structure being insensitive to the environmental disturbances, relevant Fabry–Pérot interferometers have been presented for displacement measurement. However, the discontinuous signal distribution exists in the conventional Fabry–Pérot interferometer. Although a polarized Fabry–Pérot interferometer with low finesse was subsequently proposed, the signal processing is complicated, and the nonlinearity error of sub-micrometer order occurs in this signal. Therefore, a differential quadrature Fabry–Pérot interferometer has been proposed for the first time. In this measurement system, the nonlinearity error can be improved effectively, and the DC offset during the measurement procedure can be eliminated. Furthermore, the proposed system also features rapid and convenient replacing the measurement mirrors to meet the inspection requirement in various measuring ranges. In the comparison result between the commercial and self-developed Fabry–Pérot interferometer, it reveals that the maximum standard deviation is less than 0.120 μm in the whole measuring range of 600 mm. According to these results, the developed differential Fabry–Pérot interferometer is feasible for precise displacement measurement