Composite controller design for a 6DOF Stewart nanoscale platform

A composite controller combines of feedforward and feedback control for a 6DOF Stewart nanoscale platform driven by piezoelectric actuators is proposed. A hysteresis model derived by using a dynamic Preisach method is used for the feedforward control. A measurement method can directly measure the pose of the end-effector is developed to support the task-space on-line control in practice. An example of peg-in-hole insertion task is investigated. Lyapunov theory is used to search a stable PID-based controller whose optimal gain is found by using relay feedback test method and genetic algorithm. In experiment, conditions with/without external load are employed for performance evaluation. The composite controller is verified to be capable of improving position accuracy significantly.