Finally, a stable(ish) flight! On Sunday 8th, the UAV finally flew in a more or less stable flight in the AUTO1 position. This essentially means that the UAV controls attitude and takes directional input from the radio. The UAV interprets the RC signal and decides on the relevant bank and pitch angles. In the case of the testing this weekend, it was noted that the maximum bank and pitch angles were not sufficient to have full control of the plane. Additionally some roll oscillation was noted although given that the gyro is presently disconnected, this is not unexpected.
One significant problem came to light with this flight and that was lack of telemetry. Even thought the antenna positioning was identical to the last flight, very few data packets were exchanged with the aircraft while in flight. This is being investigated, but is likely to require a more powerful ground antenna.
Next steps are to repeat the flight with improved reception so that good data can be gathered, then to test and calibrate the attitude response of the plane using the HSI.
Once responsive flight is acheived in AUTO1, the Gyro can be re-integrated and finally, AUTO2 flight with a simple ‘Circle Home’ Mission can be attempted.
The attitude problem was discovered to be a fundamental mistake when setting up the airframe file which caused teh aicraft to believe it was upsidedown.
It’s been a long time since an update on the UAV project has been forthcoming, so I thought it worth a quick post with progress.
The RC radio is now re-modified so that operation of the mode switch is on the left. I fly mode 2 and it was not the smartest descision to put the mode switch over on the right of the radio.
Test flights have shown that during the brief forays into AUTO1 (stabilised manual flight) showed a small roll oscillation and a violent nose down pitch. this issue is ongoing and is the cause of much head scratching. Telemetry data seems to show that the AHI is in a neutral position before the switch is flicked, so it’s most odd that the plane immediatly dives towards the ground. I suspect the users forum will yield suggestions.
The airframe has around six flights of ten minutes each to its name now and although some improvements have been made, the plane generally flies very well. The only mishaps have been related to the AUTO1 attempts and although these have involved close shaves, the plane is still in great shape. Aircraft now shown to fly equally well on 2 cell or 3 cell LIPO. Normal flight probably will be on 3 Cell LIPO to maximise flight time. 3 Cell pack does increase AUW and consequently approach and landind speed. Ideal prop is 8×6 and this gives good throttle response and very quiet flight.
A recent update of the GUI software has bought a massive performance improvement in the ground segment aspects. It’s not known what has triggered the improvement, simply that it runs very well indeed now. Additional GUI features will be tested over the next few weeks.
Photos of the progress are on the gallery, which is here.
Yes, you heard it right. Researchers in Switzerland have developed some attacks targetted at capturing the Radio Frequency emmissions from keyboards and using the captured RF data to work out what keys the user pressed.
Note that this attack is not against wireless keyboards, but is actually aimed at those USB and PS2 keyboards which we all use every day. Notebooks with built in keyboards are just as easily sniffed too, so there is no obvious escape from this problem.
The heart of the vulnerability is that keyboards are built so cheaply that they have absolutley no Radio Frequency sheilding at all and picking up some form of radio signal from just about any keyboard is an almost trivial excercise.
What is not trivial of course is the decoding of that signal to rebuild the users keypresses. Nevertheless, the team from the Security and Cryptography Laboratory (LASEC) in Lausanne, Switzerland have developed four similar attacks and have found that of the 11 keyboards they extensivly tested, all were suseptible to their eavedropping methods.
The key point here is that it's now pretty much mandatory to use one time passwords if you truly want to be secure.
Read more about the attackes here.
The RC radio is now modified so that it has a three position switch for MANUAL\AUTO1\AUTO2 mode selection. This works fine although ideally the switch should be mounted on the left of the radio and not the right. Full Radio (RC) range check carried out and an initial test flight showed good telemetry data. Photos of the radio mod ar on the gallery, which is here. Full radio (modem) range tests carried out and good signal recieved at 250 Meters using standard antennas.
GCS tested on Mains inverter powers from car battery. GCS voltage converter added for video goggles.
Initial flight test carried out. One 10 minute flight proved the airframe working fine. Chosen Motor/Prop combination giving reasonable
performance on 2 cel LIPO. 3 brief attempts at AUTO1 deemed failures. Each time AUTO1 flight was attempted, the airframe rolled violently. Further ground tuning underway.
The GCS is online and the airframe talks over the air to the airframe. The airframe is now complete with all components mounted. Initial tuning of the airframe file commenced involving checking the servo and sensor polarity. Changed the motor in the airframe to a unit with a bit more oomph.
The two comms channels between the GCS and the UAV were established today. The first of these, the wired USB connection used to flash the flight plan was tested after making up the Pico blade lead. The default funjet airframe file was then modified to approximately match the aircraft and the gcs successfully flashed the airframe. Proper progress! The Project gallery is here
The second part the air to ground link was also completed today. The MaxStream USB dev board arrived today, so I was able to configure the MaxStream Xbee Pro units. The units required a firmware flash up to the latest release and the bit rate set to a sensible 57600bps as well as enabling the MaxStream API, which is used to make the communications channel more resilient. After the UAV end was removed from the USB development board and plugged into the UAV, it worked just fine. Not surprisingly, a further airframe flash was required to get the MaxStream and UART parameters correct in the airframe.
Once this was completed, I started the GCS and was most hearetened to see the Airframe messages coming in.
The next task is to get the GPS working and start installing the IR Sensors
UAV Integration work well underway
The Multiplex Funjet based airframe is essentially complete and the modifications necessary to permit the easy installation and removal of the turtle deck are complete. Motor\speed controller are fitted and the servo leads all now terminate in Molex PicoBlade connectors.
Integration work is now well underway and last night the Tiny 2.1 powered aircraft booted for the first time. The servos immediately chattered themselves crazy. Without the manual radio element, the UAV falls into a default mode of autonomous control. Not ideal when the craft is sitting on the bench!
IR sensors are connected and the Gyro will follow soon along with the radio modem and the USB loader cable. The Project gallery is here.
So we all know that books last a long while right? How about its modern equivalent the CD, DVD or Hard disc? Most of us commit a larg part of our life to digital storage these days and don't even spare a thought for how long this digital memory will last. In the case of hard discs, 5 years might be your limit.
This then is the classic problem with digital storage – longevity. All other problems vanish into insignificance when considering the persistence of storage.
Our current best hope is optical media, the best of which are believed to be good for around 50 years. (interesting to think that our CD and DVD collections are more temporary than we are!)
Recently, a team from University of California Santa Cruz have come up with a system called Pergamum which uses regular hard drives to store data for a projected 1000 years. The system, called Pergamum, uses a large number of inexpensive discs, most of which are spun down. Persistence is created by using multiple slow sync mirrors & stripes.
Clever caching and an even cleverer data distribution protocol ensures that data reads, writes, rebuilds and other operations make the least demand possible on the hardware whilst continuing to be power efficient.
As an example, it's estimated that a 10Petabyte system would consume only around £20 of power per year including HVAC requirements and would be capcble of maintaining that 10PB for arount 1000 years before a data loss occurred. Pretty good methinks!
More on the announcement in this tgdaily article.
Have you ever had to make one of those calls that you wish you could record but locating the voice recording feature on your mobile or answering machine is too hard or you can’t then get the finished recording into a useable format? This seems to happen to me about once a month.
Recently I discovered a service which makes the process of call recording extremely painless. After registering you are given a phone number, access code and a pin. After dialling these in easy succession, you get…. A dial tone. Any subsequent calls you make are recorded and the subsequent call recording is either emailed to you or is available for collection at the portal site. Making multiple calls is easy as the ‘#’ acts as a break-in code to tell the system you want to make another call.
In pay-as-you go mode the process uses a premium rate access number and you simply pay by the minute for the call to the access number. The onward part of the call is not charged back to you.
The service has other offerings suitable for more regular users and also features ideal for small businesses who need to regularly record outgoing calls to customers.
Additionally, it’s possible to have your own phone number for the service which then does not require the use of the access code and pin. This also allows you to record incoming calls as you can set the service up to call you on receipt of a call.
All in all, this is a really nifty service. Check it out at http://www.recordmyphonecall.co.uk/
The problem surrounds Amazons choice to let merchants pick their own shipping costs and the poor way in which Amazon makes those charges visible to the customer.
In essence, when you search for a product and Amazon returns the result, you never see the P&P charges that will be applied.
The important point here is that unlike eBay, who show P&P charges right on screen with the search results, it’s impossible to compare suppliers shipping costs on Amazon.
Try this for yourself: Go to Amazon and try to buy a 1 gig Micro SD card. Attempt to predict how much you will pay based on the returned results. You can’t because the merchants are all dropping the product price and pumping the P&P cost to such an extent that on all the first few pages of results, the P&P cost will double the price you pay. Worse is that you can’t even find out what the shipping price will be.
The end effect of this problem is that it’s nit possible to trust any purchase on the Amazon Store. TurboTas advice is to go use eBay so that you can see upfront how much you will pay.