6dof motion platform ‘lite’

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6dof motion platform ‘lite’

Postby tzuvela » Thu 8. May 2014, 01:26

6dof motion platform ‘lite’

Hello everyone.
I am looking into building a 6dof motion platform for use with VR headset (DK2 on the way) for racing and flying simulations, (and hopefully Star Citizen), and would like to hear your thoughts on 6dof simulator with levers.

The simulator needs to be able to lift about 100Kg of weight, and I’d like to have 7-10 cm of movement.
I have been looking for existing 6dof concepts, and so far merchan-e concept with 6 wipers seems like the most cost effective way to go

https://www.youtube.com/watch?v=FfuxC_f87UI


I have seen a lot of simulators with motor arm connected directly to the push rods and the platform.
According to ebay:
“it is NOT recommended to put weight directly on a gear motor's shaft! An excessive radial bearing load may damage a motor's gear box quickly! It is always safe to isolate the load by introducing a pulley or sprocket system."
http://www.ebay.com/gds/How-to-Buy-the- ... 002/g.html

What do you guys make of it?

The way I see it,
Wiper motor without lever:
Image
Wiper motor with lever:)
Image

Similar concept has been used a lot with 2dof wiper simulators (seat balancing on a pivot point).

I plan to add 6 levers (seesaws), one for each motor, with 1 to 3 ratio so motors only have to lift one third of the platform weight.



This is what the levers and wipers might look like;

Would it be better for motors if the weight of the platform is balanced by a counterweight on the longer side of the seesaw?
How would the change of momentum affect motors?


Here is a rough model of the entire simulator:
(Dimensions and scales are not accurate)





Engines:
I really like characteristics of these worm drive motors:
http://www.motiondynamics.com.au/worm-d ... orque.html
Except shipping, 6 motors cost ~$650, shipping cost $360- 430 for UK :(
I’d be very happy to hear experiences from someone who has these motors.
With 1/3 sesaw ratio, 6 of these motors would have to move about 33.3Kg (100Kg/3)
Motors would lose 2/3 od their effective speed to about 50-60 RPM, which I thing should work great.
Has anyone tried running these at 24V?
How much power would they use, and 24V and how hot do they get? how long can these motors run in one go?

To power these I’d be getting one of IBM server PSU for 12V (or two for 24V)
These PSU’s are built to last and particular model outputs 147A from 12V.
http://www.ebay.co.uk/itm/IBM-BladeCent ... 5afdd59381

Electronic:
Thanos seems to be doing a great job with 6dof electronic boards so that's what I'll be getting :)

Looking forward to your thoughts.

Thanks,
Tino.
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Re: 6dof motion platform ‘lite’

Postby telfel » Thu 8. May 2014, 14:12

Hi

Can I ask your budget?

For motors in the Uk have a look here https://trolleys4golf.com/id34.htm

regards Terry
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Re: 6dof motion platform ‘lite’

Postby tzuvela » Thu 8. May 2014, 17:25

Hi Terry,

Thank you for your reply and for sending the link to https://trolleys4golf.com/id34.htm
Do you know the characteristics of these motors, Torque, RPM, do they have the same speed in both directions, etc?

Budget is not yet set, however I do plan to make it as affordable as possible, hopefully around 1000 Euros.
Thanks, Tino.
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Re: 6dof motion platform ‘lite’

Postby ferslash » Thu 8. May 2014, 22:27

i saw a video of guy building 6dof using just wippers... without using the lever and it worked (i dont know for how much time) but it worked...

i guess using the lever will be slower but of course better...

you should tryit i would love to see it :D

best regards

fer
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Re: 6dof motion platform ‘lite’

Postby jhordies » Fri 9. May 2014, 00:07

Hello tzuvela,

Nice project !

I'm not exactly sure of what this means :
You can mount a load to either side of the worm drive gearbox due to its hollow output shaft, though it can only be fixed from one side (fits a 12mm shaft internally).
from http://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html

But if it means that you can choose on which side you fix the shaft, I think you should you reverse it on one of the motor per pair to get a symmetric design.

Be careful not to under estimate the payload.
It should include the structure + half of the lever + rods + links + the seat + wheel + pedals + Oculus + a dressed up player.

It's a very good idea to use levers to reduce the required torque.
Though I'm not sure how the levers can follow the motion in 6 degrees of freedom, maybe the 4 rods per arm is already taking care of that but I have a hard time picturing how il will behave.

About the having the load directly on the gear box, 'Ebay' is probably right. And maybe my motor wont make it in the long run.
But I hope to be on the save side with 205Nm of torque per motor for my project without lever with my current design.

Keep up the good work
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Re: 6dof motion platform ‘lite’

Postby tzuvela » Fri 9. May 2014, 01:41

ferslash wrote:i saw a video of guy building 6dof using just wippers... without using the lever and it worked (i dont know for how much time) but it worked...


Yeah, in my opinion that is the model T of 6dof personal simulators :)
ferslash wrote:i guess using the lever will be slower but of course better...

if you are using levers to lift more weight, it will definitely slow down motors, that's why I like that 180 RPM motor.

ferslash wrote:you should tryit i would love to see it :D

That's the plan, no eta yet, but I think it would be great to make affordable 6dof personal simulator.
Cheaper simulator would enable more people to build one, along with VR HDM, the future is looking really cool.


jhordies wrote:Hello tzuvela,

Nice project !
You can mount a load to either side of the worm drive gearbox due to its hollow output shaft, though it can only be fixed from one side (fits a 12mm shaft internally).

But if it means that you can choose on which side you fix the shaft, I think you should you reverse it on one of the motor per pair to get a symmetric design.

Hi jhordies,
Thanks!

I am thinking about symmetrical design, and positioning wipers and levers in line with pushrod angle.


however I am not sure how great would be the benefit.
Levers and pushrods should be symmetrical (it's probably not apparent from the model as it was made without using real measurements)

jhordies wrote:Be careful not to under estimate the payload.
It should include the structure + half of the lever + rods + links + the seat + wheel + pedals + Oculus + a dressed up player.

It's a very good idea to use levers to reduce the required torque.
Though I'm not sure how the levers can follow the motion in 6 degrees of freedom, maybe the 4 rods per arm is already taking care of that but I have a hard time picturing how il will behave.

I think I'll have about 100Kg total weight, pivot points should take most of that weight, and for heavier players, bigger motors or longer levers are needed :)

jhordies wrote:Though I'm not sure how the levers can follow the motion in 6 degrees of freedom, maybe the 4 rods per arm is already taking care of that but I have a hard time picturing how il will behave.


Levers just go op and down, like https://www.youtube.com/watch?v=_jQkc9kNem8
I've made a simple demo using some cardboard and duck tape, and pins (It's really fun thing to make :) you can see the movement of wiper motor (when it's not connected to the lever) drawn on the right side, as a larger half circle.
On the left is the side that would be connected to the seat (smaller half circle).
Unfortunately the pivot point is not really visible.


jhordies wrote:About the having the load directly on the gear box, 'Ebay' is probably right. And maybe my motor wont make it in the long run.
But I hope to be on the save side with 205Nm of torque per motor for my project without lever with my current design.

I'm sure your motors are much more robust than viper motors, however I don't see why you couldn't add levers if you want later.

Looking forward to your updates!
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Re: 6dof motion platform ‘lite’

Postby ferslash » Fri 9. May 2014, 18:27

just to add this comment to the conversation...

i saw a guy using two wiper motors per axis insted of 1, avery pair of motors, the pots, the h-bridge, and the arduinos, where shared for every pair...


i mean he was doing this.... two motors connected to a one channel of the h-bridge and to the arduino card....

in the forum all the guys told him that it was imposible because he had to syncronize the movement of the motors... but he did it any way and he has been using for months his simulator...

i guess that using two motors per axis insted of one is even better... but... only if you have access to a bunch of almost free motors.


best regards

fer
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Re: 6dof motion platform ‘lite’

Postby sirnoname » Fri 9. May 2014, 20:33

Do you think a electro car or a tram do syncronize the motors?
If a answer is correct or did help you for a solution, please use the solve button.
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Re: 6dof motion platform ‘lite’

Postby tzuvela » Fri 9. May 2014, 21:27

Hi fer,
I'm trying to minimize cost so I wouldn't like to increase the number of motors :)
Also, you then need to figure out how to link two motors, you also double electronics and power supply requirements.
I would rather go for a larger motor if I'd really have to.
If you have access to free motors then go for it, but I'm hoping to use cheaper worm drive motors, and use levers to reduce the load on motors.

Hi sirnoname,

Sorry unfortunately I don't know much about electro cars or tram motors, are you thinking of using tram motors for simulator?
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Re: 6dof motion platform ‘lite’

Postby lucasdiulbern » Sat 10. May 2014, 04:26

I saw how to use two motors on this site.


http://www.voovirtual.com/t17642p45-pla ... ht=cockpit
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