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MathGroup Archive 1998

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NDSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15118] NDSolve
  • From: Paula Chammas <chammas at dbag.bln.daimlerbenz.com>
  • Date: Sat, 12 Dec 1998 03:59:16 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

Dear all,

I am having a problem with NDSolve.

I am trying to solve the following problem:

Tin[t_] := - 2 t + 12   /;  t >= 5 && t  <= 6 Tin[t_] :=  2    /;  t >=
0 && t  <= 5 Tin[t_] := 0   /;  t >= 6 && t  <= 10

Fn[t_] :=  0.785 t  /; t >= 0 && t  <= 2 Fn[t_] :=  1.57 t  /; t >= 2 &&
t  <= 5 Fn[t_] :=  0.785 t  + 5.495 /; t >= 5 && t  <= 7 Fn[t_] :=  0  
/; t >= 7 && t  <= 10

If [ (w[t] ! = v[t]) && ( ( (5/6) Tin[t] - (9/6) w[t]  ) > Fn[t] ),
NDSolve[
                  { w'[t] + 2 w[t] - Tin[t] + Sign[ w[t] - v[t] ] (2/3)
Fn[t] == 0,
                      5 v'[t]  + v[t] -    Sign[ w[t] - v[t] ] (2/3)
Fn[t] == 0,
                      w[0] == 0, v[0] ==0, {w, v}, {t, 0, 10}
                   ],
NDSolve [
                   { 6 w'[t] -Tin[t] - 3w[t] == 0, w[0] ==0, w, {t, 0,
10 }
 ]

There is a discontinuity at about t =4.08--that is when w[t] = v[t] and
when the switching  should happen. I am having problems imposing the
constraints!

Any ideas?

Thanks
Cheers
Paula

--------------------------------------
                    Paula Chammas
DaimlerChrysler
Research and Technology
Alt-Moabit 96A           Tel: +49 30 39982 219 10559 Berlin            
fax: +49 30 39982 107

paula.chammas at daimlerchrysler.com
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ Worry is like a rocking
chair - it gives you something to do but it doesn't get you anywhere.
-Dorothy Galyean
---------------------------------------



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