Salvador Dali had a unique perspective of time. Not sure if I understood his message, or if anyone else did for that matter. Nevertheless, time has an all-important meaning to the world of control.
In particular, it is our recent ability to subdivide time to smaller and smaller intervals in modern control systems that is of interest and which has the most important implications for control systems of the future.
In the early days of industrial manufacturing, the interval of time was whatever we could manage with the timing of escapement mechanisms and gears based on the incoming power takeoff shaft. If the factory was water powered, as much of the UK and New England area of the US were, then large water wheels at low RPM had to be converted to higher speed power take off shafts running along the ceiling. Each individual machine would be connected via a leather belt, and the speed of the shaft adjusted with pulleys to achieve the desired operating speed of the process. I would guess that things done in seconds or maybe tenths of seconds would be the limit of resolution of these systems.
With the advent of electrically operated controls based on relays the resolution of time became quicker, probably 20 to 50 milliseconds, the amount of time required for the relay to become energized. If a few relays did not perform to specification, it would lead to “relay races” where unstable circuit timing had to be diagnosed. This turned out to be a very difficult issue as control systems became progressively more complex.
After the birth of the semiconductor the controls industry went through a massive transformation where control at speeds of 1 millisecond or faster became standard. Industrial control systems were all programmed using a software editor to create a program on a CRT screen (for those don’t remember real television) for download to the processor. These systems were “hardened” against errors making them unique hardware platforms compared to the early computers of the 1960 through to the recent past.
While the industrial controls community may not have been paying particular attention to the march of Moore’s Law in the semiconductor field, the last few years have been witness to an increase in speed of more than 1000 times in processor throughput while costs continue to fall. The electrical hardware being manufactured today is tested to microseconds and even nanoseconds of accuracy in the case of special high speed equipment used in the scientific arena. Memory systems are being scaled in Terabytes and Gigabaud communications are the standards of today’s hardware.
Let’s explore this some more in the next post.