A robust control strategy for an unstable mechanical system

The unstable mechanical system used to test the robust control strategy is a beam and ball system. The main nonlinearities are due to stiction and friction in the servomotor which moves the beam, the main uncertainties are due to the ball size variations. The beam position is perturbed by external disturbances acting on the beam. The proposed robust control strategy compensates the static friction by acting on the supply voltage of the motor, makes the behavior of the beam almost independent of the ball size variation, makes the system behavior insensible to external disturbance by the online compensation of their estimated value. Simulation and experimental tests confirm the validity of this approach.