Stabilization Platform Research Articles

The Effect of Eight Weeks of Relaxation Massage on the Mental Fatigue Control, Balance, Lower Extremity Function and Landing Mechanic in Physical Education Students

Background and Aims: Mental fatigue usually occurs following prolonged cognitive activity. Mental fatigue is a psychological condition that occurs as a result of long-term cognitive activities. Mental fatigue can have significant effects on the daily life of healthy people. This study aimed to investigate the effect of eight weeks of relaxation massage on the mental fatigue control and balance, lower extremity function, and landing mechanic in physical education students. Methods: This research is a quasi-experimental study, and the statistical population of this study was physical education students. From the statistical population, 30 male students with Mean±SD age= 19.5±5.5 years, weight= 69.6±6.8 kg, height= 187.75±4.5 cm, and sports history= 2.66±1.3 years. They were selected by purposeful and were randomly divided based on Research and Criteria into two groups: control group (n=15) and relaxation massage group (n=15). Before and after relaxation massage, mental exhaustion with 45 minutes of stroke activity (Stroop test), Dynamic Balance with Y test, Semi-dynamic balance with Lafayette Stability Platform, lower extremity function by the Lower Extremity Functional Test (LEFT) test and landing mechanic by LESS, Jump-landing skill film assessment by Auto CAD and Kinovea software were measured. Data analysis was performed in SPSS v. 22 software by using Statistical method of ANOVA test with repeated measures and paired t-test at the significant level P=0.05. Results: The results showed that a significant difference was observed between the relaxation massage group and the control group on lower limb function, landing mechanics, dynamic balance, and semi-dynamic balance of physical education students (P=0.001). Conclusion: Significant changes in lower limb function factors, landing mechanics, dynamic balance, and semi-dynamic balance in physical education students after relaxation massage exercises indicate the importance of this issue. Injury prevention specialists should study and research in introducing strategies to deal with the occurrence of mental fatigue.

Railway crane platform stabilization system

When operating a railway crane in curved sections of the track, derailment of wheelsets of the crane bogies from the rail track when it is displaced during hanging on the outriggers, wheelset of the bogie missing the rail track after the work has been completed or the crane has been down from the outriggers, which significantly affects performance of loading and unloading operations. One of the reasons for the occurrence of such dangerous situations is the not strictly horizontal position of the non-rotating platform of the railway crane.Railway cranes are part of recovery trains designed to eliminate the consequences of rolling stock derailments. A priority for recovery trains is to reduce the time it takes to eliminate the consequences of traffic accidents, which can be achieved through the use of new or improved devices or methods.The article describes a system of automatic stabilization (leveling) of the platform of a railway crane (for example, EDK 500/1 crane type) when it moves in curved sections of the track (the motion of a railway crane at relatively low speeds (up to 50 km/h) is considered).In order to study the modernized technical system (a crane equipped with an automatic platform stabilization system), its mathematical simulation is carried out. At the initial stage, a solidstate digital model of a railway crane in combination with a section of a railway track is created in the SolidWorks computer-aided design system; developed solid model is translated into the Sim- Mechanics MATLAB environment. Further, in order to improve the adequacy of modeling, the developed dynamic model is being finalized by integrating MATLAB program libraries (SimMechanics, SimHydraulics, Fuzzy Logic Toolbox, etc.) to take into account the interaction of elements of different physical nature. Results of modeling modernized technical system are presented, which confirm the advisability of using the stabilization system on railway cranes when passing curved track sections.

Disturbance rejection control of airborne radar stabilized platform based on active disturbance rejection control inverse estimation algorithm

PurposeThis paper aims to study a disturbance rejection controller to improve the anti-interference capability and the position tracking performance of airborne radar stabilized platform that ensures the stability and clarity of synthetic aperture radar imaging.Design/methodology/approachThis study proposes a disturbance rejection control scheme for an airborne radar stabilized platform based on the active disturbance rejection control (ADRC) inverse estimation algorithm. Exploiting the extended state observer (ESO) characteristic, an inversely ESO is developed to inverse estimate the unmodeled state and extended state of the platform system known as total disturbances, which greatly improves the estimation performance of the disturbance. Then, based on the inverse ESO result, feedback the difference between the output of the tracking differentiator and the inverse ESO result to the nonlinear state error feedback controller (NLSEF) to eliminate the effects of total disturbance and ensure the stability of the airborne radar stabilized platform.FindingsSimulation experiments are adopted to compare the performance of the ADRC inverse estimation algorithm with that of the proportional integral derivative controller which is one of the mostly applied control schemes in platform systems. In addition, classical ADRC is compared as well. The results have shown that the ADRC inverse estimation algorithm has a better disturbance rejection performance when disturbance acts in airborne radar stabilized platform, especially disturbed by continuous airflow under some harsh air conditions.Originality/valueThe originality of this paper is exploiting the ESO characteristic to develop an inverse ESO, which greatly improves the estimation performance of the disturbance. And the ADRC inverse estimation algorithm is applied to ameliorate the anti-interference ability of the airborne radar stabilization platform, especially the ability to suppress continuous interference under complex air conditions.

The Stability of a Two-Axis Gimbal System for the Camera.

Gimbal or an inertial stabilization platform (ISP) is used to stabilize the line of sight of an object or device that is tracking another object (LOS) with stationary or moving targets or targets moving forward. It can achieve precision when there is isolation between the tracker and the gimbal base. Studying the 2-axis tilt angle to create gimbal stability, especially in a camera, is a compelling subject for the automation field, as it is controlled by modern controllers. This paper presents a two-axis gimbal loop in which the LOS rate is stable, and I proceed to examine the stability of the system to get a better overview of the system properties. Through examining the stability of the system, I can choose from modern control methods to control them. The stability of the system used from the two analysis methods I present below gives me a visual view from the results achieved. The simulation is performed in MATLAB.

Boosting the rate capability and working lifespan of K/Co co-doped Na3V2(PO4)3/C for sodium ion batteries

Na3V2(PO4)3 (NVP) has been deemed to be a prospective cathode for sodium ion batteries (SIBs) duo to its high structural stability and flat voltage platform. Herein, a series of K/Co co-doped NVP composites with optimized sodium storage property are produced via a feasible sol-gel method. Significantly, the introduced K+ has substituted of Na+ at Na1 site, strictly demonstrated by the Rietveld refinement results. Meanwhile, this substitution has hardly influence on the reversible de/insertion of Na+ situated at Na2 site. Moreover, the beneficial K+ with larger ionic radius can act as the pillar ion to improve the structural stability efficiently. Furthermore, the replacement of V3+ by Co2+ facilitates to enlarging the interplanar spacing in crystal structure, resulting in accelerating the Na+ migration effectively. Moreover, substitution with low valence element (Co2+vs. V3+) can generate the favorable holes to increase the intrinsic electronic conductivity. Notably, doping with appropriate content of K/Co elements favors to reduce the particle size and shorten the pathway for Na+ transformation, distinctly boosting the apparent ionic diffusivity. Specifically, K/Co co-doping induces to forming the unique mesoporous morphology, immensely enlarging the specific surface area of active grains and therefore facilitating the infiltration between the particles and electrolyte. Comprehensively, the optimized K0.1Co0.05-NVP/C exhibits an outstanding electrochemical performance. It shows a high initial capacity of 122.7 mA h g−1 at 0.1 C, which is higher than the theoretical value of NVP (117.6 mA h g−1). It can release an initial capacity of 100.9 mA h g−1 at 1 C and maintain 71.0 mA h g−1 after 500 cycles. Moreover, the reversible capacity can be achieved as 98.8 mA h g−1 at a high rate of 10 C and a favorable retention of 75.9% can be obtained after 400 cycles. Besides, the kinetic characteristics for the modified K0.1Co0.05-NVP/C cathode are superior than those of pristine NVP/C. Specifically, it reveals a relatively high diffusion coefficient of Na+ (0.53 × 10−10 cm2 s−1). Thus, the modified K/Co co-doped NVP/C sample can be a promising cathode material for SIBs.

Synthesis and fabrication of 2D Tungsten trioxide nanosheets based platform for impedimetric sensing of cardiac biomarker

Herein, we report the development of a two-dimensional (2D) label-free matrix for cardiac biomarker detection. Tungsten trioxide nanosheets (WO3 NS) were synthesized by a facile, environmentally friendly hydrothermal method and subsequently functionalized chemically using 3-aminopropyletriethoxysilane (APTES). Thin film of APTES functionalized WO3 NS was deposited on indium tin oxide (ITO) substrate using electrophoretic deposition technique. The fabricated APTES/WO3 NS/ITO electrode endows with large surface area for high loading of cardiac troponin I antibodies (anti-cTnI), good stability and strong adsorption platform for the biomolecules immobilization. The selective and quantitative detection of cTnI biomarker was accomplished by immobilizing anti-cTnI on APTES/WO3 NS/ITO platform. The electrochemical sensing using anti-cTnI/APTES/WO3 NS/ITO immunoelectrode was studied as a label-free immunoassay format using EIS (electrochemical impedance spectroscopy) technique. The performance of the sensor as investigated with the measurement of charge transfer resistance (RCT) for variant concentrations of cTnI antigen demonstrated good sensitivity as 30.8 Ω mL ng−1 cm−2 for a linear detection range 0.1 to 100 ng mL−1 along with good stability up to 6 weeks. The competency of the biosensor was also tested by detecting cTnI antigen in spiked human serum samples.

An Active Disturbance Rejection Control Design Method Based on Disturbance Separation

In order to further improve the stability accuracy and anti-disturbance ability of the photoelectric stabilization platform, this paper proposes disturbance separation active disturbance rejection (DSADRC) method. Disturbance separation active disturbance rejection control makes full use of the available system model information and uses disturbance separation to separate the known disturbances from the total disturbance to be estimated, and improve the estimation accuracy of expanded state observer (ESO) by reducing the load. At the same time, it gets rid of the constraints of the standard integral series type in the traditional active disturbance rejection control, and takes the actual theoretical model of the system as the compensated model of the system, thus realizing the reuse of the system controller and reducing the workload of control algorithm design. And through simulation experiments, the DSADRC method is compared with the commonly used expected frequency characteristic method (EF), linear active disturbance rejection control (LADRC), model-assisted linear active disturbance rejection (MLADRC), and the experimental results show that: The DSADRC has better dynamic response performance and disturbance suppression ability.

Large‐Scale‐Compatible Stabilization of a 2D Semiconductor Platform toward Discrete Components

AbstractAtomically thin 2D materials have drawn considerable attention in the past years with potential ranging from transistors to optoelectronics. As such, they are now foreseen as strong candidates for epitaxy‐free technologies and the tetrad of size‐weight‐power‐and‐cost (SWAP‐C) reduction. Targeting radiofrequency (RF) applications, the 2D semiconducting transition metal dichalcogenides (TMDC) family can offer the opportunity of wide tunability of their electronic properties, providing a large variety of band gaps. However, evaluation and integration of those materials into discrete components requires a stabilization of their properties. This work focuses on the evaluation of a large‐scale compatible fabrication/passivation process on large area (>1000 µm2) monolayers of the prototypical 2D semiconductor MoS2. The process is developed including pre‐ and post‐patterning protection/passivation layers. It is shown to reduce the initial natural p‐doping of the sample, leading to lower transistor threshold voltages, a 106 ION/IOFF ratio, and an effective averaged field‐effect mobility under ambient conditions of 20 cm2 V−1 s−1 (up to 35 cm2 V−1 s−1 for some devices), which represents an increase by a 40‐fold factor compared to a conventional process carried on the large scale platform. This work represents an important step toward the integration of 2D TMDCs in discrete RF circuits and components.

Improving seeking precision by utilizing ghost imaging in a semi-active quadrant detection seeker

Conventional semi-active laser guidance takes advantage of the laser designator to illuminate the stable and uniform laser spot on target precisely. The seeker collects the reflected light by a quadrant detector and outputs the relative position information to guide the missile to the illuminating laser spot. However, the designation and guidance accuracy could be jeopardized by the randomly drifting of laser spot caused by the instability of designation platform and air turbulence. In this work, ghost imaging technique is adapted to a quadrant detector semi-active seeker by utilizing structured illumination on the target. With a series of structured illumination masks, the signals from the quadrant detector are multiplexed to perform calculation of the target relative position as well as image reconstruction of the illuminated area simultaneously. Automatic target recognition methods could be further applied to the reconstructed image to calculate the designating error and correct the guidance. The results of simulation and experiment demonstrate that the proposed method could improve the guidance accuracy in many circumstances which would lead to attacking deviation if conventional semi-active laser guidance is used.

The airborne inertially stabilized platform suspend by an axial-radial integrated active magnetic actuator system

IntroductionThe inertial stabilization platform (ISP) is widely used in the earth observation system to stably track the line of sight of the payload because it could isolate vibrations and angular motions of the aviation platform. Objectivesan active magnetic actuator (AMA) system integrating the axial and the radial control is used to levitate the azimuth gimbal to improve attitude stabilization precision and dynamic performance of the ISP, and then the dynamic model of azimuth gimbal is developed. MethodsThe magnetic force and the gimbal torque of the axial-radial integrated AMA system are investigated, and the attitude information of the suspended azimuth gimbal is measured. ResultsThe attitude stabilization precision of azimuth gimbal is confined at 0.02°, and the control bandwidth of the axial-radial integrated AMA system could exceed 100 Hz. Conclusionthe ISP with an axial-radial integrated AMA system has better attitude stabilization precision and wider control frequency than the pure mechanical ISP, so it is potential to be applied in the airborne remote sensing system to improve the measurement precision.

Research of Intelligent Temperature Measuring Robot System

With the outbreak of novel coronavirus pneumonia worldwide, a kind of epidemic prevention robot is urgently needed in society. The intelligent temperature measurement robot system mainly includes the robot’s high stability multi-attitude omnidirectional movement module, robot path planning and autonomous navigation module, robot environment information acquisition and recognition module, robot remote control module, and robot system integration. According to the design principle of the wheeled robot, high stability and multi attitude omni-directional mobile platform of temperature measuring robot are constructed; path planning and autonomous navigation of robot are realized based on sensor data fusion; temperature detection and remote care function are realized by thermal imaging sensor system by capturing the thermal radiation emitted by the human body, and based on open modular control system architecture. Based on the existing research foundation, the intelligent temperature measurement robot system is established by integrating the robot multi attitude omni-directional mobile system, robot path planning, and autonomous navigation system, robot environment information acquisition and recognition system, and robot remote control system.

ВАРІАНТ СТРУКТУРИ СИСТЕМИ АВТОМАТИЧНОЇ СТАБІЛІЗАЦІЇ ПЛАТФОРМИ АНТЕННОГО ПОЛЯ РУХОМОГО ОБ’ЄКТУ

The article proposes a variant of constructing a digital system for automatic stabilization of the antenna field platform located on an object (vehicle), and also considers the structural diagrams of control channels. The choice of executive devices to ensure the performance and accuracy of the system is substantiated. The conditions of use, restrictions and initial data necessary for the synthesis of the automatic stabilization system are determined, the principles of calculating by the system - the coordinates of the position of the antenna field platform in space - are highlighted.The prerequisites for the use of a platform with stabilization at the facility is the need to ensure the most efficient use of communication facilities (antenna systems) in a complex electromagnetic environment and to reduce the deployment (folding) time, adjust radio and satellite communications in the operational-tactical and tactical control levels.The system of automatic stabilization of the antenna field platform will provide optimal conditions for the interaction of antenna systems that are part of the antenna field of radio-electronic means of the compact constellation. Optimal conditions should be understood as vertical placement of omnidirectional antennas, the possibility of changing the position of directional antennas in the azimuthal plane and ensuring the electromagnetic compatibility of radio electronic means. The deviation of the platform from the required angular positions of the reference coordinate system can be determined by accelerometers or other devices that measure the linear acceleration of an object in a given plane.It is proposed to stabilize the platform through two channels for each of the axes. The angular position of the stabilized platform in space is specified in the reference coordinate system, which is not associated with a moving object (vehicle) that is moving, and in a moving coordinate system, it is rigidly connected with this object. It is proposed to use an inertial coordinate system as a reference coordinate system, that is, motionless relative to the horizon, which is oriented at a given point on the earth's surface. The proposed automatic system is universal, with the ability to adapt to the driving performance of a moving object. Adaptability is ensured by the presence in the control loop of an automatic stabilization system of circuits, the parameters of the transfer functions of which are pre-calculated for the tactical and technical characteristics of the moving object.

Active Vibration Isolation of a Maglev Inertially Stabilized Platform Based on an Improved Linear Extended State Observer

An inertially stabilized platform is subject to the vibration force and moment from its support base, and low-frequency vibrations cannot be eliminated by mechanical vibration isolation. Combining gimbals with magnetic bearings instead of mechanical bearings, a maglev inertially stabilized platform (MISP) is characterized by no friction or an active vibration control capability. In this paper, an improved linear extended state observer (LESO) replacing displacement error with next-order error is proposed to estimate the low-frequency vibration and improve the estimation accuracy. An active vibration isolation control method is then designed to realize cancellation compensation on the MISP. Finally, a simulation example is presented to validate that the proposed measures can effectively eliminate the low-frequency vibration force transmitted from the base and ensure the stability of the MISP.

Well-Defined Lignin Model Films from Colloidal Lignin Particles.

The transformation of a molecularly complex and irregularly shaped lignin into a nanoscale spherical architecture is anticipated to play a pivotal role in the promotion of lignin valorization. From the standpoint of using colloidal lignin particles (CLPs) as building blocks for a diverse range of applications, it has become essential to study their interactions with soluble compounds of varied origin. However, the lack of model films with well-defined surface properties similar to those of CLPs has hindered fundamental studies using surface-sensitive techniques. Here, we report well-defined and stable thin films prepared from CLPs and demonstrate their suitability for investigation of surface phenomena. Direct adsorption on substrates coated with a cationic anchoring polymer resulted in uniform distribution of CLPs as shown with atomic force microscopy (AFM). Quartz crystal microbalance with dissipation monitoring (QCM-D) experiments revealed higher adsorbed mass of cationic lignin onto the CLP-coated substrate in comparison to the film prepared from dissolved lignin, suggesting preferential adsorption via the carboxylic acid enriched surfaces of CLPs. QCM-D further enabled detection of small changes such as particle swelling or partial dissolution not detectable via bulk methods such as light scattering. The CLP thin films remained stable until pH 8 and displayed only a low degree of swelling. Increasing the pH to 10 led to some instability, but their spherical geometry remained intact until complete dissolution was observed at pH 12. Particles prepared from aqueous acetone or aqueous tetrahydrofuran solution followed similar trends regarding adsorption, pH stability, and wetting, although the particle size affected the magnitude of adsorption. Overall, our results present a practical way to prepare well-defined CLP thin films that will be useful not only for fundamental studies but also as a platform for testing stability and interactions of lignin nanoparticles with materials of technical and biomedical relevance.

Fabrication of strongly near-infrared absorbing vesicles by stabilizing chromogenic radicals in biomimetic membranes

An efficient approach for fabrication of novel near-infrared (NIR) absorbing materials has been developed based on stabilization of chromogenic radicals in lipid membranes. Compared with the closed-shell molecules, radicals or radical ions of organic chromophores usually display remarkably red-shifted absorption. However, stabilization and functionalization of these radicals is still a challenging task. Herein, biomimetic membranes were employed as a platform for stabilization and convenient functionalization of chromogenic radicals. NIR optical vesicles can be facilely formed by co-assembly of radical-dominated supramolecular chromophores with surfactants in aqueous solution. The as-formed dye-interbedded vesicles with biomimetic membrane surfaces displays strong NIR absorption and electron spin resonance signals, sensitive photoacoustic response upon NIR excitation, and minimal nonspecific interaction with biological macro-molecules. Furthermore, doping of the chromogenic interlayers to optimize the optical properties and modification of the membrane surfaces for functionalization towards bioanalytical applications can be carried out under ambient conditions.

Design and Analysis of a Variable Inertia Spatial Robotic Tail for Dynamic Stabilization.

This paper presents the design of a four degree-of-freedom (DoF) spatial tail and demonstrates the dynamic stabilization of a bipedal robotic platform through a hardware-in-loop simulation. The proposed tail design features three active revolute joints with an active prismatic joint, the latter of which provides a variable moment of inertia. Real-time experimental results validate the derived mathematical model when compared to simulated reactive moment results, both obtained while executing a pre-determined trajectory. A 4-DoF tail prototype was constructed and the tail dynamics, in terms of reactive force and moments, were validated using a 6-axis load cell. The paper also presents a case study where a zero moment point (ZMP) placement-based trajectory planner, along with a model-based controller, was developed in order for the tail to stabilize a simulated unstable biped robot. The case study also demonstrates the capability of the motion planner and controller in reducing the system’s kinetic energy during periods of instability by maintaining ZMP within the support polygon of the host biped robot. Both experimental and simulation results show an improvement in the tail-generated reactive moments for robot stabilization through the inclusion of prismatic motion while executing complex trajectories.

High Performance Both in Low-Speed Tracking and Large-Angle Swing Scanning Based on Adaptive Nonsingular Fast Terminal Sliding Mode Control for a Three-Axis Universal Inertially Stabilized Platform.

In order to improve the performance in the practical engineering applications including so called low-speed video tracking and large-angle swing scanning imaging at the same time for a three-axis universal inertially stabilized platform (UISP), we propose an adaptive nonsingular fast terminal sliding mode control (ANFTSMC) strategy subjected to the uncertain disturbances and input saturation constraints. First of all, a second-order dynamic model is established with uncertain disturbances and input saturation constraints. Secondly, a nonsingular fast terminal sliding mode controller (NTSMC) is constructed to ensure the system error converges to zero fast in a finite time; meanwhile, a novel reaching law based on a modified normal distribution function is designed to adjust the control gain. Thirdly, an adaptive control law is designed to online estimate the parameters of the lumped uncertain disturbances. Additionally, the stability of the control system is proved by Lyapunov theory. Finally, extensive comparative simulations and experiments are carried out, the results comprehensively show the effectiveness and superiority of the proposed control method, which can accelerate convergence, weaken the chattering, and has the better control accuracy and robust performance both in the low-speed tracking and large-angle swing scanning applications. Moreover, the exact dynamic model and the prior knowledge of the upper bounds of the disturbances are not required during the procedure of the controller design, which make it have more extensive application value in practical engineering.

Adaptive Kalman Filter Enhanced With Spectrum Analysis for Wide-Bandwidth Angular Velocity Estimation Fusion

The optoelectronic inertial stabilization platform is widely used in the fields of astronomical observation, monitoring and search, quantum communication and other fields, which all need strong vibration suppression and tracking capability. To realize high-precision angular measurement throughout the wide bandwidth for inertial stabilization platform, the fusion algorithm is studied to fuse the signals of magnetohydrodynamic (MHD) and microelectromechanical (MEMS) gyroscope. The basic adaptive Kalman filter experiences signal-to-noise ratio and fusion-frequency jitter problems because of the measurement transfer matrix deviation, making it unsuitable for quick dynamic systems. This paper proposes an adaptive Kalman filter enhanced with spectrum analysis by connecting the measurement covariance with the signal frequencies. This method divides the trace of the modified measurement covariance into three parts according to frequency domain characteristics. Based on the frequency analysis, the filter output mainly depended on the MEMS gyroscope at low frequencies, fusion results of the two gyroscopes in the intermediate frequency-domain, and the MHD gyroscope at high frequencies. This theory is verified in the swept frequency experiment and comparative experiments, including multi-harmonic sinusoidal and step response tests compared with combing filter and closed-loop filter. The tests results show that the fusion signal is identical with the actual signal throughout the measurement bandwidth, and the fusion signal-to-noise ratio is improved. The frequency characteristics and noise level of the fusion algorithm satisfy the requirements of optoelectronic inertial stabilization vibration measurement.

Lack of cerebellar tDCS effects on learning of a complex whole body dynamic balance task in middle-aged (50\u201365\u2009years) adults

BackgroundCerebellar transcranial direct current stimulation (tDCS) is widely considered as a promising non-invasive tool to foster motor performance and learning in health and disease. The results of previous studies, however, are inconsistent. Our group failed to provide evidence for an effect of cerebellar tDCS on learning of a complex whole body dynamic balance task in young and healthy participants. Ceiling effects in the young study population are one possible explanation for the negative findings.MethodsIn the present study, we therefore tested 40 middle-aged healthy participants between the ages of 50 to 65 years. Participants received either anodal or sham cerebellar tDCS using a double-blinded study design while performing a balance task on a Lafayette Instrument 16,030 stability platform®. Mean platform angle and mean balance time were assessed as outcome measures.ResultsSignificant learning effects were found in all participants. Balancing performance and learning rate was significantly less in the group of middle-aged adults compared to our previous group of young adults. No significant effects of cerebellar tDCS were observed.ConclusionsOur findings are in line with other studies that have failed to prove robust effects of cerebellar tDCS on motor learning. The present findings, however, do not exclude cerebellar tDCS effects. tDCS effects may be more prominent after repeated stimulation, using other stimulus parameters, in patient populations, or in other motor learning tasks.Trial registrationNot applicable.

Semi-active vibration control of a semi-submersible offshore wind turbine using a tuned liquid multi-column damper

In this paper, a control system is proposed for the vibration suppression of a semi-submersible offshore wind turbine equipped with a tuned liquid multi-column damper (TLMCD). The TLMCD consists of three columns of liquid integrated into the superstructure of the semi-submersible platform. To improve the vibration suppression performance of the TLMCD, unlike previous works, the TLMCD is operated in a semi-active mode by introducing three flow control valves that allow liquid to transfer between columns. Since the rotor dynamics may greatly affect the platform vibrations, it has been included in the derived nonlinear dynamic model. In the proposed control loop, the closed-loop performance objectives of platform stabilization and rotor speed regulation are accomplished by two distinct controllers. For the platform stabilization purpose, three controller design methods of displacement-based ground-hook, velocity-based ground-hook, and bang–bang are investigated. Meanwhile, to achieve the rated rotor speed, two methods of the H∞ and gain-scheduling control schemes are attempted. The closed-loop performance is investigated through numerical simulations. Realistic wind profiles along with a wave disturbance are implemented in the numerical simulations. The results show that the gain-scheduling control scheme for the rotor speed regulation and the velocity-based ground-hook method for the platform stabilization outperform other methods. Furthermore, to study the effect of the design parameters of the TLMCD on the closed-loop performance, several cases with different values of the design parameters are examined and compared.