A light and fast two-axial fine-pointing mirror has a number of space applications, especially in intersatellite optical links. The fine pointing of laser beams in optical links is currently realized with electromagnetic or piezoelectric actuators, which are relatively large and heavy. Micro-electro-mechanical system technology bears a high potential in space applications, offering a reduction in device size, mass and power consumption. Microtechnology facilitates batch mode fabrication, yielding a low cost per unit. VTT Automation has designed and partially tested a silicon micromachined electrostatically actuated two-axial mirror, which can be controlled with microradian resolution and large bandwidth over the angular range of ±3 mrad.
A non-contacting online caliper measurement has been papermakers' dream for over two decades. Currently, paper thickness is measured using buttons contacting the paper web on both sides. In such a configuration, paper thickness is assumed to be the distance between the contacting surfaces and determined by a magnetic measurement principle. However, this arrangement of contacting measurement has several disadvantages including sheet marking, hole creation, dirt build-up on the contacting buttons, wearing of the contacting surfaces, and even sheet breaks. Moreover, the current trends in paper manufacturing, especially the increasing use of recycled raw materials are necessitating the development of a more reliable thickness measurement solution that is not affected by dirt and other material on paper or board sheet surfaces.So far, a non-destructive, on-line thickness measurement has not been successfully applied in paper production environment. Recently, Metso Automation has successfully piloted in several mills a caliper sensor that does not contact the sheet on both sides and is able to measure paper thickness with sub-micron accuracy. The new sensor is based on single sided laser triangulation. This paper presents the measurement set-up and discusses the challenges encountered. Measurement results obtained in mill trials with various paper grades are reviewed and compared to those made simultaneously with contacting, on-line sensors and off-line laboratory results of the same sheet. Factors affecting the measurement with conventional and optical thickness sensors are also discussed.
Continuous and robust measurements are needed for the high end-product quality and efficient and eco-friendly process in paperboard manufacturing. As the online measurements enable the optimization of the manufacturing process making it more cost effective and environmentally friendly, these measurements must be validated carefully and continuously. This paper presents the development of a mass-balance based soft sensor for online estimation of a two-ply paperboard ash content. The developed soft sensor considers the basis weight, moisture and fiber measurements to derive the ash content of the paperboard at the reel. The development of the soft sensor was success (Mean Absolute Percentage Error was 11.80) and during the long-term simulation with measured data, this robust online estimator showed the level and changes in ash content accurately, enabling also the continuous validation of the hardware sensor.
Optical measurement of the density of ozone and other atmospheric species at night is possible by using stars as light sources. The Technical Research Centre of Finland (VTT) has built a star-pointing spectrometer, which records stellar spectra by a two-dimensional CCD-array. The specirometer has a "slitless" design, so it can measure the absolute intensity level of a stellar spectrum attenuated by the atmosphere. A spectral inversion method designed for the satellite-based instrument GOMOS (Global Ozone Monitoring by Occultation of Stars) is applied for constituent retrieval from stellar spectra measured on ground. Analysis of simulated measurements shows that when averaging over one night the total ozone column can be measured by the VU spectrometer at an accuracy of 2 -3 %.
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