Posts Tagged ‘ design ’

Raiderbot X, 23 Days to Robot Ship: Lego Minibot!

Minibot proof of concept out of old Lego parts. The purple arms push against the pole, which angles the wheels into the pole to create a horizontal vector just strong enough to keep the bot on the pole. Took about two hours to make.

The bot is climbing up a 40 inch metal pole that is embedded in the concrete floor of our garage (for reasons beyond my imagination). Climb speed is about 6 in/s. Power is provided by a 13-year-old 9V Lego motor that is the wimpiest of the wimpiest Lego motors out there. It is being run on 12V.

The TETRIX motor we will be using in our actual minibot has 21.7 kg-cm of torque. This motor exerts no more than 200 g-cm of torque.

This is the first time in six or seven years I’ve put anything together with Legos. I think I’ve lost one of my tubs—I made this robot out of what few parts I could find. I need more gears!

Credits to my mother for taking the videos!

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Raiderbot X Meeting 4, 39 Days to Robot Ship

Meeting time: 15:00 to 21:00

We are two days behind schedule. I started a WOT (Weighted Objectives Table) discussion of the various lift concepts at 3:30. We started with seven concepts:

  • Single-jointed arm
  • Multi-jointed arm
  • Telescope (elevator)
  • Four-bar linkage
  • Eight-bar linkage
  • Scissor
  • 60/40 scissor

We narrowed it down to the four-bar linkage and the elevator and chose the four-bar linkage after a qualitative analysis using a pros/cons list for each. But I still wonder if this was necessary, because it took another 30 minutes of our time and I ran 45 minutes past my proposed deadline of 4:30. Why couldn’t we have reconsidered the two options using the three factors we had rated most highly? Will says some people just need more stake in things? Anyway, my bad for not calling them on it. Areas of improvement:

  • Do not let the loudest voices steer the discussion off-course.
  • Constantly think back to previous discussions and decisions. People were putting the WOT factors under the pros/cons lists, which is nonsense.
  • As always, be consistent, even when calling out for hands when rating the WOT factors. This is no time for jokes.

Will then separated us into four design groups for the lift, claw, base, and minibot.

Four-bar linkage: Mr. Groom found that making the shoulder pivot points’ distance shorter than that of the elbow pivot points allowed the claw to point down when the arm is down and point up when the arm is up. This should allow us to reach both the ground and the top peg as well as everything in between. This makes sense if we think about the four-bar linkage as a trapezoid and shifting the two bases—the linear displacement for the two lever arms is equal but the arm lengths are different, so angular displacements differ.

Minibot: make it as close as possible to a battery with motors glued on.

Preliminary design review planned for Saturday 17:00.

Raiderbot X Meeting 3, 41 Days to Robot Ship

Meeting time: 15:00 to 19:00.

We will have budget discussions every Tuesday after meeting.

FIRST Choice parts ordered, including the FTC Mini Kit for the minibot.

Talked more about end effectors, spent 30 minutes prototyping. Kushal and Damian made a pretty sweet prototype of a four-bar linkage arm.

I messed up here again and completely forgot that we’d planned to finish design decisions by end of the day today. Didn’t happen. Where’s my todo list? I need to make a Gantt chart soon.

Raiderbot X Meeting 2, 42 Days to Robot Ship

Meeting time: 15:00 to 19:00.

Continued talk about end effector design. We built prototypes and tested them in the shop, but just as Will was showing the old triangular scissor lift and I was wondering why there were suddenly so few people, my sister ran in and told me Mr. C (my youth symphony director) was looking for me.

Okay, major slip-up on my part.

Panicked, I promptly ran out of the shop, simultaneously realizing that I had left my violin in my locker and that that was why I felt something was awry as I walked away from my locker earlier today. In the orchestra room, I grabbed and opened a random violin case off the shelves only to discover a long-neglected violin with all four pegs loose and strings going everywhere (and collapsed bridge, needless to say). Fortunately, the next violin was in decent condition, albeit I had to play without a shoulder rest. It wasn’t my first time. It probably won’t be my last.

Halfway through rehearsal, I realized there was a (robotics) team budget meeting at 7:00 I had assured Will I would be at.

I hope never to be so stupid again.

Raiderbot X Meeting 1, 43 Days to Robot Ship

Meeting time: 15:00 to 21:00.

Printed 73-page game manual. Everyone should read the rules!

Reconsidered different drive designs (swerve, mecanum, simple, treads, omni, casters) and decided to go with swerve over mecanum in a 10-7 vote. Note the total number of votes. We have 46 people on our roster. Granted, the five PR people and some others who were working on the battery cart were not counted in that total, but I should’ve called for mandatory strongly recommended attendance for these first few days.

Also started talk about end effector design and minibot ideas. We need to nag people to come to meetings.

One thing I’ve now noticed is that if I have an idea and put off implementing it, I eventually argue myself into thinking it’s a stupid idea or other things turn up that distract me. The greater the time passed, the less likely I am to actually do it. Obviously, if I neglect to write such ideas down, I simply forget them.

I need to execute.

Raiderbot X Meeting 0, 45 Days to Robot Ship

Meeting time: 9:00 to 14:00.

Read the rules.

We hosted a team from Canby, OR per their request for a place to brainstorm after the Kickoff. Our classroom was packed.

Will wanted to set up a mock field using tape and play the game using human robots, but as LogoMotion is a very three-dimensional game, that plan was scrapped.

We identified the three parts of our robot: the drivetrain, the end effector, and the minibot. The chassis will simply be anything to hold the system together. The team was split into three groups to come up with ideas. At the end of the day, these were presented to the team.

Here are some pictures:

Design process

Design process

Minibot ideas

Minibot ideas

Drivetrain ideas

Drivetrain ideas

UPDATE 1/15: In retrospect, playing the game would have been very useful. At least, I can see now what Will was thinking by suggesting we play the game before doing anything. Before designing, we needed to identify the functions of our robot, and to do that, we needed to decide on a strategy. Strategy is a lot easier to explore when we can watch (or play) the game.