@bkueang and me realized that on every frame we tune the integral gain for
the roll and pitch rate controller is much too low. Usually it needs to be
increased to 0.3 or even 0.4 to have better "locked in" flight performance
and 0.2 seems like a good compromise for a safe default.
CMAKE_TESTING should automatically be enabled
but I hoped to do that in the test.cmake
target specific options and not in the main
CMakeLists. I have to see if I can make that
order work. Here the hotfix to make CI work
again.
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.
After boot the user is in manual mode and if he has an RC
but doesn't switch out the thrust gets set to the throttle stick
position. When he then starts a takeoff from tablet the thrust is still
high while arming and the land detector immediately sees a takeoff
skiping smooth takeoff from the position controller.
- 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.
Example: Before when you passed "make tests TESTFILTER=Attitude"
and subsequently "make tests TESTFILTER=Atti" it found the string
"TESTFILTER=Atti" in "TESTFILTER=Attitude" and hence the check if
the configuration is already correct passed. The fix checks for
the configuration parameter including the subsequent space separator
and after that strips the space away again such that the list
VERIFIED_CMAKE_OPTIONS doesn't contain trailing spaces.
visibility.h is included globally in PX4 via cmake compile flags.
It contains poisoning the exit() command which is used by gtest
to close the test application. Removing the flag for gtest compilation
fixes the compile error:
gtest.cc:4757:7: error: attempt to use poisoned "exit"
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.
the condition to enter the rc mode switch evaluation was neglecting
the first connection of an RC when "no RC switch changed". this means
depending on the actual initialization values of _last_sp_man and the
desired mode preselected on the RC while connecting it would not get
evaluated.
It wasn't possible to fly faster than cruise speed even if planned
in the mission.
Limiting the planned cruise speed is necessary because
the smoothed trajectory mission plans to the _mc_cruise_speed and
if that's higher than the maximum it gets capped for safety by the
position controller and the result is a jerky flight.
- Remove unnecessary in between rate limits member vectors.
- Only switch the yaw rate limit in auto modes,
other values stay the same anyways.
- Fill gain vectors with parameters in one line.
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.
Some threads do not exit and are still running when
trying to exit SITL running under Windows in Cygwin.
This problem was introduced with:
- posix shell #10173 because of strating a child process
for the startup script and mixing up the signal handling
(only Ctrl+C broken)
- lockstep #10648 because of simulator threads not
stopping gracefully anymore with timing race conditions
(no graceful exit possible anymore)
I leave the SIGINT handler on its default implementation for
Cygwin which kills the process and all its threads when pressing
Ctrl+C.
This hotfix at least allows the usage of Ctrl+C again instead
of forcing the user to use the task manager to shut down
px4.exe going crazy on CPU load instead of exiting
everytime.
instead of the derivative of the vertical position which is
not the same value when using the ekf2 estimation.
Using the position derivative resulted in delayed landing because
the value for some reason often bumped over the theshold before
slowly converging towards zero while the velocity was within expected
accuary in all these cases.
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.
In 5bb9babc20 I made MAVLink send a
rounded up integer instead of rounded down. This makes sense in practice
because the low battery reactions happen exactly when the reported number
switches in the UI. But here we want to provoke an exact 50% in the UI so
we stop counting at 49.9%, it get's rounded up and we see the expected
result.
In 3e6e1f5c2b the simulated battery
percentage was reversed. I'm assuming because of the possibly
missleading variable name. Now I'm fixing it by switching the
maximum and minimum voltage such that the name is not misleading anymore
but it still works as expected.
Setting PWM_DISARMED to 0 results in no PWM output to the ESC for the pusher motor.
Most ESCs start beeping endless in short intervals if they don't get a signal.
I remove changing this parameter which is 900 by default to always command the motor to stand still.
Matthias Grob