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Archive for September, 2015
Posted by Jack Crossfire | Sep 27, 2015 @ 09:19 PM | 7,283 Views
It was a long time coming, but after nearly a year & probably no more than 100 miles, the brushed motor was done. Finding the right motor was quite an ordeal. Either all ground vehicles use the same size motor or the bolt holes are in standard positions. There is no data for the bolt holes, only random posts. An obscure post recommended the Tacon 2400kV & it was the cheapest.

After converting the computer from direct H bridge driving to 50Hz PWM, the RPM constants all stayed the same. Drove it 6.8 miles at 5mph on 3S, consuming 1928mAh. The brushed motor used 3518 mAh to go 8.5 miles, so a 31% efficiency gain. Considering the brushless motor is 90% efficient & the brushed motor is 50% efficient, it was a very good translation of motor gains to mileage. The transmission didn't contribute a lot of power loss. It has a good chance of doing a full 13.1 miles on under 4Ah.

Starting was identical to the brushed motor. It didn't look anything like the banging of an AC electric train.
Posted by Jack Crossfire | Sep 26, 2015 @ 01:12 AM | 6,272 Views
Previously, the best result came from the RALPH algorithm. After nearly a year of intermittent ideas & dead end Goog searches, an algorithm emerged which made RALPH look utterly terrible. The idea came from chroma keying, but unlike normal chroma keying, this was a super chroma key.

The super chroma key worked like a magic wand, but instead of cutting off when pixels deviated away from the color key, it learned new color keys based on where the previous mask was. It differentiated between good & bad candidates for new color keys. Then it did an old fashioned greatest edge detection to find the edges of the path. The edge detection eliminated many false areas which didn't belong to the path.

While far from perfect, the super chroma key was extremely robust when tested against very shaded sections. Most sections which weren't heavily obscured by shadows were bulletproof. It could detect both sides of the path, between which a center line could be drawn & the rover programmed to drive just on the right of the center line.

It only needed 640x480 video. Processing is extremely slow. It could be some time before the super chroma key is fast enough for a test drive.

Path detection with super chroma key (0 min 58 sec)

Posted by Jack Crossfire | Sep 25, 2015 @ 12:19 AM | 5,157 Views
Lions were never crazy about basic inorganic chemistry, but propellant densification is the latest thing, like any improvement in rocketry, a major event only happening once in a lifetime. Like ion engines, it was something that spent most of our lives in science fiction, taken up & put away through the years. There's no record of it ever going beyond testing. SpaceX did yet another test, with plans to actually use it, someday.

At least the oxygen side will be refrigerated to 1 deg above the point at which it becomes a solid, providing a 7% increase in the amount of fluid mass in the same volume. Someday, maybe the kerosine side will be densified. It has the same effect as fitting a bigger rocket in a smaller space. It doesn't increase the efficiency or the thrust.
Posted by Jack Crossfire | Sep 20, 2015 @ 10:31 PM | 5,980 Views
The decision was made to convert the lunchbox to brushless. None of the flying ESC's in the apartment could support reverse, so it was time for a SimonK flashing of a Supersimple 30A. None of the blog posts about Arduino programming contained the pinout used to program the last ESC, so here it is:

black - ground
- sck pin 13
- miso pin 12
- mosi pin 11
- SS pin 10

The key parameter for reverse mode was RC_PULS_REVERSE in tgy.asm

Then came make tp_8khz.hex to generate a high efficiency 8khz target. Then came running arduino to install the Arduino ISP sketch. Then finally came the avrdude command:

/root/arduino-1.6.0/hardware/tools/avr/bin/avrdude -C/root/arduino-1.6.0/hardware/tools/avr/etc/avrdude.conf -v -e -patmega8 -cstk500v1 -P/dev/ttyACM0 -b19200 -Uflash:w:tp_8khz.hex:i -Ulock:w:0x0F:m

Then came the dreaded stk500_recv(): programmer is not responding

It erased successfully, read the device ID, but wouldn't take the program. There was no evidence of the chip being fried besides reset being 3.8V instead of 5V. A power test showed it was indeed erased. It was a brick. Fortunately, no-one buys just 1 Hobbyking ESC. It may have to be run without reverse.

According to the range test, it takes 2.5A at 12V to go 6mph. It was a major investment to make the TBLE-02s precise enough. Another stock ESC probably won't be precise enough.

A useful command to erase the mega8:

/root/arduino-1.6.0/hardware/tools/avr/bin/avrdude -C/root/arduino-1.6.0/hardware/tools/...Continue Reading
Posted by Jack Crossfire | Sep 19, 2015 @ 03:08 PM | 6,154 Views
Drove an uneventful 3.9 miles on slight uphill pavement. After .35 miles of ascending the dirt, the motor overheated & stalled erratically. Then after .35 miles of descending, the transmission fell apart. Had to walk 3.6 miles home with the truck. The smell of baking cow maneur wafted. It took 3600mAh to go just 4.5 miles at 5mph, so the motor is probably near its end of life.

It's quite clear a brushless motor is required for any attempt at the ridge trail. It's going to take a new control system to generate the different PWM control. A method of threadlocking which doesn't crack plastic is also required.

RC cars must either always operate near the ragged edge of failure or going continuously uphill for 1.5 miles is way beyond the normal regime.
Posted by Jack Crossfire | Sep 17, 2015 @ 11:09 PM | 5,812 Views
The haze of the atmosphere & the rise of the mountains above the horizon sell it, like a miniature Earth made of solid nitrogen. It was a miracle of a lucky shot, taken in total silence, as a completely silent world quickly passed below, 4.6 billion miles from the nearest human.

It could have just as easily been a featureless plain. There was no way to redirect the camera because of something interesting or plan for mountains to be in the shot. Only 1 brief flyby in 60 years of spaceflight was the limit of human capability.
Posted by Jack Crossfire | Sep 15, 2015 @ 11:26 PM | 5,905 Views
A simple surface classifier using variance didn't look any different than any other method. Among basic classifiers for surfaces, there's also comparing high frequency energy. Neural networks fall over when given data outside their training database. When looking at 16x16 blocks without the benefit of anything besides edges, it's hard to differentiate between materials.

Another idea for using multiple chromakey colors appeared. Regardless of the lighting conditions, the path has only 2 colors: the sunlit color & the shaded color. The trick is identifying color & threshold.
Posted by Jack Crossfire | Sep 14, 2015 @ 01:27 AM | 5,924 Views
Interesting comparison between the same window size from the 640x480 webcam & the 4k 'pro. That makes the idea of surface detection seem more practical. Unfortunately, a practical system would have to get by with a crummy webcam. It would have to use some kind of still photo mode that could go higher than 1080p.
Posted by Jack Crossfire | Sep 12, 2015 @ 11:05 PM | 5,811 Views
There was a theory that texture matching could be a better path detector, but it would require much higher resolution. Recorded 7 miles of 4k. Then the battery died. Did it at higher speed than the range test, with extra cargo. That's the only explanation. The battery only took 4444mAh, so it's lost a lot of capacity.

After walking the final 1.25 miles, finally viewed the footage.

The nearest part of the image had well defined differences between path & dirt.

Edge detecting makes it resistant to shadows, still leaving a well defined boundary. It would merely need to compare the amount of noise to find the path.

...Continue Reading
Posted by Jack Crossfire | Sep 09, 2015 @ 11:24 PM | 5,918 Views
10mph in slow motion (5 min 50 sec)

Another 95F outing yielded the 1st slow motion from truck cam. It was truck cam which revealed a lot of pectoralis flexing at a specific point in leg movement. It only happens during high speed.
Posted by Jack Crossfire | Sep 08, 2015 @ 11:30 PM | 6,355 Views
It was a really brutal RC truck drive in the 95F heat, set to 10 min/mile. Got cramps, nauseous, & dehydrated. The 1st charge with the accucell revealed it could probably go 12 miles on 5Ah. Consuming constant power instead of constant current would give slightly less range for the last 2 Ah.

The accucell uses the main power leads to measure voltage, so it measures slightly above the voltage from the balancing leads. The resistance in the balancing leads doesn't seem to impair it, though it could use a test to see how much current is going through the balancing leads.

The passive matrix display brings back memories of the very 1st laptops, 30 years ago. That was as good as it got.
Posted by Jack Crossfire | Sep 07, 2015 @ 06:41 PM | 5,702 Views
Not sure RC trucks were designed for this kind of distance off road, but by now, ground vehicles had gone hundreds of miles on pavement without issue.

6 mile offroad drive (12 min 24 sec)

Had to program for 9min/mile to get 10min/mile. Steering was quite manual on dirt. A wheel fell off when going in reverse at the end, but otherwise it did the business.

According to the internet, the reservoir was at 46% of capacity.

...Continue Reading
Posted by Jack Crossfire | Sep 07, 2015 @ 05:07 PM | 5,484 Views

So after 2 years, it was finally time to break out the Accucell 8150. It had the coveted capacity guage, very important for measuring the total range of a battery. It was always assumed it couldn't charge less than 3S because it only had balancing pins for 3S & the crummy Passport charger wouldn't charge unless the battery was plugged into the balancing pins.

It turned out the internet said it would charge all the way down to 1S & it didn't require the balancing pins to be plugged in. Balancing was optional. It would balance 2S by plugging the 1st 2 pins into any of the balancing headers. The ideal use was in balancing mode, so the next problem was moving the balancing header closer to the charge header & providing a pin strip which could plug into any battery.

Opening it the way the internet recommended broke 1 of the tact buttons. Half the circuit was dedicated to just balancing.

The balancing pins were all in parallel.

...Continue Reading
Posted by Jack Crossfire | Sep 07, 2015 @ 02:00 AM | 5,653 Views
Hill intervals (8 min 42 sec)

10min/mile uphill
7min/mile downhill

Did it 4 times in dry 85F with the truck. The motor was super hot after ascending, proving the hot glue holding the hall effect sensor was the problem rather than the glue holding the magnet.
Posted by Jack Crossfire | Sep 06, 2015 @ 01:13 AM | 6,428 Views
After 10 months, the tachometer broke & the truck flew down the mountain. The leading theory is motor heating made the hot glue soft. A hard crash pushed the tire into the hall effect sensor. The glue was soft enough for the hall effect sensor to slip into the path of the magnet. The magnet broke off.

The original magnet used hobby grade epoxy. The new bond used the last of the J-B Weld from 8 years ago which failed miserably at repairing landing gear. The duck's guts is now considered Loctite epoxy for metal.

It was an awful alignment, but this motor also shed a lot of brush dust. It's on its way out. The tire will impact this alignment a lot sooner.
Posted by Jack Crossfire | Sep 03, 2015 @ 11:34 PM | 6,591 Views

So Disney finally announced the fabled Star Wars themed quad copter to coincide with the movie. The quad copter is just a licensed Air Hogs toy, fully manual, no boundary sensors, sonar or camera.

The blog was told of plans for such a thing 2 years ago, but if we could make it autonomous, the license wouldn't have gone to Air Hogs but the one & only Jack Crossfire Inc. Of course, the level of autonomy was quite unattainable even by today's standards. They wanted the speed & accuracy of a vicon tracking system for the cost of a toy. It was still intriguing that the vision actually came to fruition & what Air Hogs shipped had the exact same size & propellers as the proof of concept we made.

This size was not big enough to lift the amount of electronics required for any kind of autonomy. As for the foam styling, there's probably a good market for flying prop replicas. No matter how long the fact that something looks like a historic artifact can keep their attention, they only have to buy it once.
Posted by Jack Crossfire | Sep 01, 2015 @ 11:01 PM | 7,074 Views
10mph intervals from oblique angle (11 min 47 sec)

This angle came out almost professional looking. It might still be an unseen angle in any movie, since no-one has ever run 3 miles with an RC car cam.

Running form is a lot more discernable from this angle, but it's much harder to avoid bikes going 15mph. The combined speed of an impact would be 25mph. Ran off the road once, so driving from this angle is still harder than driving from behind. A purely side view still requires an autopilot.

Unfortunately, the work done on path following would not allow a side view. The car would weave from side to side, manely staying in the center of the path. There is no algorithm which could hug the side of the path. It's another area where lookup tables or convnets differentiating materials could be the best option. It still needs a previous copy of the drive where the materials have been manually labeled.