Micro position control of a 3-RRR compliant mechanism

A planar parallel compliant mechanism based on 3-RRR kinematic structure is designed to be used as a micro positioning stage. The position of the center is measured by using a laser position sensor and the mechanism is actuated by piezoelectric actuators. The stage displacements are analyzed by using structural Finite Element Analysis (FEA). However the experimental displacement results for the manufactured mechanism are not compatible with the FEA which means that we have errors due to manufacturing, assembly etc. A position control using Sliding Mode Control with Disturbance Observer is proposed for the reference tracking of the center of the stage. Piezoelectric actuator linear models are used for disturbance rejection. Finally, the position control of the mechanism is succeeded although it has inadmissible errors compared to FEA.