Velocity and disturbance observer for non-model based load and friction compensation

In this paper, a scheme for the simultaneous estimation of the external forces acting on a rigid body together with its velocity is presented. This estimation scheme is based only on the knowledge of the position information and it allows to compensate undesired effects acting on the rigid body, like friction or external unknown loads, without requiring any knowledge of these spurious effects. This goal is achieved by means of two interacting observers, one for the observation of the generalized momenta and another for velocity observation. This compensation scheme can be also used to give to the system the desired dynamics, therefore avoiding the problem of parameter uncertainties. The effectiveness of the proposed scheme is proved both in simulation and experimentally, with a laboratory setup composed by a linear electric drive.