LMS Virtual Lab Kinematics / Inverse analysis Query

[morris9791]

Dear Experts,

I am a newbie with regards LMS Vlab motion. I wish to model
a very simplified model of a suspension system defined by revolute and cylindrical joints.
I am interested in determining the resultant forces at the pin joints and the spring force due to an applied force at the wheel at a particular point in time.
After searching through the help file, my guess is that I need to do an inverse kinematics analysis in order to determine the reaction forces.
I have a few questions that I hope some of you might be able to provide answers.

1) I am interested the reactive forces at a particular point and position in time, e.g., in full bump. Is the inverse method the correct approach?

2) My understanding is that there needs to be accelerations in the models in order to calculate the forces from F=ma etc. I am not sure if i can achieve these forces if the suspension is fixed at a particular position etc.

3) A static analysis comes to mind but it appears that this method is only used to find equilibrium of the components prior to a subsequent dynamic analysis. So I am guess that is not the way to go??

Any information on the above queries will be greatly appreciated.
Kind Regards
Ed

 

[GregLocock]

1) don't know. The way we do it in ADAMS is to start with the suspension in a design condition and then move it by either applying force or successive defined displacements (similar to IK) until we achieve the desired displacement of the wheel center.

2) Well you can't use statics like that unless you wish to apply D'Alembert forces to each mass.

3) If you want intertial forces then dynamics is the easy way to do it.

I'm astonished that there isn't a tutorial on this.

Incidentally from a practical perspective the inertial forces are very small compared with the static forces in a typical suspension in a typical dynamic event.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.