Abstract
This paper presents a novel disturbance observer (DOB) for overcoming the limitation of uniformly bounded stability in existing DOB-based control systems and to attain asymptotic stability. The DOB is derived by considering the residual disturbance remaining after disturbance decoupling is performed. It focuses on the elimination of the residual disturbance as well as minimization of the estimation error. By considering the system state and the residual disturbance simultaneously in a Lyapunov stability function, the proposed DOB cancels the residual disturbance term and attains asymptotic stability. In contrast, existing DOBs consider these factors separately in different Lyapunov functions. A basic novel DOB is initially derived for achieving asymptotic stability and is later combined with the existing DOB. This forms a novel extended DOB that achieves a better estimation rate and better performance with regard to DOB-based control than those of existing DOBs.
Highlights
I N To achieve strong control performance by minimizing the effects of disturbances or uncertainties in actual industrial systems, a robust control strategy is considered mandatory [1]- [5].disturbance observer (DOB)-based control is one of the most commonly used robust control methods
Designing a DOB-based controller is conceptually easy since the disturbance decoupling process is different from nominal control processes in that they can be designed by assuming that the disturbance is completely decoupled; this is done by using the estimated disturbance obtained from the DOB [6]– [8]
This implies that the DOB can be used with any other control method, such as sliding mode control (SMC) or H∞ control [9]– [13], to improve its robustness by enabling the direct cancellation of the disturbance [14] [15]
Summary
I N To achieve strong control performance by minimizing the effects of disturbances or uncertainties in actual industrial systems, a robust control strategy is considered mandatory [1]- [5]. Author et al.: Preparation of Papers for IEEE TRANSACTIONS and JOURNALS the decoupling input To overcome this difficulty, a novel state-space DOB, which considers the residual disturbance and guarantees asymptotic stability, is proposed in this study. A novel DOB is developed by considering the residual disturbance and the states of a system when applying Lyapunov stability Thereafter, it is combined with the existing DOB that utilizes auxiliary variables, where the aim is to improve the convergence rate of the disturbance estimation method. In this way, the novel DOB achieves asymptotic stability and improved estimation performance. The DOB considered in this paper is one of the most commonly used DOBs due to its simplicity, which comes from its utilization of the auxiliary variable based on the state-space model [7]
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