In this paper, the theory of control is considered on nonlinear systems. A closed-loop controller with a strong idea has been introduced to track system states and guarantee asymptotically stability. The proposed method is the indirect terminal sliding mode control technique based on adaptive and fuzzy rules, which has used the continuous barrier function as a new approach in its design to improve the performance of this controller. One of the significant challenges in the sliding mode control method is the chattering phenomenon due to the discontinuous sign function in the control law. In the proposed approach, the control law is obtained continuously and smoothly due to the mentioned continuous function and subsequently solves the chattering problem. Another feature of the proposed method is the asymptotical stability of the system dynamics within finite time, which is proved based on the Lyapunov function. The proposed Lyapunov function includes the function of fractional power of a sliding surface. On the other hand, the obtained control law using the sliding mode method is estimated using the fuzzy system. The adaptive approach adjusts the fuzzy law parameters and the unknown bound of external disturbance.INDEX TERMS Finite-time stability, Continuous barrier function, Sliding mode, Fuzzy estimator.
It is generally known that, with conventional PI control, the stability and dynamic response performances of a power converter cannot be optimized simultaneously. To overcome this limitation, an uncertainty and disturbance estimator assisted sensorless load current feedforward control for dc‐bus voltage regulation is presented to achieve fast dynamic response to load variations while stability is guaranteed by tuning PI controller. The proposed control scheme is verified on a cascaded converters system comprising a front end dc‐dc DAB converter followed by a single‐phase inverter as an illustrative case. Load‐current feedforward is used to enhance the transient response of the front end DAB converter while an uncertainty and disturbance estimator is used to compensate for any non‐idealities arising from model uncertainties and error in load current estimation. To validate the proposed control scheme, experimental results obtained from a 250‐W cascaded converter system are presented and compared rigorously to the performance of conventional PI control.
A non-intrusive method to estimate the values of power-stage components online and autotuning of feedback compensator for digitally controlled power converters is presented in this study. By using buck converter as an example, the presented autotuning controller has been designed to cover the wide-range variations in equivalent series resistance zero of the output capacitor and the resonant frequency of output filter L o C o. These two frequencies are estimated by examining the converter's quasi-impulse response during start-up and by measuring the output-voltage ripple during steady-state operation of the converter. Hence, due to the non-intrusive characteristic of the proposed control method, the operation of the converter is not affected. Using the acquired results, the online digital compensator is tuned automatically based on predefined crossover frequency and phase margin to provide the required output-voltage regulation and transient response under wide-range variations in the power-stage component values. To validate the effectiveness of the proposed control method, experimental results from a 12 to 1.5 V buck converter are presented.
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