Talk:State space (controls)

From Wikipedia, the free encyclopedia

Contents 1 Small error in the transfer function derivation 2 What else does this article need? 3 Section blanking 4 Feedback with reference input

[edit] Small error in the transfer function derivation

The Laplace transform of x'(t) is not sX(s), but sX(s)-x(0). I believe that the initial conditions term is usually assumed to be zero anyhow, to indicate no initial energy. I'm new to both controls and editing wikipedia, so I'll leave the actual editing to someone better equipped. :)

—The preceding unsigned comment was added by 70.171.42.102 (talk) 06:15, 21 March 2007 (UTC).

[edit] What else does this article need?

Definitely some diagrams of the systems.

I think another article on equilibrium is needed (phase diagrams, stabile points, unstable points, etc.). Cburnett 19:06, 13 Dec 2004 (UTC)

Also, state feedback was left out of the feedback section... might be good to include those tidbits. not a far stretch from what is already there, but it is entirely neglected.

Formulas to determine state-space represetnation of interconected systems:

• parallel connection

  +--|S1|--+
  |        v
--+--|S2|--+--

• serial connection

-->--|S1|--|S2|-->-

• feedback connection

--+--|S1|--+--
  ^        |
  +<-|S2|--+

Where both S1 and S2 are given in state space representation.

---

I'm trying to learn some of the math from this article, so if I don't know what I'm talking about, that's why. That being said, I think there is some sort of error in the description of variables in the Moving Object Example. In the second breakout "acceleration of the objection" it explains a variable not used in the equation.

[edit] Section blanking

An anonymous user blanked content back in July 2006. [1]. I reverted and attempted to restore edits made since then. Sorry if I missed some, but the amount deleted was wholly worth any loss since then. :/ Cburnett 01:10, 22 November 2006 (UTC)

I don't know if you want to restore more, so I prefer to ask you first. Section "State variables" is neither correct nor self-consistent, imo. State variables can be redundant (dependent); a state-space model with the number of state variables is a minimal realization, which is a special (yet important) case. One should define "realization" first, noting that it isn't unique (see some of my previous contributions). "System variables" aren't defined (I'd just write "values" instead). In "linearly independent", linearly is superfluous, because linearity isn't required here. Finally, in "the minimum number of state variables is equal to the transfer function's denominator", it's equal to the denominator's degree, not to the denominator itself. Engelec 11:42, 22 November 2006 (UTC)

[edit] Feedback with reference input

If r(t) is the reference input, or setpoint, the correct equation for u(t) is u(t) = K(r(t) − y(t)) (compare to other articles on control, e.g. PID controller). D is usually not left out just for the sake of simplification, but because it is zero in strictly causal systems. Engelec 10:03, 14 December 2006 (UTC)