Accuracy improvement of linear stages using on-machine geometric error measurement system and error transformation model.

In order to improve the accuracy of linear stages, a compact, portable and easy installation of a six-degree-of-freedom (6DOF) geometric error measurement system, in which two mirrors with special position and orientation are innovatively regarded as the sensitive elements of the roll error, is proposed. A set of combined focus lenses is integrated into the 6DOF measurement system to improve the resolution of the roll error. The accuracy of a linear stage is evaluated by the positional errors at the functional point, which is located at the working volume of a linear stage.

Self-compensation method for dual-beam roll angle measurement of linear stages.

In this paper, a self-compensation method for improving the accuracy of roll angle measurement of a linear stage caused by the non-parallelism of dual-beam due to time-dependent mechanical deformation of the support is proposed and integrated into a 5-DOF sensor to verify the feasibility. The non-parallelism between two laser beams is online real-time monitored by a pair of small autocollimator units. Through the ray-tracing analysis, the method to separate the roll angle of the moving stage and non-parallelism induced roll error is determined.

A five degrees-of-freedom errors measurement system for rotary axis with reference laser for reference axis alignment.

This paper proposes a five degrees-of-freedom measurement system for measuring geometric errors of the rotary axis. To align the measured rotary axis with the reference axis, a diode laser is used to represent the rotary axis of the measured rotation stage. Based on the proposed measurement system, a model for separating the position independent geometric errors and position dependent geometric errors of the measured rotary axis from the measured value is established and verified by measurement experiments.

Design of a compact four degree-of-freedom active compensation system to restrain laser's angular drift and parallel drift.

The laser collimation technique is widely used in science research and industrial applications. The pointing stability will be affected by the common problem of beam drift. A compact active compensation system is presented in this paper.

Real-Time Correction and Stabilization of Laser Diode Wavelength in Miniature Homodyne Interferometer for Long-Stroke Micro/Nano Positioning Stage Metrology.

A low-cost miniature homodyne interferometer (MHI) with self-wavelength correction and self-wavelength stabilization is proposed for long-stroke micro/nano positioning stage metrology. In this interferometer, the displacement measurement is based on the analysis of homodyne interferometer fringe pattern. In order to miniaturize the interferometer size, a low-cost and small-sized laser diode is adopted as the laser source.

Modeling and Optimal Design for a High Stability 2D Optoelectronic Angle Sensor.

The structural deformations caused by environmental changes in temperature, vibration, and other factors are harmful to the stability of high precision measurement equipment. The stability and optimal design method of a 2D optoelectronic angle sensor have been investigated in this study. The drift caused by structural deformations of the angle sensor has been studied and a drift error model has been achieved.

Error Analysis and Compensation of a Laser Measurement System for Simultaneously Measuring Five-Degree-of-Freedom Error Motions of Linear Stages.

A robust laser measurement system (LMS), consisting of a sensor head and a detecting part, for simultaneously measuring five-degree-of-freedom (five-DOF) error motions of linear stages, is proposed and characterized. For the purpose of long-travel measurement, all possible error sources that would affect the measurement accuracy are considered. This LMS not only integrates the merits of error compensations for the laser beam drift, beam spot variation, detector sensitivity variation, and non-parallelism of dual-beam that have been resolved by the author's group before, but also eliminates the crosstalk errors among five-DOF error motions in this study.

An Embedded Sensor System for Real-Time Detecting 5-DOF Error Motions of Rotary Stages.

The geometric error motions of rotary stages greatly affect the accuracy of constructed machines such as machine tools, measuring instruments, and robots. In this paper, an embedded sensor system for real-time measurement of two radial and three angular error motions of a rotary stage is proposed, which makes use of a rotary encoder with multiple scanning heads to measure the rotational angle and two radial error motions and a miniature autocollimator to measure two tilt angular errors of the axis of rotation. The assembly errors of the grid disc of the encoder and the mirror for autocollimator are also evaluated and compensated.

Robust roll angular error measurement system for precision machines.

This paper presents a robust and low-cost roll angle measurement system (RAMS) on the basis of two parallel beams in association with two position detectors. The commonly occurring influences of beam drift, beam diameter, and intensity variations, and non-parallelism of dual-beam on the roll angular error measurement of precision linear stages are thoroughly considered and reduced. The effectiveness of the designed system and proposed methods were demonstrated by a series of experiments.

Development of a Micro/Nano Probing System Using Double Elastic Mechanisms.

To meet the requirement of high precision measurement of coordinate measurement machine system, a compact microprobe has been designed for 3D measurement in this paper. Aiming to reduce the influences of signal coupling during the probing process, the probe has been designed by adopting two elastic mechanisms, in which the horizontal and vertical motions of the probe tip can be separated by differential signals of quadrant photodetectors in each elastic mechanism. A connecting rod has been designed to transfer the displacement of the probe tip in vertical direction from lower to upper elastic mechanisms.

Development of a High-Sensitivity Optical Accelerometer for Low-Frequency Vibration Measurement.

Low-frequency vibration is a harmful factor that affects the accuracy of micro/nano-measuring machines. Low-frequency vibration cannot be completely eliminated by passive control methods, such as the use of air-floating platforms. Therefore, low-frequency vibrations must be measured before being actively suppressed.

Low cost, compact 4-DOF measurement system with active compensation of beam angular drift error.

In this paper, a compact four-degree-of-freedom (4-DOF) measurement system is presented. With a special optical configuration, the pitch error, yaw error, and two straightness errors of the moving target are able to be detected by only a single laser beam from a collimated laser diode. A 2D hybrid mirror angle steering mount is designed to perform the large angle turning for the axis alignment and very fine angle tuning by PZT actuators for real-time beam drift compensation.

Linear diffraction grating interferometer with high alignment tolerance and high accuracy.

We present an innovative structure of a linear diffraction grating interferometer as a long stroke and nanometer resolution displacement sensor for any linear stage. The principle of this diffractive interferometer is based on the phase information encoded by the ±1st order beams diffracted by a holographic grating. Properly interfering these two beams leads to modulation similar to a Doppler frequency shift that can be translated to displacement measurements via phase decoding.

Flexible temperature sensor array based on a graphite-polydimethylsiloxane composite.

This paper presents a novel method to fabricate temperature sensor arrays by dispensing a graphite-polydimethylsiloxane composite on flexible polyimide films. The fabricated temperature sensor array has 64 sensing cells in a 4×4 cm2 area. The sensor array can be used as humanoid artificial skin for sensation system of robots.