Experimental system identification and feed-forward control of a 2-DOF flexure-based mechanism

The work presented in this paper focuses on the system identification of a 2-DOF flexure-based mechanism, designed for micro/nano scale positioning and manipulation. In the presented compliant mechanism, the cross axis coupling ratio is below 1% indicating excellent decoupling performance. The system identification procedure, experimental design, data collection, data analysis, and validation of the identified system are detailed in this paper. A linear sine swept signal over a range from 1 Hz to 1000 Hz is applied to the system as an input. Laser interferometry-based sensing and measurement technique is used to measure the response of the system. The experimental data is used to evaluate the transfer function of the system in the X and Y axes. The first natural frequency of the 2-DOF mechanism in the X and Y axes are estimated using the identified models, which are found out to be 557 Hz and 545 Hz respectively. Validation data is collected and used to verify the accuracy of the identified model. The error between the predicted output of the identified model and the experimental response is found to be less than ±10%, mostly resulted from actuator hysteresis. Further, a feedforward controller is implemented to track a 1-DOF smooth multiple-frequency trajectory.