Development of a Position Controlled Digital Hydraulic Valve

2015 ◽  
Author(s):  
N. P. Sell ◽  
N. Johnston ◽  
A. R. Plummer ◽  
S. Kudzma
Keyword(s):  
Pressure Drop ◽  
Position Control ◽  
Hybrid Control ◽  
The Other ◽  
Modern World ◽  
Empirical Testing ◽  
High Frequencies ◽  
Control Approach ◽  
High Flows ◽  
Hydraulic Valve

Digital hydraulics is a key part of the continuing applicability of fluid power in the modern world. In order to realize the potential of digital hydraulic circuits, valves which are able to switch at high frequencies whilst retaining high flows are first required. This paper details the development of a valve which is capable of switching in 0.5ms whilst providing a flow rate of over 50L/min at a 10bar pressure drop. Unlike most of the other valves currently in development, position control is used as opposed to the more common bang-bang actuation. This has obvious benefits for valve robustness and offers the possibility of a hybrid control approach which utilizes both throttling and switching control. This paper will detail the design and empirical testing of the valve and benchmark it against published and commercial valves before proceeding to discuss the challenges present in developing the valve further.

scholarly journals Angular Position Control of 3-Cars Crane System Using Proposed Fuzzy-PID Controller

2021 ◽  
Vol 7 (1.) ◽  
Author(s):  
Şahin YILDIRIM
Keyword(s):  
Real Time ◽  
Simulation Study ◽  
Pid Controller ◽  
Position Control ◽  
Angular Position ◽  
The Other ◽  
Fuzzy Pid ◽  
Control Approach ◽  
Fuzzy Pid Controller ◽  
Simulation Results

This paper presents a novel control approach for 3 cars crane systems. Nowadays; some problems for carrying unpredicted loads of crane systems exist. On the other hand; long bar loads are very important to carry without touch on other materials in factories. In this simulation study, fuzzy based controllers were designed to control vibrations of 3 cars crane system. The simulation results are improved and show this kind of controllers will be employed in real time such systems.

Pressure Drop Measurements for Air Flow Through Open-Cell Aluminum Foam

2004 ◽  
Author(s):  
Nihad Dukhan ◽  
Angel Alvarez
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Aluminum Foam ◽  
Flow Direction ◽  
The Other ◽  
Turbulent Regime ◽  
Thick Sample ◽  
Open Cell ◽  
Two Samples

Wind-tunnel pressure drop measurements for airflow through two samples of forty-pore-per-inch commercially available open-cell aluminum foam were undertaken. Each sample’s cross-sectional area perpendicular to the flow direction measured 10.16 cm by 24.13 cm. The thickness in the flow direction was 10.16 cm for one sample and 5.08 cm for the other. The flow rate ranged from 0.016 to 0.101 m3/s for the thick sample and from 0.025 to 0.134 m3/s for the other. The data were all in the fully turbulent regime. The pressure drop for both samples increased with increasing flow rate and followed a quadratic behavior. The permeability and the inertia coefficient showed some scatter with average values of 4.6 × 10−8 m2 and 2.9 × 10−8 m2, and 0.086 and 0.066 for the thick and the thin samples, respectively. The friction factor decayed with the Reynolds number and was weakly dependent on the Reynolds number for Reynolds number greater than 35.

The Reformation of the Sixteenth Century in Renaissance Italy

1981 ◽  
Vol 17 ◽  
pp. 149-166 ◽  
Author(s):  
Philip M. J. McNair
Keyword(s):  
Sixteenth Century ◽  
The Other ◽  
Protestant Reformation ◽  
Modern World ◽  
The Reformation ◽  
Giordano Bruno ◽  
The Subject ◽  
Renaissance Italy ◽  
The One

Between the execution of Gerolamo Savonarola at Florence in May 1498 and the execution of Giordano Bruno at Rome in February 1600, western Christendom was convulsed by the protestant reformation, and the subject of this paper is the effect that that revolution had on the Italy that nourished and martyred those two unique yet representative men: unique in the power and complexity of their personalities, representative because the one sums up the medieval world with all its strengths and weaknesses while the other heralds the questing and questioning modern world in which we live.

Hybrid Control of the Berkeley Lower Extremity Exoskeleton (BLEEX)

2005 ◽  
Author(s):  
Lihua Huang ◽  
Ryan Ryan Steger ◽  
H. Kazerooni
Keyword(s):  
Position Control ◽  
Hybrid Control ◽  
System Sensitivity ◽  
Walking Gait ◽  
Mixed Control ◽  
Stance Control ◽  
Control Scheme ◽  
Load Carrying ◽  
Human Limb ◽  
Careful Design

The first functional load-carrying and energetically autonomous exoskeleton was demonstrated at U.C. Berkeley, walking at the average speed of 0.9 m/s (2 mph) while carrying a 34 kg (75 lb) payload. The original BLEEX sensitivity amplification controller, based on positive feedback, was designed to increase the closed loop system sensitivity to its wearer’s forces and torques without any direct measurement from the wearer. The controller was successful at allowing natural and unobstructed load support for the pilot. This article presents an improved control scheme we call “mixed” control that adds robustness to changing BLEEX backpack payload. The walking gait cycle is divided into stance control and swing control phases. Position control is used for the BLEEX stance leg (including torso and backpack) and the sensitivity amplification controller is used for the swing leg. The controller is also designed to smoothly transitions between these two schemes as the pilot walks. With mixed control, the controller does not require a good model of the BLEEX torso and payload, which is difficult to obtain and subject to change as payload is added and removed. As a tradeoff, the position control used in this method requires the human to wear seven inclinometers to measure human limb and torso angles. These additional sensors require careful design to securely fasten them to the human and increase the time to don (and doff) BLEEX.

Assembly Strategies for Parts with a Plane of Symmetry

Robotica ◽  
1991 ◽  
Vol 9 (2) ◽  
pp. 189-195 ◽  
Author(s):  
N. A. Aspragathos
Keyword(s):  
Large Class ◽  
Position Control ◽  
Hybrid Control ◽  
Robotic System ◽  
Torque Sensor ◽  
Complex Assembly ◽  
Assembly Tasks

SUMMARYThis paper describes the development of assembly strategies based on hybrid force/position control. The assembly strategies developed are confined to the large class of assembly tasks defined as a peg-in-the-hole assembly having a plane of symmetry passing through the axis of insertion.The basic idea to develop a robotic system for programmable assembly is presented. This system can currently operate controlled manipulators with minor modifications, i.e. if a force/torque sensor and proper software for hybrid control are provided.The principles of writing assembly strategies are analysed and examples of more complex assembly tasks than the classic round peg-in-the-hole are discussed in detail.

The Apocalyptic Image of the Beast in William Blake’s ‘The Tyger’ and W.B. Yeats’ ‘The Second Coming’

2021 ◽  
Vol 33 (3-4) ◽  
pp. 47-61
Author(s):  
Yasser K. R. Aman
Keyword(s):  
William Blake ◽  
The Other ◽  
Modern World ◽  
Christian Religion ◽  
The World ◽  
The Difference ◽  
Second Coming

The monstrous image created by William Blake in ‘The Tyger’ left the world wrapped in an apocalyptic vision that creates an epiphany of unknown Romantic potentials symbolised in ‘The Tyger’. The apocalyptic vision, deeply rooted in Christian religion, develops into an ominous harbinger of the destruction of the modern world portrayed in W.B. Yeats’ ‘The Second Coming’. The image of the beast marks the difference between two ages, one with strong potentials and the other with fear and resident evil unexplained. I argue that the apocalyptic theory in Christianity has an impact on the development of the image of the beast in both poems, an impact that highlights man’s retreat from Nature into the modern world which may fall apart because of beastly practices.

Stiffness Control of Parallel Continuum Robots

2018 ◽  
Author(s):  
Vincent Aloi ◽  
Caroline Black ◽  
Caleb Rucker
Keyword(s):  
Position Control ◽  
Target Position ◽  
Human Robot Interaction ◽  
Force Measurements ◽  
Modeling Framework ◽  
Continuum Robots ◽  
Integral Control ◽  
Control Approach ◽  
Cosserat Rods ◽  
Stiffness Control

Parallel continuum robots can provide compact, compliant manipulation of tools in robotic surgery and larger-scale human robot interaction. In this paper we address stiffness control of parallel continuum robots using a general nonlinear kinetostatic modeling framework based on Cosserat rods. We use a model formulation that estimates the applied end-effector force and pose using actuator force measurements. An integral control approach then modifies the commanded target position based on the desired stiffness behavior and the estimated force and position. We then use low-level position control of the actuators to achieve the modified target position. Experimental results show that after calibration of a single model parameter, the proposed approach achieves accurate stiffness control in various directions and poses.

scholarly journals RISKS OF THE EDUCATION

THE BULLETIN ◽  
2021 ◽  
Vol 2 (390) ◽  
pp. 44-49
Author(s):  
R. Aetdinova ◽  
I. Maslova ◽  
Sh. Niyazbekova ◽  
O. Balabanova ◽  
Zh. Zhakiyanova ◽  
...  
Keyword(s):  
Educational Institution ◽  
Final Analysis ◽  
Quality Education ◽  
The Other ◽  
Educational Institutions ◽  
Modern World ◽  
High Quality ◽  
High Quality Education ◽  
The One ◽  
The University

The article justifies for the need to identify and to keep track, in practice, of different groups of risks inherent in educational institutions under current conditions of pandemic and post-pandemic transformation of education under the influence of modern world uncertainty. Transformation of education functions in the epoch of digital economy changes the content and types of risks concomitant to the activities carried out by schools. Schools belong to the most conservative types of organizations. However, the environment in which schools operate is constantly changing. An educational institution, as any enterprise, has to engage in the activity aimed at risk management. Manifestation of the risk is, on the one hand, fraught with threats and damage, on the other hand, with opportunities. Assessment of possible threats and risks allows timely projection of undesirable results, creation of a system for situational response to unforeseen circumstances and, in the final analysis, formulation of a strategy for development of the university which would allow achievement of modern high quality education, its fundamentality and conformity to important topical requirements of the personality, society and state. Causes of developing risks characteristic of educational institutions are disclosed. External and internal risks characteristic of educational institutions, sources generating them and the importance of managing them are analyzed. The analysis of risks made reveals multi-varied threats and opportunities in the external and internal envi-ronment of the institution and their ability to have a significant effect on educational, organizational and financial activities of the schools.

scholarly journals CULTURAL IDENTITY, TRADITION, AND THE RITUAL KILLING OF BULLS – A NOTE ON A RECENT DECISION OF THE FRENCH CONSTITUTIONAL COUNCIL ON THE LEGALITY OF BULLFIGHTING

Obiter ◽  
2021 ◽  
Vol 34 (2) ◽  
Author(s):  
Stephen Peté ◽  
Angela Crocker
Keyword(s):  
South Africa ◽  
Animal Welfare ◽  
Animal Rights ◽  
The Other ◽  
Modern World ◽  
Cultural Issues ◽  
Public Controversy ◽  
Legal Challenge ◽  
Kwazulu Natal ◽  
The Republic

In a recent two-part article in this journal, the authors of this note analysed the controversy surrounding the ritual bull-killing which takes place during the Ukweshwama “first fruits” ceremony held each year in northern KwaZulu-Natal, South Africa. While much of the Ukweshwama ceremony is uncontroversial, the ritual killing of a bull by young Zulu warriors with their bare hands attracted strong opposition from certain animal-rights groups, which resulted in legal action and public controversy. The authors attempted to disentangle the different legal, historical, political and philosophical strands which combined to make up a complex story about the place of ancient rituals in the modern world, particularly those involving animal sacrifice. They also attempted to situate the controversy around the Ukweshwama bull-killing ritual within a contemporary global context, by comparing and contrasting the Zulu bull-killing ceremony on the one hand, and Spanish bullfighting on the other. The purpose of the present note is to report on recent developments in what is a global debate on the place of ancient rituals which involve the ritual killing of animals, within modern constitutional democracies. In particular, this note will examine and discuss the outcome of a recent legal challenge brought before the Constitutional Council of the Republic of France by certain animal-welfare groups in that country. The challenge was directed at bringing an end to a legal exception which operates in certain parts of the country – that is, those with an uninterrupted local tradition of bullfighting – excluding bullfighting from the provisions of animal-welfare legislation. The legal, political and cultural issues which arise as a result of this legal challenge are of relevance to those in South Africa who are concerned, one way or the other, about the future of the annual Ukweshwama bull-killing ritual in KwaZulu-Natal. Like it or not, although the bull-killing rituals which take place in the South of France and in KwaZulu-Natal South Africa are very different, the similarities between the rituals and their impact on broader society (legally, politically and culturally), are such that they cannot be ignored. The authors make a similar point in relation to the links between Spanish bullfighting and the Ukweshwama bull-killing ritual.

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