[NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions

Tue Jun 9 17:41:01 AKDT 2020

@ Throttle Tech – it is an open loop device, so clearly not illegal.  If the use of Throttle Tech results in not enough power, it’s a matter of adjusting it to not clip as much off the peak power.

@ D3 with respect to AMA rules – It is legal because it is not specifically aware of “model performance, position or attitude”.  Most certainly RPM does not equate to model performance.  Full throttle RPM static operating conditions are certainly not the same as full throttle level flight, or full throttle uplines, and the D3 has ZERO awareness of the model performance, position, attitude, speed, accelerating, decelerating, etc.  I expect the D3 is governing RPM based on actual RPM (or commutation rate) and not the “load” of the motor.  Most certainly the D3 is closed loop in terms of measuring RPM and adjusting power output to maintain that RPM – that specific aspect is (intentionally) not addressed in the AMA rules.  As Jeff W noted, IF the D3 were adjusting RPM based on airspeed, then it would be illegal.  All modern ESCs look/sense “load” on the motor and dynamically adjust timing, and some ESCs in some modes also dynamically adjust PWM.  I believe that is the reason why the AMA rules are written as they are – to allow the function of modern day brushless ESCs….nobody wants to go back to brushed motors and ESCs.

Consider a normal loop flown from level flight at half throttle, with zero change in throttle input.  A data log would show decreased RPM with increased amps during the climbing portion of the loop, and then increased RPM with decreased amps on the diving portion of the loop.  The ESC has no awareness of the model performance, position or attitude….it is just the behavior of electric motors subjected to variable load.  This is an example of changing RPM and motor operating conditions outside of specific model performance.  The D3 also changes motor operating conditions without knowledge of specific model performance.

@ Dynamic braking.  I am not certain what the specific definition of dynamic braking might be.  Traditional ESCs simply apply a short across 2 legs such that the motor acts as a generator and the result is “drag” that slows the motor RPM against the driving force (forward airspeed).  The amount of drag is generally programmed as braking percentage, and is generally on/off with airplane ESCs/software.  Some ESCs allow variable braking based on the throttle stick position – notably the old Schulze ESCs (the expert on those being Chad N) which allowed a proportional amount of stick travel close to idle to adjust the braking strength – still, the mechanism for braking was “drag”.  In the braking mode, traditional ESCs are basically blind to the position of the motor and the ESC needs to re-sync to run the motor after the brake is de-activated.  In a governing mode, the ESC is actively “driving” the motor to stay at a specific RPM whether needing to add power or harvest power, and the ESC is never blind to the motor position.

Regards,

Dave

From: NSRCA-discussion <nsrca-discussion-bounces at lists.nsrca.org> On Behalf Of Jeff Worsham via NSRCA-discussion
Sent: Tuesday, June 9, 2020 7:08 PM
To: Vicente Bortone <vincebrc at gmail.com>
Cc: chadnortheast at gmail.com; General pattern discussion <nsrca-discussion at lists.nsrca.org>
Subject: Re: [NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions

Who flies pattern on a calm day without using the brake on their esc?  If D3 is illegal, then so are all esc’s that use dynamic braking to help control downline speed.

On Jun 9, 2020, at 3:36 PM, Vicente Bortone <vincebrc at gmail.com <mailto:vincebrc at gmail.com> > wrote:

I agree.  No close loop control is allowed unless the pilot close de loop.  In essence all open control loop with fix values of control is allowed.  Looks like is the case of this ESC.  One example is the cars speed control.  The old ones are open loop.  The new ones that can maintain distance are close loop control.  It is measuring the distance and adjusting constantly.   I believe this ESC is open control loop so it should be allowed. 

Vicente “Vince” Bortone 

On Tue, Jun 9, 2020 at 4:06 PM Jeff Worsham via NSRCA-discussion <nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> > wrote:

Adding a pitot tube with feedback loop into the throttle channel would violate the rule. 

On Jun 9, 2020, at 9:38 AM, tim pritchett via NSRCA-discussion <nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> > wrote:

Hey Dave,

   I couldn't really tell whether you are saying it violates the reg. or not.  My guess would be 'not', but you kind of make the case both ways. The D3 is a power management system that does make power adjustments based on model performance.  It senses the 'load' on the motor, and increases power, if I understand it correctly.  Since the motor is not part of the ESC, it's part of the model, and its performance is being read.  You also said 'the D3 doesn't know why the change is needed.....' but actually it does.  It knows that the motor RPM (part of the model performance) has changed, and corrects with a power adjustment.  The difference seems to be whether or not you consider motor RPM to be part of the model's performance.

   I can see the similarity with servo's, but they are not in question here.  The argument should be made as to why ESC's are singled out, but nevertheless, they are.  Throttle tech acts differently, I think.  It caps the power output to preserve battery life, if I remember correctly.  All I remember about using one was that I didn't have enough power!  

    If this regulation does not apply to this capability, I wonder what it's written for? About all an ESC, or power management system, does is vary the power.  And the reg. says it can't do it automatically.  If the Contest Board ultimately decides these are ok to use, I can't figure out what else would constitute a violation - the rule should be struck as superfluous.  I actually hope that's the case, which is the point of this discussion ;)

-----Original Message-----
To: tjpritchett at aol.com <mailto:tjpritchett at aol.com> ; 'General pattern discussion' <nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> >; ejhaury at comcast.net <mailto:ejhaury at comcast.net> ; chadnortheast at gmail.com <mailto:chadnortheast at gmail.com> 
Sent: Mon, Jun 8, 2020 9:58 pm
Subject: RE: [NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions

In order for the ESC to make power adjustments with regards to model performance, position, or attitude, the ESC must be aware of the model performance, position, or attitude.  Just as the servo has an internal feedback loop, so do ESCs – even those without the governing function of the D3.  Traditional ESCs and the D3 do their work without knowing the model performance, position, or attitude.

The D3 could decrease or increase power to the motor to prevent RPM from increasing for a variety of reasons – the plane is diving or climbing, the lipos are getting warmer (more efficient) or colder (less efficient), prop “bite” is changing due to changing airspeed, etc.  The D3 doesn’t know why the change is needed, and it does not know the specific result of changes made (other than RPM is being maintained).  When Throttle Tech was being developed, I talked with quite a few people about the legality of the concept (including Ramel), and it was deemed to be legal – primarily on the basis that Throttle Tech received zero information about the speed, attitude, position, performance, etc of the plane.

I flew the D3 quite a bit on a V4 Contra Drive, and detailed my final setup at RCU – post 1928 on this thread https://www.rcuniverse.com/forum/electric-pattern-aircraft-385/9833118-contra-rotating-propeller-drive-f3a-2m-pattern-planes-78.html  It is a very good ESC.  Specific to the V4 vs Castle w/ Throttle Tech, the absolute downline braking is not improved, but the behavior is different.  The Castle is capable of slowing the prop RPM too much in a downline (buffeting sound occurs, and this is possible with other ESCs as well), and the D3 can slow the props too much in a downline as well, and the D3 takes a variable amount of time (short) to “catchup” and govern properly again.  It took me quite a few flights to get the D3 properly tuned for the V4 – tuning for a direct drive single prop is much easier.

One additional consideration with the D3 – SAFETY!!!  The throttle curves that work best inflight generally have a very high idle – high enough that landings are difficult or impossible.  So the use of 2 or more throttle curves is needed, and if the “flight” throttle curve is inadvertently selected on the ground, a V4 contra is going to be “idling” fast enough to take off.  Others have posted that inflight RPM of single prop setups is ~2000 RPM -which is considerably higher than the traditional ~500 RPM of traditional ESCs.

Regards,

Dave

From: NSRCA-discussion <nsrca-discussion-bounces at lists.nsrca.org <mailto:nsrca-discussion-bounces at lists.nsrca.org> > On Behalf Of tim pritchett via NSRCA-discussion
Sent: Monday, June 8, 2020 11:23 AM
To: ejhaury at comcast.net <mailto:ejhaury at comcast.net> ; chadnortheast at gmail.com <mailto:chadnortheast at gmail.com> ; nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> 
Subject: Re: [NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions

Earl, 

   Good analogy with servo loops.  I suppose if the regulation were written about control surfaces, we'd all by flying control line.  

The rule as written however seems to explicitly restrict ESC's from self-regulating power output.  With this device, when the plane changes attitude, the ESC adjusts power.  Self regulating speed controllers had to be the targeted restriction; what else is there in an ESC?

FYI - I asked the AMA about it and have two different perspectives so far. Some of those folks may be on this list as well, but I'll share their feedback when it's determined.

-----Original Message-----
From: EARL HAURY <ejhaury at comcast.net <mailto:ejhaury at comcast.net> >
To: Chad Northeast <chadnortheast at gmail.com <mailto:chadnortheast at gmail.com> >; General pattern discussion <nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> >; Tjpritchett <tjpritchett at aol.com <mailto:tjpritchett at aol.com> >
Sent: Mon, Jun 8, 2020 9:50 am
Subject: Re: [NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions

I suppose an Electronic Speed Controller might be expected to actually control motor speed, however most don't. They simply control the amount of power applied to the motor. Great to see some ESC's that now actually control motor speed! F3A rules don't address power management systems, while the AMA rule would appear to address aircraft performance rather than motor speed control. Possibly the latter needs some wordsmithing.  

Certainly the new ESC systems involve an on board feedback loop. However, with the exception of retract servos, all of our servos use an internal feedback loop to ensure that they move and hold where we command. So we've been flying with feedback loops in our airplanes since the exit of escapements and ESC's are just catching up. 

As has been pointed out, as long as the pilot must select the control input (be it surface position or motor rpm) these systems are well within the rules. Systems that automatically maintain aircraft attitude (gyros) or speed (pitot data to ESC for example) aren't.  

Earl 

On June 7, 2020 at 2:08 PM Chad Northeast via NSRCA-discussion <nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> > wrote: 

So many of us (myself included) flew these at the WC in 2019, and there were many events in Europe that allowed their use.  As well the Hacker Sensitrol (similar function, however it uses direct rpm measurement I believe) was also in use at the WC in 2019, so there is some good precedent for legal use at least internationally.  They were known to the event organizers/jury/judges etc. that they were being used, and no one was disqualified or asked to remove them that I am aware of.  Personally I did bring along a full batch of other esc’s in case this happened as there was definitely “chatter” about them being illegal, however it turned out that was not an issue.  

My understanding is it would become illegal if you say used it to maintain airspeed, which would then in turn auto adjust the throttle input from the rx, essentially taking the pilot out of the “control loop”.  What I understand in simple terms is that as long as the pilot is part of the control loop then its most likely legal. 

Maybe Mark or Derek, or someone more in the loop on the inner workings of the rules with the FAI can give more info. 

It would be a great shame to make these sorts of innovations illegal as ultimately it will stifle creativity and has zero bearing on the results.  Everyone has access to them, so its a level playing field, the best pilot will rise to the top as usual. 

Chad 

Sent from my iPad 

On Jun 7, 2020, at 12:34 PM, Tjpritchett <tjpritchett at aol.com <mailto:tjpritchett at aol.com> > wrote: 

As I was reading this thread, I was wondering how a self regulating speed control might fit within the current competition regulations. We’ve considered the gyro/ stabilization debate before, and that issue is pretty clear, since the relevant rule was written after gyro control was already available.  

This capability, prop rpm, was not really around until now, and may need to be evaluated more carefully against existing rules. The most relevant I could find is copied and posted below, from the 2020-2021 AMA Competition Regulations, 4.4.2.  Point number 3 seems particularly relevant.  

What do you think? 

Examples of control functions not allowed: 

1. Preprogramming that will automatically perform a series of commands based on a timeline. 

2. Automatic leveling or electronic stabilization in any axis. 

3. Power plant management systems that adjust power with regards to model performance, position or attitude. 

4. Positioning systems utilizing any sensors such as air data, GPS, distance, etc. 

5. Learning functions involving maneuver-to-maneuver or flight-to-flight analysis. 

Sent from my iPhone 

On Jun 7, 2020, at 1:11 PM, flyintexanmark via NSRCA-discussion < nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> > wrote: 

A slight tweak in kv and a d3 should allow use of a ys200 prop. The right throttle curve and it may be possible to get Bryan Hebert to fly electric :) 

Seriously it seems more possible now than ever to emulate a YS. 

-------- Original message -------- 

From: Chad Northeast via NSRCA-discussion < nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> > 

Date: 6/7/20 9:27 AM (GMT-06:00) 

To: nsrca-discussion at lists.nsrca.org <mailto:nsrca-discussion at lists.nsrca.org> 

Subject: Re: [NSRCA-discussion] Plettenberg Advance 30-10 ESC - Questions 

I will chime in my 2 cents on the Pletty.  I have used the Jeti Spin 99 and the Futaba 9100 (same as OS 1100) and the D3, all of them without issues so I think you are safe with those for sure.  I have not used the CC or the Jeti Mezon, but I imagine the Mezon is like the Spin.  There is no issue taking a Pletty Advance to 90A, and no issues for big props, in fact the bigger the better.  I use a 22-13, which hits around 85A and 6300 RPM on the ground, any prop made you can run on the motor depending on what you like. 

Braking has always been an issue, even with the Jeti/Futaba ESC braking set I have never been able to get it “perfect” where its good in downlines and in 45’s etc, there always seemed to be a compromise.  Propellor selection had some impact, I found APC’s brake better than a Falcon on their own so that helped to get the balance better at least for my style. 

This is where the D3 shines (braking/constant speed), I think blows the doors off every other controller made.  It is a total re-learn of how you fly, but once you get it I don't think you would want to go back.  For those that don't know, the D3 is produced just for pattern and is custom to every motor, so you order for the motor you want.  There is no programming, no telemetry, nothing really, you just put it in the model setup your tx and fly.  It is a governor controller so setting up your RPM is absolutely critical, if you get it wrong you will not have great results and likely struggle with it.  However the ability to get constant speed is very good, it really turned the Pletty into a setup that has braking as good as anything else IMO.  It manages power for you in a lot of cases, for instance as you pull vertical and the models starts to slow down and load the prop the esc will apply power to maintain rpm, so you don't need to throttle up much, maybe 2 clicks on the stick. 

Some of the adjustments you need to get used to, generally you want to start throttling up prior to pulling the exit radius, as the esc is always maintaining rpm of the motor you dont have that freewheel to help carry speed out of an exit.  So if you don't throttle up early you will really lose airspeed.  Mostly in looping elements you actually never need to really come to a full idle, as the esc is essentially braking all the time to maintain the rpm based on your stick position. 

I have also found it very efficient consumption wise, as good or better than the Futaba/Jeti’s that I have used prior.  Some really nice side benefits, it is light ~70g and inexpensive. 

Below is a chart of rx output and motor rpm for the Pletty, personally I use 950 rpm for landing, 1950 rpm for normal flight (downline idle), and 5600 rpm at my midstick position.  In case it doesn’t show up properly, one column is % of output, one column is us output of rx (0 - 2000 us) and last is motor rpm. 

100.00%

2000

6700

90.00%

1800

6030

80.00%

1600

5360

70.00%

1400

4690

60.00%

1200

4020

50.00%

1000

3350

40.00%

800

2680

30.00%

600

2010

20.00%

400

1340

10.00%

200

670

0.00%

0

0

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-- 

Vicente "Vince" Bortone

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