Adaptive Control of a Piezo-Actuated Steering Mirror to Restrain Laser-Beam Jitter

Tracking, pointing, and imaging performances of precision laser systems are restricted by laser-beam jitter, which is time varying or uncertain. This paper proposes an adaptive control that uses a piezo-actuated steering mirror to actively resist the jitter and achieve precise pointing. First, in order to realize the single-valued linear input-output relationship, which can simplify the adaptive-control design and improve the stability and convergence rate of the adaptive filter algorithm, the hysteresis non-linearity of the piezo-actuators is feedforward compensated. Then, an adaptive controller is built based on an adaptive lattice recursive least-square filter that identifies the disturbance statistics in real-time by utilizing sensor data from a position sensing detector. The developed controllers are verified on a jitter-control system. Experimental results demonstrate that the adaptive-control method significantly extends the disturbance-rejection bandwidth, and that the control performance surpasses the conventional proportion-integral-differential (PID) control method.