How to store a matrix output of a loop?

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Here's my code:
(tryna get the transformation matrices of each link of a robot and save them)
g=zeroes(4); %initial global frame
for j=1:7
theta=q(j);
alpha=al(j);
LinkLength=a(j);
LinkOffset=d(j);
g(j,:) = [cos(theta),-sin(theta)*cos(alpha),sin(theta)*sin(alpha),LinkLength*cos(theta);
sin(theta),cos(theta)*cos(alpha),-cos(theta)*sin(alpha),LinkLength*sin(theta);
0,sin(alpha),cos(alpha),LinkOffset;
0,0,0,1];
end
I need to have 7 matrices corresponding to the transformation of each link like g(1),g(2), ....

Accepted Answer

Walter Roberson
Walter Roberson on 1 Feb 2020
Edited: Walter Roberson on 1 Feb 2020
g=zeroes(4, 4, 7); %initial global frame
for j=1:7
theta=q(j);
alpha=al(j);
LinkLength=a(j);
LinkOffset=d(j);
g(:, :, j) = [cos(theta),-sin(theta)*cos(alpha),sin(theta)*sin(alpha),LinkLength*cos(theta);
sin(theta),cos(theta)*cos(alpha),-cos(theta)*sin(alpha),LinkLength*sin(theta);
0,sin(alpha),cos(alpha),LinkOffset;
0,0,0,1];
end
Now g(:,:,k) will be the k'th matrix.
If you prefer,
g = cell(7, 1); %initial global frame
for j=1:7
theta=q(j);
alpha=al(j);
LinkLength=a(j);
LinkOffset=d(j);
g{j} = [cos(theta),-sin(theta)*cos(alpha),sin(theta)*sin(alpha),LinkLength*cos(theta);
sin(theta),cos(theta)*cos(alpha),-cos(theta)*sin(alpha),LinkLength*sin(theta);
0,sin(alpha),cos(alpha),LinkOffset;
0,0,0,1];
end
and then g{k} would be the k'th matrix.
  1 Comment
azarang asadi
azarang asadi on 2 Feb 2020
first one didn't work but the second one worked, thanks

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