Defining Terms: Systems, Stabity, and Limit Cycles

Pretty good, I think. It's useful to know the control-guy nomenclature for things we learn about in PDE class or in real life. ;)

Cheers

Phil Hobbs

Snap, I meant to watch it... lots to do at work, and limited download at home.

It's not a very exciting title. I don't know what limit cycles are so I'll have to watch it.

George H.

You mean you don't know Lyapunov's second method ?>:-} ...Jim Thompson

Not a clue w/o goolge. I don't know his first method either. :^)

George H.

I'm just yanking your chain... several of my Master's courses were on non-linear control systems... and non-linear differential equations. ...Jim Thompson

Well, you use his first method all the time -- weren't you paying attention?

(I admit to lumping the two together in the video -- the fact that there's two, and that the second is much more grad school than the first, wasn't at all what I wanted to present in that talk).

OK I watched it. I'm a very visual learner, so I'd like lot's of examples, graphs, scribbles on the white board.

Speaking of white, was that a white proto board holding your circuit? (I had resolution set low.. a bit grainy.)

George H.

There's a saying that for every equation you put into your document, your audience drops by a factor of two. I had the same fear of graphs -- I figured I'd have to spend ten minutes explaining what the graphs mean before I could throw them up.

But you just gave me the notion of doing an animated graph, with, for instance, a picture of a pendulum moving along with a graph of its trajectory in state-space. If I showed the present position as a dot (or ball), and the limit cycle's attractor as a black line, you could see the thing approaching the limit cycle.

Yes it was. It's a perfect application for the white proto board -- one, off, sub-audio, low power, and because I'm not sure of the exact properties of the pendulum, it's very handy to tune the thing by parts- swapping.

Hmm OK, perhaps I'm not a typical audience. I don't mind at all some simple equations, (that we've all been taught.. it's a reminder.) V=IR, Q=CV, (What's the simple L equation, V=L*di/dt?) t=RC=L/R

I'd like to see a 'scope display.. or a computer screen.. but I'd want it ~real time. One channel your input, and then the error signal and output? You could make a low freq. Wein bridge oscillator, slowly tweak the gain, and watch it start up.

I have no idea how to make good video's, They shouldn't be like a book, each has to be fun on their own... A video of how you found your intended 1st order was 2nd with a dead zone. I'd assume an intelligent audience, If you need to mention some perhaps new term, and you're going to talk about that in a future video, then just say that.

Yeah that's fine... I posted a pic of mine on some other thread.

George H.

You'd make a good politician..

Jamie

I wish we *had* politicians with a working knowledge of stability.

Corporate executives too, for that matter.

It's not politics, but one of the places you can learn control theory is in economics school. I helped hire my replacement at FLIR; the woman that we hired had gotten started in control theory because she was getting a Bachelor's in economics.

Econ is a disaster area. So good for her.

But, I fear - emphasis on "getting started". And I don't mean that they should make a fetish of stability, either.