ArduCopter 2.8 / 2.8.1 released

Alexsey Novik November 5, 2012 at 3:12am

HI!

I have two questions:

1. How can i change throttle gains? When i arm my 3DR Hexa (APM 2.5 with 880kv motors and arducopter 2.8.1) and move throttle stick to minimum it starts and speed is increasing by itseft to infinity. It will lift until i move throttle to minimum again. When i move it down motors just stop. No matter where my stick was at the moment.

2. My Hexa is prety horizontal stable in air, but it is rotating clockwise in about 1 turn per second. Which parameter is responsible to this? I'm trying to stop rotation with stick, but no luck. Trims are also not affecting rotation.

I fly only with Stabilize now.

Alex.

Crashpilot1000 November 4, 2012 at 8:09pm

Hi!

I had trouble with the calibration of my self build voltage devider ("Pin2") and the Missionplanner (i think 1.2.14(??) - 1.2.17).

I entered the measured values as always and the MP generates a wacky divider (& voltage). I solved the problem by typing in the values and the divider directly into the MP parameterlist. It's just an inconvenience i didn't have with the older MP versions. So not a problem with the 2.8.1 FW just an MP issue. I also tried - on purpose - to irritate the barocode and i was partly successful :)! I armed the copter in the warm house (20C), ran out in the cold (5C), started the copter without gps fix (blinking) and turned on althold. The copter started to climb ca 1.5m :). I also expected the gyro/acc to dislike the temp. difference but they did well. When arming outside althold works well(even without gps fix). Hihi, at least found something in 2.8.1!! I only managed to do it one time, so i am not shure if it was the temp difference (normally the readout is temp. compensated) or something else - but i will do my best to provoke problems! I also tried to produce the issue of turning out the transmitter after landing with a preprogrammed failsafe in my FrskyRX (modeswitch to RTL, throttlestick to hoverposition, ail/nick to neutral position). As expected the copter wanted to do a RTL at 30m (i set it to 30m to avoid trees). That is not an APM or software issue, because it did what it was supposed to do (of course i held it down by hand).

I imagine this issue can occur when you landed and lift the still powered copter (to unpower it on a table or so without crawling on the floor) with one hand and holding the TX in the other and "pulling some strings" with your jacket. That is described in the wiki "Don't pick up the model and the radio at the same time, you may bump the throttle." So what can be done about it? First of all everybody should be (and probably is) aware of dangers of RC stuff in general. (A careless friend of mine accidently "launched" a 500 Heli in the livingroom with futaba failsave - he jumped out and re-entered when there was no noise anymore..... luckily no one harmed but renovation necessary). Without sonar or contacts in the landing legs or some other kind of sensor it is not so easy for the copter to find out fast: "the throttlestick is down because i have landed and i can disarm now". For the moment i see some possible solutions:

A.: Get used to always disarm your copter immediately after landing (thr dwn, yaw left).

B.: Shorter time till the copter disarms itself after throttle cut. Currently it's about 10 sec. I think 5 sec would do it. I think this parameter is accessible in the MP - parameterlist - sorry haven't searched or wiki-ed for it.

C.: Put a powerswitch for your apm on top of your copter so you can turn off the electronic when bending down. I think this is the worst idea - and another point of a possible failure.

I have another question. There is a discussion currently going on in "my" german forum about gimbal stabilization. I have no experience with gimbals in any way. On the MP i see a lot of gimbal options. The people in the forum want to film a snowboardride with their multicopter. One is piloting and the other one (probably with another transmitter or trainercable) should point the camera to the object. They want stabilization in all 3 axes. Can this be done with the current software? From my understanding using apm2 for flying and camera stuff with 3 axes you would run out of traditional RC - channels and require some dataradio setup (laptop/joystick). Is it possible to setup the apm as gimbal only - or trick it into it by defining it as heli with 90 degree swashplate?

Thank you very much for reading, and sorry for my long post.

So long

Kraut Rob

Mark Slater November 4, 2012 at 4:36pm

Got some more tuning time today, My OCTO lifts at 40% throttle so is slightly overpowered without the camera. After tuning today I've reduced Rate_P to 0.130 rate_i 0.030 and rate_d to 0.004. I've left Imax at default.

At one stage I had sudden spikes in one of the motors, this was when Rate_i was set to 0.05, its gone now and I've got a very flyable machine although it has been a calm day and I've yet to test in wind. Fast climbs are great but the descent is very wobbly almost out of control so I want to increase my Rate_p but I'm afraid this will upset normal flight.

Alexey Kozin November 4, 2012 at 12:25pm

hi

im try to connect allegro acs756 Hall effect current sensor +-100A to apm2.0 after setting amp_per_volt = 40

in mission planner i can see 100А value when real current is 0

this sensor measure both charge and discharge and have zero point at 2,5volt output

how to change arducopter offset for current measurement?

Bill Patterson November 3, 2012 at 9:45pm

Whoo-Hoo! ROI works perfectly! Seems a bit more wobbly in Auto mode though.

https://www.youtube.com/watch?v=eYbbGSA9JIs

Think I ran out of battery at the end. *sigh*

Rob_Lefebvre November 3, 2012 at 8:02am

I just spent 2 battery packs just tuning up the Rate PID's. This is with my DwarfStar, overpowered Octo with SimonK firmware ESC's.

I started with:

Rate_P: 0.110

Rate_I: 0.050

Rate_Imax: 100

Rate_D: 0.002

I was really not happy with this setup. I was fighting a battle where, the Rate P was driving a rate-judder so I had to hold it back, but then it was also unstable in the slightest breeze because it didn't have enough response. Also, with Rate_Imax set at 500 with these params, I had a really bad flip on take-off.

Then I went to:

Rate_P: 0.090

Rate_I: 0.030

Rate_Imax: 100

Rate_D: 0.006

This was much more stable at steady state, but I still wasn't happy with the stability in a little wind. But the larger D-term really seemed to have calmed it down. I reduced Imax to 100 to prevent flip on take-off. But then I also found that it wasn't strong enough to hold well in fast-forward flight. I had to keep pushing a LOT of stick to get it to fly forward.

Now I have:

Rate_P: 0.135

Rate_I: 0.100

Rate_Imax: 500

Rate_D: 0.008

As you can see, I've got Rate P much higher now. The key to all of this, I think, is that D-term. You've got to get it high enough. Now I have no judder, but it's also stable in a breeze. Fast forward flight should also be better but I haven't tested that. And with Rate_Imax at 500, no flip on take-off. I even tried to force the issue by sitting on the ground throttled up with the octo off-level, or pushing the stick over, then jumping into the air. The wound-up I-term causes it to fly off-level a bit for about 1-2 seconds, but then it stops. I think having a high I-max with a low I can cause the flip on takeoff, because they I-term can't wind down fast enough.

But really, the D-term is key to the whole thing. I'll probably try pushing it a little higher.

Guido November 3, 2012 at 4:21am

Hi,

with 2.7.3. APM2 all is working fine, after updating to 2.8.1 all is wrong.. When i fly indoor, my copter goes in any direction, seems that it want to correct and keep the position but it make a spiral that is little and than bigger until i must land. I must always correct with pitch and roll from my transmitter... Try to reset to default parameters but nothing changed.

When outdoor, it correct always the yaw, oscillate from 20° left and right, even here it seems to keep the heading. I redo the log calibration but always with the same result. Could you say me how to do? I think i must upload the 2.7.3

Mario bernard November 1, 2012 at 9:17am

Just my 2 cents. I dont know what esc's you have, but is it possible that you have selected a slow start option on some of them... ?

Tissy October 29, 2012 at 9:29am

Not sure if this is the right place, but when changing modes, all except POSITION HOLD are dispayed in the APM.

When moving to POSITION HOLD, it is displaying as UNKNOWN, is this an error ?

Moderator

Graham Dyer October 29, 2012 at 8:26am

Had a few flights with v2.8.1 this morning but had some strange anomolies again not unlike the "leans" problems of a few months ago. Have sorted my overheating ESC issue as all my ESC's are now out in the breeze under the props.

Basically after taking off and settling into a low hover with a full battery pack, the throttle just faded and my quad pitched up and rolled left resulting in a hard "landing". This happened 3 or 4 times as can be seen in the log, after that the rest of the flight was fine.

Unfortunately the 'motors' and 'raw' were not enabled in the logs but they do show divergent and uncommanded roll and pitch with throttle (me) going to full to try to stop the descent.

Any ideas? Randy?

2012-10-29 16-23 30.log

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ArduCopter 2.8 / 2.8.1 released

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