Use of least means squares filter in control of optical beam jitter

Meeting optical beam jitter requirements is becoming a challenging problem for several space programs. A laser beam jitter control test bed has been developed at the Naval Postgraduate School to develop improved jitter control techniques. Several control techniques, such as least means squares and linear–quadratic regulator were applied for jitter control. Enhancement in least means squares techniques to improve convergence rate was achieved by adding anadaptive biasfilter to the reference signal. In the experiments, the platform is vibrated at 50 and87Hz. In addition, a fast steering mirror is used to inject a random component of 200 Hz band-limited white noise. The experimental results demonstrated that the addition of the adaptive bias filter to the least means squares algorithm significantly increased the converging rate of the controller. To achieve the reduction of both sinusoidal and random jitter, a combination of least means squares/adaptive bias filter and linear–quadratic regulator is most effective. The least means squares/adaptive bias filter control is most effective for a sinusoidal jitter and the linear–quadratic regulator control for a random jitter. Nomenclature A = cross-coupling factor A, B, C, D = state–space matrices Dm = distance from source to mirro