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Re: OutputResponse gives funny results

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128512] Re: OutputResponse gives funny results
  • From: richard i pelletier <bitbucket at comcast.net>
  • Date: Thu, 25 Oct 2012 23:35:47 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • Delivered-to: l-mathgroup@wolfram.com
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  • References: <k62nr9$cg9$1@smc.vnet.net>

In article <k62nr9$cg9$1 at smc.vnet.net>,
 "Eduardo M. A. M.Mendes" <emammendes at gmail.com> wrote:

> Tcl[p_,Kp_,Kd_,Ki_]=TransferFunctionModel[(Ki+Kp s+Kd s^2)/(Ki+Kp s+Kd
> s^2+p^2 s^2+2 p s^3+s^4),s]
> 
> fcl[t_,p_,Kp_,Kd_,Ki_]=Abs[OutputResponse[Tcl[p,Kp,Kd,Ki],UnitStep[t],t]];
> 
> Manipulate[{N[TransferFunctionPoles[Tcl[p,6,4,1]],2],Plot[fcl[t,p,6,4,1],{t,
> 0,Ts},PlotRange->All,AxesLabel->{t,x[t]},PlotStyle->Thickness[0.01],GridLine
> s->Automatic]},Style["Example 4.4 - Dorf - 12^th Edition - R(s) = 10/s, D(s)
> =
> 0",Bold],{{p,2},0,100,Appearance->"Labeled"},{{Ts,20},0.1,100,Appearance->"L
> abeled"}]
> 
> Even though the poles are on the left side (stable system), OutResponse
> gives huge numbers (instability) when the slider for the variable Ts is
> moved to higher values.  More than, it is seems that this simple code makes
> Mathematica ever so slow.
> 
as I just posted in response to your comment on my blog, the problem is 
with Output Response ­ i don't know why... Simplify didn't seem to help 
­ but if i compute and plot the inverse Laplace transform (for a unit 
step input), everything looks fine.

rip

-- 
email address is r i p 1 AT c o m c a s t DOT n e t



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