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Landing Manually (Properly)

I was going to post about landings then found this thread, which I have now read.
Catching landing - if I move my hand under the drone it rears upwards and I find it hard to "catch". I'll try the "sliding fingers under" in a minute!

I wanted to practice landing on a pad using the camera, not visually, but the camera goes back to horizontal once the drone reaches 0.5m!! Very annoying as I lose the target.

Just been outside and tried the "sliding fingers under" and NO, it doesn't disable the sensors! As soon as you get to them the drone leaps upwards!! However, did several catches by holding the controller/left stick in my left hand, pulling down on stick and it did eventually "land" into my hand but had to manoeuvre hand to make sure it stayed in the right place as the drone automatically "landed". Not comfortable with that but OK in a no clear landing area.
 
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I was going to post about landings then found this thread, which I have now read.
Catching landing - if I move my hand under the drone it rears upwards and I find it hard to "catch". I'll try the "sliding fingers under" in a minute!

I wanted to practice landing on a pad using the camera, not visually, but the camera goes back to horizontal once the drone reaches 0.5m!! Very annoying as I lose the target.

Just been outside and tried the "sliding fingers under" and NO, it doesn't disable the sensors! As soon as you get to them the drone leaps upwards!! However, did several catches by holding the controller/left stick in my left hand, pulling down on stick and it did eventually "land" into my hand but had to manoeuvre hand to make sure it stayed in the right place as the drone automatically "landed". Not comfortable with that but OK in a no clear landing area.
Pulling down the left stick is the correct way. I found that using a landyard in your RC helps a lot for doing one hand maneuvers.
 
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Sometimes, when travelling you have to improvise. This week's find in France, a manhole cover sticking out of a melted piste, presumably horizontally level (so long as I didn't go too close to the adjacent rock)PXL_20220412_090140569.jpg
And on snow I've been launching from an upturned snowboard. The trouble is, it's narrow and waxed :p
 
Sometimes, when travelling you have to improvise. This week's find in France, a manhole cover sticking out of a melted piste, presumably horizontally level (so long as I didn't go too close to the adjacent rock)View attachment 146680
And on snow I've been launching from an upturned snowboard. The trouble is, it's narrow and waxed :p

That's almost certainly cast iron. I'd suggest checking the drone's compass accuracy before beginning your flight. That much ferrous material could cause the compass to be inaccurate and lead to extremely erratic flight.
 
Sometimes, when travelling you have to improvise. This week's find in France, a manhole cover sticking out of a melted piste, presumably horizontally level (so long as I didn't go too close to the adjacent rock)View attachment 146680
And on snow I've been launching from an upturned snowboard. The trouble is, it's narrow and waxed :p
Launching from metal will mess up the compass.
 
Interesting, thanks for that. Probably explains the IMU calibration errors in pre-flight? They cleared before I took off. I calibrated the compass as well
 
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Interesting, thanks for that. Probably explains the IMU calibration errors in pre-flight? They cleared before I took off. I calibrated the compass as well
A bit OT ... but lining below up so you know why not to use manhole covers as take-off platforms in the future ...

It's a couple of functions & errors you need to know about & understand in order to avoid disasters ...

The 4 thing's are ...

-IMU initialization
-Yaw error
-Compass calibration
-IMU calibration

IMU initialization:
Initially when the drone is powered up the IMU doesn't know into which direction your drone points. During the power up sequence the compass will tell the IMU the cardinal directions, this lets the IMU "initialize" ... get to know into which direction your drone points. After this initialization phase the IMU takes over from the compass & will be the number one provider about the drone direction (by means of the gyro) to the flight controller.

If something goes wrong during this initialization phase, perhaps due to that you have placed the drone near some ferromagnetic material which deflects the compass ... the IMU will get false information about the cardinal directions.

This will lead to a ...

Yaw error:
It's of utmost importance that the drone knows in which direction it points when it is airborne. If the drone for instance is pointing to north in a hover & the flight controller gets information from the GPS that the drone have started to drift south (due to wind) the flight controller will commands both rear motors to spin up, leading to that the drone pitches down ... this to regain the position & resist the wind.

Imagine now that the drone in reality actually isn't pointing to north, instead south (the IMU think's north but in reality south... this due to a failed IMU initialization). In this case & with the same scenario with the drone drifting in a hover to south the flight controller do as earlier, it commands both rear motors to spin up (as it think's the drone is pointing north), leading to that the drone pitches down ... but here with a drone actually pointing to south the drone doesn't regain the position, the positional error actually gets even larger ... & the flight controller repeats the same command ... and again & again .... and this leads to a real uncontrollable fly away in high speed into a southerly direction.

The cause for this fly away is a yaw error ... meaning a IMU that doesn't have correct info about into which direction the drone points.

It's a way to check the IMU initialization pre flight ... & prevent a following yaw error:

After the drone have been powered on & the live view have turned up in the app ... always, on the map, check so the triangular drone icon there is pointing equal to objects on the map (roads, buildings) as the drone does in reality. If it does the initialization of the IMU have been successful ... if not, power down the drone, move away to another location & power up again & repeat the map check.

Compass calibration:
The compass in the drone is mainly affected by 2 mag. fields ... the interesting one, earth ... & the field coming from the internal/external components of the drone.

In order to only measure earth mag. field, the drones own mag. field have to be measured so it can be deducted from the total mag. field that affects the compass ... that is done during a compass calibration. When the calibration is done the compass info passed over to the IMU only shows the earth mag.field.

So a compass calibration is only necessary if the mag. field from the drone itself have been changed ... either by attaching or taking off extra equipment. A calibration will never correct a wrongly initialized IMU & therefore it will never prevent a yaw error.

IMU calibration:
The IMU contain a lot of sensors ... the obvious ones is the accelerometer & the gyro. These sensors need sometimes a calibration to give the correct measurements. For instance ... if the gyro is measuring that the drone is leveled, but it isn't in reality, the drone will erratically drift back & forth. Here a IMU calibration is needed ... if all is good the drones attitude will be correctly measured by the gyro & the drone will hover rock solid without more drifts than the accuracy of the GPS.

So a IMU calibration is only needed when the drone shows these erratic drifts.
 
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A bit OT ... but lining below up so you know why not to use manhole covers as take-off platforms in the future ...

It's a couple of functions & errors you need to know about & understand in order to avoid disasters ...

The 4 thing's are ...

-IMU initialization
-Yaw error
-Compass calibration
-IMU calibration

IMU initialization:
Initially when the drone is powered up the IMU doesn't know into which direction your drone points. During the power up sequence the compass will tell the IMU the cardinal directions, this lets the IMU "initialize" ... get to know into which direction your drone points. After this initialization phase the IMU takes over from the compass & will be the number one provider about the drone direction (by means of the gyro) to the flight controller.

If something goes wrong during this initialization phase, perhaps due to that you have placed the drone near some ferromagnetic material which deflects the compass ... the IMU will get false information about the cardinal directions.

This will lead to a ...

Yaw error:
It's of utmost importance that the drone knows in which direction it points when it is airborne. If the drone for instance is pointing to north in a hover & the flight controller gets information from the GPS that the drone have started to drift south (due to wind) the flight controller will commands both rear motors to spin up, leading to that the drone pitches down ... this to regain the position & resist the wind.

Imagine now that the drone in reality actually isn't pointing to north, instead south (the IMU think's north but in reality south... this due to a failed IMU initialization). In this case & with the same scenario with the drone drifting in a hover to south the flight controller do as earlier, it commands both rear motors to spin up (as it think's the drone is pointing north), leading to that the drone pitches down ... but here with a drone actually pointing to south the drone doesn't regain the position, the positional error actually gets even larger ... & the flight controller repeats the same command ... and again & again .... and this leads to a real uncontrollable fly away in high speed into a southerly direction.

The cause for this fly away is a yaw error ... meaning a IMU that doesn't have correct info about into which direction the drone points.

It's a way to check the IMU initialization pre flight ... & prevent a following yaw error:

After the drone have been powered on & the live view have turned up in the app ... always, on the map, check so the triangular drone icon there is pointing equal to objects on the map (roads, buildings) as the drone does in reality. If it does the initialization of the IMU have been successful ... if not, power down the drone, move away to another location & power up again & repeat the map check.

Compass calibration:
The compass in the drone is mainly affected by 2 mag. fields ... the interesting one, earth ... & the field coming from the internal/external components of the drone.

In order to only measure earth mag. field, the drones own mag. field have to be measured so it can be deducted from the total mag. field that affects the compass ... that is done during a compass calibration. When the calibration is done the compass info passed over to the IMU only shows the earth mag.field.

So a compass calibration is only necessary if the mag. field from the drone itself have been changed ... either by attaching or taking off extra equipment. A calibration will never correct a wrongly initialized IMU & therefore it will never prevent a yaw error.

IMU calibration:
The IMU contain a lot of sensors ... the obvious ones is the accelerometer & the gyro. These sensors need sometimes a calibration to give the correct measurements. For instance ... if the gyro is measuring that the drone is leveled, but it isn't in reality, the drone will erratically drift back & forth. Here a IMU calibration is needed ... if all is good the drones attitude will be correctly measured by the gyro & the drone will hover rock solid without more drifts than the accuracy of the GPS.

So a IMU calibration is only needed when the drone shows these erratic drifts.
That's great, thanks for taking the time to write it up. I didn't experience any problems in flight, but perhaps luck on this occasion
 
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