Adaptive Equivalent-input-disturbance Approach to Improving Disturbance-rejection Performance
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ive Equivalent-input-disturbance Approach to Improving Disturbance-rejection Performance Ze-Wen Wang 1,2 Jin-Hua She 1,2,3 Guang-Jun Wang 1,2 1 School of Automation, China University of Geosciences, Wuhan 430074, China 2 Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan 430074, China 3 School of Engineering, Tokyo University of Technology, Hachioji 192-0982, Japan
Abstract: This paper presents an adaptive equivalent-input-disturbance (AEID) approach that contains a new adjustable gain to improve disturbance-rejection performance. A linear matrix inequality is derived to design the parameters of a control system. An adaptive law for the adjustable gain is presented based on the combination of the root locus method and Lyapunov stability theory to guarantee the stability of the AEID-based system. The adjustable gain is limited in an allowable range and the information for adjusting is obtained from the state of the system. Simulation results show that the method is effective and robust. A comparison with the conventional EID approach demonstrates the validity and superiority of the method. Keywords: Adaptive control, disturbance rejection, equivalent input disturbance (EID), linear matrix inequality (LMI), Lyapunov stability, root locus.
1 Introduction A large number of control methods have been proposed to improve disturbance-rejection performance[1–3]. In particular, many methods have devised to actively compensate for disturbances, such as the active-disturbance-rejection control (ADRC)[4–6], the disturbance observer (DO)[7, 8], and the equivalent-input-disturbance (EID) approach[9, 10]. The extended state observer (ESO) is widely used in the ADRC to deal with a disturbance[4]. Since the parameters in such a control system are hard to adjust, a linear method was presented to tune them in a simple way[11]. While the conventional ESO method is effective, it can handle only a chained system. This restricts its fields of application. The DO method is a frequency-domain method of estimating and rejecting to a disturbance[12]. The design of the DO is complicated because it requires a low-pass filter in the control system to ensure the causality and stability of the whole system, the disturbance-rejection performance of the system, and model matching between an actual and a nominal plant[7]. The DO method is simple and effective for a minimum-phase plant, but is hard to guarantee the stability of a non-minimum-phase plant. As one of the active disturbance-rejection methods, the EID approach makes use of the information on a Research Article Manuscript received January 8, 2020; accepted March 9, 2020 Recommended by Associate Editor Min Wu © Institute of Automation, Chinese Academy of Sciences and Springer-Verlag GmbH Germany, part of Springer Nature 2020
state observer to create a control signal on the control input channel that produces the same effect on the output as a disturbance does[13]. It does not require the i
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