Measurement of ground borne vibrations for foundation design and vibration isolation of a high-precision instrument

Design and performance of an advanced metrology building for MIKES

Active vibration isolation systems (AVIS) reduce the vibrations transmitted to ultraprecision mechanical systems by providing managed stiffness and damping. Many types of AVIS are used in various fields. In nanoprecision measuring instrument fields, such as atomic force microscopy and scanning probe microscopy, the requirement for isolation of ground vibrations has always been of great interest to researchers. Bench-top-type six-degree-of-freedom (6-DOF) AVIS have been widely used in ultraprecision measuring applications. This paper describes the design, modeling, optimization, and validation of a new 6-DOF AVIS. The unique feature of the proposed system is its voice coil motor actuator that uses a Halbach magnet array to produce a high force constant. The results obtained using the proposed AVIS show that it can serve as a bench-top device for precision measuring machines.

Design and Control of a 6-DOF Active Vibration Isolation System Using a Halbach Magnet Array

Measurement underpins manufacturing technology, or in more popular terms: when you cannot measure it, you cannot manufacture it. This is true on any dimensional scale, so for microand nanotechnology to deliver manufactured products it must be supported by reliable metrology. Component miniaturization in the field of precision engineering and the development of micro electromechanical systems (MEMS) thus results in a demand for suitable measurement instruments for complex three-dimensional components with feature dimensions in the micrometer region and associated dimensional tolerances below 100 nm. As will be discussed in the first chapter of this thesis, several ultra precision coordinate measuring machines (CMMs) are developed. These CMMs are suitable for measuring complex threedimensional products, like MEMS and other miniaturized components. From a discussion on available probe systems in the first chapter it is apparent that, with respect to measurement uncertainty and applicability of measurements on MEMS and other miniaturized components, the performance of ultra precision CMMs is currently limited by the performance of available probe systems. The main reason is that the measurement using a probe system is not purely influenced by work piece topography, but also by interaction physics between probe tip and work piece. As the dimensional scale of the measurement decreases, the problems associated with this interaction become increasingly apparent. Typical aspects of this interaction include the influence of contact forces on plastic deformations in the contact region, surface forces and geometric and thermal effects. The influence of these aspects on the measurement result is discussed in the second chapter. This chapter will combine results from literature, simulation and experimental results to discuss the aspects that influence the measurement result in tactile probes. From these results it will become apparent that these aspects underlie the limitation for precision measurements on miniaturized components using tactile CMM metrology. As a result, these interaction aspects are the main challenge when designing ultra precision probes. The analysis of the interaction physics is used in the design of a novel silicon probing system with integrated piezo resistive strain gauges to measure a displacement of the probe tip. The result is a probe system with a colliding mass of 34 mg and an isotropic stiffness at the probe tip with a stiffness down to 50 N/m. The measurement range of the probing system is 30 µm, but in most measurements a range of 10 µm is used which slightly improves the signal to noise ratio. Calibration results using the planar differential laser interferometer setup as discussed in chapter 1 show a standard deviation of 2 nm over 2000 measurement points taken in a 6 hour time frame over a repeated 5.5 µm displacement. The combined 3D uncertainty of the probing system is estimated to be 17.4 nm. In order to measure micrometer scale structures, including holes and trenches, the probing system can be equipped with micrometer scale probe tips. The main limitation is the relative stiffness between the stylus and the suspension of the probing system. By design optimization, a ratio between the length and radius of the measurement part of the stylus of 50 can be obtained, making the probing system highly suitable for measuring these micrometer scale structures. So far, probe tips with a radius of 25 µm have been manufactured and work is being done to decrease this radius even further. The probing system is implemented on a high-accuracy coordinate measuring machine and is suitable for three-dimensional tactile measurements on miniaturized components with nanometer uncertainty. A main limitation when manufacturing the probe is assembly of the probe tip, stylus and chip which is discussed in chapter 4. Assembly of the probe is investigated in a series of experiments on an automated assembler. Based on these results, the design of the probe is optimized for assembly and the automated assembler is made suitable for assembly of the probe by implementation of a novel suction gripper. This resulted in an improvement in placement uncertainty at the tip by a factor of 10 and an increase in yield during assembly from 60 - 80% initially, to over 95%. In chapter 5 several experimental results with the probe system are discussed, including a quantification of the effects of surface forces on tactile measurements. It is shown that these effects are highly repeatable and result in an attraction of 40 µN and 60 µN in the xy- and z-direction, respectively. Moreover, it is shown that the influence of surface forces on a measurement in the xy-plane can be observed for a separation of 500 µm or less. Finally, conclusions and recommendations for further research are discussed in chapter 6.

Tactile 3D probing system for measuring MEMS with nanometer uncertainty : aspects of probing, design, manufacturing and assembly

Most standard temporal-phase-shifting (TPS) algorithms evaluate the phase by computing a windowed Fourier transform (WFT) of the intensity signal at the carrier frequency of the system. However, displacement of the specimen during image acquisition may cause the peak of the transform to shift away from the carrier frequency, leading to phase errors and even unwrapping failure. We present a novel TPS method that searches for the peak of the WFT and evaluates the phase at that frequency instead of at the carrier frequency. The performance of this method is compared with that of standard algorithms by using numerical simulations. Experimental results from high-speed speckle interferometry studies of carbon fiber panels are also presented.

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Adaptive phase-shifting algorithm for temporal phase evaluation

Establishment of appropriate vibration criteria is essential when designing vibration-sensitive metrology laboratories. Boundary values that are too severe may lead to unnecessarily high construction costs, whereas limits that are too broad may result in degradation of the performance of measurement equipment. The Norwegian Metrology and Accreditation Service (Justervesenet) inaugurated a new facility early in 1997. The facility will allow measurements of mass, density, dimensional, force, volume, optical, pressure, temperature and electrical quantities. Vibration control is of concern in most of the laboratories. Vibration criteria have been defined in terms of frequency-dependent peak values. In this paper, these criteria are described and the most conservative criterion is compared with other known vibration criteria for standard laboratories and high-technology facilities. The vibration criteria considered have different formulations and cannot be compared directly. They are therefore compared with regard to three different kinds of idealized vibration excitation, that is, transient, harmonic-motion and broad-band noise. The comparison shows that the most conservative Justervesenet vibration criterion is stricter with respect to high-frequency vibrations than are the others, but it is less strict for low-frequency vibrations.

https://iopscience.iop.org/article/10.1088/0957-0233/10/11/306/pdf

Henning Kolbjørnsen

Papers

Vibration criteria for metrology laboratories