VISUAL · BLOCKS → PYTHON

The Embodied Loop

Wire a sense->decide->act loop that drives the rover forward and halts it within 0.25 m of the goal with no overshoot.

01Challenge

Bench opens in the Blockly editor. The rover sits at the origin facing an amber goal 3.0 m dead ahead. Make the rover drive forward and stop when it gets close to the goal, not crash through it, not stop early. Drag blocks, press Run. You have not been taught the right answer yet, so try it.

02Model

A robot is not a program that runs once. Picture driving to a goal: point it, push go, and it overshoots, because a single command can't know when to stop. So it does something else: it SENSES (how far to the goal?), DECIDES (close enough yet?), and ACTS (drive, or stop), then does the whole thing again, many times a second. That loop is the robot.

The one thing that trips everyone up: if you check 'am I there yet?' only once, the rover never re-asks and overshoots forever. The deciding has to live inside the loop, asked every single tick.

Sense → think → act, closed around the world.

03Guided practice

Step 1 (worked): the loop and forward-drive block are placed; you drop in if goal distance < ??? with a number near 0.25. Step 2 (faded): rebuild the loop and choose the threshold yourself. Step 3 (independent): tune the threshold so the rover halts within tolerance. Too small overshoots, too large stops early.

04Feedback

PASS WHEN Stopped with final goal-distance <= 0.25 m, never exceeding goal x by more than 0.30 m, with the stop-decision evaluated every loop iteration.

If your run fails, check:

FAIL: ran the full 15 s without stopping. No stop condition reached; place a goal-distance read in the comparison.
FAIL: overshot the goal by 0.62 m. The rover never re-checks distance while driving; move the if inside the repeat-forever loop.
FAIL: halted 0.71 m short. Stop threshold fires while still far away; lower it toward 0.25 m.

05Retrieve & space

Tag fragments as SENSE / DECIDE / ACT (read_range -> SENSE, set_motor -> ACT, if < 0.25 -> DECIDE).
Predict: change threshold 0.25 -> 0.6, does the rover stop closer or farther from the goal? (Farther: triggers sooner.)
Spot-the-bug: a block stack has the stop-check outside the loop; drag it back inside.

06Mastery & project

From the fixed seed, the rover drives forward and halts within 0.25 m of the goal with no overshoot beyond 0.30 m, stop-decision provably inside the loop (L0: runs a given loop).

Contributes the stop-on-condition STOP primitive to the capstone; the 'test the sensor every tick, inside the loop' habit is the skeleton of every later controller (PID loop, timer-ISR tick).

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VISUAL · BLOCKS → PYTHON

The Embodied Loop

Drag blocks (shown here as the Python they generate) so the rover senses, decides, and acts every tick.

You read

the same obs values, read as blocks

You change

the blocks you snap together inside control

Fixed

the loop, the rover, and the physics