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Fortunately, basic PID analysis, including linear state-space representation and practical tuning methods (e.g. Ziegler-Nichols[1]), is taught in pretty much any first EE control theory course at the undergraduate level.

[1] https://en.wikipedia.org/wiki/Ziegler%E2%80%93Nichols_method

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I took a class in PID and other control systems (PIP) in my 3rd year of undergraduate Electronic Systems Engineering at Lancaster University in the UK.

http://www.research.lancs.ac.uk/portal/en/publications/-(657...

I enjoyed the class and got good grades, but I've never had to use it in practice.

Now I work for a tech company in Taiwan who make microSD cards, and some of the programming projects I worked on involved writing drivers for the testing machines. That was called "automation and control", but it's all been in software.

I like hardware, but I really don't know how to get back into it after 7 years in software.

You need some hardware projects. Designing and building something like a 3d printer or cnc machine from scratch is quite rewarding. Here is a weekend project I did using 3 RC servos and an arduino:

https://www.youtube.com/watch?v=cbNiJKSRCpA

Cool project! I had always thought 3D printers needed steppers for more accuracy (as opposed to servos). Is it the 3 arm config of the 3d printer that makes lower accuracy servos work? Curious where you sourced the hw pieces?

The RC servo project is definitely not accurate enough for printing. It was just a fun project. It would need gears or some other mechanism to get the resolution up there.

Most delta 3D printers use steppers and a linear rail of some sort to gain the required resolution (and height for volume), but I bet you could use BLDC motors in a similar control fashion as used in stabilization gimbals for cameras on hobby drones and similar. I'm not sure if it would be better resolution than micro or continuous "stepping" or not...

I have known people working on control systems for large industrial plants (offshore in the North Sea) and they said they used basic undergraduate level control theory (PID etc.) but that the "control theory" part of any project was probably only a couple of percent of the total size of the project.

Mind you that was a a few years back!

This is true for the most part. The majority of loops out there are still PID. Most mechanical systems are fast, simple and linearizable, and PID is robust and simple to implement. The control law is simple.

Advanced Control techniques like MPC are generally applied on complex plants such as chemical plants. In chemical plants, systems are slow but complex (highly multivariate with many interactions), so more complex optimal control techniques like MPC have a larger payoff. MPC has to solve an numerical optimization problem at every iteration, and requires more computational horsepower (not to mention prior mathematical modeling from step test data).

But even in chemical plants, the local loops are PID (actually, PI... D is rarely used). The MPC layer optimizes an objective function and sends setpoints to local PI loops to carry out control.

Not only that... Classic controls (including PID, Routh-Hurwitz, root-locus, etc) are NOT taught in many graduate PhD controls programs!

Are those topics no longer relevant to today's state of the art research?

It's possible that you're just expected to know them at that point.

Agreed. Many state of the art control strategies nowadays are based on optimization techniques (e.g. Model Predictive Control, MPC, optimizes a convex cost function of the state, setpoint and input to your system over a certain time horizon). This has become a viable control strategy for fast (>1kHz) processes only in the past 15 years, since the optimization can be computationally intensive.

Or be able to derive them. PID was never explicitly taught on my course, but all the theory behind it was.

Research? Largely no, although they crop up now and then in clever ways. They are still very relevant in industry, however.

Those are undergrad courses. PhD should already know those by heart.

Not even for Masters in control programs. It's state space all day!

State-space is less relevant to regulatory and servo control loops (which is the majority of loops out there), and more of interest in advanced control systems.

Of course, in Masters programs, you are already expected to know basic PID control.

Graduate courses that cover PID control tend to focus on intricacies like loop pairing, RGA, etc. PID control is an eminently practical field of study, and has many interesting facets like bump transfers, split range control, etc. There's a lot to learn about PID control that is non-theoretical.

From my experience in O+G and mining processing plant control systems many people that tune loops regularly for a while can basically do it by inspection, with small adjustments after the first pass.

First rule is you will not need any derivative except in a handful of particular cases that are well known/identifiable.

I never had Ziegler-Nichols as part of my Control Systems syllabus. My univ referred Bakshi & Bakshi as primary text book.

Google Books link → https://books.google.co.in/books/about/Control_Systems.html?...

The method is simple and practical enough that--if anything--it would have been covered as part of supplemental lab supervised by a graduate TA after professor lays foundation for PID control in lecture the week prior.

Thanks, I was pretty confused for a moment.

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