Search Results (102)

Compared with the standard finite-set model-based predictive current control (FS-MPCC), the finite-set ultra-local model-based predictive current control (FS-ULMPCC) removes the use of actual system parameters and thus has some advantages like good robustness and easy implementation. However, the steady-state performance of FS-ULMPCC is relatively weak. In this paper, a novel FS-ULMPCC method is proposed and applied to the AC/DC converter of a direct-driven wind power generation system. The proposed method is designed based on a linear-extended state observer (LESO). In particular, a new control set reconstruction strategy is proposed to improve the steady-state performance. Only three options are included in the reconstructed control set, and each one is associated with two independent, active voltage vectors and their durations. The proposed FS-ULMPCC method is compared with the traditional one through experiments. The proposed method includes enhanced steady-state performance and reduced computational burden. Full article

The three-level neutral-point-clamped (NPC) active power filter (APF) is suitable for harmonic compensation in high voltage and large capacity applications. And, the harmonic compensation effect of APF depends on its dynamic performance and control. This paper propose a repeat proportional integral (PI) decoupling control strategy with linear active disturbance rejection (LADRC) to address the issues of detection in complex harmonic current and power supply current distortion when the nonlinear load varies. To simplify the design of LADRC, this paper adopts inverter current feedback control. Firstly, repeat control is introduced to optimize the traditional PI controller, which improves the compensation accuracy while ensuring the dynamic response capability of the control system. Then, to address the serious coupling of the system model in the d-q coordinate system, a reduced order linear active disturbance rejection (LADRC) control is introduced. The PI and linear extended state observer (LESO) control method is adopted in the outer voltage loop to maintain stable DC voltage and improve the ability to suppress voltage overshoot during grid connection. The effectiveness of this control method has been verified through MATLAB/Simlink. The results show that, compared with the repeat PI method, the control method based on repeat PI–LADRC can achieve better decoupling control, improve robustness and anti-interference ability, enhance the performance of the original system, and can significantly improve the harmonic suppression capability of the APF. Full article

A combined control method integrating Linear Active Disturbance Rejection Control (LADRC) and Sliding Mode Control (SMC) is proposed to mitigate model uncertainty and external disturbances in the attitude control of fixed−wing unmanned aerial vehicles (UAVs). First, the mathematical and dynamic models of a small fixed−wing UAV are constructed. Subsequently, a Linear Extended State Observer (LESO) is designed to accurately estimate the model uncertainties and unidentified external disturbances. The LESO is then integrated into the control side to enable the SMC to enhance the control system’s anti−interference performance due to its insensitivity to variations in−system parameters. The system’s stability is proven using the Lyapunov stability theory. Finally, simulations comparing the classical LADRC and the newly developed SMC−LADRC reveal that the latter exhibits strong robustness and anti−interference capabilities in scenarios involving model uncertainty, external disturbances, and internal disturbances, confirming the effectiveness of this control method. Full article

In this paper, the velocity and altitude control problem of hypersonic vehicles is studied. Aiming at the nonlinear parameter uncertainties, external disturbances and coupling of the hypersonic vehicle system, a control method combining backstepping control with linear active disturbance rejection control is proposed. The backstepping control solves the coupling of the system and transforms the longitudinal dynamic model of the hypersonic vehicle into the form of strict feedback, which is divided into the altitude subsystem and velocity subsystem. The linear extension state observer (LESO) can observe parameter uncertainty disturbance and external disturbance. At the same time, the stability of the system is proved by Lyapunov theory. Finally, the effectiveness of the designed controller is verified by numerical simulation and comparison with classical PID control. Full article

In view of the problem of the low-speed jitter of household lawn mowers driven by a permanent magnet synchronous motor (PMSM) at low speeds and high torque, and the complicated parameters of traditional non-linear active disturbance rejection controllers, a partially optimized linear active disturbance rejection control (LADRC) driving PMSM strategy is proposed. First, the linear extended state observer (LESO), which bears a significant burden in terms of speed and load estimation in active disturbance rejection control, is optimized by reducing its order to improve the anti-disturbance performance of the active disturbance rejection controller within a limited bandwidth. Secondly, the reduced-order parallel linear extended state observer (RPLESO) is obtained by optimizing the parallel structure of the order-reduced LESO, which improves the control precision and robustness of the system. Through a simulation and experimental verification, the optimized LADRC control of the PMSM system is shown to improve the parameter adjustability, speed estimation precision and system robustness. Full article

This protocol lays the groundwork for a community-centered investigation into the intersection between climate change and violence against women and girls. Providing a standardized framework, this paper will enable researchers to collect and analyze data on severe weather patterns and their potential impact on violence within communities. The interlinkage between violence and climate is an emerging field of research. There is a need for a comprehensive understanding of the intersection of these two issues focusing on the manifestations of violence, specific vulnerabilities, and coping strategies. This protocol outlines a qualitative research approach employed in Kilifi County, Kenya. The study will include key informant interviews with community leaders and policymakers, along with focus group discussions with women, adolescent girls, and men. Community engagement is a crucial component of this work as it will ensure that the research is conducted ethically and respectfully and ensure that the findings are relevant and applicable to the community being studied. This study will contribute to a deeper understanding of the complex dynamics between violence against women and girls and climate change, informing policies, interventions, and advocacy efforts and elevating the voices of women and girls to promote gender equity in the face of climate change challenges. Full article

The paper presents the design and implementation of decentralized control for a PV–wind–battery hybrid off-grid system with limited power electronics devices and sensors. To perform well without using any maximum power point tracking (MPPT) technique from the wind turbine (WT) based on a permanent-magnet brushless DC generator (PMBLDCG) and solar panels (PVs) and balance the power in the system, a cascade control structure strategy based on a linear active disturbance rejection controller (LADRC) is developed for the two-switch DC-DC buck-boost converter. Moreover, to ensure an uninterruptible power supply to the connected loads with a constant voltage and frequency, a cascade d-q control structure based on LADRC is developed for the interfacing single-phase inverter. Furthermore, the modeling and controller parameters design are presented. The performance under all operation conditions of the hybrid off-grid configuration and its decentralized control is validated by simulation using MATLAB/Simulink and in real-time using a small-scale hardware prototype. Full article

This paper investigates an anticipatory activation anti-windup approach based on Linear Active Disturbance Rejection Control (LADRC) to address the influences of accelerated saturation on the actuators in a Miniaturized Inertial Stabilized Platform (MISP) with extreme external disturbance. The proposed method aims to eliminate the high-frequency vibrations on the Line of Sight (LOS) of electro-optical devices during actuator saturation. To achieve this, the Linear Extended State Observer (LESO) is modified by adding saturation feedback to the total disturbance observed state variable, which is operated as an anticipatory activation anti-windup compensator. The stability of the proposed controller is discussed, and the gains are optimized by the Linear Matrix Inequality (LMI) constraints though quadratic programming and an H-infinite performance indicator. Additionally, as the multiple activated scheme for anti-windup, the effectiveness of immediate activation in dealing with accelerated saturation is compared and analyzed. These comparisons and verification are implemented through simulations, where the external disturbance is introduced using recorded attitude data from USV sailing. Finally, experiments are conducted on an MISP for a visual tracking system, demonstrating that the anticipatory activation mothed effectively suppresses high-frequency vibrations on the LOS during instances of accelerated saturation. Full article

AISI 304L stainless steel is widely used in the processing equipment and food and beverage handling industries due to its corrosion resistance, hygienic properties, and cost-effectiveness. However, it is prone to pitting and crevice corrosion phenomena, the development of which can be influenced by factors such as chloride concentration, temperature, humidity, and bacterial presence. Surface treatments, including roughness levels and residual tensile stress, can significantly affect the corrosion behavior and resistance of the material. This study aims to evaluate the impact of three different surface treatments on the durability of AISI 304L steel. The correlation between surface roughness resulting from pre-treatment and pitting potential values will be examined. Additionally, the influence of different concentrations of biocide additives on surface durability will be assessed to determine the maximum effective concentration for preventing pitting phenomena. Passivation processes will also be evaluated as a potential solution for improving the pitting potential and overall durability of the components. By optimizing surface treatments and biocide concentrations, improved corrosion resistance and durability can be achieved, ensuring the long-term performance and reliability of AISI 304L steel components in critical applications such as food processing and beverage handling. Full article

Manipulators are multi-rigid-body systems composed of multiple moving joints. During movement, the Coriolis force, centrifugal force, and gravity of the system undergo significant changes. The last three degrees of freedom (DOFs) of the wrist joint of a manipulator control the end attitude. Improving the command tracking accuracy of the wrist joint is a key challenge in controlling the end attitude of manipulators. In this study, a dynamics model of the mechanical arm–wrist joint is established based on the Lagrange method. An adaptive continuous robust integral of the sign of the error (ARISE) controller is designed using the reverse step method. Additionally, a linear extended state observer (LESO) is employed to estimate the time-varying interference existing in the system and compensate for it in the designed control rate. The stability of the Lyapunov function and the boundedness of the observer are proven. The proposed control method for the wrist joint is compared with other controllers on an experimental platform of multi-DOF hydraulic manipulators. The results demonstrate that the proposed method improves the control performance of hydraulic manipulators. The application of this method offers a new strategy and idea for achieving high-performance tracking control in hydraulic manipulators. Full article

Age-disparate transactional sex relationships are often coerced and exploitative. The gender and economic disparities between affluent men and economically disadvantaged girls often perpetuate these relationships, resulting in their exploitation. This qualitative study assessed men’s understanding of factors influencing schoolgirls’ engagement in age-disparate transactional sex relationships in two rural districts in Kenya. Four focus group sessions were conducted with men from two primary professions: motorcycle taxi operators (Boda Boda) and teachers from primary and secondary schools from two districts in Kitui South, Sub County, Kenya. Focus group data were analyzed using conventional content analysis. Several influential factors associated with schoolgirls’ engagement in these transactional relationships are discussed in three broad themes: access and coercion, parental influence, and peer-related factors. Study results indicate that schoolgirls in rural areas are more susceptible to predation by men willing to trade sexual favors with underage girls. These findings make it imperative to address the predation of adolescent girls by men involved in these transactional relationships by implementing comprehensive sex education programs that empower schoolgirls to recognize and resist coercion. Additionally, implementing measures involving community leaders, parents, and other stakeholders in a collective effort to combat the exploitation of underage girls is paramount. These measures should be accompanied by the stricter enforcement of laws and regulations to hold perpetrators accountable for their actions. Full article

This paper aims to develop a novel hierarchical recursive nonsingular terminal sliding mode controller (HRNTSMC), which is designed to stabilize the inverted pendulum (IP). In contrast to existing hierarchical sliding mode controllers (HSMC), the HRNTSMC significantly reduces the chattering problem in control input and improves the convergence speed of errors. In the HRNTSMC design, the IP system is first decoupled into pendulum and cart subsystems. Subsequently, a recursive nonsingular terminal sliding mode controller (RNTSMC) surface is devised for each subsystem to enhance the error convergence rate and attenuate chattering effects. Following this design, the HRNTSMC surface is constructed by the linear combination of the RNTSMC surfaces. Ultimately, the control law of the HRNTSMC is synthesized using the Lyapunov theorem to ensure that the system states converge to zero within a finite time. By invoking disturbances estimation, a linear extended state observer (LESO) is developed for the IP system. To validate the effectiveness, simulation results, including comparison with a conventional hierarchical sliding mode control (CHSMC) and a hierarchical nonsingular terminal sliding mode control (HNTSMC) are presented. These results clearly showcase the excellent performance of this approach, which is characterized by its strong robustness, fast convergence, high tracking accuracy, and reduced chattering in control input. Full article

Severe weather events can be a catalyst for intimate partner violence, particularly in agricultural settings. This research explores the association between weather and violence in parts of East Africa that rely on subsistence farming. We used IPUMS-DHS data from Uganda in 2006, Zimbabwe in 2010, and Mozambique in 2011 for intimate partner violence frequency and EM-DAT data to identify weather events by region in the year of and year prior to IPUMS-DHS data collection. This work is grounded in a conceptual framework that illustrates the mechanisms through which violence increases. We used logistic regression to estimate the odds of reporting violence in regions with severe weather events. The odds of reporting violence were 25% greater in regions with severe weather compared to regions without in Uganda (OR = 1.25, 95% CI: 1.11–1.41), 38% greater in Zimbabwe (OR = 1.38, 95% CI: 1.13–1.70), and 91% greater in Mozambique (OR = 1.91, 95% CI: 1.64–2.23). Our results add to the growing body of evidence showing that extreme weather can increase women’s and girls’ vulnerability to violence. Moreover, this analysis demonstrates that climate justice and intimate partner violence must be addressed together. Full article

Due to some model uncertainties and unknown friction disturbances that exist in the 2-DOF lower limb exoskeleton, a linear extended state observer (LESO) is proposed to estimate the unmeasurable angular velocity of two joints and the lumped uncertainties caused by friction disturbance and hydraulic parametric uncertainties. Meanwhile, by using the Lyapunov technique, a sliding mode controller is designed to improve the dynamic performance and the steady state accuracy of two joint angle responses in human–exoskeleton cooperative motion. By regulating the sliding mode controller gain, both the system state errors and estimation errors of the LESO are reduced in an arbitrary boundary of zero neighborhood. Finally, the effectiveness of the proposed control scheme is verified with both simulation and experimental results for one operator-wearable test, to guarantee that the joint position tracking performance and human–exoskeleton impedance torques are suppressed in a satisfactory boundary. Full article

A sensorless control algorithm not only reduces the cost of a permanent magnet synchronous motor (PMSM) system, but also broadens its application scope. Expanding speed threshold and enhancing dynamic performance are crucial aspects. To optimize the adaptability of observers and the immunity of the controller in a full-speed domain, an improved sensorless control scheme for a PMSM based on a hybrid position observer and disturbance compensation is proposed. Firstly, the precise detection of the initial position and the scheme of starting with the load at any position are proposed based on high-frequency rotation injection, magnetic pole direction calibration and square-wave high-frequency injection (HFI). Secondly, a higher-order sliding mode observer (HSMO) is designed to improve high-speed observation performance by introducing an extended electromotive force (EEMF). Correspondingly, a speed controller called PI plus is developed utilizing a reverse control algorithm and the observed disturbance quantity, which further enhances the system’s disturbance rejection capability. Subsequently, a linearly weighted observer switching method and a linear signal withdrawal scheme are proposed to suppress torque and speed oscillations in medium-speed threshold. Furthermore, a normalized linear extended state observer (LESO) is designed to enhance rotor information estimation accuracy and enable the observation of unknown disturbances in full-speed thresholds. Finally, the effectiveness of the proposed sensorless control system is tested through experiments involving variations in speed, load, and parameter. The experimental results indicate that the proposed sensorless strategy is capable of achieving a loaded start. The designed observer switching strategy and the scheme of injection signal withdrawal contribute to a smoother acceleration process. Furthermore, load variation test results at high-speed thresholds demonstrate that the proposed controller can reduce speed drop by 45 rpm compared to a traditional PI. Additionally, the results of parameter variation testing validate the observer’s robustness in the disturbances of ${\psi }_f$ within the range of ±0.3 pu. Full article