Tung-Hui Hsu

Development of a laser-based high-precision six-degrees-of-freedom motion errors measuring system for linear stage

This article presents a useful measuring system for the simultaneous measurement of six-degrees-of-freedom motion errors of a moving stage. The system integrates a miniature fiber coupled laser interferometer with specially designed optical paths and quadrant detectors, capable of measuring six-degrees-of-freedom motion errors. Using this model, the proposed measuring method provides rapid performance, simplicity of setup, and preprocess verification of a linear stage. The experimental setups and measuring procedures, and a systematic calculated method for the error verification are presented in the paper. The system’s resolution of measuring straightness error component is about 25nm. The resolution of measuring the pitch and yaw angular error component is about 0.06arcs. With the comparison between the HP calibration system and the proposed system in the measuring range of 120mm, the system accuracy of measuring straightness error and angular error is within the range ±0.6μm and ±0.3arcs.

The application of the double-readheads planar encoder system for error calibration of computer numerical control machine tools

Abstract THis paper presents a useful measuring method for rapidly verifying geometric errors using a double-readheads planar encoder system. The system is capable of comparing the displacement measurements between two parallel lines simultaneously when the machine axes are moved. With the calculated model and the various specified test paths, the proposed measuring method provides rapid performance, simplicity of set-up, low cost and pre-process verification of computer numerical control (CNC) machine tools. Complete set-ups and procedures for geometric error verification are clearly presented. Also, the proposed system tested the dynamic performance of the CNC machine tools. It is an integrated system that can complete both dynamic performance and the geometric verification of CNC machine tools.

Automatic straightness measurement of a linear guide using a real-time straightness self-compensating scanning stage

Abstract In this paper a method is developed for straightness measurement of a linear guide by using a straightness self-compensating stage with an optical straightness measuring system, an eddy current sensor, and a cross-roller type compensation stage. Both the compensation stage and the optical straightness system were set up on a scanning stage to measure the straightness error of the scanning stage. The measured straightness error was fed back to the control system to compensate directly in real time. Thus, straightness of a linear guide without the added straightness error of the scanning stage could be measured. The Hewlett Packard laser straightness calibration system was used to verify the real-time compensated results. Straightness error of the scanning stage was compensated from the worst straightness error of 20 μm/150 mm to 0.9 μm/150 mm. The eddy current sensor measured straightness of the linear guide and the measured result matched the result obtained by the coordinate measuring machine.

Developed of a Multi-Degree of Freedoms Measuring System and an Error Compensation Technique for Machine Tools

In this paper, a new measuring system, Multi-Degree of Freedoms Measuring System(MDFMS), is presented. It is integrated a miniature laser interferometer with a DVD pickup and straightness measuring optical system. The five-degrees of freedoms motion errors to simultaneously measure machine tools. And, it reduces the overall time for measuring the geometric errors. The resolution and accuracy of straightness measurement are about 0.3μm and the resolution and accuracy of the angular error measurement are about 0.6arcsecs within the measuring range of 150mm. MDFMS is characteristic by simple set up, low cost, fast measuring and high accuracy for machine tools.

Development of a DVD pickup-based four-degrees- of-freedom motion error measuring system for a single-axis linear moving platform

Abstract In this study, a simple and high-resolution four-degrees-of-freedom (4-DOF) motion error measuring system based on DVD pickup has been proposed. It can simultaneously measure the horizontal straightness error and three angular errors of a single-axis linear moving platform. The horizontal straightness error is measured based on the focus technique of DVD pickup and the inverse algorithm is used to solve pitch, yaw, and roll angular errors through the kinematic analysis. The grating is mounted on the moving axis of a single-axis linear moving platform and reflects incident laser beam into several diffractive rays. Photodiode IC (PDIC) of DVD pickup is set up for detecting the focus error signal (FES) of zero-order diffraction ray from grating and quadrant detectors are set up for detecting the position of ±1st-order diffraction rays from grating. The 4-DOF motion error measuring system detected the three angular errors with a related accuracy of about ±1 arc sec for a measuring range of ±100 arc sec, and detected horizontal straightness with a related accuracy of about ±2 μm for a measuring range of ±150 μm.

Development of a straightness measuring system and compensation technique using multiple corner cubes for precision stages

Abstract At present, the accuracy of precision manufacture is most affected by straightness errors, so the measurement and compensation of these errors are very important. In the current paper, three measurement systems for straightness are presented; they are characterized by simple set-up, online measuring, low cost, and sub-micrometre accuracy achieving 0.2 μm. Experimental results show that these three measurement systems can be applied to implement a compensation system which comprises one among them, an Elmo controller, and a dSPACE controller, and accomplish static compensation and dynamic compensation in the dual linear-axis stage. The accuracies of the static and dynamic compensation achieve ± 1 μm and ± 2.5 μm, respectively.

Development of A four-Degrees-of-Freedom Diffraction Sensor

The development of a diffraction-type four-degrees-of-freedom sensor based on the three-dimensional diffraction method and collimation method is described in this paper. This sensor is designed to be integrated with a linear laser encoder to allow five-degrees-of-freedom measurement. It is composed of a miniature collimation-type sensor, a reflective diffraction grating and a quadrant detector to simultaneously measure a straightness error and three rotational angles. Based on the diffraction method, the reflective diffraction grating reflects the incident laser from the collimation-type sensor to several diffractive laser rays and only the 0 and +1-order diffractive laser rays are detected by the collimation-type sensor and a quadrant detector respectively. According to the changed spot positions of the diffraction laser lights on the collimation-type sensor and the quadrant detector, a straightness error and the three rotational errors can be solved simultaneously.

The Application of the Dual-Beam Laser Interferometer for Calibration Precision Machine ToolsAnwendung eines Zweistrahl-Laserinterferometers zur Kalibrierung von Präzisionswerkzeugen

Abstract In this paper, a dual-beam laser interferometer measurement system for precision machine tools was presented. The straightness measurement module and the angular measurement module were combined to form this measurement system such that the operations of precision machine tools, the positioning, vertical straightness, horizontal straightness, pitch and yaw, can be obtained. The resolution of the positioning, straightness and angle has achieved 0.1 nm, 1 nm and 0.1 arcsec, respectively. The performance of this measurement system has been proved by experiments.

A 3D Error Measurement System for CNC Machining Tools

A new system for measuring the errors of three-axis machines is presented in this paper. It is composed of a planar encoder system and a magnetic telescoping ball bar. The individual signals of three-axis displacement can be simultaneous obtained. The errors of the three-axis machines, geometric error, kinematic error, wobble error and volumetric error, can be effectively measured. The system is characterized by short set up time, low capital requirement, high measuring speed and high accuracy.