Blogs

In this post I show videos of two real flights, the first above for FlightZoomer version 2.0 and another below with the freshly released version 2.1. Both videos show the same automatic flight including an ILS approach. In the videos the replay feature is used to sync the recorded video from the on-board Sony camera with the presentation of the groundstation.

While FlightZoomer 2.0 works nicely and was a huge step forward overall, the video also shows some areas, that leave room for improvement. In particular the LNAV, the VNAV and the ILS autopilot modes worked not as precisely as a Pixhawk based system in theory could.

All this was addressed with FlightZoomer version 2.1, so check out the following video to see how the behavior improved:

Version 2.1 is provided as a functional upgrade. It does not bring a single new button or any UI change, but under the hood a nice number of improvements have been implemented. Existing algorithms have been refined, new cascaded control layers have been added, the ILS can be captured much more robustly, flight plans are followed more precisely and a bunch of bugs have been ironed out.

The complete list of changes is here:

1. The turn initiation time is considered now for the flight path calculations. The turn initiation time is the duration, during which the flight path over ground lags the ideal turn. This change increases significantly the precision, how the aircraft follows the planned flight track.
2. For the LNAV and the ILS Localizer mode deviations along the straight legs are now actively corrected. Prior version 2.1 the aircraft always just pointed to the next waypoint and, as a result, deviations have not been corrected until the very end of each leg.
3. A new algorithm has been implemented in LNAV mode to keep the turn radius constant even if the speed varies a bit. This was required because before the aircraft often deviated from the planned track during turns when the speed was dropping temporarily.
4. Speed transitions have been abruptly prior version 2.1 but now are smooth as well. Every speed change happens over a period of 2 seconds.
5. The vertical flight profile in VNAV mode has been improved. Due to inaccuracies in keeping the standard climb or descend rate, the actual altitude could deviate quite a bit from the correct altitude for a certain position. This is important especially during descends because we are moving towards the terrain and because the end of the descend and the end of the route should happen exactly at the same spot. The new VNAV algorithm in version 2.1 ensures this.
6. Optimization and fine-tuning of the approach pattern calculation. The result is a more realistic and much more compact approach pattern, especially during the downwind and base.
7. The ILS glideslope can now not only be captured from below and after having turned to the final approach course, but from below or even before the last turn.
8. Totally 26 issues have been fixed.

In both videos basically the entire flight was flown with the autopilot. Along the route using the LNAV and the VNAV modes, using the TRACK OVER GROUND, ALTITUDE and FLCH modes for the downwind and base and finally using the ILS LOCALIZER and ILS GLIDESLOPE modes for the approach.

Some screenshots from the second video:

On the next image you can see how precisely the aircraft follows the planned track even during a turn. Consider that the turn radius first is a variable that depends on the cruise speed and the turn rate (angular velocity). In practice also the actual speed and the impact of the inertia on the actual track over ground have to be incorporated:

The second image shows the final approach to the runway 08 of my virtual airport. Consider how the runway elevation has been configured 5 m above the real road, in order to have some safety buffer:

Again I dont want to miss the opportunity to provide some high level information about FlightZoomer:

• FlightZoomer is a top notch distributed avionics suite for drones
• FlightZoomer is entirely a software solution. The hardware are COTS devices (Windows Phones smartphones).
• Why distributed? Because there is an onboard device and a groundstation, both are connected via a Relay Server at home.
• All the components are coupled with a cellular EDGE, 3G or 4G link.
• The onboard smartphone is mated with an APM based flight controller via Bluetooth.
• Currently supported is Arducopter 3.3 or higher.
• Supporting Arduplane is on the to-do list.
• For about 200$ you can get everything mentioned working (assumed, you need to buy two Windows Phones for the groundstation and the sensor device)

Much more details you can find on my homepage flightzoomer.com.

The full documentation for version 1.5 is still valid for the basic functionality:

Version 1.5 full documentation

For the version 2.0 the additional features are described in this 50 page addendum:

Version 2.0 addendum

For version 2.1 there is currently no separate documentation (beside this post :D )