Hello,

right now I'm doing some testing regarding to ros-sdk-based indoor flights. Therefore I'm using the M600 Pro in a flight cage and tracked by a vicon system (Motion Capture). So I can gather quite precise values for height/position/movement.  

My goal is to fly the drone safe in an indoor area (without gps) with additional sensors for navigation(cameras, lidars, ultrasonic, ...).

Please correct me if I'm wrong, but it seems right now there is no possibility to feed any kind of external data to the flight computer of the drone?!

Below some examples:  

1) Altitude

The barometer measurements are terrible in an indoor location. Walls and bigger objects manipulate the airflow terrible and to use the current measurements for the topic /dji_sdk/flight_control_setpoint_generic to set the z-value to an explicit height results in non stationary height changes. Especially while moving I registered height changes of around 40cm which is quite dangerous.

I looked up in the dji A3 specsheet and read the barometer is built-in in the IMUs so I guess there is no possibility in exchanging the sensors (or are there sensors-adapters to connect custom/indiviual sensor to the dji A3?)

Even if I calculate my a fused-sensor-value as long as I set an explicit z-value as my control command – the drone will always navigate based on its own height measurements.

2) Velocities

The velocities seem to be similar. For the drone it would always been determined by gps-values – but I'm indoor and gps won't work. First I thought about systems like guidance which is acordingly to the german website compatible with all matrice drones. But now I know its not (so the guidance feels quite useless). All I can do is gain additional (external) sensor data but I can't let the drone know about them.  

(Also the quality of the single cameras is not so great and dji discontinued their sdk-support).

So I guess I need to go for specific thrust values as control command and ditch the velocity control for now.

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So in short I want to ask these questions:

- Does anybody know about possibilities to change the drone sensors? Like barometer and gps because I will not use them, and they might result in more errors than benefits…

OR atleast connect some additional sensor information to the flight controler.

- Can anyone help me with setting correct thrust-values for z-positioning?

Some values for Take-Off and Hoover would be great even if its not for a M600. Also I would like to know about your experiences with thrust-control (simulation vs. reality).

OK, hopefully somebody will read all this and can help me out.

So I want to share some updates - even though my original questions are not really solved.



In the graphic you can see some measurements of simulated height-thrust-relations. I ran the simulation for the normal takeoff command - afterwards I set my thrust to 29.20105 which is my best attempt in a stationary hover (have in mind that this value will not hover the drone even in simulation it is slightly descending) and after 5 seconds I increased my thrust by 0.1 for 5 seconds and then decreased the thrust by 0.2 and increased it after 5 more seconds to its original value. So if you are interested here is some kind of a step/pule behaviour of the M600pro. Looks a bit to well, so I guess the real behavior would be diffrent.
Some real test showed the problem of the drone ascending bevor you reached your hover-thrust-value - so if you ever intend on evaluating a precise thrust value to hover for your real drone.
First start in altitude mode ascend to about 1 meter and then switch to exampe p-mode and set there via sdk a test value for your thrust.
Afterwards hope the best: your drone will ascend or descend depending an your value (my experiments showed the correct value would be close to the simulated)
But I just can recommedn to get some kind of additonal controller or you will crash your drone ... I'm waiting for spare parts right now - so yeah didn't worked so well.
Now i tried to design a functional controller (based on simulated measurments) but sadly no real progress. Need to do more about it.

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So about my original questions:

Can anybody provide some information about the barometer/IMU issue?

Especially @dji staff: can you tell us something about the sensor are designed and how to open them? To replace the barometer with some more precise altitude measurements would be crucial for me.

Then I could just replace the sensor for something more precise and the internal dji-flight_controler would also work indoors.



Right now I'm thinking of throwing the dji_controls away and implement something like a pixhawk - maybe that's the way to go...