Sunday, February 23, 2014

First Build Season

Now that the "Build Season" is over I can reflect on the last 7 weeks with a view to being better prepared for next year. In the First Robotics Challenge or FRC the scope of the challenge is released to the public at the start of January and the teams have just 7 weeks to build a robot that can meet the challenge. Thus the "build season". Now we have a couple of weeks to breathe and prepare for the actual competitions after the March break.
The finished robot meets all of the primary goals we set out:

  • pick up the ball
  • score a low goal
  • score a low goal in autonomous mode
  • catch the ball
  • use flip-up velcro bumpers to change from red to blue easily
The last few days of building consisted of figuring out how to make things work and stay within the competition constraints. One engineer that helped us out stated that an engineer's job is to understand "function" and "constraints" - what it does and what rules and materials you must work with. This helped me to better understand the preparation necessary going into a challenge like this. As the robot came together I had to ask "What could I have taught them to better prepare the students to face up to a challenge like this. Here is a list of some of the lessons that came to mind.

  1. At least some of the students have to be good at 3D modelling on a computer. We wrestled every day with vague ideas and pencil or whiteboard drawings that lacked any sort of precision, testing or detail. The 2 or 3 models we did end up with proved immeasurably important in the final design.
  2. The devil is in the details. The students required a better knowledge of the materials and mechanisms available to make the design work. Early designs for the pickup arm featured the wheels at the top rotating in blank holes with no source of power. Shaft and bearing sizes needed to be interpreted and sometimes guessed at. There are just a handful of companies that supply parts for First robots and many of these parts have associated step files online so integrating these parts into a 3D model is very easy to do.
  3. Once the ideas start to come together on the drawing table the students must be able to model their ideas both on screen and with mock-up models to insure that all of the robot parts interact and act in the way expected.
  4. Get the bumpers on early. The bumpers on the robot interact with the ball as it is picked up and so the bumpers, or a reasonable facsimile, need to be in place. You don't want to be waiting on finished bumpers when it is time to try out some aspects of the robot function.
  5. The students all need practice using hand tools to layout, cut and drill. For many this was their first or second experience with a hacksaw or electric hand drill. Precise measurement, accurate layout and skill with a hacksaw, drill press or portable drill were practiced for just a second or third time on the build.
  6. Knowledge of fasteners and threads:
    - nut and bolt sizes and types
    - tap and die use
    - use of wrenches, nut drivers and torque
  7. Knowledge and experience with pneumatic systems. We had no pneumatic systems experience or materials when we decided to use pneumatics to operate the arm. Students require a better understanding of the constraints and an ability to calculate required and applied forces.
  8. Knowledge of programming. We have some excellent programmers on our team and they handled the challenge of robot control with considerable skill. They were, however, hampered by not having a robot controller/computer to learn with until January 4. Advanced functions such as automatic targeting could not be attempted due to lack of time and experience.
  9. The electrical wiring went pretty well. Most of my students have some classroom experience at this. Review wire and fuse sizes and have some wire labels ready. The robot became a bowl of spaghetti at the last minute when 3 pneumatic solenoids (4 wires each) were added. A last minute glitch was caused when the arm pulled on a wire ever so slightly causing the robot to stall. Wiring needs to be neat and bundled and should not move when other moving parts operate.
I'm sure there are more but I think this is a list of the major lessons and learning that can happen next fall as the students head into their second year at this.

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