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Re: your post

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15523] Re: your post
  • From: Paula Chammas <chammas at dbag.bln.daimlerbenz.com>
  • Date: Mon, 18 Jan 1999 23:47:23 -0500
  • References: <199901180804.DAA19895@smc.vnet.net.>
  • Sender: owner-wri-mathgroup at wolfram.com

 Dear All,
 
 
 At the beginning of December I posted a question regarding NDSolve.
 Thanks for all the responses. I managed to solve the problem  using the
 following:
 
 NDSolve[{
 w'[t] == -2 w[t] + Tin[t] - Sign[w[t] - v[t]] 2/3 Fn[t],
 v'[t] == (-v[t] + Sign[w[t] - v[t]] 2/3 Fn[t] )/5, w[0]==0, v[0]==0},
 {w,v}, {t, 0, 10}, MaxSteps->40000, AccuracyGoal->2}
 
 given
 
 Tin[t] := -2 t + 12 /; (5 <= t && t <= 6)
 Tin[t] := 2 /; (0 <= t && t
 <=5)
 Tin[t] := 0 /; (6 <= t && t <= 10)
 
 Fn[t] := 0.785 t /; (0 <= t && t <=
 2)
 Fn[t] := 1.57 /; (2 <= t && t <=5)
 Fn[t] := -0.785 t + 5.495 /; (5 <= t && t <= 7)
 Fn[t] := 0 /; (7 <= t && t <= 10)
 
 Now the system becomes more involved.
 
 The new system look like the following: 2 clutches C1 and C2 in parallel
 
 
    w    T1,C1   v
Tin -------||-----  Tout
----m    T2,C2   n------
    -------||-----
 
 
 Tin is input torque, it is given (see below) and Tin = T1 + T2
 
 w, m are input speeds
 v,n are ouput speeds
 
 So basically we have 2 sets of equations one for C1 and one for C2:
 
 w'[t] == -2 w[t] + T1[t] - Sign[w[t] - v[t]] 2/3 Fn[t],
 v'[t] == ( -v[t]+ Sign[w[t] - v[t]] 2/3 Fn[t] )/5,
 
 m'[t] == -2 m[t] + T2[t] - Sign[m[t] - n[t]] Fn[t],
 n'[t] == ( -n[t] + Sign[m[t] - n[t]]  Fn[t] )/5
 
 with the following constraints:
 
 Tin[t] = T1[t] + T2[t]
 w[t] = m[t]
 v[t] = n[t]
 v[0] = w[0] = m[0] = n[0] = 0
 {t, 0, 10}
 
 Fn[t], and Tin[t] are given above.
 
 T1 and T2 should be determined by the system
 
 When I try to solve the system it does not like the equation
 
 Tin[t] = T1[t] + T2[t]
 
 I get :
 Input is not an ordinary differential equation of T1[t]
 
 and in some cases
 
 NDSolve:: ndsv: Cannot find a starting point of t
 
 What is the best way of formulating the problem using mathematica?
 
 Any ideas?
 
 Thanks in advance and a happy New year to all.
 
 Paula
 
 _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
                      Paula Chammas
 DaimlerChrysler
 Research and Technology                  !!NEW Alt-Moabit 96A
 Tel: +49 30 39982 376 10559 Berlin             fax: +49 30 39982 107
 
 paula.chammas at daimlerchrysler.com
 _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/ 
Experience is a hard  teacher because she gives the test first, the lesson afterward.


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