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Erratic power

Discussion in 'Phantom 2 Vision + Help' started by Farasi, Jun 14, 2015.

  1. Farasi

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    Does anyone know what can cause the up/ down control to operate by its own or which part may need replacing? By this I mean that the motors start as normal but when the UP stick is used the drone takes off and goes to full power without reacting to the down stick. Eventually the down stick kicks in but then it is a mission to try and land in one piece as the power comes and goes very erratically.

    Have been flying for 6 months quite happily when the V2+ started dropping altitude mid way through flights and not immediately responding to UP stick. This caused several hard landings and bounces off the ground. Have checked everything with RC & Vision assistant, re-calibrated everything inc adv IMU but no difference. Daren't fly now until I can make it work properly without the props on.

    Any ideas please?
     
  2. yorlik

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    might you have put in a VERY large gain number on the thrust up/down stick in assitant? maybe just accidentally hit 0 and added x10 gain? this could account for it. otherwise it is broke.
     
  3. Farasi

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    Thanks for your message.

    The GAIN is showing 140% on Vertical which I believe is the factory setting as it has not been altered.

    Sometimes the motors increase/decrease in power without touching the Tx so I am guessing that a circuit board may be bad but not sure if it could be one of the ESC boards or the IMU?

    Something is very broke but not sure what. Any ideas on where or how to start an elimination process?
     
  4. RoyVa

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    If you have eliminated the problem to the stick in the controller then off to eBay and pick up another controller for 50-60 bucks unless you have a means to get a replacment stick and change it out. These things can and do wear out, break or go bad. I bough myself a spare just in case.
    First though I would plug into the assistant under RC and test the stick there. See if your getting erratic operation on the throttle stick. If it runs smooth there you have another issue. If it stick and jumps or lags then the stick is most likely the problem. The quad is like a computer, it can only do what it is told and the controller is the key.
     
  5. Farasi

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    Good thought. I have just checked that and all stick movements are very smooth.
    The problem seems to be in the drone. I did notice that it started to sound rough when flying so I did try different props but no change.
    When powering off, one of the motors stops a little before the other three but I can't see this could cause erratic power fluctuations.
    Could the flight controller fail in this way?
     
  6. yorlik

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    you might try changing firmware; update to newer if possible or drop back one - just to get new firmware loaded - in case the issue is software....
     
  7. Farasi

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    I have just tried this as there was a new version to download. After updating everything I gave the P2V+ a test flight. It took off, still sounding rough and flew backwards without responding to any controls until it hit a tree. A couple of props broke and the gimbal arm slightly bent but otherwise all working as before. When running the motors, without the props on, it increases and decreases speed by itself. This is why I think one of the circuit boards has failed. The response to the controls is now so bad that it has become unusable. Maybe due to the hard landings when learning way back.
    Will now think about what to do. Buy the P3 or a second hand P2V+ and have a lot of spares.........
     
  8. N017RW

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    You really can't evaluate motor RPMs on the ground with no props.
    It's a closed loop system and you have opened the loop sort-of-speak because the output devices (motors/props) are not able to perform their expected tasks.

    Did you perform the suggested IMU and Compass calibrations prior to flight?
     
  9. Farasi

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    Yes, I went through the calibrations.
    The RC and Phantom Assistant show everything looking perfect.
    The problem has got progressively worse over several flights. It started with drifting backwards immediately after take off. Calibrating the IMU did not help even with pieces of paper under the front legs to counteract the drift. After the initial drift backwards it would come under control but then the sudden drop in altitude started followed by the sudden increase in power and intermediate loss of any control.
    The rough sounding motors might be a signal for the answer? If there is one bad motor would the other motors try to compensate and throw everything out of sync?
     
  10. SnoozeDoggyDog

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    I don't suppose you can fly it anymore but I would have liked to know of it was in gps, atti or manual mode and how it reacted in each mode ....

    Phil
     
  11. Farasi

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    Hi Phil

    I was flying in GPS Nazza-M mode when the problems started showing. As the problems got worse I switched back to Vision 2 mode wondering if it would make a difference but sadly not. During one flight in Nazza-M I switched from GPS to Atti to see if I could gain control. It did not help at all. I did not try Manual so cannot comment there. I am happy to test ideas with the props on but not letting it fly until I get a consistent response from the controls while holding the PV2+ down.

    The last flight caused damage that I need to rectify such as a new body shell due to several of the body screw fixings breaking. Also still wondering if the main controller is the culprit but cannot find any information that is telling me that this could cause these problems. Luckily I had a gimbal guard which broke but saved the gimbal. I keep on reading this web site in the hope that I can find out what could cause this power fluctuation and loss of control.
     
  12. IflyinWY

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    What kind of numbers are you getting when connected to the NAZA assistant, or whatever you call it, on the Compass? There should be X Y Z and MOD numbers. What are they?

    Have you opened the bird and inspected, closely inspected each and every component? This would include the GPS assembly and puck.

    Could you have a loose connection, or intermittent connection on a receiver antenna?

    Luckily, you still have your bird and we're here to help. Keep it on a leash if you decide to fly.

    My signature contains a very good Google search engine.
     
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  13. Farasi

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    Thanks for the Google search engine. Lots of interesting reading.
    Here are the numbers attached below.
    I have had a close look at all the connections that are visible. When I get a new body shell I will get a closer look. What do you mean by the puck?
    Now going to keep reading from you links.
     

    Attached Files:

  14. SnoozeDoggyDog

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    Tie the skids down and fly it in manual mode. That way you'll not have any assists enabled that may be trying to correct flight characteristics. See how it throttles up and down etc.

    I really feel for you man. If my bird took a dive id be inconsolable.

    Do you have the link so I can buy a gimble guard please?


    Phil
     
  15. RoyVa

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    You may want to look on eBay. And get you a Laster RPM tach tester. That way at idle and high speed you can test the rpm of the motors. If one is 50 rpm different that any of the others I would replace it and the ESC. Small amount for proper operation. When ever I change a motor I change the controller also. Cheap insurance for about $20.00. Most times it is the ESC that has the problem as the brushless motor only has the bearings that are its moving parts that can go bad. After each flight check the heat of the motors. They may be good and warm but if any are really Hot then they are suspect for replacment. Turn the, by hand a if they fill gritty or loose and different then the others then they are suspects. Touchy feely is a good thing!
     
  16. N017RW

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    You cannot judge motor or ESC health by measuring rotor RPM.

    BLDC motors last hundred of hours with the bearings being the only wearing part(s).

    The system is closed loop and dynamic thus there may never be a case when all props are rotating equally.
    It's an under-actuated system with 6 DOF and [only] 4 control outputs.

    Temperature and rotational friction are your best tools.
     
  17. Farasi

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    I'll give this a go but will have to be tomorrow. Will let you know how it goes.
    The gimbal guard can be bought on ebay at
    http://www.ebay.co.uk/itm/Phondom-I...880?pt=LH_DefaultDomain_0&hash=item43dcddee90
     
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  18. Farasi

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    Glad to hear that you also think the ESC could be the problem. I have put them on the shopping list.
     
  19. Farasi

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    Looks like sound advice. Is there a way of checking the ESC's?
    I will check the motors again tomorrow but I don't recall a hot one. When testing, while holding the drone down, the speed increased by itself it got to the point where the motors seemed to be going too fast and started vibrating before dying down to a tickover, by itself! I will be buying some ESC's but still wondering if the main control unit is the fault.
     
  20. Farasi

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    Couldn't wait for tomorrow so I have just tested the drone now in manual (by changing Failsafe to Manual on assist) while holding it down (just in case). It was a good job because I started the motors with S1 on GPS as soon as I switched S1 down to manual mode the motors increased to high revs without touching the sticks. Switching back to GPS the motors automatically died down to a slow tickover. I then moved the thrust stick up and the motors increased but did not die down when the stick returned to center.
    So manual mode showed me that as soon as the motors start they rev very high without touching the sticks. Any ideas?