Problem with roll centre subsystem

I have used the physical modelling for automotive teams tutorials to build a simple suspension model to be used for kinematic analysis, because of this I have fixed the chassis in position by removing the degree of freedom subsystem. This however has caused a problem with the roll centre calculations as it is showing no change in the roll centre height even though the instant centres are moving. Any help would be appreciated thank you.

[Swarooph]

Hello Jake,

Here is what I see. In the tutorial model suspSDO.slx, the World Reference frame is at the center of the chassis. Screenshot below:

However in your model, it is on the intersection of the top right bar with the chassis. Screenshot below.

You can look underneath the IC VizL, VizR and all the Measure XY Subsystem* (in left and right wheel suspension subsystems) to see there are rigid transform blocks that translate from the reference world frame by [0 0 platform_z]. In the tutorial case, this works since it already lines up with the center of the chassis. In your case, I think it needs to be further moved in the Y axis by ((chassis_w/2) + width of grey extension part) to line it up with the center of the chassis. I think this is a first logical step to see if that fixes the issue. Once you do this, we can further see what else needs to be changed. Look for all the World Frame blocks and see if the consequent rigid transforms are properly aligned. My gut feeling says if you fix the rigid transforms in IC VizL, VizR and all the Measure XY Subsystem* (in left and right wheel suspension subsystems), it could fix the issue.

[jake humphrey]

Thanks for the suggestion, however I am still getting problems. The roll centre does move now however it is a movement in the y direction rather than the z direction which shouldn't happen as the suspension is symmetrical and the movement is the same on both left and right. I have uploaded the updated model and would appreciate it if you could take a look and see if you can find the problem, Thank you

Answer 1

[Swarooph]

Hello Jake,

I apologize for the delay. Anyway, I think we may have solved this problem. Great job changing all the subsystems to the right rigid transform translations. We missed two more of them. They were the rigid transform blocks in the Force Test subsystems. Example screenshot below.

You can also take a look at the RC Scope and see that the center is moving only in the vertical direction as shown by the blue line below.

I have also attached the files. Let me know if this was the fix you are looking for.