Why I cannot get a solution for this system?

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Traian Preda
Traian Preda on 1 Nov 2013
Answered: Alex Sha on 10 Dec 2019
Hi,
I have the following system of equations for which I have an initial guess. But I cannot get any solution. Anyone can help?
syms Lfd R1d L1d L1q Ladssec Laqssec Rfd R1q
S=vpasolve([(-(1*Rfd*((1/((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1))))*((0.072+1*(Laqssec+0.1))*sin(-0.785)-(0.005+0.009)*cos(-0.785)))*Ladssec)/(Lfd))==0.0023 ,(-(1*Rfd*(1-(Ladssec/Lfd)+((((0.072+1*(Laqssec+0.1))*Ladssec)/(((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1)))*Lfd)) *Ladssec)))/(Lfd))==-0.0054,(-(1*Rfd*(-(Ladssec/Lfd)+((((0.072+1*(Laqssec+0.1))*Ladssec)/(((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1)))*L1d)) *Ladssec)))/(Lfd))== 0.0018,(-(1*Rfd*(-((0.005+0.009)/((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1))))*(Laqssec/L1q))*Ladssec)/(Lfd))==5.8369e-04,(-(1*R1d*((1/((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1))))*((0.072+1*(Laqssec+0.1))*sin(-0.785)-(0.005+0.009)*cos(-0.785)))*Ladssec)/(L1d))==0.1303,(-(1*R1d*(-(Ladssec/Lfd)+((((0.072+1*(Laqssec+0.1))*Ladssec)/(((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1)))*Lfd))*Ladssec)))/(L1d))==0.1157,(-(1*R1q*((1/((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1))))*((0.005+0.009)*sin(-0.785)+(0.072+1*(Ladssec+0.1))*cos(-0.785))) *Laqssec)/(L1q))==-0.1323,(-(1*R1q*(((0.005+0.009)/((0.005+0.009)^2+(0.072+1*(Ladssec+0.1))*(0.072+1*(Laqssec+0.1))))*(Ladssec/Lfd))*Laqssec)/(L1q))==-0.0044],[Lfd, R1d, L1d, L1q, Ladssec, Laqssec, Rfd, R1q],[0.233, 0.0848, 0.2, -0.09, 0.099, -0.1, 0.00173, 0.0129])
  1 Comment
Matt J
Matt J on 1 Nov 2013
I'm pessimistic that anyone can help. Assuming you have no bugs, we can't know why a solution should exist to such a complicated system. If you do have a bug, we cannot know what equations you really intend.

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Answers (1)

Alex Sha
Alex Sha on 10 Dec 2019
A set of approximate solutions:
lfd: 0.273760301072663
r1d: 0.0994325019367128
l1d: 0.236671205261253
l1q: 0.077183609924249
ladssec: 0.134215496801333
laqssec: 12.088089943567
rfd: 0.00203860423799885
r1q: 0.0153424199630846

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