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In his biography of Steve Jobs, Walter Isaacson describes one of the major strategic battles of the personal computer business. Interestingly, this battle is repeating itself in the smart phone industry today. Jobs strongly believed in thoroughly and tightly integrated hardware and software. Apple does not license its operating system and exerts very tight control over its hardware and software. Bill Gates believed in the opposite approach and licensed Microsoft software to multiple hardware manufacturers. Google is doing this today for its Android operating system.
The Apple approach has been described as a “walled garden” where devices and software inside the garden are inherently integrated because there is only one gardener. Walled garden proponents argue the advantages of ease of use, safety and security. The open field approach is just that, where devices and software come from multiple manufacturers and integration is achieved either through standards or custom work. Open field proponents argue the advantages of best of breed and lower cost.
This same battle has been going on for decades in the automation world. It is at the heart of the issues surrounding fieldbus protocols, wireless protocols and plant-wide networks. Does our industry have anything to learn from these other industries?
In the early days of distributed control systems (DCSs) and programmable logic controllers (PLCs), these control systems were walled gardens. Input/output modules, controllers, operating and engineering stations, and the control highway were all provided by one manufacturer.
These systems received analog and discrete inputs which were very well standardized. The field devices were dumb and didn’t get into the act. The advent of smart field devices with digital communication blurred the walls. The introduction of commercial technology into the DCS/PLC stirred the pot even more.
There is thoughtful debate over the best approach to automation in a fully digital world. Some argue for moving the walls out to include everything; others argue for the complete demolition of all walls. These debates impact the standards efforts and the choices made by both manufacturers and end users.
Openness led to chaos
I have an opinion. First, a DCS/PLC should return to a walled garden. The drive to openness has gone too far. A DCS/PLC is, after all, the thing that controls the operation. Do we really want control to be so open that automation starts to look like the Windows PC world? I recently replaced an older Windows PC with a new one. Microsoft, Dell and Adobe all tried to grab hold of my photos and organize them for me. The openness led to chaos and a control system is no place for chaos.
Second, each field device must also be a walled garden. A single manufacturer is the best one to engineer the complex relationship between a sensor or actuator and the electronics/software that make them work.
Third, the digital connection between the field devices and the control system should be an open field governed by communication standards. These standards should stick with communication only, and not get into what goes on inside the control system or the field devices. The wonderful USB is a great example of this. It enables different devices to connect and transmit, but it stops short of trying to tell the printer how to be a printer.
So, my view is that control systems and field devices should be walled gardens with open communication between them. I recognize that there are other opinions and invite you to share them with me and each other. By the way, I moved my photos to an Apple.
Open vs “Black Box” Discussion: What do you prefer? Weigh in on the open versus closed discussion on Automation World’s LinkedIn group page. Visit http://linkd.in/AguYWS
John Berra, [email protected], recently retired as Chairman of Emerson Process Management.
