This article proposes a comprehensive approach to achieve high-precision modeling, high bandwidth, and robust control for the voice coil actuator fast steering mirror (VCA-FSM). This approach includes the Hankel matrix identification method, $H_{\infty }$ sensitivity control, disturbance observer (DOB), and zero phase error tracking control (ZPETC) algorithms. The superiority and practicality of the proposed control techniques are discussed by comparing control methods, such as $H_{\infty }$ , sliding mode control (SMC), linear-quadratic-regulator (LQR), and proportional-integral-derivative (PID) through experiments. Especially, this proposed method serves as a good guide for controller designs of other servo mechanisms.

Fast steering mirrors (FSMs) have been used for decades to improve the performance of electro-optical imaging systems, such as airborne imaging systems and space-based optical surveillance systems. With the advantage of increasing the accuracy of image motion compensation and the efficiency of scanning imaging, backscanning step-and-stare imaging has become the main approach to realizing wide-area surveillance for airborne imaging systems. According to the operating mode and motion profile of the FSM in the imaging system, a combined optimized profile (COP) is designed to avoid abrupt changes in the velocity and acceleration of the FSM. The angular position sensor based on a four-quadrant detector is used in FSMs to expand the measuring range and cut the cost at the expense of larger measurement noise. Combining a Kalman filter with a disturbance observer and zero-phase error tracking control, a control method is proposed to improve the control precision and bandwidth while suppressing measurement noise. Simulation and experimental results show that the profile designed by COP is smooth enough to meet the special requirements of FSM’s backscanning image motion compensation and that the Kalman filter-based FSM control method can significantly improve the control accuracy.

The alignment accuracy and stability of shipborne electro-optical system are affected by external attitude disturbance and internal non-linear disturbance. Therefore, this study examined a new digital sliding mode control based on a novel reaching law with an n-order disturbance compensator to solve this problem. Specially, the proposed novel reaching law was a chatter-free method, in which, as the switching gain was replaced by an adaptive function, chattering on the sliding surface tended to zero. For perturbed systems, the new sliding mode controller was able to guarantee a narrow quasi-sliding-mode domain and the ultimate width was the order of O(T3), such that the narrower the quasi-sliding-mode domain width was, the more robust toward nonlinear disturbances. Both mathematical calculations and simulations verified the convergence and stability of the new controller. Finally, based on a compound control strategy that combined feedforward control with a sliding mode control position loop and proportional-integral velocity loop control structure, shipborne equivalent dynamic target tracking experiments were performed. The results, compared with existing controllers, showed that the robustness of the new controller to nonlinear disturbances was stronger and the tracking system accuracy clearly improved, while the influence of sliding mode chattering on the system was avoided.

In this study, a sliding mode control (SMC) algorithm was proposed based on a novel reaching law to solve the nonlinear disturbance problem of a ground-based laser communication turntable. This algorithm is a chatter-free method, in which the coefficient of sliding mode variable structure function is designed as an adaptive function, so the chattering of the sliding mode approaches zero. For any perturbed system, this algorithm can ensure a finite time for the system state to reach the sliding mode surface from any initial state. Additionally, the system will stabilize in the quasi-sliding mode domain (QSMD) with O(T³) width, where a narrower QSMD width corresponds to stronger robustness toward nonlinear disturbances. Both mathematical calculations and simulations verified the sliding mode and stability of this control algorithm. Experimental results of the velocity closed-loop of pitch axis show that the proposed algorithm effectively improved the anti-nonlinear disturbance ability of the control system compared with the effects of the traditional digital PID and the existing chatter-reduced SMC algorithms, for smooth system operation.

An effective control strategy is proposed in this article to address the issue of controller performance degradation caused by parameter perturbations in voice coil actuator fast steering mirror (VCA-FSM). The strategy employs loop shaping to design a performance controller that ensures high tracking accuracy and bandwidth, utilizes $\mu$-synthesis to design a robust controller that mitigates performance degradation due to parameter perturbations. These two control methods are integrated within a generalized internal model control framework. Experimental results validate that this control strategy can effectively suppressed the impact of parameter perturbations on the controller performance, and at the same time significantly enhance robust stability and robust performance while maintaining the desired performance levels.