I have been working for quite a bit on integrating a cube orange in a big traditional helicopter UAV.
All the common setups have been done and now it is time to perform the first flight.
I would like to do the firsts hovering in a full manual mode, without any control loops (or minimizing it a lot) in order to analyse the logs for a future tuning.
I wonder how this is possible, the control loop schematics are helpful, but difficult to put values on parameters…
Helicopter characteristics :
@MaximeDM I agree with @Ferrosan that you would start with acro but there are certain settings that can be made to change it from complete pass through to providing rate feedback only to then full attitude and rate feedback with command shaping. Progressing in this fashion can only be done in acro mode but it will allow you to prove out your system in a buildup fashion.
For all of the options below, set these params just to keep from having other issues
ACRO_TRAINER = 0 - Disabled
ACRO_BAL_PIT = 0 - disables virtual flybar feature
ACRO_BAL_RLL = 0 - disables virtual flybar feature
Turn off the failsafes and the crash check just so you don’t get any unexpected transitions to autonomous modes or disarming
OPTION 1 - Complete passthrough
For complete passthrough for pitch, roll and yaw:
Set these params
H_FLYBAR_MODE = 1 passes through the pitch and roll commands with no PID loops
H_TAIL_TYPE = 1 using the tail type of servo with ext gyro causes the yaw command to be passed through with no PID loops.
I am not sure that this buys much more benefit than the next option. Although the next option has command shaping, you would still have effectively pass through as long as you kept the rate PID parameters zero
OPTION 2:
Rate only PID loops:
set these params
H_FLYBAR_MODE = 0 - turn off flybar mode
H_TAIL_TYPE = 0 for servo and allow Rate PIDs
ACRO_OPTIONS = 2 Use only rate PIDs and no attitude feedback
OPTION 3: Full control system
H_FLYBAR_MODE = 0 - turn off flybar mode
H_TAIL_TYPE = 0 for servo and allow Rate PIDs
ACRO_OPTIONS = 0 Use rate and attitude PIDs
So I have been incorporating a Bell 206 dynamics model in SITL however I have no PR’d it to master. It is in my personal repo here. I think I have it mostly finished. It gives a good idea of what it would be like to try and fly/tune a larger helicopter using arducopter. I hope to be finished with it and possibly PR it soon. If you need help getting it set up in your SITL environment, let me know.
OK for the parameters, I think I will start doing this way. Indeed this option let me tune the helicopter as accurately as I can, and also it is easier to figure out some small mechanical issues.
I guess option 2 and 3 will be steps for the future tuning. I hope starting with the first option for small hovering, and analyzing the logs will contribute to determine the starting parameters for rate PIDs and Attitude then.
What do you think about that ?
I have seen the video of your work on the SILT. But I am running Xplane 11, not providing the Bell 206.
The simulation is working, but I am not able to tune a new heli, even from your param file.
But for sure it is an awesome tool to play with parameters and determine a tuning procedure for the real UAV.
So by semi rigid rotor head do you mean that it is a teetering rotorhead that is underslung? Is the teetering hinge free or does it have some spring or other mechanism that provides some stiffness to the hinge?
I’m not sure what you mean when you said it lets you tune as accurately as you can. What are you tuning, this is straight passthrough.
I’m not sure how you will be able to determine the values for the rate PIDs from your flights using the passthrough mode. If you could complete a frequency sweep then that would be pretty useful but most I think you would get from flights with passthrough would be ensuring a good mechanical setup. you would be able to tell if the swashplate needs leveling and what the hover roll attitude would be. It just depends on how comfortable you are as a pilot flying it unaugmented.
In fact the rotor head is quite similar to a Bell 206. Means that the spindle can rotate around the main shaft, but a blade holder cannot rotate around the spindle (flapping axe) like the R22.
As you said, I will use this mode to set the tracking, the levelling of the swatch plate, the tail neutral….
I am just curious how th P I D settings of such big size helicopter is set. I have built a 450 size and 800 size helicopter and the P I D settings from 450 to 800 were getting smaller. 800 size is at most 10 kg MTOW helicopter so how will the tuning of a 30 kg heli can be done ?