Adaptive optimal filtering applied to laser pointing and tracking
Abstract
An adaptive extended Kalman filter (EKF) is used in an Adaptive Laser Optics Techniques (ALOT) control loop to track the glint from a spherical target. A fourfold improvement in tracking bandwidth is obtained over a conventional conical scan ALOT tracking loop implemented with the same hardware. The increase in tracking bandwidth is manifested in the ratio between the (conical scan) dither frequency and the tracking bandwidth, which is 2.5:1 for the EKF and 10:1 for the conventional analog or digital glint tracking schemes. The EKF provides correct pointing error estimates over essentially the entire range of the pointing error, whereas in a conventional conical-scan-loop the demodulated error versus true pointing error function is highly nonlinear due to the nonlinearity of the glint. This results in a demonstrated ability of the EKF to track a larger amplitude disturbance than the conventional conical-scan-loop. Adaptive schemes are employed to make the estimation algorithm insensitive to fluctuations in the mean level of reflected intensity and to variations in the strength of measurement noise.
- Publication:
-
In: Joint Automatic Control Conference
- Pub Date:
- 1977
- Bibcode:
- 1977auco....2.1214L
- Keywords:
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- Adaptive Optics;
- Kalman Filters;
- Laser Ranger/Tracker;
- Pointing Control Systems;
- Tracking (Position);
- Dithers;
- Feedback Control;
- Minicomputers;
- Riccati Equation;
- Targets;
- Lasers and Masers