What strategies are you using to stop climbing the rope after the button is pressed at the proper pressure? Are you planning on a manual stop? A pressure plate stop? A stop based on stall torque? It seems to me that there is a very small window to stop the robot from applying to much pressure on the plate. How are you teams trying to address this issue?
Honestly the best option seems to be driver control. It’s a huge light. If they can see the rope well enough to grab it, they can see the touchpad light.
[strike]I tend to agree with the conclusion, but I don’t agree with the methodology given that one davit is on the far side of the airship from the alliance. That will require a pilot to spot, or some kind of smarts.[/strike] I had it backwards.
Our plan so far is to use a gyro to detect when the robot is angled up at more than, say, 5 degrees. Then we’ll use an encoder on our climber winch to find our height, and stop when we hit the pad. The issue we’ve come up with is that the rope won’t always wrap in the same path, so the distance you climb on each revolution will vary slightly. We’re planning on using a velcro strip though, so this shouldn’t be too bad. If it does end up being intolerable, we’ll probably put a limit switch on the front of the robot to detect when we hit the plate and use the encoder to then climb another inch or two.
If I’m looking at the manual drawing correctly, one of the davits is directly facing the alliance, not away from it. The other two are on the sides adjacent to the ladder, which is on the far side of the airship.
There is a 1 second delay between triggering the plate and the light activating.
that is plenty of time to break components at stall or burn up motors.
i don’t have any testing to support it but i assume that with the can talons it will be super easy to detect the current spike once you hit the plate and then shut down the motors. it appears like a simple solution to me until testing proves otherwise
I think you are looking at it wrong. Each team has a clear view of one of the davits. Teams just need to climb the rope that corresponds to their view.
Don’t, if you gear a CIM motor for optimal climb speed you should be able to stall for at least 30 seconds. The pressure plate has a metal U channel that should prevent you from damaging it anyway and while you may worry about it I’m sure FIRST knows plenty of other teams will test its limit. No need to over complicate things.
You were right, I was wrong. Enjoy your rep. 
The light doesn’t turn on until after you’ve pressed it for one second.
Going to just have analog manual control of the speed of the climber, slow down as you get to the top, press it down firmly, not really worried. This shouldn’t be hard.
A suggestion someone on my team had was to measure the current draw from the climber motor, and when it spikes past a certain point, you know you’ve hit the top of the rope and are pressing the button down.
If you do this, make sure it’s a timer to make sure you’ve pressed for >=1s.
You got to make a stop mechanism so you don’t slide back down after time is stopped. One the match is done the rope points are calculated, so you got to keep up until the points are GIVEN to the team.
According to Figure 3-21 in the manual, teams only need to be touching the touchpad for a split second once the match finishes (assuming you were pressing it for longer than one second) in order to receive the points.
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.
Step 2: Test
Step 3: Test Some More.
Current through the motor is responsive and reliable to read and react upon. Getting it from the PDB is one of the best things added to the control system in recent years.
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.
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!
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).
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