I have done more ground testing and found that when the plane is below the ground steering level of 2 meters, the elevator will compensate for yaw movement only in extreme situations. The plane has to rotate more than 90 degrees a second, rudder compensation kicks in. That is a long time to wait for rudder compensation. I am not sure what variables are driving this. I would like much more immediate yaw correction than that. Any idea how to get more response in the yaw? There is no yaw P to help me.
While I’ve never done this before myself, I’m looking at the source code. I suspect you want to tune your Ground Steering controller. Can you find some parameters prefixed by “STEER2SRV_”? I hope you can find things like:
STEER2SRV_P
STEER2SRV_I
STEER2SRV_D
STEER2SRV_TCONST
STEER2SRV_IMAX
STEER2SRV_DRTSPD
and some others.
Also, your 90[deg/s] observation was a good one! The default value for GROUND_STEER_DPS is 90, which seems to indicate that at over 90[deg/s] the rudder maximizes deflection to counteract. You’re right that you definitely want the rudder to steer the plane well below this “bad-case limit” type of behavior.
Thank you for the suggestions. I tried turning all of these dials and nothing seems to impact the response to yaw. Maybe this is because I am testing the plane in hand and it has no forward motion. I do need a way to test these settings on the bench though. I turned that GROUND_STEER_DPS down and up too. No change at all to the rudder response. Still seems to take atleast 90 degrees/sec for the rudder to chime in. Maybe this is a question for the Git Hub?
It sounds like something is preventing the STEER2SRV section of code from being active, but I don’t know if that’s some parameter(s) or some conditions (altitude, speed, etc) not being met.
I think you’re asking at the right place, but unfortunately I don’t have any actual experience with this. Can someone else chime in?
if you post a DF log of an attempted auto-takeoff I can take a look
A key parameter is GROUND_STEER_ALT, the altitude below which ground steering is used.
also note that you can use ground steering in FBWA mode. I usually tune in FBWA mode, by doing test takeoffs, and throttling back before liftoff. You should be able to go the full runway length without any rudder correction.
Please also post a photo of the plane. If it is a taildragger, then a photo of the tailwheel may help. Some have a high castor (angle of the wheel strut) which causes a lot of issues with auto-steering.
I will post a photo of the plane and a video tomorrow as I will do more testing then.
Below is a link to my last test that resulted in a crash. You can see that plane yawed to the left hard. I help restraining myself from correcting it as I thought the controller would correct it but it did not happen. I attempted to avoid the crash with the windsock pole with up elevator. More files to come tomorrow. Thx
On a side note, I see that the pressure in the fuselage is not well balanced. Upon throttle up, I get a 13 meter drop in baro altitude. Not sure how that impacts the controller but I will try to correct some of it. Too many breathing holes in the front of the fuse and not enough area in the back for the air to escape. I never thought to look into this before.
I made some progress on this issue. After putting a camera on the plane to look backward on the tail, I could see that the left turn the plane made when winding the motor up was actually commanded. About 2 seconds after throttle up, I could see momentary left rudder that pushed the plane atleast 10 degrees to the left. I looked over my configuration and noticed I had my magnetic declination setup wrong. I had it set to 7 degrees when it should have been -8. I did a retest and the takeoffs are better. Some are straight and some do drift to the left but not nearly as bad. I am not seeing the left being commanded in the video. I will have to see what the logs indicate next.
Another issue I am having is I see I am only getting 94% throttle (1898-1900 us) on take off. When I manually take off, I can see it registers 100% or 1947us. TKOFF_THR_MAX is set to 100. Any idea why I am not getting the rest of that 5-6% power?
I’m doing some digging… maybe some of these ideas will help?
Do you get 100% throttle when flying in MANUAL and FBWA modes?
Do you see THR_MIN and THR_MAX parameters? If yes, what are their values?
Is it easy to try setting TKOFF_THR_MAX to 0? That should set TKOFF_THR_MAX = THR_MAX.
Probably not relevant, but what is your TKOFF_THR_SLEW value? Again, if you set it to 0, it will use THR_SLEWRATE instead.
What is your value for THROTTLE_NUDGE? If you have this set to 1, and your stick is held down during takeoff, that might limit your maximum… if this is the problem, if you push your stick up during takeoff, you should see max throttle achieved.
If none of these solve the issue, I think the relevant code is in Plane::set_servos_controlled() inside servos.cpp…
Strange. I setup a test where I was going to start the route with the stick idle, progress the stick to full throttle two seconds later and then go back to manual. All three showed 100% throttle. Not sure why it is working fine now.
Hunt0r,
Thx for the help. I will do actual air testing on Monday if the weather holds. Looking at past test, they also throttled to 100% on auto modes. There is something odd that happens with my config on a random basis. For instance, I have had my voltage failsafe go off after 1-2 min of flight as the reading of the battery is off. I charge my batteries to 90-95% which puts them around 16.2-16.3 volts. most of the time, the voltage monitor on board measures it right. I have seen a 16v battery read 14.x volts. I unplug and plug back and it corrects it. Maybe there is residual voltage in the system that is throwing it off from the previous flight?
i tridge, I have similar problem on my plane , it roles to the left on my last 2 flights and crased. on log files i couldnt find an error message. could you help to find out that problem. I use arduplane 3.8.4
