Sunday, February 21, 2016

Robotics Challenge 5: the Eleventh Hour

This will be my last entry on the team.
The last week of build season is the most intense. Monday we don't have school and all hands in team 3840 are working furiously. Saturday is the practice scrimmage at a local high school against forty other teams, and we haven't seen the robot move yet. We sacrifice the manipulator arm on the top left because the pneumatic gauges and a safety light need to be mounted in plain sight, and the door arm aisle is the only spot left. By dinner time, it's done enough to test the essential systems. 

Drive train comes first. The custom, neoprene-like treads grip fantastic, rolling over any obstacle we place in its path without slowing. The spring suspension keeps us rolling without a hitch. However, the driver discovers problem. The treads grip the carpet so well that we can't turn in place. This will mean major redesign. At least we have the ball grabber/shooter arm. 

The software folks begin by calibrating the limits on the arm. Once it has been raised all the way against the frame, a mentor asks the driver with the joystick to lower the arm. The gears grind further up. Unable to break the aluminum frame, the powerful motor rips its own screws out of the base. The arm is ruined. We all stare in shock for a while. Worse, when the head mechanic looks up the specs, we have to use a newer, bigger motor to legally replace it. Back to square one.
There is no time for calibrating the webcam. Any use of the camera for autonomous piloting has been shelved indefinitely. With the changes, we no longer have a viable mount point. The bot can still be a manual-controlled, defense-running, high-scoring machine by scrimmage. Not a mechanical expert, Pierce worked on sewing the bumpers and updating the pneumatics diagram, and adding to the list of materials used.
Tension mounts until Friday evening at 7. Ginger testing shows both drive and shooter can work again. By 8, we travel to the local town hall. The bot does so well with individual obstacles, we line four in a row up and blow over them. Cheers. We shoot a ball into the low goal at range. The room isn't high enough to assemble the high goal, but I stand five feet in front of the bot with a tape measurer until they peg me three times in a row. Then, they test the turning. Nuts fly off, and they halt the bot for repairs. We didn't bring all the tools, so it takes longer. 

During the fifteen minutes, we haul out the conquered obstacles, and set up the portcullis gate, a major manipulation challenge. I'm walking out to the trailer for the third time when I see the bot squeeze under successfully. Now people are taking turns driving to get experience--the reward for six weeks of labor.
That's when my son runs over shouting that he needs a paper towel. I lead him to the bathroom where he explains that he's cut his hand. I help him rinse off the gushing blood and see immediately the jagged wound is going to need stitches. What did he cut it on? The underside of a table top at the town hall. I drop everything, leaving my camera and gear there, and rush him to the ER. Four stitches later, we get home around eleven. He'll get to drive it tomorrow at the scrimmage.

The defenses we spent two weeks constructing got about three hours of use. A few of them will survive to visit the fair, but the rest will likely be scrapped now to make room in the shed.

Saturday morning, my son and I get up around six to arrive at the team work area before seven. We have minutes to load a dozen supply and tool boxes as well as the bot into the trailer. As we walk into the metal shop, we see something horrible on the floor. The bot is flipped on its side with an entire track disassembled. The shooter arm is duct taped in the up position. We talk to the guys who worked well into the night. After the trailer is packed, we leave early for a Menards along the way. We arrive at the school just after eight and the three specialists spent until lunch repairing the broken systems. Mr. Diers, a proud grandfather, is the metalworking mentor assisting Danny.

Everyone at these events is open and friendly. I scouted other teams and found out that everyone with machine vision used a special version of openCV compiled for our camera. When I attempted to download this for ours, I discovered that the school's network wasn't secure. My laptop behaved strangely, and is still in virus recovery mode, days later. Any hope of integrating vision is dead.

When we were finally ready to test the drivetrain, the arm was still duct-taped up. The first match, our bot cleared the first hurdle in a blur. Suddenly, it lacked power and died about a minute later. The repaired track had been reassembled without spacers. Back to the pit. They refixed the track and the arm in time for a late match. 
The event only lasted until four. We would only get a few more chances to play. We couldn't calibrate the software for the new arm in time, so they used manual control on the arm. In the game, the joystick wouldn't launch the ball, and the drivers spent the remaining time trying everything to shake the ball loose into the goal. No luck. Only after the last game did we discover that dropping the arm to the ground without software support dented the ball holder and jammed the ball too high to be ejected. 

I am consoled by the fact that very few bots did well at the practice. Only one bot consistently scored three goals a match, and even they had jams. Some bots got stuck on the obstacles or broke course elements as they ran amok.

Before we could load the trailer and go home for repairs and dinner, the inspector came by. We were last on her list because we had been in the pit or matches all day. She liked how clean our electrical and pneumatics boards were and complimented us on the diagrams. "If only everyone made it this easy." Then came the list of other changes we need to comply with code at the Duluth tournament the first week of March. We're not taking off the two work/school days to travel with them to the tournament, but we wish 3840 all the best. They're a veteran team and have a night and two days to fix everything, plus the first day of practice at the tournament.

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