Robust Fuzzy Control of Uncertain Two-axis Inertially Stabilized Platforms Using a Disturbance Observer: A Backstepping-based Adaptive Control Approach

kground and Objectives: The two-axis inertially stabilized platforms (ISPs) face various challenges such as system nonlinearity, parameter fluctuations, and disturbances which makes the design process more complex. To address these challenges effectively, the main objective of this paper is to realize the stabilization of ISPs by presenting a new robust model-free control scheme.Methods: In this study, a robust adaptive fuzzy control approach is proposed for two-axis ISPs. The proposed approach leverages the backstepping method as its foundational design mechanism, employing fuzzy systems to approximate unknown terms within the control framework. Furthermore, the control architecture incorporates a model-free disturbance observer, enhancing the system's robustness and performance. Additionally, novel adaptive rules are devised, and the uniform ultimate boundedness stability of the closed-loop system is rigorously validated using the Lyapunov theorem.Results: Using MATLAB/Simulink software, simulation results are obtained for the proposed control system and its performance is assessed in comparison with related research works across two scenarios. In the first scenario, where both the desired and initial attitude angles are set to zero, the proposed method demonstrates a substantial mean squared error (MSE) reduction: ۹۶.۲% for pitch and ۸۶.۷% for yaw compared to the backstepping method, and reductions of ۷۵% for pitch and ۳۳.۳% for yaw compared to the backstepping sliding mode control. In the second scenario, which involves a ۱۰-degree step input, similar improvements are observed alongside superior performance in terms of reduced overshoot and settling time. Specifically, the proposed method achieves a settling time for the pitch gimbal ۵۶.۶% faster than the backstepping method and ۵۸% faster for the yaw gimbal. Moreover, the overshoot for the pitch angle is reduced by ۵۳.۵% compared to backstepping and ۳۵.۵% compared to backstepping sliding mode control, while for the yaw angle, reductions of ۴۳.۶% and ۳۷.۶% are achieved, respectively.Conclusion: Through comprehensive simulation studies, the efficacy of the proposed algorithm is demonstrated, showcasing its superior performance compared to conventional control methods. Specifically, the proposed method exhibits notable improvements in reducing maximum deviation from desired angles, mean squared errors, settling time, and overshoot, outperforming both backstepping and backstepping sliding mode control methods.

کلیدواژه ها:

Inertially Stabilized Platform ، Backstepping Control ، Disturbance observer ، Fuzzy Approximation ، Model-free Control