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Comment by belzebalex | Hacker News Reader

One method that solves 99% of your control problems is the Ziegler-Nichols method [1]. It's a shame it's not taught more often.

No need to model your system, just increase the P gain until the system oscillates naturally. Measure the oscillation period, and then refer to the tables at [1] to choose the P, I, D gains depending on how you like your system response to look like.

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

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ZN tuning is taught in engineering schools in the US. I even had a lab on it. As far as I remember it was kind of painful to work through and didn’t yield that much better results than hand tuning.

Ah I remembered something else… it needs to find the max Kp which in some cases is just not possible (or wise) to attempt with a real world plant.

On the contrary, ZN is taught is almost every undergrad control course — and not actually used industry. It’s a classic textbook method to demonstrate the concept in simulations but it has many downsides in practice (pushing the system to its boundaries is not a good idea).

Most professionals tune with starting values obtained using model inversion (IMC, direct synthesis) and then hand tune. There is also software like Loop Pro that analyzes the data and proposes tunings.

You can actually use that method for the remainder constants too. I built an analog motor controller for my control systems lab and the constants were just pots. We would increase the resistance until instability and back off a little. Rinse and repeated for the remainder two pots.

A lot of gaming doesn't really have the luxury of waiting for the oscillation to kick in, in order to then balance the system, though. By the time there's oscillation, it's already too late to fix, you need to preempt the oscillation.

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