Ways to control a process (or equipment)

This is a tricky, ambiguous, question. One may say that a process or equipment can be controlled only in two different ways:

• manually or
• automated.

Since automated control means fully automated, a combination of manual-automated control possibility is  out of question. This also gives origin to two well nown concepts: open loop (lazo abierto) and closed loop (lazo cerrado).

However, the question posed as title of this post goes further. 

How can you implement the manual or automated control of a given process or equipment? 

The shortest answer is a list of options that actually unfolds into further options! There are two well known main categories of control:

• feedback, and
• feedforward.

Now, if you go a little deeper another subcategory is found. These options are:

• On/Off control (control todo o nada)
• PID control
• Robust control (control robusto)
• Fuzzy logic control (control con lógica difusa)
• Artificial inteligence (inteligencia artificial)

with the last 4 applying for closed loop only. A more detailed study of the previous categories will show that there is still another set of sub-sub-categories. These are perhaps the ones being closer to the technical implementation of the control loop. These are:

• cascade control (control en cascada)
• ratio control

From this sort of classification the, novice, engineer or technician may select the features of its control loop and then defining the elements that will make the job. This is in fact an iterative procedure.

Any question? Write in the comments and I shall try to help.

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Ildebrando.