What kind of bug? Could it be due to translation offset on your Coxa joint?
Hi,
I spent several ours yesterday for debugging. Finaly I found the bug and its solved now. 
The bug was caused by a combination of low resolution by a SQR function and the limited resolution of the fixed point table based ARCOS function Xan uses in his new V2.0 code. For a “normal” hexapod or a leg consisting of coxa(horisontal rotation),femur and tibia that is a very rare problem I hope. I can’t see the bug on Phoenix. In Xan’s new code I made a simplyfied version of Atan2 using the fixed ARCOS table, so when the diagonal distance between the center of femur and tars are almost equally to the leg height (YPos) the resolution was to low. So I solved it by using the float Atan2 function.
Anyway, that problem is solved and I’m happy!
Glad to hear that. Now eagerly waiting for your video!
You have to wait for some time though, I still have alot of work left 
I don’t think I’ll post a new video before I’m satisfied with the result.
Hi KÃ¥re, Xan,
So I think you said you’re using Xan’s code, modified of course. and I saw the gait data.
I’m having a bit of a problem getting my head around part of the problem. the Phoenix legs are sprawl, while Felix and Little Cat’s legs are “stand up”. I have the same basic knee as you do.
In the Phoenix, the femur is adjusted to be horizontal, and the tibia to be vertical. These are the servos 1500 settings.
Do you also make both the knee and hip servos be 1500 with the leg bent as you show in your pix? Are you able to use the same IK calcs? For a while it seemed that they would have to be entirely different, maybe not.
The sprawl legs of a hexapod have the knee “up in the air” (above the hip), but the 'quad knees are lower then the hip. My IK drawing is looking a lot different.
I found a couple of good cat skeleton pix, and I’ve made some measurements to aid in the proportions of the legs and body of Little Cat. the normal standing posture of the cat seems to be with a very similar “knee” angle as you show in your Felix pix, and indeed, as I’ve initially posed my 'quad at. the leg proportions aren’t bad, but I still want to work out the ratios of length of the shoulders, haunches, and leg lengths.
Then there’s the feet. You were mentioning balls for the feet. What about some passive feet?
Alan KM6VV
Hi Alan,
I calibrated the leg the same, but there where some larger offsets though.
I’m not using the same IK. So far its only 3 DOF IK (Hip, femur and tibia, the coxa are passive). But I rewrote parts of the LegIK.
I’m not sure if I understand what you mean with the passive feet. But I’ve been thinking of making some small 2DOF feet (and remove the coxa joint), that would make him much more stable. The IK shouldn’t be a big challenge to add I hope, as long as you know at what angle the tibia has in relative to the ground.
But then again maybe a bit odd/strange looking? More like the AT-AT walker (from Star Wars) LOL 
. What do you think?
At this moment I’m not really sure what direction i want to go for the Felix project. Lately I’ve been thinking of some other very different projects. I’m not giving up making Felix walk better, I just want to spend time on something else this autumn.
Woe! please zenta dont give it up. i was reminded of my mistake when i ended the stalker project. 
The quadruped scorpion is now under fire as i have another project in mind.
but i will complete the quad first.
anyway i hope you finish it and are happy with the end results.
keep up thye work.
Hi KÃ¥re,
OK, I’m still mulling over the IK calcs. While I fully understand the hexapod IK calcs, the “triangles” aren’t falling in place yet for the 'quad IK calcs.
We currently have no “ankle” joint in our legs, 3 or 4DOF. In looking at cat skeletons, I see that the rear foot is quite long, and greatly aids the cat in it’s locomotion. I purpose a passive joint (no servo) at the ankle, just perhaps a small spring. I think this would increase the stability of the gait.
Odd/strange? A 2DOF 'quad? I don’t think so! I’m the one that came up with Loki and the Creepy Hybrid!
Alan KM6VV
