Showroom **RIP** - 6DOF project using 12v DC Motors, Sabertooth 2x60's (was MM's) and Arduinos + OSW

Yeah @momoclic you are clever with all your numbers and stuff what's he talking about ?? Lol

I think the focal point of the rods faiseau is under the platform ???
This should be above ???
This is my interpretation, but I do not understand.

@SilentChill not sure too but i remembered watching something similar in the past. look at his video here and in the 6 dof graph you will see a yellow ball 4:05 in video probably that's the COG @tronicgr is talking about.and if i am right your build has this yellow ball lower near the upper frame and must be higher.
BTW great job waiting to see your build in action with you on it

What he is talking about is the center of rotation of the rig. Not so easy to get right without using the proper 6DOF math. But keep at it.

Right, on the video it seems that the center of gravity converges with the tray rotation center.
This has the effect of limiting the dynamic forces.
Well done!

now we are coming back to the maths, very interesting view about the COG. Did not know that before.

I rather think, physical or kinematics ;-)

so i need to chop my arms in half that should lower it enough nearly

Under reseve have understood that Tronicgr said:
Extending your rods converging towards the ground.
They should converge towards the sky.

If you want to play with the physical calculations - http://www.fly.elise-ng.net/motionplatformdesigner

@SilentChill found this video




from here http://www.xsimulator.net/community/threads/6dof-platform-with-small-dc-motors.5634/#post-58448

Bizarre "center of gravity" I would speak more gladly of "center of rotation"?
We can not shift the center of gravity of the mass ...

Hi
might throw some light on the maths, have a look at the config file as this gives the relationship of the crank arms pushrods and the centre of rotation of the top platform

http://bffsimulation.com/6DOF-Motion-Software.php

regards Terry

I have not got a clue what all this means but im just gonna crack on and see what happens, COG where ever it is aint gonna stop me so I aint worrying about it. He mentioned about some 47000uf caps aswell that I would need but guess what ?? I dont need any...............

He always playing down anything that doesn't use his beloved Thanos board.

Ok back on track now got some more fans installed over the MM's and all heatsinks in place although I am 2 MM's short only had a spare 3 so awaiting replacements.

Ideally the COG and the COR are the same or close to it in order to minimize the off feelings from rotational accelerations. We are talking about the COG of the person on the rig here though and not necessarily the COG of the rig and rider. My feeling is that somewhere between a person’s waist and their belly button is the ideal COG and high enough up.

I agree with your sentiments on Thanos last comment. One could look at it as being informative until you consider the fact that he rarely posts anything and then this one deals with 6dof math. It was really just an opportunity for him to take another cheep shot at others successes!

Btw, you probably won’t know if you need to add any large capacitors until you have a fully working loaded platform so you can see if you have enough available current to handle the peak draws. If not using large capacitors in parallel with you psu's may be enough to help supply the necessary current thru the peaks.

Thanks @BlazinH something I understand

Its all early days for me with this rig so improvements are on going but early tests tonight give me good confidence that its going to work ok. Movement wont be anywhere near the big AC motors but for what I want hopefully it will be enough.

Sorry guys that you see it like that. I was only trying to give some advice and good luck. I'm really interested to see if this will work, as everyone else here does.

And excuse me if you think that "my design" motion controller is more commercial than the arduino, or less DIY.

@tronicgr Maybe you could give some suggestions, I suspect there will be quite a few people who will try and design something similar.

What can be done to help with this "COG" that you talk of.

Can you please explain in simple terms for us newbies here.

Thank you

It is a mechanical adjustment I guess ...
As any stewart platform only uses a " 90 degree rotation" for each crank arm ...
So you have to set the center of this " rotation range" as your COR is needed ...
1- Horizontal crank arm rotation center gives an exact top platform COR .
2- Pointing down crank arm rotation center gives a lower COR than the top platform .
3- Pointing upward crank arm rotation center gives a higher COR than the top platform .



@SilentChill ... Try that with your Sketchup design and SimTools ...