Control of a differentially flat 2D overhead crane using the ADRC philosophy

In this paper a novel control method for a 2D overhead crane is investigated. This system although nonlinear is differentially flat, which is utilized during the control, namely it can be exactly linearized by a dynamic state feedback and coordinate transformation. However for acceptable performance, this method requires precise knowledge of the parameter values, which generally is not feasible if the crane moves loads of varying masses. The contribution of the paper is an augmented controller that besides exact linearization also applies the active disturbance rejection control (ADRC) method with virtual inputs that results in a robust closed loop. Simulations with different loads show improvement in the tracking performance and stability.