Losing MMs and RTH Question...

[Flash Grundelore]

Clarity please....
Am I right in thinking that if I fly out around a landscape feature that is higher than the regular "obstacles" [like behind a steep hill or off around the side of the mountain, as opposed to trees and power-poles/lines] that the Mini will rise to the chosen RTH height, attempt a straight-line return and crash into said landscape feature...?
The down-facing avoidance sensor DOES NOT detect the rising landscape, right?
I know it cannot detect its approach to trees, etc, but I am not sure about the actual terrain.

 

[chriscuk]

I've just tested my mini on my driveway as I've got a grass slope to test with.

I started as low as possible and just used the forwards/back control. I flew at the slope slowly and it climbed to avoid the grass and then when I came back it maintained its new altitude.
It clearly wouldn't jump over my fence and I wasn't willing to test as speed but it will avoid stuff if going slowly enough.

 

[scro]

In my experience the downward sensor (the proximity sensor, rather than VPS) will keep the AC a minimum of 50cm or so above ground (try to grab a hovering AC from underneath and it tends to rise up away from you). @chriscuk's video shows this works when the drone is in motion too, flying towards rising ground. If flying at speed you're likely to get extremely close to the ground while the drone responds to the lower ground-clearance. Whether this happens during RTH I don't know (I suspect it does, though haven't tried) but 50cm is a very low altitude to have the drone fly itself home, given there are no fwd looking OA sensors. It might work OK on very smooth landscape (sand dunes, short grass etc), but anything with long grass, bushes, rocks or similar obstacles that are even close to 50cm or more high will most likely end in the drone joining the scenery.

In short - even if it does work who would be brave enough to rely on it?

 

[chriscuk]

I need to find somewhere to test this properly as I dont fancy crashing into my fence. There is a park near me that has a slope similar or I suppose I could go do it on the road near my house as that goes up hill. If I just give forwards throttle it should climb.... hopefully.

 

[RogerDH]

I need to find somewhere to test this properly as I dont fancy crashing into my fence. There is a park near me that has a slope similar or I suppose I could go do it on the road near my house as that goes up hill. If I just give forwards throttle it should climb.... hopefully.

Your willingness to sacrifice for science is admirable and much appreciated, but might I suggest a few test runs at less than full throttle? ?

 

[scro]

It would be interesting to see what kind of climb rate the AC will do without stick input (other than fwd). I expect it not to be that fast.

 

[Flash Grundelore]

Thanks... I'm trying to pre-think anything I might stupid myself into doing...

scro~ looks like dunes would be the only candidates.

 

[RogerDH]

It would be interesting to see what kind of climb rate the AC will do without stick input (other than fwd). I expect it not to be that fast.

There are a few YouTube videos of it in action, and it looks a bit sluggish when flying over a coffee table for example. It should work fine for typical sloping ground like a hill, but it's not doing any look-ahead to see a sudden rise.

 

[Meta4]

Clarity please....
Am I right in thinking that if I fly out around a landscape feature that is higher than the regular "obstacles" [like behind a steep hill or off around the side of the mountain, as opposed to trees and power-poles/lines] that the Mini will rise to the chosen RTH height, attempt a straight-line return and crash into said landscape feature...?

Your Mini does not have obstacle avoidance sensors.
Yes, it would crash in your hypothetical scenario.
The solution is simple .... Don't go flying behind obstacles.

 

[Thomas B]

Your Mini does not have obstacle avoidance sensors.
Yes, it would crash in your hypothetical scenario.
The solution is simple .... Don't go flying behind obstacles.

Need VLOS anyway.

 

[scro]

Your Mini does not have obstacle avoidance sensors.
Yes, it would crash in your hypothetical scenario.
The solution is simple .... Don't go flying behind obstacles.

Technically the mini does have 1 OA sensor, facing downwards and in very contrived circumstances the drone will make it home without a crash. In reality it would almost definitely crash.

 

[Meta4]

Technically the mini does have 1 OA sensor, facing downwards and in very contrived circumstances the drone will make it home without a crash. In reality it would almost definitely crash.

It has a VPS sensor that doesn't point in the direction that the Mini flies.
Here's how DJI explain the VPS on p15 of the Mini Manual
The Downward Vision System and Infrared Sensing System help the aircraft maintain its current position, hover in place more precisely, and to fly indoors or in other environments where GPS is unavailable.
VPS is not for obstacle avoidance.

 

[scro]

It has a VPS and an infra-red proximity sensor. They each serve a different purpose, with VPS being for holding the drone in place during a hover (agree - this is not OA) and the IR sensor that does function as downwards facing OA sensor and to assist in smoother landing. If an obstacle comes too close to the drone from below then the drone moves up. Bring your hand (the obstacle) up underneath a hovering drone and it will rise up to avoid it. @chriscuk shows this in action in his video.

If the drone is flown behind a gently sloping smooth hill and the RTH initiated with a low RTH height, such that the drone would try to fly "through" the hill the IR sensor will tell the drone that it is getting very close to the ground and it will automatically gain altitude to avoid that obstacle. In reality you'd struggle to find a nice featureless hill like this that the drone would "slide up and over".

Edit: Perhaps I should say "optical flow sensor" rather than "VPS" as VPS could be taken to mean both sensors together.

 

[Ivan_LCF_666]

There are a few YouTube videos of it in action, and it looks a bit sluggish when flying over a coffee table for example. It should work fine for typical sloping ground like a hill, but it's not doing any look-ahead to see a sudden rise.

I wonder if we can use some type of a mirror or a reflector to redirect the sensors sensing ability to be forward instead of down!? That would be awesome, I will actually try that with mine, little mirrors I'll stick on the bottom of my Mini at a 45 degree angle as to get a reflection from what's in front the Mavic Mini.

I'll let you all know what happened, but in theory when it sees something in front of it, it will just rise up before it gets over it.

PS: I hope I don't crash my beloved baby Mavic Mini drone!!!

 

[scro]

@Ivan_LCF_666 It might work, but don't try that inside up against a wall ? as that may enable AHC mode (autmoatically hit ceiling). Cover up the VPS optical flow sensor too, as things might get really interesting otherwise!

 

[TDZHDTV]

I need to find somewhere to test this properly as I dont fancy crashing into my fence. There is a park near me that has a slope similar or I suppose I could go do it on the road near my house as that goes up hill. If I just give forwards throttle it should climb.... hopefully.

I tried this some time ago, slight incline resulted in a noise dive at speed,

 

[new2mavic]

Bigger drones such as the M2P has a terrain follow mode that can do what the OP wants. The Mini probably has the required hardware capability ( IR and vision are there but not ultrasonic ) but for marketing reasons they don't provide such feature in the firmware.

 

[Ivan_LCF_666]

@Ivan_LCF_666 It might work, but don't try that inside up against a wall ? as that may enable AHC mode (automatically hit ceiling). Cover up the VPS sensor too, as things might get really interesting otherwise!

Yeah I was thinking that I have to most definitely cover the VPS sensor, I'll fly in ATTI mode if that's what it switches to as I have such experience from flying my 3D helicopters.

About the other sensor which I'll be redirecting I was thinking can't it be used for both down and in front at the same time?! Like the lil mirror would only be half way through the sensor and the sensor will be able to get a reflection from the front and from down as half of it will be unobstructed by the mirror, the other half will get the front reflection. It might take a lot of trial and error to get it right, but that would be cool, the lil Mavic would be able to fly over fences and similar things.

 

[new2mavic]

Yeah I was thinking that I have to most definitely cover the VPS sensor, I'll fly in ATTI mode if that's what it switches to as I have such experience from flying my 3D helicopters.

About the other sensor which I'll be redirecting I was thinking can't it be used for both down and in front at the same time?! Like the lil mirror would only be half way through the sensor and the sensor will be able to get a reflection from the front and from down as half of it will be unobstructed by the mirror, the other half will get the front reflection. It might take a lot of trial and error to get it right, but that would be cool, the lil Mavic would be able to fly over fences and similar things.

The VPS is design to keep the Mini about 30 ~ 50 cm off the ground. If a mirror is added in the described manner. It will go up automatically if the fence is within may be 15 ~ 35 cm from the front propeller. However, what will stop the drone from continuing to fly forward and hit the fence ? Considering the short distance, it will just take a fraction of a second for collision to occur.

 

[rodolpholemos]

Clarity please....
Am I right in thinking that if I fly out around a landscape feature that is higher than the regular "obstacles" [like behind a steep hill or off around the side of the mountain, as opposed to trees and power-poles/lines] that the Mini will rise to the chosen RTH height, attempt a straight-line return and crash into said landscape feature...?
The down-facing avoidance sensor DOES NOT detect the rising landscape, right?
I know it cannot detect its approach to trees, etc, but I am not sure about the actual terrain.

The best you can do is to adjust your RTH altitude properly according to the highest obstacle of the surrounding area where you’ll be flying. I always check the RTH altitude before flying because I’m always afraid of it has been reset by a firmware update, for example.