I have just bought the ArduPilot Mega 2560 Full Kit... plus the Triple Axis Magnetometer HMC5883L. I should have it built over the weekend.. then i'm off to a my mates machine shop, and i'll make the splitter plate for the lower frame onto which i am going to fit the Ardupilot. the magnetometer i'll put on the tail as suggested. I am going to use my X-cell Razor 600E. For those that dont know its around the 50 size nitro heli.
Do i need to buy any other sensors i.e. the Sonar... i can fly a helicopter all day long but this is my first time flying one with stabilisation so any tips would be gratefully appreciated.
If this works well then i am going to try and use it on my x-cell gasser. i can get up to 20 minute flights with this. But i think for the time being a battery 600 is the way to go.
i'll post some pictures when i have it all together.
I'm really sorry to hear about your crash. That's a real shame.
Good to hear the wobble was gone.
Maybe it was a typo in your mail but I think I said to reduce D to zero rather than I. Having too high a P value or a high D value tends to introduce instability.
You're right! I've posted what I think has happened in this discussion. I'll need to retest with the latest code to make sure the ACRO's P value is ok.
The advice to clear out D is now obsolete. If you put a 0 value into the Acro's P control you'll get zero swash plate movement so that's not a good idea!
Sorry to jump in here, but I am somewhat confused. What or where is the ACRO's P value? Where do you set it? That too is gone from Mission Planner (as referred to in the discussion above). Is the "Rate Roll", "Rate Pitch", and "Rate Yaw" (the top row of values in the newest Mission Planner) the same as the "ACRO values you are referring to? In other words is Rate a new term to describe these nested values?
I think putting some I back in would be good.
Yes, sorry. "ACRO" has also been renamed to "Rate" it seems! thanks.
I am still somewhat fuzzy. If the Stabilize Mode is "nested" in the ACRO mode then Stabilize is dependent upon the values in the ACRO, (now referred to as RATE) table (at least the P value). Does this mean that Stabilize mode reads values from the ACRO/Rate table and therefore those values must be there for Stabilize to work properly?
Or am I misreading you: Is ACRO/RATE a totally independent controller and only comes into play when the mode switch is thrown to ACRO? Somehow I don't think this is what you meant.
It seems as though perhaps the intent was to toss ACRO as a mode, rename it to Rate and use that as a function being called or nested by Stabilize mode: making Rate not a mode at all but rather an extension of Stabilize and other modes? Or the other way around, making Stabilize a function called by RATE. Either way they are bound to one another.
If this is true then it would seem like the top two sections of the Planner (Rate and Stabilize, all the way across) would be linked intrinsically, meaning dependent upon one another. And while we are at it, could you please explain what IMAX is? Sorry for the long questions, but I am helping Malcomb with his document and understanding this fuly will enable us to write a document that is easy to understand.
I haven't specifically tested but yes, I think the Rate values must be there for stabilize to work properly.
I think ACRO/RATE as a control method is still possible. People who want to do tricks and are skilled enough to control their heli/quad by specifying the rate of change of the roll and pitch with their radio controls are welcome to use it (i'm not one of these people I'm afraid!).
Stabilize is now dependent upon rate but rate is not dependent upon stabilize.
In stabilize mode, if you let go of the controls, the heli should return to a level position. internally the stabilize pid will compare your radio controls to the heli's attitude and say, 'oh, the heli is leaning to the left by 10 degrees, better roll back to the right at 5 deg per second...hey, Mr Rate control, do that for me". Then the rate controller kicks in and looks at the rate of change of the roll and says, "hmm..we're rolling right by only 2 deg per second, better modify the swash plate to increase the right roll".
In acro/rate mode, if you let go of the controls, the heli will remain in whatever attitude it's currently in. So if it's leaning to the left by 10 degrees, it will keep leaning. the roll controller gets direct instructions from the radio, "don't roll, pitch or yaw" and it would then compare this to the current rate of change of the axis and adjust the swash (or tail) to stop any change.
IMAX allows you to set the maximum I value of the PID controller. "I" is like trim. If your heli isn't level (say leaning to the left more than you're specifying you want with the radio), the I term will slowly climb to counteract this. The IMAX is a safety feature, it stops this I term from getting too big. If it got too big you can imagine that it might completely overpower P and/or D.
It all makes sense. But I guess to use ACRO/RATE you would have to go into the program and set the values in the table manually (since it was removed from Mission Planner). I'd forgotten that: even though you can specify a value for I, it is updated by the controller (it tries to learn) and it could conceivably get into something like harmonic resonance and get out of control by continuing to grow. Thank you for the explanation. Good stuff.
I have another question if you don't mind. When I change/move the servos using the radio in Stabilize mode the servos on my setup move very slow (almost imperceptibly so), but when I change the pitch using the left stick (cyclic) they move at the fast speed. One of the values must be doing that, but I can't figure out which one. Any ideas?