The initial idea of the flight task architecture was that
a task can freely set it's setpoints and doesn't have to
worry about takeoff and landing. It would just takeoff
when it's landed and there's a setpoint to go up and
land when it puts a setpoint that pushes into the ground.
With the takeoff logic there are some significant interface
problems depending on the way a task is implemented:
From the setpoint is not high enough to trigger to
an unexpected takeoff because of some estimator
fluctuation affecting the setpoint. It's easiest to solve this
by allowing the task to determine when a takeoff is triggered.
If no condition is implemented by default a task is not
allowing a takeoff and cannot be used to get the vehicle
off the ground.
Also update some comments.
In case we activate the task and don't have a locked yaw, we should
initialize the yaw setpoint with NAN to avoid any abrupt changes.
- better in terms of dependencies:
- the position controller code depended on position topics for yaw
- mc_pos_control does not have to be run for Stabilized mode
- the code path is much simpler, and thus less error prone. This is
especially important since Stabilized is often used as a fail-safe flight
mode.