thinking back to this Jim we know that the femur drive effects the tibia indirectly, resulting in a parallel pseudo 3rd DOF.
With this its apparent that once the tibia servo actually starts to perform its rotations it counter acts this and then sends the tibia off the true rotation. reversing the tibia servo command wouldn’t fix this due to the indirect drive.
like you said this only happens in some positions that must be avoided of which can be altered in the code. i think.
ill run some more test later to see what can be done.
When it comes to the IK for this design the tibia angle must be recalculated in the LegIK sub:
IKTibiaAngle = IKTibiaAngle - IKFemurAngle
For the V2.0 code it would be TibiaAngle1(LegIKLegNr) and so on.
I’ve not tested it but I think this should work though. This leg design has some limitations when the femur angle are getting close to +/- 90 deg.
thanks zenta, i will run this though the code soon.
yes i have already noticed these limitations. iv been using the Min/Max angles to create limit end stops on the rotation. i must say though, from doing some testing I’ve noticed the range of motion and travel length is quite small compared to the conventional SES legs.
fun to play with though. it would be great to build this right up. maybe in the summer.
So there is a bit of a mechanical drawback to having skinny legs and all of the guts up around the chassis. lol
I was thinking maybe going to 4" on the femur. Was also thinking, would a 485 work for the knee servo and a 645 for the vertical hip servo? I guess we need to test if the leg design can handle the chassis payload before we build one of these guys…
Over the weekend I had a “slightly different” robot assembly competition in my head. You won. I am sending you everything you need to build this robot. Since I made up the competition, I might as well make up some rules…
I will provide you with everything to build the bot. Including Bot Board / Atom Pro 28 / SSC-32, etc…
We will agree on what parts to build it with. I will manufacture any parts that are not off the shelf.
You must build it with the agreed parts before venturing off on making other changes.
If changes to the assembly look necessary you must discuss them with me before adopting them.
After the thing is working to what we all agree is the best it can do, the bot is yours to keep.
at the moment i have arranged it using the 485’s with a weight of 9oz leg configuration. i feel this would work fine. maybe for bare minimum. using 645’s one the vertical hip would be a good idea, although there is not extra over hanging weight at the end of the femur, plus all the weight is centered.
WOW jim. the first competition i have ever won, and i didn’t even enter in for it. Lol
i feel honored to build this for you, im speechless!
esteem has hit the roof.
first thank you for this opportunity to work on a real project.
The rules sound very reasonable and it a nice way to work. we can discuss how it will be built / look and most importantly, function shortly. did you get my email?
i have also been thinking about what you have said about using the HBKR range of chassis for this. iv been looking at the measurements and all seems ok, but i will let you be the judge of that.
let me know how you wish to proceed.
Jim, i will PM you soon.
Yup I got it. I was addressing it here. Hope I didn’t miss anything.
Sounds good. It always takes a few days to get these special orders organized. So be patient. I think this will be a fun project. Even if it doesn’t work as well as the traditional one. It will definitely look unusual but in a cool way I hope. lol
The thing that intrigues me the most about this design is the way two servos face each other in perfect alignment. This allows the second axis servo to be coupled via dual push rods as shown, or even MXL pulleys. I am most interested in trying this design as a large arm. 8) Could be very powerful.
Yes, im actually quite surprised that no one has used the ASB-13 like this before. i actually made something similar to this, using push rods when i was flying my quadcopter. it was for a camera pan and tilt.
with it configured like this it does allow for lower torque servos to be used in the tibia. it would be great to see dual push rods used more. the arm sounds cool.
If someone could measure the center to center distance and give me the pulley diameter I could figure out what belt to use. Belts have the added advantage over push/pull rods of only being limited by the servo range where the push/pull rods are limited to <180 degrees.
I am sending you everything you need to build this robot. Since I made up the competition, I might as well make up some rules… 
