Disturbance estimation and compensation for trajectory control of an overhead crane

This paper presents an observer based control concept for an overhead crane using feedforward and feedback controllers. All control system components have been derived in symbolic form. Therefore, gain scheduling can be utilized to take into account varying system parameters. According to a decentralized control structure, a multibody model is presented for the crane y-axis and the equations of motion are stated. Based on a linearized state space representation, a feedback control law is calculated analytically. The feedforward control design and observer based disturbance rejection are described in detail due to their importance concerning tracking accuracy. The nonlinear friction force acting on the trolley drive and disturbance force acting on the load surface are considered. The effectiveness of the developed control scheme is shown by selected experimental results at a 5t-bridge crane