Evolving control systems

Control systems are in another evolutionary period. Usually this remark is taken to mean a technology leap in the controller. The complete system, however, is more than just the controller, and changes are occurring in every part of the system. As Control Engineering covers these changes during the year, it is useful to look at each product and subsystem in contex.


Control systems are in another evolutionary period. Usually this remark is taken to mean a technology leap in the controller. The complete system, however, is more than just the controller, and changes are occurring in every part of the system. As Control Engineering covers these changes during the year, it is useful to look at each product and subsystem in contex.

Almost everyone learns basic systems theory today. Briefly, each system has inputs, a decision-making element, outputs, and feedback to close the loop. Control system architecture includes input devices to the controller that serves as the decision-making element, and output devices that make things happen. Feedback is accomplished through the controller to advise operators, technicians, and engineers of abnormal behavior and gather data.

Sensing the environment

Control systems must know the status of the process and its environment. Input devices are the eyes, ears, and touch that the controller needs to determine necessary actions. Typical input devices range from pushbuttons and selector switches, through proximity and photoelectric sensors, to temperature and pressure sensors.

Today's sensors provide more than simple binary (on or off) inputs or varied current or voltage (4-20 mA or 0-10 V dc), although these are still very important. Vision systems providing complex information have become stable and affordable. Bar-code equipment is also part of the information providing system as well as status to the system.

Modern networks enable economical and fast data communication from sensors and other input devices to the controller. Since manufacturing management software now demands more and better information from the lowest level in the plant, these advances help power complete manufacturing enterprise progress.

Controllers and decision making

CE reports and analyzes both types of manufacturing systems-process and discrete. Where it was once believed that these were distinct types of manufacturing never to merge, that border has now been breached. It is becoming increasingly difficult to tell process controllers (DCS) from discrete manufacturing controllers (PLC). To add to the confusion, computer numerical controllers (CNCs) are now blending with PLCs to handle automation as well as machining. Robotic controllers are also now able to handle more automation and data management chores.

The newer system architectures (see diagrams) highlight separating I/O modules from the controller chassis. This means a single cable serves in long wiring runs, rather than bundles of parallel wiring. Wiring from sensors and actuators to the I/O modules is reduced to the shortest possible route. Tracing wires becomes much easier, and common wiring problems are reduced.

To a large part, this is because of market and technology penetration of personal computers (PCs). PCs now are used as controllers, operator interface, communications interface, programming terminal, and data concentrator. As a result, such things as the computer operating system, control software, and other components have become topics of discussion. Few people knew, or cared, what the operating system, chip set, or backplane bus structure was in a PLC or DCS. Now engineers openly debate the merits of Microsoft Windows NT, or embedded operating systems like Windows NT Embedded or CE.

Outputs get things done

Once the controller scans input status ascertaining the environment and makes decisions based on programmed logic, it turns outputs on or off as required. Output devices are usually denoted as coils in programs because the typical response is to energize a coil in a motor starter, relay, or solenoid. Other outputs can be an analog signal to a variable frequency drive controlling a pump or fan or a message sent to a display.

What's in the future? Look for controller functions to move out to I/O modules then to devices. Intelligent devices will form loops of local control networked to a supervisory controller. Communication loss to the controller will not immediately shut down the process or machine unless a safety has been triggered. Networks and software will become more important and embedded control will reside at the device level. The system will be monitored by Web browser technology, often on a wireless pocket computer.

Author Information

Gary A. Mintchell, senior editor, gmintchell@cahners.com

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Learn how to create value with re-use; gain productivity with lean automation and connectivity, and optimize panel design and construction.
Go deep: Automation tackles offshore oil challenges; Ethernet advice; Wireless robotics; Product exclusives; Digital edition exclusives
Lost in the gray scale? How to get effective HMIs; Best practices: Integrate old and new wireless systems; Smart software, networks; Service provider certifications
Fixing PID: Part 2: Tweaking controller strategy; Machine safety networks; Salary survey and career advice; Smart I/O architecture; Product exclusives
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Look at the basics of industrial wireless technologies, wireless concepts, wireless standards, and wireless best practices with Daniel E. Capano of Diversified Technical Services Inc.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.