is simplification of ilaplace possible?

조회 수: 6 (최근 30일)
Juan
Juan 2013년 10월 13일
댓글: MINATI 2018년 12월 18일
Hi you all! I must say YES, I'm student, and NO, this is not homework.
Function ilaplace doesn't work in computers of my university, and further I trully doubt my teacher know that it exists. But I like going beyond what I'm suppose to learn, and...
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
― Benjamin Franklin
The function ilaplace gives a soltuion, which is not simplify, I'd thank a solution for this.
For an example code:
% declare tf
s=tf('s');
F_tf=5*(-1+1j)/(s+500j)+5*(-1-1j)/(s-500j);
F_tf=zpk(F_tf)%quick view of poles and zeros
F_tf=tf(F_tf);
num=F_tf.num{1};
den=F_tf.den{1};
% get inverse laplace of transfer function
syms s t % declare syms variables
F_sym=poly2sym(num,s)/poly2sym(den,s)
F_time=ilaplace(F_sym);
pretty(F_time) %another not simplified view
The resault is of class sym:
F_time =
(655360000*4294967296000001^(1/2)*sin((4294967296000001^(1/2)*t)/131072))/4294967296000001 - 10*cos((4294967296000001^(1/2)*t)/131072)
This is what must be simplified. Operating throught Command Window, and no Editor as i wanted, it solves to
f(t)=10*sin(500t)-10*cos(500t)

채택된 답변

Vivek Selvam
Vivek Selvam 2013년 10월 14일
Here the expression is already simplified i.e., it is in the final form of sines and cosines. Since you want to change the fractions to decimal, variable precision arithmetic (vpa) should work!
F_time=ilaplace(F_sym);
F_time=vpa(F_time,2)
pretty(F_time)
  댓글 수: 2
Juan
Juan 2013년 10월 14일
Thanks!!
That was exactly what I was looking for.
MINATI
MINATI 2018년 12월 18일
Can it be possible to draw solution of coupled PDEs with two independent variable x,t
Pl. reply me on minatipatra456@gmail.com

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