Counting and Turning by Feel

Try It — The Counter Was Always There

Back in Project 3 you turned a wheel with your hand and watched a number change in Port View. You were told to remember it. Here it is.

Open Port View on a wheel motor’s port. Do not run anything — just roll that wheel with your hand and watch its number.

Find your degrees per inch

Degrees are the motor’s own unit. To connect them to the real world you need to know how many make an inch on your robot.

1. Put the robot on the floor and mark where the front edge sits.
2. Note the wheel’s number in Port View (or roll it to a nice round number).
3. Push the robot straight forward exactly 24 inches. Slowly, and in a straight line.
4. Read the number again. The difference is your degrees for 24 inches.

Your three numbers are not identical. Why not — and which one should you use?

Check the curtain: multiply your degrees-per-inch by 24. Is that close to what a move for 24 in. block must be counting to? What does that tell you about how the move block works?

Learn It — A Number Instead of a Switch

Project 10’s checking watched a switch. The exact same checking can watch a number — and the brick hands you two of them as round reporter ovals that fit into any hexagon.

Both reporters are on the regular shelf: degrees counted in the Motors category, angle in the light-blue Sensors category.

The same checking you already know

Look at these two side by side. Only the question changed.

Read the new one out loud: “keep checking the robot’s heading — the moment it has turned past 89 degrees, move on.” The green > hexagon from Project 10 finally gets its job.

Turning by feel

In Project 5 you tuned a 90° turn by trial and error, because wheel degrees are not robot degrees. The angle is robot degrees. Here is the turn, rebuilt:

It will go too far. Every time.

Run that turn and then read the angle in Port View on port 2. You asked to stop past 89. You will see something like 96.

Nothing is broken. Your robot has inertia — it is spinning, and when the checking succeeds and the motors stop, it keeps swinging a little further.

Left turns count down

Turning right, the angle climbs. Turning left, it falls — through zero and into negative numbers. That flips your hexagon:

Do It — Turn by the Numbers

Step 1 — Measure your overshoot

New project called Gyro Turn. Build the Learn It turn — reset angle, spin at steering 100, wait until past 89, stop. Run it, then read the final angle in Port View on port 2.

What is the relationship between speed and overshoot? Which speed will you use for turns, and why?

Step 2 — Correct for it

Subtract your overshoot from the target and run again. Keep adjusting until the robot lands on 90.

• My robot lands within a couple of degrees of 90

Step 3 — A left turn too

Copy the turn, flip the steering to −100, flip the hexagon to < −83 (your corrected number, negative). Run it.

• My robot turns 90° to the left as reliably as to the right

Step 4 — The square, again — and this time it closes

In Project 5 you drove a square with four wheel-counted turns and it did not close. Do it again — same square, distances with move for rotations, but every corner turned by the gyro.

Your wheel-counted square drifted a little more with every corner. Why does a gyro-turned square not do that?

• My square closes

Step 5 — Drive a checked distance

One more trick with the wheel counter, so you have it when you need it. Reset the count, start moving, wait until A degrees counted passes your degrees-per-inch times 12, stop. That is a 12-inch drive built out of raw checking — the thing move for inches does for you.

When would you build a drive this way instead of using a plain move for inches block? (Hint: what if you wanted to check two things at once while driving?)

Step 6 — Mission 9 Bonus — get Botguy out9 pts

Your claw can still be holding him. He just has to be clear of the enclosure and down on the floor at the same instant.

• Botguy is out of the enclosure and touching the floor

Step 7 — Mission 18 Base — take him to the loading zone11 pts

Mission 18 is final position, so Botguy has to still be IN THE ZONE when the match ends. Set him down properly and back straight away.

• Botguy is IN the Loading Zone and stays there

Step 8 — Mission 8 — deliver the red cube20 pts

• Pallet and Large Red Cube are both on the Loading Dock
• A Small Red Cube is on top of the Large Red Cube up there

Step 9 — Run it five times

Score It — Checkpoint

My score

My measuring card

These join your motor card. Every precise move from here on uses them.

Write the check

Can you do it again?

• I can read a wheel’s degree count and the angle live in the app
• I can work out my robot’s degrees per inch and convert a distance
• I always reset the angle before I start counting a turn
• I measure my overshoot and subtract it from my target
• I use > turning right and < turning left, and I check it before running
• I can make a repeatable 90° turn by feel instead of by wheel count
• My square closes

Think about it

Your battery is half flat, so the robot turns slower. What happens to a turn tuned by wheel degrees in Project 5? What happens to a turn that waits for the angle?

Wheel degrees tell you how far the wheels turned — not how far the robot moved. Name a situation where those two are different.

You have now built the reset-spin-wait-stop turn several times, in several projects. What would you rather do than keep rebuilding it?

Next

You have a robot that can measure. You also have a program that says the same twenty lines over and over.

In Project 12 — Teaching Your Robot New Moves, you give that whole stack a name — and then you just say the name.