I've been working on testing and making a few changes to AC3.0 lately, and did a whole bunch of test flights today which went very well. AC3.0 is simply amazing, and there's more good things to come, including a real acro mode that myself, Leonard and few other people have been working on. Hopefully it should be released in 3.1, along with the changes I'm making to the TradHeli code. Most of what I've done to 3.0 are relatively minor, the official 3.0 does work fine on TradHelis, but my changes make it more stable and precise, and perfect the take-off and landing.
I shot a video to show of the performance of the system. I was hoping for a very windy day, but the weather hasn't been coorperating lately. Not only is the wind not very high, but the space weather is bad and I experienced a lot of GPS drifting today.
Anyway, here you go. It's a bit long, but I wanted to be thorough.
Comments
Thanks, it's reassuring that the board didn't just fail out of the blue. As I'm sure you know, crashing a trad heli, especially a quality one, generally costs a lot more money and time than crashing a quad.
A conventional gyro on a heli shouldn't know the difference between a yaw command from the sticks or from APM. And in the absence of a command, it just holds current heading on its own. So I'm not sure I see how it would interfere with yaw inputs from, or confuse, whatever source. I have a Helicommand stab system on my 600 that doesn't care a bit if its internal tail stabilization or an external one is used (I'm using an external one). I also have a heli gyro very simply plugged into the steering servo on a very fast r/c offroad car (XTM Rail). With this the car runs more or less straight across rough ground at much higher speeds than are controllable manually, but control via the steering wheel is unaffected. Anyway, my point is that with tail stability/control being so crucial to a heli, maybe looking at the mature existing tail gear and integrating APM with it might be appropriate.
It looks like the SPI bus failed. I did a couple test hops to work on the COLYAW, and on one of them it just went completely out of control in oscillation and crashed. The data logs show that the sensors on the SPI bus reported crap values suddenly. (ie: MPU6000 showing 800 deg/sec rates, and the baro jumped to -16,000)
This board has been through a lot, it's been crashed heavily a number of times. And there were warning signs, over the past few days it would sometimes not boot up properly.
The 450 tail is composed of a collection of parts. The Tarot 1-piece tail box which is a nice piece, and a metal rocker-arm. Regardless, there's about 1 mm play in the pitch slider, the majority of it coming from the fit between the pitch slider ball and the rocker arm socket, and the free-rock in the bearings of the rocker arm. I don't have a lot of experience to know how much play in that system is "normal", but I know that any play is too much for a simple PID system to respond to properly, which is why I blindly state that it's crap. And I know that generally speaking, the singly-supported rocker arm is a horrible design for any mechanical linkage.
On my 600, the tail works much much better. But I can clearly see the difference between the stock singly supported rocker-arm setup, and the dual-support that I switched to. I was able to almost double the gains. In case you haven't seen this, here's a video from last year showing the 600 hovering in tail-in to 40 km/h winds. There's onboard video starting at 2:55 from a hard-mounted camera with no gimbal. It looks pretty good to me, and that is with the singly-supported rocker arm tail, and I also improved the rate controller since that was shot.
But I think most of the problem in the 450 video was due to the collective pitch compensation going in the wrong direction. So the Alt_Hold is busy on the collective, and the COLYAW was sawing away in the wrong direction on the tail.
You may still be able to use an external gyro, but I'm not sure. I've never used one myself, don't even own one. And it's been a long time since anybody tested that. I'm concerned it won't play well with the Body-Frame Stab Mode.
What sort of "inflight failure of the APM" do you think might have happened? And regarding tail mechanics, the statement that 450 mechanics are never great is based on what? Blade's toy-class 450? My T-rex 450's tail never even wiggles. A servo specifically up to the job is crucial, as is zero slop. I hope the issues are just due to the quality of the mechanics because if this system can't control a properly set up 450 tail I sure wouldn't even think about installing it in a big bird. Is there a reason a conventional heli tail gyro can't be used in conjunction with APM?
John, yeah, I'm not happy with the yaw either. That is with APM doing the tail control, no external gyro. Part of the problem is simply mechanics. Mechanics on a 450 scale are never great, and neither is the servo. There's a lot of slop in the system which doesn't help.
Also, after that video was shot, Joly reminded me of the potential that the Collective-Yaw compensation was working in the wrong direction. The parameter needs to be negative instead of positive. So whenever the collective increased, it was yanking thrust instead of adding it. I was just working on that yesterday morning, and saw an immediate improvement. But then I seem to have suffered an inflight failure of the APM and the heli crashed. So it will be down for a while.
I have to figure out if the negative collective-yaw compensation is the same for all helis, indicating the algorithm is backwards, or if it's just depends on servo reversing. I think this is the case. It's funny, because we had discovered this about 6 month ago, but I forgot about it while working on all the 3.0 stuff.
The tail performance was quite acceptable on my larger heli with better mechanics. Particularly with the Align double-link pitch slider which is a much better.
Hi, nice work. Yeah tail wag is also a problem i would be interested in how to solve proper…
i have been fiddling with the PID values for yaw for quite a while now and as far as i could observe they were best with 0 to low I-Value and as high as possible P (0.43 in my case) and according D parameter (0.004).
My tri runs on 4s with 12" props at a distance motor to motor of approx 29"/73cm and a total mass of 1.6kg (including gimbal).
is the i-value not of importance or why can't it be tuned via channel-6 ?
thanks Chris
Looking good. But I did see some slight tail wagging going on, are you running a dedicated HH gyro for the tail or is the APM controlling that also?
Jamie, yes, the parameters are very very different from a quad. And it's been a while since I looked at the standard params that load with a heli. I mean to work on that at some point soon.
After seeing this, I am definitely getting another APM for the Blade 400. Nice work. Did you have to vary the standard params much for the 450?
FANTASTIC WORK, YOU excited me TRYING TO RIDE MY 450 FOR TESTING. . CONGRATULATIONS
Nice!
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