Satish,
H_COL_MID does not affect the collective curve in acro, stabilize or any flight mode. It only tells the code where zero thrust is so in non-manual throttle flight modes it knows where to stop with downward collective while on the ground. Typically we recommend -2 deg to 10 deg for H_COL_MIN and H_COL_MAX respectively for non acrobatic setups. Then your IM_STB_COL_1 is typically close to 0 and IM_STB_COL_4 is close to 100.
It would be good if you post your parameter file so I can look at your set up.
Hi Bill, thanks for the pointers.
alzrc450fbl-1.param (13.8 KB)
Well after several hours, taking the complete FBL head apart, checking for any sloppiness (I have to say the fbl kit i got is full of issues, and when that happens, itās tough to get going by the book) and vertical play in the head assemble and fixing it, and then i noticed my FBLās washout base (in my case itās not integrated into the head-housing, rather separate piece, which is supposed to be phased in properly with the head and tightened) would not grip the main shaft no matter how much i tightened. That meant the 2 link rods were not going to be where they should, they rather leaned on as the head speed when up. This resulted in even more -ve pitch as the blade grips got pulled down. So my entire pitch setup was off. Well i could not get the washout base to grip no matter what, i finally (to give a try) CA glued it to the shaft and then went on with the pitch setup to get about -2 to +11 in stab mode. I later noticed the screws for the WB were supposed to be one longer and one shorter, the longer meant to help it tighten flush with the shaft, but not in my case. I almost ripped the screw off trying to tighten it further and gave up and went for CA, knowing this could be disaster if it gave way in flight. But this is just to be sure the rest of the settings are ok and it will fly. I will probably replace the head assembly later.
I did a test run and it finally took off. But not without some things still to figure out.
- The tail needs more authority - i could get it where i wanted it to be and it will hold there, but with throttling up or down it tends to loose the heading, let me know where i should look for
- The head speed seems to be OK all the way up to mid stick, but then it seems to drop a bit and stays there (lower) all the way up, and increases as i come down the throttle before throttling down completely. Not sure if this is a setting issue or a lipo issue.
- The pitch seems ok now, in the good range.
- And lastly, i had to give right-roll most of the time to keep it in place, else on level, it would drift left in a leveled flight.
Thank you and all for everything so far.
Satish
What do you mean by throttling up or down? Are you saying when you lower or raise the collective or actually setting a different headspeed on the ESC?
How is headspeed controlled. Are you using the governor of the ESC? throttle curve?
If you are in stabilize mode, this could be one of two things. First check to make sure that your transmitter joysticks are calibrated and that the RC1_TRIM is correct. One way to do this is got to the flight data page of mission planner and in the lower left side you will see some tabs. Select the Status tab and then scroll to the right until your see the ch1in label and that will show you the PWM of the transmitter roll stick. verify that is within the DZ of your TRIM value.
If it isnāt that, then it is the ATC_HOVR_ROL_TRM. This is the roll angle needed to overcome the tail thrust that is try to push the aircraft to the left. Therefore a right roll attitude is needed to hold the aircraft stationary. An easy way to see what value this needs to be would be to hold a steady hover and then pull the roll attitude from the telemetry log or the dataflash log. This number is in centidegrees. Right now yours is 300 which is 3 deg. So it sounds like this just needs to be a little higher.
Yes, I mean when i raise or lower collective, the heading is lost, i have to give some rudder inputs to point the nose where i want it to be. In normal heli setup we increase the head-hold gyro gain, iām not sure in AC how things interact with each other.
Iām using throttle curve for H_RSC_MODE. It seems to climb well as i throttle up, and then seems to drop when i need it most (in hover pitch), so the heli feels sloppy when it lifts.
I will check the RC1_TRIM etc coming weekend and report.
Thank you Bill.
-Satish
and i have attached the PARAM file in my previous reply.
Thanks
Just another question Bill - How do you do the ESC calibration for MAX and MIN with AC for heli? We normally do it directly with the Tx, Rx and Esc before setting up anything. But the ESC is now listening to AC, is there any calibration needed for the ESC/RSC output channel after connecting via flight-controller and AC as well, like we do with multi-rotors and AC?
I donāt normally calibrate the ESC for my helicopters because I am always using the internal governor of the ESC. I would recommend that you do the same. Iām not sure why you were using the throttle curve unless your ESC does not have an internal governor feature.
If you have to use the throttle curve, I donāt know that calibrating the ESC is actually necessary. By properly setting up the throttle curve you will limit the ESC from hitting the end of its control range.
Ok Bill i will look at the ESC gov option - we use the ESCās internal gov feature ? or anything we need to also set on AC? Also can you see in the PARAM settings, anything that could be limiting the throttle/headspeed above midstick in my case?
Thanks
Satish
There is nothing in the code that will limit the head speed unless you are using the internal Governor of ardupilot (new in 4.0). My thought is that the head speed is drooping because of the load on the rotor while hovering and climbing. That is why I think you need to raise the throttle curve for collective positions above mid collective stick. So I would recommend raising H_RSC_THRCRV_50 and H_RSC_THRCRV_75. And I would question whether setting H_RSC_THRCRV_100 to 1000. You would have to do a full collective climb out to see if the rotor speed droops.
Dear Bill,
Thanks for the guidelines - I was able to have a controlled hover finally and very happy how it turned out.
I had to increase the H_RSC_THRCRV_50 and H_RSC_THRCRV_75 like you suggested.
H_RSC_THRCRV_100 was anyway 1000. No oscillations thankfully. I have to (about every 5 seconds) correct the tail and hold right roll to stop it from drifting away left.
I now hope to be able to focus on
- Iām still having to hold right roll, else if i center the stick, the heli is stabilized but starts drifting left.
- Some more tail tuning
I;m not sure how much of a tuning is good enough in STAB mode - how would you define a stabilized 450 heli with AC?
Thank you all.
-Satish
Bill, just a question - should I be checking the ch1in PWM value is within the DZ of the TRIM with the sticks centered?? and what if theyāre off the DZ
Regards,
-Satish
Dear Bill,
Just did a check - my RC1_DZ = 20, RC1_TRIM = 1533, and ch1in = 1493. Is that the reason that i cannot fly in center stick?
Regards,
Satish
Yes, that is what you should check. If they are off then you should adjust the TRIM value to the PWM you see for the ch1in wi th the stick centered.
Yes that is the problem. Adjust the RC1_TRIM to 1493.
Thanks Bill, I have that sorted now. Had a test flight, probably not drifting as before, but a little and still holding right roll, cannot say its in the slot yet.
I try the other param you mentioned and see.
Regards
Satish
Just remember if the ch1in shows that it is within 10 pwm of the trim value then the drift is not due to the control position. Most like it is due to your atc_hovr_rll_trm param
Ok. I donāt know how there was so much diff between the two, but i just did a re-calibration of all sticks and it sorted out. I hope thatās ok ?
I will try the ATC_HOVR_ROL_TRM param and update - too windy at the moment.
regards
satish
Hello everyone,
(Bill, this is on another heli setup iām trying, not the one weāve been discussing which is a MATEKSYS 405 WING which is fantastic so far)
I know old FWās are not supported, but I hope someone can assist me. Iām trying to give some life to an old APM mini 3.1 for a 450 flybar heli with AC 3.2.1. I have everything setup, RC calib is all fine. My servoās are getting their signals and i can go for swash plate leveling. But i just canāt get output on ch8. I can hear the ESC initialize, Iām able to ARM and see the RC throttle input increase (under STATUS tab) as i throttle up, but i see no output being sent on ch8out, it stays at 973. Thereās output on all other channels from ch1out to ch4out. I would check like you mention SERVO08_TRIM and SERVO08_MIN, but on AC 3.2.1 I canāt find that PARAM. Anything iām totally missing here??
Secondly, I see the servo movementās on the cyclic servo when and stick input is given (except rud servo) is very little, why is that?
Have attached the PARAM file.
450H.param (5.4 KB)
Thanks in advance.
-Satish
Iām learning more every time i discuss with you Bill, thanks for all the experience sharing.
I see why you mention using a internal governor or the ESC. Iām sure my Turnigy blue series ESC has GOV settings which i never played with for years, i will have to check that out. So what will be the H_RSC_MODE while using the governor on ESC - RSC Setpoint??
- How to find the ideal setpoint(s) for the ESC, i mean do we first fly in RSC Throttle curve mode like i am doing now, find the stick position on tx and related PWM output in MP to get a steady hover and use that as a starting point, or is there a better safer way?
- So if i understand, we get to a good hover head-speed and then basically play with pitch curve?
- The H_RSC_THRCRV_xx settings are only for RSC Throttle curve mode?
- And itās not a good idea to proceed with RSC MODE Throttle curve for AUTO flights? or itās impossible?
I just checked my tail rotor setup alignment, and it was tilted to left (anti clockwise) w.r.t to the main-shaft by a few deg - possible reason why i have to hold right roll to keep it in one place else it simply drifts to left ?
I did not have a calm weather yesterday, so didnāt want to check with the ATC_HOVR_ROL_TRM settings. With the above tail rotor condition i had to up it to 500 to see some improvement w.r.t to holding right stick, it came down a bit, but i hope after correcting the alignment i will see better improvement. Another weekend to wait 
Thanks & regards,
-Satish
Satish, yes this was a little before my time. So I donāt think I can help you. I briefly looked at the code and it is significantly different than what we have today. The rotor speed controller was not even in there. I played with this briefly when I first got into using ardupilot but then AC 3.3 was released and that had significant improvements. Sorry.
Yes if you are using the internal gov of the ESC, you use RSC_SETPOINT.
Are you talking about setting the throttle curve points?
Probably not.
The RSC throttle curve is designed to work with auto flight mode.
Hello Bill, Yes i understand as i see AC Heli has undergone significant (and good) improvements in recent years. I was just hoping to make good use of old FC;s during this lock-down as itās extremely difficult to get new parts shipped especially in India now. But i did try with another FC, an REVO board, and i started getting output on ch8. So i;m really not sure why i cant get the same on a APM 3.1 mini - would have been perfect on a 450 with such small form-factor.
Well, sorry about the way i put things - I meant, if weāre going to use RSC_SETPOINT, do we still need to setup the throttle curve i.e. H_RSC_THRCRV_1 to 4? as i thought we set these only if we used the RSC Throttlecurve mode, please correct me.
Regarding the left-drift: had another question, is it suggested to add a few deg or pitch on the tail at neutral (rate mode setup) so that it holds the heading better in stab mode? would that also reduce the left-drift? In my case i didnāt bother much about the tail pitch in neutral, just have it centered as much.
Iām still far from using the governor setup, i guess i will do that once if have the drifting under control.
Iāve also seen chris mention many a time about AHRS TRIMās to stop the drift, should I be looking at that and is GPS reguired to be setup for that to work?
I feel the tail is a bit loose (if not hunting) as it tends to go off-heading and comes back. Do i need to play with ATC_RAT_YAW_VFF or should i try increasing the throttle curve values?
Regards,
-Satish