What is rest position?

Lynxmotion Electronics & Software
1

I have a biped that I thought I had calibrated correctly, with all 17 servos “idle” at a “stand at attention” stance. When I installed the servos I set them at 1.5mS, then set them up physically so the joint was at 0 degrees, or 90 degrees. I have the biped mounted above table top so he doesn’t collapse under no power condition.

If I select “all servos to 1.5mS”, my biped has a few unnatural postures, ie a foot turned out a bit, an arm up, one knee bent. The servos draw about 1.5 A total at this point.

If I power down then power up the ssc32u I get a whole different response with many joints severely contorted. If I power-cycle again, the shape changes again, but power draw in all these cases is only 0.12A. This leads me to believe THIS is the natural rest position and I should manually move my servos into the right position (“stand at attention”).

I get further confused when I go to the sequencer and set offsets in the servos to make the biped EXACTLY at attention.

My feeling is that, at rest, just hanging there with no power on, the biped should be at attention. When powered on, there should be NO CHANGE in any servo and power should be low, ie 0.12A, likely only the SSC32 power draw at this point. Is my analysis correct?

2

I’ve decided to step back…took the biped apart and will recheck and recalibrate all servos at 1.5 mS, then work with smaller pieces. I was working with all 17 servos at a time; I’ve now decide to work with just one leg or one arm at a time and check and double-check how the joints are supposed to line up.

I was sloppy in my first attempt to get this working.

3

Be sure that the calibration / fine adjustment was actually saved.

4

Yes, I did save it initially but upon rechecking my “joints” I found a couple way off. I now have it so that with 4 joints on a leg, and all calibrated at 1.5 mS (ie all at 0 or 90 deg), the leg can stand on it’s own in perfect balance, and when I take the power off, it still stands. The way I had it before, it would fall over because I wasn’t paying proper attention to center of gravity and balance.

What I did was put bad tires on a car and did a wheel alignment: start bad, you end bad.