- vehicle will fly less aggressive
- it does not make sense to set the lower acceleration limit to something
that exceeds gravity if most of the vehicles do not support reverse thrust
Signed-off-by: RomanBapst <bapstroman@gmail.com>
- we have set the maximum yaw-rate MC_YAWRATE_MAX to 200 degrees and it
makes senses to leave a bit of margin between what the user can demand
and what the limits of the vehicle are
Signed-off-by: RomanBapst <bapstroman@gmail.com>
the vehicle yaws towards the next waypoint before accelerating. This is
required for drones with front vision and aerodynamic multicopters such
as standard vtol planes or highspeed multirotors.
This moves the hysteresis test out of the systemlib and makes it its own
small library. Since it still depends on hrt_absolute_time this does not
link yet. My attempt to get all link dependencies together failed.
But fix the two crucial problems:
- When to begin the ramp?
There's a calculation now for the velocity ramp initial value
such that the resulting thrust is zero at the beginning.
- When to end the ramp?
The ramp is applied to the upwards velocity constraint and it
just ramps from the initial value to the velocity constraint
which is applied during flight. Slower/going down is always possible.
Without always updating the takeoff state it will not get skipped when
the takeoff happened manually and when you switch from manual to position
mode the drone goes to idle and falls.
There are two local_position_setpoint in the position controller.
One describing the setpoint the task gives to the position controller
and a second one with the output of the position controller. I corrected
the wrong one during takeoff because the new takeoff thrust ramp runs after
the controller and not before.
The velocity ramp had problems with:
- different vehicle tunings resulted in the start value of the resulting
thrust ramp staring either higher and lower than zero thrust.
lower -> delay of beginning
higher -> small jump at beginning
- when a task set position and velocity at the same time during takeoff
(which AutoSmoothVel does) it resulted in a velocity setpoint
jump at the end of the ramp because the additional velocity
setpoint correction from the position controller was not considered.
The thrust ramp should now be very deterministic:
- always start at zero
- always end at the curreant thrust setpoint output
of the complete position controller
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.
- start from a velocity setpoint pushing into the ground
to ramp from idle thrust up.
- start with a bit higher velocity setpoint threshold to make
sure the vehicle has a chance to really get off the ground.
- calculate ramp slope from initialization setpoint to the desired one
instead from zero to the desired. this ramps up quicker when you demand
a very small upwards velocity like the AutoLineSmoothVel and
ManualPositionSmoothVel tasks do at the beginning.
- don't stay in the takeoff ramp depending on the land detector, this
is unnecessary.
The comments and variable names were partly misleading.
I grouped all members, hopefully gave them more
understandable names and adjusted the comments.
There were two rather confusing function calls one to check
if smooth takeoff needs to be ran and one that updates it.
I combined them and documented the interface correctly
making the parameters non-reference const floats.
To be able to still infer the direction of the thrust vector we
limit it to a minimal length even if MPC_THR_MIN is set to zero.
Note: This is a hotfix for certain specific applications.
The direction of the thrust vector in this corner case is very
likely to get into the tilt limit which is generally undesired.
Before if you were above the maximum altitude you could not command to
go down anymore until the position controller had overshoot to under the
maximum altitude again.
Daniel Agar