This should be interesting

Yes. It was really hard to tell from that log because Pitt tried to arm in Alt Hold and take off in Alt Hold. I’d like to see what it does taking off in Stabiilize, then switch to alt hold and get an idea of why it’s not holding altitude properly. I would think if ACCEL_Z_P is too high it would cycle the collective really rapid - that is the only response I have ever seen from it being too high. With a large powerful helicopter it can slam it back and forth into the ground and bounce up and down 10 feet faster than you can blink. LIttle ones usually do a cute little “hop dance”. Pitt’s appeared to be totally random like it didn’t even engage. But it didn’t indicate that it failed to engage on the first attempt.

Hi Pitt,
I think you should decrease you ACCEL_Z_P a little bit and try again. Please post the log for the flight. You should take off in stabilize and then switch to ALT_HOLD. You should set your IM_* params such that in STABILIZE you can hover at mid throttle. That way when you switch to ALT_HOLD the heli will not be commanded abruptly ascend or descend.

Yes, that is correct.

This is why single rotor helicopters are the most popular/common in full-scale. They have the simplest, and lightest powertrain under the largest disk area. Coaxials are at a significant disadvantage (same with intermeshing). The only reason they exist is when you have a use-case where a tail rotor causes a major problem. Or, for very high flight speeds where RBS is a concern.

Had a successful Loiter today!
Haven’t really changed any parameter.

Just flip the switch…


Awesome! Great news!

Hi Bill,
Your notch filter changes seem to be very effective. I would like to use it on my

a. 4 servo heli and
b. 600 size heli.

I am flying the 600 size heli using 3.4.6. Can you please provide firmware for 3.4.6. I am attaching my changes needed to add support for 4 servos in 3.4.6 stream. Only 4 files have changed AP_MotorsHeli.h, AP_MotorsHeli_Single.cpp, AP_MotorsHeli_Single.h and version.h. If you cannot create binary then please provide me the source code and I will build it myself.

Thanks for your help.
Sunit
Tradheli_3.4.6_four_servo_supp.zip (12.4 KB)

Sunit,
Glad to hear you had good results with the notch. I recently updated it to work on just the gyro signal and not the error. I am away from home right now but I will try to give you the link to my source code tonight when I get a chance.
Bill

Sunit,
Here is the link to my repository for version 3.4.6 that has the notch filter on the gyro signal. There are a few other changes I made to the code which include attitude error limiting, leaky attitude for Acro when speed is less than 1 m/s and swashplate behavior for different states. You can clone my repository and add your 4 servo changes or just extract my notch source code. If you want to learn more about the other changes let me know and I will get you a link to my write up on that software version. https://github.com/bnsgeyer/Copter3_4/commits/Copter-3.4
I would be interested in hearing more about your results. Please let me know how this works for you.

Bill,
I think you might be interested in this.
I just finished setting up a Basecam SBGC gimbal controller (Alexmos) on my custom made gimbal.

It has notch filter function with 3 filters for each axis (for 3 different freq) and adjustable gain and bandwidth.
Its lowpass filters are also separated into signal fiters and D-term filters.
It is not open-source sadly

Looks like a solution to low D-gain problem in helis…or is D-term not needed in the first place?
But a flexible notch filter sounds great.

Hi Bill,
Thanks for these changes. I will try it and let you know about my progress. I hurt my foot yesterday, so I do not think that I will be able to fly for next 2 weeks. My 4 servo heli is a big 800 size electric, so it would be interesting to see how it goes.

Got a question
Has anyone experienced vibration problem caused by disturbed air from main rotor?
I had high vibration reading problem which was completely eliminated by just mouning it beneath the frame instead of on top.
Now I’m deciding whether I should mount the camera in front on hang underneath for less vibration.

Pitt, I don’t know about your timed-rotor helicopter. But two-blade rotors can exhibit vibration at various stages of cyclic pitch, particularly in banked turns. And especially if they are being run too slow (low headspeed). I don’t know if it is the disturbed air from the lift pulse of the blade, or simply the noise. But I sort of think that in most cases it is the noise, or sound waves, causing high vibrations. The “bark” from helicopter blades is considerably more pronouced than the bumble-bee type “buzz” of fast-turning multi-rotor blades.

I have always had better results mounting the camera underneath vs in front or off to the side. Especially in high-speed flight. The camera in front screws up the sleek aerodynamics of the canopy/cowling and causes its own problems with wind load on a quite blunt suface - underneath not so much. The Trex 800 “Trekker” with that big contraption hanging out in front was probably one of the worst-designed unmanned flying camera platforms known to mankind - and probably why it wasn’t very successful in the sales dept.

Solid mounted camera works by far the best on helicopters at high speed. Gimbals become totally worthless at flight speeds over about 35-40 mph because they simply can’t take the wind load flying upwind at airspeeds of 60+ mph.

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How are you finding the Basecam? Are you using the 32bit?
I’ve been working on a Storm32NT gimbal, but it’s frankly a pain to work with and I’m ready to toss it in the bin, as I can’t get the serial connection (or RC mode switching) to work reliably in the field.
It’ll work on the bench and then freak out when I try it ‘for real’…not to mention that the tuning is a pain.
Here’s a vid from tonight. It was supposed to be soft-follow in the yaw (was on the bench anyway), but it decided to ignore that.


The heli could be tuned a little better (changed behaviour with weight of the new landing gear/camera/battery mount), but I suspect some of the vibration is also from the gimbal.
Also, I love auto-landings :smiley:

I’m using a licensed variance of 32bit version from iFlight. It’s basically a 32bit SBGC + built in buzzer + encoders.

Setting it up can be overwhelming for most people but Automatic tuning/calibration saved me alot of work. Encoders make thing even easier as well.

I’m now trying to mount it properly on my heli to see if it’s going to vibrate like crazy or not.

Most gimbals and controllers should work in hovering situations and at low speeds, which is what gimbals are really made for. I got an off-the-shelf Walkera G2D to work really good. The problem comes in when you start going faster. The gain to the servo motors has to increase to compensate for the wind load on the camera. So it starts to shake violently when the helicopter makes a turn to an upwind leg of the flight. And it wasn’t vibration in the helicopter - just the servo motors shaking.

Since most of my imagery work is done at higher speed, and the pitch changes of a helicopter are not a lot in forward flight compared to multi’s, I finally tried just solid mounting the camera (with a rubber cushioned mount), and had instant quite excellent results. I’ve never gone back to the gimbal.

This is a photo of the 30 degree fixed mount. You can hopefully see the rubber bushings in the mounting points of the camera holder. And I added a rubber damper ring to the upper bracket. This works quite well on both the piston helicopters (lots of vibration) and the electric.

New photo by Chris & Kristin Olson

Just figured I would inject a quick note here. So the other day I had a spare few minutes and deceided to charge a couple packs. When I hooked them up I figured what the heck and used the paralell harness instead of series so it was 6s vs 12s. Some quick math came out to 1100rpm at the full 4.2 volts under ideal conditions. Actual headspeed was just south of 1000rpm and it flew great, landing headspeed was right around 900. Had to apply a degree or so more pitch to hover but generally I was astonished at how well it flew and the Pixhawk 2.1 seemed to be happy as a clam flying around in stabilize mode. Granted I will not be flying on 6s at that low of a headspeed, but i just really wanted to see what flight time I came back with and also how the Pixhawk handled such a drop in headspeed without any parameter changes. I had the heli in the air roughly 18min and probably could have flown quite a bit longer but was starting to get sick of flying… lol. Packs were roughly 3.85v at rest after landing, so roughly 50% of capacity.
Interesting test I guess for sure. Ive flown plenty of helis LHS before, but usually with a 7s pack and then only 1 pack and its always on my lighter 3D helis, not my heavy aerial pigs like this trex 800 conversion. Neat stuff I guess?
Back to the task at hand, hopefully getting my first longer auto mission in this weekend with much faster forward flight speed. My short auto tests havent shown me much yet as they were short, and very slow. I guess it told me whether it was going to blow up or run away on me or not?
Tim

Tim, did you adjust your throttle setting after switching down to 6S? I run my Trex 500DFC on 4S with a 6S motor and gearing. And get normal headspeed around 2,100-2,200 rpm. Just that on 6S I ran the throttle setting at 50%. On 4S I run it at 85%.

Chris,
Yeah, forgot that bit… I did change PWM out to 100% on RSC, so I guess I did change a parameter in MP before arming and spooling up. I should have said, “I did not change and PID tuning” parameters. My bad. :confused:
I don’t know how useful that low of a headspeed would be? I did not try the Loiter controller or auto so I have no idea if it would even fly well at high speed. Maybe got up to 35-45mph in FF.
Tim

It all depends on the disc loading. It would likely work fine for general UAV use at lower flight speeds. Then when you want to fly fast, ramp 'er up.

You can use RSC mode 1 too, and have a couple different idleups with the flip of a switch for different payloads or flight speeds. I set up a heli that way and it works fine using the governor (on a piston engine). Don’t know why it wouldn’t work on electric too.

Sunit,
Sorry to hear about your foot. Hopefully you’ll be better soon. Look forward to see how the notch works for you.