Research on the degree of freedom control strategy for redundant-drive shaking tables

Redundant-drive shaking tables composed of more than one shaking tables are indispensible test equipments for anti-seismic study of long-span structures and are experiencing rapid development recently. However, the control strategy of the shaking tables system is greatly complex and there isn´t a common accepted method now. This paper proposed two degree of freedom(DOF) control strategies for the shaking tables system composed of two identical redundant-drive electro-hydraulic servo shaking table: six DOFs control strategy and twelve DOFs control strategy. According to different control principles, build two kinds of coordinates, derive the geometric motion relationship of the platform or load and the hydraulic cylinders, and then use zero-position geometric linearity technique to obtain simplified coordinate transformation matrixes between platform or load motion space and the hydraulic cylinders space. The control system model with DOF control strategy and dynamic model of the shaking tables are built using the Matlab/Simulink and SimMechanics software. Simulation experiments are carried out and the test results indicate that both the control strategies can realize the accurate motion of the platform and verify the feasibility and validity of the proposed control strategies. In the end, this paper compared the two DOF control strategies and analyzed the advantages and disadvantages of each control strategy.