APM wobble in the wind.

[Vermiform]

I am using a micro-apm FC on my S500 quad. Today while filming in 10-ish mph winds while in Position Hold my quad did some jerky wobbles at around 100 feet. It did it during a gust and it kind of felt like a mini VRS, but I was not descending. It was in Position Hold (a GPS Loiter mode) and I'm thinking it was attempting to maintain its position. Could this be indicative of the PIDS set too rigid or something?

It has done this once before and the only similar factor was steady wind. It never does it in Stabilize mode, only when it is trying to maintain its own position.

 

[Old Man]

Unless the response was extremely severe it's probably just fine. Being familiar with APM and Pixhawk flight modes, and aviation weather, I suspect the MR was simply dealing with a directional and velocity shift in winds that normally occurs at various elevations above the ground. Winds at altitude are rarely, in ever, what is experienced at the ground. Often there's a small wind shear caused by the frictional effects of wind encountering the ground, which causes a change in wind direction between ground level and aloft. Wind velocity above the ground is usually greater than at the ground. What you are experiencing for wind typically is not what the aircraft is experiencing if is at an elevation significantly higher than your head. You also have something few realize in play, a small drift in GPS position over time. It sounds like APM was doing exactly what it's supposed to do, and that's hold the aircraft in a position.

 

[Vermiform]

Unless the response was extremely severe it's probably just fine.

It is pretty extreme. Imagine yanking back on forth 2 or 3 times on your aileron stick as fast as you can with no expo in it. It is extreme enough to make me pucker.

I know what you mean about wind velocity being higher and different at higher altitudes. I learned that lesson the hard way with my first quad (180 qx).

 

[Old Man]

Do you have a geo fence altitude set that you've forgotten about? That's how one of mine acts when it bumps the fence.

 

[Vermiform]

Not unless there is a default one already set. I haven't studied up on how to set fences yet so I haven't set any unless by accident.

 

[Old Man]

Look through all the reference material you have about failsafes. You may have a default altitude failsafe in the form of a geo fence.

 

[Vermiform]

Will do. I need to learn about fences eventually.

Hey, while I have an APM/Pixbrain expert handy......do you know of any way to set waypoints while in flight? Like the new DJI Inspire software will do. You put the bird in a certain spot, click set waypoint, then put it in another spot and click set waypoint again....etc.

 

[Old Man]

I do not. That's usually done during the ground prep and planning. I believe you can relocate a previously established waypoint but don't know about adding one.

 

[Vermiform]

Seems like a very handy tool on the inspire. You take it to where you want to start the shot, set waypoint, then take it to the end and set waypoint. Bring it back, hit go and concentrate on gimbal operation. Hopefully it will be added as a feature with us soon.

 

[Old Man]

But you're still left with the issue of wondering if your aircraft is coming back to you or heading off into the sunset.

 

[Vermiform]

Actually that's an unlisted feature. Occasionally they fly back to China for FW upgrade and tweaking!

 

[violetwolf]

If you have a tablet or laptop you can set waypoints through mavlink using mission planner or Droidplanner etc.

I have a 7" tablet that I can attach to my TX handle, but I've never got around to using it. The problem is that flight Controllers fly pretty twitchy and jerky compared to humans, so autopilot for filming is less desirable than human piloting.

 

[Vermiform]

If you have a tablet or laptop you can set waypoints through mavlink using mission planner or Droidplanner etc.

I have a 7" tablet that I can attach to my TX handle, but I've never got around to using it. The problem is that flight Controllers fly pretty twitchy and jerky compared to humans, so autopilot for filming is less desirable than human piloting.

But using it as a cable cam shouldn't be jerky at all. I use mavlink to set waypoints and such but being able to place the bird where you want it and set that exact waypoint would be a huge time saver.

Imagine you get to a new shoot. You figure out how you want to do a shot, fly the bird to exactly where you want it to start then to the end point, then replay it and concentrate only on the shot.

 

[violetwolf]

As it trundles jerking about along it's "cable"

An easy test to check this out for yourself: Hover your multi in front of you in AltHold mode. Observe it's behavior. Then switch to Loiter mode. It will almost certainly start twitching about while it corrects for position.

All FC's are like this at present.

The reason for this is that it's a fixed loop in the FC: It corrects, then looks at the sensor data, compares, and then corrects again.. over and over. Humans don't behave this way. You could say well I'll soften the gains which may help to a minor degree but the loop still exists and so will the jerky behavior, just slower.

There's a reason why all big players in this game are two man teams, and the pilots are precision flyers. Don't get me wrong, it IS doable, but you can't be a pro and rely on it. Everything changes as the day progresses. ...the wind changes to cross breeze, Or the light changes and the director wants to start at a different angle (this never happens right?) The ability to hit your mark is just as important in the air as it is on the ground. The ability to change at a moments notice without holding up the set while playing with the waypoints is important.

 

[Vermiform]

I've never filmed while running a WP mission, but as it moved from point A to point B it looked pretty smooth. I'll do some tests and report back.

 

[dazzab]

Will do. I need to learn about fences eventually.

Hey, while I have an APM/Pixbrain expert handy......do you know of any way to set waypoints while in flight? Like the new DJI Inspire software will do. You put the bird in a certain spot, click set waypoint, then put it in another spot and click set waypoint again....etc.

You can click on the map and select 'fly here' at any point which is similar to what you are asking. That's essentially how the 'Follow Me' mode works. It constantly updates the 'fly here' as you move the reference GPS around. I think you can upload a mission while it's in the air. They don't activate until you put it in 'Auto' mode.

 

[violetwolf]

I'm thinking dazzab is right about uploading missions in the air. I had originally planned to use it as described by OP but have just been doing manual. This thread has rekindled my desire to try this though

 

[Vermiform]

You can click on the map and select 'fly here' at any point which is similar to what you are asking. That's essentially how the 'Follow Me' mode works. It constantly updates the 'fly here' as you move the reference GPS around. I think you can upload a mission while it's in the air. They don't activate until you put it in 'Auto' mode.

So then it flies to that point at the same altitude it is already at?