Review of Development Stages in the Conceptual Design of an Electro Hydrostatic Actuator for Robotics

The design of modern robotic devices faces numerous requirements and limitations which are related to optimization and robustness. Consequently, these stringent requirements have caused improvements in many engineering areas and lead to development of new optimization methods which better handle new complex products designed for application in industrial robots. One of the newly developed methods used in industrial robotics is the concept of a self-contained power device, an Electro-Hydrostatic Actuator (EHA). EHA devices were designed with a central idea, to avoid the possible drawbacks which were present in other types of actuators that are currently used in robotic systems. This paper is a review of the development phases of an EHA device for robotic applications. An overview of the advantages and disadvantages related to current EHA designs are presented, and finally possible ideas for future developments are suggested

Bus Fleet Management – A Systematic Literature Review

The research on Bus Fleet Management (BFM) has undergone significant changes. It is unclear whether these changes are accepted as technological change or as a paradigm shift. Perhaps unintentionally, BFM is still perceived as routing and scheduling by some, and by others as maintenance and replacement strategy. Therefore, the authors conducted a Systematic Literature Review (SLR) to overview the existing concepts and school of thoughts about how stakeholders perceive the BFM. The SLR post-study exposed that BFM should be acknowledged as a multi-realm system rather than a uniform dimension of fulfilling timely service. Nonetheless, the work encapsulates BFM evolution which shows the need for the multi-realm research abstracted as "Bus Fleet Mobility Management" and "Bus Fleet Asset Management". The difficulties of transport agencies and their ability to switch from conventional to Zero-Emission Buses (ZEBs) illustrates why we propose such an agenda, by which the research is validated through needs both in academia and in practice

Importance of offline filtration system use

Any machine which uses mineral oil for power transfer or lubrication is dependent on the condition of the oil. Maintaining oil performance and machine components at their best is therefore vital. System filters are primarily the last line of defense, but are not conductive to achieving optimum oil cleanliness, as pressure shocks will result in the release of a large amount of the particles already retained by the filter insert. However, originally installed (suction, pressure, return) filters are still important as last chance inline filters. Secondary oil filtration is ideal for ensuring the lowest possible degree of contamination in the system, e.g. to achieve a specific level of oil cleanliness. Because of secondary filter circuit works independently of the hydraulic or any other oil lubrication system, its level of efficiency remains constant – in any situation of system operation. This paper will present reasons that justify use of an secondary filtration system

Impact of contaminated fluid on the working performances of hydraulic directional control valves

© 2019 Journal of Mechanical Engineering. The study aims to investigate the impact of solid particles on the directional hydraulic valve operation. Experiments have been performed for a certain number of operating cycles to measure the impact of the working fluid cleanliness level on the intensity of the wear on contact surfaces as well as on other failures in the operation of the directional control valve. For experimental purposes, a mechanically actuated control valve 4/2 is used. The wear intensity of working elements was determined for different levels of oil contamination by solid particles. Also, experimental results have shown that there are differences between theoretically calculated and the measured flow through the radial clearance. By measuring pressure drop values during the fluid flow through the valve, it was found that oils with the lowest cleanliness level have a greater dispersion of the measured values. The results will contribute to better understanding the impact of working fluid cleanliness on possible defects and failures happening inside hydraulic system components

Določanje izgub tlaka v hidravličnih cevovodih ob upoštevanju vpliva temperature in tlaka

Generally accepted methods for calculating pressure losses within flat pipelines, as presented in literature and used in praxis, are based on the Reynolds number, which considers the viscosity and density of fluid, internal pipe friction coefficient, pipe geometry, and oil circulation velocity. Such an approach contains serious inconsequentiality. Namely, only nominal values for viscosity and density are considered in the calculation, which differs substantially from real conditions. It often leads to inaccurate calculations of pressure losses. A numerical model has been developed within the work prescribed in the paper, which takes into account actual changes in density and viscosity under the current oil pressure and temperature in order to overcome the above weaknesses of standard calculation procedures. Such an approach is novel and provides new capacity for an accurate pressure drop analysis of advanced hydraulic systems

CONTAMINATION CONTROL OF HYDRAULIC SYSTEMS IN INDUSTRY 4.0

This paper describes the expansion of maintenance in Industry 4.0 concerning contamination control ofa hydraulic systems. Recently, a lot of attention is dedicated towards newly coined term of Industry 4.0, therefore maintenance 4.0, Industrial Internet of Things, Internet of Condition Monitoring, etc. Contamination control as an integral part of Condition Based Maintenance takes a significant part in diagnostics and prognostics of systems containing hydraulic fluids. Hydraulic fluid as a driving medium in hydraulic system suffers from material and energy contamination. The influence is seen through degradationof physical and chemical properties of the hydraulicoil. Recently, in condition monitoring techniques, as a maintenance strategy, a lot of authors emphasize using particle influence as a pre‐warning sign in detecting potential failure. Therefore stakeholders in the industry ((engineers and technicians)follow that claim and consequently implement the strategy therby purchaseand install new sensors and equipment in order to eliminate and mitigate system stoppage or reduction in performance. In this paper, however authors propose a slightly different aproach in trend analysis over particle contamination, and that is, using viscosity change as a pre‐warning sign. Besides, authors advocate techniques and methods needed in adequate contamination control of a system

Diesel fuel filtration problems with modern common rail injection systems / Проблемы фильтрирования дизельного топлива в современной системе впрыска common rail / Problem filtriranja dizel-goriva kod savremenih common rail sistema ubrizgavanja

Modern diesel fuel injection systems called ”common rail systems” have been increasingly developing over the past two years. Along with the development of such systems it has been, at the same time, necessary to follow the development of ancillary systems used for their proper and efficient operation. This paper provides a detailed presentation of the latest generation of common rail systems operating at high pressure together with problems regarding diesel fuel filtration. / За последние годы заметно возросло развитие современных систем впрыска дизельного топлива, под названием „common rail“. Наряду с развитием данных систем необходимо одновременно следить за соответстующим развитием вспомогательных систем, которые обеспечивают их правильную и эффективную работу. В данной статье подробно описаны последние поколения common rail систем, которые работают под высоким давлением, а также обсуждаются вопросы фильтрирования дизельного топлива, и подчеркнута проблема загрязнения окружающей среды от промышленного топлива. / Savremeni sistemi za ubrizgavanje dizel goriva, pod nazivom 'common rail' poslednjih nekoliko godina se naglo razvijaju. Uporedo sa razvojem ovih sistema potrebno je istovremeno pratiti i određeni razvoj pomoćnih sistema koji se koriste za njihov pravilan i efikasan rad. U radu je detaljno opisana poslednja generacija common rail sistema koji rade sa visokim radnim pritiscima. Naveden je i problem filtriranja dizel-goriva i izdvajanja nepoželjnih kontaminanata u pogonskom gorivu

Life Cycle Assessment of Different Waste Lubrication Oil Management Options in Serbia

On average, approximately 22 thousand tons of new lubrication oil were marketed annually in Serbia in the period 2015–2019. Less than 20% of the waste lubrication oil (WLO) generated was treated, whereas the remainder was mostly uncollected or improperly disposed of. The purpose of this study is to examine different WLO management scenarios that could be implemented in Serbia in the future and to quantify their potential environmental benefits. Different WLO treatment processes (namely the re-refining of used oil for base oil recovery, the use of WLO as a substitute to fossil fuels in cement kilns, and the combustion of WLO in waste incinerators with energy recovery) were evaluated using the life cycle assessment (LCA) and ReCiPe 2016 impact assessment methods. The LCA results obtained indicate that no single WLO treatment process consistently exerts diminished environmental impacts according to all the impact categories considered. From a human health perspective, the incineration of WLO in waste incinerators was found more favourable than the other treatment processes considered, whereas the combustion in cement kilns was the most favourable approach with regard to ecosystem protection. In terms of fossil fuel savings, re-refining technologies performed slightly better than the other processes considered. This can be accounted for by significant amounts of marketable co-products generated in the re-refining process, which can be used as a substitute to fossil-based primary products. Furthermore, a total of four possible WLO management scenarios were developed on the basis of the annual quantities of untreated WLO and a mix of treatment options. The results obtained indicate that up to 22,100 t CO2 equivalent and 34,300 t oil equivalent could be saved annually in Serbia provided the most favourable WLO management scenario is considered