PX4FLOW & position hold

[Matthew]

Hi

I'm looking for a way to achieve precise position hold with M4 controller and without GPS signal (indoor). I figured the best bet would be PX4FLOW sensor. But is it still supported in AQ firmware? How much work would it be to achieve a good result? I do have some electronics skills but not as much programing experience.

The second thing I'd like to achieve is hover and position hold without radio in the system. Possibly drone would be placed anywhere in space, user would push a button, motors would start to work and M4 would try to hold the position given by PX4FLOW sensor. Is this achievable? To be frank over 200 files of AQ firmware looks a bit scary and I don't know where to start.

[kinderkram]

Bill and Peter have played with PX4flow some time ago with AQ6 and M4:




And there have been tests with LIDAR for position hold and obstacle avoidance:

[Matthew]

Thank you for the answer I have seen the first video along with Bill's topic on the forum. The results are great but is there any instruction how to achieve that? Is connecting M4 USART port with PX4FLOW USART port enough? Which firmware version should I download?

[sandmen]

[Matthew]

[sandmen]

Only some lines in AQ....
Need to check that.
Otherwise, on Px4Flow, Bill's changes are already in the official FW.

[Matthew]

Hi

I guess there is no need to create new topic. My quad finally flies. It turned out that PX4FLOW really works out of the box. You just have to connect UART.

Unfortunatelly I experience a significant, horizontal drift in position hold. It has a rather constant speed of 20 cm/s. All test I do are indoors, and every time, after about 5 seconds I have to land the quad to prevent it from crashing on the wall. Please help me resolve that problem.

First of all I couldn't find any information on how to calculate UKF_FLOW_ROT parameter. My AQ is fliped around Y axis, while PX4FLOW is mounted like in this picture https://pixhawk.org/_media/modules/px4f ... tok=8dfdcf with front of the quad on top of the picture. I tried all 4 angles (0, 90, 180 and -90) but there is a drift every time. Once I connect AQ to QGC, move the drone above the ground and observe position on the screen it seems to don't change logically. It only works well if I hold the quad fery still.

It would probably be much easier to diagnose the problem once wireless telemetry would be working. I have a bluetooth module but UART on AQ is connected to FLOW sensor. I found an information that there is a second UART but if I am correct it's on the same pins as PWM output which is used to connect KISS esc. GPS module is not used in my setup so theoretically I could desolder the module and use it's UART. Would that work? What changes to the code shall I make?

Before tests I performed tare leveling, IMU calibration without temperature calibration and changed PID values for tilt and YAW.

[Matthew]

Ok I made a progress in the subject of telemetry over bluetooth. I discovered that external esc can be connected through ports 1 - 4. So I switched connections from ports 5 - 9. They work like a charm. By doing so UART6 become accesible. I soldered bluetooth module but it doesn't seems to work. The problem is very similar to the one described in this subject viewtopic.php?f=33&t=4389 . I have already tried switching TX <-> RX cables and tried both COM ports in QGC.

In board_m4_r6.h I found the line "//#define COMM_PORT3 USART6" and uncommented it. This change alone didn't make bluetooth work. Are there any other changes neccesary to enable UART6? Or is there some other solution?

[Max]

[Matthew]