Comments on: Flexible Bodies in SimMechanics https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/?s_tid=feedtopost Guy Rouleau is an Application Engineer for MathWorks. He writes here about Simulink and other MathWorks tools used in Model-Based Design. Mon, 10 Sep 2018 12:45:21 +0000 hourly 1 https://wordpress.org/?v=6.2.2 By: Yiqing Meng https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-226777 Mon, 10 Sep 2018 12:45:21 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-226777 @Jerry S Hi, I’m also doing some investigation on caternary shape cable. Could you please guide me how to define the damping rate and spring stiffness for the cable? In addition, how did you define the two sides of cable ? Are they just connected to the same ‘world frame’ block ?

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By: 福来 刘 https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-219436 Sat, 31 Mar 2018 13:02:40 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-219436 About how to define K and C parameters, I think you can assume one end of beam is fixed, and one end is free, then add a force F to the free end, calculate the free end displacement of rigid elements connection model and real model(with E and I), and let them be equal, then you can get a value of K.

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By: Pedram https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-211310 Fri, 16 Jun 2017 18:32:19 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-211310 Hi Guy,
Thanks for your example, it was really great and helped me a lot. I am modeling a flexible link in 2nd gen but I have problems with K and C parameters and I couldn’t find the right number of them, I searched the relation between Elasticity and stiffness ( K ) in web and I found these two ( E.I /L and E.A /L ) I tried them both and they didn’t answer. I wanna know how you define these numbers. ( K & C =????? )

Regards,

Pedram

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By: Bruno https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-146350 Thu, 05 Nov 2015 15:25:51 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-146350 Hi, thx for this example. I’m pretty new on SM and I find this really interesting.
I was looking at the code and I couldn’t find the parameter initialization for K,C,Lw and d.
Could you please lead me on the path?

thx a lot,

Bruno.

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By: Etienne https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-126316 Mon, 01 Jun 2015 15:37:10 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-126316 Hi Guy

Have you tried to build a flexible component with a state space block, similar to the paper and examples from the first generation? I have tried to do this with the second generation, but cannot get the beam example to work.

Regards

Etienne

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By: Anton B. https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-119000 Sat, 04 Apr 2015 21:03:36 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-119000 @ Jerry :

Sorry to “renew” the old thread, but

I think, a good work-around could be the application of the gravity as a function of time over a short period, so that your computations do not last for too long. This approach is very popular in mechanical / geomechanical modelling, when one does not want to see numerical high frequencies , arising from the fact, that gravity is suddenly applied as a step at the initial phase of the numerical model.

Anton.

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By: Jerry S https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-70091 Fri, 27 Jun 2014 20:51:53 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-70091 I am working on a model similar to the one I described earlier, but without the sliding mass. I have a fixed mass in the middle of the cable. Before the simulation begins, SimMechanics determines the initial conditions of the joints throughout the simulated flexible cable. Then, as gravity takes effect, the cable oscillates. I would like the initial conditions to be such that there is no motion unless I apply an external force. Then, I would be able to apply a force to the mass and observe the reaction in the cable. Is there a way to execute an optimization function for the initial conditions for the cable/mass system, so that there is no motion (due to gravity) after the simulation begins?

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By: Guy Rouleau https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-69217 Mon, 16 Jun 2014 19:14:25 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-69217 @ Jerry: Thanks for the comment, this is a very interesting application. This type of “point-on-flexible-curve” problem is very challenging. the current version of SimMechanics either first or second generation cannot directly simulate this system.

To make that happen, you will need to go through Simulink and compute the force relation between the cable and sliding mass, to finally apply the resulting force to the appropriate element of the cable.

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By: Jerry S https://blogs.mathworks.com/simulink/2014/05/22/flexible-bodies-in-simmechanics/#comment-68974 Thu, 12 Jun 2014 17:08:31 +0000 https://blogs.mathworks.com/seth/?p=3668#comment-68974 I’m attempting to model a cable hanging between two points of different heights in SimMechanics (2nd generation), and this Flexible Beam example has been very helpful so far. In the simulation, the cable forms a catenary as expected. However, the physical system I’m attempting to model will also have a hanging mass sliding down that cable. I can’t figure out how to model the interaction between such a mass and the cable. Right now, I have the mass connected to a 6-DOF joint connected to the World Frame. The mass is initially positioned at the high side of the cable. After the simulation starts, gravity causes the mass to drop through the cable. Any ideas? Would it be easier to try this in First Generation SimMechanics?

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