Simulink Disc Rotation (Pendulum movement)

[JPGraphX]

Hi,

First, I want to thanks all of you for helping (especially Fex32). I'm doing another post because my english is bad and I want to "try" to be a bit more precise. So here's what I want to do; I want to model on Matlab Simulink the rotation of a disc around a shaft. That disc when at initial position can rotate 90 degrees clockwise and ccw. When you "crank" it to 90 degrees and release it, it does a pendulum movement, until it stops.

Here is a top view of my disc (in black are the rubber bands)

On my second picture we can see the type of curve (chart?) I want to obtain:

When rotating the disc, the rubber bands stretches and the inertia momentum isn't constant;

Example of the type of simulink I'd like to have:

Youtube video of my prototype:

http://www.youtube.com/watch?v=jgIRu39fH18

So, here's in other word want I want: I would like to have a simulink files that "model" reaction of my disc. I need to get from it a sinus chart. I need to be able to adjust it to my real prototype with a friction factor.

***I think I need to input Simulink my matlab function of how my Inertia Momentum varies in time? ****
Here is the function:
M = force1*armlever1/1000+force2*armlever2/1000

Thanks so much,
JP

 

[FeX32]

Hello JP,

That Simulink diagram you show is key.

***I think I need to input Simulink my matlab function of how my Inertia Momentum varies in time? ****
Here is the function:
M = force1*armlever1/1000+force2*armlever2/1000

This is correct. What you can do is instead of having a Gain K block in your simulink diagram insert an embedded matlab block. This will allow you to vary the inertia any way you like.


"Simplicity is the ultimate sophistication." L. da Vinci
G. Coppola

 

[FeX32]

http://www.mathworks.com/help/simulink/slref/matlabfunction.html

"Simplicity is the ultimate sophistication." L. da Vinci
G. Coppola

 

[JPGraphX]

Hi,

I would like to calculate the function of a rotating disc that has 2 spring slowing it down. (look at my pictures to understand)

Let say I turn my disc 90 degrees clockwise and release it, it is going to oscillate a certain moment than stop.

I want to plot that function and to have a sinus function decreasing to 0 after a "x" number of period.

Thanks for your help,
Jean-Philippe

 

[FeX32]

The other thread you started is essentially the same question. The ode code from there can be slightly modified to do just exactly this. Just replace the polar rod by your springs when modeling.


"Simplicity is the ultimate sophistication." L. da Vinci
- Gian

 

[JPGraphX]

This is exactly my problem, I don't know how to model my situation.

 

[FeX32]

The model is simply:

theta(t)_dd++c*theta_d(t)+K*theta(t)=0

where c is the damping (hard to estimate for real systems unless you do some simple experiments) and K=k1+k2 where k1 and k2 are the stiffness of each of the springs you have.


"Simplicity is the ultimate sophistication." L. da Vinci
- Gian