Tag Archives: machine vision

1966-1975 V. Chaloupková, T. Ivanova and A. Muntean
Particle size distribution analysis of pine sawdust: comparison of traditional oscillating screen method and photo-optical analysis
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Particle size distribution analysis of pine sawdust: comparison of traditional oscillating screen method and photo-optical analysis

V. Chaloupková, T. Ivanova* and A. Muntean

Czech University of Life Sciences Prague, Faculty of Tropical AgriSciences, Department of Sustainable Technologies, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: ivanova@ftz.czu.cz

Abstract:

Particle size and particle size distribution (PSD) are crucial parameters which affect properties of particulate and agglomerated materials, and have an impact on a quality and utilization of a final product. The aim of this paper was to determine PSD as well as to assess dimensional features of pine sawdust fractions via mechanical sieve analysis and photo-optical analysis. The first one is a traditional and standard method taking into account only one parameter of particle shape and the second one is a modern method based on a digital image processing that considers also irregular shapes of biomass particles. Pine sawdust was grinded into three fractions: 4, 8 and 12 mm and analysed using two mentioned methods. A horizontal vibrating sieve shaker comprising 11 sieves and a bottom pan was used, and the obtained data of retained particles on each sieve were evaluated. For comparison, a computerized photo-optical particle analyser was applied with max Feret’s diameter as a measurement algorithm for a particle length, and PSD was analyzed by grouping the particles according to their distinct lengths adjusted to the sieves’ sizes used in the screening method. Moreover, additional results in dimensions and parameters of PSD were obtained and evaluated through the photo-optical method. Pine sawdust particles can be described as non-uniform, mainly prolonged, finer particles dominated in all fraction samples. The study showed differences in the results, inaccuracy and other drawbacks of the conventional sieving method such as clogging and falling-through phenomena as well as the limitations of the machine vision. Strong sides of both methods were discussed, too. Overall, the results contributed to a better knowledge of the material properties and different methods of PSD analysis.

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733–744 M. Dlouhy, J. Lev and M. Kroulik
Technical and software solutions for autonomous unmanned aerial vehicle (UAV) navigation in case of unavailable GPS signal
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Technical and software solutions for autonomous unmanned aerial vehicle (UAV) navigation in case of unavailable GPS signal

M. Dlouhy¹, J. Lev² and M. Kroulik¹*

¹Czech University of Life Sciences Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 21 Prague 6, Czech Republic
²Czech University of Life Sciences Prague, Faculty of Engineering, Department of Physics, Kamýcká 129, CZ165 21 Prague 6, Czech Republic
*Correspondence: kroulik@tf.czu.cz

Abstract:

 The article presents autonomous navigation for Unmanned Aerial Vehicles (UAV) without GPS support flying in extremely low altitudes (1.5 m – 2.5 m). Solution via visual navigation as an alternative to missing GPS position was proposed. MSER (Maximally stable extremal regions) was used as a navigation algorithm for detection of navigations objects. While GPS is useful for waypoints specification there are scenarios where GPS has unreliable signal (orchards) or is not available at all (indoor machinery halls or greenhouses). For that reason existing installed camera which is already needed for the task of inspection was used. The navigation algorithm was tested in two scenarios. The first experiment was done with dashed line marked on the floor of the hall. 8-loop testing track was created approximately 10 meters long so it was possible to fly it several times. Then outdoor experiments were performed on the university campus and park roads.
One of the discoveries was that MSER algorithm, proposed for finding correspondences between images, is possible to run in real-time. High reliability of the navigation algorithm was found during the indoor testing. The incorrect detection of the dashed line was found only in 1% of cases and those failures did not cause failure of navigation.
Although outdoor road recognition is difficult in general due to various surfaces and smoothness, MSER was able to find suitable candidates. When the UAV was fed with the parameter of road width it could verify that information with estimated distance and camera pose to accept or reject the detected pattern. The road was successfully recognized in 40% cases. Similar to the indoor algorithm in the case of navigation failure navigation along the absolute trajectory (line) was used.

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