Sigitas Petkevičius

Vytautas Magnus University, Kaunas (VDU) · Agricultural engineering

This paper is dedicated to soft grippers, robot tools with a wide application area in various activities where an accurate and delicate grabbing movement is required such as routine manipulation tasks with fragile objects, operation in unknown or dangerous environments, and manipulation with unknown shape objects, as well as exploring the depths of...

Autonomous systems are becoming increasingly relevant in our everyday life. The transportation field is no exception and the smart cities concept raises new tasks and challenges for the development of autonomous systems development which has been progressively researched in literature. One of the main challenges is communication between different t...

Positioning accuracy in robotics is a key issue for the manufacturing process. One of the possible ways to achieve high accuracy is the implementation of machine learning (ML), which allows robots to learn from their own practical experience and find the best way to perform the prescribed operation. Usually, accuracy improvement methods cover the g...

This study investigates an imaging system based on a Rikola hyperspectral (HSI) and Nikon D800E (CIR) cameras installed on a manned ultralight aircraft Bekas Ch-32 for applications involving precision agriculture. The efficiency of this technical solution is compared with that of using Canon PowerShot SX260HS camera images acquired from helicopter-...

Increasing the imaging rate of atomic force microscopy (AFM) without impairing of the imaging quality is a challenging task, since the increase in the scanning speed leads to a number of artifacts related to the limited mechanical bandwidth of the AFM components. One of these artifacts is the loss of contact between the probe tip and the sample. We...

Increasing of the imaging rate of conventional atomic force microscopy (AFM) is almost impossible without impairing of the imaging quality, since the probe tip tends to lose contact with the sample. We propose to apply the additional nonlinear force on the upper surface of a cantilever, which will help to keep the tip and surface in contact. In pra...

In a threshing device, identifying the optimum balance between grain damage and grain loss during threshing is highly relevant while harvesting high-moisture corn ears. The qualitative performance indicators of a threshing device depend on the corn ear properties and process parameters as well as the device's design. Comparative experimental trials...

In Lithuania, besides the usual farming technologies, starting precision agriculture (PA). The basic principle of the PA is to focus technological operations on the conditions located in separate field locations. When there in separate fields is a significant difference in the amount of nutrients in the soil, the distribution of weeds or diseases,...

Positioning problems of scanning electrochemical microscopy (SECM) are very important by means of living cells damaging by moving ultramicroelectrode (UME). The working principle and operating modes of SECM are introduced. Investigation of redox activity of living cells are outlined. Problems, which arise in investigations of living cells by consta...

One of the key design parameters of a threshing unit critical for corn ear threshing is the shape, height and number of the concave crossbars. The paper presents the results obtained during the theoretical and experimental research of corn ears threshing process by analysing the crossbars of three different shapes: rectangular, rounded and oblique....

The majority of district heating systems in the Baltic countries use fossil fuels; mainly coal, oil and gas. Prices of fossil fuels are constantly increasing and the earth's supply of them is running out, therefore there has been a rising demand for research on various new and alternative energy sources that could replace coal or petroleum products...

Straw walker is a separator that separates grain from straw, and limits the efficiency of combine-harvesters therefore special attention is devoted to the development and improvement of its design and technological parameters. The most important parameter of walker operation is Froude-number k that depends on the amplitude of the straw walker movem...

Crop yield has been harvested by combine harvesters where threshed grain has been separated from straw by the straw walkers or rotary straw separators. The conventional combine harvesters consist of four, five, six or eight straw walkers with stepped surface. The number of steps, their height and the inclination angle of straw walkers sections (scr...

Wet maize ears of the ‘Benicia’ variety with a moisture content of 32.5% and medium dry maize ears of ‘Attribut’ variety with a moisture content of 18.5% were fed in parallel and perpendicular to the drum shaft of a conventional threshing drum. Maize ears fed in parallel with the drum shaft in the concave clearance moved twice as fast (4–5 m s−1),...

The impact of the inclination angle of the first section (screen) of straw walkers on grain separation through the straw layer of various thicknesses has been tested in the laboratory. The straw feed rate on the straw walkers and the Froude number of the straw walkers (rotational speed of the walker crankshafts) was changed during the test. About 2...

By harvesting of wet maize (moisture content of grains about 35%) up to 40% grains can be damaged. Grain damage mostly depends on their Young's modulus. It was established, that moisture content of grains varies by length of the cobs the grain Young's modulus varies as well. It was estimated, that Young's modulus of grains changed with moisture con...

The paper presents the test results of wet maize ear threshing process during the period of 2003–2005. Grain biometrical indices, technological parameters of threshing apparatus, and the feed rate of the maize ears appeared to be the most significant causes of threshing drum losses, grain damage, and the threshed amount of grains thrown to the stra...

The paper describes the impact of the feed rate of cereals to the threshing apparatus, the movement speed of rasp bars and the clearance between the drum and the concave on the grain damage. When the feed rate of the cereals into the threshing apparatus is increased the grain damage decreases. Estimating the crop harvesting conditions the permissib...