Range finder for terrain following in Drone Programming - Step-by-Step Execution

Concept Flow - Range finder for terrain following

Start

↓

Read range finder sensor

↓

Calculate altitude error

↓

Adjust drone altitude

↓

Check if mission complete

No Yes↓

Repeat

The drone reads the range finder sensor, calculates altitude error, adjusts altitude, and repeats until the mission is complete.

Execution Sample

Drone Programming

altitude_setpoint = 10
while mission_active:
    current_altitude = read_range_finder()
    error = altitude_setpoint - current_altitude
    adjust_altitude(error)
    if mission_complete():
        break

This code keeps the drone at a set altitude by reading the range finder and adjusting altitude until the mission ends.

Execution Table

Step	Action	current_altitude (m)	error (m)	Altitude Adjustment	Mission Complete?
1	Read sensor	8.5	10 - 8.5 = 1.5	Increase altitude by 1.5	No
2	Read sensor	9.2	10 - 9.2 = 0.8	Increase altitude by 0.8	No
3	Read sensor	9.9	10 - 9.9 = 0.1	Increase altitude by 0.1	No
4	Read sensor	10.0	10 - 10.0 = 0.0	No adjustment	No
5	Read sensor	10.1	10 - 10.1 = -0.1	Decrease altitude by 0.1	No
6	Read sensor	10.0	10 - 10.0 = 0.0	No adjustment	Yes

💡 Mission complete detected at step 6, loop exits.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	After 6
current_altitude	N/A	8.5	9.2	9.9	10.0	10.1	10.0
error	N/A	1.5	0.8	0.1	0.0	-0.1	0.0
mission_active	True	True	True	True	True	True	False

Key Moments - 3 Insights

Why does the error become negative at step 5?

At step 5, current_altitude is 10.1 which is above the setpoint 10, so error = 10 - 10.1 = -0.1, indicating the drone is too high and needs to decrease altitude.

Why is there no altitude adjustment at step 4?

At step 4, error is zero (10 - 10.0 = 0), so the drone is at the desired altitude and no adjustment is needed, as shown in the execution_table row 4.

When does the loop stop running?

The loop stops when mission_complete() returns True, which happens at step 6, causing mission_active to become False and exiting the loop.

Visual Quiz - 3 Questions

Look at the execution table, what is the error value at step 3?

A 1.5

B 0.8

C 0.1

D -0.1

💡 Hint

Check the 'error (m)' column in row 3 of the execution_table.

At which step does the drone first stop increasing altitude?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look at the 'Altitude Adjustment' column to find when it says 'No adjustment' for the first time.

If the altitude_setpoint was changed to 12, how would the error at step 1 change?

A It would be 3.5

B It would be -1.5

C It would stay 1.5

D It would be 10

💡 Hint

Calculate error as altitude_setpoint - current_altitude using the new setpoint and step 1 altitude.

Concept Snapshot

Range finder terrain following:
- Read sensor for current altitude
- Calculate error = setpoint - current altitude
- Adjust altitude based on error
- Repeat until mission complete
- Keeps drone flying at desired height over terrain

Full Transcript

This visual execution shows how a drone uses a range finder sensor to maintain a set altitude for terrain following. The drone reads the current altitude, calculates the difference from the desired altitude (error), and adjusts its altitude accordingly. The process repeats until the mission is complete. The execution table traces each step's sensor reading, error calculation, altitude adjustment, and mission status. Key moments clarify why error can be negative, when no adjustment is needed, and when the loop stops. The quiz tests understanding of error values, adjustment timing, and effects of changing the setpoint.