Is there anybody with ADAMS/Car experience?

[Tudor Miron]

Hello,
Is there anybody with some ADAMS/Car experience?

Thank You
Ted

[Tudor Miron]

Hello,
Is there anybody with some ADAMS/Car experience?

Thank You
Ted

[Buckingham]

I have a lot of Adams/Car experience, most of it involves spending wasted hours in a computer lab scratching my head and staring hopelessly at a computer screen.

After about a year or so of that you will start to get better. After two years or so you will be able to use it readily in the design process and the anal retentive suspension nerd in you will be able to sleep at night knowing that your motion ratio was designed to be linear to within 0.1% over the full suspension travel plus 1 inch either way, you know....in case you change ride height.... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Tudor Miron]

Thank You for your reply Donovan,
Yes I'm aware about famous "user friendliness" of ADAMS. I have to say that for simple things like geometric "installed" motion ratio I would use WinGeo - making it linear within 0.1% will take few minutes.
I'm interested in ADAMS for dynamic simulations and may be because of the challenge – guys at MSC must have won all "frustrated customer"� awards ï�Š.

Would You please help me with some suggestions?

When I create single suspension assembly with some chosen spring rates – how do I find at what ride height my assembly is at the start of say parallel travel analyses?

Thank You
Ted

[Tudor Miron]

So Donovan, http://fsae.com/groupee_common/emoticons/icon_wink.gif
Your experience doesn't go any thurther than letting you say that You have a lot of it, that in a year I will get better http://fsae.com/groupee_common/emoticons/icon_smile.gif and that A/car is good for designing accurate, almost perfectly linear MR?

Thank You
Ted

[mtg]

I used ADAMS and Mitchell when I designed the 2004 UMR suspension.

The strong point of ADAMS is that once you get the thing open (harder than it sounds), get your model, and run the simulation, you can spit out just about any plot you can think of.
The low point of ADAMS is like what's mentioned above- its a pain in the ass to use.

Beware of kinematics programs giving you wrong numbers.

[Omer]

hi
i'm designing our suspension,and as other have said not so friendly,even so i managed in a few weeks to build a pretty good model,using the fsae template and run the simulation to receive migration of the RC,camber change,scrub.(those are the importent things to me.
it's better than programs that calculate Rc by geometry(it think)but because of that every little change in your model,includung rocker dimensions changes your output.

about the spring rate i don't have an answer but found out it doesn't make a big difference.

use kinematic mode.

use the forum at:http://forums.mscsoftware.com/adams/ubbthreads.php
it's very helpful.

pay attention to adams definiton of camber,they take it relative to the body where for us we need it relative to the ground.

good luck

[Tudor Miron]

Thanks Mtg, Omer,

I'm designing a GT type car with outboard suspension (no rockers for now). I wanted to do exactly what you described - model front/rear suspension - analyse it till I get satisfactory results in camber gain/loss, FVSA dynamic angle/length, scrab, ackerman, bump/roll steer etc., etc. - You name it.
As suspension is not inboard I thought I'd use TR_front suspension (double wishbone available in shared database) to modify it to suit my geometry.
Problem is that when I submit it to simulation (parallel wheel travel for example) - I don't know at what ride height my suspension assembly is at 0mm wheel travel. In othere words what are coordinates of say LCA front inner hard point...
Also with springs - installed length and preload. As I understand when you decrease installed length of spring by preload, one would expect the chassis to go down (installed length change by MR). Also I would expect that RC height will go down as well. Problem is that when I did such changes (installed length decrease) RC went up... I got a bit confused. Than I tried to increase installed length more than it's free length – thinking that it will act as if I'm turning the spring lower perch down and so moving the chassis down (decreasing ride height) – again – RC went up...
So I'm a bit confused here. Any way knowing the chassis ride height at static equilibrium would be helpful – at list I would knew what is going on with the height of the chassis when I change spring rate/preload/installed length.

Thank You
Ted

[Marc Jaxa-Rozen]

I'm not familiar with the other templates but preload is defined independently from the spring length in the FSAE template, increasing it will jack up the chassis (and RC) by effectively increasing the initial spring force.

The parallel travel simulation makes you define the wheel travel relative to the chassis so you won't see any differences by changing spring properties, try another mode like roll simulation.

Marc Jaxa-Rozen
École Polytechnique de Montréal

[Omer]

hi
I think I understand your problem and has encountered it myself.

you set your hardpoints, and then you run a simulation,your question is are those hard points change according to car mass,spring rate etc.. while simulation or those really are the points adams uses for his simulation.
did i understand?
anyway this was my problem and i asked it in the forum,they didn't gave an answer just said i didn't understand completley the meaning of a hardpoint.


try the help and the documantation maybe the answer lies there.

as for the springs,the way i see it, making the preload bigger will take the chassis up,and the Rc as well.

keep me updated

[ben]

My approach to ADAMS/Car was always to model the suspension hardpoints in the position I wanted them in at ride height, then adjust the preload in the spring until it was equal to static load on the spring.

A simple hand calc should get you close enough. Martin Kieltsch from Volkswagen has written a script to automatically adjust the preload. Martin is a regular on the ADAMS BB and is probably one of the best A/Car users outside of MSC.

Unless you just want to do pretty pictures to impress the judges, I'd create your own templates from scratch and learn how to write functions measures to actually get the information you want. The easiest way to get lost in ADAMS is to make assumptions regarding which axis system you measured something in.

Ben

[Tudor Miron]

OK,
I figured something out. To make sure that my suspension hardpoints are at designed Z coordinate at static load I made a simple Static Load simulation with same upper/lower Wheel vertical forces corresponding to my static front corner weights. Than I used Measure distance tool to find distance between desired hard point location and testrig's table inertial frame point at desired time during simulation. As my vertical wheel forces where constant – any point in time could be used.
One little trick - you have to set your suspension parameters so tire stiffness and unloaded diameter is right for you. Than you should take into account that at your static loads will will deflect according to it's vertical stiffness. So all hardpoints will go down by corresponding amount. This basically means that if your tire has stiffness of 200N/mm and your static corner load (vertical wheel force) is 2000N than all your hardpoints will go down 10mm.
So I moved all my hardpoint up 10mm (except wheel center) and than played with spring preload to get at designed ride height at designed static load.
And! RC location started correlating nicely with results from WinGeo. This is for single suspension – not full vehicle analyses.

One thing is still annoying – in real life when you change spring preload – turning in/up lower spring perch your springs installed length doesn't change (except a little for additional raised corner weight) but chassis rises. Or if suspension is at fool droop (damper's shaft fully extended) spring's installed length will change but than chassis would not rise.
In adams both things happens at the same time (change in IL and ride height) – I don't understand this...

Thank You
Ted

[ysteve2011]

Does anyone know how to add hard point tables without manually adding each coordinate value for x,y and z? So much of my time is spent copying x, y and z coordinates from Solidworks into excel and then into Adams.

[John_Burford]

Your *.sub files are text files cut/paste your hardpoints from excel to the text file and re-open the assembly.

[Joe_Little]

The points in Solidworks can be linked to excel (Design Tables I believe they are called) and as John said, and the values can be directly pasted to/from excel and Adams .sub files.

I don't remember the soliworks/excel interface being very nice to use, but maybe its improved.

There will be a bit of different between the design table format and the subsystem table format, so some cell linking and what not is called for, but other than the solidworks design table it should be quick and easy.