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.
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.
There were accidents because when missions lead through an obstacle
and it should be avoided but the setpoints from the external obstacle
avoidance module are suddenly missing the mission is continued into the
obstacle which results in a crash.
PositionControl: update comment about the order of thrust and position
mc_pos_control: reset setpoints to NAN if required
MulticopterLandDetector: consider to be landed if vehicle is not armed
mc_pos_control: initialize landing struct with landed
mc-pos-ctrl: adjust thrust-setpoint and yaw during ground-contact/maybe-landed without capturing
that information within vehicle-local-position-setpoint topic because that information
does not belong to user intention
PositionControl: set local position/velocity setpoint to NAN if not used in the control pipeline
mc-pos-ctrl: Fill vehicle_local_position_setpoint_s structure as follow:
The message contains setpoints where each type of setpoint is either the input to the PositionController
or was generated by the PositionController and therefore corresponds to the PositioControl internal states (states that were generated by P-PID).
Example:
If the desired setpoint is position-setpoint, _local_pos_sp will contain
position-, velocity- and thrust-setpoint where the velocity- and thrust-setpoint were generated by the PositionControlller.
If the desired setpoint has a velocity-setpoint only, then _local_pos_sp will contain valid velocity- and thrust-setpoint, but the position-setpoint
will remain NAN. Given that the PositionController cannot generate a position-setpoint, this type of setpoint is always equal to the input to the
PositionController.
mc_pos_control: switch to designated initializer for landed
It's less error prone because it produces an error on every discrepancy.
- landing_gear: refactor state name
- Add the keep state to the landing gear message
- Adapt FlightTaskManual, FlightTaskAutoMapper, mc_pos_control,
to review message definition
Necessary because NuttX defines pollfd differend from
the POSIX standard. The difference of field order makes
use of C++ designated initializers to compile for both
platforms impossible.
If the landed state was set before the position controller starts it
would get updated with the first poll_subscriptions() anyways. But it's
not on all posix and nuttx platforms I tested and the deleted statement
just copies the zero message into the struct which is already zero.
* attitude and rate setpoint message: use 3D array for thrust demand
* FixedWingAttitudeControl: rework airspeed scaling
* move airspeed and scaling calculation into separate method
* if vtol in hover and airspeed disabled use minimum airspeed instead of trim airspeed
Matthias Grob