Browsing by Author "Li, Dongyang"

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    Estimation of non-symmetric and unbounded region of attraction using shifted shape function and R-composition
    (Elsevier, 2022-09-21) Li, Dongyang; Ignatyev, Dmitry; Tsourdos, Antonios; Wang, Zhongyuan
    Sum-of-squares programming is widely used for region of attraction (ROA) estimations of asymptotically stable equilibrium points of nonlinear polynomial systems. However, existing methods yield conservative results, especially for non-symmetric and unbounded regions. In this study, a cost-effective approach for ROA estimation is proposed based on the Lyapunov theory and shape functions. In contrast to existing methods, the proposed method iteratively places the center of a shifted shape function (SSF) close to the boundary of the acquired invariant subset. The set of obtained SSFs yields robust ROA subsets, and R-composition is employed to express these independent sets as a single but richer-shaped level set. Several benchmark examples show that the proposed method significantly improves ROA estimations, especially for non-symmetric or unbounded ROA without a significant computational burden.
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    Nonlinear analysis for wing rock system with adaptive control
    (AIAA, 2021-12-29) Li, Dongyang; Ignatyev, Dmitry I.; Tsourdos, Antonios; Wang, Zhongyuan
    Adaptive control has the potential to improve the performance and reliability of aircraft. However, the inherent nonlinearity of adaptive control causes difficulty in stability and robustness verification which is critical before entry into service. In this paper, the region of attraction (ROA) estimation using sum of squares (SOS) technique is explored for adaptive control systems. The problem of wing rock suppression by a model reference adaptive control (MRAC) serves as a benchmark example to demonstrate the effectiveness of the method. Considering the potential disturbance presented in measurement signals, the operative range of aircraft must be included in the ROA of the control system. Therefore, the ROA is evaluated using SOS polynomial optimization under various combinations of design parameters in the adaptive law, including adaptation rate and sigma modification values. This gives insight into the interactions of design parameters on the adaptive control performance.
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    Nonlinear analysis for wing-rock system with adaptive control
    (AIAA, 2022-07-25) Li, Dongyang; Tsourdos, Antonios; Wang, Zhongyuan; Ignatyev, Dmitry I.
    Introduction The potential of adaptive control in improving the performance and reliability of control systems attracts researchers and engineers from different disciplines. However, the verification and validation of the flight control system regarding the modeling error, uncertainty, disturbance, and time delay is not an easy task due to the inherent nonlinearity of the problem as well as the lack of rigorous analysis tools for nonlinear systems [1–5].
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    Region of attraction analysis for adaptive control of wing rock system
    (Elsevier, 2021-11-01) Li, Dongyang; Ignatyev, Dmitry I.; Tsourdos, Antonios; Wang, Zhongyuan
    This paper introduces a numerical method for region of attraction (ROA) estimation of the adaptive control system in polynomial form. A classical adaptive controller with sigma modification on suppressing the wing rock motion is revisited. Using the nonlinear analysis technique based on the sum of squares optimization, ROA of the origin is computed with respect to the potential measurement error. The obtained result gives a solid guarantee on the allowable initial conditions where the adaptive controller is still able to suppress the wing rock motion. It provides confidence for the adaptive controller operating under some unforeseen conditions in practice.