Last weekend was my first real time to fly the hex fpv. The wind was blowing very hard. If I had to guess I would say up to 25+ at times. However determination kicked in and I fpv’d the hex which to my surprise didn’t mind the wind too much. The video looked horrible but the machine was flyable. In preparation for the fpv I cut a new sonar mount, fpv camera mount system in the front and a simple battery tray for the rear. All but the battery tray is shown in the pics below, still need to take a picture of that. The fpv camera mount is home to the video transmitter, OSD (underneath) and the fpv camera. I wanted the unit easily removable and as a unit. The camera is my trusty Pixim Seawolf 690tvl camera. The best fpv camera I have used yet. It is a bit heavy but the picture is really good and it will shrink the sun when looking directly into the light. As for the Sonar I tried to keep in mind that it needed to be 3+ inches away from the main body. The wire that I have seen most people use was a standard servo type 3-wire cable. After some research on getting the most from my Sonar I leaned that the Sonar is very sensitive to emf interaction either to the Sonar itself or the cable carrying the data to the flight controller. I located a piece of shielded cable in the shop which is surplus from another project and used it for my Sonar. I soldered in a right angle header to the sonar board for a neat clean wiring job. For what its worth the sonar is absolutely rock solid and I couldn’t be happier with it. Using shielded cable is highly recommended. One other notable point is I checked the balance on my Graupner 14″ props. The Graupners are quickly becoming my favorite props but the set that I have definitely needed balancing. One of the six only needed balancing tape on the blade. All the rest needed quite a bit of work on the hubs and the blades. I did manage to get some more of the jello out of the video. The battery cables were vibrating off the back of the gopro case so I’m not real sure how much I eliminated. Next major change to the hex is a relocation of the power wires. Then I can get a better measurement on the removal of jello since nothing will be rattling around.
My buddy Drew and I flew yesterday for a while (video below) and I went back out today to do some more setup work on the hex. It was good yesterday but initiating rtl or loiter was quite a shaky affair. After some PID tuning last night today was a little better. Good enough to perform a ‘return to launch’ and then ‘auto land’. Both of which make me very nervous. As seen in the video below there is still some oscillations in loiter mode. However, in the flight controllers defense, the wind was blowing up to about 15mph at times and then down to nothing. I am going to edit the settings again in an attempt to achieve a shake free loiter. One thing I did learn was that there is a slight delay from when you invoke loiter to when the flight controller actually takes over. Once the switch is flipped, continue to hold position for a 3 count and your set. Before that I would flip the switch and the hex would wander away about 20′ then go back to the original location. After the three count procedure it never leaves the original location.
My minimosd really helped me feel more at ease on the auto land and return to launch today. Once I flipped the switch to return to launch and let go of the sticks (but still held the radio tight.. lol) and rode along via fpv keeping a close eye on the angle meter and altitude. The hex rose a little to meet the minimum altitude for RTL, promptly flew to the spot where I armed the flight controller and began to auto land. It did overshoot the target by about 20′. The PID’s need to be adjusted to slow it down a bit. When RTL kicked in the hex rose quickly and wasted no time going to the target. When it came time to auto land I watched the altitude slowly click off. The hex was descending nice and calm. I will admit about 3″ off the ground I jumped the gun and turned it off. The stick throttle stick was up just a touch which is why it popped back up. No harm no foul. Now I can set my fail safe to return to launch and know everything should be ok.
Pictures AJ Goin took of the hex last weekend.
Video 1. Stock PID’s for loiter, rtl and auto land.
“Video starts at 1:23. First attempt at loiter with stock PID settings 2:00-2:14. There is some wobble but its not too bad. The wind was blowing some. Return to launch starts at 3:05. The hex overshoots home at 3:22 and then is on the ground via auto land at 3:40. I turned the switch off upon landing but didn’t pull the stick down. At that point the hex jumped a little. Other than that the APM performed great. I did manage to tune the PID some more in a second video (which I will post in a bit) and got more of the wobbles out.”
Video 2. I edited the PID’s for a little better Loiter and did some hands off floating. lol