A Modular, Mission-Selectable Build

The mission 4 min

One robot that can be reconfigured between runs — not rebuilt.

Yesterday you established that the mission set varies per round. A robot that needs rebuilding to suit the round cannot suit the round, because there is no time to rebuild.

What the modules have to reach 5 min

The three launch pads at A, B and C sit in a row along the bottom and want the same thing done to them, so one module serves all three. That is the easy half.

The other jobs are different in kind. The launch gantry at D is a delivery, and the satellite row at E is at the top of the mat and almost certainly wants something else again.

So the natural split is: a pad module used in every round, and a satellite module used only when the crossing to E is worth it. Two modules, one mounting point, chosen before the round starts.

Check the clearance along the bottom row while you are looking. The pads at A, B and C are only about fourteen units apart, so a module that overhangs sideways can be interfering with the next pad while it is working on this one.

The technique — one mount, many modules 12 min

Modularity is not "some parts come off". It is a mounting point with rules, and everything that attaches obeys them.

• One position, keyed. A module fits one way round and one place. If it can go on rotated or offset, it will, on the day, and the whole run will be out by that offset.
• Locates before it fastens. Push it home against a stop first, then pin it. That is lesson 10’s rule and it matters more with several modules than it did with one.
• Same motor, same port. Every module drives from port A. A module needing a different port is a different robot.
• Same weight, roughly. A much heavier module shifts the balance and changes the tuning you certified in Block 4. If one module is far heavier, expect to re-check the follower with it fitted.
• Fits in ten seconds, with one hand, without tools. Time it. If it takes a minute and two people, it is not modular.

Build it 10 min

Build the mount first and the modules second. Teams do it the other way round and end up with two good modules that attach differently.

The mount is whatever gives you a repeatable position: a pair of pin holes and a hard stop is enough. Test it by fitting the same module five times and checking it sits identically each time.

Then build the pad module, since every round needs it. Build the satellite module only if your costing in lesson 33 said the crossing to E is worth doing at all — if it is not, one module is a complete and honest answer, and you should say so rather than building something you will never fit.

Sketch both from the side and above, marking the widest point, and keep the ports as they have been all course: drive on B and C, gyro on 2, colour on 3, ultrasonic on 4, module on A.

Program it — the configuration card 12 min

For each module, write a card. This is the document the person setting the robot up reads, out loud, before every round.

• The module name — short, and the same name the menu will use tomorrow.
• Which missions it serves, and which it cannot.
• The motor positions, found by hand and read off the port view, exactly as in lesson 26.
• Anything the program must be told differently when it is fitted — a slower approach, a different arm travel.

Then check your My Blocks still work with each module fitted. Collect may need a different position per module, which by lesson 14’s rule is an input, not a second block.

Tune it — the swap drill 9 min

Time a full module change: robot on the table, module off, other module on, seated and pinned, robot back at HOME ready to start.

Under thirty seconds is a modular robot. Over two minutes is a rebuild wearing a disguise, and the honest response is to simplify the mount rather than practise harder.

Then do the drill three times and check the module ends up in the same place each time. Fit a module, drive one pad approach, mark where the robot stops. Repeat. If the marks scatter, the mount is not locating properly and every route you tuned will inherit that scatter.

Run it — both configurations 6 min

With the pad module fitted, run HOME to a launch pad, do the job, deliver to the gantry at D, return to HOME.

Then swap to the satellite module, on the clock, and run HOME up to the satellite row at E and back.

Two runs, one robot, one mounting point, nothing rebuilt. If either run needed a spanner, a second pair of hands or a rethink, that is today’s remaining work — and it is the last build time this course gives you.

The journal 4 min

Today’s entry:

• the mount, sketched, with what keys it into one position
• a configuration card per module — name, missions served, motor positions, anything the program must be told
• the swap drill time, and the three repeat marks
• whether the follower needed re-checking with the heavier module
• one sentence on the difference between swapping during a run and swapping between runs, and why one is expensive and the other is not