I was bored and in the mood to tinker and build, so I added a rotatable and tiltable foot to one of the legs I designed for WALTER. I actually had enough servos to complete the leg. I took several pictures of it to show the range of motion, especially of the foot. This is a full 3DOF leg with foot rotation and tilt motions. I also built a testing jig out of the remaining decks, which seems stable enough if I add weight on the top, to test all leg motions.
This would be the “normal” walking orientation of the leg.
As with the eventual version of WALTER for self leveling, there will be four legs. I can easily detach the foot assembly and replace it with an MMT-03 motor mount at the rotation point. It’s really amazing how much flexibility is gained by adding on a rotatable/tiltable foot.
I connected this leg up to an SSC-32 today and tinkered with it a bit. I discovered I have 1 bad HS-645 and probably a bad SSC-32 also, so will have to replace those next month. I’ve also decided to get six HS-485 servos, since I want to use the same servo throughout this project. I think I am going to end up having two separate robots - a quadrapod with this leg design, and WALTER with four steerable wheels. Eventually, I will merge the two in order to get a self leveling hybrid WALTER. I think things will be interesting enough with WALTER and four steerable wheels for awhile.
Once I have the HS-485 servos, I will replace all the HS-475s I have in use and just use those for experimenting, pan/tilts, etc.
Here are some pictures to show the direction I want to go for legs at some point. The wheel can be used as a wheel or a foot. I’m sure this won’t be the last revision of this leg design, because it really doesn’t have the range in the ASB-11 section that I would like to have. I wish there was a “long” ASB-11 as I think that would work perfectly in situations like this.
I am amazed! The servos I have installed into the leg with the motor and wheel are working! They are lifting and manipulating the joints of the leg perfectly! I have HS-645 servos in the two heavy lifting joints (2nd and 3rd). Now I know that the problem with the other leg/wheel I had built was due entirely to a power issue. This makes me feel so good because it means I will not have to go to digital servos now.
I’ve been playing with the current leg I have built, but am not happy with its range of motion. I can’t get the wheel high enough using this 3DOF design, so am looking at the possibility of going with a 4DOF design which does allow the range of motion I want. However, I’m not at all sure how a 4DOF leg is going to work with the added weight of steering and wheel tilt and the motor and wheel at the end. I’ve assembled brackets for one possible 4DOF leg design and just have to disassemble the current leg and put servos in this new leg. I don’t have the third HS-645 servo I need though. I’m getting concernd that the first HS-645 won’t be able to lift the rest of the leg.
Yes, I’ve seen those. I just came up with another 3DOF leg design I am going to try. I wish I had more servos so I could keep more than one leg built up, so I can really compare range of motion between designs.
The new design uses an ASB-15 and two ASB-11. It’s a very simple design and I think it might give me the range of motion I want. More on this when I have it built up with servos.
I am not quite sure how I should mount the ASB-11 to the hip rotation servo for the best strength. I’m concerned about putting this much weight on an unspported servo horn.
In looking at the current leg design I have, and considering others, I’m really not happy with the transition point from leg to wheel (steering and tilt). It just all seems to make the whole assembly too unstable. I’m not at all sure how to deal with this without a custom bracket of some sort. I think the whole leg with wheel steering and tilt make the whole thing too long to be really workable for what I want to do. I think the weakest link is between the 3DOF leg and the steering for the wheel.
I’d like feedback on how I might best accomplish what I want to do with this.
I’m getting concernd that the first HS-645 won’t be able to lift the rest of the leg.
