PLC in Automation
Today, programmable controllers are an elementary component of state-of-the-art automation solutions. Intelligent solutions are not based on a conflict between these systems, but on unity. With important advantages like,robustness and easy handling, the PLC continues to guarantee its success. Its further development will be dependent on more & more steadfast integration of information & technology. For the engineering process, this means an integrated workflow that covers all engineering tools; for production, it means transparency of the data flow between a company's production processes and its business processes.
If official market studies of a few years ago were to be believed, the PC was supposed to replace the PLCs completely which meant PLCs would play very little or no role in automation. However, the fact is, the PLC's market volume, worldwide, has grown from one billion euros in 1982 to 4.5 billion euros proves that automation without PLC's is unimaginable and growth is continuous.
Robustness is an important prerequisite for the success of the PLC. Most state-of-the-art controllers are easy to use, modular, and require no fan. Sometimes, modules can even be removed or inserted while energised (a process referred to as hot swapping).
Today, a PLC is distinguished by a large number of scalable technology functions suchas counting, measuring, positioning, closed-loop control or cam control. With a graduated selection, which extends from entry-level PLCs to high-performance models, there is a suitable solution for every task.
As far as programming and configuring are concerned, there is much to choose from the basic LAD, FBD and STL programming languages over graphical languages for sequencers, state graphs and process flow charts to high-level languages Particular attention is paid to integrated engineering. The repeated input of data means not only more overheads, but also an increased danger of input errors. Both must be avoided through the interaction of modern engineering tools for program development, including HMI and communication.
The possibility of simulation shortens the test phase and can be used to optimise functional sequences without the need for target hardware. In addition, open interfaces can be used to import or export data, for instance from upstream planning tools.
All important bus systems, such as AS-Interface, Profibus and Industrial Ethernet, can be connected over different communication interfaces. Modern information technologies (IT) based on Industrial Ethernet offer simple solutions for local or global business networks. The basis for safe global communication is TCP/IP. The use of Web technologies and an email function make worldwide communication in the automation world possible.
Fail-safety is increasingly becoming a must feature these days for any powerful PLC. Wherever the highest continuous safety is required for humans, machines and the environment, fail-safe controllers are absolutely essential. They are suitable for the processing of safety-related functions. When a fault occurs, they immediately switch to a safe state. The most sophisticated controllers now offer an integrated safety concept, i.e. the bringing together of safety level with standard automation to form a transparent system.
Today's PLCs are capable of controlling extremely fast machining processes. Process response times must be defined and reproducible, even in distributed solutions. The IO signals must be read in and read out in an equidistant time frame and synchronised with the user program - a must for sophisticated motion control tasks.
Plant or Machine availability - an important topic
Powerful integrated system diagnostic functions increase the availability of the controller and help during the commissioning phase. Thanks to plain text messages showing the type of fault, the date and a time stamp, faults can be quickly rectified either locally or via remote diagnostics. In cases where availability plays an important role, there are also high-availability control systems in which a standby assumes control in the case of a device failure, preventing production delays in round-theclock production environments.
In recent years, PLC applications have grown to include process engineering. This requires the capability to carry out plant modifications and expansions even while the plant is in operation, regardless of whether this involves adding sensors or actuators or simply assigning new parameters to a module. The PLC was able to penetrate this application field thanks to hardware and software for intrinsically safe, fail-safe and high availability solutions and engineering that speaks the "process language".
Integration is the crux
In all sectors, interesting solutions can be found which have been implemented with products from PC-based Automation, Soft PLC, Slot PLC or embedded solutions. The automation engineer is confronted on the one hand with the task of deciding the optimum hardware platform and on the other hand with having to maintain continuity in programming, maintenance, HMI and communication. Maximum discretion can be attained with an integrated spectrum, which also includes the standard PLC. The user program can operate without modification on both the standard PLC as well as on the Soft PLC or Slot PLC. The result is unity rather than conflict. The right solution can be selected in dependence on the primary focus of the task in question.
New automation solutions with the PLC on the b asis of distributed intelligence
The use of distributed intelligence is a huge step forward in modular plant and machine construction. In this conjunction, PLCs can serve as the intelligent, freely programmable core of a plant or machine module. The modules are developed and tested autonomously. The advantages are the ease with which these modules can be re-used and the clean interplay between modules over standardised communication links.
Automation remains innovative - The PLC remains the basis
The ability to respond morequickly to changes in the market and implement increasingly individualised mass production require production to be flexible.
All required information must be available anywhere in the company at any time. This makes it possible to ensure a continuous information flow over the entire supply chain, from suppliers over the company's own production to the customer, taking into consideration the company's business processes (ERP).
The main challenges to production are detecting faults before they can cause a failure and organising maintenance tasks. One approach to this problem is a cross-production maintenance and service concept.
The engineering process for the development of a plant or machine also requires an integrated flow of information between all participating engineering tools. The island solutions which frequently exist today, in which multiple experts with limited responsibilities and competence master their part of the overall process, must melt together in future into an integrated workflow which extends from rough design to successful commissioning, making it possible to progress more quickly from initial idea to productive operation.
The further development of automation technology is therefore no longer distinguished by the individual development of individual components and products; instead, the main objective is the integration of all components belonging to an automation solution. In future, the PLC will continue to play a central role in automation.
- N Girish