Why I do not see the correct transfer function

I am trying to build a feedback system and use the connect() function to build it. But some how I can not get the correct transfer function. Here is my code:

G1 = tf([1,[1,0]]); G2 = tf(1,[1 1 0]); G3 = tf(1,[1,1,0]);
G4 = tf(-2, 1); G5 = tf(-1,1); G6 = tf(1,[1,0]);
G7 = tf(-1,[1,1]);

Sys = append(G1,G2,G3,G4,G5,G6,G7);

Q = [1 6 5; 2 1 7; 3 2 0; 4 3 0; 5 4 0; 6 2 0; 7 3 0];

INPUTS = 1;
OUTPUTS = 4;

G = connect(Sys, Q, INPUTS, OUTPUTS);

tf(G)

Here is my error:

Warning: The closed-loop model may be improper because of singular algebraic loops. 

ans =

0

Static gain.

Please help

Answer 1

[Paul]

Hi Zeyuan,

Is G1 defined correctly? If it is, or if stil having trouble after correcting it, it would be easier to help with a block diagram drawing of the system to be modeled. You can upload a figure using the paperclip icon on the Insert menu if needed.

G1 = tf([1,[1,0]]), G2 = tf(1,[1 1 0]); G3 = tf(1,[1,1,0]);

G1 =
 
  From input 1 to output:
  1
 
  From input 2 to output:
  1
 
  From input 3 to output:
  0
 
Static gain.

G4 = tf(-2, 1); G5 = tf(-1,1); G6 = tf(1,[1,0]);
G7 = tf(-1,[1,1]);
Sys = append(G1,G2,G3,G4,G5,G6,G7);
Q = [1 6 5; 2 1 7; 3 2 0; 4 3 0; 5 4 0; 6 2 0; 7 3 0];
INPUTS = 1;
OUTPUTS = 4;
G = connect(Sys, Q, INPUTS, OUTPUTS);

Warning: The closed-loop model may be improper because of singular algebraic loops.

Answer 2

[Jasper Gerritsen]

You probably meant to write

G1 = tf(1,[1,0]);

But there is no way to tell unless you specify to us what you intended to do.