The center position of each servos are not stable

Lynxmotion Legged Robots
1

Hi community

I built quadruped robot with these parts and Pixhawk2.1 Cube black.



But the center position of each leg’s servos are not stable.
Please see below image.

This collapsed disarm posture is controlled by the Cube black controller.
However, the center position is slightly different between the left and right.

image
image2485×1959 518 KB

How can I solve this probrem? Can I adjust the center position of servo?

Thank you for your help

2

Yes, you will need to do two things:

  1. Send a zero signal to all servos, then physically disconnect and reconnect the joints which are very far off (this will get rid of the “macro” errors).
  2. You then need to calibrate each servo in software. Since the Pixhawk is not directly made for legged robots, you’ll need to find where in the code you can offset each servo upon startup
1 Like
3

It’s a bit offtopic, but I’m wondering why these servos have 24 teeth?
That way you can’t adjust alignment of a servo horn at all. Because 24 / 4 is not a fraction.
No matter which of the 4 horns you try to use, they alway lock at the same angle.

With e.g. 18 teeth, each horn would lock in half a tooth different angle. 18 / 4 = 4.5

I hope, I made my point clear. Although it won’t change much.
Knowing how to make things better, but not have a chance to change it, is frustrating sometimes…

4

Don’t know the history / background, but Futaba had 25 teeth (14.4 degrees between each), and Hitec is transitioning to that design. 360 / 24 = 15 degrees between teeth.

5

Thanks for the insight,
15 degrees is way to much to solve the above described problem. Software-offset has side-effects, too.