scholarly journals Prediction of dynamics and seaworthiness of amphibious hovercraft

2021 ◽  
Vol 27 (1) ◽  
pp. 22-32
Author(s):  
В.В. Зайцев ◽  
Вал.В. Зайцев ◽  
Д.В. Зайцев ◽  
В.В. Лукашова
Keyword(s):  
Mathematical Models ◽  
Degrees Of Freedom ◽  
High Accuracy ◽  
Sufficient Accuracy ◽  
Trial And Error ◽  
Slow Pace ◽  
Operational Characteristics ◽  
Depth Analysis ◽  
The Cost ◽  
6 Degrees Of Freedom

Annotation – The creation of hovercraft projects is a very expensive procedure, and the emergence of new ships of this type and their evolution is proceeding at a very slow pace. Despite the fact that hovercraft have been used for decades and there is a large amount of literature that is related to the theory of such ships and the practice of their design, there are still a number of unresolved problems associated with these ships. There are various methods, theories and publications that allow to calculate and design various complexes and systems of hovercraft, and as a result, this allows to create vessels that are successful in operation and with good seaworthiness. But at the same time, until now, the main problem remains to achieve sufficient accuracy in predicting the operational characteristics of hovercraft under various modes. Therefore, it is not uncommon for a successful hovercraft project to be born after a series of unsuccessful trial and error. The presented work describes a methodology for creating simulations of hovercraft for various modes of their operation. Various types of simulations of such ships and the ways of their implementation into functioning software are considered. The main mathematical models that are involved in the implementation of such simulations are described and their structure is shown for various hovercraft. The described complex of mathematical models, embodied in the program, allows an in-depth analysis of the dynamics and operational characteristics of hovercraft before the completion of their design and before the start of construction. It is argued that the most difficult, but suitable for real practical problems of analyzing the dynamics of hovercraft is the simulation of this ship with 6 degrees of freedom. The study allows us to conclude that the described methodology for creating a complex of mathematical models makes it possible with high accuracy to predict the dynamics of hovercraft and simulate any hovercraft with 6 degrees of freedom, which will reduce the cost of designing and building a lead hovercraft with accurately predictable seaworthiness and operational characteristics.

High Accuracy, Low-Invasive Displacement Sensor (HALIDS)

2013 ◽  
Author(s):  
Swavik Spiewak ◽  
Curtis Zaiss ◽  
Stephen J. Ludwick
Keyword(s):  
Degrees Of Freedom ◽  
Inertial Sensors ◽  
Signal Transmission ◽  
High Accuracy ◽  
Displacement Sensor ◽  
Reference Base ◽  
Root Cause ◽  
Wireless Signal ◽  
Measurement Units ◽  
6 Degrees Of Freedom

Sub-micron accuracy and precision in measuring unconstrained, spatial motion is pivotal in science and engineering. It imposes stringent requirements on the accuracy, reliability, and invasiveness of sensing devices (including lasers, lidar sensors, or optical scales). While the capabilities of these devices have seen dramatic improvements in the last decades, the needs for sub-micron accuracy, low-invasive sensors greatly outpace the available solutions. The root cause of measurement difficulties is a conflict between the very nature of motion (simultaneous translations and rotations relative to a chosen reference base) and the fundamental requirement of measurement accuracy known as the Abbe principle. Small and accurate Microsystems Technology based inertial sensors (accelerometer and gyroscopes) can alleviate, or at least significantly mitigate, many of the current difficulties. If contained in small Inertial Measurement Units (IMU) and equipped with a wireless signal transmission, they can be placed on or very close to the objects whose motion is to be measured. Furthermore, as long as the IMU, its fixture, and some region of this object around the fixture can be considered as rigid, coordinate transformation rules facilitate converting signals measured by IMU into translations and rotations of any point in this rigid region. Consequently, a virtual 6-DOF sensor can be created. Its dimensions are infinitesimally small, and it can be “placed” anywhere within the above rigid region. In particular, it can be placed such that it is collinear with the displacements of the cutting tool or robot’s end effector, and satisfies the Abbe principle. We present a High Accuracy, Low-Invasive Displacement Sensor (HALIDS) for application in manufacturing and in engineering design. The sensor is capable of measuring simultaneously 6-degrees-of-freedom displacements of objects. Its short term resolution is down to 0.1 nanometer and accuracy better than 1 micron. The sensor can be built small, light and wireless. Results from experimental evaluation of two prototype versions are presented.

4D in in vivo 2-photon laser scanning fluorescence microscopy with sample motion in 6 degrees of freedom

2011 ◽  
Vol 200 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Sabine Scheibe ◽  
Mario M. Dorostkar ◽  
Christian Seebacher ◽  
Rainer Uhl ◽  
Frank Lison ◽  
...  
Keyword(s):  
Fluorescence Microscopy ◽  
Laser Scanning ◽  
Degrees Of Freedom ◽  
Sample Motion ◽  
6 Degrees Of Freedom

Workspace, dexterity and dimensional optimization of microhexapod

2015 ◽  
Vol 35 (4) ◽  
pp. 341-347 ◽  
Author(s):  
E. Rouhani ◽  
M. J. Nategh
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Screw Theory ◽  
Design Parameters ◽  
Dimensional Synthesis ◽  
Content Type ◽  
Workspace Analysis ◽  
The Difference ◽  
Flexure Joints ◽  
6 Degrees Of Freedom

Purpose – The purpose of this paper is to study the workspace and dexterity of a microhexapod which is a 6-degrees of freedom (DOF) parallel compliant manipulator, and also to investigate its dimensional synthesis to maximize the workspace and the global dexterity index at the same time. Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Design/methodology/approach – Microassembly is so essential in the current industry for manufacturing complicated structures. Most of the micromanipulators suffer from their restricted workspace because of using flexure joints compared to the conventional ones. In addition, the controllability of micromanipulators inside the whole workspace is very vital. Thus, it is very important to select the design parameters in a way that not only maximize the workspace but also its global dexterity index. Findings – It has been shown that the proposed procedure for the workspace calculation can considerably speed the required calculations. The optimization results show that a converged-diverged configuration of pods and an increase in the difference between the moving and the stationary platforms’ radii cause the global dexterity index to increase and the workspace to decrease. Originality/value – The proposed algorithm for the workspace analysis is very important, especially when it is an objective function of an optimization problem based on the search method. In addition, using screw theory can simply construct the homogeneous Jacobian matrix. The proposed methodology can be used for any other micromanipulator.

Contour Extraction of Cerebrovascular Based on Maximum Optimization Cost

2011 ◽  
Vol 204-210 ◽  
pp. 1415-1418
Author(s):  
De Jiang Zhang ◽  
Na Na Dong ◽  
Xiao Mei Lin
Keyword(s):  
Dynamic Programming ◽  
Blood Vessel ◽  
High Efficiency ◽  
High Accuracy ◽  
Differential Method ◽  
Cost Curve ◽  
Contour Extraction ◽  
Target Image ◽  
The Cost ◽  
Conventional Algorithm

By studying the conventional algorithm of contour extraction, a new method of contour extraction in blood vessel of brain is proposed based on the MOC maximum optimization cost. First of all, the theory computes the gray differential of the image by conventional differential method to build the cost space. Then, by using dynamic programming theory, the maximum optimization cost curve in the space is extracted to serve as the specific cerebrovascular profile. The experiments show that this method ensures high efficiency in extracting cerebrovascular contour and a high accuracy in positioning cerebrovascular contour, and it diminishes the target image ambiguity caused by noise to improve the anti-interference ability of Contour extraction.

An improved calibration curve between soil pH measured in waterand CaCl2

Soil Research ◽  
2002 ◽  
Vol 40 (8) ◽  
pp. 1399 ◽  
Author(s):  
B. L. Henderson ◽  
E. N. Bui
Keyword(s):  
Statistical Analysis ◽  
Water Resources ◽  
Soil Ph ◽  
Calibration Curve ◽  
Smooth Function ◽  
Degrees Of Freedom ◽  
Additive Model ◽  
Smoothing Spline ◽  
Look Up Table ◽  
6 Degrees Of Freedom

A new pH water to pH CaCl2 calibration curve was derived from data pooled from 2 National Land and Water Resources Audit projects. A total of 70465 observations with both pH in water and pH in CaCl2 were available for statistical analysis. An additive model for pH in CaCl2 was fitted from a smooth function of pH in water created by a smoothing spline with 6 degrees of freedom. This model appeared stable outside the range of the data and performed well (R2 = 96.2, s = 0.24). The additive model for conversion of pHw to pHCa is sigmoidal over the range of pH 2.5 to 10.5 and is similar in shape to earlier models. Using this new model, a look-up table for converting pHw to pHCa was created.

scholarly journals MODIFYING MATHEMATICAL MODELS FOR CALCULATING OPERATIONAL CHARACTERISTICS OF DIESEL ENGINES BURNING RME BIOFUELS / MATEMATINIŲ MODELIŲ PRITAIKYMAS DYZELIŲ, DIRBANČIŲ RME BIODEGALAIS, DARBO PROCESUI IR EKSPLOATACINIAMS RODIKLIAMS SKAIČIUOTI / ДОРАБОТКА МАТЕМАТИЧЕСКИХ МОДЕЛЕЙ РАСЧЕТА ПОКАЗАТЕЛЕЙ РАБОТЫ ДИЗЕЛЯ НА БИОДИЗЕЛИНАХ РРМЭ

Transport ◽  
2011 ◽  
Vol 26 (1) ◽  
pp. 50-60 ◽  
Author(s):  
Sergejus Lebedevas ◽  
Galina Lebedeva ◽  
Kristina Bereišienė
Keyword(s):  
Diesel Engine ◽  
Mathematical Modelling ◽  
Mathematical Models ◽  
Diesel Engines ◽  
Fuel Injection ◽  
Internal Heat ◽  
Computer Programs ◽  
Toxic Substances ◽  
Load Range ◽  
Operational Characteristics

The article considers and solves the problems of adapting the mathematical models, used in calculating operational characteristics of diesel engines burning mineral diesel oil, to engines converted to RME biofuels. The analysis of mathematical models of calculating the main technical and economic characteristics of diesel engines as well as the parameters of the in-cylinder process and the concentration of toxic substances in the exhaust gases is performed. The need for adjusting the calculation algorithms is also demonstrated. The computer programs based on single-zone thermodynamic models are used in the research. The programs of mathematical modelling are modified, i.e. supplemented with the algorithm for calculating energy characteristics of the combustion products (e.g. specific heat capacity, internal heat, the lower calorific value, etc.). Based on the computer programs, modified for examining diesel engines burning biofuels, the computer-aided mathematical modelling experiment is carried out. The results of modelling are compared with the data obtained in testing the diesel engine 1A41. The mathematical modelling performed demonstrates the accuracy acceptable for solving practical problems: the difference between the obtained calculation results and diesel engine testing data for the load range of (1.0÷0.5) Pi nom does not exceed ± 5÷7%. Higher accuracy of modelling the characteristics of diesel engines, operating in the low- and medium-load modes, may be accounted for by the adjustment of the algorithm for calculating the induction period and the on-set phase of fuel injection. Santrauka Publikacijoje pateikti dyzelio darbo proceso ir eksploatacinių rodiklių skaičiavimo matematinių modelių tobulinimo rezultatai, siekiant matematinius modelius pritaikyti dyzeliui dirbant riebiųjų rūgščių metilesterių, taip pat RME, biodegalais. Atlikta skaičiavimo algoritmų analizė ir pagrįsti pagrindiniai jų tobulinimo aspektai. Sukurtas kompiuterinis programinis modelis, skirtas darbinio kūno dyzelio cilindre energiniams parametrams skaičiuoti (specifinei šilumai, vidinei energijai), dyzeliui dirbant plačiąja elementinės cheminės sudėties biodegalų gama. Atliktas 1A41 dyzelio techninių ir ekonominių bei ekologinių rodiklių modeliavimas kompiuteriu, naudojant patobulintus matematinius modelius. Parodytas gautų rezultatų, pakankamų praktiniams uždaviniams spręsti, tikslumas: dyzeliui dirbant artimos nominaliosios apkrovos režimais (1,0÷0,5) Pi nom skirtumas tarp skaičiavimo ir dyzelio motorinių tyrimų rezultatų neviršija ±5÷7%. Dyzeliui dirbant mažos apkrovos režimu, matematinio modeliavimo rezultatų adekvatumo didinimas susijęs su kuro įpurškimo fazės bei savaiminio užsiliepsnojimo indukcijos periodo skaičiavimo algoritmo tobulinimu. Резюме Рассмотрены и решены задачи адаптации математических моделей расчета показателей дизеля при переводе их работы с минерального дизелина на биодизелины метилового эфира рапсового масла (МЭРМ). Выполнен анализ и дано обоснование направлений доработки расчетных алгоритмов ряда однозонных термодинамических математических моделей, используемых в практике исследования эксплуатационных показателей, параметров индикаторного процесса и эмиссии токсичных компонентов в выхлопных газах дизелей. В форме программного модуля составлен алгоритм расчета энергетических параметров рабочего тела в цилиндре (удельной теплоемкости, теплоты сгорания, внутренней энергии) для топлив с широким элементарным химическим составом. С использованием доработанных компьютерных программ выполнен широкий расчетный эксперимент и сопоставлены его результаты с данными моторных стендовых испытаний одноцилиндрового отсека дизеля 1А41. Показана приемлемая для решения практических задач точность математического моделирования: для нагрузочных режимов (1÷0,5) Pmi расхождения расчетных и экспериментальных значений параметров работы дизеля не превышают ±5÷7%. Повышение качества моделирования показателей дизеля на режимах средних и малых нагрузок связано с уточнением алгоритма расчета периода индукции и фазы начала видимого горения топлива в цилиндре.

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