Helicopter Force Trim building ..

[Triggerhappy]

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:


Rough cut parts for trigger mech:


Cyclic stick handle with push-buttons and coolie hat:



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

[Prof Bill]

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]

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

[Triggerhappy]

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..!

(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]

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_...nterfacing.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_ped...e_feedback.htm

[Triggerhappy]

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_...nterfacing.htm

http://www.simprojects.nl/rudder_ped...e_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]

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]

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/d...ndamentals.htm The same as your hardcopy primer?

[Roland]

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]

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.