Dynamics Decoupling Control of Parallel Manipulator

Due to the eccentric load of parallel manipulator, dynamic coupling occurs between the various degrees of freedom. As a typical parallel mechanism, the dynamic model of redundant shaking table is built. Coupling force observaction based on coupling model is introduced to the DoFs control structure. The coupling forces are controlled as disturbance forces on hydraulic system by distributing it to each actuator through Jacobi matrix transformation. Decoupling control is given based on the dynamic model as well as a feed forward disturbance force compensation control strategy. However, due to the fact that differentiating acceleration which contains large noise is needed in decoupling control based on dynamic model, modal decoupling control is given. Modal equation of redundant shaking table is given by considering hydraulic cylinder as a hydraulic spring. Through standard modal matrix and its inverse matrix, the redundant shaking table is controlled in non-coupling modal space instead of DoFs space. By analyzing the relationship between the modal matrix and the coupling characteristics of different modal DoFs, an experimental method is given for determining the modal matrix. Simulation analysis shows that compared with decoupling control based on dynamic model, the modal space decoupling control can more effectively reduce the dynamic coupling among DoFs of the redundant shaking table. A control system of the redundant shaking table is developed using rapid control prototyping technology based on xPC Target. Detailed experimental analysis and research are carried out on the proposed coupling characteristic analysis and decoupling control strategies. Experimental results demonstrate that the proposed decoupling control strategies are effective and advanced.