Author Topic: Hacker Senstrol  (Read 5042 times)

Online Stuart Mellor

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Hacker Senstrol
« on: 22, December 2016, 08:25:13 PM »
New development (at least to me!) - the Hacker Senstrol.

Looks like a constant rpm device (esc)  that monitors the motor rpm & adjusts accordingly thru the esc. Thought at first it might be a rule breaker - but on checking, perhaps not - but sailing very close me thinks.
Yours for 499 Euros.

Stuart

Offline Adrian Harrison

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Re: Hacker Senstrol
« Reply #1 on: 23, December 2016, 08:28:11 AM »
+ the cost of a Hacker motor which is 'chip' matched to the ESC.

Offline Malcolm Harris

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Re: Hacker Senstrol
« Reply #2 on: 23, December 2016, 09:09:58 AM »
When we spoke to Hacker at the World Championships last year they said it would be possible to send in an existing motor to have the sensors required added and matched to the new ESC. They were going to start this within "a few weeks". Then they said that the system would only be available to their team pilots for the foreseeable future and now they have decided they can make more money by selling completely new motors.

All a bit disappointing really.

Malcolm

Online Stuart Mellor

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Re: Hacker Senstrol
« Reply #3 on: 23, December 2016, 03:17:00 PM »
Not a cheap do then -but werry interesting nevertheless.

Just wondered though on the advantage? Would constant rpm give constant speed? (which would probably be illegal)

Just imagining a pull up to vertical & how the motor would respond - probably increasing power to compensate for extra load  & in the downlegs braking to match throttle position.

Still think though, a constant speed device is bordering on illegality within current rules.....

Stuart

Offline Mike Wood

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Re: Hacker Senstrol
« Reply #4 on: 24, December 2016, 09:16:16 AM »
What do people think with regard to it being legal?

Is it like programmable mixing or is it a step too far?

m

Offline Bob Wasson

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Re: Hacker Senstrol
« Reply #5 on: 24, December 2016, 01:29:26 PM »
Hello Mike,


The short answer to your question is that the Senstrol probably complies with FIA Guidelines.  Others may see it differently.


F3A Aircraft rely on 4 primary controls– Motor/Engine, Elevator, Aileron and Rudder.  In control terminology, each of these 4 functions relies on a control system to move the “ Measured Variable” (MV) in accordance with the “Set Point” (SP).  For example - and leaving aside refinements such as exponential and mixes for the moment - if a pilot moved the elevator stick on his Tx to 50% of travel, he would expect the elevator on his aeroplane to follow suit.
 
In practice, whether the MV does follow suit exactly, depends on the sophistication of the control system.  Most modern control systems rely on a digital algorithm which is the equivalent of the older analogue based control systems.  These older systems could basically be divided into 3 main types:


  • Proportional (P only)
  • Proportional + Integral (P+I)
  • Proportional + Integral + Derivative (P+I+D)
In the simple “P only” system the MV aligned with the SP only when zero load was applied to the measured component – for example with the model in still air sitting on the ground.  (Although even then the weight of the control surface would provide some load.)  As soon as a load was applied to the measured component (for example air blow back on the elevator), there was a deviation between the MV and the SP.  The greater the load, the greater the deviation.  Increasing the “Gain” (or tightening the Proportinal Band) on a “P only” control system would decrease the offset, but only up to a point.  If the Gain was increased too far, the controlled surface would start to oscillate.  In effect, the new generation of “Digital” servos increased the Gain/decreased the Offset through an increase in frame rate.  The characteristic buzzing sound, is an indication that any significant further increase would lead to the onset of oscillation. (As a further aside, speak to any R/C Helicopter pilot and he will tell you what happens if the Gain is increased too far on his Stabilisation Gyro!).
 
In the real life of F3A, some small offset between the SP and the MV is likely to be of little consequence.   This is because the pilot himself is also an important component in the “closed loop” control system.  If, for example, the amount of elevator applied does not lead to a tight enough radius on say a loop, the pilot will instinctively increase stick movement until he achieves the right effect.  F3A relies heavily on this continuous human element of fine tuning and even novice pilots soon realise that a constant motor and elevator setting is unlikely to result in a 10 scored loop!


“P+I” control is a refinement of P only.  Without getting too heavily into the mathematics of the algorithm, the “I” element of the control system effectively integrates (i.e. accumulates) any difference between the SP and MV over time, and continues to apply corrective action until such time as any deviation is totally eliminated.  In fast acting, servo operated control systems, this integration can take place very quickly.  However, increasing the amount of integral action in a P+I system can lead to the same type of instability as too much gain in a P only system.


A ”P+I+D” system is a further refinement still, though its use is mainly confined to systems with slow acting transfer functions such as a system for heating a large warehouse.  In such systems the Derivative Action (the “D” bit), effectively boosts the amount of control action that is taken during the early stages of corrective action in order to reduce the amount of time it takes for the SP to align with the MV (eg: for the warehouse temperature to align with the setting on the thermostat).


Though I have no way of knowing, I suspect that the Senstrol is a clever digital equivalent of a P+I (or possibly P+I+D) control system.  In other words it an RPM controller which, in effect, quickly integrates any difference between the Set RPM and the Measured RPM until both are in exact alignment – irrespective of the load applied to the propeller.  Whether it results in any tangible advantage is a moot point, especially since the pilot is the final element in the control system and is continually making fine adjustments to his power settings in the same way as he would be to his A, E and R controls.  Having said that, F3A is all about small gains, and any improvement, even if mainly psychological, could result in the difference between being a winner and a runner up.


As to its legality, I very much doubt that it would be classed as illegal, any more than a control system that always ensured that an elevator always moved exactly to the pre-set stick position irrespective of the amount of blow-back.  In the final analysis, the pilot will still be making the adjustments necessary to achieve the perfect speed and flightpath – not an autopilot.  Not only that but I suspect that Hacker would be unlikely to spend any significant cash on it's development if they had any doubts about it being legal.


Sincere apologies if I have wittered on and overcomplicated matters.  If you have got this far, may I wish you a very Merry Christmas and a very happy New Year.


 
Bob Wasson
« Last Edit: 24, December 2016, 06:04:06 PM by Bob Wasson »

Offline Mike Wood

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Re: Hacker Senstrol
« Reply #6 on: 24, December 2016, 02:28:08 PM »
Bob wow

Thanks for that.

Mike

Offline Phil Lewis

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Re: Hacker Senstrol
« Reply #7 on: 24, December 2016, 03:23:28 PM »
"In other words it an RPM controller which, in effect, quickly integrates any difference between the Set RPM and the Measured RPM until both are in exact alignment – irrespective of the load applied to the propeller". 

I don't know either but that is exactly what it must be doing, if the output of the servo channel is 1000 to 2000 us the 1000 is stopped and 2,000 is the full RPM (it must have a way to calibrate that). So rather than the throttle controlling how much of the time the motor "see's" the battery this chip controls that increasing the time if the motor slows and decreasing it if starts to over speed, measuring thousands of times per second it is telling the esc to switch accordingly.

Put simply it is a heli variable (with the throttle stick) governor mode.

It could also quite easily be made as an add on, you would plug the esc connection into this and then this into the RX so something like that is probably being made in China right now and I would guess would be for somewhat less.

Quite why (apart from to sell more motors) they have put the chip in the motor I can't see any other reason than temperature sensing which is nice but hardly necessary. 


Offline Mike Wood

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Re: Hacker Senstrol
« Reply #8 on: 24, December 2016, 03:41:29 PM »
Good point, it would seem it could be a stand alone add in.

m

Offline Adrian Harrison

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Re: Hacker Senstrol
« Reply #9 on: 24, December 2016, 04:35:31 PM »
I believe there are two controls RPM as discussed and a torque control.
Over to you Bob....... Happy New Year ;)
Adrian
Bob text me if you need a food parcel 8)

Offline Bob Wasson

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Re: Hacker Senstrol
« Reply #10 on: 24, December 2016, 06:00:40 PM »
Hello Adrian,

I had no idea that Buurmingham had moved on from diode/triode valves and lead acid batteries. But this time you’re likely to be bang on the money.


The RPM sensor will be used to provide the necessary feedback regarding the true rotational speed of the shaft, which will differ from the output of the Speed Controller depending on the propeller load and motor slippage.  I can only guess that the Torque sensor is some clever means of speeding up the response time and/or increasing the stability of the control system.  It must have taken a fair old time to perfect as there were rumours of Matt and other preferred Hacker pilots using prototype systems quite some time ago.


As to the food parcels, a very kind offer but no need to worry.  You’d be surprised what you can do with a potato these days.  Sheelagh has been in training to pedal the generator and as long as I keep her well topped up with potcheen, we should be all set for another piping hot Christmas dinner.


Great to hear about you joining forces with Chris and Keith.  A great idea and I wish you all every possible success.


Very best wishes for Christmas and may your next year’s score cards all be full of birdies.


Bob

Offline Adrian Harrison

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Re: Hacker Senstrol
« Reply #11 on: 24, December 2016, 06:19:42 PM »
Cheers Bob lets hope we can meet up in the New Year.
Adrian

Online Stuart Mellor

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Re: Hacker Senstrol
« Reply #12 on: 24, December 2016, 06:44:46 PM »
I agree with Bob (but only partly! - in that, yes, it would be unlikely for Hacker to invest in a system that contravenes the rules.... yes but ther'es a but coming.... BUT

Sporting Code:

Permitted: "2.Any type of button or lever that is initiated by the competitor."

Not permitted:  3. Auto-pilots or gyros for automatic wing levelling or other stabilisation of the model aircraft."

 if I were an FAI official (heaven forbid) I might argue that the device does not comply with 2. and this is a feed back device not switched by the pilot, in an attempt to stabilise the flight automatically and also may contravene " stabilisation on the model aircraft" in 3.

In short, a method of stabilising or enhancing flight automatically sans pilot input.

But then again , I always was a trouble maker.... & Hacker is a big player.......

Stuart

ps -  a merry F3-A Christmas to one and all


Offline Mike Wood

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Re: Hacker Senstrol
« Reply #13 on: 24, December 2016, 07:16:46 PM »
On the information so far I'd go with Stuart!

Programmable mixes mix in fixed amounts of deflection and aren't dependent on any feedback.

Mike

Offline Bob Wasson

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Re: Hacker Senstrol
« Reply #14 on: 24, December 2016, 07:37:40 PM »
Depends on how you define stabilisation.


I would argue that a control system that maintains a constant RPM irrespective of propeller load is no different to a control system that maintains a constant control surface deflection irrespective of blowback forces.  Both contain an element of feedback.  That is what the feedback potentiometer in a servo is there for – to provide position feedback!  The RPM sensor in a Senstrol is no different.


If Hacker’s system was further refined to provide a constant airspeed (as opposed to constant RPM), that would be a different matter.  Such a system might well be regarded as infringing on the concept of automatic flight control.
 
With a Senstrol system, the pilot remains in control of both the aircraft’s speed and aircraft’s position and attitude in all 3 axes.


Bob
« Last Edit: 24, December 2016, 08:05:25 PM by Bob Wasson »