Abstract
U-model, which is a control-oriented model set with the property of generally facilitate nonlinearity dynamic inversion/cancellation, has been introduced to the Disturbance Observer-Based control (DOBC) methods to improve the performance of the nonlinear systems in this paper. A general DOB based U-Control (DOBUC) framework is proposed to improve the disturbance attenuation capability of U-controller for both linear and nonlinear systems combined with (based on) the U-model-based dynamic inversion which expands the classical linear disturbance observer control to general nonlinear systems. The proposed two-step DOBUC design procedures in which the design of DOB and U-controller are totally independent and separated, enables the establishment of global exponential stability without being subject to disturbances and uncertainties. Comparative simulation experiments with Nonlinear DOBC in controlling Wind Energy Conversion Systems (WECS) and Permanent Magnet Synchronous Motors (PMSM) demonstrated the proposed method.
Highlights
It is believed that unknown system uncertainties and disturbances universally exist in various engineering control systems [1]
Motivated by the advantages of the U-control and the frequency-domain Disturbance Observer (DOB), this paper aims to develop a nonlinear DOB design, which is analogous to the conventional frequency-domain DOB
There are two main challenges in Wind Energy Conversion Systems (WECS) [25]: complex nonlinear dynamics and difficult to measure actual wind speed in real-time application [26,27,28] collect the latest research on advanced control and optimization examples of wind energy systems [18] first proposed a continuous-time U-control system for wind energy conversion
Summary
It is believed that unknown system uncertainties and disturbances universally exist in various engineering control systems [1]. If one can construct the inverse dynamic of nonlinear systems, the lumped disturbance can be estimated directly using the difference between system input and calculated input Another aspect of DOBC is the baseline controller designed to satisfy the required system performance specifications. Based on the simulation experiments, it verifies the efficiency of UM based dynamic inversion algorithm can be applied into affine nonlinear system, and non-affine nonlinear system This offers the possibility of extending the idea of frequency-domain DOB into a new disturbance estimation approach using the difference between system input and calculated input. The first one is to propose a new nonlinear DOB design method, extend the idea of conventional frequency-domain DOB be applicable to nonlinear system, which can integrate all external disturbances and internal modelling uncertainties as system input error, whereas the conventional time-domain nonlinear DOB estimates the disturbance in system state variables’ channel.
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