pneumatic

Karnaugh maps approach to understanding control implementation behind digital pneumatic (1.ªParte)

Industrial processes need to be changed quickly so that different products can be produced. The response to these…

Industrial processes need to be changed quickly so that different products can be produced. The response to these changes requires a reconstruction of the pneumatic control according to the new requests, that is, reconstruction of the control machine. To solve this problem, we present an alternative way to develop dual control for double-path sequence using Karnaugh Maps. In practice, we propose an approach to developing pneumatic control system in complex cases when there are two variants of the control sequence. The equations obtained by Karnaugh Maps (KM) simplified the elaboration of the command of the circuit, be it electro or pneumatic control, guaranteeing not only the realization of the two sequences combined, but as well as minimizing the command variables needed for a digital circuit. A practical example to understand the implementation of the control will be presented. The equations required to control the circuit will be also used in a programmable logic controller (PLC) that will control the circuit. This is an easy methodology to understand and implementing control digital pneumatics.

Introduction

Compressed air is one of the oldest sources of energy. Its distribution and use, under different working pressures, has become widespread and is currently an element that is present in all productive and service sectors. The controlled use of this energy source was called pneumatic (Pneuma), a Greek term meaning blow or breath.

Numbers are the applications that use compressed air as an energy source. Operations such as drilling, tapping, etc., are perfectly fit in mechanization and process automation, replacing the human force, as a work producer, by a constant and uniform external force capable to maintaining high productive rhythms. In this sense, the use of the pneumatic, as a source of energy, will be next to the mechanics, electricity or electronics and hydraulics. This integration will require a more comprehensive knowledge of the technologies to be applied in any process of automation not only from the point of view of the transmission of energy but also the control. Therefore, pneumatic control can be performed pneumatically (use of pneumatics as power source and control), electrically (pneumatic as power source and electricity as control, relay technology), electronically (pneumatics as power source and electronics as control, e.g., PLC) or combined with the hydraulics acting as power source and control and vice versa.

Adriano A. Santos, António F. da Silva
Research Center of Mechanical Engineering (CIDEM), School of Engineering Polytechnic of Porto, (ISEP) Porto, Portugal

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