Since the earliest pages of Control Engineering in the mid-1950s, engineers have argued fervently about the merits of closed-loop versus open-loop control. Please, set up closed-loop controls where possible and let them work their magic (which is what closed-loop control is, to those who don’t know or don’t think about what’s inside the box.)

Why do we need to close more loops? Demographics. Remember the skills gap in the news? There aren’t enough people being trained, the world over, to fill future technology requirements… as we do things right now.

As necessity is the mother of invention (thanks, Plato), we need to engineer more for autonomous operations where it makes sense. If there are fewer engineers and technicians around to design, operate, maintain, and upgrade complex equipment, more designs must be elegant and intelligent enough to operate on their own.

Trust the control loop:

• Measure. Take the right measurement with the right sensors for the application;
• Decide. Make a smart decision, consistently, using logic (hardware and software) to apply historical knowledge, rooted in wisdom, able to anticipate changing application needs; and
• Actuate. Valves, motors, pumps, hydraulics, pneumatics, and other motive forces activate the process to make it go where it should go.

And then repeat, ensuring that networks reliably move messages around the loop, and human-machine interfaces, where needed, reassure humans that things are going just fine.

When the loop is closed, no human intervention is needed. With an open loop, at one or more points, a human intervenes. If we’re going to have fewer humans with enough training, we need to close more loops. And keep it simple.

That is easier said than done, of course, with the current technology installed in most plants. That is why, with your help, we explain (online, in print, and in person), how to better design, select, apply, commission, use, maintain, and upgrade controls, instrumentation, and automation systems worldwide.

Challenges increase as legacy systems meet newer, blended technologies that distribute and embed control loops closer to the process. Sometimes one box can integrate multiple elements needed for closed-loop control, which can be faster, without communication lag time… and more difficult to see. Standards help designs be more understandable, modular, reusable, flexible, scalable, and interoperable.

Fortunately, many automation vendors, original equipment manufacturers, system integrators, and end users increasingly “get it.” It’s all about putting more trust in elegant closed-loop control—the ability to design it, apply it, set it, and forget it.

mhoske@reedbusiness.com