Stabilization of a Double Pendulum with a Soft Spring

With the soft spring it is now longer feasible to view the dynamics added by the spring as unmodeled high-frequency dynamics. In this case, the controller has to be designed for the full double pendulum including the spring dynamics. This is most easily done with a Hinf controller. The video clip shows the stabilized inverted pendulum in this case. The oscillations are caused by viscous friction within the spring. This can be convincingly proven by switching on and off the Coulomb friction in the simulation model and shows the power of an accurate simulation.