BlueROV-10: Mission Command

1. Mission Command Overview:

There are three types of commands:

•  NAVigation commands (MAV_CMD_NAV_*) are used to control vehicle movement, including takeoff, moving to and around waypoints, changing altitude, and landing.
•  DO commands (MAV_CMD_DO_*) are for auxiliary functions that do not affect the vehicle’s position (for example, setting the camera trigger distance, or setting a servo value).
•  CONDITION commands (MAV_CMD_CONDITION_*) are used to delay DO commands until some condition is met. For example MAV_CMD_CONDITION_DISTANCE will prevent DO commands executing until the vehicle reaches the specified distance from the waypoint.

2. Download current mission:

The mission commands for a vehicle are accessed using the Vehicle.commands attribute. The attribute is of type CommandSequence, a class that provides ‘array style’ indexed access to the waypoints which make up the mission.

Waypoints are not downloaded from vehicle until download() is called. The download is asynchronous; use wait_ready() to block your thread until the download is complete:

# Connect to the Vehicle (in this case a simulated vehicle at 127.0.0.1:14550)vehicle = connect('127.0.0.1:14550', wait_ready=True)# Download the vehicle waypoints (commands). Wait until download is complete.cmds = vehicle.commandscmds.download()cmds.wait_ready()

3. Clearing current mission:

To clear a mission you call clear() and then Vehicle.commands.upload() (to upload the changes to the vehicle):

# Connect to the Vehicle (in this case a simulated vehicle at 127.0.0.1:14550)vehicle = connect('127.0.0.1:14550', wait_ready=True)# Get commands object from Vehicle.cmds = vehicle.commands# Call clear() on Vehicle.commands and upload the command to the vehicle.cmds.clear()cmds.upload()

Note: If a mission that is underway is cleared, the mission will continue to the next waypoint. If you don’t add a new command before the waypoint is reached then the vehicle mode will change to RTL (return to launch) mode.