Back in early January I was tasked with the duty of delivering my recently quadrupley bypassed father to my aunty's house down on the south coast of New South Wales for some much needed rest and relaxation. As it happens, the quiet sleepy town of Moruya, in which my aunty resides, is also home to Hobby King's Australia based warehouse. Not being one to pass on an opportunity to double task efficiency, I decided after depositing my father into my aunt's capable hands that I might as well make use of the ample cargo space offered by my humble little hatchback. So I dropped in to grace to the good people at HK Aus with some good old first person custom.
To cut a long tangent short, this is what I brought home with me:
The 1500x300x400mm shipping box of the UAV-3000 was a tight fit, but no problem for the jack of all trades GTi.
Anyway, while I was there in the showroom, I noticed a few warranty return/clearance items on the bench at heavily discounted rates. Among these items was a folding multirotor platform. The IdealFly IFLY-4, with which a former customer had apparently had little success, appeared to be a nice and entirely complete airframe which simply needed a new FC. Keen for a new build, I swapping it for a single John Flynn, bid the HK team a good day and headed north.
Once at home I did a bit of research on the IFLY-4 and was surprised to find out that, due to the fact the IFLY-4 ESCs communicate via I2C, I would need to replace these as well as the FC. So, I set about ordering the following items:
* APM
* GPS/MAG
* Afro Slim ESCs
* I also ordered a motor to replace one with a bit of play in it.
When these items finally arrived last week I set about assembling my new craft along with a few extra items from the parts bin including camera, RCRX, power meter, BEC, cables, fasteners, and batteries.
Introducing the IdeaFly IFLY-4 Reloaded - APM Edition.
You know how with some builds nothing seems to go right? When holes don't line up, you can't seem to find the right sized fasteners, you are forced to think and rethink, mount and remount, route and reroute and repeatedly forced to retrieve tools that are out of immediate reach? Well this build was nothing like that. It just seemed to come together beautifully.
I had originally modified the factory distribution board with the intention to recycle it for it's former purpose however, after damaging some of the PCB traces I realised it really didn't have the current carrying capacity I would like, so I just used it as a mounting platform for the APM, which was attached using soft double sided adhesive foam, choosing instead to deal with power distribution at the Power Module.
I was really pleased with my work on the Power Module. It is very very strong (much stronger than I expected, and it has been tested with great force), super compact, neat and convenient for maintenance. A Turnigy 3A BEC powers all 5VDC needs with the exception of the camera, which is left to rely on it's own on board battery (no chance of nasty noise entering camera).
Amazingly, after removing the factory I2C ESCs, I found that the Afros slotted very neatly in to the arms. Having read about others having issues with Simon K ESCs and AutoTune, I was a little worried about having problems with the Afro Slims, but I simply had to persevere due to their convenient size, affordable price and strong performance credentials. I am not exactly using them in a low kv pancake applcation either, so the "she's be right, mate" attitude prevailed. Just a dab of hot glue was required to firmly hold them in place. I was worried about using hot glue on such a heat generating component, but they don't seem to warm up much at all, as the chipset is 30A rated and they are running at less than 50% duty at max.
The GPS/Mag was purchased on ebay for about $18. It is mounted on a re-purposed FPV camera bracket which I flattened and fastened to the front of the frame using hard double sided adhesive foam and two zip ties giving a solid but nicely dampened mount for the GPS/Mag. Mounting holes were a perfect match, and I had all the right nylon M2.5 fasteners and spacers in the tool box to suit. TIP - Invest in an assortment of M2.5 and M4 nylon and SS fasteners, as it will save you so much build time.
A 433Mhz Telemetry Radio from RCTimer is mounted on a short 2-inch boom at the back of the centreplate in the same way outlined above, but with two M2.5 bolts added to ensure it remains firm and alignment stays true.
For battery duties I decided to use the 3S 2200mAh Turnigy, of which I have several. It is about 25mm too short to span the top centreplate and corresponding anchor points, so I fabricated a hold down plate to solve the problem. Keeping weight to an absolute minimum, the hold down bracket is made from Balsa wood, painted black with a texta and enclosed in clear heatshrink. The bracket is plenty strong and weight is less than 10 grams.
At this point, I had the basic hardware sorted and moved onto setting up the firmware and configuring all relevant settings in Mission Planner. This is not my first APM setup, so navigation was pretty straight forward. I did use Mission Planner instead of APMPlanner2 due to familiarity though, and I did go through some fiddling getting the right hex and character set for MinimOSD Extra (hence why I didn't tune better position for the telemetry info in the 4:3 frame - I just wanted to move on once it was working effectively). I was also surprised to learn that the only firmware setting on the Afro Slims able to be set by the user without the USB programming tool is the max and min throttle points. With the USB programming tool riced at just $6.65 this would seem an easy up sell if only mentioned in the ad.
Ready to fly, I grabbed my Nexus 7 ground station and a battery and headed out to the backyard to burn through a charge on the standard settings. As usual, the APM's default PIDs worked fine out of the box. Super pleased with myself, I headed back inside and proceeded to invest several hours sanding the props into perfect equilibrium.
Next I wanted to try AutoTune for the first time, having witnessed Ian Lions perform this operation with his TBS disco earlier this year. So I grabbed another battery and headed for the park. Ardupilot performed it's dance with effortless finesse, delivering an exciting but otherwise unremarkable result on the first attempt (only ~800mAh consumed). The improvement in flight performance was immediately recognisable and I was just overwhelmed by how precisely it could be maneuvered and positioned. What a fantastic afternoon!
That evening I headed home and began adding the requisite parts to enable FPV and aerial video capture.
For imaging duties, I chose the little Mobius Action Cam. It is a great little camera, offering 4/5ths of a gopros performance and convenience at just 1/5th of the price. Plus, it is a significant upgrade on the #26 808 I was using previously. The file format it generates is much easier to work with too, as it imports into iMovie for iPad/iPhone for fast easy editing and convenient upload to youtube.
For mechanical isolation I created two small plates from balsa wood roughly the size of two moon gel rectangles placed side by side. The top plate was cut to tightly tessellate with the exposed bolts on the underside of the GPS mount and the bottom plate was left flat. The two balsa plates were sanded and coloured with texta, moongel was placed between these two layers and the sandwich loosely wrapped in cling wrap. This gave a really nice surface to mount against and the whole thing is held in place by a relatively loose fitting velcro strap with an extra piece of moongel added below the camera for good measure. The results offered by this isolation method have proved very pleasing. First Person View of telemetry overlayed video is transmitted back to my DIY Ground Station via a DIY 5.8Ghz VTX.
The next day I jumped in the car and headed up to my sister's place in the mountains in order to give the newly updated rig a run. The whether was overcast, but relatively mild. I ran down two batteries and got some nice test shots. Unfortunately, I also lost the canopy during a particularly fast decent. The great news is that I was traveling backwards at a rate of knots when it fell so I was able to capture the descent of the canopy via the onboard camera. Using the below images the canopy was found the next day.
Smitten with my new craft, the next morning I set out at sparrow's fart for more flights. Overly eager, I was up and ready too early and cursing Siri for making me wait.
30 minutes before sun up I was parked down at Old Government House in UNESCO world heritage listed Parramatta Park. The second I saw the first few photons shoot in my direction I was away. I was starting to gain real confidence in the reliability of the craft at this point. All features and functions, like loiter precision, just spot on.
Reviewing the video from these early morning flights exposed the low light and exposure balancing limitations of the little Mobius. But there are only so many photons a tiny lens and sensor can collect in 33.3-millisecond.
I continued with more flights, moving from place to place. I drove between locations and carted my little integrated ground station so to record both telemetry (via DroidPlanner) and live video stream (via SD DVR installed into DIY ground station).
By mid morning I had been to several locations and had put about half a dozen charges through the craft.
I went home to download and review the media from the Mobius. Most flights were conducted twice, once recording 1080HD@30fps and then again recording stills at 250-millisecond intervals. It seems logical I should have realised this earlier, but the Mobius is not able to deliver live video out while simultaneously capturing and recording 3MP images 4 times a second. Mobius prioritises live output over still image capture, so I didn't pick up on this issue until getting home. Sadly, all the airtime spent capturing stills gave just gave me hundreds of images like this (the panoramas above were recovered from these corrupt files):
Then I set out again, revisiting many of the locations I had shot at earlier in the day. After getting another half a dozen or so more flights under my belt, I returned home at about noon. I put the Mobius and the installed 2200mAh Lipo on charge and grabbed a quick bite to eat for lunch. Before downloading the media from my second morning outing, and (for the first time in 2 days) without bothering to link DroidPlanner and operate the flight recorder in my ground station, I set out into the backyard to get a nice panorama of nearby Lake Parramatta and the surrounding woodland.
While performing the same pirouette maneuver (at about ~40-metres AGL), just as I had done so many time before, I noticed the craft drift noticeably beyond previously experienced limits. I immediately aborted the maneuver, and attempted to recover but failed.
What happened next is not entirely clear. I think I switched to stabilise mode, but this did not help. I then went for loiter mode, but the craft continued moving away from me at an accelerated rate. So I think I went for loiter again, but that didn't arrest the craft either. Next I remembered that RTL was associated with channel 8 so I flicked that, but this didn't help. I then remembered the the RTL failsafe I had set in the event of loss of RCTX link so I switched the transmitter off in the hope this would return it to me. Unfortunately the craft was ~300-metres away from me by this time, and it was not coming back.
In a state of fright, I jumped in the car and scanned the streets for about an hour. Nothing. It was gone. What the hell did I just do I wondered? How could the craft be so predictable and so obedient, just to go and do it's own thing all of a sudden?
Upon reflection I realised that my perception of what happened and what I was doing was probably not as accurate as I would have liked it to be.
First of all, how sure was I that I was pirouetting in loiter? Could I have been in alt hold instead? That would have explained why the craft went off alignment. I am really not sure about this, but my assumption is to blame myself and not the hardware. Also, were the mode commands I sent the craft following loss of control correct? Probably not, no, not at all actually. My channel 8 switch which has always previously been used for RTL failsafe was, at the time of the incident, still associated with AutoTune. So, when I flicked the channel 8 switch (the moment it went out of sight) I had shot myself in the foot. Next, turning off the controller would have been a good idea, but only if I had returned FTL to channel 8. In actual fact, by turning off the RCTX I had totally doomed the craft. Air Craft Investigation seems to reveal that I am completely to blame.
Ashamed, embarrassed and disappointed, not knowing what else to do and having no idea where my craft had ended up, I headed down to my local area command to file an incident report.
What a weekend!
Comments
@Oliver 5.8 is quickly lost with a free trees get in the way.
Try using your tablet in front of your house with less obstacles as opposed to another direction with more walls. VEry quicly you will lose range and data will slow down.
To be precise, Stabilize and max or minimum throttle is my goto. And this works even in Stabilize mode.
The other thing I should mention is the Stabilize and low throttle option. I try to keep the throttle just above the level where the motors cut off until I hit the ground. This rotates the copter to level rather than just let it tumble.
As I have become more confident I find the most regular "oh crap" moment in a normal release is acro. However, I spend most of my time testing and flying new code and I am often confronted with a big bug that I have introduced that means I have to switch back to stabilize to save the copter. Thankfully these bugs tend to get filtered out by me, then Randy, then the simulation tester, then the large number of beta testers. Most of the time they don't survive to Randy and very rarely to the simulation tester. (Reassuring tone used here) :)
@ leonard and ian and everyone else...
if stabilize is your goto for panic mode, what are you usually flying in?
i've only had a few flights on my f450, after learning on a little hubsan 107, so i'm mostly comfortable in stabilize at the moment.
unless it turns you find it or not - let it rest in one cool peace, i imagine how it upsets to have gone the aircraft, almost lost an fpv plane once
I got mine up and running just the same last
weekend!
running real early apm2.0 from 2011 (turns it's working great)
previously i had hangups and sudden drops from stabilise due to only power supply inconsistive voltage drops.
managed to grab faulty aircraft with hands just before too late.
i flew having logging mask turned on and with ground station as a rule.
and just after 3 totally first successful flights 15 mins each with total automation (never imagined i'll be brave to do it so early, just how really cool this feature is)
my logs totally could not be read anymore.
anyway nothing so precious as experience one step a time though
cheers. E.D.
Very nice build - hadn't though to wrap the moon gel in glad wrap - amazing how much gunk it attracts.
I hope whoever finds it does the right thing.
I'm with leonardthall - Stabilize is my go to place for those oh shit moments. It's one thing to set up the switches - it's quite another to be able to flick them correctly in a moment of panic. The only way to get there is practice drills. I don't trust the GPS enough yet to rely on the fail safes.
The Taranis is great because it gives you audible queues for both flight modes and signal strength. I'm waiting for my Teensy 3.1 so I can route more telemetry data to the Taranis - for those times I don't turn on the ground station.
Thanks a lot for the reply leonard, really good points.
I've only flown a handful of times so far, and have executed the 'zero throttle' procedure... but I assumed that was only because I am an inexperienced pilot :P
you're right though, my copter has turned out to be surprisingly sturdy during my hard 'landings'.
Hi Joe Thompson,
No, I do mean Stabilize mode and full throttle or zero throttle. Generally this "oh crap" moment happens during acro maneuvers, fpv loss of orientation or link, or being about to hit an object, or a GPS glitch before the glitch protection stuff was introduced.
Stabilize and full throttle will immediately level the aircraft and gain altitude as quickly as the copter is capable. Or, as I have done many times, rotate the craft from inverted doing 60km/h directly down and slow the craft as quickly as possible :)
Another one of my favorite is the dog that suddenly comes on the seen that thinks your quad is a frisbee to catch!!! The owner apologized to me and in return I ran the dog 8 laps around the oval as fast as it could go :)
If it is a relatively minor "oh crap" moment I can generally just keep flying as if nothing happened. But in any case I am 20m higher and have time to work things out before I contact an object.
Stabilize and zero throttle is useful if you are below trees and have lost orientation. You have a choice of hitting a tree, building, car in front of you. Increasing height and hitting a roof, tree, or some other overhead object, then probably the object you were trying to avoid in the first place. Or dropping it on the ground and letting it tumble a little but stop before hitting the other objects. This is also a very useful approach if you KNOW you are going to hit one of the aforementioned objects and all you can do is minimise the damage. In any case the copter tends to hit flat and I have found very little damage tends to be done. On the 3dr quad I tend to break a leg or two but I can generally take off and fly back to myself.
And I am sure people are thinking this. Having these procedures fresh in your mind become even more important if somehow one of these objects (or many of them) happen to be people!!!!
Thankfully, I am the only human object I have had to take emergency actions to avoid.
@ Mp1
Thanks for the clarification on the 2.4/5.8, I'm just getting into FPV but am aware of those range limitations, glad to hear that you weren't referring to any basic interference issues.
@ Leonard
Your descriptiopns of your preflight procedures, in-flight checking and also the method for determining long-distance orientation are just outstanding! These things all fall under the category of basic piloting - the lack of which is at the root of many problems, as our aircraft become ever more autonomous but remain subject to all sorts of things that can cause Mr. APM or Mr. Pixhawk to say, "Who, me?". People really need to learn to fly, there's no substitute. Everyone should first get a "toy" quad (the palm-size Hubsans are great) and get to where they can rip around the yard in all orientations, recover from unknown attitudes, recover from lost orientation, and so on. It's fun to learn and is guaranteed to pay off later on.
You situation has provided me a thought of which I plan to address in the main page sometime today. It will propose in the Mission Planner a "Rescue Search Area" in the event we pilots lose control of the aircraft and will plot a search area accordingly. More to follow once I've finished my draft.
I really do not think that I lost signal continuity with the craft but, further to discussion regarding choice of frequencies and sources of interference, below is an image showing the location of the RCRX and VTX. (GPS on front up to, telemetry out back up top, RCRX on one side, VTX down low on other side).
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