This video shows my first loops and rolls with the DJI Naza F450 Quad. I did at least one in every direction (left, right, forwards and backwards). The entire flight was flown via FPV which I found much easier for these moves. Flying line of sight at this height and distance makes it hard to maintain orientation.
A guy that started flying the F450 about the same time as me told me how he tried to roll it, it got half way and dived into the ground. Broke an arm or two and some props. Thanks to the well thought out F450 frame, he was back up and running in no time but after hearing such a tale I was a bit apprehensive to try it myself..... until now. With my FPV gear up and running it's much easier to gain a lot of height and maintain orientation.
The setup is a stock F450 quad with 8" props and 4S battery (4000mAh on this flight). Other than the gain settings as described here (http://fangin.com/blog/2012/08/07/dji-naza-f450-gain-settings-flips-and-rolls/), there's not much to it. Gain plenty of height and bang the stick over. I can see how if the gains were set too low, the roll rate might not be quick enough to complete the roll without losing too much height.
The settings I've been using up until this point were;
Basic Gain: Pitch: 150, Roll 150, Yaw 100, Vertical 120
Attitude Gain: Pitch 70, Roll 70
The problem I found with these settings was under heavy acceleration, the quad would oscillate. The same oscillation would occur with high yaw application and when descending from height. After some forum reading I decided to enable "Remote Adjust" by assigning X1 to the Basic Gains and X2 to the Attitude Gains. The oscillation on descent was apparently due to too low gain on Attitude settings.
By using "Remote Adjust", the gain settings can be changed in-flight and the affects judged immediately. I found increasing the Basic Gains to max the quad would start oscillating even just in a hover. Backing it off a few notches would stabilise the quad and give quite good response to input. Dialling the gains all the way down meant the response was much softer and smoother which meant response to input is slowed somewhat. Without knowing what the actual values were at the time, I settled on gains that seem to be a good mix between control authority and smooth flight. There was still some vibration but I'll work on that.
I think I'll keep the Remote Adjust capability setup on the Quad. Being able to dial back the gain for some slow smooth input for photos and video and then dial it up for some hot-dogging is a great feature. All without having to stop and plug in the laptop.
The gain settings I settled on are;
Basic Gain: Pitch: 104, Roll 104, Yaw 69, Vertical 83
Attitude Gain: Pitch 150, Roll 150
I used the DJI F450 Quad and GoPro v1 to take some photos of a house under construction but found with the GoPro mounted flat on the front tab of the frame, most of the photos were angled too high and showed plenty of the roof of the house but not much more. Also the props were quite prominent in the photos and video. i needed something to angle the GoPro towards the ground but I didn't want to mount the GoPro hanging beneath the frame.
Easy solution, buy one of these http://arkrc.com.au/cpgpmount-crudd-parts-gopro-mount/ . But I prefer to make things where I can so I bought some 3mm perspex from bunnings, cut a 7 x 4 cm square, heated it with a mini blowtorch for the bend and Bob's your uncle, a new GoPro mount.
I threw the 4S 5000mAh battery on the DJI Naza F450 Flamewheel quad. I expected the battery might be a bit too heavy weighing in at 530gr plus the weight of the GoPro camera plus EagleTree Logger, EagleTree GPS and the DJI GPS, the Flamewheel has put on a bit of weight since it's maiden flight. I'll have to weigh all those parts and see what they contribute to the all up weight.
I was pleasantly surprised at the climb rate even with a half kilo battery onboard. The EagleTree log shows I flew for around 16 minutes of fairly sedate hovering with six ascents to high altitude.
This is how I've set my first and second level protection voltage thresholds. I found the default setting with 14.8 Volts in the 'No Load' without any value in the 'Loss' field meant the Second Level Protection kicked in far too early and the Quad became sluggish to ascend. Even at full throttle, it would only rise very slowly. Flicking it into manual mode and the Quad would take off like a rocket. That tells me the battery has plenty of juice left in it but the Naza is artificially limiting the maximum throttle available by slowly moving the mid-point up.
The results from the Eagle Tree logger show a loaded voltage level throughout the entire flight. 14.4 and 14.2 is probably a bit conservative but I'll test it out and see how it goes. I reckon I might change it to 14.2 and 14.0. We'll see.
****Update - 5th July 2012
I think these values are too conservative. On the last flight, 2nd level kicked in and I still had about 50% left in the 2650mAh 4S. I've set them to 14.2 and 14.0 (zero loss) and will do another test flight. The Eagletree logger is fantastic for this type of problem.
On the left is the original footage from the DJI Naza F450 GoPro. On the right is the "stabilised" version. By uploading the original to YouTube, applying the stabilise, then downloading the MP4 and running it back through YouTube you're able to see a side by side comparison.
The stabilised filter has some funny side effects where it appears as though the video is suddenly zoomed in and out. The blurriness of the RHS probably isn't a fair representation because that side has been uploaded, compressed, and downloaded.
The process does crop the video slightly and uses the edges as a buffer to remove the sudden movements from side to side or up and down.
The videos are in pretty good time sync but you may notice the RHS looks like it's behind the LHS. This lag is due to the smoothing effect of the filter and sudden movements take a little bit more time to catch-up with the RHS.
I've since changed the mount that the GoPro uses and without any post-processing the video is quite smooth. It will be interesting to see how smooth a video would look from the new mount after applying the stabilise filter.
Overall for this type of video, the stabilise filter does a pretty good job.
The shots below show my settings in the DJI Naza Assistant software for the X, Y & Z co-ordinates and what that translates to on the Quad. The first time I flew with the GPS, I didn't bother to set any parameters and GPS mode wasn't very good. As soon as I activated it, the quad would bank left and drift quickly until I re-engaged attitude mode.
I made three changes before the next flight. 1. Mount the GPS on the stick provided, 2. Point the arrow on the GPS towards the front and 3. Enter the co-ordinates in the software configuration. After another test flight, the GPS holds position pretty well. What I don't know is what had the most effect (the mount, direction or co-ordinates). I'm hoping it's the co-ordinates in the software because I'd prefer not to use the stick mount because it makes it bulkier to pack and more prone to damage on a hard landing. I think I'll try going back to double sided foam tape and mount it directly to an arm.
The pictures below show these settings X = -4cm, Y=4cm and Z=-9cm and what they look like in the real world.
The first full flight with the EagleTree Logger v4 running on the DJI Naza F450 with GPS. The first 140 seconds show little activity while I plug things in and wait for GPS lock. When I eventually takeoff with a 4S 2200 Nano-tech LiPo, the voltage drops to 15.4 Volts and within 40 seconds drops down to 14.8 Volts as you'd expect from a 4S battery. It seems to hold the voltage fairly well throughout the flight keeping in mind it was fairly sedate backyard hovering with the GoPro onboard and recording. The voltage seems to start decling quickly after about 500 seconds where there's a few spikes in current and corresponding drops in voltage where I did a few short sharp rapid ascents with the throttle wide open. At about 670 seconds, the voltage drops too far and the second level protection kicks in where the Naza automatically descends. For my liking, it descends too rapidly but I'm not sure if that might be the result of setting the second level voltage protection level too low so there's nothing left in the pack to land safely. I wonder if I up the Voltage level, will the descent be more controlled when the Naza takes over.
I got about 2,000 mA out of the 2,200 pack which seems fairly good. The quad is loaded up with a GoPro, Naza GPS, Eagletree logger and Eagletree GPS so it's carrying a little more weight than usual. 8.5 minutes hover time seems pretty good I reckon. Average current draw with the 8" props is around 13 amps with a peak at 24.5. The 30Amp ESCs should be more than comfortable to handle that load.
This was the second flight with the DJI Naza GPS and all went well. There's been many rumours floating around the forums that the GPS doesn't work so well in the Southern Hemisphere (SH) and after my first flight I was worried they were right. During that flight, whenver I activated GPS mode the Quad would veer off to the left and never recover. After entering the X,Y,Z co-ordinates in the software configuration and mounting the GPS on the stick, it works great. At most the drift was maybe 1 meter but most of the time it seemed to hold position withing bout 30-50cm.
Next mission - Test the Return to Home (RTH) feature. I'll need a bit more space than the backyard though because it's supposed to ascend 20 meters, return to base, then land. Need to make sure there's no trees in the way. At the moment, the only way I have to trigger failsafe mode is to switch off my transmitter. That could be a bit nerve racking. In all my years of RC flying, I've never deliberately (or accidentally) switched off my Tx in mid-flight. I might have to make sure to have the video camera recording that one.
I'm not saying it's the best way, it's just how I do it and it seems to work well. Velcro on the bottom of the GoPro, velcro on the part of the F450 frame that sticks out the front then wrap a length of velcro around the entire camera. The "shutter" button can still be easily operated through the velcro.
Simple, light and works. I used to use the protective case but what's the worst that could happen. If I write it off, I'd have to replace it with a new version 2 GoPro. Damn. 🙂
The DJI Naza GPS arrived today from Queensland, ordered from Quinton Marais (firstname.lastname@example.org). I must say his postage time is quick. I ordered it Wednesday night and it arrived at work in Melbourne Friday morning, just in time for the weekend.
The unit comes with a little 2 inch mounting pole that I guess helps elevate the GPS and Magnetometer from surrounding interference. Somewhere in the manual it talks about sensitivity to both vibration and magnetic field. I reckon the vibration would be worse when mounted on the supplied pole so I've gone with directly to the arm. I used some doubled sided foam tape to hold it on the arm.
A quick test in the backyard and it took maybe a minute from coldstart to acquire a full GPS lock. You can tell that by the colour and sequence of the flashing VU. When the controller is set to GPS mode, and before satellites are acquired, the VU will blink RED, RED, RED, GREEN. As more and more satellites are acquired, the number of RED flashes decreases until the VU flashes GREEN about once every two seconds.
No test flight to report yet.
** Update 6th July.
I've since moved the GPS onto the stick, faced it forward, entered the X,Y & Z co-ordinates and calibrated the magnetometer. It works much better now.