Closed link Mechanism constrained by springs

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Thura
Posts: 2
Joined: 13 Jul 2018, 18:27

Closed link Mechanism constrained by springs

Post by Thura » 01 Aug 2018, 17:04

Hello everyone

I am trying to build a simple mechanism that consists of parallel link closed by two plates, the bottom plate and the top.
On either sides of the mechanism, a spring is used to constraint the structure and give it damping property. Two motors on top will pull on the springs to control the angle of deflection of the structure and the stiffness of bending.

Here is the image: https://drive.google.com/open?id=1LCCfD ... -Up6ChzsEr


I used the dummies to close the link of the structure, It seems to work but now I am having problems connecting the side springs to the structure as well as how to implement the motor-pulling mechanism. I've been struggling to try to solve it for many days now, Please help me in this case, What should I do to attach the springs and how can I implement the pulling mechanism?
(even when the structure is without the side springs, it wobbles as if there are springs on either side)

Here is my scene
https://drive.google.com/open?id=1ghWN9 ... tPBsIdNSSC

Thank you

coppelia
Site Admin
Posts: 6867
Joined: 14 Dec 2012, 00:25

Re: Closed link Mechanism constrained by springs

Post by coppelia » 03 Aug 2018, 06:10

Hello,

at first view it looks fine, I would have built it in a similar way. You now also need to take care that your mechanism is not overconstrained. Have a look at this planar example.
I would also first design the mechanism with disabled spring/dampers (i.e. free prismatic joints). Once that behaves as expected, adjust the spring/damping.
Finally, make sure that masses and inertias are correctly dimensioned (i.e. mainly design considerations 7 & 8)

Cheers

Thura
Posts: 2
Joined: 13 Jul 2018, 18:27

Re: Closed link Mechanism constrained by springs

Post by Thura » 04 Aug 2018, 14:26

Oh thank you Coppelia, this really give me new insights. I didn't really pay much attention to the mass or moment of inertia of each shapes when I grouped them together. I will reconstruct the mechanism again this time with attention to each shape and the constraining.

Thank you.

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