Simulink Product Block Dimension Issue.
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Hi everyone,
I have created a simulink model (shown below) to determine robot joint velocities (
) for given robot end-effector velocities (
) by using the following relation: ![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764036/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764026/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764031/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764036/image.png)
The pseudo-inverse of the jacobian
(called Jpinv in the model) is fed to a product block to be post-multiplied with the joint velocities (called pdot) to produce the end-effector velocites (called qdot).
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764041/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764046/image.png)
However I get the following error messages:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/764051/image.png)
Why doesn't the Product block recognize the dimensions of the Jpinv matrix? Because Simulink states [7x6] at the exit of the Function block and then suddenly loses this information when it enters at the Product block? And from Linear Algebra I know that a [7x6] matrix times a [6x1] vector should yield a [7x1] matrix of joint velocities qdot.
Does anybody know how I can fix this issue to get the correct multiplication result?
Thanks in advance,
Mike
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Accepted Answer
Jonas
on 11 Oct 2021
You need to set the 'Multiplication' option of your Product block to 'Matrix(*)'.
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More Answers (1)
Luca
on 8 Nov 2021
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/794219/image.jpeg)
What blocks do you need to visualize the product of a pressure for a surface and obtain a force?
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