Disturbance Observer Based Decoupling Control to Suppress Rotational Motion of Cross-coupled Gantry Stage

Gantry stages are being used in a variety of industrial applications requiring high speed and high accuracy. A cross-coupled gantry stage driven by two linear motors is disturbed by the cogging force because of the large thrust required and the crossbeam connecting the two linear motors acts as a mechanical coupling, which has an adverse effect on the synchronous control performance of the two motors. Although there are cogging forces and mechanical couplings, the two linear motors in the cross-coupled gantry stage must operate synchronously. For this purpose, the dynamics of the cross-coupled gantry stage are separated into a linear mode and a rotational mode. The dynamics of each mode is applied to the proposed disturbance observer based decoupling controller. The feature of the proposed controller is that each mode is designed for a independent purpose. Therefore, the linear mode controller is designed to suppress the cogging force and the rotational mode controller is constructed to eliminate the influence of mechanical coupling.