2 robots 1 controler

[dknguyen]

It goes straight because "technically" each wheel can roll in any direction (X-direction and Y direction). If you get two wheels to roll in such a direction that the movement in one axis cancels, and the movement in the other axis is the same, the robot will move straight in that direction. And since the third wheel can also roll in any direction, it won't interefere with that movement. (It makes it easier to think about if you just pick any one wheel to be the front and do nothing and have the other two wheels to control the movement.)

If the two robots are supposed to perfectly synchronize movement, it sounds like you are supposed to make it so that if one robot hits something, they both stop...that means the robots have to talk to each other...that makes things a bit more complicated (maybe).

Are the robots all autonomous or remote controlled? Because mirroring movements when they are both autonomous means that one robot is practically controlling the other robot (the only thing the slave robot does it tell the master whenever it hits something so they both stop). If they are mirroring movements based on a remote control then that means that they have to communicate with the remote control AND each other so that they both stop when they hit something...that makes things more complicated. How is it supposed to be exactly? Because making it so that they both stop when one hits something makes it more complicated than if they just blindly mirror each other's movements.

And are you sure you want to use omniwheels? You got two robots, and 3 fancy (expensive) wheels per robot with 3 motors per robot makes things pretty expensive...then again, maybe you are making the omni-wheels yourself since you are a MechE.

 

[docel]

Chaos 'n Kid-stuff

to have 1 telling me that my english is bad enough.. but to have another rub it in is rather rude.. it is disrespectful and annoying.. n i thought i was childish..

Apology accepted. Let me rub it in some more..

Some years ago, the Chinese invaded India with their Cheap RC cars. Some thoughtful soul donated 20 of these to our school. The kids made short-work of these and in quick time, most of them conked out. The cars, I mean!
When asked, I agreed to repair, on condition: I get to work with them and the kids!

The result? CHAOS.

SYSTEM A
1 Master remote ( 27MHz TX), 5 Slave cars ( 27MHz RX )
The Slaves did everything together, by the Masters commands. This was quite interesting and a big hit with the Adults. The kids did'nt count, since they are always hooked, by default.
Imagine 5 cars of different shapes doing Fwd, Rev, FwdL, RevR etc.,.......Together in the concrete quadrangle!

System B

Obstacle sensors connected to a 27MHz TX buttons, 1 TX on each car.

Now , The cars did what the Master wanted + did what ANY ONE of the cars did too!!
All cars are going break-neck and suddenly veer to the right, or skid RevL or something like that, depending on the particular car what finds an obstacle...

This, was even more a hit.
....Except for some confusion regarding Master over-ride.

System C

After some other combos, the kids got bored of this, as usual. Some smart alec kid wanted assorted lights/ sound/ speech and the cars be camouflaged as demons, dance etc., and the whole troop echoed in cacophony.

I introduced them to F84s and Nigel. Then,

ALL HELL BROKE LOOSE !!!

 

[sicburger]

to all that has helped.. thank you..

 

[JimB]

One thing to be aware of, two robots are very unlikely to behave in exactly the same way (or mirror image) without the use of some kind of feedback control.

You may get near to it by using stepper motors for the drives and ensuring that both robots get the same number of pulses to the motors.

The problem comes from the fact that the parts are not absolutely identical. A bit more friction here, a slightly more powerfull motor there, the power supplies not identical, it just gets worse and worse.

JimB

 

[docel]

Right!
...Exactly why ALL HELL broke loose!!?
but then, who cares about precision in a toy?
Ordered 100 motors from Mabuchi. Had to resistance-equalise every pair for 'straightness" !!

 

[philba]

of course you could had added encoders to each wheel and used that to get equal revs...

 

[docel]

Yea, we do that for the path/Maze solvers where cost and complexity is'nt a factor. But for general line/ wall/ obstacle, a simple coil of solder will do! These never go straight, anyway :lol:
This also helps my students learn the hows and whats of resistance....