UAVs, Photography, and more Software Engineering than most can stand.
Outback Challenge Deliverable 2 Submitted
So there have been some sleepless nights recently as the deadline for the Outback Challenge second deliverable passed this afternoon. I managed to get my report in by the skin of my teeth after some email troubles (still waiting on the confirmation from the organisers :S ).
Each team had to submit a technical report that details the design of their aircraft and their risk management strategies. We also had to compile a video that demonstrates our on field setup procedure, takeoff and landing and how the aircraft handles carrying and dropping the payload. (more…)
Pulsar 4E Bottle Drop Tests
With the second deliverable for the Outback Challenge quickly approaching it was about time I discovered if the Pulsar could even carry the all important bottle of water.
After a successful maiden flight I took the Pulsar home and began hacking away at it with a rotary tool. The idea was to cut the holes I had planned in the fuselage so the bottle could be attached and the camera could see. This is pretty much what I achieved, albeit with a few more slips and scratches then I had hoped for. (more…)
The Pulsar’s Maiden Flight
So it’s been 18 days short of a year since the Pulsar arrived in a giant box. Since then there has been a lot of time spent measuring and modelling and generally designing to figure out how to fill it with stuff to ready it for the outback challenge.
It took a few attempts at various components to get the fit right. Measuring its sleek, sexy curves proved to be quite difficult. The last few days have been spent shifting things around to perfect the balance and program my recently replaced radio equipment. (more…)
Meet the Pulsar 4E
As I’ve mentioned a bunch of times on this blog and to anyone I came into contact with over the last 12 months: I’m building a rather large glider to compete in the Outback Challenge. I recently finished collecting and assembling parts and am keen to see it get off the ground when all the stars align. You’ll notice that it’s big… really big. And no; I’m not short 😛
The Pulsar range of gliders should be familiar to most RC enthusiasts. They are typically a slow, light weight and very well built aircraft featuring enough carbon fiber to make most cyclist jealous. It is not a scale model, so it doesn’t look like a traditional manned glider. Instead it has been designed from scratch to be a very efficient radio controlled aircraft.
The Pulsar 4E is the largest of the Pulsar series with a wingspan of 4 meters. The one I have assembled weighs 2280 grams without a payload, which is expected to be a little over 500 grams of water and bottle. I have fitted a modest 550 Watt Neu motor to the front which I expect will be just enough power to maintain cruise speed while climbing vertically.
So far, we’ve taken the Pulsar to the airfield twice in attempts to fly it. Unfortunately we’ve been foiled by gusty winds and some really buggy firmware for my transmitter. At least it hasn’t been destroyed yet.
I’ll save my rant about Spektrum’s latest DX8 firmware (2.04) being a terrible example of embedded software and something I consider quite dangerous, as it is sometimes in control of very large and fast aircraft. I’ve downgraded to version 2.01 which I will use cautiously for the time being.
I still have to add the avionics I’ve been working on. I had some plastic mounts printed that served as both the dropping mechanism for the payload as well as holding the electronics in place. Unfortunately some of the dimensions were a bit off and it failed at both of those things. I have some more coming in a couple of weeks and will hopefully have written enough code to make that worthwhile by then.
So while I wasn’t flying anything today, I took the time to make this view of airfield (3MB). Enjoy!
New Avionics
I recently completed building the first of my new version of Asity, the avionics I plan to use in all my UAV activities. The main improvements in this version are the new inertial sensor chip I’m using. I previously had a separate accelerometer and gyroscope. Now I’m using the MPU-6000, which does both much better than what I had. It also does some motion processing of its own which I am dubious about, but I’m going to try it out and see if it can save me writing my own.
The top side of Asity
There are also a number a bug fixes I noticed while playing around with the last version. These are silly things like not including a bias inductor on a powered GPS antenna, supplying the wrong voltage to my compass, and forgetting to put decent pull-up resistors on an I2C bus or two. Fingers crossed that there aren’t more I didn’t find.
The most significant improvements are from a manufacturing view. Given that I’m assembling this by hand with a frying pan, I need to put some effort into the design to make it as easy as possible. This involved swapping a bunch of 0402 sized capacitors & resistors for their slightly larger 0603 versions. I also had to consider how I can fix things as I assemble it, so trying not to block access to my soldering iron. I also have a planned out assembly procedure that involves testing at a few stages. It’s much easier to fix some things before the board is complete, so I try to make sure it all works before continuing. Applying solder paste tends to be the messiest part and results in lots of tiny conductive balls rolling around your components if you do make a mess of it. I ordered some Kapton stencil from OHARARP to make this easier.
The bottom side of Asity
The bottom side of Asity is all hand soldered, so I made sure to choose the components and their layout wisely. This means: no 0402 sized components; no packages with hidden leads (QFN, BGA), and; everything nicely spaced so I can get my soldering iron between things. This last point may have been neglected a little, mostly because there isn’t enough space on the board.
I took two attempts to solder the FPGA on the bottom. The first time was a bit of a nightmare and I spent way too long poking at it with the iron to clear shorts etc. I decided that I had probably butchered the chip and that I didn’t really want it flying my aircraft. So I removed the first one completely, cleaned the pads and started again with a fresh one. It wasn’t a cheap part, but given the components on the others side aren’t particularly cheep either, and they were already working, I decided it was for the best. The second FPGA went on with much less fuss and also seems to work fine now.
The daughter board
I’ve also assembled the daughter board that fits on top of Asity onboard the aircraft. This board includes a VHF radio to act as a backup link if the main UHF fails. It also has an interface to the camera in the nose of the aircraft as well as another FPGA and some RAM to process images data.
So far everything has tested well. I haven’t tried the radios yet, as I still need to assemble the other end of the link, but I’m feeling pretty confident about everything else. It all fits together nicely (there’s a massive radio module sandwiched between the two halves) and only weighs 53g assembled. Now I just have to fill it with useful code.
My Outback Challenge Aircraft
So the massive lack of updates recently has been due to me gaining knowledge in the business management and marketing fields. I’ve been doing some more coursework to complement my PhD and make me generally more entrepreneurial. A fairly painful experience so far, and one which will last for another six months.
Between paragraphs of my business plan I did manage to update the designs for Asity as well as complete the CAD models for the parts I need for the Pulsar. This combination is geared towards completing the Outback Challenge while still being useful to my research. So here’s an attempt to illustrate what I’m building.
This is the layout of the components I intend to include in the Pulsar4E airframe I’ve got lying around. It include the typical motor-ESC-battery you’d find in a modern electric RC plane as well as the avionics and camera components I’ve been working on. You’ll also notice the whopping great water bottle hanging from the bottom. This is of course the all important payload that needs to be delivered to Joe.
The motor, Electronic Speed Controller (ESC) and propeller blades are being carefully selected to allow the whole aircraft to climb vertically with a payload when the throttle is flat out. Once it reaches a comfy altitude, the motor is switched off and the propellor folds back. I’m using a Neu 1110/1Y with 6.7:1 gearbox with a 75A ICE Lite ESC from Castle Creations. I’ve picked a few props with varying pitches to experiment with. I’m expecting the aircraft’s takeoff weight to be around 3 kg, and so aiming for a static thrust slightly higher than that.
The moulded parts shown are all coming from Shapeways. Results so far are promising. The quality is great and my measurements of the curvy fuselage are actually quite accurate. Not so accurate are the dimensions I chose for the servo components in the payload dropping mechanism, so I will need a few bit reprinted.
The payload is suspended from a pylon by two polypropylene webbing straps. I will also add some velcro between the pylon and bottle to prevent it from sliding back and forth. The pylon fits a hole in the bottom of the fuselage and mates with a beefy servo with a metal horn.
The camera is towards the front of the aircraft and also needs a hole cut in the fuselage. The camera I’ll be using is a fairly cheep 1.3MP CMOS sensor; the kind you would’ve found in a phone from 2005. It should be just enough to spot a vehicle from 1500ft, and hopefully Joe from 400ft. I believe the aircraft will be able to stabilise the camera adequately, so I have only included one servo to compensate for the pitch of aircraft. As I’ll be gliding most of this time, I’ll usually be pitched down and will need to adjust the camera.
I designed a small board to transfer data from the camera back to the main processors in the center of the aircraft. The board pictured includes a small LVDS transceiver that will translate the parallel interface of the camera into a high speed serial stream, back up the Cat5 cable to a similar chip which will recreate the parallel interface and feed it into an FPGA. From there it will be appropriately processed and fed into the UHF radio to be sent to the ground.
I’ve also built the first of my latest version of Asity; the avionics I’m developing. I’ll go in to more detail about this in another post, so for now here is a pretty picture:
Pulsar has Arrived
The couriers have visited frequently in the past few weeks, two of them arriving today. The first brought me the new ADCs I need for the Asity prototype, which I should hopefully have complete sometime tomorrow. The second courier brought a rather large box containing the Pulsar 4E that I plan to use for the Outback Challenge next year. This is a big aircraft! compared with the Paprika I built last year, this has twice the wingspan. It’s 4 meters wide and so far weighs about 1100 grams. I expect it to weigh a little under 3 Kg once I’ve installed all the other components and the payload. I’m still working on sponsorship for the remaining parts so it probably won’t be airborne for a month. Right now I’m going nuts with my callipers to try and build a model of the fuselage so I can plan out the other parts I need. This is one disadvantage of a sleek glider; there isn’t much cabin space to play with.
The Outback Challenge was recently announced as a bi-annual event with the next ‘Search & Rescue’ being held in September 2012. While this does interfere with my plans significantly, I do appreciate the extra 12 months for development.
The Shape of Things to Come
I may be using this title a little prematurely… I just finished watching Caprica last night. The last few months of my life (holidays included…) have been spent designing the hardware components for the avionics board I plan to use for my unmanned aircraft. A few days before Christmas the PCB designs were sent off to the manufacturer signifying the design was complete and ready to be built. I’ve since spent my time rereading datasheets and conferring with colleagues, praying that there are no significant flaws in the design. So what is it?Asity is basically a processor, a radio and a collection of sensors that cover everything I need to fly an aircraft autonomously and perform some experiments relevant to my research. The PCB is 40mm x 60mm with the odd protrusion and will easily with into the fuselage of a glider. More specifically:
Actel ProASIC3 FPGA
Atmel ATtiny88
16MB SRAM
32 Mb Flash
MicroSD Card Slot
GPS
900MHz Transceiver
3 Axis Accelerometer
3 Axis Gyroscope
3 Axis Compass
Barometric Pressure Sensor for altitude
Differential Pressure Sensor for airspeed
Temperature Sensor(s)
8 Servo Channels
Current Sensing and power enable on each Servo
Flight Pack Voltage Sensing
Motor Current Sensing
Slave Receiver Headers
12 General IOs
I’m also building an USB daughter board to allow a ground variant to attach to a laptop in the field.Why does the world need another autopilot? There are a number of similar boards available covering a range of applications. The main difference with Asity is that the processor is a Field Programmable Gate Array (FPGA) rather than a traditional CPU. I also intend to write the firmware completely in HDL rather than using any ‘soft core’ processor that seem to be so popular with FPGA developers. This allows for verifiable firmware that can run mostly in parallel. Each sub-system effectively has its own hardware within the processor greatly increasing reliability and timing capabilities.
The challenge is now to gather the rest of the parts and the tools required to assemble the boards, as well as the months of VHDL coding I have to do. Only time will tell if this project will actually work :P.
Video from the Paprika
Having recovered from its tragic accident last week the Paprika was once again ready to fly today. I’m actually still waiting for some parts from the US, so I’ve put a new plastic Graupner prop on it, which is a bit squishier and doesn’t look nearly as slick as the carbon HK I’ve been using. Otherwise it’s the same pitch and diameter. I was also fairly adamant about getting video from onboard the aircraft. The last failure was a dodgey switch so I’ve opened it up to fix it. While I was there, I modded it a little so it can actually point along the fuselage. So the camera finally worked and the result is what I would like to share with you now. It starts a little bumpy while I’m working out the trim, but I eventually manage some low and speedy flybys. I don’t wanna hear anything about my landing! The flaps shed speed a lot faster than I was expecting and I decided that was safer than trying to pull out again.
My recent expedition to the airfield ended abruptly on Thursday with a unfortunate nose-dive on takeoff. I managed to hand launch the Paprika on my own for one flight. After a quick trim, I managed a whole seven minutes of smooth flying and a neat landing with full flaps. The flight only used about 600mAh from my 4S 2600mAh battery, so I could easily stay in the air for over half an hour. The only reason I landed was because the ESC data log was full and I wanted a good snapshot of my flight.
The video camera failed me again. I thought I had just left it on and flattened the battery but after closer inspection I found the power switch had failed. So still no video from the aircraft… The second flight was less successful. Immediately after launch it pitched down and hit the runway resulting in two snapped prop blades and cracked stabilisers. This was probably caused by shifting the centre of gravity forward without removing the tail trim to compensate. The worst part was that this happened immediately after my supervisor arrived. This created some scepticism around the story of my first flight, which was not helped by the lack of video (again).
So another night was spent at the workbench putting things back together. I’m a little relieved that I had the chance to improve the strength in the stabiliser joints. There was not much force involved in the crash, so they could just as easily have snapped off in the air during a hard pull-up. I’ve also ordered new blades and a handful of other things from Esprit Model. They get a special mention as they shipped my parts within 4 hours of me ordering them and their prices are always pretty fantastic. So the repairs are done, I’m just waiting on the new prop and should be back in the air sometime next week, hopefully with a working camera.
Paprika’s Maiden Flight
It Flies! After a bit of foul weather recently we lowered our standards and took the Paprika for it’s maiden flight this afternoon. The sky was a little grey and there was a stiff breeze about, but at least there were no hailstones.
After a last minute check of the surface trims and the flight modes I had set up followed by about 10 minutes staring at the sky and observing the wind to look for an excuse not to hurl my fragile pile of work into it, I was ready(-ish). With a short sprint down the runway, my supervisor did the hurling as I waited for the moment I had control. The initial climb was as expected in that it went up in a less than straight line. The first thing I noticed was the sheer power I had available. It easily climbed vertically at about one third throttle. After gaining some altitude, I levelled off to assess the balance and trim,quickly realising that it was far from perfect. The paprika wanted to pitch the nose up all the time which lead to repeated stalls, stalls that I would not call graceful. So half the flight was spent helplessly tumbling out of control. This was were the excessive power I had came in handy. A short burst of throttle would pull this aircraft out of any tumble with ease giving me back control. This aircraft takes far more concentration than the Hurricane40D I’ve been flying so far. So much in fact that I didn’t dare move my thumbs from the joysticks to adjust the trim as it would almost instantly try to backflip. Eventually one tumble took me so close to the ground that I decided to cut my losses, level out and ditch into the long grass. I was hoping to catch this flight on video from the plane itself and had attached a small camera under one wing. Unfortunately I interpreted it’s blinking LEDs exactly wrong and ended up turning it off just before the flight, and back on again when it was back on the ground. I was also expecting some useful data out of the ESC (Electronic Speed Controller) regarding the motor’s performance but I only have a couple of flat plots consistent with it sitting there doing nothing, which I’m guessing means I need to clear it before each flight. I guess I’ll just have to fly it again.
Overall the experience was quite exciting and I was certainly shaking at the end of it. The aircraft is still in one piece, which classifies a successful landing despite collecting a few grass seeds. It is a completely different beast from the Hurricane40D and there will be a few more exciting flights before I have it under control. Thanks to Uwe, Florian and Pat for their work behind the cameras. I’ll add more of their handy work to this post as it comes to me.
Meet the Paprika
Another long absence ends as I’m done with the crappy business of moving house. Luckily have something new to talk about 😀
This is my new plaything that has recently eaten up all of my time and money. It’s called a Paprika (AKA Gem) and is the RC glider I’ll be spending a lot of time with over the coming months.
Some stats:
Wingspan: 2m
Weight: 1.515kg
Wing Loading: 4.23 kg/m^2 (13.86 oz/ft^2)
Length: 1.2m
Airfoil: MH32
I’ve gone well overboard with the power train starting with a 100A Speed Controller and ending with a 12×6 folding prop. In the middle is an 850W Hyperion Brushless motor which will easily be capable of vertical climbs. The rational of course is efficiency. I expect the most efficient state for this aircraft will be when the motor is off and the prop has folded back, so the quicker the climb the sooner I can get back to gliding. This glider won’t actually be the most efficient aircraft it can be, but it will give me plenty of flexibility to try things.
I’ve upgraded my old 36MHz radio to a very snazzy Spektrum DX8. This thing is incredibly complicated compared to the old 4 channel with mechanical trims. It does include a telemetry module to keep me updated on the numbers onboard the aircraft which is nice, but it’s gonna be weeks before I wrap my head around how all the other features will benefit me.
I also have some other toys, including a camera and some solar panels. I’m not expecting fantastic results from either of them, but they will hopefully be enough to inform some avenues of research and of course more money spending. I’ve also picked up a cheep EeePC to act a ground station. For now it will just be downloading ESC logs and video recordings, but eventually I’ll have some kind of interface to the auto-pilot I’m in the middle of building. Maiden flight will hopefully be early next week – weather permitting.
Flying
So the ‘final sprint’ I had anticipated has been more of a ‘sit and wait for parts’. Belts arrived today and my epoxy gears don’t really seem adequate anymore. I’ll probably make some new ones using the belt as a mould. I’ve also just sent off an order for the last of the bits I need from MakerBot, so hopefully not too much longer… I’ve also been working on some super secret new idea that I’m not going to reveal until I know it’ll work 😀 more on that later. In the meantime, here are some shots of my plane from the other weekend. Actually flying this time! Thanks to Jan Zimmer for these.
I’m still working on sponsorship for the remaining parts so it probably won’t be airborne for a month. Right now I’m going nuts with my callipers to try and build a model of the fuselage so I can plan out the other parts I need. This is one disadvantage of a sleek glider; there isn’t much cabin space to play with.
