Automotive Chassis / Kinematics

[dubstar-04]

I am very interested in working on an Automotive chassis workbench. I have used MSc Adams http://www.mscsoftware.com/product/adams in the past and I would like to have something similar in FreeCAD. I have done a little playing and I have a basic skeleton workbench allowing:

- Creation of a chassis object
- Adding components to the chassis, front assembly, rear assembly, weights, COG...
- Controlling the properties of the assemblies and adding sub-components, anti-roll bars, wheels/tyres , uprights, springs and dampers...

I am now looking at adding the graphical objects and starting to think about how to add analysis to the workbench and I would like some advice.

- Whats the best way to implement some kinematic functionality to analyse the suspension geometry?
- Whats the best way of adding graphical object to python objects?

I understand that the scope of these questions may be a little vague, i am just looking for some advice.

Thanks,

Dan

[microelly2]

First to do is to provide computations for basic properties like
center of mass, moment of inertia, tensors for deformation, aspects of friction ...
on base of the cad model

then you need something, where you can describe the constraints (newton dynamics, fluids?, ...)
and simulate it.

my examples/testcases are:
fill a bottle with wine
fill a boot with water through a leak and let it sink, control a submarine
pendulum, coupled pendulums
4-leg walking robot
cylinder space of a combustion engine
(simplified) airbag

I think about an interface to open modelica, but is still a far future dream.
Modelica is powerful enough but its a lot to do to get the interface.


Simple cases like hooke's law for suspension can be done with pse (python simulation editor) or octave(free mathlab) to solve differential equations but I still have not found an interface to FreeCAD.

- Whats the best way of adding graphical object to python objects?

what do you exactly mean with this?

[m.no]

I was thinking a little about Dynamics workbench earlier and i made some quick research. I've got some experience in using alike software.

I would divide whole Dynamic Simulation into two independent parts. Dynamics workbench istelf would be preprocersor that can export scenes as input files for external solvers (just like FEM workbench). There is MBDyn (https://www.mbdyn.org/), AFAIK there is no collision detection, yet. There is also HOTINT (http://www.hotint.org/) which also supports SPH simulation, yay! Of course there are libraries like ODE or Bullet, but as said, they are just libraries not solvers (AFAIK), and both are not so accurate, but they are fast (simulations in real time).

As postprocessor I would see animation workbench extended with importing simulation results and some post processing functions like tracing points, drawing some plots etc. Later, even exporting loads to FEM.

About car suspension simulation: i think it should be some kind of extension to dynamics module itself. We can also add later something like LMS' Discrete Track module for simulating tracked vehicles.

Personally i don't have much time for now to do any real work (full time work and MSc degree in progress), but i can make some more research how this should work or how this is working in other sofware.

[r.tec]

Hello,
I did some projects with Adams/Car, too. But only with a student's licence that were very restricted to few users because the license fee is prohibitively expensive.

The other day I learned that the master grade students work with Dynatune (http://www.dynatune-xl.com) which is based on excel and at least the basic programme is more or less affordable with €99. I read somewhere that this excel-programme was conceived by an ex-racecar-engineer.

Kind regards,
Helmut