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Robot build

We started the season as a rookie team. Both coaches and all 5 students (eventually 7) had never competed in FLL. Most of us had never actually built a LEGO® MINDSTORMS® robot. As with any rookie team, we sought out a viable base robot design on the internet, and used this as our base robot. One team mentor worked with 2 to 3 students to build a copy of that base robot. The mentor interpreted the pictures of the design, and conveyed it to the students who actually built the robot.

Building this way was a slow process and at times very frustrating. An alternate strategy we should have used is "dual build." You need twice as many pieces, but it works well. The mentor builds a robot in parallel with the student. The mentor puts several pieces on the robot, tell the student what was done and allows the student to hold and interpret what was done via touch. Then the student mimics the changes on his or her robot.

So I would summarize the process as follows:

  1. team builds robot with mentor
  2. team designs, builds and tests attachments
  3. team develops strategy and designs/tests programs

Below are pictures of the robots we used for our first and second competition:

Our first robot "Phighter".

A driving design element for our first robot was the desire (on the part of the students) for it to climb the "stairs" in the Senior Solutions Challenge. We were able to do that, but only about 10-20 percent of the time. In our very first match as a team, we were able to successfully balance after the stair climb. It was a thrilling moment.

phighter too
Our second robot "Phighter Too".

After our first competition, we decided to redesign our robot to take on tasks more reliably. We did succeed in building a more capable robot, but it was a great stress level on the team. In the future, I would not recommend such a major undertaking again. I would advise practice, "tweaks" and more practice, but no rebuild.

A critical success factor for all FLL teams is precision in starting the robot on its "missions." This can be done by sight or with the use of a "jig." Most teams use sighted alignment techniques, but we obviously could not. Every team member started at least one mission per match, so we developed and used a standard starting position for our first robot.

We spent many hours on different types of alignment. Here is a picture of one of our better (early design) alignment jigs, was a bit fragile but pretty accurate. It was not very good if it dropped! It did lead us down the road to better designs and strategies.

early jig
Early alignment jig.

For "Phighter," we incorporated into the design a tailpiece and some pegs off to the right side for alignment. If you back the robot into the corner, you can feel when the robot is at the precise angle we used to start. For our missions, we aligned into the back corner and touching the black standoff on the right side of the robot. (see top view photo below) It looked like this:

phighter tailpiece
Phighter's alignment jig.

phighter tailpiece
Phighter's alignment jig (top view). 

Obviously, since we won (as co-champions) our qualifier, this jig performed quite well. It did however force us to stay within a few turns of the home base. To move farther from home base, you would need sensors to help realign your robot or use another technique like "bump turn alignment." We chose "bump turns."

A "bump turn" is simple driving maneuver that allows the robot to re-establish that it is "square" to the direction it intends to go. You drive out to a point. Back into a wall and push just a bit (timed not by degrees). The robot realigns. Then you proceed, usually across the field on a true heading. This opened up several missions to us that we could do much more reliably than the "stairs." It is definitely a good technique to incorporate into your design.

Phighter Too's bumper.

The next two photos show a bump turn in action:
Back into Wall Drive off straight

The left (or top) photo shows the robot backing into the wall and lining up. The right (or bottom) photo shows the robot driving straight across the field ready to take on another mission farther from the home base than possible without the bump turn.

This new "bumper" design had us back to basics on a starting jig. We went very simple and chose to implement a spacer. It could be used for going "north" or "east." This gave us two starting positions versus one for our previous techniques. It was simple and reliable. Align the robot right (or left) against the jig and back tight against the wall. It could also be rebuilt easily if dropped! The new jig looked like this:

Bumper jig Bumper jig
Bumper jig Bumper jig

We (the coaches) had hoped to get into sensors from a robot design and a programming perspective, but simply didn't have the time. This was our first year as coaches and we had a lot to do to form the team from scratch. The next season we compete, I hope to have a least one or two sensors in use!