Jüri Olt

• PhD
• Estonian University of Life Sciences

In precision agriculture (PA), monitoring individual plant health is crucial for optimizing yields and minimizing resources. The normalized difference vegetation index (NDVI), a widely used health indicator, typically relies on expensive multispectral cameras. This study introduces a method for predicting the NDVI of blueberry plants using RGB imag...

Machine learning algorithms are increasingly used to enhance agricultural productivity cost-effectively. A critical task in precision agriculture is locating a plant's root collar. This is required for the site-specific fertilization of the plants. Though state-of-the-art machine learning models achieve stellar performance in object detection, they...

The integration of artificial intelligence and data science in agriculture is significantly transforming traditional human knowledge-based agricultural practices into a data-driven decision-making domain, known as precision agriculture. This study focuses on enhancing precision farming by using computer vision models to detect root collar of bluebe...

Electrically driven agricultural robots encounter accelerated battery depletion compared to vehicles operating on asphalt due to heightened rolling and traction resistance necessitating increased energy consumption. This issue becomes pronounced in regions devoid of access to the electrical grid, precluding the possibility of recharging electricall...

Over the past two decades, there has been an increasing use of biofuels worldwide, especially in Europe. The main objective is to reduce greenhouse gas emissions, particularly carbon dioxide (CO 2 ), from transportation. The regulation of fuels produced from biomass and other renewable sources at the EU level is primarily governed by the Renewable...

Electrically driven agricultural robots experience faster battery depletion than vehicles moving on asphalt because higher rolling and traction resistance require more energy. The problem arises in areas without access to the electrical grid, where charging electrically driven agricultural robots is not possible, resulting in interruptions to the r...

This article focuses on optimizing the battery management algorithm to minimize the amount of energy remaining in the battery at the end of the workload.The increasing use of renewable energy to operate agricultural robots increases the autonomy of the robot's energy supply. The volatility of renewable energy in turn increases the need for a smart...

Over the past two decades, there has been an increasing use of biofuels worldwide, especially in Europe. The main objective is to reduce greenhouse gas emissions, particularly carbon dioxide (CO2), from transportation. The regulation of fuels produced from biomass and other renewable sources at the EU level is primarily governed by the Renewable En...

One of the technologies for harvesting carrots is to separate the tops without extracting the carrots from the soil with their subsequent digging up from the soil. Since the cutting of tops is carried out, as a rule, by a continuous rotary top-cutting apparatus, there is a need to further clean the root crop heads from the top residues. A new desig...

Global transport today is mainly powered by the Internal Combustion Engine (ICE) and throughout its century and a half of development it has become considerably more efficient and cleaner. Future prospects of the ICE rely on the scientific work conducted today to keep this trend of higher efficiency and cleaner emissions in new engines going. The a...

The article poses and solves the problem on time-optimal control of the quasi-static acceleration or deceleration of a massive flywheel by taking into account the strength properties of the material. The dependence of optimal regimes on parameters is investigated and features of optimal regimes are revealed. For disk and long cylindrical flywheels,...

With depleting resources, it is essential to increase the application of Agriculture 4.0 principles and technologies. Blueberry cultivation includes various operations, one of them being fertilization. To precisely discharge the correct amount of fertilizer, a volumetric dispenser utilizing a straight fluted roller could be considered as an option....

Nowadays, there is a global trend towards the use of alternative fuels in order to reduce environmental pollution. For example, Compressed Natural Gas (CNG) has become more widely used around the world. The use of different fuels in engines affects the combustion process and efficiency, with the latter potentially being reduced by such means as, fo...

In order to carry out experimental research and determine the performance criteria for the transportation of agricultural materials, a test unit of the combined screw conveyor has been designed by the authors. The axial speed and capacity of bulk material transportation on a curved route have been determined for the articulated-section operating de...

Harvesting sugar and fodder beet tops is a complex technological process that requires the use of special harvesting machines. Trailed harvesters of different rows, which together with aggregate tractors form symmetric or asymmetric machine-tractor units, the movement of which in the horizontal plane is not always stable, are widely used. The purpo...

One of the important processes taking place during soil surface tillage is the variation of the soil temperature at different depths. The paper presents the results of research into the dynamics of soil temperature variation in terms of such parameters of the soil as its thermal diffusivity and temperature oscillation frequency. It has been establi...

In this article, power characteristics of a state-of-the-art unmanned ground vehicle (UGV) are characterised. It is demonstrated that in terms of power characteristics requirements, purpose-built computer aided autonomous UGV systems are capable of replacing systems that utilise conventional tractors in peat field operations, with milled peat extra...

Nowadays, structures welded from dissimilar steels have found a wide application in mechanical engineering. One workpiece that belongs to this class is a shut-off solenoid valve. As evidenced in practice, a single-pass boring cycle of a dissimilar welded structure with a 0.5-m tool overhang is accompanied by an autowave process (AWP), which evolves...

This research resulted from military interest in finding methods to provide distributed electricity generation in order to support comprehensive state defence measures. The aim of the study was to investigate the effect of a heated air-fuel mixture on the combustion process of a spark ignition (SI) engine, and to highlight the maximum temperatures...

This research resulted from military interest in finding methods to provide distributed electricity generation in order to support comprehensive state defence measures. The aim of the study was to investigate the effect of a heated air-fuel mixture on the combustion process of a spark ignition (SI) engine, and to highlight the maximum temperatures...

One of the possible ways to significantly increase the spreading distance of fertilisers (and, accordingly, efficiency) by the fertiliser spreading tools may be creation of a structure with an inclined axis of rotation. For experimental investigations an experimental setup was developed and a solid mineral superphosphate granular fertiliser was use...

For precise fertilization of blueberry plants, it is technologically the easiest and most suitable option to use a volumetric filling, for which it can be presumed that it is possible to precisely dose the fertilizer for each plant by grams. For setting up a volumetric filler, it is necessary to know parameters such as the size of the fertilizer pa...

In this article a concept is presented for replacing the tractors that haul machinery during necessary operations on peat fields with centrally controlled unmanned ground vehicles (UGVs). The objective is to reduce operational costs in terms of human labour, fuel consumption and the associated CO2 emissions. A robotic system architecture for the ex...

The article deals with the most effective primary utilization and subsequent processing of the main waste of machine-building enterprises-metal chips. To solve the above problems, the recycling of metal waste the most effective method is a comprehensive approach to the conditions of machine-building enterprises working in the conditions of the auto...

Annotation Purpose. Establishment of theoretical regularities that make it possible to make such a choice of parameter values for a trailed disc harrow, which provides it with the desired directional stability, which, in turn, ensures a high-quality performance of the technological process for the disc-type machine-tractor unit. Methods. The method...

From the point of view of environmental protection, it is reasonable to stop using disposable tableware that has been made from polluting plastics and to start using biodegradable and compostable products. Biodegradable and compostable tableware is significantly more environment and nature friendly than disposable plastic tableware and drinkware. T...

In the production of biological preparations for agriculture there are promising jet bioreactors with an external circulation ring, providing intense mixing of the medium along with a high degree of aeration. However, application of these bioreactors is limited by large shear loads on the microorganisms (microorganism cells) arising in the circulat...

The production of exhaust gas emissions in combustion engines has been the subject of many studies all over the world, including exhaust gas emissions produced in the combustion of biofuels. The studies have mainly focused on the production of exhaust gas emissions from using various fuel mixtures in various types of engines. The effect of biofuels...

In the process of cutting, often the selection of cutting parameters is done considering empirical methods. This approach is more expensive and does not usually lead to the best solutions. Numerical methods for simulating the chip formation have been under development over the last thirty years. The aim of the present research is to compare models...

This study discusses practical collection methods of cereal harvesting costs in different agricultural holdings in order to effectively manage combine harvester fleets, make economically reasoned decisions on the exploitation of combine harvesters, reduce harvesting costs and consequently the cost price of cereals. For this purpose, the author used...

Biodegradable and compostable tableware which is made by using agricultural by-products is significantly more environmentally-friendly than is disposable plastic tableware. The aim of this research was to study and compare production technologies that are used in the formation of tableware using by-products from the process of milling cereals, spec...

The occurrence of fretting corrosion on nominally fixed surfaces of high-loaded parts of mining machines and mechanisms is considered. Examples of wear and damage of critical parts, bearing assemblies of engines of dump trucks in fretting conditions are given. The mechanisms of fretting corrosion when using wear-resistant coatings are considered. I...

In addition to gasoline and diesel fuel, the biofuels HVO and FAME have been taken into wide use during the last decades. The properties of gasoline and diesel fuel and their effect on the combustion process have been studied for a long time, but studies on HVO and FAME are still are very much work-in-progress. Existing studies show that the use of...

In order to model and optimise the structural parameters of the working parts of agricultural machines, including harvesting machines, the mechanical properties of the culture harvested must be known. The purpose of this article is to determine the mechanical properties of the blueberry plant’s stem; more precisely the tensile strength and conseque...

The increase of the efficiency and quality of performance of the work process of potato heap separation can be achieved by means of improving the design of the vibrational spiral separator and substantiating theoretically its rational parameters under the condition of eliminating damage to the potato tubers. An equivalent schematic model of the int...

In order to increase substantially the quality of the potato heap separation, it is necessary to carry out the theoretical substantiation of the spiral separator’s parameters with regard to the impact interaction between the product and the tools of the unit under the condition of not damaging the tubers. An equivalent schematic model of the impact...

Metal cutting is a complex process in which several mechanisms are at work simultaneously. The mathematical modelling allows carrying out research into the optimization of machining conditions. This work examines the simulation of chip formation during the process of cutting. The studies demonstrated that the chip formation process, taking into acc...

The theoretical basis of the agricultural material drying techniques has been formed in the world for two and a half centuries. Nevertheless, despite the multitude of studies well presented in the literature, the industry still lacks universally recognized methods of design calculation for the majority of drying problems. Presumably, this is due to...

Cleaning potato tubers from soil impurities and plant debris after digging them out of soil is a topical problem in the work process of potato production. Therefore, the engineering of new designs of potato heap separators necessitates the further studying of them and the optimisation of their kinematic and design parameters, which must not only en...

Replacing traditional fuels with biofuels in the transport sector has been named as one of the measures in the increasingly strict environmental policy of the European Union. The Renewable Energy Sources directive and Fuel Quality Directive stipulate the minimum required amount of biofuel to be added to the motor fuel used in the transport sector....

Growing blueberries on exhausted milled peat fields could be a possible solution to decrease carbon dioxide emission from these areas. To operate such crop-giving plantation manually, a lot of manpower is needed. To decrease the manpower, suitable and helpful technical solutions should be introduced. The aim of this article is to investigate differ...

Oil shale is the main energy resource in Estonia, which generates large amounts of CO2 and waste oil shale ash. Flue gas from oil shale combustion can also contain large amounts of SO2. Microalgae can be used for biological sequestration of carbon from flue gas. In this research, green algae Scenedesmus obliquus were grown with 14% CO2 in 1 L biore...

Free-piston engines (FPE), as power generators for electricity and hydropower solutions, have come under intensive research and development during the last decade. The rapid development of information technology provides an opportunity to return to FPE technology development due to better levels of control and management in terms of the engine’s wo...

The smoothly adjustable belt drums of belt sorters can be used in the processing of harvested blueberries. Previous tests with the smoothly-adjustable belt drums of belt sorters indicates the fact that further improvements are required to increase their sorting efficiency and uniformity. For this, the relationship between the dimensional characteri...

The article considers the issues related to improving the efficiency of multipoint machining by the use of rotary cutters which are equipped with replaceable ceramic inserts on CNC machines by developing a method of multipoint machining process control. A dynamic model is proposed for the multipoint cutting process on the basis of continuum theory,...

A mathematical model has been developed representing the motion of a seed drill combination simultaneously performing the preceding banded placement of mineral fertilisers. Such a combined unit comprises the gang-up wheeled tractor, the fertiliser distribution module behind the tractor attached to it with the use of a hitch and intended for the ban...

The reduction of power consumption in the ploughing operations can be achieved by way of improving the grip properties of the implement -carrying tractors, which is facilitated by selling up ploughing units for operation on the 'push-pull' principle. The aim of the current research is to substantiate the set-up and parameters of the ploughing unit...

In light of climate change and the increasingly limited availability of energy resources, any form of renewable raw materials that can be used for energy production should be accounted for. One of the most promising renewable sources is considered to be that of lignocellulosic feedstock. In urban forestry and greening, millions of tons of lignocell...

This paper presents a novel biomass pretreatment method that uses high pressured N2 and temperature to break the hemicellulose and lignin seal around the cellulose macro fibrils in the cell walls of the lignocellulosic biomass in order to open up the biomass structure for more efficient enzymatic hydrolysis. In this method the biomass is exposed to...

A novel method for the pretreatment of lignocellulosic material is investigated in this work, using floodplain meadow hay as a feedstock for bioethanol production. Pressurized nitrogen (N2) pretreatment is combined with explosive decompression to achieve high glucose yields with simple technology and low energy input. Results show that N2 explosion...

This work examines the simulation of chip formation during the process of cutting. An analysis of complex rheological models enabled a set of assumptions to be considered, thereby substantiating a hypothesis relating to the chip formation process. The studies demonstrated that the chip formation process, taking into account the plastic deformation...

Belt sorters are used to sort different type of objects according by their size. Making belt sorter easily and quickly adjustable in desired range has positive influence on it’s functionality and productivity. One solution for that is to use one or more adjustable belt drums. This option allows to change the distance between belts evenly and throug...

The paper presents the main provisions of the new theory of oscillations of the versatile combined opener assembly of the breeding seed drill with a spring-suspended furrow opening toothed disc in the vertical longitudinal plane during its movement across irregularities of the soil surface. Basing on the improved design of the opener assembly, an e...

The application of coatings based on fluorocarbon polymer composition, frictionmechanical brass, fullerene C60 and surface treatment of vibrorolling with the regular roughness for the protection of heavily loaded mating parts of machines, working in conditions of frettingcorrosion. Studied the mechanisms of friction of coating, which will considera...

The article examines the forecasting performance of the cutting tool equipped with interchangeable plates of carbide oxide ceramics (A2 – mixed ceramic), by definition porous ceramic tool material affecting its cutting properties. Set correlation of porosity ceramic tools from electrical resistivity removable ceramic plates. Cutting tools having la...

Currently, throughout the world quite extensive use is made of combined tractor-implement units, which are capable of performing several process operations in the same pass. At the same time, the state-of-the-art ploughing and general-purpose tractors that can carry as front- so rear-mounted implements and accordingly feature both the front and rea...

The mathematical modelling of the process system allows carrying out research into the selection and optimisation of machining conditions. The conceptualization of the operator that represents the dynamic characteristics of the cutting and friction process is an important issue in the development of the mathematical formulation of the interaction b...

The problem of collecting and utilising the pruned canes of grape vines and branches and twigs from fruit trees that are left in vineyards and orchards all year round after the scheduled pruning of plantations in early spring is the topic of the day, and it is one that requires an effective solution. One of the ways in which the problem might be so...

The widespread use of a great number of different types and manufacturer brands of tractors in agricultural use raises several important questions. These all concern the implementation of the criteria which may be involved in making the right choice in regard to a particular power unit that is capable of delivering the required result during the su...