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Archive for January, 2014
Posted by Jack Crossfire | Jan 31, 2014 @ 03:18 AM | 5,724 Views

It got a new installation of buttons & LEDs. The battery has some cable management which seems to work well. Comparing to the video

PX4Flow micro quad (1 min 16 sec)

from Sep 2013 reveals it's nowhere close to where it was. Not sure why this is. There's still a lot of IMU drift, but it's bearable.
Posted by Jack Crossfire | Jan 29, 2014 @ 10:44 PM | 9,933 Views

The RC car goes to heroic lengths to achieve just bang bang steering.

It doesn't completely stall the motor, despite the motor sucking very high current when at the limit. It uses an ingenious centrifugal clutch.

...Continue Reading
Posted by Jack Crossfire | Jan 29, 2014 @ 06:00 PM | 5,857 Views

The Chinese fartbags once again stick it to the poor people of the world. The blog recalls that the LCD wasn't cracked & there certainly wasn't any of the damage listed. The problem was the touch sensor, which wasn't listed, & discoloration of the backlight, which didn't have to be fixed.

Just because the Chinese are the only people in the world who can make phones & the only ones who can invent things, they treat the rest of the world like snot. The Americans get poorer & the rich move on to the stars. That's how humans have always lived.
Posted by Jack Crossfire | Jan 28, 2014 @ 11:07 PM | 6,000 Views

So the PX4flow issue ended up being the UART overflowing. The floating point conversion must have slowed it way down. IMU drift still seems within limits. There are a few more UART routines to optimize for the higher latency, a few more glitch crashes.

After all that floating point rewriting, DCM conversion, & IMU hacking, the result was still pretty bad. Optical flow is still a sloppy method, especially outside the 1m fixed focus of the PX4flow.

It would scream if it had an autofocus based on the altitude data, but there's still no way to make a long macro lens with autofocus down to a price.
Posted by Jack Crossfire | Jan 28, 2014 @ 03:57 AM | 6,997 Views

Getting the video feed on Qgroundcontrol requires disconnecting the PX4flow from all other power sources except USB. Official Linux support for Qgroundcontrol seems to be gone. It's just Mac & Win, unless you want to make your own port.

The PX4flow is indeed broken. The camera works. The altitude readings work. The flow compensated readings are garbage. Moving it around a lot gets useful flow compensated readings to start showing. It reverts to garbage after a certain amount of time below a certain amount of movement.

The gyros would have to be broken, but no mems gyro has ever died. Some of it could be the UART dropping characters. The raw readings are quite erratic around startup & engine arming time.
Posted by Jack Crossfire | Jan 27, 2014 @ 04:32 AM | 5,939 Views

After a full day, the electronics were transferred to a new airframe with new motors & new propellers. The IMU drift, as it was known, was no more. So the motors should be considered gone after 1 crash.

There was 1 phase in the development where it was spontaneously getting thrusted into the floor by 2 motors going to full throttle. That might have done it.

The autopilot is now non functional. The PX4flow might be damaged. There was another reflex to put the sonar on foam, which probably doesn't work, either.
Posted by Jack Crossfire | Jan 26, 2014 @ 06:39 AM | 6,169 Views

After a 2 day process, an outboard IMU was fabricated.

A magic switch was installed to switch the UART between debug & IMU input. The bootloader started in 115200, then the mane firmware switched to 230400 for the IMU. That supported 1050 full readouts per second.

...Continue Reading
Posted by Jack Crossfire | Jan 23, 2014 @ 02:59 AM | 6,009 Views

Hard mounting the electronics made all 3 axes drift for the 1st time. So the next strategy was to get as many axes stabilized as possible, then use an offboard gyro for the 1 remaning axis.

Returning to nearly the original battery mounting still resulted in drift in 2 axes. Also tried the hardware lowpass filter setting & increasing the full scale range.

That left going back to a very large offboard IMU in a heavily padded case.

Finally added feedback for the rate of the rate gyros that all the commercial quad copters seem to have. They call rate of rate feedback "stabilization P", while the rate feedback is "stabilization I". The feedback for angle & trim are the "self leveling P & I". A total of 4 terms are required.

It didn't have any obvious impact. The weight of the PX4flow is degrading the flight characteristics.
Posted by Jack Crossfire | Jan 21, 2014 @ 09:40 PM | 6,465 Views
It's quite annoying when everyone else in the world has a Turnigy microquad & yours is the only one with an IMU drift issue.

Decoupling the battery from the electronics caused drift in both directions. The only explanation is the battery was preventing drift in its long axis while not affecting drift in its short axis.

The others hard mount their stock KK board with the heavy LCD on the frame & always have the battery underneath.

...Continue Reading
Posted by Jack Crossfire | Jan 21, 2014 @ 12:27 AM | 5,967 Views
The hunt for the IMU drift has been long & fruitless.

There was using higher quality ADXRS gyros, fitted with their own microcontroller.

There was more compliant foam.

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Posted by Jack Crossfire | Jan 20, 2014 @ 09:00 PM | 6,121 Views

A complete home entertainment system for FPV, but with the same old analog NTSC video.

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Posted by Jack Crossfire | Jan 17, 2014 @ 04:30 PM | 6,045 Views
The phone started dying after only 6 months. The back & menu buttons died. Then the bottom of the touch screen died. Suspected salt invasion from days of running.

The phone was indeed invaded by salt.

...Continue Reading
Posted by Jack Crossfire | Jan 16, 2014 @ 11:12 PM | 6,317 Views
So the pondering about cubesats was lame, but now there is a new idea. Get a cubesat to photograph a spy satellite up close. It can't be very far from happening.

The mane spy satellite of interest is USA 224. It's in a sun synchronous polar orbit that passes over Baghdad at noon. It's low enough for a cubesat to reach. It can only be seen from the ground in Australia. It is believed to be a shortened hubble space telescope which can be approximated by chopping off hubble's instrument section.

Another spy satellite worth visiting is USA-223, the largest satellite in orbit.

It has a 100m dish. It's in a geosynchronous orbit over the middle east. A cubesat would have a hard time reaching that orbit.
Posted by Jack Crossfire | Jan 16, 2014 @ 02:16 AM | 6,134 Views
Was hoping Elysium would have some stunning visuals of a space colony, but all you get are 2 hours of Matt Damon bleeding & some lame immigration policy narration. Finally figured out why everyone suddenly got obsessed with immigration policy in 2013, manely the lack of healthcare entitlements to illegal immigrants.

As one who hasn't had any health insurance since 2009 & has only seen people leaving US to obtain healthcare overseas, this story never made any sense, but it is what the media tells us to think. These movies also forget that once the immigrants own all the stuff in Elysium, what do they do about all the citizens who now want their stuff?

The conversion of Jodie Foster & William Fichtner from unemployed astronomers to most evil pair in the universe is complete. Never seen so much evil.

For all the accusations between republicans & democrats, the immigration policy debate is more of a class war than a party debate. The richest 1% want cheaper labor. The poorest 1% want entitlements. The middle class wants to keep their jobs.

The leaders of the system want expanded immigration while the workers under the system want less immigration. The government & the people are at odds, as every attempt at government has been.

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Posted by Jack Crossfire | Jan 14, 2014 @ 08:48 PM | 6,201 Views
Whether to port bits of Arducopter to Marcy 2 or port bits of Marcy 2 to Arducopter has been the mane question. Arducopter is a very large & growing nest of features, with a lot of hype around a few features that might be useful. Porting bits of Arducopter to Marcy 2 has been the only thing that fits into the 2-4 weeks between all up demos.

The additions or at least the hype is getting more frequent, as 3D Robotics has more money to invest in features, but the hardware has remaned the same. Recently, the big ones have been autotune, hybrid mode, inertial navigation, & Kalman filtering.

As with everything nowadays, the marketing for every new feature is in your face & viral, while reality sometimes differs. Actually having a stock arducopter to test with optimal parts is financially prohibitive. $800 + stock RC system + crash repairs is quite a lot by Chinese standards.

The inertial navigation still seems a bit like smoke & mirrors. There hasn't been a side by side test of inertial navigation vs. GPS only. The question is how much new information they can actually get from the same old garbage input.

The autotune feature is potentially useful, conceptually simple, but very time consuming to perfect. It's in 1 small file called auto_tune.pde. It commands a bunch of rolls & pitches to optimize an existing set of tuned attitude hold gains. It doesn't touch heading or position.

Once again, there's no obvious improvement that jumps out....Continue Reading
Posted by Jack Crossfire | Jan 14, 2014 @ 01:51 AM | 6,890 Views
It was decided that the $40 RC car was good enough to justify modifying it as an exercise tool. The mane task is converting the steering to a servo.

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Posted by Jack Crossfire | Jan 09, 2014 @ 11:36 PM | 6,816 Views
7 mile RC car drive (3 min 26 sec)

The gopro died after 6 miles & the car died after 7 miles on a 1.5Ah battery. Its speed was 9m30s/mile until the battery died.

Mounted the camera backwards for the next one.

5 mile RC car drive (3 min 57 sec)
...Continue Reading
Posted by Jack Crossfire | Jan 08, 2014 @ 08:10 PM | 6,013 Views
Ran with the RC car being manually controlled. Keeping it on the narrow urban sidewalks was impossible. After leaving the urban jungle of Rain Ramon, it could start staying on the 15 ft wide trail. After several miles, banging out a straight line became automatic. Its tiny wheels made it erratic on the crumbling parts of the trail. 1 handed driving is still difficult, but better. The controller needs to get smaller.

The gopro naturally died after 6 miles. The RC car went 7 miles on 1.5Ah, then suddenly died & had to be carried 6 miles home. That was way beyond expectations. Thought it would go 1 mile. 6 miles on 1.5Ah should be considered the range. It has a brown out shutoff. A brushless motor should get it up to 9 miles. Its nominal pace was 9m30s.

This system is fast enough to be a pace maker for the slow, long run, but needs more NiMH batteries which are super expensive compared to Lipo. Would only invest further development in a high end brushless system. Those things are expensive, even from Hobbyking. They're $75 - $100 just for the frame.

Don't think the changes are substantial enough to sell a manually controlled, modified RC car as a workout coach. The only differences are the 1 handed control, longer range, & attachments for water.

Making it completely autonomous is pie in the sky, but there might be a way to get it to drive the straight sections or avoid obstacles. A camera which automatically tracks the runner would be something. There's absolutely nothing which can make a timelapse video of an athlete during an entire run, but it can't be far off.


Interesting to note how the speed followed the NiMH discharge curve for 7 miles.

Lion after 6 miles. There's no way to see yourself this far from home besides robot.
Posted by Jack Crossfire | Jan 08, 2014 @ 02:50 AM | 7,720 Views

RC Car Run (2 min 56 sec)

A better battery, proportional steering, variable throttle, autonomous athlete following, & it could be a useful exercise tool. The reality of crossing streets & staying on the path makes the autonomous following hard, but the rise self driving cars gives hope.

It's really crusty. The steering is binary. The speed is binary. Instead of a steering servo, it bangs a motor completely left or right to the stalling point. It can't go backwards.

For someone who never had an RC car before, the amount of mechanics required to perform steering & optimally transfer power to the road is quite amazing. 4 wheeled vehicles are pretty complex & there's no simpler way of doing it.

The 2 wheeled balancing robot eliminates a lot of the complexity, but it still can't achieve the ultimate fluidity in turning that fully articulated front wheels do.

A manually controlled vehicle might be viable for exercise. A vehicle which carried supplies for 30 miles has been on the radar for a while. The quest began to make single handed driving more ergonomical.

...Continue Reading
Posted by Jack Crossfire | Jan 06, 2014 @ 03:24 AM | 6,994 Views

Everyone wants to hack a laser tape measure for aircraft navigation. It would indeed make a cheap, extremely accurate, reliable altimeter.

Today, it's the DLR130. It outputs at 1cm accuracy at 3Hz. You need 10Hz for flight, so maybe there's a way to speed it up.

It's very well constructed.

...Continue Reading