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Performance issues with Virtual Sticks and Mavic Mini
593 3 2020-8-13
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DJI_Lisa
Second Officer
South Africa
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We can learn a lot from each other and so far,  Dronelink has proven to be a great resource around Virtual Sticks and automated mission planning with Mavic Mini's (and other drones).  So I'd like to highlight an issue some pilots have been experiencing when flying with Virtual Sticks and the Mavic Mini.  Please note, that this is more of a hardware technical article but can really benefit other developers out there who are using DJI's SDK and targeting DJI's smaller drones.

Some pilots using Dronelink's app and what any developers using virtual sticks will most likely encounter with the Mavic Mini, is that executing a mission can be jerky.  This of course, is not ideal and so I'd like to share some of Dronelinks explainations around this and their tips and tricks.





The following is taken from Dronelink Article: Why does the drone fly off course or make jerky movements during certain mission plans?  

Flight performance depends on many factors including:

  • Hardware - How big and stable is the drone?
  • Environment - What are the winds aloft, etc?
  • Mobile device performance - Are you using an older device? Does it have low battery? Is the ambient temperature high or are you in direct sunlight?
  • Mission Plan - What are the specifics of your mission plan? How fast and how tight are the curves?

If you use a small drone in high wind with a low performance device that is low on battery and in direct sunlight on a hot day, you cannot expect the same performance as a large drone on a calm day with a brand new iPad Pro in 70 degree weather.

When in doubt, try to mitigate as many of these factors as you can, the easiest of which are the flight path and speed (round out the corners and slow it down). In the end there is a 200ms round-trip latency with virtual stick (learn more), meaning onboard code will always have an advantage with respect to smoothness, but we have been able to achieve great results with many different drones and devices in a variety of conditions.






Working with Virtual Sticks and the Mavic Mini is a work in progress, is not perfect and over time will benefit from tweaking here and there.  If anyone has any other tips and tricks, questions or points - please do share with us!



And thank you Jim McAndrew for the benefit of your experience so far and letting me share this on DJI's Developer Forum




2020-8-13
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Leandro31
lvl.4
Flight distance : 371280 ft
Uruguay
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Is there any way to measure the signal delay? As we don't have anything like a ping command on the sdk, can we just measeure the response time from some param query?
2020-8-14
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Mats Bohlinsson
lvl.4

Sweden
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Leandro31 Posted at 2020-8-14 05:57
Is there any way to measure the signal delay? As we don't have anything like a ping command on the sdk, can we just measeure the response time from some param query?

This info is not what I have experienced.

Latency: No way 200ms, more like 20ms. Itäs exctly the same latency you get from the stick in the RC. It's in the same way.

The jerkiness is due to which mode the gimbal is in.
Sadly the virtualstick biggest flaw is that the gimbal is always in yaw follow mode. The yaw follow mode and turning gets into a race condition. It's like this on all mavics I tried, but since the mini is so light the yaw changes a lot more.


This gets even worse if the program uses the drones reported heading for calculating the gimbal yaw, specially when its windy, cause the yaw of the drone is alterating. The solution is to use the yaw that is set in virtualstick as a reference when calculating the gimbal yaw, or use the speed option, it's not perfect byt it gets better.

The solution is to set the gimbal to FREE mode, and everything gets superstable.
But there is no such option in the sdk, at least not to my knowledge. At least I havn't got it to work.
https://developer.dji.com/api-re ... bal_workmode_inline


DJI could you please fix this?. It would make all flights so much smoother in virtualstick.
2-13 16:33
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kv886
Second Officer

South Africa
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I think you can send an email to dev@dji.com to report this problem
2-18 01:39
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