I have a newer 3dr iris+ and recently had a flight where the Mission stated an altitude of 200meters. It flew most of the way at the correct altitude, but towards the end it started to get low, to around 50 meters. I was watching and I switched it into loiter mode and put the throttle high up and it had no problem gaining altitude.The battery voltage was fine as well, as it was a short mission.What could cause this? I was using the droidplanner2 android software....I can provide logs if needed....Thanks in advance for your help!
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That shouldn't matter. I bought a Tarot gimbal separately as well for my 3DR Y6B, the only thing you get when you buy it from 3DR is an assembled unit and a $10 mounting plate.
Did 3DR give any indication that a different motor/prop combination might be necessary for use with a gimbal/GoPro?
That came stock with the Iris+ right? So in other words it was intended to be flown with the Tarot gimbal and a GoPro as shipped, so it should be capable of producing more than adequate amount if thrust.
I'm not 100% convinced I'm interpreting your log correctly, so I hope someone like Randy or Bill will take a look and teach us both a bit about interpreting the data. That said I still think you're not developing enough thrust. However this appears to be contradicted in at least one of the charts that will follow, Thus the reason I hope someone else will take a look.
First lets take a look at the Auto Analysis done with Mission Planner.
Log File C:/Users/Nathaniel Caner/AppData/Local/Temp/tmp3012.tmp.log Size (kb) 11365.4287109375 No of lines 152205 Duration 0:10:32 Vehicletype ArduCopter Firmware Version V3.2 Firmware Hash c8e0f3e1 Hardware Type Free Mem 0 Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data Test: Balance/Twist = GOOD - Test: Brownout = GOOD - Test: Compass = GOOD - mag_field interference within limits (21.35%) Max mag field length (578.82) > recommended (550.00)
Test: Dupe Log Data = GOOD - Test: Empty = GOOD - Test: Event/Failsafe = GOOD - Test: GPS = GOOD - Test: IMU Mismatch = GOOD - (Mismatch: 0.19, WARN: 0.75, FAIL: 1.50) Test: Parameters = GOOD - Test: PM = GOOD - Test: Pitch/Roll = FAIL - Pitch (-44.37, line 31438) > maximum lean angle (30.00) Test: Thrust = FAIL - Avg climb rate -13.88 cm/s for throttle avg 979 Test: VCC = GOOD -
Everything looks good, really good in fact except the THRUST test. I don't know what the metric is here but I think it its supposed to be over 15cm/sec. In your case its below that and the throttle is almost maxed out ti produce this rather lethargic number.
Next lets take a look at Voltage vs Altitude:
Your Mission had all waypoints at 200m, we can clearly see that over the first 2 minutes you climb to 200m and the voltage takes the biggest hit during this time dropping from a high of 12.41v down to 11.18v. Your OK for about a minute then it starts to have trouble maintaining 200m fluctuating in altitude over the next two minutes until finally taking a dramatic plunge to a low of about 30m where you change to loiter and are able to climb a bit back up to around 90/95m, the voltage meanwhile has continued to drop now to 10.65v. Your voltage was around 11.3v when you began to have trouble holding 200m so you dropped another 0.65v.
Lets take a look at Current vs Altitude:
During your climb to 200m your peak current is about 30A. Once you reach 200m it drops to about 15A, then over the next 2 minutes fluctuates between a high of about 30A and a low of around 7A. During the plunge its fairly stable at around 23A.
Now lets take a look at what your motors are doing:
This is a snipet from the beginning of the plunge to where you change over to loiter. Motors 1,2 and 3 appear to be operating normally but motor 4 is maxed out at around 1.946ms while the other motors range between 1.6ms to 1.85ms. I would imaging this could result in an unstable attitude that might cause a loss of control/altitude.
Lastly lets take a look at Desired Altitude/Altitude/Barometric Altitude:
This is where I begin to get confused. From pulling your waypoints out of your tlog I can see that the altitude for all waypoints in the mission is 200m, so I expected to see the DAlt to remain at 200m, but it doesn't it closely follows AltR and BarAlt R. I might not understand these values correctly, but I believe DAlt is desired Altitude, Alt R is GPS altitude and BarAlt R is Barometric Altitude.
What I expected to see was that DAlt remained at 200m while Alt R and BarAlt R would follow each other closely while diverging from DAlt. It appears that the FC is responding to a change in DAlt and reducing altitude accordingly. This is obviously not what you wanted.
Hopefully someone else can interpret these charts and explain things for us better. At this point I'm not sure what's going on, but I do believe that thrust is marginal.
Have you added anything to the stock Iris+ that would have added any significant weight?
Regards,
Nathaniel ~KD2DEY
Stuart Brookes > Nathaniel CanerDecember 28, 2014 at 2:36pm
I think I saw one of the experts post recently sating dalt drops if altitude can not be maintained . hopefully that will be confirmed by one of the experts.
Certainly higher C values won't hurt, however at the current level the Iris+ is running 8C is more than what is required. The higher the C rating the heavier the battery for a given capacity, which equates to shorter flying time.
I'll take a look at the bin file shortly and see what I can see.
Regards,
Nathaniel ~KD2DEY
Stuart Brookes > Nathaniel CanerDecember 28, 2014 at 1:51pm
Looks under powered to me judging by that bin file. The ThrOut is pinned at full for that whole descent stage. Battery is lowish, but doesn't seem alarmingly so to me. maybe slow it down using the appropriate speed parameter in mission, or limit the pitch angle (It didn't pitch as far as the demanded pitch angle during that descent).
Can you pull the log file from the Pixhawk SD card, it has more detail and could help? Measuring internal resistance is easy with a 3cell battery. Take a 12v 100w 2 prong halogen bulb (available at Lowes/Home Depot) and make a simple rig with a connector that can attach to your battery with an appropriate connector. Using a Current/voltage analyzer like this one, measure the no load voltage. Then plug in the 12v 100 watt bulb and wait 10 seconds. Note the voltage and current again. Unplug the battery. Then it's just a matter of doing a bit of simple math.
((No Load Voltage - Loaded Voltage) * 1000) / Amps Under Load= Internal resistance in millliohms
This is really a comparison test in which you would ideally test the battery when new and compare to subsequent tests at a later date. In general terms the lower the value the better. Anything under 30 milliohms should be good. Over 50 and I doubt you'd have good results.
Thanks for the quick replies. Greatly appreciated. I had thought that the 400 foot ceiling was for commercial purposes and not a strict limit for noncommercial personal flights....
Attached are the telemetry logs from my android device.
Replies
Adam,
That shouldn't matter. I bought a Tarot gimbal separately as well for my 3DR Y6B, the only thing you get when you buy it from 3DR is an assembled unit and a $10 mounting plate.
Did 3DR give any indication that a different motor/prop combination might be necessary for use with a gimbal/GoPro?
Regards,
Nathaniel ~KD2DEY
Adam,
That came stock with the Iris+ right? So in other words it was intended to be flown with the Tarot gimbal and a GoPro as shipped, so it should be capable of producing more than adequate amount if thrust.
Regards,
Nathaniel ~KD2DEY
Adam,
I'm not 100% convinced I'm interpreting your log correctly, so I hope someone like Randy or Bill will take a look and teach us both a bit about interpreting the data. That said I still think you're not developing enough thrust. However this appears to be contradicted in at least one of the charts that will follow, Thus the reason I hope someone else will take a look.
First lets take a look at the Auto Analysis done with Mission Planner.
Log File C:/Users/Nathaniel Caner/AppData/Local/Temp/tmp3012.tmp.log
Size (kb) 11365.4287109375
No of lines 152205
Duration 0:10:32
Vehicletype ArduCopter
Firmware Version V3.2
Firmware Hash c8e0f3e1
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Balance/Twist = GOOD -
Test: Brownout = GOOD -
Test: Compass = GOOD - mag_field interference within limits (21.35%)
Max mag field length (578.82) > recommended (550.00)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.19, WARN: 0.75, FAIL: 1.50)
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = FAIL - Pitch (-44.37, line 31438) > maximum lean angle (30.00)
Test: Thrust = FAIL - Avg climb rate -13.88 cm/s for throttle avg 979
Test: VCC = GOOD -
Everything looks good, really good in fact except the THRUST test. I don't know what the metric is here but I think it its supposed to be over 15cm/sec. In your case its below that and the throttle is almost maxed out ti produce this rather lethargic number.
Next lets take a look at Voltage vs Altitude:
Lets take a look at Current vs Altitude:
Now lets take a look at what your motors are doing:
Lastly lets take a look at Desired Altitude/Altitude/Barometric Altitude:
What I expected to see was that DAlt remained at 200m while Alt R and BarAlt R would follow each other closely while diverging from DAlt. It appears that the FC is responding to a change in DAlt and reducing altitude accordingly. This is obviously not what you wanted.
Hopefully someone else can interpret these charts and explain things for us better. At this point I'm not sure what's going on, but I do believe that thrust is marginal.
Have you added anything to the stock Iris+ that would have added any significant weight?
Regards,
Nathaniel ~KD2DEY
Stuart,
That would make sense then if you aren't producing enough thrust.
Regards,
Nathaniel ~KD2DEY
Adam,
Certainly higher C values won't hurt, however at the current level the Iris+ is running 8C is more than what is required. The higher the C rating the heavier the battery for a given capacity, which equates to shorter flying time.
I'll take a look at the bin file shortly and see what I can see.
Regards,
Nathaniel ~KD2DEY
Looks under powered to me judging by that bin file. The ThrOut is pinned at full for that whole descent stage. Battery is lowish, but doesn't seem alarmingly so to me. maybe slow it down using the appropriate speed parameter in mission, or limit the pitch angle (It didn't pitch as far as the demanded pitch angle during that descent).
Stu
Adam,
Can you pull the log file from the Pixhawk SD card, it has more detail and could help? Measuring internal resistance is easy with a 3cell battery. Take a 12v 100w 2 prong halogen bulb (available at Lowes/Home Depot) and make a simple rig with a connector that can attach to your battery with an appropriate connector. Using a Current/voltage analyzer like this one, measure the no load voltage. Then plug in the 12v 100 watt bulb and wait 10 seconds. Note the voltage and current again. Unplug the battery. Then it's just a matter of doing a bit of simple math.
((No Load Voltage - Loaded Voltage) * 1000) / Amps Under Load= Internal resistance in millliohms
This is really a comparison test in which you would ideally test the battery when new and compare to subsequent tests at a later date. In general terms the lower the value the better. Anything under 30 milliohms should be good. Over 50 and I doubt you'd have good results.
Regards,
Nathaniel ~KD2DEY
Thanks for the quick replies. Greatly appreciated. I had thought that the 400 foot ceiling was for commercial purposes and not a strict limit for noncommercial personal flights....
Attached are the telemetry logs from my android device.
Let me know if that helps.
2014-12-26 13-25-02.tlog
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