I've recently put together a quad with DJI FlameWheel 440 frame, ESCs and motors and APM 2.0
I have few problems:
1. in Stabilize mode it's extremely difficult to hold altitude: when I slightly increase the throttle to avoid crashing the copter continues to ascend and even small change causes it to descend and it bounces up and down. I tried changing the controls but they seem to have no effect so if anyone you guide me which ones to pay special attention to, that would be great. (note: in loiter mode it's much more stable).
2. the copter also seems to have problems with holding position despite solid blue GPS light. I managed to put it to stable hover in stabilize mode and then switched it to loiter mode then without touching the sticks observed what's it doing - the copter was drifting to random positions within 15-meters radius - I would expect better from GPS (note: it was open space and no wind at all).
Any help would be very much appreciated
i will do this upgrade on my Turnigy 9x http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A4280... this afternoon.
hope this will solve the problem.
modified the Turnigy 9x now i have throttle curving and a 6 Pos. switch
I presume being an Aussie you are flying with a Mode 1 radio.
I tried this initially but found that the throttle on the same stick as the roll was far too difficult to handle.
Switched the radio to Mode 2 and have had a much better experience.
You might mean Mode 3 - Throttle still on the right, but Rudder and Ailerons swapped. I fly this way, and it makes much more sense than Mode 1.
No I have switched the throttle to left stick and aileron and elevator on right stick.
Yank and bank when flying aircraft.
Easy to do on a Turnigy 9x.
Glad to hear it worked Michael! I switched to a Spektrum controller, so I have six channels and a throttle curve. The quad flies like a dream now!
Guys, I would not recommend using throttle curves for taming the throttle.
It will complicate the PID tuning. What I recommend is to lower the throttle P value, say by small increments, say 0.10, to reduce the sensitivity.
Also, there should be no notching on the throttle stick. It should be smooth, otherwise it's very hard to get good throttle control. If your transmitter stick has notches, either file them off or put a piece of electrical tape over the notches to smooth it out, yet keep the tension on the throttle.
Ellison I'm going to have to respectfully disagree. I don't want the throttle to be less sensitive, I want it to be more finely controlled. By curving the throttle, I'm simply crowding the high and low throttle values that I don't really need into the ends of the stick's throw. The pwm values are the same, its just in the middle of the stick's range it transitions through them slower. I don't see how this would mess with the PID, its just as if I'm moving the stick in a different manner.
Also, I swear by the notches on my throttle. They are very fine, so if my quad is dipping, I can move the throttle up by one or two notches to level it back out. They keep me from overshooting the stick, because I can count on the fly how many notches I've moved by.
Hmm, well maybe I misunderstood. If you want more sensitivity, increase the throttle P by small increments.
Also not sure if other have mentioned, you should calibrate the ESC individually so that they are set to the right range of the throttle of your receiver. I had a similar problem with my DJI Naza, where the throttle was not responding properly too.
The PID system sets the motor speed so that when you change your sticks, the change in PWM results in a motor speed. PID is expecting a linear change in stick input PWM values. If you change the throttle curve, then the throttle input is no longer linear. You can compensate by adjusting the PID values, but at some point, the PID is not able to handle it. You're correct though, throttle curves are like moving your sticks faster or slower at the top and low ends, but PID will breakdown for such extremes. Like I said, it complicates the PID tuning process to have to account for a non-linear throttle curve.
The throttle notch is a preference, most flyers hate notches. We just can't get the throttle stick to stay between notches, without holding it tightly. A smooth throttle stick, with enough tension, will stay where you leave it.
@ Ellison: thanks for your reply - could you please point me to specific PID name that I need to play with?
I don't have the Mission Planner in front of me right now, but can't remember if there was Throttle rate PID (well maybe my memory starts to fail ;)
What do the "Stabilize Roll P" and "Rate Roll P" do? Are you referring to one of those?
Also, I'd appreciate if you could tell me whether I need to increase or decrease the values?
Thanks heaps in advance.
Yes, sorry, my bad. "Throttle Rate P".
If you are flying Stabilize mode, and want to tune the P you can adjust the Stabilize Roll/Pitch/Yaw P's. Same for Rate. Rate means only for gyros.
Will adjusting the Throttle Rate P make a difference in the stabilize mode or Loiter only?
I'm fairly happy with the response in Loiter mode, but Stabilize is horrible.
I also need to tune the Roll and Pitch as the copter seems to be too jerky when pushing the sticks too far - I'd like it to be less sensitive. Yaw in the other hand seems very sluggish so need to change that one as well.