OutputResponse gives funny results

*To*: mathgroup at smc.vnet.net*Subject*: [mg128463] OutputResponse gives funny results*From*: "Eduardo M. A. M.Mendes" <emammendes at gmail.com>*Date*: Mon, 22 Oct 2012 02:03:12 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hello I am trying to implement some examples on Dorf's book. Here is a code for one of them. 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. Have I missed something? Many thanks Ed