Control of Hydraulic Devices, an Internal Model Approach

Hydraulic Devices are used, where high forces must be generated by small devices. A disadvantage of these devices is the nonlinear behavior, especially of big devices, which are used e.g. in steel industries. Since one cannot measure the whole state in these applications, an output feedback controller is presented, which is based on a reduced observer. In addition disturbance forces, which can be described by exosystems, are taken into account. Their effect is eliminated in the steady state by the internal model approach. The presented design is applied to the hydraulic gap control of mill stands in rolling mills, such that unknown varying disturbance forces and forces caused by eccentricities of the rolls are rejected