• 使用DroneKit与PX4通讯
    • 配置DroneKit
    • 完整的任务示例

    使用DroneKit与PX4通讯

    官网英文原文地址：http://dev.px4.io/dronekit-example.html

    DroneKit可以帮助创建强大的无人机应用。这些应用运行在无人机的协同计算机上，通过执行计算密集但又需要低延迟的任务（计算机视觉）来增强飞控计算机。

    DroneKit和PX4目前致力于获得完全兼容。截止DroneKit-python 2.2.0，仅提供任务处理和状态监控这样的基本支持。

    配置DroneKit

    首先，从当前主分支安装DroneKit-python

    1. git clone https://github.com/dronekit/dronekit-python.git
    2. cd ./dronekit-python
    3. sudo python setup.py build
    4. sudo python setup.py install

    创建一个新的python文件并导入DroneKit, pymavlink和基本模块

    1. # Import DroneKit-Python
    2. from dronekit import connect, Command, LocationGlobal
    3. from pymavlink import mavutil
    4. import time, sys, argparse, math

    连接到无人机或模拟器的MAVLink端口

    1. # Connect to the Vehicle
    2. print "Connecting"
    3. connection_string = '127.0.0.1:14540'
    4. vehicle = connect(connection_string, wait_ready=True)

    显示一些基本的状态信息

    1. # Display basic vehicle state
    2. print " Type: %s" % vehicle._vehicle_type
    3. print " Armed: %s" % vehicle.armed
    4. print " System status: %s" % vehicle.system_status.state
    5. print " GPS: %s" % vehicle.gps_0
    6. print " Alt: %s" % vehicle.location.global_relative_frame.alt

    完整的任务示例

    下面的python脚本文件给出了使用DroneKit和PX4的完整任务范例。目前还不完全支持模式切换，因此我们发送自定义的模式切换指令。

    1. ################################################################################################
    2. # @File DroneKitPX4.py
    3. # Example usage of DroneKit with PX4
    4. #
    5. # @author Sander Smeets <sander@droneslab.com>
    6. #
    7. # Code partly based on DroneKit (c) Copyright 2015-2016, 3D Robotics.
    8. ################################################################################################
    10. # Import DroneKit-Python
    11. from dronekit import connect, Command, LocationGlobal
    12. from pymavlink import mavutil
    13. import time, sys, argparse, math
    16. ################################################################################################
    17. # Settings
    18. ################################################################################################
    20. connection_string       = '127.0.0.1:14540'
    21. MAV_MODE_AUTO   = 4
    22. # https://github.com/PX4/Firmware/blob/master/Tools/mavlink_px4.py
    25. # Parse connection argument
    26. parser = argparse.ArgumentParser()
    27. parser.add_argument("-c", "--connect", help="connection string")
    28. args = parser.parse_args()
    30. if args.connect:
    31.     connection_string = args.connect
    34. ################################################################################################
    35. # Init
    36. ################################################################################################
    38. # Connect to the Vehicle
    39. print "Connecting"
    40. vehicle = connect(connection_string, wait_ready=True)
    42. def PX4setMode(mavMode):
    43.     vehicle._master.mav.command_long_send(vehicle._master.target_system, vehicle._master.target_component,
    44.                                                mavutil.mavlink.MAV_CMD_DO_SET_MODE, 0,
    45.                                                mavMode,
    46.                                                0, 0, 0, 0, 0, 0)
    50. def get_location_offset_meters(original_location, dNorth, dEast, alt):
    51.     """
    52.     Returns a LocationGlobal object containing the latitude/longitude `dNorth` and `dEast` metres from the
    53.     specified `original_location`. The returned Location has the same `alt` value
    54.     as `original_location`.
    55.     The function is useful when you want to move the vehicle around specifying locations relative to
    56.     the current vehicle position.
    57.     The algorithm is relatively accurate over small distances (10m within 1km) except close to the poles.
    58.     For more information see:
    59.     http://gis.stackexchange.com/questions/2951/algorithm-for-offsetting-a-latitude-longitude-by-some-amount-of-meters
    60.     """
    61.     earth_radius=6378137.0 #Radius of "spherical" earth
    62.     #Coordinate offsets in radians
    63.     dLat = dNorth/earth_radius
    64.     dLon = dEast/(earth_radius*math.cos(math.pi*original_location.lat/180))
    66.     #New position in decimal degrees
    67.     newlat = original_location.lat + (dLat * 180/math.pi)
    68.     newlon = original_location.lon + (dLon * 180/math.pi)
    69.     return LocationGlobal(newlat, newlon,original_location.alt+alt)
    75. ################################################################################################
    76. # Listeners
    77. ################################################################################################
    79. home_position_set = False
    81. #Create a message listener for home position fix
    82. @vehicle.on_message('HOME_POSITION')
    83. def listener(self, name, home_position):
    84.     global home_position_set
    85.     home_position_set = True
    89. ################################################################################################
    90. # Start mission example
    91. ################################################################################################
    93. # wait for a home position lock
    94. while not home_position_set:
    95.     print "Waiting for home position..."
    96.     time.sleep(1)
    98. # Display basic vehicle state
    99. print " Type: %s" % vehicle._vehicle_type
    100. print " Armed: %s" % vehicle.armed
    101. print " System status: %s" % vehicle.system_status.state
    102. print " GPS: %s" % vehicle.gps_0
    103. print " Alt: %s" % vehicle.location.global_relative_frame.alt
    105. # Change to AUTO mode
    106. PX4setMode(MAV_MODE_AUTO)
    107. time.sleep(1)
    109. # Load commands
    110. cmds = vehicle.commands
    111. cmds.clear()
    113. home = vehicle.location.global_frame
    115. # takeoff to 10 meters
    116. wp = get_location_offset_meters(home, 0, 0, 10);
    117. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_TAKEOFF, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    118. cmds.add(cmd)
    120. # move 10 meters north
    121. wp = get_location_offset_meters(wp, 10, 0, 0);
    122. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_WAYPOINT, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    123. cmds.add(cmd)
    125. # move 10 meters east
    126. wp = get_location_offset_meters(wp, 0, 10, 0);
    127. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_WAYPOINT, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    128. cmds.add(cmd)
    130. # move 10 meters south
    131. wp = get_location_offset_meters(wp, -10, 0, 0);
    132. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_WAYPOINT, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    133. cmds.add(cmd)
    135. # move 10 meters west
    136. wp = get_location_offset_meters(wp, 0, -10, 0);
    137. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_WAYPOINT, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    138. cmds.add(cmd)
    140. # land
    141. wp = get_location_offset_meters(home, 0, 0, 10);
    142. cmd = Command(0,0,0, mavutil.mavlink.MAV_FRAME_GLOBAL_RELATIVE_ALT, mavutil.mavlink.MAV_CMD_NAV_LAND, 0, 1, 0, 0, 0, 0, wp.lat, wp.lon, wp.alt)
    143. cmds.add(cmd)
    145. # Upload mission
    146. cmds.upload()
    147. time.sleep(2)
    149. # Arm vehicle
    150. vehicle.armed = True
    152. # monitor mission execution
    153. nextwaypoint = vehicle.commands.next
    154. while nextwaypoint < len(vehicle.commands):
    155.     if vehicle.commands.next > nextwaypoint:
    156.         display_seq = vehicle.commands.next+1
    157.         print "Moving to waypoint %s" % display_seq
    158.         nextwaypoint = vehicle.commands.next
    159.     time.sleep(1)
    161. # wait for the vehicle to land
    162. while vehicle.commands.next > 0:
    163.     time.sleep(1)
    166. # Disarm vehicle
    167. vehicle.armed = False
    168. time.sleep(1)
    170. # Close vehicle object before exiting script
    171. vehicle.close()
    172. time.sleep(1)