A compact measurement system to measure four-degree-of-freedom (4-DOF) geometric errors of machine tools is presented in this paper. The angular errors and the straightness errors of the machine tools can be detected simultaneously by only one single laser beam, one position-sensitive detector (PSD) and one four-quadrant photodetector (QPD) through a simple optical configuration. The 4-DOF system has been calibrated and an API XD laser system is used as a reference. The straightness and angular measurement range of the system are ± 100 μm and ± 200 arc-sec, respectively. The resolution of straightness and angle measurement is 0.1 μm and 0.5 arc-sec, respectively. The developed measurement system was assembled on a machine tool with a carrier platform which has been moved 800 mm with an interval of 50 mm. A similar measurement was also conducted by the API XD laser system. The measuring results show that the maximum straightness residual is less than 2 μm and the maximum angular residual is less than 2 arc-sec. The experimental results show that the system have a straightness repeatability of ± 2 μm and an angular repeatability of ± 2 arc-sec. The developed 4-DOF measurement system can be easily assembled for geometric error measurement of machine tools in the industrial fields.
Thermoelastic damping is one of the key factors affecting the quality factor of vacuum-encapsulated resonant devices. In order to suppress the influence of thermoelastic damping, vertical slots are introduced to the MEMS resonant beams. The heat flux inside the beams are expected to be reduced through local structural optimization, thus improving the quality factor. To verify the feasibility of the proposed method, the software of COMSOL is employed to explore the inhibition effect of structural parameters such as length, width and quantity of the slots on thermoelastic damping. The simulation results show that the thermoelastic damping decreases sharply and the quality factor are improved after the slots are introduced, and the effects are strongly related to the characteristic parameters of the slots.
This paper mainly focuses on the sphericity evaluation based on the minimum zone sphere (MZS) method in the Cartesian coordinate system. An asymptotic search method is proposed to search for the homocentric centre of MZS model and calculate the sphericity error. The search process of the proposed method consists two parts: geometric area search is implemented to obtain a quasi-MZS centre (close to the MZS centre) and 3+2 and 2+3 mathematical models dominating the minimum zone sphere are solved to obtain the MZS centre. The geometric area search is employed to fast convergence to the quasi-MZS centre by constructing a search sphere model. Some characteristic points distributed on the search sphere are selected to determine the search direction. A threshold is set to terminate the search process and the quasi-MZS centre is determined as a result. The quasi-MZS centre is employed as a reference centre to solve the 3+2 and 2+3 models to determine the MZS centre. According to the minimum conditions, the mathematical models are established to solve the two models. Then the judgment is implemented to ensure all the measured points are enveloped between the two homocentric spheres. As a result, the centre of two homocentric spheres is the MZS centre. The MZS sphericity error can be obtained as well. To verify the performance of the proposed method, simulation experiments and comparison experiments are implemented. The results demonstrated that the proposed method is effective, reliable and meet the requirement of sphericity evaluation.
Probe tip of the Micro-coordinate Measuring Machine (Micro-CMM) is a microsphere with diameter of several hundred microns, and its sphericity is generally controlled at tens to hundreds of nanometers. Due to the small size and high precision requirement, the measurement of the microsphere morphology is difficult. In this paper, a measurement method for probe microsphere of Micro-CMM is proposed based on two SPM (Scanning Probe Microscope) probes, and a ruby microsphere of a Renishaw commercial CMM stylus is measured by the proposed method. In the experiment, the repeatability error of a maximum section profile is test, and the repeatability error is 41 nm (peak-to-peak value). Two perpendicular maximum section profiles are measured, and the corresponding diameter and roundness are estimated by the least squares method.
The zero initial optical path difference, the integral optical path layout and the polarization interference technique are adopted to design quadruplicated polarized laser interferometer measuring system. The factors and design requirements which affect high-precision interferometer are analyzed. In order to reduce DC offset error, unequal amplitude error and non-orthogonal error, four orthogonal measuring signals are processed by a series of circuits with differential amplification and orthogonalization functions, and the two ideal orthogonal measuring signals are obtained. Beyond the VC++ environment, combined with the 200 phase subdivision, the resolution of 0.8 nm can be achieved. The measuring results are compensated and corrected according to the environmental parameters. The error sources of the measuring system are analyzed, and the quantitative values of the cosine error and abbe error are given. Compared with the British Renishaw XL-80 high-precision laser interferometer, the experimental results show that the measuring system has high stability and accuracy.
In order to compensate three-dimensional (3D) angle errors of two-dimensional (2D) stage in motion, a 3D angle errors detection and compensation system using a modified DVD pick-up head has been developed in this paper. The modified DVD pick-up head, which consists of a commercial DVD pick-up head without objective lens and voice coil motor, is used as an angle sensor. The mechanism of the angle sensor is based on optical auto-collimation, and each sensor can detect two deflection angles of the stage simultaneously. Utilizing the angle error information obtained by two angle sensors which are set along X and Y moving direction respectively, the controlling system adjusts the nano-positioning stage by controlling the piezoelectric ceramic actuators’ movement to compensate the angle errors of the stage. This system can achieve the measurement and compensation of yaw angle error, pitch angle error and roll angle error of the stage. Experimental results show that the angle detection range of this system is ±110", the resolution is about 0.2", and the repeatability error is about 2″. After compensating, the 3D angle errors of 2D stage can be controlled within 3″. This system has the advantages of compact structure, low cost, etc.