Digital fluid systems are controlled solely by onoff valves, in contrast to analogue fluid systems which use continuously adjustable valves. Many digital fluid systems have been in practical use for some decades. The steel industry relies on several fluid technologies. Apart from the handling of the liquid steel, several other fluid processes exist to fulfill indispensable functions; examples include cooling, motion control, torch cutting, descaling, and lubricating. Many of these processes need better control concerning precision, dynamics, resource demand, reliability, and environmental impact or must offer additional functionalities for use in factories of the future. In several cases digital fluid systems are the better solutions. In this paper this is demonstrated by four examples, ranging from proven simple solutions and concepts going currently into industrial application to promising concepts for the future.
Hydraulic control with switching valves can excite undesirable hydraulic and mechanical oscillations; hence, control performance is inadequate. There are different ways to cope with such oscillations. One way is to change the design or to add some damping elements which improve the attenuation of the oscillations. Another way is to actuate the system in an appropriate way -so that almost no unwanted oscillations are excited. This article illustrates that optimal feedforward control theory can be used to obtain a realisable switching valve command which avoids ongoing oscillations for the case of a fast position step. A system composed of a dual-stroke cylinder with its piston chamber connected to the switching valves by some pipeline and its rod chamber to pre-pressurised accumulators for counterbalancing is modelled as a discrete dynamical system of order 9. The optimal control problem is conditioned such that the resulting valve signals can be approximately realised by the existing switching valves. For this realisation, the so-called ballistic mode of switching valves plays an important role. The theoretical results are tested experimentally on a proper test rig.
Design and layout:University of Maribor Press No. of Copies 120Published in: September 2017 © University of Maribor PressAll rights reserved. No part of this book may be reprinted or reproduced or utilized in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publisher. The International Fluid Power Conference is a two day event, intended for all those professionally-involved with hydraulic or pneumatic power devices and for all those, wishing to be informed about the 'state of the art', new discoveries and innovations within the field of hydraulics and pneumatics. CIP -Kataložni zapis o publikacijiThe gathering of experts at this conference in Maribor has been a tradition since 1995, and is organised by the Faculty of Mechanical Engineering at the University of Maribor, in Slovenia. Fluid Power conferences are organised every second year and cover those principal technical events within the field of fluid power technologies in Slovenia, and throughout this region of Europe. This year's conference is taking place on the 14th and 15th September in Maribor.We wish all participants at the International Conference-Fluid Power 2017 continued successful professional work, and hope that we have yet again added another small piece within the mosaic of fluid power. 1The role of pneumatics in digital systems Industry 4.0 represents a future where intelligent machines are self-aware and automation challenges can be solved by the machinery itself. In the factory of tomorrow, cyber-physical systems will communicate with one another using the Internet of Things. Microsystems will make decisions autonomously and highly sensitive robots will support employees so that they can continue to work, even in their later years.Pneumatic applications are sturdy and reliable, which from an Industry 4.0 perspective might also be interpreted as inflexible. For pneumatics, this concept seems to leave only peripheral tasks. Simple, repetitive tasks might remain under the control of some intelligent sub-system. The "natural" motion for intelligent cyberphysical systems seems to be driven electrically.For machine builders and machine operators pneumatic controls come with some additional challenges, since every logical function comes encapsulated in a physical valve. Changing the functionality means exchanging the valve. This also means that potentially a lot of valves and other pneumatic function elements such as throttles are kept on stock resulting in costs. Pneumatic valve terminal with controller and multiple functions, where any combination of functions can be implemented, but changing functions requires physical changes is shown in Figure 1. Digital pneumaticsAs a response to above mentioned challenges, Festo has developed the Festo Motion Terminal, the world's first standardised platform that will develop into a "cyber-physical system" thanks to its intelligent fusi...
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