Chief Delphi

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)
-   General Forum (http://www.chiefdelphi.com/forums/forumdisplay.php?f=16)
-   -   How Fast Can you Safely Climb? (http://www.chiefdelphi.com/forums/showthread.php?t=153871)

Ginger Power 18-01-2017 13:33

How Fast Can you Safely Climb?
 
There are going to be some extremely fast climbers this year. How fast can you reasonably climb without putting the Pilots, the field, and your robot in danger?

For example, say a team can climb in 1 second. Their robot is going to be traveling very fast... they are going to hit the field sensor very hard... how much abuse can the field take?

RoboChair 18-01-2017 13:45

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Ginger Power (Post 1633008)
...how much abuse can the field take?

Never enough.

Looking at you Team 900....

Daniel_LaFleur 18-01-2017 13:52

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by RoboChair (Post 1633020)
Never enough.

Looking at you Team 900....

QFT.

I'm even more concerned hen the winch doesn't stop at the top of the climb

Joseph Smith 18-01-2017 13:57

Re: How Fast Can you Safely Climb?
 
I could see a team that runs into the touchpad and continues running their winch until one of two things happens:
They burn out their motors

OR

Their gearing is reduced enough that they yank the retaining knot of their rope through the davit and fall to the ground.

Teams should plan on having a way to stop climbing when they reach the top that doesn't consist of stalling motors.

Bruceb 18-01-2017 14:11

Re: How Fast Can you Safely Climb?
 
ok I am not a programmer but isn't there a way to sense current draw and shut the motors off when it spikes?

Ginger Power 18-01-2017 14:21

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Joseph Smith (Post 1633030)
I could see a team that runs into the touchpad and continues running their winch until one of two things happens:
They burn out their motors

OR

Their gearing is reduced enough that they yank the retaining knot of their rope through the davit and fall to the ground.

Teams should plan on having a way to stop climbing when they reach the top that doesn't consist of stalling motors.

What happens when the retaining knot is solid, the gear ratios are low, and the rope is rated to ridiculous tensile strengths? Is there a realistic possibility that something on the field could break?

What recommendations do people have so teams

1. Don't burn out climber motors
2. Don't break the field

Joseph Smith 18-01-2017 14:25

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Ginger Power (Post 1633050)
What happens when the retaining knot is solid, the gear ratios are low, and the rope is rated to ridiculous tensile strengths? Is there a realistic possibility that something on the field could break?

What recommendations do people have so teams

1. Don't burn out climber motors
2. Don't break the field

As Bruceb noted, you could have some way to detect a spike in current that the climb motor is drawing, and use this as a trigger to stop running the motor. (I'm not a programmer, but I know that the control system lets you monitor current outputs.) Or, you could set up a system where there is a flexible plate over a limit switch, such that when it is pushed against the touch sensor the plate will bend down and trip the limit switch. This way it could apply the required force to activate the sensor, but stop you from trying to tear the airship apart.

Chris is me 18-01-2017 14:27

Re: How Fast Can you Safely Climb?
 
You know, the rope and target are one of the few things on the field you can be reasonably sure you'll be able to see. Just have the operator stop hitting the "winch up" button.

prozack19 18-01-2017 14:49

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Chris is me (Post 1633055)
You know, the rope and target are one of the few things on the field you can be reasonably sure you'll be able to see. Just have the operator stop hitting the "winch up" button.

I was literally thinking the same thing.

scca229 18-01-2017 15:32

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Daniel_LaFleur (Post 1633025)
I'm even more concerned hen the winch doesn't stop at the top of the climb

This has been my biggest fear after seeing the reveal at Kickoff. I'm hoping this coming weekend will answer a lot of my questions.

Koko Ed 18-01-2017 15:38

Re: How Fast Can you Safely Climb?
 
If you design a robot that breaks the field again and again you are going to get on the FTA and head refs bad side really quickly and you don't want to reside there.

John Retkowski 18-01-2017 15:39

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by scca229 (Post 1633086)
This has been my biggest fear after seeing the reveal at Kickoff. I'm hoping this coming weekend will answer a lot of my questions.

I've seen FRC team build some pretty amazing machines over the past few years. I would be disappointed if a wide spread problem was not being able to stop a motor once the robot has hit a button. One would think the problem could be solved by something as simple as a limit switch and locking gear box among many other (alot of them not very complex :D ) things.

anishde 18-01-2017 15:42

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Chris is me (Post 1633055)
You know, the rope and target are one of the few things on the field you can be reasonably sure you'll be able to see. Just have the operator stop hitting the "winch up" button.

Yeah, as far as I could tell, isn't this a fairly simple solution? Or are some teams unable to stop their winch?

cgmv123 18-01-2017 15:49

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by anishde (Post 1633101)
Yeah, as far as I could tell, isn't this a fairly simple solution? Or are some teams unable to stop their winch?

If it's run by a motor, either the team commands it to shut off or the robot shuts it off when it gets disabled.

Bruceb 18-01-2017 15:53

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by anishde (Post 1633101)
Yeah, as far as I could tell, isn't this a fairly simple solution? Or are some teams unable to stop their winch?

you can only see 2 of the ropes. The third one is on the back side of the gondola.

MrForbes 18-01-2017 15:56

Re: How Fast Can you Safely Climb?
 
The fun part is that the touchpad dome does not illuminate when the robot contacts it, it waits a second....

I love control challenges like this

AdamHeard 18-01-2017 16:04

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Chris is me (Post 1633055)
You know, the rope and target are one of the few things on the field you can be reasonably sure you'll be able to see. Just have the operator stop hitting the "winch up" button.

If they react too early, you don't hit the plate... If they react too late, you've potentially loaded up the entire system w/o breaking anything and it'll be a real pain to remove from the field (or you devastated the touch plate).

Ginger Power 18-01-2017 16:06

Re: How Fast Can you Safely Climb?
 
Obviously the operator can let go of the trigger when the robot reaches the top. My point was that if a robot is climbing very fast, it's going to take skill on the operator's part to stop the robot in a reasonable amount of time. I was looking for reasonable methods of stopping the robot that would be automatic. Limit switches and current sensing are two good options. Are there any other options that can be utilized on a robot?

Richard Wallace 18-01-2017 16:10

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Koko Ed (Post 1633096)
If you design a robot that breaks the field again and again you are going to get on the FTA and head refs bad side really quickly and you don't want to reside there.

^ QFT.

The first time your robot does this, your team will have violated G15-H. Penalties: FOUL; if extended or repeated, then YELLOW CARD; if Head Ref deems that further damage is likely, DISABLED. There had better not be a second time, because if so your team will have violated T03, and will fail most egregiously.*
------------

*See "Bill and Ted's Excellent Adventure."

Eric Scheuing 18-01-2017 16:16

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Bruceb (Post 1633040)
ok I am not a programmer but isn't there a way to sense current draw and shut the motors off when it spikes?

The answer is yes, but you want to do this as a backup, not as a primary stop feature. I say this as a team that used this method last year, and was having anxiety attacks all season about burning out that motor.

Chris is me 18-01-2017 16:16

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by AdamHeard (Post 1633115)
If they react too early, you don't hit the plate... If they react too late, you've potentially loaded up the entire system w/o breaking anything and it'll be a real pain to remove from the field (or you devastated the touch plate).

Well, the plate has a bright light on it, so the "too early" thing isn't a huge concern for me. Too late is a problem, depending on your design - any design is going to need a way to relieve the rope tension or stop at exactly the right time to work. Depending on how fast the hanger goes, you can have a second button to run the winch more slowly when you're near the top.

Alternately, put a vex bumper switch on whatever mechanism is doing the plate contact for you.

Edit: Apparently the touchpad only illuminates when you've reached the 1 second threshold. Thanks, GDC...

Eric Scheuing 18-01-2017 16:17

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Ginger Power (Post 1633116)
Are there any other options that can be utilized on a robot?

Ultrasonics and other distance sensors could work. My team is toying with the idea of running the whole operation on a loop that's activated by the on-board gyro sensing a change in the robot's angle.

Hitchhiker 42 18-01-2017 16:46

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Eric Scheuing (Post 1633124)
Ultrasonics and other distance sensors could work. My team is toying with the idea of running the whole operation on a loop that's activated by the on-board gyro sensing a change in the robot's angle.

Could also use the accelerometer in tandem with that to stop when you reach a certain height.

zinthorne 18-01-2017 16:55

Re: How Fast Can you Safely Climb?
 
This may sound really dumb, but FIRST could put it in the field programming to stop robot communication if the pressure sensor is held for 1 second in the final 5 seconds. I realize this takes the drama out of holding for one second to end the match, but it could stop a lot of problems with motor burnouts. Most mechanisms wont break if stalled for ~one second. Just an idea, but will likely never be implemented.

Lireal 18-01-2017 16:57

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by zinthorne (Post 1633138)
This may sound really dumb, but FIRST could put it in the field programming to stop robot communication if the pressure sensor is held for 1 second in the final 5 seconds. I realize this takes the drama out of holding for one second to end the match, but it could stop a lot of problems with motor burnouts. Most mechanisms wont break if stalled for ~one second. Just an idea, but will likely never be implemented.

The issue would be if a team only had a motor keeping the robot up, it would crash to the ground immediately.

zinthorne 18-01-2017 17:08

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Lireal (Post 1633139)
The issue would be if a team only had a motor keeping the robot up, it would crash to the ground immediately.

You could argue that it would also crash to the ground at the end of the match anyway if all they had was a motor holding it up.

KJaget 18-01-2017 17:08

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by RoboChair (Post 1633020)
Never enough.

Looking at you Team 900....

6-CIM climber you say?

As a serious contribution, perhaps the human players have some use here since they might be able to see what the driver might not?

Kevin Sevcik 18-01-2017 17:13

Re: How Fast Can you Safely Climb?
 
Starting from the bottom, the rope goes through a steel U-channel, which it's held in by 2 pins. Then it makes a 90 degree turn, runs across the top of a square steel tube, and through 2 steel tabs welded on the sides of the tube. There's a pin through the top of these tabs to hold the rope in, the knot rests on the far side of the two steel tabs.

Failure options for winches will too much torque that don't stop at the top.
  • Knot slips/rolls completely off the bitter end of the rope. Rope slips through tabs and channel.
  • Knot tightens or compresses enough to slip through tabs. Rope slips through tabs and channel.
  • Rope breaks. Robot falls, only custom rope is damaged. I suspect this will be disturbingly common with teams using mostly velcro for a rope. I expect field crew to have a trophy wall of 4" long ropes, since they'll likely break at the 90 degree bend.
  • Knot wedges between tabs and bends them outwards. Depending on size, knot may get stuck in channel.
  • Steel channel buckles under load. I'm not bothering to calculate this, but it seems like it's less than the following.
  • One or more tabs shear their welds.

After playing with the touchpad, I think it's unlikely to get damaged. First, there's the channel sticking down that your winch will run into. Please design your climber to jam against this channel before the touchpad. Second, the plate is 1/4" lexan, the bolts it hangs from are relatively well pivoted, and I'm nearly certain you can shove it against the steel plate it hangs from with no ill effect. The most likely failure mode would be shearing the screws that hold it to the channel on the davit, I think.

amesmich 18-01-2017 21:06

Re: How Fast Can you Safely Climb?
 
Assuming someone does not have it geared 10,000:1 so it crawls up an inch per hour, motor current may pop the snap breakers/fuses. There is only so much power available, and since it needs to be geared in a realistic manner that limits how much force can be expected. Still hundreds of pounds and even thousands, but I expect the damage to be done to the robots because of ill designed systems.

gegozi 18-01-2017 22:58

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Ginger Power (Post 1633050)
What happens when the retaining knot is solid, the gear ratios are low, and the rope is rated to ridiculous tensile strengths? Is there a realistic possibility that something on the field could break?

What recommendations do people have so teams

1. Don't burn out climber motors
2. Don't break the field

The pilots can see the field, and they can communicate to the drive team with hand signals.
I don't see why that would be prohibited...

gegozi 18-01-2017 23:09

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Lireal (Post 1633139)
The issue would be if a team only had a motor keeping the robot up, it would crash to the ground immediately.

It doesn't matter if the robot falls after the timer stops.
The rules say that as long as the button is pressed through time 0 and it is pressed for over 1 second, it will count. I'd therefore recommend that you run your winch a little more than the minimum requirement to make sure that even if it does begin to slip or unravel, the button will still be pressed enough to credit the points.

If you're referring to the robot damage, that could be a serious issue.
I talked about this with my sister and she said to use an airbag-type system to prevent robot damage. I would LOVE to see someone build an airbag-type system that is FRC legal.

Either way, I hope this helps.

matthewdenny 19-01-2017 05:49

Re: How Fast Can you Safely Climb?
 
My back of the envelope calculations tell me a 2.5 second 1-CIM climber at motor max power point is very doable. Half that for 2 CIMs.

Koko Ed 19-01-2017 06:45

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Richard Wallace (Post 1633119)
^ QFT.

The first time your robot does this, your team will have violated G15-H. Penalties: FOUL; if extended or repeated, then YELLOW CARD; if Head Ref deems that further damage is likely, DISABLED. There had better not be a second time, because if so your team will have violated T03, and will fail most egregiously.*
------------

*See "Bill and Ted's Excellent Adventure."

Team 1815 at GTCR learned this the hard way, last year, when they impacted the wall hard three matches in a row. The head ref told them to fix it after the second time it happened and when it happened a third time he gave them a red card.

JesseK 19-01-2017 09:10

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Eric Scheuing (Post 1633122)
The answer is yes, but you want to do this as a backup, not as a primary stop feature. I say this as a team that used this method last year, and was having anxiety attacks all season about burning out that motor.

Different anecdote:

The only sensors 1538 added to their bot for the 2015 season were encoders. They used current sensing for limits. Even with all of its complexity, this is what their wiring looked like.

It takes time to develop current-based limits. They don't work if a team decides to try them out for the first time on the robot in week 6.

dirtbikerxz 19-01-2017 09:33

Re: How Fast Can you Safely Climb?
 
Just have the drivers stop pushing the "climb" button, when the bot slams into the touchpad. Since climbers this year (most likely) will only have to be turning in one direction, a simple solution to avoiding having to stall the motors to stay up is just sticking a ratcheting socket wrench on the end of the climber shaft. That should keep the bot from coming back down without having to stall the motors.

MrForbes 19-01-2017 09:40

Re: How Fast Can you Safely Climb?
 
When I read the rules, it appeared that if your robot contacts the touchpad, but then goes back down the rope enough that the touchpad is no longer activated, then you can't get the climbing bonus.

It might be that you want to spend a little time on the control system for your climbing mechanism?

Chris is me 19-01-2017 09:58

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by MrForbes (Post 1633400)
When I read the rules, it appeared that if your robot contacts the touchpad, but then goes back down the rope enough that the touchpad is no longer activated, then you can't get the climbing bonus.

It might be that you want to spend a little time on the control system for your climbing mechanism?

This isn't a universally true statement. You just need to satisfy the two criteria:
  1. Touch the pad for at least 1 continuous second
  2. Touch the pad during the 0.0 second mark on the clock.

I actually can't find anything in the rules that suggests that these two operations have to be done in the same instance of touching the button; I could have missed that though. Point being, if you touch the button at zero seconds, and you've already touched it for 1 second or more beforehand, you don't need to stay up there.

Any number of really simple control system things can ensure you don't immediately fall back down once you touch the button - it could be as simple as a feed-forward gain.

Basel A 19-01-2017 10:09

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Chris is me (Post 1633411)
This isn't a universally true statement. You just need to satisfy the two criteria:
  1. Touch the pad for at least 1 continuous second
  2. Touch the pad during the 0.0 second mark on the clock.

I actually can't find anything in the rules that suggests that these two operations have to be done in the same instance of touching the button; I could have missed that though. Point being, if you touch the button at zero seconds, and you've already touched it for 1 second or more beforehand, you don't need to stay up there.

Any number of really simple control system things can ensure you don't immediately fall back down once you touch the button - it could be as simple as a feed-forward gain.

That would be a good question for the Q&A. I would anticipate that it does have to be the same instance but as you say, that's not specified.

As for control, the easiest way is to (a) press the touchpad using something springy like a bumper and (b) have something mechanical like a ratchet keeping you from moving downward. This combination means you can stop all power but will still be exerting some small amount of force on the touchpad.

Chris is me 19-01-2017 10:18

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Basel A (Post 1633416)
That would be a good question for the Q&A. I would anticipate that it does have to be the same instance but as you say, that's not specified.

As for control, the easiest way is to (a) press the touchpad using something springy like a bumper and (b) have something mechanical like a ratchet keeping you from moving downward. This combination means you can stop all power but will still be exerting some small amount of force on the touchpad.

After reading section 3.9 again, it specifies the three criteria to score are evaluated "at the end of the MATCH", which seems to imply that you have to satisfy the T=0 requirement at the same time you satisfy the >1 second requirement.

Eric Scheuing 19-01-2017 10:24

Re: How Fast Can you Safely Climb?
 
Quote:

Originally Posted by Basel A (Post 1633416)
That would be a good question for the Q&A. I would anticipate that it does have to be the same instance but as you say, that's not specified.

I would think so as well, but all I was able to find in the rules was this:

"If a ROBOT causes a dome to illuminate, but disengages from the
TOUCHPAD, the dome turns off and the associated points are removed from the real-time score."

Let's see what the Q&A has to say about this!


All times are GMT -5. The time now is 03:42.

Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi