New build, arduino, motomonster, 2dof

Hey all,

Phil here, looking to start a new motion platform build and want to make sure I'm understanding the core concepts correctly thus far.

I think 2dof will suit my purposes, as if I'm not mistaken I can get pitch and roll simultaneously with 2dof, I've attached a crude mock-up of the initial plan showing a combination of motor directions and resulting platform angle, if folks could let me know if this is off in some way that'd be great.

Are mounting holes the only reason some motors come in left and right versions? For the motors I'm looking at, I don't see any mounting holes so I'll have to make brackets I would think.

Components

2x - 12 Volt Gear Motor, 150 RPM, 25/1, 180 W, 30-40 NM
2x - Linear 10k Pot
1x - Monster Motor Controller Shield
1x - Arduino

As I understand it, not counting additional software the arduino reads the pots for motor position and then sends a PWM signal to the moto shield for each motor, the PWM determines the speed of the rotation and duration of the PWM signal determines the amount of rotation, since the rig should only use a quarter or so of the motor's rotation how does one avoid over torquing and destroying the pots? Also, any leads on an appropriate power supply easily available in Canada, as well as safety features I could build in, that'd be great!

Glad to have found this community, I was going to go with Linear Actuators until I found these forums and learned most folks go with DC motors.

Would this power supply work?

Power Supply 12V 15A

Hi @substatica
15 A is not enough. You'll need about 30 A per axis. So you better look for two power supply units with 30 A or one with 60 A. A decent PC PSU will do.

Okay, I've got a bunch of those laying around then.

have fun with your project!

you may find an arduino code fitting motomonster in my signature

Thanks! Initially the setup, assuming it turns out safe, will be used as a base for my infant son's bassinet -- this is why I was asking about safety features, I was thinking an accelerometer I can read to kill the power if any undue force is detected. I'm hoping to program some smooth wave, walk, rumble motions. Then when he's a bit older I'll replace the bassinet with a seat and controls and convert it to a simulator of some sort.

I had the same concern
Maximum speed is a parameter of the code: low value makes the movment smooth and calm.

Adding an accelerometer on top of this would be possible, some simple lines code to add...

One thing I don't have is a lot of metal working tools, a small MIG welder, drill press, grinder, that's about it. It looks like the motors I'm planning on buying need shafts, pivoting arms and linkages, I ordered two of these Heim Joints, does anyone have a go to place online where I could source more of the linkage parts?

This shaft, cut down to size, should work for the 1/2" motors I referenced above and these couplings should work to attach the pots, no?

1/2 in. x 3 ft Keyed Shaft
2x - 1/2 in. Shaft Coupler

I'll try to give back to the forums with a full parts list, how-to and results when it's all done Thanks for the help!

Sorry but your motor position is in the worst case scenario , your motors will have to work too hard to gain any real fluid or sim comparable motion. specially with 25:1 boxes, it doesn't work. People have tried this and it fails badly , again Sorry.

@substatica , I agree with Rob, your kid and your weight are two massive differences.
If you develop a code that gently rocks the kid, then yes, but DO NOT put a race track through it or even a roller coaster.
Also, design is bad, after 14 designs, depending on how much overall weigh you plan to put on it, you will have to move the motors to connect a lot higher, like a foot motor mount or shoulder mount at rear.
You could use 50:1 or higher boxes and use like a taller desk racer mount on the side, but again, platform design needed.
People have done this sort of design over and over and they eventually had to rebuild and or re-design. Even me.
I have pictured a foot motor mount, where obviously your feet would sit, so make the motor connections are higher than your toes.
This keeps the design compact and will perform better.

So you're both saying I need the arm mounts on the platform to be higher? This build will not be for me, just the kid, I may re-purpose the setup later for a chair. I also asked the motor seller if they could send me 50:1's which they also offer instead of the 25:1's I won the auction for.

I would recommend buying hall effect pots too as they are far superior to the normal pots only slightly more expensive but worth it.

@substatica , if its for your child, then yes 25:1 and the current frame design will be fine.
Its just later if you plan to convert it for yourself, then you may need to look at frame re-design and different gearboxes.

I ordered a couple of these to use as pots, initially at least, do you have an example of the type of flexible coupler you're referring to? All I found is hoses with hose clamps when I search for that. Planning on writing my own software, initially at least as it won't need any sim interface, only some pre programmed motions which I can stream or hardcode on the Arduino. I've also got a spare RasPi kicking around I can use to talk to the Arduino.

I appreciate all the help, if folks are interested I maintain a blog with other projects I've undertaken,

http://unmaintained.com/

so you are not going to use Simtools then?