Lesson 5 · Proportional Control — Knowledge ChecksAnswer key

With base speed 0.3, what does `arcade(0.3, 0.15)` set the two motors to?

1. A.Left 0.15, right 0.45
2. B.Left 0.45, right 0.15✓
3. C.Both 0.3
4. D.Left 0.3, right 0.15

arcade adds turn to the left motor and subtracts it from the right: 0.3 + 0.15 = 0.45 left, 0.3 − 0.15 = 0.15 right.

Setpoint is 0.5 and the sensor reads 0.2. What is the error?

1. A.−0.3
2. B.+0.3✓
3. C.0.7
4. D.0.2

error = 0.5 − 0.2 = +0.3. The positive sign says the robot drifted onto white and should steer toward the line.

If Kp = 0.6 and error = 0.3, what is the correction?

1. A.0.9
2. B.0.18✓
3. C.0.3
4. D.0.5

correction = error × Kp = 0.3 × 0.6 = 0.18.

Your robot follows the line but weaves back and forth rapidly, never settling. What should you do to Kp?

1. A.Increase it — it needs to react harder
2. B.Decrease it — it is over-correcting✓
3. C.Set it to 0
4. D.Leave Kp; increase base_effort instead

Rapid weaving is over-correction — Kp is too high. Lower it for gentler, smoother steering.