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Jack Crossfire's blog
Posted by Jack Crossfire | Jan 13, 2008 @ 12:40 AM | 3,557 Views
So SheCharger abandonned quick charging, lost her MOSFETS, thermistors, & heatsinks. She now supplies constant 0.05C to 5 D slots & 11 AA slots. No more applications require quick charging NiMH. Her biggest problem was the analog levels changed depending on the number of batteries being charged so she couldn't tell what batteries were connected. Now she charges full time and the LEDs are decorative.

Now thinking of starting the fixed wing phase sooner, since copters R going to have lots of downtime. Components & current prices for the fixed wing phase

Single IDG300 for roll & pitch.                 Free
ADXL330 for gyro drift.                         $35
uBlox for heading, speed & position             Free
XBee communication                              $32
Easystar airframe                               $60
PIC18F                                             Free
Prototyping                                     $20
Motor + ESC                                  Free
Shipping                                        $30

The goal: single chip autopilot to reach high altitude, long duration, long distance, take a picture, & return.
The plan: upgrade PIC bootloader to flash a complete autopilot from the serial port. Single chip autopilot firmware in C. Board bringup before airframe purchase.
Posted by Jack Crossfire | Jan 11, 2008 @ 04:36 PM | 4,093 Views
Looks like Vicacopter II won't arrive this week. Free shipping, U know. That means more focus on SheCharger. In 2005, NiMH was king and we made SheCharger to charge the massive number of batteries required for Trapezoid missions.

Quick charging required using MOSFETS to multiplex thermistor & voltage readings. Now that SheCharger has been marginalized by Lipos, considering abandoning the MOSFET quick charging and just having trickle charge.

She broke down long ago when her MOSFETs died from static discharge and glitches on from noisy battery contacts. The goal is to implement software noise reduction and replace the MOSFETs.

Unfortunately any future Trapezoid missions would use Lipo's, the light pollution from overcrowding makes the observing locations worthless, charging that many cells separately is a real pain, and she consumes $300 of rent every year. So upgrading SheCharger has been debated for a year. It's more of a sentimental upgrade now.
Posted by Jack Crossfire | Jan 10, 2008 @ 01:18 AM | 2,510 Views
The Canon A560 has such fast continuous exposures, U can easily make handheld timelapse movies.

Walking A560 timelapse (0 min 36 sec)

This was just handheld with software stabilization.

The Canon A560 won't run on any less than 3.0V, so threw a heatsink on the 3.3V just in case it felt like powering the A560. That brought the electronics board up to 119.8g and the complete autopilot to 8oz.

One other thing. Watching Nausia inspired us to think more about gliders for after Vicacopter. A glider could probably stay aloft for hours. It couldn't do timelapse movies or take off vertically but it could reach long distances and high altitudes.
Posted by Jack Crossfire | Jan 09, 2008 @ 02:03 AM | 2,625 Views
Before U can fly Vicacopter II, U need to implement collective pitch on the flight computer. Collective pitch makes for a more complicated software. If Vikacopter II doesn't do the job, can get another XBee and build a very simple receiver out of the existing source code.

Also took this moment to replace the LS7805 with a tried & true LM317. The LS7805 was causing +/- 0.2V fluctuations in the analog sensors as it heated up. The LM317 theoretically is more stable in a single flight since resistors don't get hot.

The servos must be installed on the copter to do any meaningful tests.

Meanwhile, there's no way this board can power the Canon A560. Probably time to start looking at Buck converters for all these power supplies.
Posted by Jack Crossfire | Jan 08, 2008 @ 12:10 AM | 2,450 Views
The Canon TX1 replacement arrived after 1 week. $400 cheaper but has everything except HD and what video quality it has isn't much worse than TX1 HD. Most importantly, it has a full frame shutter & goes to 1/2000 in ISO400. No more wavy lines and probably no more vibration blur for the stills.
Posted by Jack Crossfire | Jan 05, 2008 @ 06:11 AM | 2,472 Views
The Jesus monitor finally arrived after 1.5 years on the upgrade manifest. Free credit & expectations of future inflation made it possible. It almost displays half our camera resolution. No dead pixels observed so far.

XVideo doesn't work at all for 1920x1080 on the old Quadro FX 4000. You have to force the driver to use OpenGL instead of overlay by hogging the overlay in some bogus program. Did this a long time ago and forgot about it.

Win 2000 is a disaster of course. It only does 1280x800 and after our attempt to upgrade drivers, Orbiter crashes completely.

1080i sux when fullscreen. 480p & 720p R golden. Despite the Windows fiasco, we use Linux 99% of the time and on Linux it screams.

Gootube videos look pretty small on the Jesus monitor. The dual Dells had a larger surface area but less useful resolution. Colors R way too saturated.

BTW, it came with 2 6ft DVI cables so the 2 we ordered R paperweights.

Note the last NVidia driver to support shaders with the Quadro FX4000 was 8762.
Posted by Jack Crossfire | Jan 04, 2008 @ 03:43 AM | 2,441 Views
Hopefully rchover will do a better job than helihobby. While lying awake for 6 hours in bed due to copter withdrawal, thought up some more inertial navigation ideas.

Notice in every professional UAV video how solid the tail is. The tail on the Corona, like the Trex the way we're going to fly it, was real loose. That probably destroyed the navigation quaternion.

In fact, combining big gyro drift + big wobble probably makes quaternions fall over, so now we're integrating the gyros directly on their axes. Many fixed wing autopilots are very successful like this.

With our favorite telemetry, it seems to cut drift. Least squares estimation is also showing signs of life.

Next, there's subtracting GPS velocity straight out of Euler angles. Most of the time, U can see the pitch angle try to jump back in line for every GPS update.

More of your favorite telemetry (0 min 59 sec)

This is not chromakeyed anymore. The HUD & aerial video are stacked in Java. So far Java really sux at video textures.
Posted by Jack Crossfire | Jan 03, 2008 @ 01:50 PM | 1,959 Views
30min flight time

logo 10
20min flight time
1150 mm rotor diameter
500 mm blades

logo 500
7 min flight time using 22.2V 5Ah
1150 mm rotor diameter
500mm blades

Looks flimsier than the Trex but longer flight time.
18min of flying on 14V 4.2Ah
950mm rotor diameter

9min flight time on 18V 3.2Ah
425mm blades
970mm rotor diameter

trex 450
18 min flight time using 11.1V 2.1Ah 2000rpm

So without the Corona, flight times R 2 short. The only way to do it now is the Saudi Arabian juice.

Can't afford a 500 size anymore.

The boss ate our paychecks to pay off his mortgage.

It's cheaper to make lighter electronics than buy bigger batteries.

The 450 has 98% of the Corona's blade size.

Don't anticipate increased value from long flights for another year.

We fly just about every day. Whatever comes now is going to desintegrate in a year.

In any case, the Waypoint Mode switch must become Engine Mode. Engine cutoff & spool up to flight speed. The flight computer needs CCPM mixing & a 5th servo header.
Posted by Jack Crossfire | Jan 02, 2008 @ 05:15 PM | 2,090 Views
Well, it's probably going to be the Trex 500. The Trex 500 was very popular last November on social networks but sold nowhere. Then it suddenly disappeared.

The 500 is probably the largest U can fly in Calif* without paying big bucks and driving 300 miles. The extra space for the TRex 600's is needed for the illegal immigrants.

A Trex 450 would require drastically reduced electronics weight, would definitely not move an HD cam, but would be the most convenient.
Posted by Jack Crossfire | Jan 02, 2008 @ 03:18 AM | 2,458 Views
Well, we're probably not going to spend any more time on HD video from space, but we will have a 7.2oz still camera to mount. With the autopilot, it's 14.7oz of payload. The Trex 450 may not have enough power to do the job even though it uses the same motor & battery as the Corona.

The Trex 500 has 4x the battery cost. In 2006 the 22.2V 4Ah battery was $170. In 2007 it was $230. Guess what it's going to be in 2008.

rchover.com: trex 450SE CF + motor + ESC for $230

Autopilot weight:

Payloads of different copters:

What's probably going to happen is we're going to have a fixed wing UAV & a rotor wing UAV eventually. Fixed wings can take U far and high from the ground station for long periods of time, but they require special programming to handle constant turning. Copters can get U stationary timelapse movies near the ground station, but they require special programming.
Posted by Jack Crossfire | Jan 01, 2008 @ 09:10 PM | 2,504 Views
Discovered the tail rotor hub was cracked, the hard way. That explains the recent yaw control losses. Unfortunately this part is no longer available.

So it's time for a new airframe. The Corona was the last copter which could fly for 30 minutes on a battery charge but it paid for it in maneuverability. Economics dictate shorter flight times and better maneuverability in the new copters.

Looks like U can choose either short flight time + less stability on a Trex 450 or extremely short flight time + better stability on a Trex 600.
Posted by Jack Crossfire | Jan 01, 2008 @ 04:23 AM | 1,952 Views
Simulated the XMas flight recording again with the 14 state Kalman filter just for a sanity check. The Kalman didn't do much better than the algebraic methods even though it probably did slightly better. That flight recording contains a lot of horizontal acceleration.

HUD + video + Kalman filter (0 min 58 sec)

Eventually made an algorithm where the least squares approximation of recent drift rate was subtracted out of the latest gyro rates. Couldn't get the yaw drift to work but there wasn't any huge advantage with that method either way. Simplicity still seems golden.

There's probably a tradeoff between a larger copter or DGPS.

Now a summary of 2007.

2007 was pretty rough. Food got 50% more expensive. Rent got 10% more expensive. Electronic parts got 25% more expensive. Fell in love again. Lost 401k, vacation benefits, and 10% of our income. Copter autopilot wasn't as easy as expected. Our cash lost all of its value as far as mortgages are concerned. No good songs came out. No new HDTV movies were on broadcast TV.

The worst seems to be less and less new stuff. There's less original artwork, less original music, less original technology, but more copies of it.
Posted by Jack Crossfire | Dec 31, 2007 @ 02:47 AM | 2,625 Views
So the next best thing to a Kalman filter is a least squares approximation of all IMU results. Instead of averaging 99 gyro steps + 1 accel result, you feed 99 gyro steps and 1 accelerometer result to the least squares equation and it spits out the best estimate of the true current state.

BTW, Gumstix showed the 600Mhz board in stock for the first time since it went on sale a year ago.
Posted by Jack Crossfire | Dec 29, 2007 @ 08:01 PM | 2,835 Views
> light rain...rain....rain...very
> wet pattern from Thursday through Sunday
> with progressively wetter systems...
> hazardous weather outlook...

Have new techniques to waterproof Vicacopter using painter's drop cloth.

Video AHRS tests gave 2 conclusions:

Need more clockcycles to run a 14 state Kalman filter or need a better AHRS algorithm to use the existing clockcycles.

Need a better camera to get higher framerates.

Suspect the 14 state Kalman filter worked better than the 7 state because it accumulated history in the velocity stores. Another idea is to predict future drift from historic data.

One other thing. Amazon's touch pad finally died so a new laptop is back on the budget.

Now a word from our sponsor.

When Earth is not enough. (0 min 50 sec)

Posted by Jack Crossfire | Dec 28, 2007 @ 12:05 PM | 2,711 Views
Simulated another flight recording with HUD, video, & moving map. The idea is to find any evidence of GPS lag. Looks like the Aiptek does 8fps in HQ mode and 4.25 in low quality mode. The AHRS is still pretty awful. This was the uBlox, dynamic model 6, 1Hz.

HUD + video + moving map (0 min 58 sec)

Posted by Jack Crossfire | Dec 27, 2007 @ 06:29 PM | 2,696 Views
Finally have a way to plot flight recordings on a moving map. The uBlox autopilot tests are replayed. This was dynamic model 6, 4Hz. Underdamped oscillation clearly visible. Can't verify the GPS accuracy although it seems to lag too much for 4Hz to be useful. Time is compressed 3x.

Autopilot test on moving map (0 min 39 sec)

And this was dynamic model 5, 1Hz. Time is compressed 5x.

...Continue Reading
Posted by Jack Crossfire | Dec 26, 2007 @ 12:50 PM | 3,213 Views
2 Pedestrian - same as 3 Automotive

5 Airborn(e) <1g acceleration - increased delay

The answer is no. The dynamic model settings didn't do much except maybe add delay. The goal with the uBlox was to increase wind resistance but everything besides DGPS is still gravy. So we fought the uBlox for 1 month. 4Hz wasn't really there without DGPS. Don't want to devote that huge amount of space and weight to something which doesn't make much difference.

Well the video overlay HUD showed a serious influence of acceleration on AHRS and it leads back to better GPS to take it out.
Posted by Jack Crossfire | Dec 25, 2007 @ 10:24 PM | 2,994 Views
On the first sunny XMas in many years, finally got HUD overlays from the flight recordings. With every flight parameter + video stored on flash, we can simulate a ground station in the dumpy apartment.

It's a painstaking process, rendering the HUD & synchronizing it to the video. Just needs a few hours to capture the OpenGL output over AGP. Times like these make U wish U just wrote it in C using software graphics + YUV overlay. Overlaying on video this way is very fast. May never draw 3D graphics or run this in Windows.

HUD & video for XMas (1 min 39 sec)

Can finally see how bad the AHRS is.

Going through each uBlox model 1 battery at a time.

1 Stationary - no velocity readings
3 Automotive - noisy data
6 Airborne with <2g Acceleration - longer delay
Posted by Jack Crossfire | Dec 25, 2007 @ 05:51 AM | 3,400 Views
* 1 Stationary
* 2 Pedestrian
* 3 Automotive
* 4 Sea
* 5 Airborne with <1g Acceleration
* 6 Airborne with <2g Acceleration
* 7 Airborne with <4g Acceleration

It defaulted to "Automotive", so now we put it on "Airborne with <2g Acceleration". The logic seems to be more lowpass filtering the higher U go. Suspect the most sensitive model is "stationary" and the least sensitive model is "Airborne with <4g Acceleration".

Either way, high wind & rain will keep away meaningful tests for the rest of the year.

Got some good news. The bogus climb rates from the uBlox were actually a bug in the simulator. It was reading heading as climb rate, hence the range of -3.14 - 3.14. Also, the uBlox is randomly ignoring configuration lines, so it often generates garbage NMEA sentences. Climb rate is now in the meaningful range, if not actually useful.

XBee is paying off in this wind. Had 1 save which wouldn't have been possible on 72Mhz.

Well, got our first autonomous video from the Aiptek. Besides tons of manual altitude nudges, it actually maintained horizontal control in 5mph wind. The uBlox definitely has less delay.

Got 100 lousy seconds of video. Only hand stabilized 35 seconds for the viewers at home. The rolling shutter was in attendance.

Aiptek video in auto hover (0 min 36 sec)

Need a tiny camera with a real fast, manual shutter speed + full frame shutter. Next year's cameras R going to be 20% more expensive than last year's.
Posted by Jack Crossfire | Dec 24, 2007 @ 03:58 AM | 3,119 Views
Well, if U plot acceleration vs. attitude U don't get any correlation. The secret is still locked up in the neural network.

After more test flights in cyclic -> attitude mode, it looks like 4Hz without DGPS doesn't buy much. Attitude hold is also sensitive to wind. If 4Hz doesn't come through, we're dropping a few grams and going back to the EM406.

Cyclic -> attitude mode with hard coded angles is so stable it's tempting to just live on that. Can fly through trees in ways no IR stabilizer ever dreamed of.

The search for GPS noise continues. Put the antenna out from under the blades to measure blade interference. Put her on the ground and cycled the throttle from 0 to light on the skids to measure vibration effects. Got no obvious interference.

One thing is 4 sure. There are no blogs discussing DGPS experiences. Maybe Web 3.0. Have 1 more scenario with 4Hz before it's time to think about DGPS.

The latest batteries are now down to 13min of flying. The first batch was retired when it hit 8 minutes of flying. http://www.rcgroups.com/forums/attac...mentid=1389849 As recently as http://www.rcgroups.com/forums/showthread.php?t=750660 the current batch was doing 20 min.