Posted by Tim Trueman on October 31, 2009 at 5:56pm
We'll be back at our regularily scheduled time next week.If people want to just hang out in the chat at 9PM on Sunday though, you're more than welcome.
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A routine mission to photograph NASA from our day job almost ended in tragedy as our XbeePRO 900's lost contact & the vehicle headed for a roof.The XbeePRO 900's sucked from day 1. The problem seems to be they only do 50mW compared to the 90mW of the original XBee PRO 2.4Ghz. They also spread the signal more omnidirectionally, making for all around weaker reception.900Mhz normally had 10% packet loss while occasionally getting nothing while the 2.4Ghz normally got all packets & occasionally nothing. You could get better reception by rotating the 2.4Ghz wire antenna in azimuth & keeping it parallel. Rotating the 900Mhz wire antenna didn't really do anything. Finally the 900Mhz interfered more with all the other avionics.Upgrading to the 900Mhz equivalent of an XBee PRO for $42 was too good to be true. You need to unload more money in high gain antennas & haul around a tracking mount in addition to your laptop, batteries, transmitter, & video downlink.Best to stick with 2.4Ghz unless you're loaded with government loans or know someone at AIG.So ignored the warning signs during test flights, insisting the 900Mhz hype was true. Sure enough, while scrutinizing video telemetry, saw the vehicle was suddenly pointing the wrong way & was over a roof. Took manual control, but the radio was gone.We don't do RTL because of the chances of an autopilot malfunction sending it into a human or an engine spinning up on the bench. Best to let it drop if the radio dies.
Fortunately it was 1 of the few non government buildings still inhabited & with tenants who could access the roof.It somehow crashed right side up, mostly undamaged & took 4GB of roof photos. Both main & preview cameras captured the action. If it was a pure autonomous flight, leaving us enough bandwidth to monitor the radio, this wouldn't have happened, but had to play with our $50 UART cam.
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Posted by Matt Fisher on October 30, 2009 at 1:06pm
Flight test programs at Edwards Air Force Base and NASA’s Dryden Flight Research Center usually are off-limits to outsiders, but we got a peek at one of its coolest programs, the X-48B, when the Air Force recently threw open the gates for an open house.MORE: http://www.wired.com/autopia/2009/10/x-plane/Read more…
Hobby King released a new platform which might address some of the complaints with easystar - it's larger, has ailerons (and flaps), and plenty of room under the wing for CG neutral payloads.
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Posted by Jordi Muñoz on October 29, 2009 at 8:00pm
Hi there,I been thinking about create a simple and relative ground station to display information in a more useful way.Here is my idea:-Simple reference map, with actual position, distance and heading of the airplane relative to home.-Display waypoints relative to home.-Display information more like an OSD.-In the future click and drag waypoints with real time update (for ardupilot mega).-Overlay photos for offline use.-Multiple Aircrafts?-I would like to create two or three small airplane indicators for pitch, roll and yaw angle in a easy way to read, something like this:
But with real time rotating images,In the meantime you can download and play with the experiment i just did, is in labview 8.2 and 8.6 and also i compiled for Windows:newground.zip.
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Posted by Jordi Muñoz on October 29, 2009 at 6:24pm
You can download ArduPilot 2.4 + Ground Station Beta 2 from here.I didn't get feedback from the community in the unofficial release, so that means that maybe is working fine.. Please tell me if you spot any bug. ;-)What's new:-Altitude hold improved for my EasyStar.-Free running analogs for better performance.-Now compatible with ArduPilot Shield V2.-Minor bugs.- And more...Todo:-Cross Track Error-More testing.-New GroundStation.........Regards.
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Sigh....I am going to give Peter Hollands an award for finding the "juiciest bug" in the released waypoint firmware for the UAV DevBoard. The bug has been fixed, and the firmware has been re-released as version 1.8b.The bug was in the yaw drift gyro compensation calculation. It would only show up for waypoint legs with a heading between 327 degrees and 360 degrees. The result was that the actual heading would slowly vary between 327 and 360 degrees. The symptoms were barely noticeable.The way that Peter discovered the bug was with a combination of ground testing and telemetry, while he was testing out some really nice programs that he wrote for processing telemetry. Peter noticed an anomoly during ground testing for headings between 327 and 360 degrees.Waypoint firmware for the UAV DevBoard is available in both MatrixNav version 1.8 and AileronAssist version 1.8 from the UAV DevBoard home page, with the following features:• Waypoints are 3D.• Location of the points is specified relative to the initialization location of the board.• You have the option of using either cross-track error navigation, or using navigation toward target waypoints.• Arrival at a waypoint is based on the concept of a "finish line". This produces a reliable assessment of arrival, without any chance of loitering.• The primary source of steering is the direction cosine matrix, so steering continues reliably and smoothly even when the GPS loses lock during banked turns.• Rudder-elevator mixing in MatrixNav, based on the values of the direction cosines, prevents loss of altitude during turns.• You can specify more than 1000 waypoints.Just to be clear, the X and Y coordinates of each waypoint are specified with respect to the power up point. It is not specified with respect to the previous waypoint in the list. The X coordinate is the distance, in meters, along the east direction, from the power up point. The Y coordinate is the distance, in meters, along the north direction, from the power up point.Best regards,Bill Premerlani
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Posted by Jason Short on October 28, 2009 at 1:30pm
I was wondering if anyone had done any work on orbiting or managing turns? I prototyped an idea I had last night about orbiting waypoints and realized the same algorithm works for turn prediction.On my autopilot I have running a drift compensation routine that maps the desired location of the plane onto a line connecting the old waypoint and the next waypoint. I simply look ahead 10% farther on that line and steer toward that point instead of the actual waypoint. This helps me regain course when I'm blown off or miss it entirely.In my simulator I added a check to see which side the next WP is -right or left- and I use a vector rotated 90° to the plane bearing to offset the WP to the left or right. This vector also allows me to orbit the target.Here are some diagrams and a shot from the simulator showing the orbit. If anyone has done this before I'd love to hear about how it went. I hope to fly it this weekend if my replacement ESC ships by Friday.
Posted by Faisal Shah on October 28, 2009 at 11:02am
http://www.chrobotics.com/CHR6d.phpFEATURES* IMU weighs less than 1.5 grams* .8" x .7" footprint* Customizable FIR digital filter* TTL UART communication interface* 16-bit ADC resolution* +/- 400 deg/s gyro dynamic range* +/- 3 g accelerometer dynamic rangeSophisticated onboard filtering, simple user-interfaceThe CHR-6d Inertial Measurement Unit includes a customizeable Parks-McClellan windowed FIR filter to process sensor data. The filter is easily customized by sending commands over the TTL UART.Open-source firmware makes the CHR-6d fully customizableWhile the CHR-6d comes ready to use, it can also be reprogrammed for specialized applications. In addition to the UART, four extra GPIO pins are routed out for additional flexibility. At 64 Mhz, the onboard ARM Cortex™ processor is fast enough to handle a wide variety of sensing and control tasks.On their products page (http://chrobotics.com/products.php), they also make mention of this :CHR-9d Inertial Measurement UnitComing soon - the CHR-9 line incorporates rate gyro, accelerometer, and magnetometer data to create a self-contained attitude estimation system.No news yet on pricing, but they said it should be available in Oct 2009.
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Link to "report" [PDF]:http://www.auvsi.org/unmannedscience/newsletter/attachments/140/Barnhard_D.pdfQuote:"In the near future we will see unmanned aircraft systems (UAS) operating in the National Airspace System (NAS) seamlessly with manned aircraft in all classes of airspace. To achieve this airspace integration issues must be solved in a safe expeditious manner. There is much to do by all Stakeholders in the coming dec-ade to realize this end. Approaches to Airspace Integration for UAS are herein discussed with potential solutions and the way forward set forth."Interesting read...desired steps but nothing really concrete yet (but I guess it has to start somewgere)
Read more…3D Robotics
We've wanted to be transparent with the community on our plans for ArduPilot Mega to get feedback, but I fear we've also introduced uncertainty and confusion. Here are some tips and pointers that may help you plan your ArduPilot path.
First, don't expect ArduPilot Mega until well into the new year. Second, it will be considerably more expensive than ArduPilot. Third, it won't necessarily work any better than the current ArduPilot for basic autopilot functions--it's just for people who want two-way telemetry and a more compact installation. Fourth, we'll continue to support the current ArduPilot. These are two different products, for two different customer classes.
We'll also be releasing a product that's for a lower end of the market, an even simpler, cheaper autopilot for inherently stable aircraft (this is a turn-rate limiter autopilot that will outperform the PicoPilot at less than 1/4 the cost). Also Q1.
So think of ArduPilot as a family of products: Entry, General and Pro.
ArduIMU is not part of the ArduPilot line. It's for people who want to integrate an IMU/AHRS into their own project.The IMU in ArduPilot Mega will be custom for that product.
Unless you're really trying to save money, I suggest most people start with the current ArduPilot. It's mature, stable and will be supported as long as we can see. ArduPilot Mega will someday get there, but unless you're willing to deal with our teething pains for the next year, you'll be a lot happier with the current product.
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First, congratualulations to Brian Wolfe, the winner of the second round of the T3 Contest. Now it's time for Round 3.
This round's objective is to break the Stanford team's UAV altitude record of 7,142 feet by doing at least 24 circles with a 300ft climb and descent in each, as shown above. (This won't really beat his official record, because there won't be an official judge there. But you'll get bragging rights, at least).
The winner will have the highest cumulative altitude, but anyone who exceeds 7,142 feet will win a prize.
As usual, you must submit a KML track and video in the comments below. Evidence that fun was had is welcome (and may influence Gary's point assignment blackmagic equation), but is not required.
Deadline is Midnight PST on November 29th.
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Dear Sirs,I am writing to express my disbelief and disappointment that you have issued a cease and desist notice to Sparkfun in respect of their tradename. I am a customer of Sparkfun and have bought their products in relatively large numbers in recent time. I have never at anytime confused their products with yours and...Out of interest I went to my search engine (Yahoo UK & Ireland) and searched for 'SPARC'. The first result was "SPARC - Strategic Promotion of Ageing Research Capacity". Hmmm,I hope I have not inadvertently created a problem for that erstwhile organisation by pointing out their potentially alleged breach of your trademark. Further down the first page of the search were a number of organisations going by the name SPARC. And of course the SPARC they are using is an acronym, just as is the name of your company (derived I believe from Scalable Processor Architecture). That is interesting. So the only similarity between your tradename and that of SparkFun is that the first syllable is sounds the same? Because of course the origins are different. SparkFun is derived from the 'real' word 'spark' and your word 'SPARC' is an acronym - not a 'real' word - of something that does not have anything like the same meaning. A quick search on Yell.com for Spark gave me the following: http://www.yell.com/ucs/UcsSearchAction.do;jsessionid=B9775C9A5B29D4E8835460CFEADA240E?startAt=30&companyName=spark&M=0&searchType=advance&ssm=0&startOoaAt=0&ppcStartAt=45&lastKeyword=Plumbers&pageNum=4I wonder if SparkFun should go after a few of those at some stage? Maybe you might like to consider it yourself.It is interesting that you claim that your SPARC sounds like spark - yes it does, amazing that you are effectively trying to restrict the use of the English language in favour of an acronym....I further notice that your legal representatives have stated categorically that SparkFun supply 'identical goods.' Now here is where you got my attention! I would be so grateful if you could supply me with a list of those goods as I am always on the look out for better priced goods. I have to admit that I did have some problems finding the following goods on your website and I would particulary be interested in your links to the following popular items (do you accept Visa Electron?):VTI SCP1000 pressure sensor breakout board (the Sprakfun is SPI but I would be REALLY interested if you did a TWI version - I think it uses the SCP1000-D11);short lengths of breakaway female headers because SparkFun only do them in strips of 40 and the problem is that when you break apart the section that you need you lose one pin and the end looks pretty grim - especially if you are trying to develop a commercial product (I hope yours are not too identical if you know wnat I mean);ArduPliot - they only supply it in red which to me is a bit aggressive;this one is a bit off the wall I know but do you sell hoodies? I really wanted to get a SparkFun one but as you supply identical products I may be shifting my brand loyalty and of course I am always ready to help promote and identify myself with a worthy product. My problem with SparkFun is that I am XXXL and their tees only go up to a XXL and while I really fancy the wrist belt I am a big guy and am not really sure that it will fit. Maybe your own calalogue will have a greater variety of sizes - or maybe they are identical too? Do your hoodies have SparkFun written on them if they are identical?Anyway, I am really look forward to receiving your list of identical goods so that I can compare, contrast and hopefully get a better deal.Oh yeah, before I forget - your legal advisors are trashing your reputation and that of your holding company - well it's alleged anyway.Regards (allegedly),Mike(PS, don't forget the links and the thing about the tee-shirts - thanks)
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Posted by Jose Julio on October 27, 2009 at 10:50am
Hi all, hola Jordi!. I have made some test flights with a modified arduIMU code in stabilization assist mode with good results. Mi test platform is a small swift II wing (this is not an easy plane for an IMU...). See telemetry video
I have been working on an imu and AP code for some months. I have tested it and fly it and works well on normal conditions. When I see the news from Jordi of the arduIMU (Thanks Bill and Jordi...), I downloaded the code and tested it and adapted it to my hardware (Locosys GPS, Sparkfun 5DOF [old model with IDG300] and a LISY300). It works fine in static tests but have some problems: slow response, vibrations from motor and problems in dynamic conditions. I start to look at the code and I implemented some modifications to improve the results.1) The code is using a free running ADC mode but only use the last ADC reading, so the effective sampling rate is only 50Hz. This generates aliasing problems (in vibration enviroment) becuase the sample rate must be 2x the bandwith of the sensor. In your hardware bandwith of gyros is 88Hz and accels 50Hz so we need a minumun sampling rate of 176Hz and 100Hz. The simpliest solution is using all the ADC readings and make and average. In my Atmega328 at 8Mhz I have about 550Hz samplig rate.Code:volatile uint8_t analog_count[8];...ISR(ADC_vect){...analog_buffer[MuxSel] += (high << 8) | low; // cumulate readings...analog_count[MuxSel]++;MuxSel++;...For read:AN[0] = analog_buffer[0]/analog_count[0];AN[1] = analog_buffer[1]/analog_count[1];... 2) We only need to make a low pass filtering on the accelerometers, because we want the high frequency response of the gyros. This improves the response of the system.3) Because the delay effect of low pass filtering, I think is better to correct the centrifugal force effects on the raw accel data and then apply the low pass filtering.Also I am thinking on adding a term for correct plane accelarations/decelerations on x axis (need some tests):// Correct accelerometer x axis for plane accelerations/decelerations based on GPS speed...if (GPS_Error == 0){acceleration = (GPS_speed - GPS_speed_old) * 5; // dV/dt = dV*Hz (in my case GPS runs at 5Hz)Accel_Vector_unfiltered[0] += Accel_Scale(acceleration); // x axis accel}4) For centrifugal force correction. Accel_Scale affects the two terms:Accel_Vector_unfiltered[1]+=Accel_Scale(GPS_speed*Omega[2]); // accy += GPS_speed(m/s)*gyro_yaw(rad/s)//Accel_Vector_unfiltered[2]-=Accel_Scale(GPS_speed*Omega[1]); // accz -= GPS_speed*gyro_pitch* The old code also works because of Accel_Scale definition but I think this is more clear...5) Manage GPS errors: We can only use GPS info (speed and course) when he have a good GPS signal. If we lost GPS signal we must remember the last speed info (we need this for centrifugal force corrections) and make no drift corrections using course.6) To think...: Adaptative Kp and Ki for roll and pitch. We can trust more on accel data when it´s magnitude is near g value.This are the code modifications: ADC.pdeDCM.pde (note that my sensor configuration is different than arduIMU hardware)On more thing: The execution time of DCM is only 4.25ms on an arduino pro mini atmega328 at 8Mhz!. So there is room for a lot of things on our little machines...I will continue my test flights with this code and post the results...Coments welcome and thanks to Bill and Jordi for share this code and for the porting to arduino...JJ.
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$3 in mass volume, so that has to mean under $20 single quantity.16bit digital output using I2C Interface is nice, 16bit is a good start.Sadly if it's anything like the IDG range it will never compare to "serious" gyros like the AXDRS range. It's a start though.
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I still remember how thrilled I was when we passed 100.... Sometime over the weekend, we passed 6,000 members. We're now doing an average of 15,000 page views a day! We have an average of twice as many visitors at any given time as the #2 UAV community, RC Groups.
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