ITPEC FE Subject A April 2025 Question 4
ITPEC FE Subject A April 2025 — Question 4 of 60
Line-following vehicle control — determine motor speed adjustments based on sensor feedback.
The vehicle follows a black circular outline using two photo-reflective sensors (L, R):
- •More black under sensor → sensor value decreases
- •More white under sensor → sensor value increases
When Sensor L > Sensor R:
- Left sensor sees more white → vehicle drifted outward (away from circle)
- Correction: turn inward (right) → Motor L increase, Motor R decrease
When Sensor L < Sensor R:
- Right sensor sees more white → vehicle drifted inward (into the circle)
- Correction: turn outward (left) → Motor L decrease, Motor R increase
Why not others:
- (a) — same correction direction for both cases, cannot handle both drifts
- (b) — reverses the correction logic (turns away from the circle when it should turn toward it)
- (d) — same as (c) but swapped, produces opposite corrections
Key rule: To turn right, speed up the left motor and slow the right. To turn left, do the opposite. Match correction to drift direction relative to the circular path.
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