Design and modeling of decoupled miniature fast steering mirror with ultrahigh precision

To address the problem of low tracking precision caused by mechanical cross-coupling between the axes of a two-degree-of-freedom fast steering mirror (FSM), this study introduces an ultrahigh precision decoupled miniature fast steering mirror (MFSM) realized in a tiny volume. The proposed MFSM is driven by piezoelectric actuators and guided by a ring-type flexible hinge to achieve high-precision deflection and kinematic decoupling. A theoretical analysis of rotational stiffness was conducted to perform a detailed decoupling design. The output angle of the mirror was then evaluated. The relationship between the input voltage and the output angle was determined by modeling the dynamic characteristics of the MFSM. Owing to the mechanical decoupling property of the MFSM, two independent proportional-integral-derivative (PID) controllers were used separately for axis control, and experiments on trajectory tracking control were performed. The experimental results revealed that the angle traveled for more than +/- 2 mrad for both axes, with an ultralow coupling ratio of less than 0.64 parts per thousand. The underload natural frequency exceeded 3.24 kHz. The mirror exhibited a good closed-loop tracking accuracy, as indicated by the tracking error, which was less than 1 grad for both the one-degree-of-freedom and two-degree-of-freedom trajectory tracking control.