Lumenier QAV250 Mini FPV Quadcopter

The QAV250 quadcopter is a small FPV quadcopter which can also carry a Mobius camera. Its design provides an unobstructed view for both the FPV and HD cameras.

 Pixhawk Spektrum Satellite RX and Mobius camera on top

Assembly

The ARF assembly guide is here: Build Manual

There wasn't quite enough room to orient the Pixhawk lengthwise, so I rotated it 90 degrees and positioned the 4 foam mounting pads as far apart as possible on the frame. Don't forget to specify the correct autopilot orientation when you are setting parameters. The buzzer is mounted to the bottom front of the frame with servo tape and the safety switch fit neatly in one of the holes at the rear of the top frame. To save some weight and make power cabling easier, I removed the XT60 from the output end of the power module and soldered its leads directly to the PDB. Flying weight as pictured with 3S/1300mAh Nano-tech LiPo and Mobius camera, but no FPV gear is 547g and hover throttle is about 50%.

PDB and power module underneath

The photo below shows the QAV250 with the smaller form-factor AUAV-X2 instead of a Pixhawk. It is mounted underneath the top plate to move it further away from the EMI generated by the PDB and ESCs. This allows flight without an external GPS/compass since the internal compass is usable with the reduced EMI. Note that the X2 is mounted in a sintered nylon case with a “baro chamber” which may be ordered from Phil Kocmoud's Shapeways store: nylon case (top) Also note that you must order the top and bottom case halves separately. The baro chamber reduces sensitivity of the barometer altitude to pressure effects created by wind and turbulence.

AUAV-X2 mounted under top plate

Maiden Flight

With default parameters for DJI F330 (autostart ID:4010).

Mobius video

FPV Flight

Beginning to get the hang of throttle management:

clipping twigs and skimming grass

ALTCTL Mode Flight win new QAV250 airframe config

Letting the PX4 Firmware control altitude (X2 in Shapeways case / no GPS):

Mobius video

Configuration and Tuning

This configuration uses the AUAV-X2 small form-factor autopilot and the (default) Q attitude estimator.

The QAV250 has stock ESCs and motors with 5×4.5 HQ bullnose props, 1300mah 3S LiPo and the field altitude is about 1 mile above sea level. At sea level, 5×3 props would behave similarly.

A complete flight log is here: http://logs.uaventure.com/view/WeDwjj8RAwK5deDVQbDZkf

In this initial test flight with latest master, the QAV250 is very tail-heavy, and the PID parameters were tuned for a configuration with better longitudinal balance (no GPS or Mobius camera installed up front for this flight).

This flight log is a good demonstration of how the integral error term functions in the PID pitchrate controller.

 approx. 30 seconds for integral windup

Rollrate tracking is good immediately on takeoff, since there is no steady-state error due to lateral imbalance.

 good lateral balance, no initial steady-state error

Here's a flight test of the min/max thrust parameters for auto and manual modes: http://logs.uaventure.com/view/R7vmBXjMWqgY7VvGrH6gv8

The minimum thrust value of .06 is low enough to allow rapid descent with a small degradation of attitude control:

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