Search Results (97)

This research aims to actively suppress vibrations at the end-effector of a flexible manipulator. When configured in a locked state, the system behaves as a two-link manipulator subjected to disturbances on the first link. To analyze its behavior, Finite Element Analysis (FEA) is employed to extract the natural frequencies (eigenvalues) and corresponding mode shapes (eigenvectors) of a two-link, two-joint flexible manipulator (2L2JM). The obtained eigenvectors are transformed into uncoupled state-space equations using balanced realization and the Match-DC-Gain model reduction algorithm. An H-infinity controller is then designed and applied to both the full-order and reduced-order models of the manipulator. The objective of this study is to validate an analytical framework through FEA, demonstrating its applicability to complex manipulators with multiple joints and flexible links. Given that the full state-space representation typically results in high-dimensional matrices, model reduction enables effective vibration control with a minimal number of states. The derivation of the 2L2JM state space, its model reduction, and a subsequent control strategy have not been previously addressed in this manner. Simulation results showcasing vibration suppression of a cantilever beam are presented and benchmarked against two alternative modeling approaches. Full article

Intensity–duration–frequency (IDF) curves, which relate rainfall intensity (i), storm duration (d), and return period (T), are cornerstone tools for planning, designing, and operating hydraulic works. Since Sherman’s pioneering formulation in 1931, many modern implementations have systematically omitted the duration-shifting parameter C, causing predicted intensities to diverge to infinity as $d\to 0$. This mathematical paradox becomes especially problematic under extreme hydrological regimes and convective storms exceeding 300 mm/h, where an accurate curve fit is critical. Here, we first review conventional IDF curve fitting techniques and their limitations. We then introduce IDF-GtzLo, a novel, intuitive formulation that reinstates and calibrates C directly from observed storm statistics, ensuring finite intensities for all durations. Applied to 36 automatic weather stations across Mexico, our method reduces the root mean square error by 23 % compared to the classical model. By eliminating the infinite intensity paradox and improving statistical performance, IDF-GtzLo offers a more reliable foundation for hydrological risk assessment and the design of infrastructure resilient to climate-driven extremes. Full article

To meet the in-orbit performance verification requirements of a drag-free control system for gravitational wave detection satellites, this study develops a ground simulation platform using the H-infinity ($H_{\infty }$) control method in Simulink. The FPGA implementation accelerates the core algorithm of drag-free control. A frequency-domain linear robust control design is employed, with a frequency pre-warped bilinear transformation method used to discretize the multi-degree-of-freedom controller. The established control system model includes 18 degrees of freedom, with 12 from the dual test masses (TM) and 6 from the satellite body. The two test masses are spatially arranged in a symmetric configuration, and their control structure also exhibits symmetry. A rapid reconfigurable hardware architecture is utilized, and the Vitis Model Composer tool is employed to efficiently translate the Simulink algorithm model into hardware description language, reducing the processing delay of the core control algorithm to the nanosecond level. Through a 15-channel gradient test comparison, the FPGA platform maintains numerical equivalence with the Simulink platform (maximum error of ${10}^{-13}$). Experimental results show that the hardware acceleration improves dynamic response speed by an order of magnitude, achieving position control accuracy of ±5 μm and attitude accuracy of ±10 μrad, with overall processing latency at the microsecond level. This method provides a reliable engineering validation approach for ultra-precision control systems in gravitational wave detection. Full article

This paper proposes a novel Guidance and Control architecture for close-range rendezvous and final approach of a chaser spacecraft towards a non-cooperative and tumbling space target. In both phases, reference trajectory generation relies on a Sequential Convex Programming algorithm which iteratively solves a non-linear optimization problem accounting for propellant consumption, relative dynamics, collision avoidance and navigation sensor pointing constraints. At close range, trajectory tracking is entrusted to a translational H-infinity controller, coupled with a quaternion-feed-back regulator for target pointing. In the final approach phase, an attitude-pointing strategy is adopted, requiring a six degree-of-freedom H-infinity controller to follow a reference roto-translational trajectory generated to ensure target-chaser motion synchronization. Performance is evaluated in a high-fidelity simulation environment that includes environmental perturbations, navigation errors, and actuator (i.e., cold gas thrusters and reaction wheels) modelling. In particular, the latter aspects are also addressed by integrating the proposed solution within a complete Guidance, Navigation and Control pipeline including a state-of-the-art LIDAR-based relative navigation filter and a dispatching function for the distribution of commanded control actions to the actuation system. A statistical analysis on 1000 simulations shows the robustness of the proposed approach, achieving centimeter-level position accuracy and sub-degree attitude accuracy near the docking/berthing point. Full article

This study aimed to examine the pharmacokinetic changes in tolfenamic acid administered intravenously and orally to ducks at different doses (2, 4, and 8 mg/kg). Furthermore, the binding ratio to plasma proteins was assessed utilizing the ultrafiltration method. Eighteen male Pekin ducks were randomly assigned to three dosage groups (2, 4, and 8 mg/kg), with each group undergoing a trial in two phases: intravenous (IV) and oral administration. The sample was analyzed using an approved HPLC-UV method. A non-compartmental analysis was utilized to evaluate the pharmacokinetic data. For 2 mg/kg IV injection, the area under the curve from zero to infinity (AUC_0-∞), total clearance (Cl_T), volume of distribution at steady state (V_dss), and elimination half-life (t_1/2ʎz) were 13.03 h*µg/mL, 0.15 L/h/kg, 0.30 L/kg, and 1.72 h, respectively. Following oral administration at a dose of 2 mg/kg, the AUC_0-∞, peak plasma concentration (C_max), and bioavailability were 6.32 h*µg/mL, 2.25 µg/mL, and 48.52%, respectively. The t_1/2ʎz was extended, C_max and AUC_0-∞ elevated, T_max shortened, and Cl_T decreased in a dose-dependent manner. No dose-related change was observed in V_dss and bioavailability. In ducks, tolfenamic acid’s plasma protein binding was 99.74%, unaffected by concentration. These results may contribute to the application of tolfenamic acid in ducks at different doses, but dose-related changes in therapeutic efficacy should also be demonstrated. Full article

This study presents an image inpainting model based on an energy functional that incorporates the $L^p$ norm of the fractional Laplacian operator as a regularization term and the $H^{-1}$ norm as a fidelity term. Using the properties of the fractional Laplacian operator, the $L^p$ norm is employed with an adjustable parameter p to enhance the operator’s ability to restore fine details in various types of images. The replacement of the conventional $L^2$ norm with the $H^{-1}$ norm enables better preservation of global structures in denoising and restoration tasks. This paper introduces a diffusion partial differential equation by adding an intermediate term and provides a theoretical proof of the existence and uniqueness of its solution in Sobolev spaces. Furthermore, it demonstrates that the solution converges to the minimizer of the energy functional as time approaches infinity. Numerical experiments that compare the proposed method with traditional and deep learning models validate its effectiveness in image inpainting tasks. Full article

Accurate dynamic estimation is of vital importance for the real-time monitoring of the operating status of power systems. To address issues such as non-Gaussian noise and outlier interference, a cubature Kalman filter state estimation method based on robust functions (RF-CKF) is proposed. Firstly, based on the exponential absolute value, an estimator is established, which is represented by the exponential absolute value and quadratic functions. Secondly, the regression form of batch processing mode is established, and the estimator based on the exponential absolute value is integrated into the cubature Kalman filter framework. Finally, an example of a standard IEEE 39-bus system is used to verify the effectiveness of the proposed method. Compared with the unscented Kalman filter, cubature Kalman filter and H-infinity CKF, the proposed method has better estimation accuracy and stronger robustness in an anomaly environment. Full article

The integrated design problem of non-fragile controllers and extended state observers (ESOs) for nonlinear unmanned surface vehicles (USVs) under mismatched disturbances is addressed in this paper. First, an integrated model combining the USV system and the rudder system is developed, which includes a second-order underdamped system and a Norrbin nonlinear model incorporating uncertainties. Due to the coupling issues in the design of controllers and observers caused by parameter perturbations or other unmodeled dynamics, an integrated design method, which enables the simultaneous computation of controller gains, observer gains, and disturbance compensation gains, is proposed, effectively addressing these issues. Ultimately, the performance of the designed strategy is verified through a simulation, with the data used in the simulation derived from the real Qingshan USV. Full article

Hydrostatic transmissions are essential in applications demanding variable torque and speed, such as mining and agricultural machinery, due to their compact design, high power-to-weight ratio, and efficient variable speed control. Despite these advantages, their inherent nonlinearities and susceptibility to parametric uncertainties pose significant challenges for precise motion control. This study presents a comparative analysis of classical PID and robust H-infinity controllers for regulating the speed of hydraulic motors under varying torsional loads. A linearized uncertain system model is developed using upper Linear Fractional Transformations (LFTs) to capture key parametric uncertainties. A simplified H-infinity controller is designed to robustly manage system dynamics, particularly addressing phase lags induced by uncertain loads. Simulation results demonstrate that the H-infinity controller offers superior performance over the PID controller in terms of stability, disturbance rejection, and robustness to load fluctuations. This work contributes a practically viable robust control solution for improving the reliability and precision of electro-hydraulic systems, particularly in demanding, real-world environments. Full article

Battery longevity and hydrogen consumption efficiency are primary optimization goals for EMS in high-performance fuel cell hybrid electric vehicles (FCHEVs). This article provides an overview of an FCHEV powertrain and a hierarchical control scheme that includes low-level controllers for key components. Finally, a higher-level control architecture for power management combines a fuzzy logic controller with an H-infinity controller to ensure reliable power management. The aim is to enhance EMS performance and overall robustness to uncertainties by implementing the higher-level control architecture. The effectiveness of the proposed strategy is demonstrated through simulations in the MATLAB/SIMULINK 2024a environment. Full article

Accurate and reliable estimation of the state of charge (SOC) of lithium-ion batteries is essential for the performance and safety of battery management systems (BMS) in applications such as electric vehicles and energy storage systems. However, there is a lack of comprehensive comparative studies evaluating different SOC estimation methods under standardized conditions. In this paper, we address this gap by providing a comprehensive, objective comparison of various Kalman and H-Infinity filter variants for battery SOC estimation, utilizing a detailed validation method based on well-defined criteria. The main contributions of this work are: (1) Implementation of multiple filter variants using a consistent equivalent circuit battery model; (2) Development of a standardized validation method for objective performance evaluation; (3) Detailed mathematical formulations enhancing reproducibility; (4) Evaluation of computational efficiency on a digital signal processor (DSP) to provide practical insights for real-time applications. Our findings reveal that while neither filter type is universally superior, the Extended Kalman Filter (EKF) and H-Infinity Filter (HIF) offer a solid balance between estimation accuracy and computational load, making them reliable choices for general applications. This work advances the understanding of SOC estimation methods and aids practitioners in balancing accuracy and computational efficiency for real-world applications. Full article

Background/Objectives: Disability is a term that involves mental, intellectual, or sensory impairment resulting in the loss of one’s ability to walk or perform the activities necessary to live in a society. This study aims to collect all the data regarding the absorption, distribution, and disposition of drugs in disabled Saudi patients, i.e., patients suffering from epilepsy, cancer, cardiovascular diseases, etc., and then compare these results with data reported in other ethnicities. Methods: An exhaustive online search used the key terms in Google Scholar, PubMed, Cochrane Library, and Science Direct to extract all articles that met the eligibility criteria. All research studies containing pharmacokinetic (PK) parameters (area under the curve from 0 to infinity (AUC_0–∞), maximal plasma concentration (C_max), clearance (CL), volume of distribution, time to reach maximum plasma concentration, and half-life) were included in this review. Results: In pediatric epileptic patients, carbamazepine showed a notable decrease in C_max with increasing age, which may be due to ontogenetic changes in its disposition. The AUC_0–∞ of busulphan in adult hematopoietic stem cell transplantation patients was recorded as 4392.5 ± 1354.65 μg·h/mL, with high inter-individual variability. Moreover, the CL of vancomycin was reported to be 25% higher among cancer patients in comparison to non-cancer subjects. Conclusions: The complications in disabled patients due to alterations in cytochrome P450 enzymes, pathophysiology, genetics, and ethnicity emphasize the significance of patient-centered drug dosing. These findings may aid healthcare physicians in refining therapeutic care in this population. Full article

Phthalic acid esters (PAEs) are mainly used as plasticizers and result in serious environmental contamination worldwide. Microbial biodegradation becomes an efficient strategy for PAE elimination. In the current study, the PAE-degrading strain Gordonia sp. LUNF6 was isolated from contaminated soil. Strain LUNF6 can efficiently degrade DBP in a wide range of temperatures, pH values, and salinity levels. This strain is also capable of degrading 11 types of PAEs and displays remediation potential in wastewater. The complete genome of strain LUNF6 was sequenced to determine its efficient degradation performance. Its genome comprises a chromosome (3,971,257 bp) and a plasmid (78,813 bp). After gene function annotation, the complete PAE degradation pathway was proposed. The gene of monoalkyl PAE hydrolase MphGd2 was cloned and heterologously expressed. The protein of MphGd2 was purified by infinity chromatography, and we hydrolyzed MBP to produce PA. These results reveal the molecular mechanism of PAE degradation by strain LUNF6, which will contribute to the application of strain LUNF6 and hydrolase MphGd2 in bioremediation. Full article

In 1998, we gave a complete scattering analysis of the cubic Heun operator ${\displaystyle H=a^{\ast }(a+a^{\ast })a}$ acting on Bargmann space, where a and $a^{\ast }$ are the standard Bose annihilation and creation operators satisfying the commutation relation $[a,a^{\ast }]=I$. We used the boundary conditions at infinity to give a description of all maximal dissipative extensions in Bargmann space of the minimal Heun’s operator H. The characteristic functions of the dissipative extensions were computed, and some completeness theorems were obtained for the system of generalized eigenvectors of this operator. In this paper, we study the deficiency numbers of the generalized Heun’s operator ${\displaystyle H^{p,m}=a^{{\ast }^p}(a^m+a^{{\ast }^m})a^p;(p,m=1,2,\dots )}$ acting on Bargmann space. In particular, here we find some conditions on the parameters p and m such that ${\displaystyle H^{p,m}}$ is completely indeterminate. It follows from these conditions that ${\displaystyle H^{p,m}}$ is entirely of minimal type. Then, we show that ${\displaystyle H^{p,m}}$ and ${\displaystyle H^{p,m}+H^{{\ast }^{p,m}}}$ (where $H^{{\ast }^{p,m}}$ is the adjoint of $H^{p,m}$) are connected to the chaotic operators. Full article

Under the European Space Agency (ESA) support, INCAS has taken the initiative to develop an Ascent and Descent Autonomous Maneuverable Platform (ADAMP) which will serve as an in-flight testing platform for reusable space technologies. This paper is focusing on activities aimed at assessing the robustness of the control system of the ADAMP in the presence of aerodynamic disturbances, with an emphasis on stability and disturbance rejection. Considering the ADAMP’s inherent aerodynamic instability, the way aerodynamic forces and moments are incorporated in the control design formulation plays a critical role in the effectiveness of the adopted control solution in the presence of wind gusts and potential interaction with sloshing modes. To showcase these phenomena, two alternative control design methodologies are employed in the paper: the baseline strategy relies on robust self-scheduled structured H-Infinity optimization, while the second approach is based on nonlinear sliding mode theory. Different structured H-Infinity controllers are designed and analyzed in the frequency domain, providing a clear understanding of the impact of the aerodynamic effects in terms of stability margin degradation. These controllers are then thoroughly compared with the sliding mode alternative via nonlinear worst-case simulation of typical ascent and descent flights in the presence of strong wind gusts. Full article