Analyze flight logs

What you will do

You will analyse a log from your SITL flight with pyulog and a plotting library, and optionally with Flight Review. Privacy note: logs uploaded to the public Flight Review service can be public; do not upload logs of real flights you consider sensitive.

Before you start

• A ULog file from an earlier lab.
• Python with pyulog, numpy and matplotlib installed (pip install pyulog).
• Lesson M6-T13 (flight logs and debugging).

Steps

1. List the file contents: ulog_info flight.ulg. Note the duration, parameters and the list of topics with their message counts.
2. Export topics to CSV: ulog2csv flight.ulg -m vehicle_local_position,vehicle_status, or read them in Python.
3. Plot measured local position against the setpoint (from trajectory_setpoint) and compute RMS and maximum tracking error.
4. Plot the arming state and navigation state over time to mark mode changes.
5. Inspect the estimator status/innovation topics for your version (list the topics first) and find the maximum innovation test ratios.

from pyulog import ULog
import numpy as np

log = ULog("flight.ulg")
pos = log.get_dataset("vehicle_local_position").data
sp  = log.get_dataset("trajectory_setpoint").data
t_pos = pos["timestamp"] * 1e-6
t_sp  = sp["timestamp"] * 1e-6
x_sp = np.interp(t_pos, t_sp, sp["position[0]"])
err = np.hypot(pos["x"] - x_sp, 0)     # extend to y and z, ignoring NaN setpoints
print("rows:", len(t_pos), "RMS x error:", np.sqrt(np.nanmean(err**2)))

Report

• A timeline with arming, mode changes and any failsafe events.
• Tracking error statistics per leg of the mission.
• The estimator’s innovation statistics and an assessment of whether the filter looked consistent.
• Three questions the log cannot answer and what extra logging would answer them.

How to know it worked

• Plots of setpoint against measurement with error statistics.
• A timeline of modes and events.
• A written assessment of estimator health from innovation data.

If it does not work

References

• PX4: flight log analysis
• pyulog repository
• PX4 Flight Review (note: uploads may be public)

Record your progress