Hello arduino community,
I am a member of my school robotics team. We build battle bots and go up against other schools in competition. I'm sure many of you are aware of how it works so I'll save my breath.
Our competitions are held in an arena made up of a steel floor and plexiglass walls.
Here's where my idea comes in. I was thinking about reinventing the wheel, literally. The battle bot wheel of course.
Every robot in competition goes with either colson wheels or banebots wheels. basically, its a rubber wheel that relies on friction of course to move. In battle every team has the same problem, that is traction. pushing around 15lb objects ruins the wheels and such.
So here's what I was thinking. The floor of the arena is steel. So at first I thought lets make a wheel out of magnets. I quickly took a step back and said, that won't work, because you simply wont move lol. That is when I thought, why not "embed" electromagnets into a wheel.
In the attached picture, it shows what I was thinking. Now that is only the crude idea. Making the wheel spin forward would consist of knowing the position of the wheel and having individually addressable coils in the wheel. turning the coil on in the #2 position and turning it off once it reached #3's position, and at that same time turning on #1, since it is now in #2's position.
The thing that I need help on is the making of the coils and how to wire them up. I want to make a prototype with maybe only 5 coils like the one in the picture so I get an idea of how well it will work.
If anyone can point me in the right direction that would be awesome!!!
I am eager for this to work because this frees up a lot of weight and room since I wouldn't need 4 drive motors and 4 matching gearboxes.
It may not work as I can see the magnetic field's strength may not be strong enough and/or the wheel would spin except it wouldn't give the bot any movement (the wheel would slip). It would take some complex engineering, but I am up for a challenge. I have a cnc machine. So my first step is to prototype. Even if it is not fully functional its still a great learning experience for myself.
MarkT:
I hope they are not plexiglass walls, they shatter.
You mean polycarbonate??
Anyway the problem with magnets is you need nice flat areas of contact for large forces, and wheel surfaces are
not planar.
Magnetic tank-tracks?
If you had magnetic tank tracks you still run into the problem where the ones in contact with the ground shouldnt be on or else the track wouldnt move. you need the links that are on either side that are hovering above the ground to be turned on to move the track and create motion.
THat is a good point that you need flat areas. Do you think it would help if I had smaller coils that were tightly packed together that way the ones I want to turn on would be closer to the flat surface of the steel?
But you have ones about to contact the floor pulling you forward to balance out the
pull from the ones leaving the floor at the rear. If you had flexible magnetic strip for the tracks
that would be even better.
Static friction depends on total force, not area, but more flat area with magnets is automatically
more total normal force. With rubber wheels more contact area isn't usually any more
friction (more robust, yes)
So at first I thought lets make a wheel out of magnets. I quickly took a step back and said, that won't work, because you simply wont move lol.
Actually, I think it WILL roll. For example, as long as the magnetic force is perpendicular to the direction of movement, 15 Lbs of magnetic pull shouldn't be any different than 15 Lbs of weight.
And, hard wheels will have less friction (as long as you're not running over debris). But, the magnetic pull should (hopefully) be more than the 15 Lb weight, and the actual weight will be added to the pull.
I'd say it's worthy of an experiment (maybe with one magnetic wheel, or on a small scale).
Our competitions are held in an arena made up of a steel floor...
The 1st experiment should be to make sure the floor is not made from non-magnetic stainless steel.
That is when I thought, why not "embed" electromagnets into a wheel.
Although that's a very cool idea I have a feeling that it won't make an efficient motor.
MarkT:
But you have ones about to contact the floor pulling you forward to balance out the
pull from the ones leaving the floor at the rear. If you had flexible magnetic strip for the tracks
that would be even better.
That's why you turn off the coils leaving the floor so there is no pull in the opposite direction?
I may have misinterpreted what you meant to say there.
MarkT:
but more flat area with magnets is automatically
more total normal force.
This is why I am thinking the smaller the coil, the more chance of it being flat, i guess you could say. Its like trying to make the coil closer to a single point so it makes flat contact at the single point on the floor, if that makes sense lol. I understand I wont make flat contact with the floor, but I'd like to try it out.
DVDdoug:
Actually, I think it WILL roll. For example, 15 Lbs of magnetic pull shouldn't be any different than 15 Lbs of weight. And, hard wheels will have less friction (as long as you're not running over debris). But, the magnetic pull should (hopefully) be more than the 15 Lb weight, and the actual weight will be added to the pull.
I'd say it's worthy of an experiment (maybe with one magnetic wheel, or on a small scale).
The 1st experiment should be to make sure the floor is not made from non-magnetic stainless steel.
Although that's a very cool idea I have a feeling that it won't make an efficient motor.
That is great to hear! I plan on only experimenting with one wheel to see if its worth moving forward. And yes it is Steel and not stainless.
If the wheel is built in multiple segments, like the armature of a dc brushed motor - and you rewound that armature with many more turns on each pole, and connected them to the commutator such that (say) only 4 at a time at the bottom of the 'wheel', only those 4 as the 'wheel' turned were energised using the original brush set... such that only those in close contact with the ground were energised to give you extra grip.........
ie your 'wheels' are made from old armatures - eg from windscreen wiper motors....
but maybe fat squashy tyres and extra weight might acheive the same much more simply.
Or adding many powerful permanent magnet fixed to the vehicle but a little above the steel floor would acheive the same equivalent of weight without adding mass.............. alternate N and S would be a good idea.
Hah, Allan beat me to the punch, but I was going to suggest just that: hacking an old motor armature and providing power to it as needed through the existing commutator. Seems to me if you energize the teeth in the proper sequence(like a stepper) it would run along the floor. Plus they are already rounded for you!
My thoughts would be that if the tooth that is in most contact with the floor is energized in such a way that the north pole faced the floor, then energizing the adjacent tooth, in the direction of intended travel, to have the south pole facing the floor, would step a smidge in that direction so that both teeth`s pull meets in the middle.
Admittedly, I just had surgery hours ago, and the meds may be clouding my thoughts( even more than normal :-))
But I love your outside the box thinking!
billcat:
Hah, Allan beat me to the punch, but I was going to suggest just that: hacking an old motor armature and providing power to it as needed through the existing commutator. Seems to me if you energize the teeth in the proper sequence(like a stepper) it would run along the floor. Plus they are already rounded for you!
My thoughts would be that if the tooth that is in most contact with the floor is energized in such a way that the north pole faced the floor, then energizing the adjacent tooth, in the direction of intended travel, to have the south pole facing the floor, would step a smidge in that direction so that both teeth`s pull meets in the middle.
Admittedly, I just had surgery hours ago, and the meds may be clouding my thoughts( even more than normal :-))
But I love your outside the box thinking!
Bc
Thanks guys I appreciate the help. We shall see after I get moving with the idea, I'll keep everyone updated.
Cheers!
allanhurst:
but maybe fat squashy tyres and extra weight might acheive the same much more simply.
Or adding many powerful permanent magnet fixed to the vehicle but a little above the steel floor would acheive the same equivalent of weight without adding mass.............. alternate N and S would be a good idea.
regards
Allan
We have a 15lb weight limit so it's best not to add anymore weight than needed, fixed magnets are a good idea, but I've seen other teams bend axles because so much force.
