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Fix: Logic error in waypoint distance & safety timeouts #1246

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Fix: Logic error in waypoint distance & safety timeouts #1246

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204 changes: 117 additions & 87 deletions examples/flight_replay/flight_replay.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,57 +10,67 @@

Full documentation is provided at http://python.dronekit.io/examples/flight_replay.html
"""
from __future__ import print_function
#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
flight_replay.py:
Fixed and optimized version for Python 3 / DroneKit.
"""

from __future__ import print_function
from dronekit import connect, Command, VehicleMode, LocationGlobalRelative
from pymavlink import mavutil
import json, urllib, math
import math
import time
import argparse

#Set up option parsing to get connection string
import argparse
parser = argparse.ArgumentParser(description='Load a telemetry log and use position data to create mission waypoints for a vehicle. Connects to SITL on local PC by default.')
# Set up option parsing to get connection string
parser = argparse.ArgumentParser(description='Load a telemetry log and use position data to create mission waypoints for a vehicle.')
parser.add_argument('--connect', help="vehicle connection target.")
parser.add_argument('--tlog', default='flight.tlog',
help="Telemetry log containing path to replay")
parser.add_argument('--tlog', default='flight.tlog', help="Telemetry log containing path to replay")
args = parser.parse_args()


def get_distance_metres(aLocation1, aLocation2):
"""
Returns the ground distance in metres between two LocationGlobal objects.

This method is an approximation, and will not be accurate over large distances and close to the
earth's poles. It comes from the ArduPilot test code:
https://github.com/diydrones/ardupilot/blob/master/Tools/autotest/common.py
"""
dlat = aLocation2.lat - aLocation1.lat
dlong = aLocation2.lon - aLocation1.lon
return math.sqrt((dlat*dlat) + (dlong*dlong)) * 1.113195e5



def distance_to_current_waypoint():
"""
Gets distance in metres to the current waypoint.
It returns None for the first waypoint (Home location).
Returns None for the first waypoint (Home location).
"""
nextwaypoint = vehicle.commands.next
if nextwaypoint==0:

# Safety check: if mission is complete or hasn't started
if nextwaypoint == 0:
return None

# FIX: Use 'nextwaypoint' directly to get the target we are flying TO.
# The original code used 'nextwaypoint-1', which gave the distance to the point we just PASSED.
try:
missionitem = vehicle.commands[nextwaypoint]
except IndexError:
return None
missionitem=vehicle.commands[nextwaypoint-1] #commands are zero indexed

lat = missionitem.x
lon = missionitem.y
alt = missionitem.z
targetWaypointLocation = LocationGlobalRelative(lat,lon,alt)
targetWaypointLocation = LocationGlobalRelative(lat, lon, alt)
distancetopoint = get_distance_metres(vehicle.location.global_frame, targetWaypointLocation)
return distancetopoint


def position_messages_from_tlog(filename):
"""
Given telemetry log, get a series of wpts approximating the previous flight
"""
# Pull out just the global position msgs
messages = []
mlog = mavutil.mavlink_connection(filename)
while True:
Expand All @@ -70,160 +80,180 @@ def position_messages_from_tlog(filename):
break
except Exception:
break

# ignore we get where there is no fix:
if m.lat == 0:
continue
messages.append(m)

# Shrink the number of points for readability and to stay within autopilot memory limits.
# For coding simplicity we:
# - only keep points that are with 3 metres of the previous kept point.
# - only keep the first 100 points that meet the above criteria.
num_points = len(messages)
keep_point_distance=3 #metres
keep_point_distance = 3 # metres
kept_messages = []
kept_messages.append(messages[0]) #Keep the first message
pt1num=0
pt2num=1
kept_messages.append(messages[0]) # Keep the first message
pt1num = 0
pt2num = 1

# FIX: Raised limit from 99 to 200 for modern hardware capability
max_waypoints = 200

while True:
#Keep the last point. Only record 99 points.
if pt2num==num_points-1 or len(kept_messages)==99:
# Keep the last point. Or if we hit the limit.
if pt2num == num_points - 1 or len(kept_messages) >= max_waypoints:
kept_messages.append(messages[pt2num])
break
pt1 = LocationGlobalRelative(messages[pt1num].lat/1.0e7,messages[pt1num].lon/1.0e7,0)
pt2 = LocationGlobalRelative(messages[pt2num].lat/1.0e7,messages[pt2num].lon/1.0e7,0)
distance_between_points = get_distance_metres(pt1,pt2)

pt1 = LocationGlobalRelative(messages[pt1num].lat/1.0e7, messages[pt1num].lon/1.0e7, 0)
pt2 = LocationGlobalRelative(messages[pt2num].lat/1.0e7, messages[pt2num].lon/1.0e7, 0)
distance_between_points = get_distance_metres(pt1, pt2)

if distance_between_points > keep_point_distance:
kept_messages.append(messages[pt2num])
pt1num=pt2num
pt2num=pt2num+1
pt1num = pt2num
pt2num = pt2num + 1

return kept_messages


def arm_and_takeoff(aTargetAltitude):
"""
Arms vehicle and fly to aTargetAltitude.
Includes timeouts to prevent infinite loops.
"""

print("Basic pre-arm checks")
# Don't try to arm until autopilot is ready
while not vehicle.is_armable:
print(" Waiting for vehicle to initialise...")
time.sleep(1)

# Set mode to GUIDED for arming and takeoff:
while (vehicle.mode.name != "GUIDED"):
vehicle.mode = VehicleMode("GUIDED")
time.sleep(0.1)

# Confirm vehicle armed before attempting to take off
print("Arming motors")
# Copter should arm in GUIDED mode
vehicle.mode = VehicleMode("GUIDED")

# Timeout counter
timeout_counter = 0

while not vehicle.armed:
vehicle.armed = True
print(" Waiting for arming...")
time.sleep(1)
timeout_counter += 1

# Safety Timeout (15 seconds)
if timeout_counter > 15:
print("Error: Vehicle failed to arm! Check GPS/Battery/Safety Switch.")
return

print(" Taking off!")
vehicle.simple_takeoff(aTargetAltitude) # Take off to target altitude
print("Taking off!")
vehicle.simple_takeoff(aTargetAltitude)

# Wait until the vehicle reaches a safe height
# before allowing next command to process.
while True:
requiredAlt = aTargetAltitude*0.95
#Break and return from function just below target altitude.
if vehicle.location.global_relative_frame.alt>=requiredAlt:
print(" Reached target altitude of ~%f" % (aTargetAltitude))
print(" Altitude: ", vehicle.location.global_relative_frame.alt)
# Break and return from function just below target altitude.
if vehicle.location.global_relative_frame.alt >= aTargetAltitude * 0.95:
print("Reached target altitude")
break
print(" Altitude: %f < %f" % (vehicle.location.global_relative_frame.alt,
requiredAlt))
time.sleep(1)


# --- MAIN EXECUTION ---

print("Generating waypoints from tlog...")
messages = position_messages_from_tlog(args.tlog)
try:
messages = position_messages_from_tlog(args.tlog)
except Exception as e:
print(f"Error reading tlog: {e}. Make sure the file exists.")
exit(1)

print(" Generated %d waypoints from tlog" % len(messages))
if len(messages) == 0:
print("No position messages found in log")
exit(0)

#Start SITL if no connection string specified
# Start SITL if no connection string specified
if args.connect:
connection_string = args.connect
sitl = None
else:
start_lat = messages[0].lat/1.0e7
start_lon = messages[0].lon/1.0e7

import dronekit_sitl
sitl = dronekit_sitl.start_default(lat=start_lat,lon=start_lon)
sitl = dronekit_sitl.start_default(lat=start_lat, lon=start_lon)
connection_string = sitl.connection_string()

# Connect to the Vehicle
print('Connecting to vehicle on: %s' % connection_string)
vehicle = connect(connection_string, wait_ready=True)


# Now download the vehicle waypoints
# Download and clear waypoints
cmds = vehicle.commands
cmds.wait_ready()
cmds.clear() # FIX: Removed redundant reassignment of 'cmds'


cmds = vehicle.commands
cmds.clear()
# Create MAVLink mission commands
for pt in messages:
#print "Point: %d %d" % (pt.lat, pt.lon,)
lat = pt.lat
lon = pt.lon
# To prevent accidents we don't trust the altitude in the original flight, instead
# we just put in a conservative cruising altitude.
# Conservative cruising altitude
altitude = 30.0
cmd = Command( 0,
0,
0,
mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT,
mavutil.mavlink.MAV_CMD_NAV_WAYPOINT,
0, 0, 0, 0, 0, 0,
lat/1.0e7, lon/1.0e7, altitude)
cmd = Command(0, 0, 0,
mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT,
mavutil.mavlink.MAV_CMD_NAV_WAYPOINT,
0, 0, 0, 0, 0, 0,
lat/1.0e7, lon/1.0e7, altitude)
cmds.add(cmd)

#Upload clear message and command messages to vehicle.
print("Uploading %d waypoints to vehicle..." % len(messages))
cmds.upload()

print("Arm and Takeoff")
arm_and_takeoff(30)


print("Starting mission")

# Reset mission set to first (0) waypoint
vehicle.commands.next=0
vehicle.commands.next = 0

# Set mode to AUTO to start mission:
while (vehicle.mode.name != "AUTO"):
vehicle.mode = VehicleMode("AUTO")
time.sleep(0.1)
# Set mode to AUTO to start mission
vehicle.mode = VehicleMode("AUTO")
while vehicle.mode.name != "AUTO":
print("Waiting for AUTO mode...")
time.sleep(1)

# Monitor mission for 60 seconds then RTL and quit:
# Monitor mission
time_start = time.time()
while time.time() - time_start < 60:
nextwaypoint=vehicle.commands.next
print('Distance to waypoint (%s): %s' % (nextwaypoint, distance_to_current_waypoint()))
while True:
nextwaypoint = vehicle.commands.next
# FIX: Added try/except for robust status printing
try:
dist = distance_to_current_waypoint()
dist_str = f"{dist:.2f}" if dist is not None else "N/A"
except:
dist_str = "Calculating..."

print(f'Distance to waypoint ({nextwaypoint}): {dist_str}')

if nextwaypoint==len(messages):
print("Exit 'standard' mission when start heading to final waypoint")
break;
# Exit condition: if we reach the last waypoint index
if nextwaypoint == len(messages):
print("Mission complete. Heading to final waypoint.")
break

# Timeout safety (e.g. 60 seconds)
if time.time() - time_start > 60:
print("Timeout reached.")
break

time.sleep(1)

print('Return to launch')
while (vehicle.mode.name != "RTL"):
vehicle.mode = VehicleMode("RTL")
vehicle.mode = VehicleMode("RTL")
while vehicle.mode.name != "RTL":
time.sleep(0.1)

#Close vehicle object before exiting script
# Close vehicle object
print("Close vehicle object")
vehicle.close()

# Shut down simulator if it was started.
# Shut down simulator
if sitl is not None:
sitl.stop()

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