Articles
Publication Date: 2024
IET Renewable Power Generation (17521416)18(14)pp. 2629-2640
This research proposes the application of fractional-order sliding mode control (FOSMC) at the primary controller level to improve the stability of an islanded microgrid by adjusting its voltage and frequency. The control strategies used in the microgrid are performed in two levels (primary and secondary) in the islanded mode. Practically, most previous studies have worked to improve the primary controller. Droop control is one of the most commonly used methods at the primary level and is adopted in this study as well. The sliding mode control (SMC) strategy is normally used to control linear equations. Thus, the non-linear microgrid equations were transformed into some linear ones using the input-output feedback linearization technique. Further, a fractional sliding surface was acquainted. The sliding surface and FOSMC were designed to reject system uncertainties and organize the voltage and frequency. Design parameters were chosen using the Lyapunov stability theorem. The validation of the proposed method using Simulink-MATLAB confirms its effectiveness in enhancing level power sharing, regulating frequency, and maintaining voltage stability across the system. © 2024 The Author(s). IET Renewable Power Generation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Publication Date: 2023
Computers and Electrical Engineering (00457906)105
A variation in load on a microgrid (MG) system has a significant impact on the MG's frequency. In addition, wind and photovoltaic power sources are significantly affected by weather fluctuations; thus, the system experiences frequent oscillations. This paper proposes an integral sliding mode control system that incorporates a disturbance observer (ISMCDO) for establishing a power balance and frequency regulation in a MG system. MATLAB/ Simulink is used to compare the results of this method and those of integral sliding mode controller (ISMC) and disturbance observer-based controller (DOBC). In addition, their performance indices are compared as well, where the results can verify the superiority of ISMCDO method in comparison with other techniques. Consequently, Utilizing the ISMCDO controller, the secondary controller performances in the MG system may be improved, which will ensure stability, flexibility, quick response, and maintenance of the load balance when sudden changes in loads and weather conditions occur. © 2022
Publication Date: 2023
IEEE Transactions on Industry Applications (00939994)60(2)pp. 2117-2126
Load frequency control (LFC) is a crucial application in modern power systems as it ensures the system frequency remains within an acceptable range through demand control and active power generation. However, as information and communication technology (ICT) becomes more prevalent in power system, there are both opportunities for improved reliability and efficiency as well as potential security threats. This article proposes an LFC approach that takes into account the simultaneous occurrence of false data injection (FDI) attacks on the sensor-controller side, disturbances in the states of the system and time delays in the controller-actuator side. To tackle these challenges, a slide mode observer is utilized to estimate system states and detect cyber-attack signals as an extra virtual state. Subsequently, a cyber-attack-resilient predictor slide mode controller is designed to establish a robust control law capable of overcoming system challenges, when all system states are not within reach. Therefore, the robust control law is designed based on the estimated states, cyber signal and measured system output. By integrating these techniques, the proposed methodology offers a promising solution to enhance the resilience and performance of power system faced with cybersecurity threats. It improves the response speed of the system and minimizes the maximum overshoot compared to some published resilience control laws, thereby ensuring secure and reliable load frequency control. Additionally, reducing the number of sensors in the system helps to reduce overall costs. Finally, the performance of the controller is also verified in real-time using the OPAL-RT simulator testbed. © 2023 Institute of Electrical and Electronics Engineers Inc.. All rights reserved.
Publication Date: 2022
ISA Transactions (00190578)126pp. 513-532
Crouch gait is a gait anomaly observed in youngsters with cerebral palsy (CP). Rehabilitation robots are useful for treating individuals with crouch gait. Multiple factors have impact on crouch, including contracture, spasticity, weak motor control, and muscle feebleness, which make the designing and controlling of these exoskeletons for this population a challenging job. A harsh kinematic trajectory enforced by an exoskeleton control strategy may place individuals with spasticity at a high risk of muscle tissue injury. Therefore, in this article, a multi-input multi-output (MIMO) control method is proposed to reduce this risk and improve crouch gait pattern. A constrained control law is used in the model since high power demands may threaten the wearer. In addition, the controller needs to be robust enough against external disturbances and uncertainties. Thus, a nonlinear disturbance observer (NDO) is presented to compute the wearer-generated muscular torque and the uncertainties in the modeling. In addition, a robust constrained MIMO backstepping sliding controller (CMBSC) based on NDO is used to deal with the effect of actuator saturation and uncertainties. A simulation test was used to validate the proposed model and controller. The results of Simulation confirmed the efficiency of the proposed control method when applied to crouch gait with subject specific gait reference. Then, some experimental tests were undertaken to validate the efficiency of the proposed controller. © 2021 ISA
Publication Date: 2019
MethodsX (22150161)6pp. 1838-1846
Exoskeletons are new robotic systems that are in close contact with the human body. Thus, their performances are influenced by many factors, including the selection of its structure, actuators, measurement devices, parameters, and mechanism of coupling to the human body. The latter offers numerous challenges to its design, evaluation and modification, including analyzing the effectiveness of the exoskeleton, finding the optimal force for actuators and, discovering the effect of changes in design parameters on human muscle behavior, which are very difficult to measure. Therefore, numerical simulations play an important role in solving these challenges and have the potential to improve treatment strategies and medical decision-making. In this study, a simulation-based method is presented for the designing and analysis of the parameters of an exoskeleton and its wearer's kinetics and kinematics. Model-based design software, including OpenSim and Inventor, and mathematical software, such as MATLAB, are integrated. This method can assist in the modification of exoskeleton devices and allow physiologists, neuroscientists, and physical therapists to generate new solutions for rehabilitation programs using exoskeletons. • Using the movements parameters of each individual subject in her/his exoskeleton design. • Combining the power of OpenSim body movement and the ability of Matlab in mathematical calculations. • Considering the effect of exoskeleton parameters on each muscle-skeleton movement. © 2019 The Authors
