Author Topic: Post WPI discussion  (Read 1806 times)

Louis L

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Post WPI discussion
« on: March 14, 2017, 12:15:42 PM »
With the loss of a few days of work since the WPI event, I'm putting down some thoughts so that we can expedite the process of making changes (if any) heading into RIDE. The original intent was to have a meeting to discuss this but this snowstorm isn't helping. Since you all have the day off, let's see if you can add to the discussion via the forum.

A few students showed up on Sunday so we held a mini review. Below are a summary of the ideas that came out of the discussion plus some of my personal notes. Please feel free add to this discussion.

  • If the tip on the Lift comes off and gets stuck on the Gear, don't waste time removing it; just use it as-is with the tip facing up in the geartrain so you can turn it.
  • Practice! Drives and operators need to practice ASAP. The more practice the better. We need to modify the test-bot to better mimic something that can place a Gear.
  • It seems many teams claimed they could do the center gear in auto but failed. If we can do it, we should just go ahead and try it. We need help from the scouting team to find out which teams are truthful and actually delivering on their auto claims.
  • replace yellow extension cords. Both have dead outlets. Worse, at least one has an intermittent outlet. We should at the very least tape over the bad ones and also add a 1:3 (from the BSB box); that would be cheaper than buying new cables (they're not cheap). [I checked them out and they seem to be ok. One has a taped receptacle that is know to be bad. I added two 3:1 green expanders to the kit]
  • We lucked out that team 4041 was from Maine and didn't get to their pit until the evening. Otherwise we would have had a much tougher time setting up the pit. For RIDE, we probably won't be that lucky. The loading dock there is pretty limited (2 or 3 cars max). We should try and get the Pit stuff in first, get it set up, then bring in the robot and the rest of the gear. Or find an area to pile our stuff while the pit gets built. Either way, we can't have everything deposited in a 10x10 space and still have room to work.
pre-flight checklist.  We've talked about doing this for years and it's about time we did. There's no excuse for not doing it, especially with 5 people on the drive team. The core problem is that the squeaky wheel gets the grease. In other words, things that break get noticed and we fix them. But things that don't fail get ignored and when they fail, we're surprised. We should treat everything as if it will fail and therefore check them all. We've been bitten by this before; more than once.
  • Check all nuts and bolts.
  • check air pressure if using pneumatics
  • check bumpers / velcro
  • check servo & positions
  • check wheels for debris
  • check electrical connections - be careful here not to be aggressive on pulling cables. Check by sight first.
  • Selecting autononous modes via the driver station is something we did last year. A few times, the value set did not pass to the robot code but it was not reproduceable and the problem was short-lived. Well it seems to more pronounced this year. Should we go back to the old switch box? We would need a minor code change needed.
CLIMBER - this was half of our mealticket to the finals. Our bread.
  • replace any worn velcro on rope
  • replace worn velcro on drum
  • improve ratchet on climber so can't fail
GEAR - and this is our butter. We had numerous issues with this. It's a simple contraption in theory but a PITA to implement and have it last. Some proof-of-concept was done on Sunday for improvements.
  • Move the camera for exclusive use by the Gear device. Stav says he wasn't using the camera to drive and we sure could use it on gear placement. What's the best vantage point? Where do we have room?
  • The servos are wearing out. Ryan took one apart and half the teeth have sheared off. While they are rated for 10 inch-pound (times 2 units at 5 inch reach for a load handling capability of 4 pounds), it's likely that between the struggles of lining up the robot and the human player pulling on the gear at the wrong time, we're putting occasional strain on the servos that easily exceed its rating. One option is a pneumatic system. A pre-charged tank at 30 pounds can deliver 35 activations, far more than we would ever need. If we stick with servos we need to decide soon so that I can order replacements. At $40 each, I want to make sure we'll be using them. Would moving the camera, this getting better placement, be enough to avoid strain on the servos? [Ryan decided that any change could not be made before RIDE so 2 additional servos were ordered].
  • Add visual indicator for Pilots. We talked about this some time ago. Something easy to see and interpret so the Pilot knows when to pull the Lift. It seems there are more bad Pilots than good and we need to make our system idiot-proof.
  • Replace pusher if we swap out the servos. Have it push a larger surface area.
  • Replace doors. Not as critical. At the very least, make a few spares if we know we'll be using them again.
  • In terms of usage and strategy, for left and right driver stations positions, use the opposite Lift (right and left respectively) for best view of the Lift peg.
  • cut off part of intake to allow gear to slip under. This prevents damage to the intake. But is this desirable (see chassis)? [We will raise the intake so that it doesn't catch irregularities on the carpet. But we will add a reinforced backing so that gears do not go below the intake. They will be pushed along. No gear will get stuck beneath the robot.]
  • Lower the side skirts to block gears from getting under chassis. Is this really an issue? If this is done in conjunction with raising the intake scoop, what happens if a gear goes under the intake and gets stuck inside & under robot?
  • Add wheel encoder for autonomous. We'll use the touchless encoder we already have and use it on one of the drive wheels. This is for autonomous. It'll be much easier to program than trying to figure out speed/time requirements. [This was tested on the bench.]
  • There's a new design in the works. Parts are on order. With any luck, it'll be ready in short order. It will also be lighter than the current hopper. The target goal is a non-rotating shooter. Shot distance is controlled by wheel speed. Side wall hopper position is the primary shooting spot.
how do we staff the next event?
  • The pit was too crowded. Of course it wouldn't be if we didn't have to make repairs. Let's trim the size of the pit crew. Also let's be smart. If there's work to be done, thin out the crew. Otherwise, we can have more people. Always be able to adjust with the conditions.
  • We will also be trimming the pre-scouting crew on day0
Robot cart
  • Add one of the old battery chargers to the robot cart. [We can just add this to the cart. No need to mount anything.
  • Remove audio amp but keep arduino for lights - needs new programming. [The circuitry has been disconnected from the battery cable so it can't be used. But it is still mounted in place. The audio amp has a bad speaker output connector so it's not useful for other uses! We'll deal with this some other time.]
« Last Edit: March 16, 2017, 10:35:13 PM by Louis L »

Ed B

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Re: Post WPI discussion
« Reply #1 on: March 14, 2017, 01:26:23 PM »
Climber ratchet: we beefed up the climber frame part that holds the ratchet shaft. This seems to have solved the problem we had during unbag testing. The problem we had in the final match at WPI was that the ratchet release mechanism disengaged the ratchet due to some collision on the field during the match. I believe this can be resolved by putting on a stronger spring. The one on there now is pretty weak.  We can do some experimenting to check this hypothesis and bench test under load.

Pusher servos... We are using 4 of those servos on the gear mechanism. I think the door servos get beat up more than the pusher, and they have been fine. My guess is that the servo we had to replace was defective from the beginning. Is there evidence that others are failing?

Gear doors... We should replace them with more robust plastic and make plenty of spares. I would also like to consider modifying the bearing setup so that the pivot shaft on each door is rigidly attached to the door and turns in the mounting blocks. Seems like a simple change and will keep the doors coplanar more easily.

Climber... The velcro is holding up surprisingly well, but I agree replacing would be a good move. It seems like we could also add a taut nylon string guide on either side of the climber to keep the rope from getting into the nooks and crannies next to the climber. Should make acquiring the rope quicker.

Intake vs gears... Scary to raise this but not the rest of the chassis and end up dragging gears around. I see no sign that gears are getting past the chassis. alternative... Raise the scoop but put a hard barrier behind it that gives a gear on the ground a place to go when we are at the load station, but does not capture it under the chassis, so it it comes back out when we back out. May be a little risky for fouls, though.

Cart... Check if the robot is being supported by the bumpers and if so, add a spacer in the wheel niches to raise it up a little. Also, add blocks to raise robot enough to run the wheels while on the cart.

Louis L

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Re: Post WPI discussion
« Reply #2 on: March 14, 2017, 02:18:48 PM »
Ed, regarding the pushing servos - so far we've replaced 2 of them and the 3rd is already feeling like it's shot. Of the 2 pulled from service, one has missing teeth (was opened up). The other looks ok, though was not totally dissected. So given that every servo (3) that's been used as a pusher has been negatively affected, I doubt it's a manufacturing defect. At 60% failure overall and 100% failure as a pusher, more likely we're not using it correctly.

Pablo C

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Re: Post WPI discussion
« Reply #3 on: March 14, 2017, 02:30:46 PM »
Other Pre-Flight Checklist Things
  • One of the most important checklist item has nothing to do with our robot: Make sure our alliance pilots know exactly how our gear mechanism works! Many pilots tried to move the lift while we were still placing the gear. Make sure they only use the lift after our robot has backed out.
  • Check box pin is secure & string is stowed
  • Check and recheck Joystick/controller connections. If they fail in the match, press F1 to restart the joysticks! THIS STUPID ERROR COST US A MATCH!
  • Seems trivial, but make sure there's a fresh battery
  • When loading gear, make sure a spoke is directly down? (Not sure about this in the future, see below for more details)

Other things to do before RIDE
  • Right now we have 2 ropes with the correct bottom velcro pattern. Fix the other two so that they all have the right velcro end and all are the right length.
  • Finish auto-gear. I know the software peeps have been working hard on this for a long time, and I'm realy exited to see it work in the competition! One thing to note is that we were told to load the gear with a spoke facing directly down, and in two matches auto-gear would've worked if we loaded the gear spoke up. This happened once in the center and once on the right. I'd like to discuss if this is worth changing or if updated auto-gear code will fix this issue.

Random Tips for Drive Team
When the driver goes to get a gear, the operator doesn't have much to do, so make sure you don't zone out. The driver should move very quickly across the field, and then moving very slowly when alligning for placing the gear. What Stav and I did was he made a complete stop before alligning for the gear, at which point I opened the gear flap to the half way position. This seemed to work very well. The operator needs to know when is the right time to push (I know I did it a bit too early). After the gear is pushed onto the peg, it will swing for a bit since the peg was places into a hole in the bottom of the gear. The driver shouldn't dive away immidiatelly, as are robot will prevent the gear from swinging all the way off the peg.

Stav also became really good at pushing gears/balls out of the way when getting or placing gears. This will be extremely useful and I suggest practicing this in particular!

Finally, visibility is much better than I thought. The lifts are front and center, and the rope will never be on the opposite side of the field. The feeder stations can be a bit tricky if you aren't on the feeder station side, but you can move left/right depending on if you are in the center or the far side to see around the airship. I ended up being to the left/right of Stav depending on which side he needed to be on in order to see the feeder station.

Just be calm and move slow when alligning to place a gear or climb. Nothing is more satisfying than moving the left joystick up and knowing you'll climb with 10 seconds to spare!

Louis L

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Re: Post WPI discussion
« Reply #4 on: March 16, 2017, 12:06:13 PM »
Another thing we need to do:

  • Lots of practice for Lydia and Dasha for chairman's award
  • Make more buttons
  • Make a few more hats
  • We have a bunch of goggles for the hats. Need to "age" them and hand them out
  • Hand out the rest of the team shirts
  • Get the rest of the NE First consent forms.
« Last Edit: March 16, 2017, 12:10:23 PM by Louis L »

Stav Z

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Re: Post WPI discussion
« Reply #5 on: March 22, 2017, 09:33:03 PM »
Here's my checklist - I ordered it based off of priority, please add anything:

Replace battery
Check bumper screws
Check bumper velcro
Check climber ratchet
Inspect the velcro on the rope
Make sure pin is in
Check pixy (If not working re-teach it)
Visually inspect the wires
Make sure wooden pieces in the gear are firmly attached
Check servo positions
Check wheels for debris
Check cracks on gear door
Hand tighten bolts

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