Parallel Leg Mechanism Design Discussion

[xanhast]

The Vstone Robovie-PC (or KumoTek KT-X PC) uses this or something similar

The knee was heavily "gear interlock parallel link mechanism" adopted

[billyzelsnack]

I saw that interlock design awhile back, but didn't study it. That's a pretty interesting way to get rid of a leg servo.

Another thing I like about the Robovie-PC are the shoulder servos which allow for a lot more room inside the torso.

[billyzelsnack]

Actually.. Looking at it more it looks like it has conventional hip and ankle pitch combined with the parallel leg setup. Very cool.

[Tyberius]

Finally finished up my redesign of Giger.

I've put in a LOT of Inventor time recently. This is a ground up complete redesign from my previous revision, not a single part aside from some bearings and the servos will be re-used. So, I took this as a good time to get the entire robot's frame anodized black.

Here is my finalized model of Giger 4.0, using 14 EX-106+ and 10 RX-64. Stands about 75cm tall.



Giger 1.0 vs Giger 4.0:

[mog123]

I won't believe you if you'll tell me you're using the same servos as in the first Giger

[Tyberius]

Ha, not entirely. Started off with 64s in the legs and 28s in the arms. v2 had the weight bearing 64s in the legs replaced with 106+. v4 is adding an additional set of Ex-106 in the leg-pitch for PLM, and pan/tilt in the waist. The rx-28s in the arm are being replaced by 64s

[mog123]

are you telling me your robot costs a couple of k GBP?

[Tyberius]

14 EX-106+ and 10 RX-64 + all the frame components and onboard controller, it certainly adds up quick. I do work for Trossen Robotics though, so I get a bit of a discount.

Finished up head design, 80.5cm tall including the head.

[Stephane]

I never feel very comfortable when I don't have both end of a servo axis attached to the other section (such as servos for neck, waist, hips, shoulders and elbow twisting in Tyberius design).
On the other hand, changing these joints is not something so easy.

With a big robot like yours, don't you worry that the load on such attached servo will wear them out faster?

(I am probably worrying for nothing, but I can't help thinking that I must find another way to do when I have this kind of joints, not very successfully so far.)

[mog123]

14 EX-106+ and 10 RX-64 + all the frame components and onboard controller, it certainly adds up quick. I do work for Trossen Robotics though, so I get a bit of a discount.

Finished up head design, 80.5cm tall including the head.

I envy you so much. I'd like to work in a company like that. I'm currently designing a humanoid under 400$ (http://xmog123x.blogspot.com/2010/06/im ... alive.html)

[Tyberius]

I never feel very comfortable when I don't have both end of a servo axis attached to the other section (such as servos for neck, waist, hips, shoulders and elbow twisting in Tyberius design).
On the other hand, changing these joints is not something so easy.

With a big robot like yours, don't you worry that the load on such attached servo will wear them out faster?

(I am probably worrying for nothing, but I can't help thinking that I must find another way to do when I have this kind of joints, not very successfully so far.)

These particular joints are reinforced using a different type of horn and a thrust bearing beneath. The current build of Giger was at one point, 7.2kg in weight and about 2/3 the proposed size. It did not stress these joints in any considerable way. The Kung Fu variant that I competed with in Korea at KRGF was lightened up a good amount to just over 5kg, but was under quite a bit more 'wear' given the type of shuffle gaits and impacts I was taking in competition. This again didn't prove to be an issue for these joints. I think as long as they're placed in a manner that they don't have a vertical side loading force on them, it's fine.

[Ausrobo]

Tyberius,

I have been following this forum for some time and your design for parallel legs using dual servos has inspired me to come up with my own. I have been working with a Kondo KHR-3HV for some time and would like to continue to use that platform, however need to translate everything from Japanese is just a little tiresome. The Robotis platform looks pretty good.

My goal is to build a biped at around 80cm. I am thinking of legs of about 60cm. The design I have come up with is based on using carbon fibre tubes for the vertical elements in the legs and the servos, top and bottom for the mounting. Unfortunately my cad skill are not up your level and the plans are on paper.

I did have on question. I have been looking at the ankle and hip joints and am concerned that like the legs, they will need two servos each. Have you considered this on your design.
Also how is the design going, have you moved on to construction?
Peter

[Tyberius]

Tyberius,

I have been following this forum for some time and your design for parallel legs using dual servos has inspired me to come up with my own. I have been working with a Kondo KHR-3HV for some time and would like to continue to use that platform, however need to translate everything from Japanese is just a little tiresome. The Robotis platform looks pretty good.

My goal is to build a biped at around 80cm. I am thinking of legs of about 60cm. The design I have come up with is based on using carbon fibre tubes for the vertical elements in the legs and the servos, top and bottom for the mounting. Unfortunately my cad skill are not up your level and the plans are on paper.

I did have on question. I have been looking at the ankle and hip joints and am concerned that like the legs, they will need two servos each. Have you considered this on your design.
Also how is the design going, have you moved on to construction?
Peter

Hi Peter,

Would love to see your designs when you get them on a digital medium!

I have actually had the same thoughts about the ankle/hip joints. The way I have it designed currently, I could forgo using the current hip/ankle brackets and replace them with the brackets in the knees. Those brackets could then attach to a double EX-106 assembly quite easily. I had even set aside 4 additional knee brackets in my BOM specifically for this purpose.

My current plan was to try it out with a single EX-106+ in the ankle/hip roll positions, and then move on to the double ex-106+ configuration as needed. I'm fairly certain I will need that configuration to get the desired results however. I'm also looking at getting the size down a bit on my own, under 60cm total height so it's still viable for the kidsize Robocup league.

[Ausrobo]

Andrew,

I have been working on building the hubs that link the carbon fibre tubes to the servos. I am pleased with the first version, however it took way to long to make. I will need 32 of these, so I need a more streamlined way of producing them. The second version was faster but I am concerned if it will be robust enough. Off to design something in between.

Cheers,

Peter

[UncleBob]

Funny. I tought about tube yesterday. Tubes to join the servos together actually.