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Implementation of inverse kinematics algorithm for 6DoF robot arm in Unity
Get PDFIn this paper, the implementation of the solution of the
inverse kinematics problem for the 6DoF industrial robot arm in
the Unity game engine is presented. Unity, one of the most
popular game engines, is a very powerful tool and a leading
platform for creating XR applications. Two different methods for
the implementation of the solution of the inverse kinematics
problem have been proposed: 1) Development and
implementation of the inverse kinematics algorithm of a specific
robot, and 2) Using inverse kinematics solvers by integration of
Unity with dedicated robotics development frameworks. For
verification of the proposed procedures, a serial robot with
cylindrical joints RL15 is used
Effect of Corrosion-Induced Structural Degradation on the Ultimate Strength of a High-Tensile-Steel Ship Hull
Get PDFStandard structural assessments of ship hulls include the evaluation of the elastic structural response. Elastic analysis neglects extreme and unpredicted loadings, which can produce catastrophic outcomes, such as the loss of the ship’s ultimate strength. Moreover, hull elements are considered unaffected by age-related degradation. Therefore, this study models and quantifies the effect of corrosion-induced structural degradation on the ultimate strength of a high-tensile-steel (HTS) cargo ship using progressive collapse and nonlinear finite element methods. Uniform and pitting corrosion are modeled through selected scenarios, which hull elements might encounter during exploitation, producing a total of 148 calculation models. The findings show that corrosion-induced degradation can significantly decrease the ultimate strength of the hull (up to 30% for the most severe scenarios assessed). Furthermore, ultimate strength decreases almost proportionally to the amount of wastage considered. It was found that stiffener corrosion has a significant effect on the total ultimate strength. This study’s aim is to emphasize the vast importance of including ultimate strength along with ageing effects in industry-standard structural assessments of large HTS ship structures, designed to last for several decades whilst exposed to excessive and unpredicted bending moments
HARD HAT DETECTION FOR SAFETY PURPOSES BY USING YOLOV9
No full textEnsuring the safety of workers at workplaces is a crucial task for every company. The usage of personal protective equipment represents the basic form of protection. Hard hats are very useful in protecting head from injuries. However, workers often neglect the importance of wearing safety helmets and do not wear them. Systems for monitoring and detecting unsafe behaviors can be very helpful for maintaining security. For that purpose, this research examines the success of the application of the latest YOLO algorithm for detecting the presence of safety helmets on workers that can be applied in those systems. Two models with different numbers of parameters are trained for this purpose – YOLOv9c and YOLOv9e. The results showed that YOLOv9c model achieved mean average precision of 97.2%, 93%, and 92.9% in training, validation, and testing, respectively, while YOLOv9e reached slightly higher mean average precisions of 97.5% in training, 93.4% in validation and 93.4% in testing
Pressure Distribution in Gas Microbearing Modeled with Fractional Derivatives for all Rarefaction Degrees
No full textVelocity slip boundary condition for all Knudsen number values in microbearing gas flow is modeled by fractional derivative. For this purpose, a variant of Caputo derivative with the variable order α which depends on the local value of Knudsen number is applied. Such a universal boundary condition is implemented in the solving procedures of continuity and momentum equations, which leads to the general corrected Reynolds lubrication equation for all rarefaction degrees. An appropriate transformation of the variables enabled obtaining an analytical solution for mass flow rate and pressure distribution in the microbearing. The presented solution is in an excellent agreement with the solutions based on the kinetic theory for all regimes: continuum, slip, transition, and free molecular flow
MECHANICAL PROPERTIES OF PA12 SPECIMENS PRODUCED USING SLS TECHNOLOGY
No full textIn this study, the research focuses on tensile PA12 specimens with CAD model dimensions selected according to the ISO 527-2 standard, with bulk dimensions of 170x20x4 mm. The study utilizes a Fuse 1 (FormLabs, Summerville, MA) 3D printer that employs SLS technology. This printer is capable of producing objects with different shapes and dimensions simultaneously, provided that they are printed at a minimum distance of 5 mm apart.
The research involves producing two batches of specimens, each differing in printing orientation (i.e., horizontal and vertical). After printing, the specimens are tested using a Shimadzu AGS-X universal testing machine with a capacity of 100 kN to evaluate the mechanical characteristics of the materials. The findings reveal that horizontally printed specimens have a modulus of elasticity about 9.3% higher than the manufacturer's stated value, while vertically printed specimens show an increase of approximately 11.4%. This enhancement is likely due to the thermal and cooling cycles during printing. The difference in modulus of elasticity between the orientations is around 2%, indicating a minor impact on mechanical properties
Environmental and Social Assessment of SHPP Mojanska 1 - Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)
Excavators’ Cabins Ergonomic Design Influential Factors Modelling: Preliminary Study
No full textExcavator operators encounter demanding work environments with very high risks for discomfort, musculoskeletal disorders, and workplace accidents. In line with that, this study examines the relationship between ergonomic design influential factors using the structural model of excavator cabins design factors, using a sample of 32 excavator operators. Descriptive statistics were performed to describe the operator's age, height, weight, working experience, and excavator's lifespan. After that, the structural equations model was developed to describe the impact of latent variables related to ergonomic design of the cabin. This model was constructed by using 17 questions, which were categorized into 5 groups based on ergonomic design characteristics such as seat, armrests, commands, cabin, and working conditions. The findings indicate that the model exhibits favourable reliability and validity coefficients, a substantial effect size, and a satisfactory model fit. Further research is needed to increase the sample size, despite the preliminary nature of the current research and its satisfactory results
Carnot Battery with Steam Accumulator and Pebble Bed Thermal Energy Storage
No full textCarnot battery with steam accumulator and pebble bed thermal energy storag
A comprehensive bibliometric analysis and assessment of high-impact research on the berth allocation problem
No full textThis paper aims at the identification and assessment of High-Impact Research Papers (HIRPs) on the Berth Allocation Problem (BAP) research at marine terminals. The BAP objective is to optimally assign and schedule ships at berthing positions along a quay, as well as to determine the berthing times and positions of ships at a port. The purpose of this study is to facilitate the work of the relevant research community and ultimately promote the research quality in this area. In meeting this objective, the paper utilizes a systematic and fair method to determine HIRPs of the BAP, which is based on the h-index and the g-index. An in-depth bibliometric analysis of the identified studies reveals their key features and characteristics. The analysis was conducted using the VOSviewer and bibliometrix R-package software programs. The main findings provide many useful insights on the BAP research development. The adopted approach and associated analysis results present an up-to-date detailed picture of the BAP research and constitute a valuable tool for its applications into other relevant research areas. The common trends in the reviewed HIRPs and important future research needs are discussed in a comprehensive manner. This survey study can be viewed as the first attempt for a comprehensive bibliometric survey of the high-impact BAP literature, which will be of a great value to researchers and industry practitioners. Furthermore, the proposed methodology for the identification of HIRPs can be used not only for the BAP research but for the literature surveys in other domains as well
Risk Assessment of Pressure Vessels by Using Fracture Mechanics and Advanced Ultrasonic Testing
No full textRisk assessment of cracked cylindrical pressure vessels for compressed air by using basic fracture mechanics and advanced methods of non-destructive testing (NDT), such as Phased Array Ultrasound (PAUT) and Time-of-Flight Diffraction (TOFD), is presented. Basic fracture mechanics equations are used to calculate the stress intensity factor, KI, in the case of unacceptable defects found in the pressure vessel 970 in the Reversible Hydro Power Plant "Bajina Basta", and get the ratio KI/KIc, according to the minimum measured values for fracture toughness for welded joints, as the typical zones where crack-like defects are found. The ratio Snet/Sc, where Snet is the net stress in cross-section with a crack, and Sc is the critical stress, is then evaluated to define the operating point in the Failure Assessment Diagramme (FAD), and thus, to estimate the likelihood of failure of the pressure vessel 970. In combination with estimated high consequence for the pressure vessel 970, the risk matrix was used, as a simple tool to assess the risk. In this paper the focus is on one aspect of this procedure, being the NDT role, since it is of utmost importance to use as precise as possible method for detected defects in welded joints. In this paper advanced ultrasound methods, PAUT and TOFD, are used to get precise image of defects in pressure vessel 970 welded joints, which were previously detected by conventional NDT methods. It is shown that the use of PAUT and TOFD is of utmost importance for decision making process in this case. © 2024, Strojarski Facultet. All rights reserved