how to create a variable without assigning a value to it and also the variables shouldnt be symbolic variables

syms e d 
m= [27.5084  -10.7668   -9.7727;-20.6533   15.8060   14.8502];
k1=[27.5084*e  -10.7668*e   -9.7727*e;-20.6533*e   15.8060*e   14.8502*e];
g11=tf([27.5084],[1 0])
g12=tf([ -10.7668],[1 0])
g13=tf([-9.7727],[1 0])
g21=tf([ -20.6533],[1 0])
g22=tf([15.8060],[1 0])
g23=tf([14.8502],[1 0])
k2=[g11 g12 g13;g21 g22 g23]
k3=k2*d

i want the matrix k3 in terms of variable 'd' so i can optimize the matrix with respect to the variable 'd' but that is not happening as d is a sym variable

and also unable to perform any kind of command on k1 as it has sym variable , is there any way to rectify this

Answer 1

[Walter Roberson]

syms e d 
m = [27.5084  -10.7668   -9.7727;-20.6533   15.8060   14.8502];
k1 = m * e;  %not used
k2c = arrayfun(@(V) tf(V,[1 0]), m, 'uniform', false);
k2 = [k2c{1,:}; k2c{2,:}]

k2 =
 
  From input 1 to output...
       27.51
   1:  -----
         s
 
       -20.65
   2:  ------
         s
 
  From input 2 to output...
       -10.77
   1:  ------
         s
 
       15.81
   2:  -----
         s
 
  From input 3 to output...
       -9.773
   1:  ------
         s
 
       14.85
   2:  -----
         s
 
Continuous-time transfer function.

syms S
K2N = cellfun(@(V) poly2sym(V,S), k2.Num)

K2N = 

K2D = cellfun(@(V) poly2sym(V,S), k2.Den)

K2D = 

k3 = K2N./K2D * d

k3 = 

This is symbolic, so you can start manipulating it, and can start optimizing.

[bhanu kiran vandrangi]

thank you

can i use ilaplace on K3 (s to t) keeping d as it is

[Walter Roberson]

syms e d 
m = [27.5084  -10.7668   -9.7727;-20.6533   15.8060   14.8502];
k1 = m * e;  %not used
k2c = arrayfun(@(V) tf(V,[1 0]), m, 'uniform', false);
k2 = [k2c{1,:}; k2c{2,:}]

k2 =
 
  From input 1 to output...
       27.51
   1:  -----
         s
 
       -20.65
   2:  ------
         s
 
  From input 2 to output...
       -10.77
   1:  ------
         s
 
       15.81
   2:  -----
         s
 
  From input 3 to output...
       -9.773
   1:  ------
         s
 
       14.85
   2:  -----
         s
 
Continuous-time transfer function.

syms S t
K2N = cellfun(@(V) poly2sym(V,S), k2.Num)

K2N = 

K2D = cellfun(@(V) poly2sym(V,S), k2.Den)

K2D = 

k3 = K2N./K2D * d

k3 = 

ik3 = ilaplace(k3, S, t)

ik3 = 

[bhanu kiran vandrangi]

clc

syms e d

m = [27.5084 -10.7668 -9.7727;-20.6533 15.8060 14.8502];

k1 = m * e;

k2c = arrayfun(@(V) tf(V,[1 0]), m, 'uniform', false);

k2 = [k2c{1,:}; k2c{2,:}]

syms S t

K2N = cellfun(@(V) poly2sym(V,S), k2.Num)

K2D = cellfun(@(V) poly2sym(V,S), k2.Den)

k3 = K2N./K2D * d

K=k1+k3

GP=tfmatrix

CON=K*GP

% where GP is =

GP =

From input 1 to output...

0.005659 s^2 + 0.05206 s + 0.004496

1: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

0.003013

2: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

0.0006678 s + 0.003046

3: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

From input 2 to output...

0.003013

1: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

0.005659 s^2 + 0.02714 s + 0.004051

2: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

0.02554 s + 0.004018

3: -----------------------------------

s^3 + 9.357 s^2 + 2.228 s + 0.06147

i am getting a error while executing 'CON' in matlab as mentined above CON=K*GP

how to get past this error