It's explained on the video description:
In this research, a methodology for sensor-less full body active
compliance was used on a 6-DOF RSS (Rotary-Spherical-Spherical)
parallel manipulator. The manipulator can detect and comply with the
external forces on any part of its body without using any explicit
force/torque sensor at the joint or the end-effector. ...
You can use this code in MATLAB:
x = 0:0.1:20;
y = dsigmf(x,[1 4 1 16]);
I came back to this question and thought a bit more about it because of your bounty - typically the bounties are offered from a point of desperation, and I hate that feeling myself.
I think probably your code is fine, in looking at it. There are things that I'd do differently, like scaling your PID output by the time step, but you could distribute that ...
I can add one more point to RowanP's excellent list: the servo's PID is unreliable, not because of a defect, but because it is mistuned for your application.
Recall that tuning a PID control is arcane, if not entirely a black art. The servo manufacturer tuned the control PID coefficients for some use case, perhaps moving RC aircraft control surfaces. That ...
I had a few ideas about what might cause the jitter action you showed in the video. I suggest you'll need to be more specific in the information provided to enable more specific answers.
Idea 1 - Movement Boundaries Conflict
Is the joint trying to move past a physical boundary? When constructing your robot arm for the first time, the servos need to be in a ...
This is probably a formula to model what is called "Adverse yaw" in aircraft dynamics. It is a very popular factor - along with Dutch Roll - in terms of fixed-wing aircraft design and control, as it causes the vehicle to make an undesired movement.
In terms of a quadcopter here is what I think: When you perform a "roll" maneuver, the ...