Author Topic: Active Pitchcontrol  (Read 331794 times)

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mbouwer

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Re: Active Pitchcontrol
« Reply #924 on: February 05, 2018, 02:10:45 PM »
Kitestrings,

You are right of course. But the drawing only served to support the question which I very much would like to talk about.
How can we improve the components?

mbouwer

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Re: Active Pitchcontrol
« Reply #925 on: March 15, 2018, 08:25:23 AM »
It seems to me worthwhile to regard the pitch steering as used by Midwoud

mbouwer

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Re: Active Pitchcontrol
« Reply #926 on: March 16, 2018, 05:12:28 AM »
The steering is based on the measuring of the voltage of one of the phases of his Piggott generator.
But I would rather like that he describes the circuitry.
« Last Edit: March 16, 2018, 05:30:28 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #927 on: March 25, 2018, 08:55:40 AM »
What about other ways of measuring the rotations per minute,
and on that basis installing the angle of the blades?
« Last Edit: March 25, 2018, 09:02:01 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #928 on: March 26, 2018, 09:48:01 AM »
It would also be nice if I could make a simple direct-drive motor to move the pitch steering rod.
« Last Edit: March 26, 2018, 10:53:43 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #929 on: March 27, 2018, 06:12:24 AM »
On reflection I would like to first try an axial direct-drive motor.
It only must turn limited rpm.
How to make the control?
« Last Edit: March 27, 2018, 06:28:38 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #930 on: March 29, 2018, 09:06:56 AM »
The pitch steering rod provides at the same time the axle for the hub with the magnet discs.
 

mbouwer

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Re: Active Pitchcontrol
« Reply #931 on: March 30, 2018, 09:20:47 AM »
Number and thickness of the magnets is not determined yet.
« Last Edit: March 30, 2018, 09:27:12 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #932 on: March 31, 2018, 05:56:49 AM »
The heart of the statormal is divisible to facilitate unloading.

midwoud1

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Re: Active Pitchcontrol
« Reply #933 on: March 31, 2018, 11:15:22 AM »
Actuator  test setup  during high windgust at max  windmill  rpm.


https://www.youtube.com/watch?v=N3hPAq9e8gA




mbouwer

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Re: Active Pitchcontrol
« Reply #934 on: April 09, 2018, 03:09:00 PM »
Is the actuator in your mill of the same type as this one?

midwoud1

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Re: Active Pitchcontrol
« Reply #935 on: May 04, 2018, 04:33:39 AM »
lineair actuator  active blade pitchcontrol. Reliable system.

Adjustable stroke / speed , forward and reverse , powerfull Cordless drill motor , Timing belt ,

threaded rod .  Actuator activated by max and minimum prop rpm by an Arduino Controller.

« Last Edit: May 04, 2018, 04:38:29 AM by midwoud1 »

SparWeb

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Re: Active Pitchcontrol
« Reply #936 on: May 04, 2018, 10:19:49 PM »
So much closer to reality.  You must be getting excited to see the hub mechanics come together.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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midwoud1

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Re: Active Pitchcontrol
« Reply #937 on: May 05, 2018, 07:05:38 AM »
Glad to see other hub mechanics .Hope we can interchange ideas, alot experience here.

mbouwer

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Re: Active Pitchcontrol
« Reply #938 on: June 29, 2020, 03:44:46 PM »
When Midwoud started this topic there were lots of nice enthusiastic reactions, and I thought that windmill friends would pick up the design and go on with it and write about on the forum.


mbouwer

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Re: Active Pitchcontrol
« Reply #939 on: June 30, 2020, 04:06:36 AM »
Maybe people who live on the countryside and want to do something with wind energy can tell what they are hiccups about.
We can then look at possibilities, for example through cooperation.

mbouwer

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Re: Active Pitchcontrol
« Reply #940 on: July 01, 2020, 03:17:17 PM »
A windmill friend told me that I may have expressed myself wrong in Reply # 939

What I  wanted to say:

Maybe people who live in the countryside, and want to do something with wind energy, can tell us what kind of windmill they want to build.

kitestrings

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Re: Active Pitchcontrol
« Reply #941 on: July 02, 2020, 04:24:41 PM »
Hi mbouwer,

My concerns with a variable, powered-pitch mechanism like this are pretty much the same.  To me, it adds quite a bit of complexity up on the tower.  With this comes extra components & weight, wear points & maintenance and the potential for failure.  For a small turbine it is just hard to justify.

Generally I've leaned toward passive designs like a furling tail.  We have added a power furling unit at the base of the tower to shut things down either automatically or by manual intervention - say in the case of an imminent storm, but the normal furling happens all on its own.  It is not dependent on a motor or actuator or control to function.

I'm in no way trying to discourage you, rather I've enjoyed the progress, and alternate approaches.  It may, however, be one reason others haven't adopted this design.  Other factors are quite simply that PV has far and away taken reign of much of the RE market.  It has become lower cost, more predictable, modular... and comparatively easier to permit and get installed.  I think there are just less of us wind enthusiasts still around now...

~ks

mbouwer

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Re: Active Pitchcontrol
« Reply #942 on: July 03, 2020, 11:20:47 AM »
Hi Kitestrings,

With pleasure I always read what you show us about your turbine.

But do'nt you think active pitch control would be a real improvement also for you if it could be maded simpler and fail safe? Proper implementation may take a while, but that's a challenge and no problem.

The pitch drive can also be done from below the mast.  Then it is always possible to control your turbine, and in a storm it can continue to run quietly. The load remaining low.

Wind mill enthusiasts are a little dreaded to build a heavy nervous windmill in their yard I think.

I would like to focus on nice creations, with slow speed, and always manageable.

And for which we can supply to each other the components.

Regards Rinus

kitestrings

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Re: Active Pitchcontrol
« Reply #943 on: July 03, 2020, 12:55:52 PM »
Quote
But do'nt you think active pitch control would be a real improvement also for you if it could be maded simpler and fail safe? Proper implementation may take a while, but that's a challenge and no problem.

Actually, I don't...I guess this is my point.  Having installed and maintained small turbines - we did mostly residential induction generators, but some eventually were scaled up to about 60 kW; and some off-grid installs - for a number of years, my bias is to have the simplest, most robust equipment on the tower.  Electronics, rectification, regulation, monitoring, diversion, protection and controls can all be done on the ground, and under cover.  To me this is preferred.

Our turbine, it is by no means perfect, but I like that fundamentally it has three moving parts on the tower.  The rotor turns, the machine yaws, and the tail hinges, or furls to protect things.  All this happens without any signals or sensors or wiring.

The power pitch mechanism that Frans designed is very elegant, clever, and precise.  And, I only wish I had some of his skills.  It does however, introduce a great deal of complexity, particularly on the tower.  Where we live most turbines have to up 80-120' to work well.  So, any added maintenance is an important consideration.

mbouwer

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Re: Active Pitchcontrol
« Reply #944 on: July 03, 2020, 01:59:28 PM »
On that beautiful spot and with that background it is great that you can use wind energy in that way.
And I understand what you are saying.

Personally I like the complexity and the technique of modern windmills and that really appeals to me.

bigrockcandymountain

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Re: Active Pitchcontrol
« Reply #945 on: July 03, 2020, 04:53:30 PM »
I really love what you guys have done and what you are doing with active pitch control.  Keep doing what you are doing.  There are lots of us quietly watching your progress. 

I decided to build a side furling tail and fixed pitch prop for the reasons stated by kitestrings.  Also, i would add that building a turbine is a daunting task and adding another layer of complexity probably makes it too big a project for most people.

My observations from the last two years running my 13' turbine would be that it works very nicely and would only gain a very small percentage from variable pitch.

We are off grid here, so we don't really have a use for the high storm wind type production.  It is the slow, steady, 500w output that we really look for.  For grid tied people, variable pitch might be more worthwhile.

If you guys are having fun tinkering with variable pitch, keep on doing it.  I enjoy reading about it. 

SparWeb

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Re: Active Pitchcontrol
« Reply #946 on: July 03, 2020, 07:47:38 PM »
I'm tempted to weigh in... but have little to add to the good points made here.

About 10 years ago (has it really been that long??) I teamed up for a while with a fellow who lives nearby, building DIY turbine projects together.  His innovation was the pitch-control hub that he had developed.  While I was fascinated by the way his hub worked, it needed a lot of tuning to get it to operate in the right wind speed.  Each adjustment required a different torsion spring - adjusting the mass balance was not enough.  For his part, he was not interested in wood carving as I am, nor doing the math to get the pitch and curve just so. He preferred to buy simple fiberglass blades, which undoubtedly is less expensive than what I do.  It has taken me 3 generations of hand-carved cedar blades to get the right generator-blade match, which is not too different from his iterations of torsion springs needing trial-and-error.

Here I find the active pitch-control to be preferable to a passive one.  It solves the tuning difficulties with a control system at ground level.  Now the issue becomes reliability of a system distributed between an actuator motor in the nacelle, and electronic devices at ground level.  Franz made it fail-safe so I call that a win.  Anyone with the needed skill could go further and add redundancy and robustness to make it last a long time.  This thread deserves all the attention it's received and I have referred to it many times over the years when the subject comes up.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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mbouwer

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Re: Active Pitchcontrol
« Reply #947 on: July 04, 2020, 09:26:22 AM »
There are wind energy enthusiasts on this forum who already have a turbine and use wind energy. That in itself is quite an achievement I think.

They are the ones who have experience and are now the ones who react in this discussion. Thanks for that.

But how can we focus on and involve builders who want to concentrate on inventing, designing and building active pitch control?

mbouwer

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Re: Active Pitchcontrol
« Reply #948 on: July 08, 2020, 02:54:28 PM »
Active pitchcontrol can also make a small turbine quiet and safe.

This topic started here about 10 years ago, but it seems that it does not inspire anyone to apply it.
Or even to discuss methods on this forum.

But let's be in no hurry:

It also took the professional windmill builders a very long time before they all understood they needed ajustable blades.

mbouwer

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Re: Active Pitchcontrol
« Reply #949 on: December 25, 2020, 11:57:10 AM »
Happy New Year to Midwoud and all other windmill friends.
And perhaps in 2021 we together will find simpler manufacturing techniques to apply pitch control.

Adriaan Kragten

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Re: Active Pitchcontrol
« Reply #950 on: December 26, 2020, 04:28:24 AM »
Pitch control has been discussed in several of my public KD-reports. It is described in KD 437 of the VIRYA-15, starting at chapter 6, in KD 622 of the VIRYA-5 starting at chapter 9 or in KD 654 of the VIRYA-3.6PC starting at chapter 6.

mbouwer

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Re: Active Pitchcontrol
« Reply #951 on: December 26, 2020, 09:57:11 AM »
Nice descriptions. And it would be nice to also consider the system, with external energy source to steer, as applied by Midwoud on his Piggott.

midwoud1

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Re: Active Pitchcontrol
« Reply #952 on: July 23, 2021, 06:57:38 AM »
Active pitch control   14220-0

Adriaan Kragten

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Re: Active Pitchcontrol
« Reply #953 on: July 24, 2021, 03:42:03 AM »
Pitch control systems can be divided into two main categories A and B and each main category can be divided into several sub categories with each different mechanical constructions. Every category has certain advantages and disadvantages. As all pitch control systems result in a complicated hub construction, they are normally only used for rather big rotors.

Main category A
For this category, the movement of the blade around the blade axis is steered by the aerodynamic moment, by a moment caused by centrifugal weights or by a combination of both. Both moments increase with the square of the rotational speed. These moments are counter balanced by a moment caused by a spring and this spring moment keeps the blade in the normal working position up to a certain rotational speed. One can use positive pitch control for which the blade angle is increased or negative pitch control for which the blade angle is decreased. Negative pitch control is also called active stall. The aerodynamic moment around the quart-chord point has a direction such that the angle of attack is decreased and so the blade angle is increased. So the aerodynamic moment supports positive pitch control. The main advantage of this category is that it works automatically and that no external energy is needed to activate the system. The main disadvantage is that the pitch control system can't be used to turn the blades about 90° to the vane position for which the rotor stops. Another disadvantage is that the system works only nicely if the bearings of the blade rotation have only a little friction but as the bearing load is rather high, this is difficult to realize, especially if plain bearings are used.

Main category B
For this category, the movement of the blades is coupled mechanically such that there is a shaft in the center of the rotor which is moving forwards or backward. The movement of this shaft is activated by a hydraulic cylinder or by a linear electric motor. The movement of this shaft can be steered by any signal like the wind speed, the rotational speed, the power, the temperature of the winding of the generator, vibrations or whatever. A computer is required which transforms the signal into the right movement of the central shaft. The main advantage of this system is that any signal can be used to activate the pitch movement. The system can therefore also be used to stop the rotor if the blade can be turned about 90° to the vane position. This system can also be used to facilitate starting of the rotor at increased blade angles. The main disadvantage of this system is that some energy is needed to activate the central shaft and so the system isn't working automatically. So if something goes wrong with the computer or with the energy supply, the system is no longer active and the rotor stays in its normal working position. This may result in too high forces in the blades at very high wind speeds resulting in destroy of the rotor. This disadvantage can be cancelled if the blade is always pushed back by a spring to the vane position but this requires a rather strong hydraulic cylinder or linear electric motor to counter act the spring moment for the normal working position.

More information about this subject is given in chapters 6 - 14 of my public report KD 437.

kitestrings

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Re: Active Pitchcontrol
« Reply #954 on: July 26, 2021, 03:03:40 PM »
There are a couple of related influences, some discussed much earlier in this thread, but active pitch mechanisms usually result in a heavier rotor assemblies.  As much of this weight is added closest to the plane of the blades, it may also require a more robust frame and/or yaw assembly to support it.  It may require additional conductors and slip-ring poles.

Adriaan points to the idea that for the system (Category A) to work well depends on the blades having relatively low friction about their axes.  I think this is true of both categories, and to achieve this depends not only on the selection of the bearings, and related components, but also on regular maintenance of those components and points of contact (cleaning, lubrication, removal of corrosion).  We recently discussed some of the older Dunlite turbines.  Although they were a very heavy, robust build (Cat. A type), they often had severe damage over time if they were not maintained.

I do agree that an advantage of the Category B designs is that you also have the added potential of shutting down the turbine.  This feature is a significant advantage if there are hurricane force winds on the horizon, or say if there is icing, or a need to climb the tower for inspection or maintenance.  In my experience this is one of the best ways to avoid problems; wait out the really rough stuff.

With either category, you will have introduced more complexity.  Most of it up on the tower.

Adriaan Kragten

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Re: Active Pitchcontrol
« Reply #955 on: July 26, 2021, 08:25:41 PM »

Adriaan points to the idea that for the system (Category A) to work well depends on the blades having relatively low friction about their axes.  I think this is true of both categories, and to achieve this depends not only on the selection of the bearings, and related components, but also on regular maintenance of those components and points of contact (cleaning, lubrication, removal of corrosion).  We recently discussed some of the older Dunlite turbines.  Although they were a very heavy, robust build (Cat. A type), they often had severe damage over time if they were not maintained.

With either category, you will have introduced more complexity.  Most of it up on the tower.

In my calculations I have found that the aerodynamic moment is rather small. The moment of centrifugal weights will also be rather small if not very large weights are used. So the friction moment of the bearings must be low for category A systems if you don't want to have large hysteresis in the pitch movement. It is true that the friction moment may increase if the lubrication of the bearings becomes worse after certain time. It is therefore very important to use good seals for the bearings although seals give some extra friction.

Most safety systems of category B use hydraulics to activate the movement of the central shaft. Very high forces and therefore very high moments can be executed by hydraulic cylinders. So for category B, it isn't very important that the bearing friction is low.



kitestrings

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Re: Active Pitchcontrol
« Reply #956 on: July 27, 2021, 10:09:09 AM »
Yes, and it is not just the bearings to consider.  The blades have to rotate in unison, so there is linkage between them.  There is also the center shaft and slides of some sort that limit the range of motion.  It may go without saying, but the entire mechanism needs to be protected from the elements, and even condensation can introduce corrosion or frost.  I've had sliprings on my engine driven generator glaze over or stick the brushes momentarily, preventing output, when the wrong combination of humidity and and temperature drop have combined.  (Stop and restart it, and all is good once a bit of heat is present).