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Old Mar 25, 2012, 06:53 PM
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I just received 5 of these HK SS 18-20a Card Programmable ESCs which I plan to reflash with SimonK's tgy.hex firmware.

I probably wouldn't have considered it but read about n3m1s1s's problems with these HK SS 18-20a Non Card Programmable ESCs. It seems that the firmware recently changed and now they release the magic smoke when connected to some flight controllers (not sure what he is using).

Then I read Warthox's recent bad experiences with his favorite Hobbywing ESCs where they recently switched to a SIL chip.

So maybe there is not much of a difference between "good" stock firmware on a HK ESC and SimonK's.

But...I don't really trust what fw version they loaded at the HK factory. Also, I understand that the motors run quieter (less whine) with SimonKs fw and most report more stability after reflashing.
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Old Mar 25, 2012, 07:02 PM
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Originally Posted by photronix View Post
Not sure the video proves anything really. I've watched it in the past. It's pretty obvious that the throttle range is different on each test and one seems to be balanced well.
If you don't understand what the video demonstrates, you're not qualified to write up this review and (once again) spread misinformation. Could it be that you're about to start selling "maytech" "400hz" "escs"?
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Old Mar 25, 2012, 07:18 PM
Al Ducharme
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Originally Posted by timecop View Post
If you don't understand what the video demonstrates, you're not qualified to write up this review and (once again) spread misinformation. Could it be that you're about to start selling "maytech" "400hz" "escs"?
Ok...that's about what I expected....

I said in the post that the results indicate NOT to use the Maytech.

The video is not quantitative analysis. If it was I wouldn't have bothered writing the post.

Honestly, I am trying to spread GOOD information in the hope that someone with appreciate it.

Work with me here Timecop you're a highly intelligent poster and I have come to respect the nuggets of information you share. This is hopefully one of mine.

I've been measuring and teaching transfer function testing for 20 years.
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Old Mar 25, 2012, 07:24 PM
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Originally Posted by timecop View Post
If you don't understand what the video demonstrates, you're not qualified to write up this review and (once again) spread misinformation. Could it be that you're about to start selling "maytech" "400hz" "escs"?
I would like to see that test video done again, this time with some consistency in rpm used, and perhaps some monitoring with an oscilloscope showing the time delay between the signal sent from the gyro, and the signal sent to the motors. You have the issue of how long it takes for the motors to actually change speed after the signal to do so has been received. For all we know that delay could have been substantial, and a simple change of rpm may bring it into a phase where it stabilised the arm. I am not convinced by the footage, it's not to say it isn't true, it's just not all that scientific.
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Old Mar 25, 2012, 07:29 PM
Al Ducharme
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Originally Posted by Erknie View Post
I would like to see that test video done again, this time with some consistency in rpm used, and perhaps some monitoring with an oscilloscope showing the time delay between the signal sent from the gyro, and the signal sent to the motors. You have the issue of how long it takes for the motors to actually change speed after the signal to do so has been received. For all we know that delay could have been substantial, and a simple change of rpm may bring it into a phase where it stabilised the arm. I am not convinced by the footage, it's not to say it isn't true, it's just not all that scientific.
Agreed.


I also wanted to point out, on a different subject, that at 6000 RPM asking a motor to change faster than 100 Hz doesn't really seem realistic. This would equate to changing the speed more than once (at higher than 100Hz) during a single rotation.
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Old Mar 25, 2012, 07:45 PM
Tri-Quad-Hexa-Octo-copters!!
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Gents,

Here is KapteinKuk's ESC response thread with scope data: http://www.rcgroups.com/forums/showthread.php?t=1250488

Note that while Art's previously posted video of the ESC firmware comparison's of a very good figure of merit (FOM) operational test of how an ESC firmware affects motor/prop and a very fast gyro update, it would be excellent and more robust with some additional metrics: http://www.rcgroups.com/forums/showp...55&postcount=9

From the ESC recommendations and converting ESCs to I2c and to faster PWM section in the Quadrocopter and Tricopter Mega Link Index
--TIP 11: For faster ESC PWM update rates for use on most current flight controllers that output ~400Hz update rates, it is recommended to flash Quax/SimonK ESC firmware to take advantage of the higher performance. You can DIY per the Fast PWM links such as Nek's SimonK fast PWM firmware thread, or order the ESC's specifying that you want the fast PWM loaded from Ken in the USA at www.quadroufo.com , or Timecop in Japan at www.abusemark.com , or Dan in China at http://www.multircshop.com/site/inde...product_id=627., Flitelab in Canada: http://www.flitelab.com/OnlineStore/...hedSimonK.aspx
--Conversion thread: http://www.rcgroups.com/forums/showthread.php?t=766589


While some ESCs such as the Turnigy Plush's will give the multicopter the appearance of flight stability, the Simonk firmware still is the best out there compared to OEM ESC firmware ESCs that are not designed specifically for multicopter use and includes what I seek in ESC performance for multicopters:

FWIW Here is my wish list for proper Multicopter ESCs:
Multicopter ESC requirements:
- The PWM ESCs should be able to do at least 400hz + update rate and running at 16khz.
- ESC endpoint throttle calibration must be manual. Automatic calibration is bad for multicopters.
--Note: This must also consider that there are some different throttle ranges, i.e. 200-1200μs vs. the more standard 1000-2000μsaccomadate the various throttle ranges
- Linear throttle-no curve or "smoothing".
- >250+ steps.
- No LVC or the ability to turn it off.
- ESC prop stop if stalled by hand, etc, then restart.
- Governor off.
- Brake off.
- Start normal.
- Motor timing optimization for 12+ pole outrunners 500-1500Kv. (Dynamic changes are bad for multicopter performance).
- Available in Amp ranges from 5-80A. Typically 20A, 30A, 40A.
- Graceful over current protection that does not constantly affect multicopter performance as it fights windy conditions.
- No BEC on-board.
- Also some I2c versions or the ability to do both PWM and I2c like the YGE ESCs can do.
- Future considerations:
--Two way communication for dynamic braking with inputs from a flight controller.
-- Serial comm.
Cheers,
Jim
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Old Mar 25, 2012, 07:48 PM
Arx
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A transfer function can only be used to completely characterize a linear system, which this isn't.

There are limits intentonally imposed in the firmware for ramp-up speeds, etc, which can vary in implementation drastically. Your testing is likely to bump into these limits, and depending what you have for a load, will give you results completely independent of what matters.

To use an extreme example, If you were to test with a completely unloaded motor, with an ESC with no accel/decel limiting, it would respond "extremely well" on your test. Yet the same setup, with a heavier load, would probably just stop and vibrate, making some high pitched squeeling noises.

Regarding that test video with the motors bouncing around, I gotta agree with timecop on this one.. You need to try and understand what's going on there. That's a lot more revealing than what your "transfer function" will be.

Kudos for trying to put some engineering into it, but be careful what you present as fact, based on a single, fairly limited test.
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Old Mar 25, 2012, 07:56 PM
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Originally Posted by photronix View Post
Agreed.


I also wanted to point out, on a different subject, that at 6000 RPM asking a motor to change faster than 100 Hz doesn't really seem realistic. This would equate to changing the speed more than once (at higher than 100Hz) during a single rotation.
yuuup! (watching storage wars)

Seriously, thank you for the info. Great write up as well.
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Old Mar 26, 2012, 01:14 AM
Arx
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Originally Posted by photronix View Post
Agreed.


I also wanted to point out, on a different subject, that at 6000 RPM asking a motor to change faster than 100 Hz doesn't really seem realistic. This would equate to changing the speed more than once (at higher than 100Hz) during a single rotation.
Why is that a problem? If It wants to go from 5999 to 6002 RPM, how long is it going to take to get there?
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Old Mar 26, 2012, 01:51 AM
hacker
Canada, BC, North Vancouver
Joined Dec 2010
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Hello! Thank you for doing these tests!

There are other graphs I would like to see. Could you post the raw data? I suspect, for example, the average RPM (or RMS RPM which is probably actually closer to thrust) is rising with the input frequency. I suspect the CC ESC is employing active braking, which will keep the average RPM much lower in this case, and make it appear as having less attenuation because the negative delta duty cycle requests will be amplified. This should actually map to stability as well and so is important, but at some point the trade-off will be with power consumption. (Isn't your Y-scale backwards?)

I was considering implementing a poor-man's active rectification with fixed proportional diode conduction assumptions, since this should effectively produce active braking and increase efficiency at the same time, if only just to see what result it might have in a test such as this. Your setup would be useful for comparisons here.

I have a few suggestions that might be worth looking at. First, it would be useful to test Mystery/BlueSeries/ztw type ESCs with stock firmware, since they seem to have much more significant throttle input averaging than the Hobbywing/Turnigy series, and I do not believe it is affected by input rate. Also, although not directly related to thrust, measuring the duty cycle output (lag, resolution, and bandwidth) might give you data with a lot less noise, assuming you want to exclude active braking from the equation for a fair comparison of control bandwidth.

One thing I find odd with your plot is that RCTimer ESCs (<= 30A) actually all run the same software as shipped on older, ATmega-based, Turnigy Plush ESCs. So, unless the update to SiLabs MCUs significantly changed the response, I would expect the numbers to match. (Unfortunately, both have "V3.1" on the sticker.) With this code, the throttle input is averaged on every received pulse, which means that higher update rates reduce the averaging lag-time, as tested here: http://www.rcgroups.com/forums/showthread.php?t=1250488 ... I suspect you will see less "attenuation" with the RCTimer ESC if you changed your test to send pulses at 400Hz, for example. This is what I believe largely lead to the believe that high update rates are required -- it just works around this implementation issue.
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Old Mar 26, 2012, 12:23 PM
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Photronics Thanks for putting some real science (measured data and facts) into this kind of discussion.
Jim
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Old Mar 26, 2012, 03:42 PM
Al Ducharme
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Originally Posted by Jem3 View Post
Photronics Thanks for putting some real science (measured data and facts) into this kind of discussion.
Jim
Thanx Jim....I was beginning to wonder if people still wanted to work together on RCgroups. I just realized today that I was stepping on some toes because people sell re-flashed ESCs.

Sorry to all those people re-selling re-flashed ESCs I am sure they work much better.
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Old Mar 26, 2012, 04:18 PM
Arx
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Originally Posted by photronix View Post
Thanx Jim....I was beginning to wonder if people still wanted to work together on RCgroups. I just realized today that I was stepping on some toes because people sell re-flashed ESCs.

Sorry to all those people re-selling re-flashed ESCs I am sure they work much better.
While that's probably true, there are some differences between the reflashed and stock ESCs, and it seems pretty hasty to just dismiss the reflashed ones as no better than stock. If it were that simple, Simon would be kind of a dumbass to be wasting his time writing firmware.

There are differences that go beyond what the test you're doing can resolve, and some of them are quite evident in peoples empirical testing (Definitely not just their imagination).

That's not to say that your measurements are wrong, or useless, just that it's not quite as simple as your original post implies.

Keep up the good work on this stuff, just don't throw away everyone else's testing and experiences as invalid.

With that test with the bouncing motors, I believe the "throttle range" was pretty much just controlled by a servo, I interpreted that bouncing as oscillation due to the lag. Sure, the gain might just need to be tweaked downward to stabilize it as well, but that is undeniably a useful result. That said, I don't really understand what the deal was with the 3rd one.
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Old Mar 26, 2012, 04:27 PM
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Originally Posted by photronix View Post
Thanx Jim....I was beginning to wonder if people still wanted to work together on RCgroups. I just realized today that I was stepping on some toes because people sell re-flashed ESCs.

Sorry to all those people re-selling re-flashed ESCs I am sure they work much better.
Thanks for the work, people can decide the value of it for themselves. Which it seems they are

Greg
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Old Mar 26, 2012, 06:07 PM
Al Ducharme
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Originally Posted by Arx View Post
Why is that a problem? If It wants to go from 5999 to 6002 RPM, how long is it going to take to get there?
I am taking a look at this.
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