Disk brakes

[Lil' Lavery]

Keep in mind that there are other, possibly cheaper, methods of braking, including one build into the Victor speed controllers (see what 111 and several others did last year). For a different physical method of braking, look at 25s drivetrain.

[Viper37]

Originally Posted by Lil' Lavery

Keep in mind that there are other, possibly cheaper, methods of braking, including one build into the Victor speed controllers (see what 111 and several others did last year). For a different physical method of braking, look at 25s drivetrain.

The victors use power to slow down the robot. If one were to use say a solenoid to open a precharged air loop, which in turn powered a disc, it would use virtually none.

[Jeff K.]

I think a disk brake to control more than one mechanism would be interesting if used to control say...a differential like thing to separate power to two or more different mechanisms from one motor. I agree with Sean, they aren't as useful in the drivetrain as a mechanical locking mechanism in the gearbox itself like 25 had this past season.

[Arkorobotics]

Disk brakes sound really inefficient for a FIRST robot. Why not just take the (+) and (-) wires and have them touch (I am not giving away any concept designs, just an ideal concept). Take a motor and spin the shaft. Now connect the two wires together and try it again. It would be a lot harder, and even harder when you have that going through a gearbox.

[Madison]

Originally Posted by Arkorobotics

Disk brakes sound really inefficient for a FIRST robot. Why not just take the (+) and (-) wires and have them touch (I am not giving away any concept designs, just an ideal concept). Take a motor and spin the shaft. Now connect the two wires together and try it again. It would be a lot harder, and even harder when you have that going through a gearbox.

This is how the breaking feature on the Victors work.

[Viper37]

However some people may want more braking power then that.

Another robot will certainly not have very much of a hard time pushing 2/4 motors on a transmission, especially if it already has the momentum going for it and it is using the same type of drivetrain.

[Arkorobotics]

Originally Posted by M. Krass

This is how the breaking feature on the Victors work.

Woah! Is it like a programmable thing? Has his been around for a long time? I never looked into detail about the Victors.

[Joel J]

I'm looking at the DeWalt transmissions. Does the anti-backdrive pin on these work well/reliably? Sounds like a good way to hold up an arm.

[Madison]

Originally Posted by Arkorobotics

Woah! Is it like a programmable thing? Has his been around for a long time? I never looked into detail about the Victors.

There's a jumper on each Victor that allows you to decide if you want to set it to brake or coast. Brake is as described, while coast is what most folks use.

Teams have, in the past, created a servo-driven mechanism that allows them to switch between the coast and brake modes in the middle of a match.

Edit: Also, apparently you can program it to switch back and forth. You learn something new every day

[Joel J]

Last year IFI pointed out that the jumpers on the speed controllers could be wired to a digital IO port, allowing you to control in software the mode the speed controller was in. It made sense last year, as a team would have been able to enable brake mode, if the robot started to go in the direction opposite the one it was heading in as the match ended (WHILE DISABLED!). That is, you could have the robot coast up the ramp, and then not slide back down (if the dynamic brake was strong enough).

[Lil' Lavery]

Originally Posted by Joel J.

Last year IFI pointed out that the jumpers on the speed controllers could be wired to a digital IO port, allowing you to control in software the mode the speed controller was in. It made sense last year, as a team would have been able to enable brake mode, if the robot started to go in the direction opposite the one it was heading in as the match ended (WHILE DISABLED!). That is, you could have the robot coast up the ramp, and then not slide back down (if the dynamic brake was strong enough).

And you had enough traction.


The essential point that I was making is that the Victor brakes are almost always good for use in a drive-train in FIRST. I'm willing to bet that one of the robots involved in the pushing match (either yours or the robot trying to push you) will lose traction before the motors back-drive in brake mode. Especially considering a vast majority of pushing doesn't occur head on (a great deal of it is rotational in the world of FIRST, something that a braking mechanism that locks the wheels won't help with). If you want a system to prevent torqued out of position, it would have to be in contact with the playing field rather than the wheels.
Mechanical brakes (such as disk brakes) may be a valid solution for other aspects of the robot, such as arm and shoulder joints.

[Joel J]

Originally Posted by Lil' Lavery

And you had enough traction.


The essential point that I was making is that the Victor brakes are almost always good for use in a drive-train in FIRST. I'm willing to bet that one of the robots involved in the pushing match (either yours or the robot trying to push you) will lose traction before the motors back-drive in brake mode. Especially considering a vast majority of pushing doesn't occur head on (a great deal of it is rotational in the world of FIRST, something that a braking mechanism that locks the wheels won't help with). If you want a system to prevent torqued out of position, it would have to be in contact with the playing field rather than the wheels.
Mechanical brakes (such as disk brakes) may be a valid solution for other aspects of the robot, such as arm and shoulder joints.

My post was a follow up to M. Krass's.

As for what you are saying about brake mode: it is not that strong. It does provide some resistance to motion, but not alot. Brake mode seems good for allowing the robot to stop on a dime, and also for helping to keep an arm stationary. Break mode may not help much in a pushing match.

[Lil' Lavery]

Originally Posted by Joel J.

My post was a follow up to M. Krass's.

As for what you are saying about brake mode: it is not that strong. It does provide some resistance to motion, but not alot. Brake mode seems good for allowing the robot to stop on a dime, and also for helping to keep an arm stationary. Break mode may not help much in a pushing match.

The 2nd half of my post was a generic address to the topic as well, not specifically at you (just the initial traction comment). But the brake mode works very well from what I have heard (and determined playing against it) during pushing matches. I don't believe that 116 has ever implemented it though, so perhaps there are quirks that I didn't know.
Regardless, a vast majority of pushing in FIRST does occur rotationally though.

[Jay TenBrink]

If you have potentiometers or a similar devices to measure the position of your wheels, you can program in a reactive braking feature that we refer to as “dynamic brakes”. When the robot is at rest and you want to stay put, the dynamic brakes are activated. The controller senses when a wheel is beginning to turn and applies just enough current to the drive motors for that wheel to keep it stationary. This can work on each side of the robot in opposing directions to keep you from being spun around.

These dynamic brakes only work when you have power, so they won’t keep you on an inclined ramp at the end of a match. They are, however, lightweight (only software) and effective in keeping the wheels from turning. The limit to the staying power is the traction between the tires and carpet.

Jay

[ChuckDickerson]

Originally Posted by Arkorobotics

Woah! Is it like a programmable thing? Has his been around for a long time? I never looked into detail about the Victors.

The brake/coast jumper has always been on the Victors. Just move it from one position to the other. I think it usually ships in the coast position by default so you may have never noticed it. If you connect the jumper back to the robot controller digital I/O (switches) then you can program the Victor to either brake or coast at will.