[youtube=http://www.youtube.com/watch?v=QB15-uSNvHA]
We stumbled onto one of [Nik Melton]’s projects, an Omni-car. It is omnidirectional, meaning it can go any direction at any time without having to turn. The body was designed by him, then printed with a 3D printer. The control scheme is what interests us though. He has found a simple way to wire it to get the job done. Sure you can see that it suffers from some pretty bad “drift” when trying to go in a straight line, but overall, we think he pulled it off well.
You might want to take a few moments to look around his project page. This guy has done a bunch of fun stuff like delta robots, strange hybrid wheel/leg robots, tesla coils, and arm mounted flamethrowers. Judging by the videos, he’s pretty young too. We think his guy has a bright future ahead of him.
looks weird how it moves.. pretty cool though
I don’t know, it seems like the drift, though momentary is pretty well compensated for, unless that is something he is controlling (I was assuming it was a passive compensation). Very nice project though, good job!
An interesting concept, but it looks like the only thing it does particularly well is spin in place. Moving in every other direction appears pretty erratic, and I am not sure that I would call anything the car does in the video “going in a straight line.”
That said, I am not sure what the advantage is of a setup like this over a more traditional “tank” style of propulsion. The only thing it looks like this design can do over that is sideshift.
If he had a 3D printer, why didn’t he print wheels as well? That body could have been any material or shape. If he really wanted a learning experience he should have printed the wheels as well.
this remember me the propulsion system of the forklift at the “prototype this” workshop
My question… if it could go in any direction, what’s the point of turning in place? A servo on top of the car or leds could indicate the front of the vehicle.
For considerably more difficult construction, the mecanum wheel (http://en.wikipedia.org/wiki/Mecanum_wheel) (the technical name for the aforementioned Prototype This forklift propulsion system) will fix the drift problem.
Initially I thought it had 3 wheels like the Rovio which can drive in a straight line pretty well.
It also reminded me of the forklift wheels on Prototype This, but I also recall seeing an electric wheelchair in the 80s that could go sideways by having small freewheeling wheels on the main wheel, like these projects, but they were mounted diagonally instead of 90 degrees to the main wheel so you could go sideways using only 2 main wheels instead of 3 or 4.
Wonder how loud it is using servos as the drive motors…
Reminds me of the “Sidewinder” forklift (in the link provided)
I’m wondering why he added an extra wheel. Most holonomic robots only use three (it’s all you need,and the things are damn expensive).
This design is interesting but it is not new. The small size RoboCup league has been using this design for quite some time. If you are interested in some examples of this design at work see the media at the following link.
http://www.cis.cornell.edu/boom/2005/ProjectArchive/robocup/
reminded me of the Jeep Hurricane that can turn around where it sits.
This design, however, is to driving straight as a tank is to spinning.
Youtube link to Jeep Hurricane for the lazy:
http://www.youtube.com/watch?v=3b5zH0G5pxE
why not put the wheels aligined with the directions of movement, forward, backward, left, right?
Also from the videos i’ve seen of mecanum wheels they have nicer movement than omni wheels.
I think this sideways drifts is there, because his omniwheels arent ideal. Many times the wheel stays so that it sits between two of the secondary wheels, and then the friction isnt the same on all sides.
There are big professional omnimove platforms which use a slightly different wheel design. The secondary wheels are mounted 45 degree to main wheel (simmilar to Mecanum wheel). They are fine with this with very accurate moves while carring many tons of weight.
Our FIRST robotics team (team 1058) used omni-wheels on our robot for about two years, and we did things a bit differently. We placed our wheels parallel to each other, which does require a slightly different wheel where the rollers are at an angle in relation to the actual wheel. I don’t really see the an advantage of having omni-wheels of that configuration, but I can see that it obviously makes the vehicle a lot fatter. Strange. I can’t imagine why he has them like that.
^Yea, I remember one of these that only had three wheels, way back in the early 80’s. Definitely nothing new. Also, that song rocks! I crank it up at the pub all the time… :)
There’s a massive waste of energy in the movement transition,and on top of that,that Omni car cannot climb a hill,period.
This is plain cool!
However I wonder how difficult it is to actually control and navigate it via remote control.
Cheers, Arne
just to answer a few questions:
the drift is self compensating and does move in a somewhat straight line. but ive found that the drift is actually caused by the smooth floor. the same actions on a carpeted floor are nearly perfect.
the reason i did 4 wheels instead of 3 is that it is in fact much easier to control and far more efficient then 3
i decided to use omni-wheels because theyre about 1/5 the price of mecanum style wheels so the choice was easy.
and it is very easy to control. i have it set up so that one channel controls foreword/reverse, one for left/right, and one for spin.
I think re-orienting the movement would potentially result in straighter smooth-surface motion. With the omni-wheels having perpendicular rollers, I would think you could just drive each pair of parallel wheels for your four primary directions — that way two wheels would be stationary (and perfectly perpendicular to the direction of motion).
Basically, reconfiguring the electronics so that back/forth on each pair of parallel wheels would be controllable, rather than all four wheels being driven relative to one another. When you drive the “left and right” pairs “forwards”, you could get diagonal motion by driving the “front and back” pair one way or the other (resulting in what is currently “forwards” motion).
Essentially, the primary drive mode would be what is now a “diagonal” drive… did that end up making any sense at all?
yes i understand it completely and that was actually my original design, but i decide on doing it this way cause i thought it might be more fun x) but moving diagonally with it now is very slow, its best to have all 4 wheels working together
I have thought of a similar type of car, but the wheels were similar to mouseballs (computer mice!!), driven by two perpendicular wheels.
Never thought of something like this. Is it possible to run it with fewer engines and a clever gearbox?
FingerTech Robotics has a really good set of mecanum wheels for sale, they work MUCH better than the wheels on this robot.
http://www.fingertechrobotics.com/proddetail.php?prod=ft-mecanum-set
http://www.youtube.com/watch?v=DhNm0FOIiG0&feature=player_embedded
the only problem with the mecanum wheels is that they cost frikken $90 while 4 omni-wheels only cost 15
I was thinking Wowwee Tribot (3-wheeled commercial toy).