×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Joint Stop

Joint Stop

Joint Stop

(OP)
Hello,

Are there any possibilities in the ADAMS to stop a joint motion in a specified joint positon like for example in the ProEngineer/ProMechanism? With or without restitution?

An example: there is a revolution joint, hinge like, and one wants to prescribe, that the motion to be limited in a 0-120deg revolution angle, related to the initial position. If the motion reaches one of the limit (0 or 120 deg) it stops (if restitution is not defined or zero), or begins to move back some kind of velocity according to the restitution value.

I can solve the problem with the combination of a joint and some kind of contact, but maybe there is more simple way.

I hope, may problem is clear,
thank you for any help or suggestion

dezsit

RE: Joint Stop

Easy peasy way is to define a non linear torsional spring. This has the advantage that you can shape the force vs deflection curve to represent the real stiffness of your end stops. If you do this right you'll end up with much faster solve times than if you use contacts.

It will be difficult to add damping or friction to that system without using contacts, but there may be a clever way similar to the method at the end of this note.

Using contacts isn't very difficult, it is just numerially unstable, and rather hard to calibrate.

An alternative approach is like this, where a bumper only exerts a force when it is in vertical contact, and also has damping only when it is in contact. Note that this formulation explicitly does not use contact for speed and robustness.

VARIABLE/118971,
,FUNC=(DZ(118971,118775,118775)+ABS(DZ(118971,118775,118775)))/2.0
!  bumper elastic force
VFORCE/118971,I=118775,JFLOAT=1189711, RM=118775
,   FX=0\FY=0\FZ=ABS(AKISPL(VARVAL(118971),0,118971))


VARIABLE/118775,FUNC=VZ(118971,118775,118775,118775)
! bumper damping force
VFORCE/118775,I=118775,JFLOAT=1189712, RM=118775
,   FX=0\FY=0\FZ=STEP(VARVAL(118971),0,0,.1,0.1*(VARVAL(118775)))




 

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies  http://eng-tips.com/market.cfm?

RE: Joint Stop

(OP)
Hello,

Thank you for your answer. Yes, my problem is the calibration of the contact, not its using.

I will try the nonlinear spring, this solution probably has also calibration problem, but maybe easier to solve it, because my joint stop device (in the real design) is a bumper, a rubber like material.

And thanks for the last suggestion, I will test it.

Dezsit

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close