Controller design and experimental investigation of a 3-universal-prismatic-universal compliant manipulator for active vibration isolation

For low frequency signals under 10 Hz, effective control methods are urgently needed to realize active vibration control for precision instruments. Based on our previous works on design and dynamical modeling of micro-parallel manipulators, a mixed H 2 / H ∞ control model is proposed for controlling a compliant three universal-prismatic-universal (3-UPU) parallel platform in this paper, which is established in a state-space framework considering the stiffness of flexure hinges. Moreover, other control methods in terms of LQR, H2and H ∞ are approached for a multiple-input and multiple-output (MIMO) active vibration isolation system, and the mixed H 2 / H ∞ method has proved more effective than the three methods mentioned above. Finally, an experimental system is built up to implement the active vibration control using an improved 3-UPU compliant parallel manipulator prototype. With the hardware and software developed, the real-time active vibration control methods have been tested at random signals; frequency rates at 0.5 Hz and 1 Hz are selected for illustrations. The experimental results demonstrate that the vibrations acting on the base and the moving platform are significantly reduced, and are limited to 0-10 Hz vibration signals. This active vibration control system provides a reliable experimental platform for validating the theoretical analysis work.