Modal Space Feedforward Control for Electro-Hydraulic Parallel Mechanism

As a parallel mechanism with six-degree-of-freedom, an electro-hydraulic shaking table is endowed with strong coupling characteristics among different degree-of-freedoms. When the electro-hydraulic shaking table moves to one direction, there will be some unnecessary related motions in other directions, which will affect the tracking accuracy. The kinematics model, the dynamic model, and the electro-hydraulic model are all established based on analyzing the components and working principles of the electro-hydraulic shaking table. After that, a modal space controller is built on the basis of a three-variable feedback controller by relying on the designed modal space matrix on the premise of modal control theory. In this regard, a multiple-input multiple-output system with strong coupling within the physical space is transformed into a set of single-input single-output systems independent from each other within the modal space. Moreover, the accuracy of vibration control can be improved by introducing a discrete feedforward controller. It is evident from the experimental results that the proposed control strategy can effectively improve the accuracy of vibration control.