Matlab suspension modeling

[Belatti]

I have used the software in the past (at Uni) to learn how FEA works: I solved a rather simple (and static) structure using FEA (but without a FEA software). Basically I used Excel to write the system and print the ecuations and then Mathcad to solve the matrixes.

Now I want to learn how to model a vehicle suspension (I guess I´ll start with 1/4 vehicle, thats 1 wheel ) and then keep on adding complexity to the system.

Have anyone arround here worked with Mathcad software to model vehicle suspensions?

Can anyone lend me some files with typical suspension systems already modeled?

Any advice, recomendation, links, files, etc. are welcome

[bajanf1]

I've worked with them in Matlab but I have never created a model from scratch. This download link on Matlab Central contains a pdf file showing the theory of the quarter car model. It also contains the Simulink diagram and Matlab files that can be opened in Notepad/MS Word to allow you to see the code. I intend to create a suspension model withing the next few months using Matlab also and will start with the 1/4 model like you. Hope this helps, good luck.

http://www.mathworks.com/matlabcentral/ ... ange/18410

[Jersey Tom]

Having used Mathcad before... there's no way I would use it for suspension modeling. I'd rather solve by hand. Hell I'd rather jump off a cliff!

IMO Matlab is the way to go... Simulink especially. You can model quarter-car kinetics in literally less than 5 minutes, from scratch! Very easy to build from there.

[Belatti]

Thanks banjan, Tom!

Tom, I would have joined you on the jump when I had to solve the torsion of a non simetrical section using Fourier series... by hand

I have heard that Matlab was more intended for electronics so thats why I was heading Mathcad way. It seemed not that hard for me, at least for the purpose I used it in the past.

I´ll try Matlab, then .

[Jersey Tom]

Matlab is immensely powerful. You can use it for electrical engineering, CFD, suspension analysis, track telemetry analysis, thermodynamics, or whatever you can dream up.

[yzfr7]

Don't think twice, MatLab is the way to go. Maybe it was more electronics oriented in the past, but today it is widely used in mechanical engineering, specially aerospace and dynamics. I am not that into MatLab, but for a starter it is the best option.

The simplest way for you to start with suspension dynamics is the simple 1DOF mass-spring-damper model, a very very simple system for a quarter car model. There are many examples/tutorials around, but I recommend this, which is a 2DOF system

http://www.engin.umich.edu/class/ctms/s ... uspsim.htm

There are loads of other MatLab/Simulink examples in this link, just go around.
If you want something more advanced, you could try this

http://www.sciencedirect.com/science?_o ... rticle.pdf

which is a nonlinear model with asymmetric damping.

The kinematics of the suspension system can be added in any of these systems. It may seem strange with only one wheel, but it helps adding it while dealing with more simple models. Later you could go to half car models, and maybe one day have a full car model working, which is what I am trying at the moment (but not in MatLab).

I have tons of other material/examples/papers on suspension modelling/simulation, but not with me right now. Will try to find and send later.

[elena01]

this is a rather interesting discussion.. thank you for sharing
simulation rachat de credit

[bajanf1]

That Bus model link you posted is like gold for a first timer to suspension modelling. Thanks

[Jersey Tom]

Alternatively you can do it as a block diagram in Simulink and save heaps of time... plus allow for easy nonlinear rates.

[yzfr7]

Some more links, if anyone is still interested.

Basic equations and simulink model:
http://www.prism.gatech.edu/~gtg173g/AE ... ject_2.pdf
http://www.calpoly.edu/~jridgely/ME422/labs/lab1.pdf
http://www.waset.org/pwaset/v19/v19-11.pdf

Material from Georg Rill, an expert in vehicle dynamics. Go to vehicle dynamics -> Skript zur Vorlesung (the book is in English)
http://homepages.fh-regensburg.de/~rig39165/

And if you want to drool at how the big guys do it
http://www.lesoft.co.uk/index1.html

Alternatively you can do it as a block diagram in Simulink and save heaps of time... plus allow for easy nonlinear rates.

I did start with Simulink models, but got really unpleased with how many wires and blocks I had with the more complex models, and completely gave up on it with the incompatibilities that I found across the versions. Plus, if you are looking for fast simulations, not the best option. Still, it is the best choice to start.

[Belatti]

I did start with Simulink models, but got really unpleased with how many wires and blocks I had with the more complex models, and completely gave up on it with the incompatibilities that I found across the versions. Plus, if you are looking for fast simulations, not the best option. Still, it is the best choice to start.

I want to give it a try, still I got a lot of reading to do before. I´ll start with an example file and the softwares help, no matter how hard that may be its my only way right now.

[DaveW]

SciLab/SciCos is an alternative to MatLab/Simulink. Slightly more primitive, perhaps, but free helps. Google & download.

[Caito]

Studying electronics, know Matlab. Would definitely start with simulink.


http://www.easy-share.com/1910968738/22 ... Matlab.pdf


Don't know if the following one was already posted

http://www.mathworks.com/products/simul ... suspn.html


Direct hill jump(semi active)
http://epubs.glyndwr.ac.uk/cgi/viewcont ... ontext=eng



Hope it helps.


Idea: As I was going to do something similar and I see good interest. Does anybody want to make a public project of a quarter car suspension?


bye bye

[Jersey Tom]

There should be plenty of quarter suspension examples around... I'm sure a quick Google search would net plenty.

[Caito]

Hi guys, big revival.. but related.

Today I modelled the quarter car, similar to this one:

The basic difference is that I also modelled a damper between the tire and the road.


I would like to know a little bit about the limitations of the models. Leaving the fact that is just a quarter of a car. What I find disturbing is that the spring labeled Kt is attached to the ground and to the unsprung mass. The problem with this is that you can never have your car leave the ground.

Moreover, If you get a disturbance with a BIG(and negative) dxr/dt the Kt spring tries to instanstly stretch a lot, as that would never happen it pulls the sprung mass violently. So the model should be subject to a road that does not change very abruptly.

What bothers me is that when the road "goes down" the spring pulls the car towards the road which, in reality, it's not that way. What really happens is that the sprung mass is pushing the wheel to the ground, the wheel is not being pulled by the road.

To sum up, with positive dxr/dt the system looks pretty real to me. It fails to represent the reality with a negative dxr/dt.

In reality I don't know if this represents a problem to the model or not. Anyway, do you think of any other similar problem? Does anybody know which could be the solution to the problem presented?


Bye bye!


Caito.-