×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Simulink Disc Rotation (Pendulum movement)

Simulink Disc Rotation (Pendulum movement)

Simulink Disc Rotation (Pendulum movement)

(OP)
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

RE: Simulink Disc Rotation (Pendulum movement)

Hello JP,

That Simulink diagram you show is key.

Quote:


***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

RE: Simulink Disc Rotation (Pendulum movement)

(OP)
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

RE: Simulink Disc Rotation (Pendulum movement)

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

RE: Simulink Disc Rotation (Pendulum movement)

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

RE: Simulink Disc Rotation (Pendulum movement)

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources