Modal space three-state feedback and feedforward control for 2-DOF electro-hydraulic servo shaking table with dynamic coupling caused by eccentric load

Abstract

Shaking table is a device to simulate the vibration environment, which is used to test the reliability and seismic resistance of many products. However, the control performance of the shaking table is restricted by the serious output coupling caused by eccentric load. In order to solve the coupling problem, a new control strategy, modal space three-state feedback and feedforward control, is proposed. For a 2-DOF electro-hydraulic servo shaking table, its kinematics model and dynamics model with eccentric load are built. And then, the dynamic coupling is analyzed, which makes it impossible for each channel to be controlled independently. To avoid the effect by coupling, a modal space control framework is established based on the vibration theory and the decoupling characteristics of the modal space are researched. In modal space, although a controller of each channel can be designed dependently, the ultimate requirements are decoupling for channels in the degree of freedom space, so it is necessary to discuss the mapping relation between traditional physical space and the presented modal space. The effect of modal channel consistency on the decoupling for physical space is revealed. Furthermore, the correlation of the frequency responses between the two spaces is also analyzed. To meet the obtained conclusions of modal space, a modal space three-state feedback and feedforward controller is designed for improving the dynamic performance and the consistency of modal channels. The experimental results show the correctness of the theoretical analysis, and validate that modal space three-state feedback and feedforward control method is effective, which can significantly reduce the output coupling for the 2-DOF electro-hydraulic servo shaking table with eccentric load.