Motorized brake

What is the best way to make a single motor brake to stop your robot from being bushed, and to play to better defense?
Lead screw and nut?
Linear slider? (Rack and pinion)
Linkage? (This is only one example, there are many more ways of doing it)
An other design that I can’t think of?
I began to wonder this after seeing this thread.

Using a worm gear to press a pad into the ground would probably be the most space efficient and effective way to utilize a motor.

Another way is via software and the motors you already have and not make yourself any heavier.

A PID control on your motors to try and stay in the same position works pretty well too. One of my teams calls it the “you shall not pass” strategy by pushing a button to try and remain exactly where you are. You may want to couple with a rotational PID too to keep your shooting angle.

You can switch to a different set of PID constants for the hold versus drive that ups the P or D contributions. So any movement away from 0 error on the encoder results in an overshoot back if untouched. But it results in a pushing force back if the other guy is pushing you back. Increasing the P value can accomplish this to magnify any slight movement away from the desired spot and once you pass the desired spot it backs off. D will be the rate of movement away as the compensation.

This can lead to motor burn out though as your motors may want to go pretty high motor values to remain in place. But isn’t that what you are doing when you manually sumo wrestle robot style?

However, a piece of metal driven down with the anti slip mat on it is pretty effective too… A wider surface area makes for a nice frictional force for the opponent to overcome. But you have the time it takes to get it in and then back off and maneuver yourself back to your sweet spot of shooting. Software control of “this is a good spot” which is the same as “you shall not pass” works to get you back to the right spot for shooting.

From an event producer standpoint, not a big fan of jabbing metal into my competition floor. I’ve seen a number of teams use the positional PID as a strategy.

Plus just think of the points you’ll score with the judges when you talk in your interview about it!

Yes flat metal brakes, not jabby metal brakes that puncture the foam tiles.

Nice flat surface with anti slip mat. Like team 62 had last year at worlds. But a bigger surface area.

I want to simply be able to sit there and not get pushed around. We have a quite fast drive, that I would expect to lose and stall out in most pushing battles. And an other navigator robot has a 2 motor drive and would need to play defense in some situations. So I don’t think that PID is really an option for us.

(Only shown for a spit second)
I will take that into consideration. Would something like the Texas Discobots 2587Z’s break be a better option?

The pad with anti slip seems like it wouldn’t damage the tiles, but I’m a bit worried about where the other end of those screws you see are, are there nuts sticking out the bottom of the brake?

Umm, if you flipped the screws over so the screw head is down (vs the sharper bolt end) or covered by some non-skid then OK.

And since this thread has gone on, the word break (like in the title) has to with damage, like will this break Foster’s field tiles.

The right word is brake, as in can I deploy a wheel brake?

Thanks!!

Is there any reason that I couldn’t use a lock on the wheels (Traction wheels)?


Like this hang lock from 7793R back in tossup.

It’s certainly space efficient. The only major problem is it’s really slow, so by the time you’ve deployed your break, you have already moved a good ways away from where you were trying to shoot from.
I suppose if you had a super light robot it would work well, because you could gear it for high speeds.
We built this at the start of the season:

It lifted the robot nicely, but it was kind of a prototype so we never perfected it.

If a team attached multiple layers of matting to their brake mechanism, then it’s unlikely it would damage the mats. We did some tests on this earlier this year. Also if the weight was spread nicely on a large plate of metal, (with matting) then it’s even less likely it would damage the matts. Still, if the robot was really heavy it might be a different story.

A turbo motor spins at 4 rotations per second. I don’t know the threads per inch on the vex lead screws, but 4 rotations should be at least 1/4 in, enough to get the brake off the ground.

It would certainly get the brake off the ground, but would it put enough force on the ground when deployed?

That I do not know. I see your point.

Yes matting is excellent. We’ve just personally seen brakes jam into the floor tiles with just the sharp profile of a linear slide piece holding the robot. It held but left a nice divot in the foam tile of the shape of the linear slide metal. Grrr.

It was a few years ago in sack attack. They have graduated and are in college now.

I think it could be calculated. But it depends so much on the weight of the robot that there’s probably not much point in doing a blanket calculation.
What if it was deployed with rubber bands, and then pulled back up with a motor. That way it would be instantly deployable. It would take a small amount of time to pull back up, but the main thing is getting is down quickly. Also, I wonder if an over tilt mechanism could be used, similar to this autonomous switch:

It might allow for quick deployment and removal, with one motor to pivot the “switch.”

Your images aren’t showing.

Maybe using a slip gear and an IME?

I can see the images, so it might be something with privacy settings acting up. I’m working on fixing it.

A slip gear sounds like a good idea. Sort of like a launcher, only it fires at the ground. I think it would need some sort of dampening system, otherwise I can see the robot jumping off the ground for a second. (Brings to mind the old pogostick discussion :D) It would also need a lot of matting, as a quick fire at the ground would have a lot of potential to damage the tiles. Maybe it could be slowly released using ample friction?
Edit: Slow release defeats the entire purpose. Never mind.

Could be an option, but I personally would not like doing this, simply because in the case of failure (motor, structure breaks, programming screw up, etc.) the brake would be jammed down and you can do absolutely nothing for the rest of the match. If a different mechanism were to break, you won’t be able to use the brake, but at least can drive for the rest of the match. It’s not like in vehicles were you’re in trouble if the brakes don’t work (truck air brakes are designed so if you lose air pressure the brakes jam on).

I think a hammer, a radial saw, and Tombstone would probably do the trick.
Here you go.

The correct word would be brake, not break. I just wanted to clarify this so we don’t have everyone using a word associated with destruction to describe a device for slowing down a robot.