Internal Disturbance Estimation and Its Compensation for Pre-Installed Velocity Controller for Crane System

Abstract

This paper proposes a method for estimating disturbances, which is added in the control loop of a crane with a preinstalled velocity controller, from the input-output relationship of the velocity control system. The controlled plant is a mechanically-configured velocity control system using a flow control valve. A type-1 disturbance observer was designed for the controlled plant including the velocity controller. The model parameters were identified from actual crane systems. The disturbance is assumed to be the disturbance torque generated by the wind and swaying of the suspended load applied to the crane boom. However, to avoid loss of generality, the disturbance is estimated in the dimension of angular acceleration, which is almost equivalent to torque. By feeding back the estimated disturbance via the inverse system of the velocity controller, the disturbance applied inside the controlled plant could be compensated using inputs of different dimensions.