by PaulL » Thu Nov 10, 2011 10:15 am
by PaulL
Thu Nov 10, 2011 10:15 am
An update...
(removed overly grandiose verbiage
)
I've been coding, sure, but I also worked on the hand design a bit this last weekend. I had a bit of a "duh" moment. I was going to use the case screws on the bottom of the MKS DS-450's to secure the servos to the hand base plate, but realistically, there isn't much thread and the screws are tiny.
I was planning on countersinking the screw holes to leave some bite for the screws in the servo case, but there wasn't much room to play with anyway. Instead, I'll skip drilling and countersinking 20 holes in the base plate, and do servo tape for mounting the servos.
And, instead of machining a servo horn hub and tendon strip as one piece of teflon, I'll machine a sleeve / hub for the horn, cut some strips of teflon from .020 inch sheet stock, and thread and screw the strip to the hub. The bracket design got a bit more simple, too.
I'll probably buy Vectric's Cut2D (DXF to G-code for my mill), as I fiddled with it more this past weekend, and I think it's a pretty good piece of software. Cheaper to buy that than to spend time manually generating G-code or building my own tool (which would take me away from my dev focus). The tab feature alone is worth it!
The sound card design is on hold for now, I can do proof of concept w/ the IM380A adapter and full-sized PCI card. Using a custom mPCI audio card or the adapter and full-sized PCI card makes no difference to my code, so I'm not worrying about it for now. Clearly, at some point, I'll get back to it. The design is basically done, but I found myself over-designing, another good reason to step away from it for now. When I've got things proven out, I'll finalize the board work and send it off. I don't see it as a money maker - the interest in such a product is very limited, and heck, the parts are obsolete.
Regarding the hand design - it seems MKS bumped up their prices a while back, the servos seem to be no less than $31.00 USD now, meaning $300.00 USD for servos alone for one pair of hands. Luckily, I bought 11 of them at around $25 / each a while back, but ultimately I want to have at least 2 pair for 2 bots. Why am I so stuck on using these servos? Size, torque, and metal gears!
I'm still trying to work out a few hardware aspects. The hip rotation design should be fine, still need to cut up some Nylatron and see what the friction is like (simplifies the design). I will probably use the same design for wrist rotation as for hips, but the problem there lies in what servo to use to rotate the hands. The DS-450's in the fingers aren't a problem, individually they don't need much torque.
It's tough to fit a wrist rotation servo in without affecting range of motion. Using a micro servo for wrist rotation would be minimally intrusive, but the wrists need to be fairly strong if I'm going to have him do push ups or cartwheels or push up from a fall and so on. If I go with a full-sized servo, it will be bulky and weigh more. Still not sure what to do with this.
And yet another concern is in the neck motion. I WANT head tilt (2 axis) and rotation (a 3rd axis), but getting a mechanism in there without jacking his head up, one that will withstand headstands and one that I can run wires through, will not be easy. I can draw up a design (and I have a few), but manufacturability is a problem. Clearly, the servos will have to be micros, and will have to be remote located - pushrods, guided wires, in all, no easy answer here yet.
The hands are a big deal for me, as they'll convey expressiveness that I won't be able to convey otherwise. The neck motion will also help, but who knows, I may have to stick with just rotation (and maybe some limited range of motion in his neck will keep him a bit more "robotic", who knows). Hips should be OK, but wrists may end up getting full-sized servos slung off the back side of his arms.
He'll be heavy, which is another reason I went with a bunch of HSR-5498SG's (and yes, I have enough for 2 bots, hip rotation servos included). And run-time? I have no idea at this point. Maybe I'll have to shop for batts again, see if I can somehow shoehorn more amp-hours into his battery compartment. Advanced power management is definitely an "in the future" goal. The shorter the run time, the more quickly I will push to improve power use.
I've thought of some demo videos, picturing two (red and blue, already bought the bracket sets) talking amongst themselves about their technology. I am thinking of taking the silver bracket set and weathering it w/ airbrush / etc, make that one (w/ stock setup) look worn and aged beyond his years, and have the tougher two interact with him (his name will be Rusty - LOL!). Lots of potential.
Take Care,
Paul
An update...
(removed overly grandiose verbiage
)
I've been coding, sure, but I also worked on the hand design a bit this last weekend. I had a bit of a "duh" moment. I was going to use the case screws on the bottom of the MKS DS-450's to secure the servos to the hand base plate, but realistically, there isn't much thread and the screws are tiny.
I was planning on countersinking the screw holes to leave some bite for the screws in the servo case, but there wasn't much room to play with anyway. Instead, I'll skip drilling and countersinking 20 holes in the base plate, and do servo tape for mounting the servos.
And, instead of machining a servo horn hub and tendon strip as one piece of teflon, I'll machine a sleeve / hub for the horn, cut some strips of teflon from .020 inch sheet stock, and thread and screw the strip to the hub. The bracket design got a bit more simple, too.
I'll probably buy Vectric's Cut2D (DXF to G-code for my mill), as I fiddled with it more this past weekend, and I think it's a pretty good piece of software. Cheaper to buy that than to spend time manually generating G-code or building my own tool (which would take me away from my dev focus). The tab feature alone is worth it!
The sound card design is on hold for now, I can do proof of concept w/ the IM380A adapter and full-sized PCI card. Using a custom mPCI audio card or the adapter and full-sized PCI card makes no difference to my code, so I'm not worrying about it for now. Clearly, at some point, I'll get back to it. The design is basically done, but I found myself over-designing, another good reason to step away from it for now. When I've got things proven out, I'll finalize the board work and send it off. I don't see it as a money maker - the interest in such a product is very limited, and heck, the parts are obsolete.
Regarding the hand design - it seems MKS bumped up their prices a while back, the servos seem to be no less than $31.00 USD now, meaning $300.00 USD for servos alone for one pair of hands. Luckily, I bought 11 of them at around $25 / each a while back, but ultimately I want to have at least 2 pair for 2 bots. Why am I so stuck on using these servos? Size, torque, and metal gears!
I'm still trying to work out a few hardware aspects. The hip rotation design should be fine, still need to cut up some Nylatron and see what the friction is like (simplifies the design). I will probably use the same design for wrist rotation as for hips, but the problem there lies in what servo to use to rotate the hands. The DS-450's in the fingers aren't a problem, individually they don't need much torque.
It's tough to fit a wrist rotation servo in without affecting range of motion. Using a micro servo for wrist rotation would be minimally intrusive, but the wrists need to be fairly strong if I'm going to have him do push ups or cartwheels or push up from a fall and so on. If I go with a full-sized servo, it will be bulky and weigh more. Still not sure what to do with this.
And yet another concern is in the neck motion. I WANT head tilt (2 axis) and rotation (a 3rd axis), but getting a mechanism in there without jacking his head up, one that will withstand headstands and one that I can run wires through, will not be easy. I can draw up a design (and I have a few), but manufacturability is a problem. Clearly, the servos will have to be micros, and will have to be remote located - pushrods, guided wires, in all, no easy answer here yet.
The hands are a big deal for me, as they'll convey expressiveness that I won't be able to convey otherwise. The neck motion will also help, but who knows, I may have to stick with just rotation (and maybe some limited range of motion in his neck will keep him a bit more "robotic", who knows). Hips should be OK, but wrists may end up getting full-sized servos slung off the back side of his arms.
He'll be heavy, which is another reason I went with a bunch of HSR-5498SG's (and yes, I have enough for 2 bots, hip rotation servos included). And run-time? I have no idea at this point. Maybe I'll have to shop for batts again, see if I can somehow shoehorn more amp-hours into his battery compartment. Advanced power management is definitely an "in the future" goal. The shorter the run time, the more quickly I will push to improve power use.
I've thought of some demo videos, picturing two (red and blue, already bought the bracket sets) talking amongst themselves about their technology. I am thinking of taking the silver bracket set and weathering it w/ airbrush / etc, make that one (w/ stock setup) look worn and aged beyond his years, and have the tougher two interact with him (his name will be Rusty - LOL!). Lots of potential.
Take Care,
Paul
Last edited by PaulL on Tue Jun 19, 2012 1:52 am, edited 1 time in total.