Showroom Compact AC Servo 6DOF Rotary Stewart platform

The first time my rig hurt my back,.. was when i was carrying down to the basement the 100lb 30 inch 1/2" thick steel plate. ... it went on to hurt my back ... many more times....

even just running rectangle tubes along the bottom would likely be enough

Hello Chris, amazing work and commitment!
Very interesting project and I have a lot of questions
How do chinese reducers behave?
Do you feel any backlash during change of direction?
Is backlash constant from day one or it started to rise as you use your simulator?
Do you feel any differences in reducers during motion?
Do you know what is efficiency of these reducers?
Any particular reason why you didn’t go with worm reduces?(possibly low efficiency)
What is your feel about most demanding game concerning dynamics do you need more speed or torque, I am just thinking about if it is possible to go with 100:1 ratio reducers and same speed of motors?
I read that game spits data 10 times per second, so what are maximum angle increments if we talk about roll, yaw and pitch?
Is this fixed period (new data from game) or it has some “jitter”?
Did you saw platform with 3 phase induction motors with encoders, if yes do you know what is trick there?
I thought that induction motors are not very good and precise for positioning but maybe they work in velocity loop…
Do you feel any motion lag between game and platform movement?
I am not familiar with board which makes step/dir for drives and wondering is platform movement soft or hard?
Is there any set up for this board for “movement profile” sometnig like trapezoidal or s curve?
Is there any setup for max speed and max acc/decc?
Based on amount acc/decc drives should work harder or easier to acomplis these requirements.
Thanks
Borko

torque multiplier, at the cost of speed, , luckily they move fast.

no, the backlash is so low its imperceivable, i had to go through a few gears from different suppliers to find the right one that worked like that, and i am glad i kept trying.

no backlash, no maintenance, no wear. i oil my heim joints,.. because i love my machine, and it seems very personal to do so....

are you referring to the two color ones i have, they are the same gear model, just the blue one was a previous revision, same spec, same feel.

all the specs should be on the aliexpress site, they are necessary, but you can calibrate it to whatever reducer ratio you have, its just a variable/scaler in the ac servos you can change,

they are big and loud, this is small and silent.

tradeoffs, tough question, all relative to your goals, mine was speed, reduce weight so i could get the fastest speeds and not need the torque. some folks want to move a car/plane cockpit around.

10hz would be terrible, and you would need to filter that if thats what the game gives you, cause that would be jagged and awful. no, games can emit data in several ways and rates, and through different protocols if at all, often its in a 6 axis vector of force data, speed or acceleration values, that then need to get normalized .. though simtools.

my contorller /simtools, updates the sim at 1000hz, games do whatever the game does,

AC servos give you the PID intelligent control portion as part of the purchase, its more trivial to tell a controller through numbers where it should turn its spiny bit.

as much as lag as you dial into the PID controllers for the ac servo, and simtools filtering, you could turn it off, and have it direct, .. but it would likely rip apart the sim/driver.

my controller controls sets the step, dir,1000 times a second and the spiny bit is following that as fast as it can, it can be very hard, it can be soft, soft enough to rock a baby to sleep, (please dont put a baby in this....) its up to your filtering elsewhere to slow it down.

yes, in each controller, i have these settings documented on how i did it in the repo, but its up to you to fine tune them for your comfort.

high five.

“are you referring to the two color ones i have, they are the same gear model, just the blue one was a previous revision, same spec, same feel.”
Yes
Thanks a lot for answers, I will check repo.

Hey there mate!
If I can chime in... I built my system taking inspiration with Chris's plans and I gotta tell you these actuators are THE WAY to go! They're plenty strong and in combination with the 750W motors they can snap your neck and break your spine no doubt about it! My main selling point would be the noise output though. I already experimented with linear actuators using the same motors and they're heck lotta' noisier than the planetary gearboxes. With the planetary actuators I swear I can play at 11pm without the platform making any noise whatsoever. My pedals are the only things we can hear and believe me this makes immersion alot more realistic since you can't hear those actuators making their thing, as opposed to the linear actuators chirping and squeeking! Haha!

Can't really comment about wear since I've been using them for a couple of months now couple hours a week, though out of the box there is absolutely no noticeable backlash. Only backlash you could end-up having in the long run would be on the output shaft itself on the woodruff keys. If I'm not mistaken Chris ended up welding them to the bushings. There might be other ways to go around but this is definitely something that will happen to any setup using those planetary gearboxes since they handle a lot of torque back and forth with lots of speed. The changes in direction inevitably end up loosing the key even if you tighten those set screws till they strip! I thought maybe using taper bushings could be helpful but there has to be absolutely no slippage.

Keep us posted on you progress! I'll eventually post some pictures of my setup but now I have some other priorities on my plate.

Cheers from Canada!
Alex

Correct, I welded each swing arm to the corresponding motor shaft, its not going .. no where

Thanks guys for info, I indeed believe that reducers are good but the price is "strong". Checked the aliexpress and with shipment price reaches around 250 eur per piece. I was thinking about worm reducers NMRV050 with shipment 1 piece is around 80 eur. Looking at original datasheet it says as ratio is raising the efficiency drops don't hold me here but seems that for 50:1 efficiency is 0.6 ~ 0.7. They have backlash from 18' - 32' and 50 series has max torque about 85-90Nm. As Chris mentioned these are loud. I believe these reducers are copy of original ones which are more expensive. In datasheet of original ones is stated that reducers can support peak torque up to 2 times but it would be interesting to see how this copy behaves. Well I don't know yet if I am going to build if decide I wouldn't go with linear actuators.

18-32 arcmin backlash is huge, you want less than 5

Yes, I also checked here people experiences about worm gears and backlash in simulators.
One thing that found out today about these worm gears, they have max input speed of 1400 rpm and limiting factor is heating due the high friction.

Stepperonline has planetary gearboxes which are some sort of compromise between the cheap worm gears and the expensive precision gearboxes. They have <15arcmin backlash. As Smitty said, <5arcmin would be better.