The great enabler: PLCs and the industrial internet of things
12 Mai 2017

In an industrial world that’s becoming ever more complex, technology is an enabler. It allows us to collect and make sense of data in new ways, leading us to make better decisions about how we run our businesses. Take the Industrial Internet of Things (IIoT) for example.

In under a century we’ve seen industry transform through the third industrial revolution. The latest progression, Industry 4.0, introduced the idea of the smart factory. Now we’re reaching the tipping point where technology is mature enough to make that vision happen on a global scale. Jamie Smith at Control Techniques looks at the lynchpin that’s making the Industrial Internet of Things (IIoT) a reality.

We’ve come a long way since industry 2.0

If you go back long enough, times before PLCs were around, we had relay, timers, and electric loop controllers. Process control systems were highly distributed and hardwired into the factory. Monitoring these systems was time consuming and would often require technicians to walk around the factory all day long. As you can imagine, this made fault finding very difficult. Clearly a serious problem for high value businesses where downtime could cost millions of dollars. This spurred a growing demand for integrated control. As a result, engineers began looking for a reliable alternative to relay logic. Out of this emerged programmable logic controllers, or PLCs.

PLCs used to be so big that businesses would install PLCs in central control rooms due to their size and environmental requirements. They were remotely wired to field devices using huge amounts of cable. Even with all the additional expense, PLCs made a huge impact. Faults were easier to find, downtime reduced, throughput increased and safety improved. In the end, it came down to making a business more profitable, and the PLC achieved that.

The tipping point for the industrial internet of things (IIoT)

Thanks to the development in technology, PLCs have steadily shrunk in size, cost and are capable of operating in harsher environments. This has presented new opportunities to increase the level of control. Now we can connect together all our machines, in multiple factories, in any part of the world. Those machines can run a master program fed from a smaller central controller to individual PLCs. For less complicated processes, a simple outboard PLC on a device removes the need for complex and costly electromechanical options.

More businesses will be able to benefit from the Industrial Internet of Things (IIoT) as the technology becomes more affordable. For instance, certain low cost AC drives now come with an onboard PLC at no extra cost. It must be very appealing for OEMs.

Some the major benefits of using a decentralised PLC

  1. Large PLCs can be expensive. One option is to remove the central controller and spread the work across smaller PLCs. The cost could be further reduced by using an AC drive with onboard PLC.
  2. When upgrading or making a change to a system, extra coding may be required. On a centralised control system this could mean shutting down a whole production line. The other option is to have a local controller that can be isolated, leaving the rest of the line to keep going.
  3. In some cases, processes run too fast for a central controller to respond immediately. By having a decentralised controller it’s possible to reduce lag, benefiting in more uptime.
  4. It’s easy to connect when the unit is local to the operator. This allows for capabilities such as trending analysis, alarming, batching or even, printing.
  5. It can be difficult to troubleshoot when using one large system, as opposed to working on smaller ones. Distributed control software is easier to maintain as there is less information to analyse.
  6. Field-based distributed controllers do not wholly rely upon the central controller. So in the event that the central controller goes into fault, the entire process won’t fail. This allows the user to continue running their process.
  7. A great benefit of having a distributed system is that it’s easier to partition. You can have enhanced safety using zoned interlocks or light guards.

In defence of the centralised system

There’s a reason why many people still use centralised systems. To begin with, they are proven over many years as an effective way of managing factory wide communications. Changing a system would be expensive and counterproductive, why introduce needless downtime when something already works well?

For new equipment, decentralisation might add extra complexity which is not needed. So in industries where airborne particles or temperature can cause malfunction, a simple setup with a conditioned centralised PLC is the better option.

Most importantly, you need a master in your system. That means one PLC which sends the master communications to the rest of your system. Usually these are powerful processors which spur off messages to smaller follower PLCs. What’s great about this approach is that we keep control centralised, but gain from the autonomy of individual parts of the system.

The linchpin of change

Until recently size, communication and software standards all impacted on our choices. They forced our hand when building equipment. The possibilities of the Industrial Internet of Things (IIoT) is about to be realised. Before long new businesses will start to appear, offering the same products but producing more intelligent products that increase uptime.

The question is, are you ready for the next wave of innovation and the coming of age of the Industrial Internet of Things (IIoT)?

Browse all Technical blog posts