Helicopter Force Trim building .. [Archive]

Triggerhappy

05-25-2008, 10:16 AM

I am building a fully funcional KA-50 Cockpit for the forthcoming Digital Combat simulator' KA-50.

I am building the Stick from a modded old Thrustmaster grip and the Collective and rudder from bottom..

BUT.. I want the mechanical part of the helicopters Force-trim to be functional with my Opencockpits cards. So when I hit the Trim center button, the stick and pedals mechanical centerpoints are reset to the current one..!

My only problem so far is HOW..?

I have thought of using a solenoid to open some kind of "brakepads" on the axis and allow it to return to its spring loaded centerpoint. And then "closing" the brakedpads again. Leaving the cyclic and rudder in it's current position?

Any good ideas fellows?

DCS Site:
http://www.digitalcombatsimulator.com/

Here's a my updates so far:
http://forums.eagle.ru/showthread.php?t=27270&page=28

spitfire9

05-26-2008, 01:21 AM

I have also toyed with the idea of building a helicopter pit for Black Shark.

The videos look awesome,, especially the start sequence where the sim pilot uses Trackir and touch screens to go through the realistic start !

A couple of years ago I built a collective for use with the helicopters in Fs2004 and it works great.
I've been looking forward to trying it out with Black Shark for quite some time now. hope its released soon.

As for the force trim,, I have a friend that also cruises this forum and he has come up with a idea of using a small electric clutch ( I'm not sure which website he found them on but I'll ask ) to simulate the elevator force on a fixed wing aircraft.
The clutch would be interfaced with an IO card that would allow the clutch to get input from the airspeed value. The higher the airspeed the more the clutch would squeeze the elevator axel. This should give a fairly accurate representation of how the yoke feels sloppy at slow speeds and more firm at higher speeds.

Maybe something like the above could be used for force trim??

I remember a previous thread where force feedback was discussed at length ,, with some amazing ideas from quite a few of the guys.

Trevor Hale

05-26-2008, 08:13 AM

Hey there,

I am not sure if it would work for you, however, what about using the base from an old Force feedback Joystick? Could that not be implemented somehow? The Force feedback could be enabled or disabled through the OC Interface.

Just a thought.

Trev

spitfire9

05-26-2008, 01:08 PM

I tried building an extended stick using an old Logitech Wingman FFB stick.

With anything heavier than the small light plastic (original ) grip,, the FFB motors are just too small to get any kind of feedback.

Perhaps someone with more electical knowledge than me could hook up bigger motors and use the original sticks circuit board. That would work .

With bigger motors,, I'm sure resistors and proper cooling would then be an issue.
Also an issue would be Fs9 (and I'm sure FsX) has such poor FFb files,, compared to ,,say,, IL-2Fb.
Black Shark probably would have good force feedback although I haven't heard either way.

When flying helicopters in Fs9 I use a Microsoft Sidewinder with FFB but I use a small app called "RTC"that was originally made for race car sims that don't have FFB coded in the sim. It gives an FFb stick (or wheel) a good center spring feel and a steady thumping at any freq. that you choose.
That feels quite realistic when flying choppers. Much more so than the Microsoft fixed wing FFb files.

Trevor Hale

05-26-2008, 02:01 PM

Yeah, I was using a Microsoft FFB JS and it had larger motors then what I have seen on the logitech equipment. But when you install the leverage of a 20 Pipe on top of it, it may not hold the weight.

Good thoughts.

Trev

Mike.Powell

05-26-2008, 06:53 PM

I believe the force trim system that Triggerhappy is referring to is different from force feedback. I think it's basically a spring centering force with an adjustable center point.

If you look at pages 36 and 37 of the Bell 412 product data manual there is a description of the key elements of the system. (http://www.bellhelicopter.com/en/aircraft/commercial/pdf/412EP_PDB_2002_r1_web.pdf)
From the manual: "The force trim unit, acting as a spring-loaded centering mechanism, provides an artificial feel for the pilot maneuvering when desired".

There is a magnetic brake that allows the pilot to release the "fixed" end of the springs, resetting the zero point of the centering force.

I don't think it's necessary to incorporate the OpenCockpits card at all. In operation, the magnetic brake is operated by the pilot pushing a button on the cyclic. There's really no reason not to do something similar in the simulator.

The challenge here is to find an affordable brake mechanism that has little or no backlash. Something like an electrically operated automotive air conditioning clutch or a small tractor power take off clutch might serve as a starting point. The problem with them is the expense.

I'm inclined to think that a DIY magnetic brake is a possibility; however, there's probably a ready made solution somewhere. Thoughts??

Triggerhappy

05-31-2008, 10:00 AM

I have the same experience with extending the stick of a FFB joystick myself.. It just don't seem to be powerfull enough to really make a difference.

And since I am building the stick to resemble the KA-40 stick with the trigger mechanism made out of aluminium. It will have to at least give some feedback with this added weight..?

However I have come across some sites:
http://www.lbodnar.dsl.pipex.com/Images/LBodnar-FFB.jpg
http://www.lbodnar.dsl.pipex.com/ForceFeedbackController.html
A Force feedback controller?
http://www.simprojects.nl/images/Logitec_FF.jpg
http://www.simprojects.nl/adding_force_feedback.htm
Adding force feeback to a DIY Yoke from Logitech FFB joy..
http://www.simprojects.nl/images/FS_box_complete.JPG
http://www.simprojects.nl/flight_stick.htm
or a flightstick..

http://buggies.builtforfun.co.uk/Sim/Images7/Test-Rig.jpg
http://buggies.builtforfun.co.uk/Sim/force-feedback-3.html
A totally DIY adding of FFB to a stick..

So far the solution from the simprojects.no site looks promising? Anyone tried this approach to the issue?

Westozy

06-08-2008, 07:19 PM

Hi Triggerhappy,

My apologies mate I appear to have missed this thread but the other boys seem to have covered more than I know, well done chaps!

Gwyn (Westozy)

Prof Bill

06-16-2008, 06:50 AM

It would appear that I am joining this thread a little late!

However there is a neat piece of software from Dirks Software that may well address many of the implementation possibilities that some are considering
http://www.fs-force.com/

There is a Demo downoad available.

You can really play around and very quickly build your own profiles.
I have a twin yoke in a Baron 58 forceback driven by a modified Logitech Wingman Board, two "H" Bridges that can deliver 5 Amps (in an aircooled aluminium case) for X and Y axis FF manipulation.

Bill.

Prof Bill

06-16-2008, 10:24 AM

Triggerhappy

06-20-2008, 05:53 AM

Apologies All,

I should have added some pictures that might help!

The first picture is the Logitech board with two "H" Bridge devices attached in it's development stage.
The second picture is the FF Motor etc driving the Aileron FF.
The third picture is the two FF Motors etc driving the Elevator and Aileron Yoke etc..
The third picture is the FF Motor etc driving the Elevator.

There are other pictures of the assemblies around if needed!

Bill.

That's what I call a sweet setup..! Nice, Clean and slop-free..!
But some questions pop up in my head as I gaze in awe at the pics. Are you using TWO FF motors per axis? Is this because you have a dual control setup in your pit or just simplyfied way of increasing the sum of the FF motors output?

Or am I mistaken and you actually use larger FF motors AND two of them?

Do you have the schematics for a H-Bridge circuit? And the specs of the components you use to build them? Allthough I try to learn electronics as fast as I can (I knew NOTHING before starting my Ka-50 Pit), I'm not quite sure how this works. I could off course set myself down and learn it, and to be honest I probably will.. But if you have a system that works I'll just go ahead and do as you did.. No point in inventing the wheel again and again and again..?

My FFB stick will have to have the FF motors connected by pushrods and bellcranks like yours. But I have to fit it all in within a space of 150mmX180mm areal.!

And the motors will have to pull quiote a heavy load being that the cyclic stick is casted in Fibreglass with some heavy push-buttons and an all metal trigger mechanism. Donnu the total wheight of it all with wires and stuff yet. But I'd rather use FF motors that are to big, and turn the FF settings down. Do you agree?

Stick with finished Triggermechanics in aluminum:
http://byfiles.storage.live.com/y1pXMutyGoQ-MJh5CbCmATvqysMpdr5DpWTlQcmr0Nm_IsWHjXk1sCTHuNAQOBjcEPclHrqRL0wFsU

Rough cut parts for trigger mech:
http://byfiles.storage.live.com/y1pXMutyGoQ-MK5O9ALXDfU_hQJYvINZ6z7EQGM88Yp1pwQ_3fF-UDETg9gfsl_dSljtEI-GA_JDB0

Cyclic stick handle with push-buttons and coolie hat:
http://byfiles.storage.live.com/y1pXMutyGoQ-MI4nnZ63YrT9KqptclwFTHAC9kQezEd-skN8_hZLbhMy6khINZIxAPS9eahRm841qs

And what is that thin wire that runs from the axle just beneath the slider pot and back under the panel for?

Prof Bill

06-20-2008, 02:36 PM

Hi Triggerhappy,

Many thanks for your compliment!

In this particular setup there is only one motor for each axis drawing a maximum of 1 amp at 12 volts peak and probably 200ma sustained.

Both yokes are mechanically linked!

I used a couple of H Bridge chips straight off the shelf made by Allegro described as a 3966 Dual Full Bridge PWM Motor Driver(up to 30 Volts).
These are rated at 650ma continous and 750ma peak but as they are PWM driven you can be adventurous with the specifications. I have never known a failure. These are easy to solder into the Logitech board as you can see from the picture. The have a copper heat sink stuckon top.

I had a student do quite a bit of experimentation and believe it or not you really do not want big meaty motors as their inertia hides the subtlety of the more interesting and impacting feedback vibrations.

The best H Bridge is one that drive a medium sized "stepper motor" and I will look out some specs for you as I have many in my retirement laboratory.
The motor does not have to be a stepper motor.

L6203 DMOS Full Bridge Driver is an 11-pin flat package IC with mixed bipolar, cmos and dmos technology. It delivers 3A output current at supply voltages up to 52v with very high efficiency and fast switching speed.
Each side of the bridge is controlled by a separate logic input.
It is cheap to buy!

There is little or no design and minimum build in the setup in the pictures so do not despair in terms of technical complexity in the build or software!
The hobby is about integrating items and components so do not waste time
on trying to learn a new skill that could take up a disproportionate amount of your time!

I am away for a few days on a soiree up at Oxford (literally heading out the door now) but when I return I will come back to you if you need help.

Bill.

zenandzen

06-21-2008, 01:50 PM

Triggerhappy

06-22-2008, 08:51 AM

Chaps.......
just dropping in on the back end here;
did someone request a source of electric clutches smaller than a tractor takeoff?
You could look at photocopiers either wrecked junkers or source new parts from somewhere.
Many ,many d.c. clutches in copiers & all sorts of sizes too.
All the way from the small variety that fit a 1/4" shaft with a flat (some call them 'D shaft') to big babies that may indeed rival a tractor takeoff.

Just a thought from a retired copier tech.
Cheers
Gerry

All rise For Gerry.! YOU 'THA MAN..! :D:D

(edit: I originally was just about to post this with the heading "All rice for Gerry.." Guess I should have paid more attention in school.. LMAO)

I just love it when guys come up with goddarnit just blilliant ideas like that..! You just solved my Forctrim pedals dilemma..!

Anyone have any thougts on using electric cluches as replacement to servos/steppers and connect to "off the shelf" electronics from a FFB stick?

Roland

06-22-2008, 04:30 PM

Not sure whether this will be any help as it mainly deals with fixed wing aircraft, but I recently did some more work on force feedback, this time with DIY interface. See http://www.simprojects.nl/diy_force_feedback_interfacing.htm
I applied this to rudder pedals and works satisfactory. It has pedal force related to speed, and it is also possible to offset the center point with DC value derived from trim, or add dynamic signals. Accuracy may not be perfect, but it's simple and straightforward.
The rudder pedal can push some 13kgf, which feels OK.
see http://www.simprojects.nl/rudder_pedals_with_force_feedback.htm

Triggerhappy

06-22-2008, 09:50 PM

Not sure whether this will be any help ... Bla bla bla bla interresting stuff actually, but not my point, witch is..
...but I recently did some more work on force feedback, this time with DIY interface.

Man you did'nt not do SOME work on the subject. Your actually the ONLY real DIY sollution I have found..!
I mean I might not be as good as my inner-self claims at surfing the Net, and I'm pretty sure you guys building "too-the tea", full functioning copies of twoseater heavies probably all have'em.!?

But your's is the one site i have found giving simple and instructive info on .. artiscic brake build up tension.. Not the consept of FFB pro's and con's of servos, steppers or magnetic brakes..

But the real tough one..! The number one question..?..:

How the **** are you gonna tell all us morons how FFB ACTUALLY WORKS..!

(And thowing in a side-dish of "..and this is by the way how it is all put it all together, by stuff you probably have in your garage or someone elses.. Oh yeah... and see..! it really does work..!?")

It really works for me mate..! It really does..! Actually I'm pretty sure that your site greatly influenced me in taking the plunge and think:
"Suuuure... I could make that..!? ...Couldn't I? ...for sure..? I mean..? He did..?"

And I'm not being sarcastic..!
So you've at least one fan.. Not even sure I would want me for a fan, but what the ****..! You've got no say in the matter, I think bouldly to myself..! c",)

Check Rolands site out on:
http://www.simprojects.nl/diy_force_feedback_interfacing.htm

http://www.simprojects.nl/rudder_pedals_with_force_feedback.htm

. . . I'm still confused about one thing though? A H-Bridge is not really an amplifier is it?
It seems more like a bigger controller getting signals from the smaller one, and just putting more "juice" out to the motor?

Or should I just go to bed..... ? Well now it doesn't really matter 'cause roland has allready done it and I can copy him..! See it works..!

Prof Bill

06-23-2008, 10:20 AM

Hi Triggerhappy,
Sounds as if you are as enthusiastic as ever!
To help answer your question on how you can easly get to grips with Force Feedback I would suggest the the following Primer.

A FORCE FEEDBACK PROGRAMMING PRIMER by Louis Rosenberg Ph.D

This was the definitive manual (easy reading) in the early days and laid the ground rules for Force Feedback. It was published by Immersion Corporation http://www.immersion.com/ as it was then called who are the leading world players in this area especially in the games and medical virtual area.

The primer does not have an ISBN number and may be out of print but I am sure you
could advertise on EBAY and perhaps locate one.

This one very early primer layed down some of the ground rules in Force Feedback Design and Haptics.

The Immersion site is well worth exploring as it will give you some good leads.

Bill.

Mike.Powell

06-23-2008, 12:07 PM

Force Feedback I would suggest the the following Primer.

A FORCE FEEDBACK PROGRAMMING PRIMER by Louis Rosenberg Ph.D

Bill,

Is the online tutorial here: http://www.immersion.com/developer/downloads/ImmFundamentals/HTML/ImmFundamentals.htm The same as your hardcopy primer?

Roland

06-23-2008, 01:53 PM

Sorry to be (partly) responsible for the pitbuilding bug. Unfortunately there is no remedy, and the symptoms only seem to get worse.....

. . I'm still confused about one thing though? A H-Bridge is not really an amplifier is it?
It seems more like a bigger controller getting signals from the smaller one, and just putting more "juice" out to the motor?

An H-bridge circuit is just a circuit where the load (motor) is connected between two bridges. It is therefore also called BTL or Bridge Tied Load. In zero drive condition, the 2 bridge outputs both sit at 1/2 the supply voltage, so zero voltage over the motor. When drive in one direction increases, one bridge output goes down, while the other goes up, and visa versa for the other direction. In this way, you can produce a voltage over the load that is at maximum: + or - the full supply voltage. In order to make this possible, each bridge has to be able to source or sink current. In my FF motor drive, I used 2 transistors for each bridge, in a push-pull configuration. It is simple, and can deliver high current, but has the drawback that it is dissipating a lot of power when the motor is running half speed. For FF motor drive, this is not so bad as power levels are relatively low. Max 50 ~ 60W of dissipation, and not continuous, all you need is big transistors and a big heatsink. So my FF drive buffer is really nothing more than a very simple 100W audio amplier, for producing slowly varying DC voltages to the load.

For higher efficiency, (smaller or no heatsink) you can use switch-mode output stage (similar to the now popular "digital" class D audio ampliers) It's usually a more complex circuit. They produce a high-frequency square wave, where the average value of the squarewave (that the motor sees) is again a slowly varying DC voltage. Regardless whether the bridge is push-pull or switch-mode, it is still called H-bridge when the load is connected between the two bridges.

In my case, the choice of components often depends on what I find in my (rather big) junkbox. So the circuits are not always that elegant from price / power design point of view.

Prof Bill

06-23-2008, 03:52 PM

Bill,

Is the online tutorial here: http://www.immersion.com/developer/d...ndamentals.htm The same as your hardcopy primer?

Hi Mike,

The short but unsatisfactory answer is not quite!

The primer is a seminal document in terms of when it was written and Rosenberg discusses quite a few ideas in terms of "temporal components" and what was fashionable at the time but not executable easly.
Enabling technology and the medical interest has brought much more practical focus to the whole area.

The reference you have linked to http://www.immersion.com/developer/d...ndamentals.htm is a "lite" version of what works easily now for most and is covered in the primer which has less sophisticated diagrams. What I personally like about the primer now (published in April 1997) is that Rosenberg happened to get things right in terms of system design and integration for Haptics.
I am happy to loan you the primer if you wish as I have people travelling to and from the US with regular monotony.
Incidently I have your "works" here on the bookself and the they are frequently referenced.

Bill.

Triggerhappy

06-27-2008, 05:31 PM

Mike.. Roland.. Prof. Bill... You guys have no idea how mch you have helped me..

I am now the proud owner of a brand spanking new Logitech Force 3D Pro that I'll hack the FFB electronics ot of and use for my own stick.

I'll be sure to update you as it progresses..

And Mike..? Your book... well... It has found it's place right next to where I am absolutely sure to have sufficient quiet to dive into all the info..! Thank you..!

Ps. Don't even thing that I'm done bugging you on the FFB amplifying though..! just need to finish the Stick's trigger mechanism first. So by sunday you'll have me here going on and on and on again..:roll:

Triggerhappy

11-29-2008, 09:08 PM

I took the FFB mechanics out of a Sidewinder Force Feedback 2 USB stick and removed the handle with my home-made KA-50 Handle and switches:
http://img155.imageshack.us/img155/708/ka50forcefeedbackjoystiou2.jpg

http://img368.imageshack.us/img368/6030/ka50forcefeedbackjoystihn8.jpg

The Handle is an old TM stick with my own KA-50 Box on top made from a handcarved foam plug:
http://img201.imageshack.us/img201/4177/ka50hocascyclicboxmold2eq2.jpg

http://img160.imageshack.us/img160/5894/ka50hocascyclicboxmold7sl3.jpg

http://img84.imageshack.us/img84/310/cyclicstickafterfirstsaev6.jpg

http://img329.imageshack.us/img329/5320/cyclicstickafterremovinle3.jpg

http://img114.imageshack.us/img114/7471/cyclicsticknearingreadyec8.jpg

http://img98.imageshack.us/img98/5032/cyclicsticknearingreadyzs0.jpg

The Trigger mechanism is also made by me.. I wanted it to look and work like the real thing:
http://img219.imageshack.us/img219/1597/ka50triggermechanism31am1.jpg

http://img179.imageshack.us/img179/2273/finishedtriggermechanissm2.jpg

Still some work needed in this though.. :roll:

I have tested the Trim Function in DCS Blackshark with the new Cyclic Stick now.. And it works like a charm..!

However I will probably be replacing the motors with bigger ones like shown by Prof Bill in this thread (I will be bugging you for more info If that's okei with you?).

As I decided to use the buttons and coolie hat from the MS FFB Stick, I need to find out what the components in the small PCB inside the stick handle are?

The seem to be some combination of a 2to1 resistor/diode? Anyone have an idea of the values/function of them?

The reason I ask is that I (by mistake of course) used a much to high temperature while de-soldering the switches, and now some of the pads have come of..

So I might as well make a new and neater one..

Please help me out anyone, so I can start using it..:!: