Climb Stopping Mechanism

[Chris is me]

Depending on what T=0 means, you don't NEED to hold your robot on the button after power is cut, just as power is cut, provided you have already held the button for >1 second. If your mechanism can't do that, it's not like prior years where you can't get the points at all, it just requires more commitment in advance and eliminates last-second scoring.

[Kartoffee]

Our team is using a hex shaft, so we will include a 1/2" ratcheting wrench to help us climb. This was seen to be effective from Ri3D 1.0 and our team is worried that our bot might fall after the buzzer (or at least glide down, which still isn't safe).

I've changed my opinion since the reveal. I thought that it would be stronger to use a single grabbing motion (like the 2013 pyramid climbers), but I've noticed that you would need to dedicate a huge portion of your bot to that.

Our team is using a type of winch. It's not an original idea, but our testing shows its effectiveness. We are quite excited to be climbing this year.

Good luck all!

[mentorDon]

According to the 2015 FRC motor information sheet, a CIM motor pulls 133 amps at stall. Well above the allowed 40 amp breaker allowed per motor under rule R56 Table 8-3.

[Chris is me]

Originally Posted by mentorDon

According to the 2015 FRC motor information sheet, a CIM motor pulls 133 amps at stall. Well above the allowed 40 amp breaker allowed per motor under rule R56 Table 8-3.

133 amps at stall at full voltage. If you stall the motor at much less than full voltage, it will draw significantly less current as well. This can allow you to hold position while the robot has power (but not after power has been cut).

[MrForbes]

Originally Posted by JesseK

Step 1: If your climber is a winch, get rid of all of your sensors and use the PDB's built-in current sensors. When Current / Applied Voltage > a ratio (we're using 60A & 12V, so ratio of 5) then disable the motor from going in that direction for N milliseconds.

I'll get our programmers on this....

thanks!

We were going to just slow down at the top, and stop after we visibly moved the touch pad up as much as it takes to get the light to go on (practice day, you know). But the current thing looks like a fun way to keep a few students busy for a few more days

[tr6scott]

We have an encoder integrated into the climber. We plan on monitoring the current to detect when the climb starts, and set a stop distance based on that start point. The operator will have the ability to jog higher if we stop too soon, but hoping this approach leads to automatic climbing.

Still untested theory at this point. Fingers crossed. Would like to have working repeatable solution by week 1, we are going to need it.

[6101 Robert]

I think the easiest solution is to simply use the motor controllers to sense when the motor is stall. This is what 6101 is doing. The Davit has a C-channel piece to protect it in brief high-stress situation and the 40A breakers wouldn't pop immediately. I don't see any reason why this wouldn't work.

To prevent gliding, we are using a ratchet head on the winch similar to Ri3D 1.0.

[waialua359]

This shouldnt be too hard.
Once you see the light go on, dont drive the lift anymore.
We plan to use a simple ratchet to prevent it from backdriving.

[AdamHeard]

Originally Posted by waialua359

This shouldnt be too hard.
Once you see the light go on, dont drive the lift anymore.
We plan to use a simple ratchet to prevent it from backdriving.

Will you have the ability to disengage the ratchet under load?

If not, what keeps you from effectively clamping onto the field when waiting the 1 second?

[waialua359]

Originally Posted by AdamHeard

Will you have the ability to disengage the ratchet under load?

If not, what keeps you from effectively clamping onto the field when waiting the 1 second?

Sorry, I'm slow. I dont quite follow?

[Daniel_LaFleur]

Originally Posted by waialua359

This shouldnt be too hard.
Once you see the light go on, dont drive the lift anymore.
We plan to use a simple ratchet to prevent it from backdriving.

The light does not go on until a full second after the plate is pushed.
Hope your knot holds.

[waialua359]

Originally Posted by Daniel_LaFleur

The light does not go on until a full second after the plate is pushed.
Hope your knot holds.

Yes, that part we knew and it will hold.

[JesseK]

Originally Posted by Daniel_LaFleur

Hope your knot holds.

I'm missing something here - isn't this something everyone has to worry about?

[Daniel_LaFleur]

Originally Posted by JesseK

I'm missing something here - isn't this something everyone has to worry about?

Yes, but if you wait to stop your winch until AFTER the light comes on you will be putting the full power of your winch + the weight of your robot pulling on the rope for that second.

That's probably a decent amount of force (at least 300 lbs)

[waialua359]

Originally Posted by Daniel_LaFleur

Yes, but if you wait to stop your winch until AFTER the light comes on you will be putting the full power of your winch + the weight of your robot pulling on the rope for that second.

That's probably a decent amount of force (at least 300 lbs)

Hence the need for sensors.