Inner coupling force analysis and suppression for redundant-drive hydraulic shaking tables

The table array system errors of redundantly-driven electro-hydraulic shaking tables not only lead to inner coupling force in each shaking table, but also lead to inner coupling forces between shaking tables. The inner coupling forces can reduce the net output force of the system and even may damage specimens. Here, the redundantly driven parallel mechanism dynamics was used to analyze the formation mechanism of the inner coupling force and establish the model of the inner coupling force. The mathematical relationship equations for inner coupling forces in a shaking table and those between shaking tables versus installation errors, displacement measurement errors and servo valve zero-bias of the system were derived. The influence mechanism of the errors mentioned above on the inner coupling forces was analyzed quantitatively. The inner coupling force synthesis matrix and the generalized forces of all DOFs. synthesis matrix were derived applying the dynamics relations and then the inner coupling force suppression controllers based on proportional-integral controllers were respectively designed according to the influence mechanism and the formation mechanism of the inner coupling forces. The dynamic model of a shaking table array system was built using the software SimMechanics and its control model was built using Simulink. The co-simulations were performed and the simulation results indicated that the analysis of the shaking table array system's inner coupling forces is right and the proposed control strategies can reduce the inner coupling forces effectively.