New Products Flash Sale
Jack Crossfire's blog View Details
Posted by Jack Crossfire | Apr 06, 2009 @ 12:00 PM | 3,026 Views
Finally got a 3D position out of sonar. All those small errors really add up. It's 1ft off in the air. On the ground, it's hopeless. It is 20Hz at least, it's better than GPS, & it's indoors. It would definitely improve with a larger array & 5x faster sampling. What do U expect for $20?

So it's taking 42% of an 800Mhz CPU to do sonar navigation. Sometimes clock drift works & sometimes it doesn't. The triangulation algorithm is the least efficient possible. If the copter clock is ahead of the ground clock, fuggedaboutit. As Kris Kraft would say, U need to start flying it regardless of the imperfections, to know if sonar is completely nuts.

There was once a large book of software anomalies for the space shuttle. The risk & cost of software changes was too high to bother fixing it.

So, in a 10 minute flight, Vika 2 needs to process 55 megabytes of telemetry to stay in the air. In comparison, your GPS vehicle with 14 satellites crunches 1 gigabyte in a 10 minute flight.
Posted by Jack Crossfire | Apr 05, 2009 @ 08:27 PM | 2,764 Views
HEROINESAPIEN

Can't believe Heroinesapien fizzled out right after release the way she did. U people forgot about her within a month of 2008 CES. At least we know she could walk on carpet if properly hacked.

Heroinesapien walking on carpet (2 min 15 sec)


Another note on Heroinesapien: The servos are timed so if they don't reach their desired position in a certain time, they just stop. A little smarter than RC servos which just burn out.


THE LATENCY OF GROUND BASED AUTOPILOT IS

Got the latency figure for ground based autopilot & it's 60ms. It takes 60ms to transmit an event from the copter, to the ground station, & get the response back. So really the feedback is 16Hz & the other 34Hz R redundancy for interference. Got that by comparing transmitted packet numbers with returned packet numbers.

SONAR 4 U

Also, with the increased workload on the groundstation, we're now aligning the sonar clocks to within 21 useconds or 0.27" of distace error. Pretty horrible.

Remember using the Maxbotix to sense altitude? It was killed because the Maxbotix didn't have an accurate enough trigger, was too expensive, the shrouds defeated XY sensing, & U thought U could synthesize pings on the flight computer to save a few milligrams.

Well, the answer is no. Your flight computer doesn't have enough clockcycles to synthesize pings. It can only reach 8khz. It turns out, when 8khz pulses are applied to the transducer leads, current...Continue Reading
Posted by Jack Crossfire | Apr 04, 2009 @ 10:04 PM | 2,765 Views
At least all those laid off Boeing employees have jobs in N. Korea.

Now the headline on CNN:
> The NCAA men's basketball Final Four couldn't come at a better
> time for the city of Detroit.

With a budget of $654.1 billion, your defense department is going to pay most of the cost of new mortgage, SUV programs & that oh so precious NCAA men's basketball final. The prime cuts will be:

airborne laser: gone
Air Force refueling tanker: gone

Our gut reaction is most of the 1 man UAV startups will be gone & the budget is going to focus on increasing the number of tried & true predators & global hawks to replace manned planes. Hummingbird A160, MQ-8B firescout, X-45 UCAV, X-51 waverider: fuggedaboutit.
Posted by Jack Crossfire | Apr 04, 2009 @ 06:06 PM | 2,712 Views
The only thing we need from Canadia is Motor-7mm 1.7Ohm. Can't believe no-one besides Canadia sells a stupid motor. If there was any other place to get it from, or humans were more creative, this story would already be over.

Kris Kraft notes

Kris Kraft thinks like most of the world exept US. Mainly, the rest of the world thinks about doing while US thinks about politics. He wished China landed on the moon tomorrow because it would make U think about something besides Michelle Obama's dress.

He didn't say anything U don't already know from watching the many TV reruns of Apollo footage. He thinks the space shuttle could be economically viable if it wasn't for politics, job losses, constituents, lobbyists, unions, & basically the USA. The shuttle program was required to buy components from every state. Sheesh.

The only reason the shuttle happened was because it was the only reason the Soviets were willing to negotiate in 1 meeting in 1979. It was really Peanut Head's call, but don't bother searching for Jimmy Carter names on the Goog.

Thinks the shuttle should fly with less of the redundant systems functioning, because that's what redundant systems R for. The main engines could be run at lower power, the TPS could be more robust, & the hydrolics could be made electronic. It could have 100 redundant computers with today's technology. Mainly, it should continue evolving like the 60 year old B-52.

Thinks a lunar vehicle should go between low Earth orbit & the moon, & rely on the shuttle to move people between orbit & the ground. The space station should be moved to a 28' inclination with many incremental propellant burns & become the docking station for the lunar vehicle.

Like J. R. Thompson, said the Orion would be just as problematic & expensive as the shuttle, with a fraction of the capability, because it's the management, not the vehicle. But doesn't think Orion is ever going to happen because of the cost of mortgage programs.
Posted by Jack Crossfire | Apr 03, 2009 @ 03:59 AM | 2,844 Views
Vika 3

Deriving position from realtime digital audio processing is really hard, so lets start thinking about actuators & motor mounts for Vika 3.

Building a micro copter out of Canadia parts would cost over $100, so you're going to be building parts from scratch. Canadia charges $15 for a crummy coil of wire. People R mounting the motors with rubber bands on sticks. Aft thrust vectoring is the hard part.

Ground based autopilot then

Originally, no-one knew if ground based autopilot would work. The latency, full duplex bitrate, & interference effects were unknown. Today we know the maximum feedback rate is 55Hz, & there is enough bandwidth. The latency is 1 calculation U need a day off from your boss to do.

http://www.rcgroups.com/forums/showthread.php?t=912482

Ground based autopilot now

When the timing software was added, it brought the maximum sampling rate from 47khz to 40khz per channel. Since no alias frequencies show up at 40khz, U need to run it at 30khz per channel. Now the ground station is only 739kbit. Really U expected it to go to 30khz anyways.
Posted by Jack Crossfire | Apr 02, 2009 @ 01:04 PM | 6,204 Views
He sounds skinnier & more serious than he looks. Says "umm kay" a lot & is very beaurocratic. Probably doesn't trust anything that bleeds for 5 days & doesn't die.

Clean pads don't save money. The time required to move a rocket back to the hanger & fix it costs more than fixing it on the pad. U need to do as much on the pad as possible.

U need the largest mission control possible. U need as many people on the ground as possible to do what doesn't have to be done in space. This may be more important for manned missions.

The space shuttle IMU has to be reset from the ground once a day. It doesn't have star trackers, accelerometers, or magnetometers. If the update has an error, as happened many times, it'll burn up all its fuel & lose radio contact. IMU's have been replaced by GPS everywhere except the shuttle because it wasn't supposed to fly after 2010.

U need a functioning IMU to align the antennas & U need aligned antennas to keep the IMU functioning. The shuttle can't land without ground communication either. Ground communication is a huge failure point.

Now our highlights video of STS-119, since all the other copies of these highlights were blurry, improperly exposed, jerky & unedited.

best of STS 119 (2 min 25 sec)


The modern consumer electronics industry is basically a space program. The gadgets U read about in the news aren't made by single companies anymore. They're just too complicated,...Continue Reading
Posted by Jack Crossfire | Apr 01, 2009 @ 03:29 AM | 2,700 Views
So U want to easily swap between USB & UARTs for easy conversion between a ground based autopilot & an embedded autopilot eh. Well, fuggedaboutit. All the FIFOs, single byte reads, blocking, timed waits, & polling that UARTs did 4 U have to be written manually for USB.

At least U finally got the XBee, 72Mhz, & audio all crammed into a single cable. Try doing 1.1Mbits over an Ardu nacho taco dilla. Feedback frequency is also a bit more stable over USB instead of serial dongles.

To make it fit in the available clockcycles, U ended up with 6 endpoints, with all the IO except the audio directly between the peripherals & the endpoint DMA area. There's no way to do the audio without memcopies.

E: Ad=01(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 64 Ivl=0ms (audio)
E: Ad=02(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms (to xbee)
E: Ad=82(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms (from xbee)
E: Ad=03(O) Atr=02(Bulk) MxPS= 16 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 16 Ivl=0ms (from 72Mhz)

To Xbee had to be big enough for a complete uplink packet, to keep the XBee from splitting it into 2 802.15.4 frames & destroying the full duplex rate. U could have done all this on the latest $1 ARM chip without any optimizations at all of course.

Unfortunately, not enough clockcycles to do 50khz audio & radio on the same chip. It's stuck at 47khz. Theoretically, sonar is optimum at 50 & 30 because these are 10khz away from...Continue Reading
Posted by Jack Crossfire | Mar 31, 2009 @ 12:12 PM | 3,154 Views
He rambled a lot about management styles & project planning. That's what software is for nowadays.

The SSME was tested to destruction. That's why it's never failed, so far. No other part of the shuttle was tested to destruction, so the rest of it has had problems as managers speculate on the lethal conditions.

The turbine blades & the bearings crack in every flight & R reused after cracking. They couldn't get them to stop cracking, so instead of fixing the problem, they tested to destruction to know when the cracks were lethal & told the astronauts they were riding cracked blades.

Unfortunately, it's real expensive to test to destruction. U ever blow up a bag of LiPo's to figure out what their true C rating is?

The A1 test stand has no roof. They can't fix an engine if it's raining. The 1 time they put a roof on it, it trapped pure O2 from a leaky valve & made all the wires on the test stand burst into flames when the engine started.

He thinks NASA should have continued improving & testing the shuttle after 2003 as if it wasn't being phased out. Now there R no more improvements, the experts have left the program, & you're flying extension after extension on a vehicle which is no longer tested.

He thinks NASA emphasized pushing the limit of technology too much & should have derated the performance to increase margin. The shuttle was no more dangerous than any other system, if its performance was reduced.

NASA can keep making new vehicles all it wants & they'll be just as dangerous as the shuttle. By pushing the limits of performance & not testing components to destruction, they'll make Ares-1 just as problematic & expensive.
Posted by Jack Crossfire | Mar 30, 2009 @ 01:48 PM | 2,975 Views
Dreamed Russian Heroine became a rich banker & formed her own olympic swimming program. She hired some coaches & athletes. She was much older, sitting in a chair next to the pool, & her athlete lover swam over.

We figured the program was just a way of providing a constant supply of men to make love with. She still recognised us but was much more interested in her athlete.

In another dream, we joined a startup full of Russian programmers & she came in, yelled & screamed about stalking her. It was on some university in a classroom.

Vacuum tubes forever

Hopefully U all saw this Gizmodo revelation about vacuum tubes.

Electrons on Parade pt 1 - RCA (9 min 31 sec)


U can't blog about sonar without bringing up vacuum tubes. The answer is yes, BYU used vacuum tubes in its recording studio in 1997. More specifically, a pair of tube leveling amplifiers. Vacuum tubes still are the only way to get certain sounds just like a Steinway is the only way to get certain sounds.

So U want to simulate vacuum tubes in software, eh.

The truth about digital audio

Sampled audio at 48khz can't reproduce a 440Hz sound. It can alternate between 440.366972Hz & 436.363636Hz to try to fake it, but it can't do the 440Hz your great great grandparents heard on their LP's. To make discretely sampled audio do every frequency that analog did, it would have to sample millions of Hz at 24 bits. It literally amounts to digitizing the molecular structure of the complete physical tape.

Wouldn't be surprised if no-one in the current generation ever heard true A440.


Kinetic energy busters

The kinetic energy credit card had some more problems. It took -2v to rewind the first mass, so the second mass needed 3v. The 3v mass would finish its movement before the -2v mass rewound. Since each mass movement took less time to complete than the previous one, a new mass would be required for every movement. There was no way to defer kinetic energy repayment.
Posted by Jack Crossfire | Mar 29, 2009 @ 05:32 PM | 3,170 Views
3 years ago, U envisioned the kinetic energy credit card. It accelerated payloads to 17,500mph while deferring the equal & opposite reaction for later. At 17,500mph, it released the payload & then repayed the equal & opposite reaction by returning to Earth & discharging the rest of the debt into the ground.

It used 2 moving masses in real long tubes. 1 moving mass shot aft to accelerate the payload forward. When it reached the end, it reversed direction & another moving mass shot aft with enough velocity to pay back the direction reversal of the first mass + additional payload acceleration. They kept alternating & accelerating exponentially to build up payload velocity.

In reality, it would have used millions of oscillating masses, they would have exceeded the speed of light real fast, & the tubes would have been really really long vacuums, maybe several miles long.

It could work with a ground based vehicle. It would allow the vehicle to travel a short distance without requiring traction.
Posted by Jack Crossfire | Mar 29, 2009 @ 05:06 PM | 3,021 Views
There is no direct servo control via IR on the Heroinesapien. The 1 kid who went through all the trouble of uploading a teardown to the internet didn't label the fricking chips.

U would have to splice 3 wires for each servo to control them manually. U would have to bias the potentiometers without turning on the H-bridge driver. All the leg wires R hard soldered to the board, so U couldn't just make a board with connectors & plug it in.

Walking requires changing the center of gravity by moving the arms & body motor, then moving the leg motors....Continue Reading
Posted by Jack Crossfire | Mar 29, 2009 @ 12:18 AM | 3,197 Views


Automatically add someone famous to the subscribers list of every account. You'll have them falling over themselves with glee, taking their comments seriously, & referring your social network to the world. Gizmodo originally did that.

Make a fake IQ test which always gives rediculously high numbers.

Most importantly, use a strange font that no-one's seen in years.

Sonar busters

Phased array sonar is busted. The ping is too repetitive & the waveforms aren't similar enough for absolute differences or correlations of the waveforms to work. Was hoping correlation could get a hedge from multiple distance readings. It would work if the frequency was super low & the microphones real close together.

It detects phase in a single period nicely. That could be applied to velocity or error correction.

All U can get are independant distance readings from the microphones.


Posted by Jack Crossfire | Mar 28, 2009 @ 03:47 AM | 4,047 Views
Fuggedaboutit it using GPS. If sonar panned out & we could get it up to 20Hz, a VikaCopter swarm would definitely happen someday. It would take precise alternating of pings from 2 separate computers. It would use 1 ground station & a lot of new software.

A swarm can do a lot of things a single vehicle can't. 3 GPS guided vehicles can surround a building & provide UWB positioning for a vehicle inside. 1 vehicle can fly a light while the other one flies a camera. They can refuel each other. They can hand off payloads to eliminate refueling. Most of the money these days goes to mapping obstacles using swarms. They can do other things which R too crazy to mention.

Sonar hell

Aligning 3 channel audio is hard. You're better off sending 3 channels + 1 empty channel & eating the clockcycles. Also not sure of exactly the best way to determine the phase of 3 audio channels.

More shuttle 4 U

Loading up your portable media player with

http://ocw.mit.edu/OcwWeb/Aeronautic...otes/index.htm

& listening to it during 10 hours of traffic every week, U realize the purpose of universities isn't what it was 15 years ago. People R learning everything they need from the internet. They're getting brand recognition from universities.

The MIT degree means they physically sat in a room, were lectured to by the best, & waited on a lot of stupid questions. That's the kind of thing big companies value. So MIT doesn't spend money on calculus &...Continue Reading
Posted by Jack Crossfire | Mar 27, 2009 @ 12:09 PM | 4,097 Views
Yes, when the original Robosapien first came out, we too were blown away by the hype & wanted one. This really was the gadget that put Gizmodo on the map. It was invented by a Los Alamos engineer & he had all these videos of spagetti prototypes & the video was freakish & it was only $100, wow!

Would never buy a male robot or a barbie doll, but we always wanted replicas of Heroine Statues & Russian Heroine left us, so it's time for the Heroinesapien.

Heroinesapien 4 U (0 min 50 sec)


Sadly, she can't do much without PC control. The posing feature is really worthless. There's no position accuracy. The waist servo is too highly geared to pose. She forgets all the poses when power cycled. She can't walk on carpet at all. She has husky african voice sounds. She can't be posed like an action figure. The 11 joints are mechanically coupled to just 5 degrees of freedom. She can't bend over.

Some ideas 4 U Heroinesapien hackers:

Give Heroinesapien the learning & intelligence of an AIBO with PC control.

Recharge the batteries with a head mounted solar panel & intelligent sleep modes.
Posted by Jack Crossfire | Mar 26, 2009 @ 12:43 PM | 3,667 Views
http://ocw.mit.edu/OcwWeb/Aeronautic...otes/index.htm

via a comment on $parkfun .

The shuttle runs at 1Hz during liftoff & 6Hz in orbit. Most electronics R manually shut down in orbit to save fuel. The gyros were originally sampled to only 4 bits because they didn't have enough clockcycles. Full scale range was based on liftoff oscillations, not orbit.

The shuttle doesn't use PID loops because there's not enough fuel to constantly hunt for equilibrium. It uses XY plane feedback. Given a start & end state, the computer looks up the exact required burn time in a table.

The pilot has to manually select lookup tables based on payload, robotic arm position, & docking.

The standalone shuttle is a rigid body while a docked space station & extended robot arm turn it into a flexing body.

They calibrate the tables using very accurate mission simulations in software which accurately predict the center of gravity, moments of inertia, flexing modes, aerodynamics, & noise. On STS-1 they had an unpredicted oscillation during tank separation which almost killed the crew.

Also, most of the computers failed on STS-1 because of floating solder balls.

You're never done optimising a system even after U start flying it.

The space shuttle computers have 100x more memory than VicaCopter's airborn computer.

Everyone taking courses in aerospace is an Israeli or a Russian & they constantly ask stupid questions too. Look. The worst part about college was waiting for the endless stupid questions to get answered & they all were stupid.

Hubble is high maintenance because it flies in the "south atlantic anomaly" which exposes it to severe radiation. The Anomaly is caused by the Earth’s magnetic field, but Americans R going to fix it by raising carbon taxes.

Entire careers were built on guidance, navigation & control in the 70's. Today U buy the systems from China for 5 cents.
Posted by Jack Crossfire | Mar 25, 2009 @ 02:59 AM | 3,160 Views
The answer is no. U don't need a 157khz samplerate to capture 40khz sonar. Through the magic of aliasing, U can sample at 50khz. On a 50khz ADC, the 40khz waveform shows up at 10khz. That's good enough for 2" of accuracy. This trick won't work on a soundcard because those have lowpass filters to reject everything above 20khz. Only bare ADC's.

157khz would be better, but we have to pay your mortgages off.

Libusb does indeed support queueing multiple URB's, so U don't need the dual endpoint trick from 7 blogs ago. Getting a 48Mhz PIC to do 3 transducers at 50khz is not easy. Probably not enough room for the radios.

Now page 2.

Most of our memory of Russian Heroine was from just the first 7 months in 2007. Have very sparse memories of her in 2008. Only saw her 4 times in 2009. On the inside, didn't notice the first 7 months receeding into history. They always felt just around the corner, but on the outside the times were getting rarer & we were missing her a lot more.

Having a car & a big salary let her join a lot more activities & keep busy. Before that point, she was pretty idle & unhappy. Those 2 things basically ended the 7 month honeymoon.

The $50,000,000,000,000 man strikes again.

After astronauts installed the final solar arrays on the space station, Osama made up a great line,

"This is really exciting because we're investing back here on the ground (in) a whole array of solar and other renewable energy projects. And so, to find out you're doing this up at the space station is particularly exciting."

Solar panels powering satellites. What a great renewable energy project.
Posted by Jack Crossfire | Mar 24, 2009 @ 01:11 PM | 3,142 Views
So Russian Heroine left us a month ago, 2 weeks before the 2 year point after she arrived. Don't expect to fall in love anymore. Our heroine worshipping trait began at age 10 & never dematerialized. Never was attracted to winning the bread & thus never had a successful love affair, never dated, & never got emotional support before Russian Heroine.

Thought we'd naturally adjust to patriarchy by age 25 but it never happened. Used to think it was fatal, but times have changed. Nature weeds out all non hackers. If it wasn't possible for humans to survive without emotional support, heroine worshippers wouldn't be born.

The DNA sequence would have been thrown out by a repair protien. Neurons would have evolved to not make the connections. Evolution would have weeded out our capacity to worship heroines if it was really fatal. Heroine worshipping can never perpetuate itself, yet humans can still do it, so it's probably survivable.

Humans forget bad experiences & remember good experiences. Humans follow leaders blindly & enslave themselves. The traits that perpetuated the species survived. If evolution didn't shut down certain brain functions, U humans would tend to absorb all the pain in the world & die. The "feeling all the pain in the world" function got thrown out.

The answer is no. The USB prototype can't get the 471000 samples/sec required by software sonar. It was intended for audible sonar instead of ultrasonic.

The cheapest solution is the PIC24FJ64GB106 or an AT91SAM7S with the whole autopilot on the microprocessor. It's a question of throwing huge amounts of money into a potential disaster or throwing huge amounts of time into proving theories with uneconomical parts.

We prefer using the same parts for everything & most theories blow up, so guess where this is going.
Posted by Jack Crossfire | Mar 23, 2009 @ 12:32 PM | 3,053 Views
Firstly, flying the IDG300's is real hard. They drift too much for any lapse of concentration. Secondly, the software sonar was much better in flight than the Maxbotix reference design. Got 20ft of horizontal range at eye level. They can go up to 30ft at higher altitudes. This is more than the indoor space in the dumpy apartment.

Though the margin can be increased by aiming the receiver at the flight area, we aimed it straight up & the transmitter straight down.

Also, FYI the 3.3Ah super battery went 10min with Ghetto copter.

Finally, the hand soldered uBlox 4 recorded horizontal position in flight but not vertical, so we can't tell if some of the Maxbotix range was vertical or horizontal. It got 5-8 satellites.

With the soldering producing much better results than the breadboard, there R still a few more amplifier tweeks & an increase in the bandwidth before we light up the 2 extra transducers.
Posted by Jack Crossfire | Mar 23, 2009 @ 12:26 AM | 2,977 Views
Make a note of this so U don't forget about it while worshipping your mortgage bailouts.

Ares 1-X has been cancelled. It has a tentative date of July 31 in the unlikely event your government doesn't have to pay out more executive bonuses, but nothing is planned.

nasaspaceflight wrote:
> Orion 4 and the first crew rotation mission to the International
> Space Station (ISS) - is threatening to slip on upcoming PMRs
> (Program Milestone Reviews), with a worst case scenario of 2017.

We originally predicted 2020. Well, given the size of Ken Lewis's bonus requirements, fuggedaboutit. Really Edward Liddy's bonus was the curve ball that downed this turkey.

http://www.nasaspaceflight.com/2009/...al-pad-option/