What is the difference between digital controls and digital control systems?

[timthereaper]

"Digital" Control Systems

I recently took a control theory class at my local university and we learned about PID, loopshaping, and state-space methods and implemented them in MATLAB/Simulink and used an Arduino for some projects. However, I was talking with some EEs (I'm an ME) and they were mentioning a "digital controls" class. Is there a difference between "digital controls" and what I was doing? I figured since we weren't doing things with analog components directly, I was doing digital control systems. Am I wrong?

 

[analogdesign]

You're not wrong. What separates "digital" control theory from standard or "analog" control theory is that in digital control theory the system is quantized. This means you have to use the z-transform instead of the Laplace transform and there are some subtle stability gotchas due to the mapping from the continuous-time Laplace domain to the discrete Z domain. There are some differences mathematically and theoretically but in most practical cases the difference isn't much.

For the most part as long as you sample the appropriate signals fast enough you won't run into trouble but if things get weird it can be helpful to remember you're in a discrete-time domain.

 

[timthereaper]

Okay. That's good to know. We did have to use the Z-transform, so I guess I was doing digital all along. It's just weird because they mentioned it as if what I was doing was different.