In the world of Industrial Controls, the traditional platform has been the PLC. This control was initially the by-product of decades of hard wired automation based on relay logic. The rules were fairly simple, everything got broken down to “on” and “off” contacts, but with the creation of an electronic platform that solved the logic at higher speed and with greater complexity, you could create lots of sophisticated systems from some fairly simple building blocks. The real motivation here is to use a common language to communicate how things work that maintenance people can be comfortable with. Since plant floor electrical maintenance people were generally familiar with ladder logic, the programming language of the PLC was pretty much decided.
Not that other ideas weren’t tried. I remember Boolean programming and some other variants that were attempted due to the variety of solutions being offered by competing vendors. Some of the early PLC’s involved some very exotic variants such as programs that executed software in strict line-by-line form as part of the control system strategy to insure precise, repeatable execution. Larger systems with 1000′s of I/O points simply relied on centralized execution and the controllers focused on increasing speed to manage system behavior. The common metric was so many thousands of lines of code per millisecond of execution time.
Where does all this go when the cost has fallen to a $.50 chip of FPGA logic and an OEM editor that you can license for $5 a copy from one of the major suppliers of ladder editors? As a marketing proposition, it’s hard to differentiate a highly technical production like a controller when there are 20 or 30 brand of mature products to choose from. This is made more difficult when the system pricing varies from $300 to $3000 for what could be argued is the same thing. If the assumptions about the commodity level product are correct, then where is all this headed.
When evaluating controls, the dominant cost is generally not the processor, it’s the I/O system. There certain applications where there are specific I/O considerations such as platinum RTDs or specific alloy thermocouples which cannot be avoided. In these cases, the supplier with the best product wins, pricing may be a secondary consideration. With regard to general purpose I/O products, ac and dc discrete inputs and outputs, lowest cost combined with highest density will be the most effective. So if the system requirement is relatively simple, direct hardware cost will be a significant drive to best overall cost. Where more complex I/O are required, careful examination of the specialty components will be the key differentiator.
Given the tendency of the market to gravitate to the lowest cost, the technology curve for machine control suggests that there are some very large bumps in the road ahead. Let’s hope the “unseen hand” of the free market prevails and some really cool new control solutions break out into the real world.
Filed Under: Mechatronic Tips, Mechatronics
