Translation controller

Robb Bates

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What attempts have been made at building translation controllers? I've been bouncing that idea around in my brain since I started my pit.

Oddly, I just happen to work with one of the guys who built the original translation controller for the Space Shuttle :speakcool:. He showed me some photos of the thing. The internals, other than being seriously over engineered (as all good NASA projects are), are nothing more than a regular joystick with a push pull axis. Now how hard can that be to make one of our own? We have enough techy guys here to pull this off.

Thoughts?

Robb
 

Zatnikitelman

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I once broke a Logitech Extreme3d Pro joystick and promptly proceeded to take it apart if anything, just to see how it works :p The "head" piece for lack of a better term where the hat switch is could be useful. It contains the four hat-switch buttons mounted around the hat switch's post, then four buttons for the top, and a limit switch for the trigger. What's great is the head comes apart all in one piece so you have this nicely-discrete package of stuff. Perhaps mounting it vertically (so the hat switch would stick "up" pointing towards you) and fitting a custom post in there made out of styrene or something would allow up, down, left, and right. For forward, back, you might could mount the entire head against your own buttons using springs to provide the centering force. Only problem is the buttons work through some weird series of diodes so I wouldn't even begin to know how to wire it (like 4 wires for 4 buttons).
Yes, I have given this a lot of though for my own someday-might-possibly-kinda-maybe-almost-not-sure-gonna-happen Simpit! :p
 

Robb Bates

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Just do it! Jump in like I did. I'm shocked at how quickly my simpit came together. And I did it fairly cheaply. Still working on it, but it has a good foundation.

Just about any joystick can be torn down to get the X/Y axis mechanism. I think it's the push-pull that stumps everyone. There's no quick and easy way to get that kind of mechanism stuck on the end of the X/Y stick.

Looking at the Shuttle THC, it's not a quick and easy way either. It's basically a rod that runs through a tube. The tube is connected to the X/Y mechanism. The Z axis is an offset potentiometer with a linkage that turns the pot as you push and pull the rod. Of course there is spring return centering too. The whole Z axis thing goes for a ride on the end of the stick as you move the X/Y part.

It's not a difficult bit of engineering, just not something that can be easier hacked together from existing parts.

Robb
 

Robb Bates

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Functionally it probably would, but somehow it's missing that ... uh... industrial look. Too "Lexus", not enough "Caterpillar".

Robb
 

Usquanigo

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Functionally it probably would, but somehow it's missing that ... uh... industrial look. Too "Lexus", not enough "Caterpillar".

Robb

It doesn't look like a worthless white-good appliance on wheels (toyota) trying to pass itself off as high quality (luxury) to me.

If anything I'd say it's rather Cadillac. Has some of that Art and Science feel to it, just without the edgy angles (which would be cool on it).

Actually looks like something that would be at home on the XR-2. Though as you said, not so much on a Dragonfly.
 

yagni01

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Looking at the Shuttle THC, it's not a quick and easy way either. It's basically a rod that runs through a tube. The tube is connected to the X/Y mechanism. The Z axis is an offset potentiometer with a linkage that turns the pot as you push and pull the rod. Of course there is spring return centering too. The whole Z axis thing goes for a ride on the end of the stick as you move the X/Y part.

It's not a difficult bit of engineering, just not something that can be easier hacked together from existing parts.
If you explained our conundrum to the guy that built the real one, think he could come up with some ideas using common hand tools, materials and electronics parts? Something "prototype-ish"?

I haven't seen any pictures/drawings of the inner workings of those. Are they ITAR?
 

yagni01

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Have a look at this: http://www.nasa.gov/centers/johnson/pdf/383442main_controllers_workbook_21002.pdf

Section 3 explains the THCs.

btw the THCs are not analog. They are purely on-off switches (digital). They have a total of 18 switches (triple redundant).
Hadn't seen that one. Good reference, thanks!. Doesn't show any internals, but does say deflection is only 0.5". I swear while I was watching an ISS docking he pulled it out a good 2-3" during a Z-translation. Maybe Hall Effect sensors would be simpler than micro switches. Hmmm. . .
 

C3PO

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If you go with switches, you'll need a fully functional DAP to make smooth maneuvers.
 

yagni01

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If you go with switches, you'll need a fully functional DAP to make smooth maneuvers.
If you were going to use translation and rotation simultaneously, I agree, but you can still use them separately like switching modes back and forth with the keyboard, just without the extra keypress and double checking what mode you're in.
 

Robb Bates

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That's cool. The pictures of the THC he showed me were not flight grade, they were for simulators and used off the shelf potentiometers. I wonder why the difference. Switches would be so much easier to build.

He is a technician, not an engineer. He built it, he didn't design it. And what he show me were just some photos, not drawings.

Robb
 

scuba_steve

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I've been planning on building a THC using an arcade style joystick

http://www.happ.com/joysticks/competition_joy.htm

They're pretty cheap, easy to interface too (just switches) and i think they have a bit more of that "industrial" look? Down side is they're digital and that anoying lack of a z-axis.

My plan is to have two side by side. One for Up/Dn L/R and the other only using one axis as fwd/aft. Sort of a throttle and stick idea, but only inches away from each other so you can use one hand for both. Havn't mocked it up yet, so this is all speculation.

Side note: whats a DAP?
 
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Robb Bates

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Digital Auto Pilot? I think it has to do with the shuttle's computer monitoring rotational rates and zeroing it out when you let go of the stick. It does more than just that I think, but that's one of it's main features. Or I may just be completely wrong.

Robb
 

C3PO

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If you were going to use translation and rotation simultaneously, I agree, but you can still use them separately like switching modes back and forth with the keyboard, just without the extra keypress and double checking what mode you're in.

That's not the problem. With a digital joystick you would only have full thrust or no thrust. The DAP regulates how much DV (adjustable) you get from each push of the THC IIRC.
 

tblaxland

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Digital Auto Pilot?
Yes

I think it has to do with the shuttle's computer monitoring rotational rates and zeroing it out when you let go of the stick.
If in disc rate mode, yes. Other modes are accel (closest to using the RCS numpad keys in orbiter) and pulse: http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/avionics/gnc/dap.html
[FONT=Arial, Helvetica, sans-serif][SIZE=-1]when pulse is selected, a single burst of jet fire is produced with each RHC deflection. The resultant rotational rate is specified on the DAP config display. When disc rate is selected, jet firings continue to be made as long as the RHC is out of detent in order to maintain the rotational rate specified on the DAP config display. When accel is selected, continuous jet firings are made as long as the RHC is out of detent.[/SIZE][/FONT]
It does more than just that I think, but that's one of it's main features. Or I may just be completely wrong.
The above link has lots of good info on it.
 
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