Force feedback throttle

[KStolp]

I am running TA7291SG for motor controllers, there is a VRef in that allows me to connect to arduino pin that support PWM and regulate now much power the motor gets. in future i plan on using this as a part of the force feed back. running 0 - 255 i am currently running 180 getting it enough counter resistance to have a push against something an for the controller to still be able to return to center. I will post a video when i have time for everyone to see how it moved around, i want to print a handle first.

Another thing i need to print is a base case, when pulling up the unit it needs some weight to counter the pull.

[mike43110]

How much weight do you think will be necessary?

The Arduino due could go into the lower case as there will be space. Moving to a stronger controller will be useful if more advanced features like ffb ever get completed. Would be amazing though.

[KStolp]

UPDATE, So i had it working but there is much calibration that i currently don't have the time to deal with. I added a bunch of copper pennies to the bottom in a case. not sure how much weight i added.

So here is my View currently as i see it now. The Good, The Bad and The Ugly.

The Good
The Build work and the frame is Solid, it moves nice and has very good return force for 5V on 12V motors. nice range of movement as well.
Future thing that would be great, feedback of-course.

The Bad
The Gearbox, i have slip in one of my 3 gearboxes again, the Calibration mostly i need to spend more time on it, but if the controller hits the wrong spot if got in to this trying to center loop and just keep moving the effector plate until you help it out might be better with a full handle on top. i think the unit needs to be connected to the table to fix the weight issues and a issues of sliding forwards and back as you try to move those direction.

The Ugly
Gears... Dam Gears, can just get one set, gotta get a whole wack of them to get the needed 3 or 4 gears and when i checked the bag i orders some gear where missing but i got the ones i needed. need thicker ones to with hope stop the slipping, Mod 0.8 dont seem to work well enough and i cant seem to get them to print nice enough.

Post some question if you have any, i will make a GIT and upload what i have sofar maybe some one whats to see about building a better gear box. I have another project i need to get back to.

[Ghostpilot]

Is it only the gears fault they are slipping? What about the seats for the axles for instance?
If those seats aren't level the gears will wobble. A broken gear might be cause of the slip, but the wobbling might be the cause of the gear breaking in the first place.

[fledder]

I just had what I think is is a great idea... what about using a mechanism like a hard drive voice coil to directly apply servo force to the arm? Might need some higher current than a motor, but it wouldn't require any gear train or anything. You could then use the delta kinematics equations to recenter all axes, or only the X and Z axes while allowing Y (throttle) to stay where you put it... thoughts?

[LVMIKE]

Voice coils are an interesting idea... But they may experience the same issue steppers will, which is long term back-driving causing demagnetization. I'll admit, I'm not that well educated on that aspect, but it was something of concern I found in researching steppers.

[fledder]

How long term are we talking about? Could also use two electromagnets instead of a permanent magnet and an electromagnet... would increase total power requirements, but might also make it less dangerous to magnetic media when shut off...

[LVMIKE]

Unfortunately I'm not that well educated on the subject, but here is what I was able to find.

It is also worth noting that the best way to demagnetize something is to expose it to a high frequency-high amplitude magnetic field. Running the control system to spin the rotor at high speed when the rotor is actually stalled, or spinning the rotor at high speed against a control system trying to hold the rotor in a fixed position will both expose the rotor to a high amplitude high-frequency field. If such operating conditions are common, particularly if the motor is run near the curie temperature of the permanent magnets, demagnetization is a serious risk and the field strengths (and expected torques) should be reduced accordingly!

http://homepage.cs.uiowa.edu/~jones/step/physics.html Stepping Motor Physics: EMF Issues by Douglas Jones

But voice coils look to work pretty differently, so this may not be an issue at all.

[fledder]

I'm thinking you wouldn't need high frequency at all. It could act just like a spring, where the amount of current in the voice coil would be proportional to the amount of force you want to apply as "feedback". With the stepper, you would be trying to step the motor, which is a high frequency thing, but this should be a little easier on the magnets. I hope.

I think the next step is going to be building a test rig of some sort, as I'm not sure what kind of currents we are talking about here and if they are achievable on this sort of scale. Sadly I apparently have to keep going to work and feeding my family, so it might be slow going, but y'know...