The Quadruped chassis can handle 2DOF, 3DOF or 4DOF legs, either in a sprawled (insect) or Mammalian (cat or dog) layout.
due to the manner in which the four yaw servos are mounted, only a single chassis plate is required to construct the 'bot. The more familiar use of 3DOF legs will still require two chassis plates.
Although for a 4 x 4DOF 'bot, using tubes and flanges on the corner servo horn mounts makes for an interesting and very attractive spacer for adding an second deck (chassis plate).
A standard cutout for mounting a BB2/SSC-32 stack is incorporated into the design, as well as cutouts for four (4) yaw servos.
Lithium Polymer or LiMH batteries up to 5.7" x 2.75" can be accommodated on the chassis.
I’ve got the legs and boards on a new metal chassis, and I’m working out the “neutral” position for the legs, and getting them set up properly.
Seems like the legs should have a little bend in them when at rest, what do you think? I saw your “Fexix the dog” walking in a video yesterday. Impressive! Looks like you’ve got a bit of a roll in the gait, to help with the COG maybe?
Hopefully this weekend I’ll be able to “power up” and test some idle positions on my little cat this weekend. Not the proper battery pack yet, I’m waiting for a check (actually Paypal) to be able to order some LiPo batteries and appropriate charger. Thanks for the battery info!
I should grab a few pix too while I’m at it to post.
It’s been slow. I’ve got some mods into the 1.3 Phoenix code.
Finally got the LiPo batteries, and a charger for them. Two months wait for the batteries on back order. Also got a pair of BEC’s.
A Lexan chassis is seen in this old pix, I currently have a nice .080" aluminum chassis with the yaw (geared) servo horns running in pockets to get the proper gear alignment.
I’m also trying to get a Micromouse up and running for our local HBRobotics club meetings.
Very interesting to see a picture!
But may I ask why one of the hip servos (front left?) are mounted the oposite way (the C-bracket pointed downwards)?
I wondered if anyone would notice! I noticed it after I hoisted and posted the pix. At the time, I was experimenting with a different leg arrangement, one that would give a little more rotational travel to the new “roll” joint. It worked, but made adjustment of the force on the LP bearing (backlash) impossible to adjust.
I am still not satisfied with the adjustment of the bearing load. I’ve tried to find the Bellville washers that I’ve used elsewhere, but nothing of the appropriate size. Still looking!
Aren’t the servo horns all facing inwards? l guess I’m not following you.
Oh, the “roll” servo! Yes, they should be as well; it would give me more clearance. I have new '654 servos to replace the hip and knee '475 servos, so I’ll make the changes. Thanks for that catch!
On the LP (thrust) bearings, I think I may need a bigger diameter. Any chance of a new part Jim?
Just taking a first look at your project, I predict you will have issues with the gearing at the top of the leg. If there is any slop in the top bearing then the small thin gears with fine teeth will slip and not hold under load. I suggest you go with gearing with larger thicker teeth that will be more tolerant of alignment holding issues with the top bearing setup.
I’m not seeing any slippage as of yet. These are the parts of the LP bearing, and my mounting the gears and hubs on my much larger .080" chassis instead of LM’s .060" aluminum plate should make it more stable. I have some play, that the Belleville washers would theoretically help take out.
Probably would be good to power up the gear drive servo and do some load testing to see what happens. A chain drive might be a possibility, but has its own issues. Since the rotation range is limited, a simple dual rod servo arm push/pull setup might be workable.
Pushrods probably can’t make the 180 degree swing.
That does give me an idea. With a little gearing, like for the tilt/pan from Servo City, I could simply mount a new precision pot driven with a 2:1 gear from the servo. That would work!
Alan is this the Neutral stance “home pos” or just standing for the camera?
you will need to have the legs bent to make it more stable. you could get it walking without changing the legs.
as long as you keep (##PosX at 0) the code will know the legs are underneath and inline to the body.
e.g:
; Initial Start positions of the feet.
;Right Front leg
[code]RFPosX = 0
RFPosY = 55
RFPosZ = 40
; Right Rear leg
RRPosX = 0
RRPosY = 55
RRPosZ = 40
; Left Front leg
LFPosX = 0
LFPosY = 55
LFPosZ = 40
; Left Rear leg
LRPosX = 0
LRPosY = 55
LRPosZ = 40 [/code]
in order to use the HipRotate Servos you would need to do some changes: In ServoDriver it looks like this:
It’s just standing. I was planning on a bend in the legs. Although the “triangles” for the IK are hard to work out. I pulled out a few angled servo brackets. Not sure if they help my legs.
You’re saying a 90deg rotation would help the hip servos? Not exactly following. It’s probably been too long since I worked on my IK last to remember.
