This paper presents a new control strategy that combines classical control and an optimization scheme to regulate the output voltage of the bidirectional converter under the presence of matched and mismatched disturbances. In detail, a control-oriented modeling method is presented first to capture the system dynamics in a common canonical form, allowing different disturbances to be considered. To estimate and compensate for unknown disturbances, an extended state observer (ESO)-based continuous sliding mode control is then proposed, which can guarantee high tracking precision, fast disturbance rejection, and chattering reduction. Next, an extremum seeking (ES)-based adaptive scheme is introduced to ensure system robustness as well as optimal control effort under different working scenarios. Finally, comparative simulations with classical proportional-integral-derivative (PID) control and constant switching gains are conducted to verify the effectiveness of the proposed adaptive control methodology through three case studies of load resistance variations, buck/boost mode switching, and input voltage variation.

In this paper, a novel design of an energy regeneration system was proposed for recovering as well as reusing potential energy in a boom cylinder. The proposed system included a hydraulic pump/motor and an electrical motor/generator. When the boom moved down, the energy regeneration components converted the hydraulic energy to electrical energy and stored in a battery. Then, the regenerated energy was reused at subsequent cycles. In addition, an energy management strategy has been designed based on discrete time-optimal control to guarantee position tracking performance and ensure component safety during the operation. To verify the effectiveness of the proposed system, a co-simulation (using MATLAB and AMESim) was carried out. Through the simulation results, the maximum energy regeneration efficiency could achieve up to 44%. Besides, the velocity and position of the boom cylinder achieved good performance with the proposed control strategy.

This work presents a new disturbance observer-based chattering-attenuated terminal sliding mode control for a class of nonlinear systems in the presence of both mismatched and matched disturbances. A nonlinear disturbance observer is typically employed to accurately estimate mismatched disturbances. In this study, a terminal sliding mode control was designed, based on the disturbance estimation results, to counter the effects of disturbances and ultimately stabilize the target system. The utilization of a chattering-attenuated full-order terminal sliding mode structure satisfactorily resolves both chattering and singularity problems in controller design. It was shown by theoretical analyses that both the disturbance estimation error and the system state converge to the equilibrium point in finite time. Two simulation studies, namely a numerical example and an application to an electro hydrostatic actuator system, were conducted to examine the characteristics and to verify the effectiveness of the proposed algorithm.

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A good suspension system is of paramount importance to the operating performance of a vehicle and, consequently, to the safety and driving comfort of the passengers. Nevertheless, suspension systems are commonly susceptible to nonlinearity, parameter uncertainty, and exogenous perturbation, which can easily impair their effectiveness. This study first employs a full state feedback super twisting control (FS-STC) to stabilize both vertical displacement and pitch angle of a half-car suspension system in the presence of disturbances. FS-STC inherits the robust property of sliding mode control (SMC) while effectively attenuating the chattering phenomenon as one of its attractive features. However, FS-STC strictly requires both direct displacement and velocity state feedback, which implies additional sensors have to be installed, thus increasing the complexity of the physical structure and being prone to measurement noises. Therefore, a higher order sliding mode observer (HOSMO) based STC (HOSMO-STC) and an unscented Kalman filter (UKF) based STC (UKF-STC) are subsequently proposed to tackle this state availability problem. HOSMO estimates velocity states, thus reducing the dependence on state feedback for STC design. Meanwhile, UKF implementation takes further actions by utilizing more common and easily accessible relative displacements such as suspension strokes to estimate all concerned system states. Comparative simulation results demonstrate that UKF-STC offers better performance in terms of both convergence accuracy and chattering alleviation compared to FS-STC and HOSMO-STC while requiring the least information of state feedback.INDEX TERMS Half-car suspension, higher-order sliding mode observer, super twisting control, statefeedback critical, unscented Kalman filter.