Vehcile Co-ordinate System 2

[par1]

Does each OEM has different vehicle co-ordinate system?
Each has vehicle co-ordinate system with respect to C.G. of a vehicle?
While doing vehicle testing what should be the component position? with respect to C.G or with respect to ground level?

 

[TheTick]

I've never seen CG as the origin. Not a good choice, anyways, since CG will vary with E V E R Y slight change.

 

[par1]

I understand that CG varies with slight change.
I was talking the component position while doing the initial assembly & mentioned the CG as a reference point for a static condition of vehicle.(C.G. won't move)
Each vehicle has Vehicle coordinate. SO WHAT IS THE REFERENCE FOR A VEHICLE COORDINATE?

 

[TheTick]

I see different (X,Y,Z) orientations for every OEM. Because we are a little further removed (tier 2 or 3), I don't know the origin. I've heard various ways including:
[ul][li]some point x distance in front of the car[/li]
[li]where transmission and drive train are connected[/li]
[li]center of windshield[/li]
[li]center of front or rear axle at nominal loading[/li]
[/ul]

Almost always, the origin is on the car's median symmetry plane.

"An object at rest can not be stopped."

http://www.EsoxRepublic.com

 

[IRstuff]

Most aircraft design coordinate systems put everything to the right of the origin, presumably so that there are no negative coordinates along the plane's long axis

TTFN

 

[ewh]

Most of the aircraft coordinate systems I am familiar with have the z-x plane in the center but forward of the aircraft. The z direction represents waterline and x represents fuselage station.

 

[mloew]

par1,

There is the SAE standard coordinate system detailed in SAE J670 Vehicle Dynamics Terminology. It is not widely used, however, for vehicle development. I use:

X positive reward; origin at the front axle position.
Z positive up; origin at convenient position on vehicle (on a structural fame perhaps, depends on the vehicle).
Y positive left; centered on symmetry plane.

For the vehicle dynamics work, it is different.

X positive forward; origin at the front axle position.
Z positive up; origin at ground plane
Y positive right; centered on symmetry plane.


Best regards,

Matthew Ian Loew


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

 

[sean01]

Hi par1,

In my experience, all the platforms I have worked on have tended to have Z=0 at floor level and Y=0 along the centreline of the vehicle. X however has been a different issue - some companies have had it at the bottom of the oil sump - some level with the centreline of the front wheels. Others preferring to have it on the front most point of the bumper at Y=0.

When I first entered into OEM design for FMC, I used to use PDGS which automatically set up the XYZ datum depending upon which car program you were working on. Nowadays with Catia and IDEAs - it seems that the global co-ordinate system is used as a datum. I have never personally come across an OEM program that has used the occupant or COfG as the datum position. Some powertrain applications however and standard parts are drawn in a local co-ordinate system and then moved appropriately to their equivalent position on the vehicle.

hope this helps


Sean

 

[GregLocock]

One of the big three works more or less as Sean describes, except that the origin is somewhere under the ground, and forward of the front of the car. X points backwards, parallel to the general run of the floor in the XZ plane, ie not parallel to the ground. Therefore Z is not truly vertical, and forward motion is in the negative x direction.

The coordinate axis needs to be fixed relative to something that doesn't move much during or between successive programs, I believe the crease where the firewall hits the floor may be the ancestral location that was regarded as fixed.





Cheers

Greg Locock

 

[Samanthajane]

One of the "big three" uses the following dimensions when
locating the Vehicle Origin from where all vehicle dimensions are taken from.

The X plane runs from front to back of vehicle when viewed in side view ( front of vehicle pointing left).

The Y plane runs from side to side of vehicle ( door mirror to door mirror) when viewed in front, rear or plan view.
note: the right hand side of vehicle is always positive Y and the left hand side of vehicle is always negative Y.
This is irrespective of the actual drive of the vehicle.

The Z plane runs vertical from the bottom to top of vehicle when in side view.

X 0 = 2000mm from the vehicle centreline section, of the IP rear most point.
Y 0 = Centre line of Vehicle.
Z 0 = 500mm below the lowest point of the front door seal.



Regards

Samanthajane

 

[par1]

I appreciate everbody's info on Vehicle co-ordinate system.

some few questions associated to this forum:

1. Before starting the solid model how do one make sure that the model will be in a vehicle co-ordinate position?

I mean to say before the any new vehicle program starts the OEM people know the each subassembly co-ordinates?

Do you think it is appropriate to put the component in a vehicle position after the solid model is done?


Thanks in advance,

 

[ewh]

I'm not sure how the auto manufacturers do it, but I've worked at companies that did it both ways.
One was a military vehicle manufacturer, where each part was modeled at the coordinate system, them mated to the proper placement at the assy level.
Aircraft manufacturers I have worked at do it the other way. The parts are modeled in space at their position in the finished aircraft (except of course fasteners and related hardware). The parts were still properly mated, but even without the mating, they would appear in the correct location.
The logic seems simple. If the part is going to be used in multiple assembles, each at a different location, then model at the coordinate system. If the parts are unique and used only at one location on one vehicle, then model relative the vehicle absolute coordinates.

 

[GregLocock]

Most new car programs are based on a previous car, so we just use the carryover coordinate system for the floorpan or whatever.

You can build your model in any coord system you like, it's when you want to talk to other people you need to move it and spin it into global.



Cheers

Greg Locock

 

[Samanthajane]

Par,

As ewh quite rightly points out it's logical to model the Part / Assembly in it's vehicle line position so as to check mating issues.

Within C3P Ideas, the option is available to model the component either in vehicle line position or at global.

The question come's as to how other users of the component or other designers trying to match to the "new" component, know the part /assembly is in it's correct vehicle position.

This can be made known by making a Master Package, which has all components as sub-assemblies as instances, that can be moved into their correct vehicle positions but will not move the original components.
Therefore other users will know that if they reference the Master Package the components within will be in vehicle line.


Regards

Samanthajane

 

[Rob45]

More than one US OEM uses the front axle CL as the origin for x, y, and z. Z positive upwards, x positive rearward, and I "leave it to the student as an exercise" to figure out where positive 'y' is. <grin>

 

[buckeye1160]

Working with many US and foreign auto and truck OE's x,y,z coordinates are fairly universal in direction.


x=fore/aft or front to back
y= cross car or from centerline of vehicle outbnoard
z=up/down

US OE's use xyz coordinate convention
some Japanese use t,b,h for x,y,z but is just change of letters.

 

[Hydroformer]

My $0.02...

I've seen the most convenient origins at the center of the front wheel spindles.

*Without data, you're just another person with an opinion.*

Hydroformer