Simscape Multibody 2G // Change the direction of the axis of a joint primitive

Question

Thomas Pujolle 2017-3-4

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https://ww2.mathworks.cn/matlabcentral/answers/328066-simscape-multibody-2g-change-the-direction-of-the-axis-of-a-joint-primitive

评论： Abdeladim FOUAD 2023-5-25

Hello,

The title says a lot, I found this example here (in section "directing joint axis") that explain how to do it in the 1G, but no idea how to do that in the second generation.

How can I for instance use a prismatic joint and decide that the primitive is along x and not along z ?

Thanks in advance, any tip would help a lot ):

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Answer 1

Sam McDonald 2017-3-7

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https://ww2.mathworks.cn/matlabcentral/answers/328066-simscape-multibody-2g-change-the-direction-of-the-axis-of-a-joint-primitive#answer_257693

The 2nd Generation joint blocks in Simscape Multibody define the primitive along one direction. For example, the Revolute Joint block represents a joint with one rotational degree of freedom along the common Z axis, as mentioned in the documentation:

https://www.mathworks.com/help/physmod/sm/ref/revolutejoint.html

You cannot change the primitive direction of rotation, but you can connect a Rigid Transform to the joint block. This change was made to add more flexibility in defining reference frames between solids and joints. Refer to the following documentation:

https://www.mathworks.com/help/physmod/sm/ref/rigidtransform.html

Here is an example that uses this technique rather than using First Generation blocks:

https://www.mathworks.com/help/physmod/sm/examples/computing-actuator-torques-using-inverse-dynamics.html

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Abdeladim FOUAD 2023-5-25

HI

Could you please provide more clarification related to this topic.

Actually when i try to conncet the rigid transform all the joint turns with that and i get back to the same issue which is the fact that the second joint move in the Z direction and not in the X that i want.

I have seen also that you did provide a link that should discribe the Rigid transform but there is only a picture without explanation.

Could you provide more detailles.

Thanks in advance

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Answer 2

Thomas Pujolle 2017-3-8

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https://ww2.mathworks.cn/matlabcentral/answers/328066-simscape-multibody-2g-change-the-direction-of-the-axis-of-a-joint-primitive#answer_257915

All right good to know, I though it was a bit weird having to add rigid transform in order to match the joints primitive, but it was intended that way I'll take it. Thanks !

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Abdeladim FOUAD 2023-5-25

Hi Thomas i hope you are fine.

Did you solve the problem?

If yes could you please tell me how can we connect the Rigid Transform to the joint block without rotating all the joint and getting back again to the same issue .?

Thanks in advance

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