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Old 01-18-2018, 10:13 PM   #341
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Quote:
Originally Posted by MetalGear_Honk View Post
Hi
looks interesting.
Are you using the Motors as counterweight?
And how do you simulate near Stall speeds (loss of control Authority)
how do you integrate the FFB communication in your controller?
And what controller are you using?
I have so many questions :-)
are you willed to share some more information’s with us?

MetalGear_Honk
The motors are not used as counterweight, one of the axis is sitting level because the motor is in-axis with the gimbal, while the other axis is tilted in the picture because the weight of the motor is pulling on one side. This is intended to be a floor mounted joystick with the rotation point somewhere halfway between the seat and the floor. There will be a counterweight under pivot point to balance the grip and to keep it neutral on all axis.

I was intending this as mostly a helicopter force-trim, but I think I can simulate control loading by moving the motor depending of the axis position.

Im currently using a overkill STM32L476RG (about 9$), I could use a cheaper micro controller but this kind of optimization is not worth it a the low production count sim equipment have (and I might only produce my stick... ). The controller is detected as a FFB stick and I can receive the command that DCS send to the stick. That code was done about 1 or 2 years ago so im a bit fuzzy on the details.

There are 2 hall sensor per axis, one of them is used to send the data to the computer without any backlash. The other sensor is used to read the position of the offset created by the motor, the difference between the 2 measure will be used to control the offset created when the cyclic is trimmed.

I also intent to link a set of FFB pedals with the same controller, this will enable force-trim on the pedal when the stick receive the trim command.

The board also have connections to read and send the button press of a Thrustmaster Warthog, I intend to intercept theses button press to be able to set a force-trim in simulator that does not support FFB.
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Old 01-19-2018, 11:47 AM   #342
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Hi
with the Liking up a FFB Paddle du you mean to add another USB-Class to the controller?
Or do you know a way to integrate more than 2 Axis into a FFB-Class?
And would it be possible to give me/us some insight in your code?
I would love to get a look at your effect calculations so I can copy those that I am not able to get working.

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Old 01-19-2018, 09:47 PM   #343
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For the pedals I was only thinking of faking the ffb and make assumption based on the commands received to the XY axis and send similar force command to the pedals. From what I read and remember DCS does not support 2 FFB devices, so only the stick will be properly detected as a FFB device, and I will simply add another axis on the USB controller to send the positions of the pedals.

This is mostly for force-trim on a helicopter, so when the XY axis will receive a different spring center command, I will also change the spring center on the pedals. Either that or I will intercept the trim button press on the stick and will change the spring center of the pedals that way.
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Old 02-18-2018, 08:30 PM   #344
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Quote:
Originally Posted by Thadiun Okona View Post
Actually I don't recommend using the driven pot circuit at all, or any other diy interface because it represents an astronomical amount of work and very limited usability. I recommend instead using a MSFFII modified to output 400% the stock torque and connect that to real motors using your own psu in the form of simply 24 power bricks. No idea what you mean by 'threat' lol.

As to shaft winding, as far as mechanical systems go you are not going to find much simpler an arrangement to construct, especially one with no backlash or cogging which are (or should be considered) deal breakers for what you are trying to do. Steel cable is subject to creep and stretch and would eventually need tightening however kevlar (Spectra/Dyneema etc) is not. Such a system would req little if any tuning and it would be pretty straight forward to incorporate a cable tension mechanism where it mounts on the bellcrank, or even little idler pulleys.

Steel cable is like a rubber band made of stabby needles though, where it elongates some 35% at break vs kevlar which is more like 3.5%. Kevlar also doesn't poke holes in your fingers and instead feels like a waxy shoelace. There are rl aircraft that use it over steel now in control circuits.

Best of luck whatever you guys decide...


I hate self-quoting, but it's relevant to my current thoughts and plans and it made more sense than editing a buried post...

Now that Condor2 (sailplane/soaring sim) is soon releasing(!), I'm really keen to get a force feedback stick working in short order. The Condor devs have MSFFII sticks and really use them to great effect (rl glider pilots that have tuned the game to that stick... I fly glides too and can they did indeed do a good job of it and have provisions for pedals too along with UDP output streams for motion platforms etc) here so it reinforces my inclination to use it as the interface vs rolling my own. For now I'm just soldering some resistors in a MSFFII to double the current with the existing hardware to run a longer stick, much like in this example.

Later I'm going to double it again (400% original current, like this example), which req upgrading some diodes/caps/mosfets and using my own power supply, in this case a 24v 7a power brick. I found reasonable priced/sized motors suitable for this, brushed 24vdc servomotors with skewed armatures designed to minimize magnetic cogging. Pittman Lo-Cog 14000 series have good form factors for this too.

My long winded preamble that makes it relevant to this thread that has different options for all of the above, is that I have revisited the idea of belt drive again for power transmission. After seeing how Fanatec uses belts in their excellent wheels it got me thinking. Then after looking at the cross-section of HTD belts with their semi-circular teeth it seems apparent why the 'zipper effect' is so minimal on their gear.



They don't use HTD but something very similar but one of the things Fanatec does that makes theirs behave so smoothly is use idler wheels to increase the contact area the belt is on the pulleys. Here's the pic that shows ~270deg of the pulley in contact.











Getting the wrap ratio really high like that will go a long way to minimizing the effect each individual tooth makes when coming in contact with the pulley, thus minimizing the tactile effect. This combined with the rounded tooth pattern of HTD belts should be subtle enough to be a non-issue for this application, so I plan on getting some HTD 3m x9mm belts/pulleys to build with. If it turns out to be an issue, I can always switch back to shaft-winding using the same hardware and COTS solutions get the ball rolling.

Another issue I've been considering which I brought up earlier was mechanical advantage ratios. Again looking to the MSFFII as a benchmark to draw from, I'm going to stick with their 24:1 ratio (+/-15 deg stick travel = +/- 1 full motor revolution). My thinking is this. Microsoft had real engineers really think their design through, including min/maxing torque advantage vs undesirable inertial effects. Although the motors I'm going to be using are bigger/heavier, torque equations scale linearly so the true min/max ratio would still be in the same ballpark, given similar motor construction so seems an ideal baseline. Unless I'm putting 2 and 2 together and coming up with 22 :p


TL;DR:
I changed my mind about belt drive in light of Fanatec hardware, and think 24:1 gear ratio MS used in the FFII is likely the ideal ratio as a starting point
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Old 02-19-2018, 06:57 AM   #345
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I think the belt is the way to go... there will be almost zero backlash. I thought about to redesign how the MSFFII works and adopt belts
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Old 02-19-2018, 11:08 AM   #346
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Those motors are expensive.
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Old 02-19-2018, 04:45 PM   #347
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Quote:
Originally Posted by 98abaile View Post
Those motors are expensive.
For motors suitable for FF they are quite reasonably priced, and because they are brushed they don't require an expensive drive to go along with them and can be told what to do by a modded MSFFII. By suitable I mean they have skewed armatures to reduce magnetic cogging (reluctance torque). This property is not a given for motors (uncommon in fact) but a key ingredient for force feedback because power needs to be smoooooth even though the motors are barely moving.

Once you get into applications that req high torque/low RPM you are no longer shopping for just any old motor that happens to fit or look good on paper. Also, Pittman makes a lot of these so they can actually be found as surplus or used, making them more attractive than any other options I've considered for this in a long time.

Whether brushed or brushless, if the motors you want to use were not -specifically designed for low rpm/high torque- it's a recipe for disappointment for FF. Here's a chart for brushed motors showing cogging vs rpm, comparing a straight armature vs a skewed one: https://www.infolytica.com/en/applications/ex0075/



If you know where to get cheaper motors suitable for FF, brushed or brushless I'd be interested in adding them to my bookmarks.

My post was not about the motors but aimed at validating belt drive as power transmission, and bringing up the 24:1 gear ratio since I think 50:1 is the last I remember being seen thrown about. I talked down belt drive in several previous posts but have since changed my mind after looking closer at the belts themselves and how Fanatec uses them once I realized how nice their wheels are and it seemed relevant to this thread.
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Old 02-20-2018, 05:09 PM   #348
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There's that word again. Spending $400 on motors before anything else is not reasonable for most people.
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Old 02-20-2018, 05:35 PM   #349
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There's that word again. Spending $400 on motors before anything else is not reasonable for most people.


Motors are the heart of these things that without suitable ones FF is a nonstarter so by all means please show us all and link what you think are reasonable cost motors that are suitable for FF.
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Old 02-21-2018, 12:01 AM   #350
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If the gear ratios need to be increased so we can use a higher RPM, so be it, pulleys and belts are cheap. If I have to put up with a tiny amount of cogging that'll be damped somewhat by the backlash in the belts anyway, that's ok. I'm not saying you can't burn money if you want to, but consider the rest of us in your design. Because ultimately accepting some very minor flaws to get decent force feedback is far more reasonable than not having any force feedback because a very small number of people are happy to throw large sums of money chasing diminishing returns. Excessive amounts of money are what make it a non starter long before any minor inconveniences, so please consider the what is achievable to us with less money to spend in your design.

https://www.xsimulator.net/community...progress.7769/
If these guys can build better than commercial racing wheels with $35 motors there shouldn't be any reason why we can't do similar.
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