We need a force feedback base badly...

[FIN_Centurion1]

Lovely project idea, I'd be eager to help in any way I can (though probably not much). I know there are some people on the HOTAS discord DIY channel thinking about force feedback gimbal design but I haven't seen any conrete designs or proposals yet.

[MilesD]

As title says,

Even if it is going to cost near to the 4 digits :(

It is becoming more and more important for some serius virtual flight.

 

Look what you started TaliG, Your post motivated me to finish an old project... hopefully.

 

@FIN_Centurion1, I am always up for suggestions and new ideas, no matter how crazy they sound. Fortunately, for this project, I have a quite a bit of experience with motion control systems, and I have shelves full of hardware well suited for this challenge. My CNC machines have been idle lately, so I am looking forward to using them again. Electronic work and coding can be be rewarding, but there is nothing like cutting metal and throwing nice chips.

 

Miles

[heloguy]

Whats up HeloGuy!!!

 

Your spot on with the design goals. A realistic force trim implementation is a critical design goal. I see a few minor issues with modeling the trim actuators and parallel servos outside of the sim, but I really don't see any other way to do it. I assume you only use the simulation trim to administratively set the trim to zero, and then all trimming is done electro-mechanically with the stick.

 

When I am a bit more freed up from PointCTRL we should get up on discord voice, or phone. Given your "Night" job, I would love some more input. My helo advisers are mostly UH1 and S76 . We are getting together in January for 3 days, so I hope to have some working prototypes to test, adjust, and verify different control loading and effects. An air-frame dependent ETL vibration is a big one for me.

 

Thanks for the input, and I hope to talk to you soon.

 

Miles

 

I'd definitely love to help!

 

Right now, the sim just reads the stick like a regular spring based stick, and I trim the direct drive motors using the hat switch, and buttons on the grip. The sim doesn't know it's any different, since I don't map any trim switches for any aircraft in game.

 

This presents a small problem with the Ka-50, since the heading hold won't capture a new heading unless you press the in game 'trimmer,' but the work around is just shutting off heading hold, and using the pedals like an actual pilot.

 

I'd like to use the heading hold function, but there seems to be a bug with the "Joystick without springs and FFB" option. See here:

 

https://forums.eagle.ru/showthread.php?t=252975

 

True FFB integration into DCS would be ideal, but the work arounds with the Brunner stick are still way better than using a spring based stick. Hopefully one day Brunner's FFB integration will not be so hard to get working.

 

In the meantime, I'll try to hop on Discord one of these days on the PtCtrl channel and chat about things.

[RustBelt]

Thanks for that RustBelt, Are you using alternative dc motors with your FFB2/Warthog or the stock ones?

 

Miles

 

Still the stock motors. I've not found any really solid how to level discussion on motor upgrades certainly not ones with concise motor specs/part numbers, and really as long as it's still plastic gears it's going to still feel a bit crunchy. My longterm goal is to gut the FFB2 circuits for a belt drive yoke when a good FFB stick finally comes to market. I'll want better motors for that.

[MilesD]

Still the stock motors. I've not found any really solid how to level discussion on motor upgrades certainly not ones with concise motor specs/part numbers, and really as long as it's still plastic gears it's going to still feel a bit crunchy. My longterm goal is to gut the FFB2 circuits for a belt drive yoke when a good FFB stick finally comes to market. I'll want better motors for that.

 

Thanks for the info, it sounds like you have a good plan. I have an the old gameport version of that stick that I never used, but I took it apart once and as l recall they were standard 775 brushed motors with helical gears. I think the problem with putting bigger motors in that system is it would probably increase detent torque making the stick hard to initially move.

 

If we were able to source larger coreless, or skew wound motors it would help, but they both have less low speed torque.

 

I have used several methods to overcome the detent torque of the larger industrial motors I use. Some more successful than others, all of the wins used a form of pressure sensing on the control stick.

 

Anyway, the initial static friction and magnetic detent torque are the number one factors that kill the flight control feel for me.

 

Miles

[Thadiun Okona]

Still the stock motors. I've not found any really solid how to level discussion on motor upgrades certainly not ones with concise motor specs/part numbers, and really as long as it's still plastic gears it's going to still feel a bit crunchy. My longterm goal is to gut the FFB2 circuits for a belt drive yoke when a good FFB stick finally comes to market. I'll want better motors for that.

 

 

Roland van Roy figured this out and has good documentation if you want to do this. The stock circuit can be made to run up to 400% the stock torque by swapping some transistors and adding some caps/diodes/resistors. It works.

 

 

 

http://www.simprojects.nl/ms_siderwinder_ff2_hack.htm

 

 

 

As to motors, he has guidelines on motor selection. For one you probably want a brushed DC with a skewed armature to reduce magnetic cogging. Beyond that you select them based on the voltage drop at full load using Ohm's law. You want the voltage drop to be 12v at full power. I'm making such a mod now and have settled on 38.8v Lo-Cog Pittman 14203 motors (about the size of a coke can and have skewed armatures), which also need 25w 1/2 ohm resistors to bring the voltage drop to close to 12v since the terminal resistance was a bit low.

 

 

 

My ideal motor would be a 48v Pittman 14204, a bit stronger and has the correct native terminal resistance. Pittman motors are not cheap new but can be found as surplus if you have patience. I paid $60 for a pair of 14203 recently. Using a 25:1 belt drive for power transmission (5:1 into 5:1).

 

 

I currently run a modded MSFFII using the stock motors running at double the power by halving the resistance in the current sensing circuit and a 24v 3a psu to supply them with full power. Much stronger than I expected it to be. My gimbal is custom for my sailplane cockpit and pitch axis is 50mm longer than roll, but I kept the stock motor/gear assy's. Printed a glider grip and made a carbon fiber/printed elbows stick to achieve a full length offset stick that closely replicates typical sailplanes. This iteration of the stick is just to tide me over until I finish the one with the Pittman motors.

Edited October 26, 2019 by Thadiun Okona

[JoeyJoJoJunior]

and a 24v 3a psu to supply them with full power.

 

Hmm, I did the resistor mod as well to double power. Are you saying you don't get full potential of the mod without PSU replacement? The PSU in the stick is internal right, so I guess you had to modify or replace the PCB?

[Fri13]

 

That is what I want, with a VKB compatibility. Let that be own base and VKB grip go to Blackbox with pedals (and throttle).

 

https://www.irisdynamics.com

 

No, I do not care about Thrustmaster compatibility as it is lacking behind features and possibilities.

[MilesD]

 

That is what I want, with a VKB compatibility. Let that be own base and VKB grip go to Blackbox with pedals (and throttle).

 

https://www.irisdynamics.com

 

No, I do not care about Thrustmaster compatibility as it is lacking behind features and possibilities.

 

That is a really impressive implementation of a proportional solenoid. (Edit: referring to actuators on their website) I tried doing something similar once with a sensorless RC outruner motor that I attached a encoder too. I think my micro controller was to slow, or the encoder did not have a high enough resolution. In the end, I really wasn't smart enough to make it work well.

 

I know a bit more now, and have some big BLDC motors with very high resolution encoders, maybe I will it a try again and add it to the test line-up. I think adding a flywheel for static inertia would be helpful when switching the poles quickly. Might try scraping the encodes if I can get really fast hall sensors.

 

Miles

Edited October 26, 2019 by MilesD

[TomVR]

I currently run a modded MSFFII using the stock motors running at double the power by halving the resistance in the current sensing circuit and a 24v 3a psu to supply them with full power. Much stronger than I expected it to be. My gimbal is custom for my sailplane cockpit and pitch axis is 50mm longer than roll, but I kept the stock motor/gear assy's. Printed a glider grip and made a carbon fiber/printed elbows stick to achieve a full length offset stick that closely replicates typical sailplanes. This iteration of the stick is just to tide me over until I finish the one with the Pittman motors.

 

I'd love to see a picture of that setup

[Thadiun Okona]

Hmm, I did the resistor mod as well to double power. Are you saying you don't get full potential of the mod without PSU replacement? The PSU in the stick is internal right, so I guess you had to modify or replace the PCB?

 

The stock psu might not even put out what the motors can drink with the stock value at max draw which is 1.4A @24vdc. Doubling the current draw makes them capable of accepting up to 2.8A. Not sure the rated output of the stock unit is but the input is 1A @ 120vac. My 3A psu draws 2.8A @ 120vac to produce 3A @ 24vdc using similar circuit architecture.

 

As to the psu being separate, while MS put them in the same enclosure the power supply is a discrete component so yes it's replaced. I'm not using the stock enclosure because my gimbals are a completely different form factor so it was not a huge leap from there. Even with the stock psu I was quite surprised how much more powerful the stick was after the resistor mod though. Unless you're holding both axes way off center (not a realistic flying condition), the one that's displaced more is getting more juice so in actual use the stock psu is likely fine but it seemed low hanging fruit to bump it up after coming this far :p

 

To that end I have a 7A psu that I'll be using to power my newer conversion with the Pittman 14203 motors which should equate to somewhere ~3.5Nm final drive. My estimate based on similar sized motors/draws of the stock ones with the 24:1 ratio is ~0.8Nm, so the simple resistor mod we did should bump that to 1.6Nm or so which seems plausible.

 

 

I'd love to see a picture of that setup

 

 

I'll try to get some pics tomorrow, it's still a wip but at this point is finally cohesive enough to see what's going on. I plan on doing a proper thread here on it once it's in its 'final' form. The gimbals are a combination of printed parts with bronze bushings pressed for pivots along with aluminum parts for mounting the motor assy's, using the stock pots for simplicity

Edited October 27, 2019 by Thadiun Okona

[MilesD]

@Thadiun Okona, Great stuff!!!, It sounds like you have been doing this a while.

 

Miles

Edited October 27, 2019 by MilesD
Spelling

[Thadiun Okona]

I'd love to see a picture of that setup

 

 

Here's a shot I just got after some bench testing a few minutes ago. I still have some wiring/soldering to do. It will have an enclosure and properly mounted boards soon but the important parts are all present and work nicely together.

 

 

 

I'm making a breakout board to connect the grip to the shaft using standard 2.54mm plugs/wires/boards. I'm retaining the led/photodiode circuit, but it will be mounted in the sailplane cockpit it was made for so the stick will be active if I'm sitting in it vs mounted in the grip.

 

 

 

 

 

 

Here's a link to an album that has more pics and descriptions: https://imgur.com/a/4PHsM3V I don't want to drift this thread too much by dumping all the images here and again will be making a proper thread for it here soon.

 

 

@Thadiun Okona, Great stuff!!!, It sounds like you have been doing this a while.

 

Miles

 

 

Heh, thanks, but mostly I have the advantage of riding the shoulders of giants like Roland van Roy, who has kindly helped me with other related projects in the past. At one point I came up with a new scheme for full homebrew diy ff which was tested to good effect by Roland, but once the MSFFII hack became viable it makes a lot less sense to reinvent so many wheels when a good effects library of DirectInput can be extracted and utilized to good effect by such inexpensive hardware

[TomVR]

I like the small counterweight you've got on the stick. Is the gimbal printed in PLA or something tougher?

[Schmidtfire]

I recently got a MSFFII and wow. What a great feeling it is flying with force feedback! Some modules work better than others (like the F-14). Not all have the "buffeting" sensation when stalling, but in general the feeling is good accross the board.

 

The sad part is loosing a lot of hats and buttons compared to flying with my Warthog. Will keep an eye on this project, because a high-end force feedback base would be a gamechanger.

[Thadiun Okona]

I like the small counterweight you've got on the stick. Is the gimbal printed in PLA or something tougher?

 

 

Thanks, the counterweight does a nice job keeping pitch balanced with the offset grip. I kept it all as light as possible so reduce the mass needed to keep it upright and can adjust the weight as needed.

 

Not sure if you saw the link to the album I started but it has more pics and descriptions under each one https://imgur.com/a/4PHsM3V

 

I just printed in PLA, however none of the critical load paths rely in its strength other than the 45deg elbows, so they were printed at 100% infill and have really thick walls. The base of the shaft has a brass tube to reinforce the fulcrum and there are printed bosses that engage the stock mechanism that have m3 screws running down the center of them. I might make an updated version in abs or petg but probably not since this is just my stepping stone stick before I build the 'real' one using motors the size of coke cans and a belt drive, though will retain the form factor and will basically be the same stick but on steroids

[MilesD]

@Thadiun Okona,

That is really some great execution. I like your design with the adjustable counter weight. Even with the large industrial motors I have been testing with, I found I still needed a perfectly balanced stick in both the x and y to achieve a light 2 finger feel of symmetry at the trimmed center position. I balanced my single axis test stick just like a RC helicopter rotor head.

 

What are you thoughts on open ended kevlar cord wraped and pinned around the motor shaft instead of gears or belts? I found it to be very effective. It also eliminated a double reduction of transmission to the control stick. I am curios if I am missing a reason not to use this method.

 

I will be picking up on an old design I started a few years ago using 3 phase steppers controlled as sensored BLDC motors. The driver will be purpose built for our unique motor control requirements.

When I get some time I will dig out the test fixtures and post some pics.

 

Thanks for sharing your awesome build.

 

Miles

 

Miles

[Thadiun Okona]

Thanks for the kind words Miles. Ironically using the shaft winding technique was my original starting place on this project and I designed a stick around it in 2008, though never got around to the actual build. With improvements in HTD (rounded tooth) type belt drives, notably GT2/GT3 (rounded tooth modified for better engagement under load) the most compelling reason imo to use shaft winding, the lack of tactile pollution, was no longer an issue. To that end, I switched to belt drive due to off-shelf components making one more part of the build accessible, especially now that printing is viable for the larger pulleys.

 

True it's not practical to achieve huge ratios without a double without or triple pulley setup, there's also a practical limitation on how small a shaft you can wind around (and hence size of final drive) before doing damage to kevlar with constant cycling. The other thing is you can't go crazy with drive ratios due to inertial influences. The MSFFII engineers chose 24:1, which seems a great tradeoff of power vs unwanted inertia from spinning armatures, though I haven't done any real testing yet to see how much is too much. At 24:1 the motors go through 2 full revolutions when moving the stick from stop to stop with the stock mechanism.

 

I do prefer kevlar family ropes to aircraft cable though, it's much less elastic... more than an order of magnitude! Steel aircraft cable stretches like 20% @ 50% the break strength whereas kevlar stretches 1-2% at the same mark. It's harder to work with for terminating cleanly and tensioning installations, but there are enough advantages to be worth employing solutions. For me it was in the zone of diminishing returns in the face of GT3 belt though since they behave so nicely and are easy to work with and I don't desire super high ratios. Being able to print the large pulleys makes it economically sound.

 

Here's a drawing of my shaft winding design from 2008 long before I knew now to use cad lol. That iteration had the pitch motor going for a ride, but mounted directly on the roll axis (with a miter gear) to mitigate its swinging mass. My current form factor has the roll axis moving with the gimbals and is near the axis but also augments the counterweight and after thinking about it, pitch is not operated vigorously enough for it to matter so the previous iteration was a solution looking for a problem. My new design is far more compact. I bought 1/4 hp Yaskawa 3ph ac servos/drives for this and had a full diy scheme for ff but now that msffii is hackable it's a silly wheel to reinvent but that was before Roland pioneered the mods. May still employ those solutions for ff pedals and possibly airbrakes down the road, but that's a whole nother can of worms :p

 

 

 

Edited November 1, 2019 by Thadiun Okona

[MilesD]

Hey Thad,

Isn't it great looking back at old notebooks. Its always interesting to compare initial drawings to final products years later. I also enjoy looking at the things we dreamed up, but never made. You have an artist touch, I cant draw anything without graph paper.

Thanks for the good info about the new belt profiles and cogging, My machines have a mix of HTD and GT belts.

 

I really don't have anything new to offer in the mechanical design department. You have more experience with the FFB joysticks than I. I did a 5 min sketch of the design I was thinking of using on this. I always use a anchored open ended belt on my machines. I like the kevlar winding because it eliminates the change of direction idler bearings that back-bend the belt with this partial pulley implementation. I also like the compactness of an 6" radius partial pulley that has an 12" effective diameter in terms of power transmission ratio.

 

Let me know if you see any holes in this implementation.

 

Thanks again,

 

Miles

Edited November 1, 2019 by MilesD

[shadowze]

+1 to this, really would love a force feedback base

[MilesD]

I like these FHT kevlar belts,https://www.sdp-si.com/ss/pdf/80502026C.pdf but the limiting factor is the pulley torque, winch is about half of what we would need. I didn't see a % of circumference tooth engagement the specs were written for, however with the back-bending design of the partial pulley system with idlers I think it would be significantly increased.

 

Just thinking out-loud for comments,

 

Miles

Edited November 1, 2019 by MilesD
Forgot the link

[Thadiun Okona]

I like these FHT kevlar belts,https://www.sdp-si.com/ss/pdf/80502026C.pdf but the limiting factor is the pulley torque, winch is about half of what we would need. I didn't see a % of circumference tooth engagement the specs were written for, however with the back-bending design of the partial pulley system with idlers I think it would be significantly increased.

 

Just thinking out-loud for comments,

 

Miles

 

 

 

 

Uhhg... just had a fully written reply wiped by a finger flub... second attempt

 

 

Nice truncation of your pitch pulley, I've also embraced a partial pulley design for my final drive to further reduce the footprint/form factor, though mine is applied to a double reduction where the first stage is full round but 4" dia. Whether cable or belt, the same radial relationships generate the same mechanical advantages so the ultimate size is still influenced by this. With cable you can only drive it with so-small of a shaft due to cable properties and with belts the lower limit is by tooth engagement (smaller drive pulley increases tactile pollution and belt wear). My planned belt gimbals will only be a 1/2" bigger all around than my current ms hack (6x6x5 enclosure) even though the motors are twice the size. After playing 'musical cockpits' for the last 10yrs I've grown an appreciation for things that are compact and self contained :p

 

As to pulleys/belts not allowing enough torque I think it's just a matter of selection. There are combos rated for more torque than it takes to rip our arms off, at least more than what's safe for a little baseball bat mounted by our privates. GT belts are rated at higher values of HTD due to the efficient tooth engagement by the modified design and are also quieter (lower tactile report). Pulley's limits are more determined by fastening type ie: set screw or screws (ok) or split-collar (better) or collet (best) but I'm starting simple with set scews since they're cheapest. If I have issues I can divot or cross-drill the shafts and permanently mount them, if that fails I can move up the food chain using standard options I can buy and make. Here's a neat chart comparing belts by type/size

 

 

 

 

I can't find a similar chart for the polychain belt version, but they are the type rated for high torque at low rpm that use the same pitches/teeth so there are better low speed options if powergrip is insufficient, but my belt driven ff simracing wheel uses powergrip and works like a champ, which is what sold me on modern belt drive capabilities. Here's a Gates pdf on polychain belts, which are similar but tailored for applications under 500rpm https://www.ahrinternational.com/PDF_catalogues/Gates/polychaindesignmanual17595.pdf (p25 chart shows 8mm polychain rated ~.8hp and 14mm rated ~6hp at 10rpm)

 

I fly irl and used to obsess over achieving 100% force value, which in most circumstances is pretty low but corner cases can be quite high for sailplanes but applies to most general aviation. Warbirds and big boys of course generate much higher forces but I scaled back my ambition after observing how readily the human brain accepts lighter forces. So long as they accurately resemble what my brain expects based on flight condition it's quite convincing. Same applies to motion of motion platforms... timely suggestions of accelerations that are short of full value, so long as accurate, are enough for your brain to accept. I worked for E2M Technologies for a few years, and got to build/play with high end belt driven electric ball-screw motion platforms rated at 3000kg (they make much bigger ones but switch to direct drive much beyond 3k and those weren't built at our facility). Their control loading hardware was all direct drive (didn't get to play with any but motors were yuuge), however my boss there worked on the Air Force One Blackhawk simulator some years back and that utilized (wait for it...) shaft winding for some of the ff power transmission :) Got to spend a lot of time picking his brain and talking shop which was helpful for adjusting my priorities.

 

Kinda rambling here I guess so to summarize I don't see torque limitation of belts as an issue, even for powerful sticks and my belt driven 6Nm Fanatec simracing wheel regularly tries to break my wrist without any tactile artifacts. You do have to select the belt type/pitch/width suited for the application though. In my case it's 3mm GT2 9mm (may use 8mm polychain) but a warbird setup might benefit from say 5mm GT2 15mm (or 14mm polychain) for example. Shaft winding is good too of course, and could be made compact with similar tricks if desired.

Edited November 3, 2019 by Thadiun Okona

[MilesD]

Hey Thadiun,

Thank you so much for your time and sharing your knowledge and extensive experience, and its not rambling at all, you are a wealth of great information. I assumed with high static loads the limiting factor with narrower fine pitch belt's would be shearing or skipping belt teeth because their lack of depth would enable them to cam out of engagement, but from your experience, its apparent it wont be a problem.

 

One of my CNC machines that I haven't gotten a chance to set up hard or soft limits on has big NEMA 34s and if hit a mechanical stop it skips teeth.

 

I had a good laugh at the the bat near the family jewels analogy! I didn't even think of that, must be cautions during testing.

 

Thanks for confirming that the Kevlar shaft shaft winding does not have any obvious "show stoppers", and it's interesting to know it was was used in professional simulators. It surprised me how it outperformed everything I tested. I did have a role pin on the shaft at center winding that anchored the cord.

 

I need to get caught up on PointCTRL, so I can dedicate more time to this.

 

Thanks again for sharing your insight and knowledge.

 

Miles

[Pinello]

@Tadiun, are you using that stick in Condor 2?

 

 

Are you guys plan to hack a MS FFB2 as controller?

 

 

This could be a (more costly..) alternative:

http://bffsimulation.com/BFF-FFB-System.php

http://bffsimulation.com/CL_Software.php

 

 

Its for x-plane and p3d, but there is a UDP interface there:

http://bffsimulation.com/Manual-CL-USB/Appendix_J_CL_Controller.php

 

 

For 3'partys (DCS..):

http://bffsimulation.com/CL_Controller.php

 

 

 

Its basically for yokes (he sells diy "kits"/instructions), but he seems to have tested with planetary gears and sticks:

 

 

 

He writes about this prototype:

"The reduction ratios are 8:1 on the elevator axis and 4:1 on the aileron. The pitch axis motor is mounted

on the elevator axis motor - a very simple mechanical arrangement which works pretty well"

The motors:

https://www.aliexpress.com/item/32775070208.html?spm=2114.12010612.8148356.14.41438234R32ddl

 

 

Edited November 16, 2019 by Pinello
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