Why does this matrix multiplication work?
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Hi,
I had a look at the Simmechanics Demo mech_bouncing_ball.mdl because I want to find out how to model ground.
In the subsystem that calculates the force that acts on the ball when hitting the floor is a matrix multiplication.
It is calculated with a Gain-Block. The input is a 1x3 Matrix, the Gain Parameter is [0 0 0;0 0 0;0 0 -ball.pengain] and the output is again a 1x3 matrix. The Setting of the calculation is "Matrix(K*u)". The Help says: "The input and gain are matrix multiplied with the input as the second operand."
I dont't understand how this works. How is it possible that a 3x3 matrix is multiplied with a 1x3 matrix? When I try that in the comand window it says that "Inner matrix dimensions must agree." Why does it work with the Gain Block?
Would be great if someone could help me. I really don't understand that. Thank you very much!
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回答 (1 件)
David Sanchez
2013 年 6 月 11 日
What's wrong with it?
a=rand(1,3);
b=rand(3,3);
c=a*b;
3 件のコメント
Iain
2013 年 6 月 11 日
Its using the vector, as a column. eg
A = [0 1 0; 1 0 0; 0 0 1];
B = [2 3 4];
C = A*B';
C = [3; 2; 4]
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