How to add gravitational acceleration acting on a mass that is connected to a cylinder in Simscape?

Question

Asmaa Alyat 2015-8-13

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https://ww2.mathworks.cn/matlabcentral/answers/233724-how-to-add-gravitational-acceleration-acting-on-a-mass-that-is-connected-to-a-cylinder-in-simscape

编辑： Hamed Shamsi khani 2022-4-23

My model.jpg

I have a double-acting cylinder connected to a mass at its mechanical port R, and I am adding pressure at end A of the cylinder to extend the piston and hence drop the mass. I want to add a gravitational acceleration acting on the mass as well. I tried to use the ideal force source (to implement F=mg), but it does not seem to work. I have uploaded a screenshot to show what I did. Could you please help me?

Thanks a lot. Asmaa

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Answer 1

Sebastian Castro 2015-8-14

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Your force source approach is the right way to model a weight. Two things I would check:

You should also attach a "Mass" block to the R port of the cylinder. You can use (50/9.81) kg for the mass, I guess.
Check the upper and lower limits/initial displacement/directionality of the cylinder block. Chances are your lower displacement limit is 0 and that small negative displacement is due to the large stiffness of the hard stop representing that contact.

- Sebastian