A SAKF-Based Composed Control Method for Improving Low-Speed Performance and Stability Accuracy of Opto-Electric Servomechanism

The opto-electric servomechanism (OES) plays an important role in obtaining clear and stable images from airborne infrared detectors. However, the inherent torque disturbance and the noisy speed signal cause a significant decline in the inertial stability accuracy and low-speed performances of OESs. Traditional linear control schemes cannot deal with the nonlinear torque disturbance well, and the speed obtained by the finite difference (FD) method cannot effectively balance the tradeoff between the noise filtering and phase delay. Therefore, this paper proposes a strap-down stability control scheme, in the combination of a proportional-integral(PI) controller and a state-augmented Kalman filter (SAKF), where the PI is used to regulate the linear part of the servomechanism, and with the SAKF performing torque disturbance observation and speed estimation simultaneously. The principle and the implementation of the controller are introduced, and the tuning guidelines for the controller parameters are presented as well. Finally, the experimental verifications based on OESs with three transmission types (i.e., the direct-driving, the harmonic-driving, and the rotate vector-driving(RV-driving) OESs) are carried out respectively. The experimental results show that the proposed control scheme can perform better speed observation and torque disturbance compensation for various types of OESs, thus effectively improving the low-speed performance and stability accuracy of the mechanism.