An F550 Hexcopter for Aerial Photography

Since I really liked the agility of my quadcopter, I wanted to keep it that way and, so, for a stable aerial photography platform, I opted for a hexcopter.  I got a great deal on a DJI Flame Wheel F550 combo package which included DJI's NAZA-M v2 flight controller with GPS (which is just killa'), a Zenmuse H3-2D gimbal for a GoPro camera (which I already have) and DJI's landing gear so that the gimbal and camera can be mounted underneath the copter.  All of this should make for a very stable aerial platform.

NAZA-M V2 Flight Controller

NAZA-M V2 Flight Controller

The assembly followed much the same procedure as that for the quadcopter project although the setup of the NAZA took a little while as I wanted to familiarize myself with the assistant software and all the features of the NAZA controller (it will supposedly fly OTB but I wanted to dig into its features).  Also,  since I have an older Spektrum DX7 transmitter, I needed to perform some custom programming in order to allow me to activate the various functions on the NAZA controller (like the Return-To-Home fail-safe option).

The first thing I tested was the GPS-lock mode (commonly referred to as Loiter Mode).  In this mode, the flight controller should not only hold the attitude of the vehicle, but should also keep it at a given location in space - this includes altitude.  In this video, the ability of the F550 to return to its prescribed location and also its ability to takeoff and then land on the same spot is tested.  Before mounting and possibly losing expensive camera equipment, it was necessary to test the ability for the F550 to be easily and steadily controlled and recovered.  As can be seen in the video, the NAZA FC kept the F550 on the spot.  With a good lock on several satellites, the NAZA performs extremely well in this role.  The controller does have a sluggish feel to it.  It flies very well and with much stability and it feels like it.

It is important to realize that these vehicles are unstable by design and would crash very quickly without a controller, (although not so much that it can't be flown manually by a pilot).  Consequently, any computer-augmented control is really a fly-by-wire (actually wireless) design.  Different flight characteristics can be build into the flight controller.  In the case of the NAZA-M, this controller is designed to be smooth and stable and flying the quad with it feels that way.  Switching the controller to manual really gives the F550 a much more aggressive nature.

In a rush to get some aerial photography (AP) going, I decided to mount my GoPro directly to the F550 using one of the standard mounts that came with the camera plus some double-sided tape.  Video was a little choppy, but great to see.

Zenmuse H3-2D Gimbal

Zenmuse H3-2D Gimbal by DJI

Having satisfied myself that the flight controller was working properly, I then proceeded to mount the Zenmuse H3-2D gimbal on which to mount the GoPro.  This Zenmuse is especially designed for the GoPro camera.  It holds it, stabilizes it and allows one to remotely control the camera's shooting as well as controlling the pitch on the camera.  Since the Zenmuse it 2D, it stabilizes in pitch and roll only.  Additionally, as mentioned, the camera can be remotely tilted using the transmitter.  Yaw control of the camera is performed by yawing the vehicle.  When the battery is connected to the vehicle and the gimbal powered, the GoPro will recharge itself.  Additionally, the gimbal provides a video out line which can be used to send the video signal to a video transmitter for real-time viewing at the ground station.

Unfortunately, the Zenmuse does not attach readily to the frame of the F550 (which I found very strange since both are made by DJI - it does, however, attach readily to the frame of the F450).  For now, I simply attached the mounting plate of the gimbal to the underneath of the F550's hub using cable ties.  This worked pretty well except that (because of the wide angle lens of the GoPro) the langing gear appears in the camera's view.  Soon I will 3D print a custom mounting plate for the gimbal that will take care of this.  For now, I will just have to live with the sight of the landing gear.  Initial testing of the Zenmuse gimbal shows that it works very well in stabilizing the camera.

The real test, of course, comes from flying the copter.  Took the F550 up over UCLA for a scenic flight.  Zenmuse results in a beautiful, stable picture.

 

 

Back at the park for another go round and starting to put the F550 through its paces.  Flying it more and more aggressively as I develop a feel for its performance.

 

Return-To-Home (RTH) Failsafe Setting

Before adding too much expensive equipment to the vehicle, I wanted to ensure that the the controller's failsafe feature was enabled, active and working correctly.  The idea here is that in case of an emergency, I can flip a switch on the radio and the RTH function will be activated.  When activated, the vehicle will climb to 20 meters (this can be adjusted) if it is below that altitude, return to the location from where it took off and will land itself gently (assuming sufficient power remains in the battery).  If, when RTF is activated, the vehicle is above 20m in altitude, then it will retain that altitude, fly itself home and land.  In the event that the vehicle flies out of range of the radio and the signal drops, the NAZA will automatically enter RTH mode after 3 seconds of signal loss.  The video below shows a test of the RTH feature.

First Person View (FPV)

The idea behind FPV is that by attaching a video transmitter to the hexcopter, we can turn the GoPro video with a live stream that can be viewed in real-time at the ground station using either a video monitor of a pair of video goggles.  Using this video image, the pilot can control the vehicle well beyond the visible range by, in effect, putting the pilot in the "cockpit" of the vehicle and allowing him to steer from that point-of-view.

MORE SOON...