How to determine suspension ride frequency in adams car

[nasb12]

I have a modelled the suspension of a vehicle and now I'm trying to determine its ride frequency, which simulation would I need to run to achieve this.

 

[GregLocock]

Do you have a full vehicle model? If so:

I think you'll find static vehicle characteristics tells you one quick estimate. There are several frequencies in the report

Bounce node loc. wrt H-pt. mm 1943.44
Bounce natural frequency Hz 1.38
Pitch node loc. wrt H-pt. mm -903.64
Pitch natural frequency Hz 1.94
Ride frequency ratio 1.36
Front
Wheel hop natural freq. Hz 10.57 10.58 10.55
Wheel tramp natural freq. Hz N/A
Front ride frequency Hz 1.31

Rear
Wheel hop natural freq. Hz 9.00
Wheel tramp natural freq. Hz 11.82
Rear ride frequency Hz 1.77

The bolded ones are the ones we usually call ride frequencies but they are really corner frequencies

One problem is that in a real car the 'ride frequency' varies with amplitude, so a given frequency(s) only applies to a given track and speed.

The 4 poster test is a good one for theoretical ride frequencies, otherwise you just run it over surfaces with various wavelengths at various speeds.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[nasb12]

Hello Mr Locock,

Thank you for taking the time to reply me

I'm having a few issues

1} the FSAE model has bellcranks on the front and rear suspension but the vehicle I am trying to model has direct dampers on the front suspension and a pushrod setup with bellcranks on the rear suspension.
I don't know how to modify the geometry on the front suspension to make it a direct damper.

2} Is there any way to assess ride frequency by analysing just the front and rear suspensions individually?

3} yes it's a full vehicle model of the FSAE 2018 template but when I try to run the base fsae 2018 model to determine static vehicle characteristics i get the following error

---- START: ERROR ----
This command cannot be processed until a model has been defined.
Maybe you need to add a FILE/MODEL=pathname, OUTPUT=prefix command to the command (*.acf) file.
---- END: ERROR ----

command: preferences/solver=CXX
command: preferences/list,status=on
PREFERENCES:
SIMFAIL = NOSTOPCF
Contact Geometry Library = (not loaded)
Thread Count = 1
Library Search Path = Not Set
Status Message = Off
Solverbias = CXX (C++ Solver)

command: control/routine=abgTire::con901,func=user(901,465,98,104,1,2)
command: control/routine=abgTire::con901,func=user(901,473,99,105,1,4)
command: control/routine=abgTire::con901,func=user(901,483,107,113,1,6)
command: control/routine=abgTire::con901,func=user(901,491,108,114,1,8)
command: output/nosep


---- START: ERROR ----
This command cannot be processed until a model has been defined.
Maybe you need to add a FILE/MODEL=pathname, OUTPUT=prefix command to the command (*.acf) file.
---- END: ERROR ----

command: control/routine=abgVDM::EventInit, function=user(5,1,8,0,3,6,8,17)
command: control/routine=abgVDM::EventRunNext, function=user(0)
command: control/routine=apresolver::consub, function=user(1111,14,0,0,0,0,507,508,60,63,18)
command: !
command: stop


Finished -----
Elapsed time = 0.00s, CPU time = 0.00s, 0.00%

ERROR: Cannot load results! File 'DEMO_1_svc.res' not found.
Simulation is complete.

 

[GregLocock]

(1) look in help for the options with your suspension template.
(2) If you know the sprung mass at one axle then the ride frequency is just 1/2/pi*sqrt(wheelrate*2/SM), get wheelrate from the vertical test
(3) Looks like the model didn't build. What files are in your working folder?


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?