Jaw Functional Orthopedics and Cranoficial Growth
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Adaptive robust control of electromagnetic actuators with friction nonlinearity and uncertainty compensation
No full textFriction nonlinearity and uncertainty are the main factors affecting the highly performance control of electromagnetic actuators. In this paper, a nonlinear adaptive robust control strategy is proposed of electromagnetic actuators with friction nonlinearity and uncertainty compensation. First, the dynamical model of the electromagnetic actuator is established considering nonlinearity and uncertainty. Then, an adaptive robust controller is designed based on the continuously differentiable friction model to ensure that the control input is continuously and bounded. In the design of the controller, the unfavorable effects of unknown parameters in the electromagnetic actuator are eliminated by constructing a parameter adaptive law. Meanwhile, in order to improve the tracking accuracy of the electromagnetic actuator, a nonlinear robust control law is designed to ensure the robustness of the controller. The stability analysis by Lyapunov function shows that the asymptotic tracking effect can be obtained when only parameter uncertainty exists in the closed-loop system of the electromagnetic actuator, and the consistent bounded stability can be ensured when the system also exists uncertain nonlinearity. Extensive comparative results verify the effectiveness of the proposed control method
Ferroresonance phenomena in power systems
No full textIt is a known fact that the world's dependence on electrical energy is increasing day by day. The fact that electrical energy has some advantages over other types of energy, the increasing world population and changing living conditions can be considered among the reasons for this increase. This increase in dependence on electrical energy can be met by expanding existing facilities and establishing new facilities. In these studies, the transmission of electrical energy from the place where it is produced to the place where it is consumed poses important problems as the system expands. Some work is required to eliminate these technical and economic problems and to ensure stable operation of the system. These are problems that were not considered beforehand as the system grew. One of these problems is the ferroresonance phenomenon that occurs at the fundamental frequency due to the nonlinear magnetization characteristics of transformers. Ferroresonance is a resonance phenomenon that occurs in an electrical circuit containing an iron-core self-coil as a nonlinear element. This resonance manifests itself with sudden oscillations in the output size of the system caused by a small change in the amplitude or frequency of a magnitude applied to the input of the system. High voltage transmission lines are double-circuit lines that share the same pole. In special cases such as maintenance or malfunction of such a transmission system, one of the lines can be disconnected from the system and continue energy transmission with the other line. In the high voltage transmission line, the system may oscillate due to the stored energy in the magnetic field of the transformer inductance on the disabled line and the electric field of the line capacity. This oscillation disappears after a certain period of time due to iron losses and other circuit losses. When these losses are covered by the other transmission line, permanent oscillations and over voltages may occur at the transformer terminals. All these events are the negative effects of ferroresonance on transmission systems. In the energy transmission system, ferroresonance phenomenon occurs. Over voltages may occur in case of idle power transformers in star point/isolated networks. In medium voltage networks, ferroresonance occurs due to the melting of a fuse, the opening and closing of voltage transformers with one pole, and the dissymmetry that occurs as a result of a connection process. These negative effects caused by ferroresonance in the energy transmission power system are discussed in detail within the subject of this study
Enhancing non-destructive testing in concrete structures: a GADF-CNN approach for defect detection
No full textThis research introduces a novel approach for detecting defects in concrete structures. It utilizes the Gramian Angular Difference Field (GADF) in combination with a Convolutional Neural Network (CNN) enhanced by depthwise separable convolutions and attention mechanisms. The key contribution of this work is the use of GADF to transform one-dimensional impact-echo signals into two-dimensional images, thereby improving feature extraction and computational efficiency for analysis by the CNN. This advancement offers a new perspective in non-destructive testing technologies for concrete infrastructure. Comprehensive evaluation on a varied dataset of concrete structural defects reveals that our GADF-CNN model achieves an impressive test accuracy of 98.24 %, surpassing conventional models like VGG16, ResNet18, DenseNet, and ResNeXt50, and excelling in precision, recall, and F1-score metrics. Ultimately, this study enhances the integration of sophisticated image transformation techniques with deep learning, contributing to safer and more durable concrete infrastructure, and represents a noteworthy development in the field
Case report – distoclusion treated with Bimler A períod of 12 months
No full textThe Bimler type A utilizes forces derived from muscles, particularly the tongue, concomitantly, it acts as a systemic, dynamic and functional treatment, Bimler appliances transmit neural excitation throughout the system. The objective of this study was to present a clinical case and demonstrate the efficacy of the functional orthopedic appliance, specifically the Bimler A elastic modeler, in the treatment of a patient diagnosed with distoclusion (prognathism of the maxilla and retrognathism of the mandible) according to Bimler and McNamara cephalometry. The case involved a 9-year and 11-month-old male patient with atypical swallowing, respiratory issues, and allergic conditions such as asthma. Clinical examination and complementary tests revealed a large overjet, a narrow maxilla and mandible, an open bite, and distoclusion (retrognathism). The proposed intervention included the installation of the Bimler Elastic Modeler (BEM), type A. The treatment duration was 12 months, with ongoing monitoring every 2 or 3 months. The comprehensive approach, combining BEM type A, chewing exercises, and occlusal adjustments, resulted in orthopedic changes improved mandibular, tongue, lip, and head posture, as well as enhanced chewing balance. Importantly, the appliance effectively repositioned the mandible into a more balanced, normoccluded position without the need for elastic or constant forces. Beyond the orthodontic changes, the active engagement of facial expression muscles during these activities contributed to an overall improvement in facial harmony, achieving lip seal and notable enhancements in breathing. These positive changes extended to the patient’s daily activities and sports performance. The observed outcomes not only increased the child’s active participation in the treatment but also positively impacted self-esteem, driven by the aesthetic, functional, and psychological improvements experienced
Finite element analysis of rockfall impact on pipelines with different erosion resistant coatings
No full textIn this paper, the finite element analysis method is used to extensively study the response of rockfall impact on pipelines with different erosion resistant coating. Based on the numerical results, the safety of the pipeline is comprehensively evaluated. Firstly, through the establishment of detailed pipeline and rockfall models, the impact of different rockfall materials and speeds on the pipeline is simulated. The results of the finite element analysis indicate that rockfall impact can cause significant stress concentration and deformation in the pipelines and damage to the coating. With the increment of impact speed, the damage to the pipeline also increases significantly, and different rockfall materials exhibit varying damage conditions, and it is found that fibreglass reinforced epoxy is better than the polyethylene coating. By comparing the analysis results under different conditions, the safety threshold of the pipeline under various rockfall impact scenarios is obtained. This provides an important theoretical basis and reference for the protection design and safety maintenance of the pipeline. The research in this paper not only aids in deepening the understanding of the mechanism of rockfall impact on pipelines but also serves as a valuable reference for improving the safety and reliability of pipeline engineering
Lubrication optimization of high-speed train drive gearbox
No full textThe gears in the high-speed heavy-duty gearbox of the high-speed train are typical high-speed heavy-duty gears. Combined with the transmission principle and structural characteristics of the high-speed train drive gearbox, to ensure adequate lubrication of meshing gears and bearings, an optimization of the lubricating oil flow inside the gearbox was conducted. The oil and gas two-phase flow model inside the gearbox adopts the VOF model, and the turbulence model adopts the standard κ-ε model. Fluent is used for simulation calculation. The results show that the exhaust port position of the gearbox has little effect on the flow of lubricating oil inside the gearbox; the overall pressure distribution inside the gearbox is relatively uniform, with higher pressure only at the meshing gears; the distribution of lubricating oil inside the gearbox is related to the rotation of the gears, and the flow velocity of lubricating oil is mainly affected by the rotation of the gears, with the maximum flow velocity appearing around the gears; the flow of lubricating oil inside the gearbox meets the lubrication requirements of the gearbox. These results provide support for the lubrication design, flow channel structure improvement, and effectiveness evaluation of high-speed train transmission gearboxes
Object localization of channel robot using laser triangulation
No full textTrajectory tracking and Object Localization in robots are developing rapidly, but the tasks are becoming increasingly complex and significantly increasing the range of tasks for robotic systems. Cognitive tasks in domestic, industrial or traffic conditions require not only the recognition of objects but also their evaluation by classifying them without direct recognition. One of such spheres are tunnels that are physically difficult for humans to reach and require diagnostics. In such an environment, it is difficult to globally define the direction and goal, so it is necessary to interpret the locally obtained information. To solve such a problem, sensor fusion is widely applied, but sensors of different physical natures do not allow to obtain the necessary information directly, so there is a great need to use AI to interpret and control the received information and generate the robot's trajectory [1]. Local navigation systems require a wide range of sensors [4]. Various cameras and time-of-flight LiDAR lasers are widely used. For the aforementioned reasons, an economical local trajectory generation and tracking system is being developed, one of the most important components for object recognition is the laser triangulation method. The essence of this method is that the camera reacts to the projection of the laser light in front of it and interprets the obstacle depending on its distortion. In this way, the camera's resources are more concentrated, and at the same time, a simple RGB camera is enough for this method. Also, this method is perfect in the dark, when the laser light is more pronounced. In this paper, the laser triangulation method will be reviewed in detail, evaluating its advantages and disadvantages
A recent lower limb exoskeleton robot for gait rehabilitation: a review
No full textHuman rehabilitation improved significantly after traumas, surgery, or accidental cross-link events with human health. During the last six decades, exoskeletons have played a significant role in human activities related to body training and post-trauma or surgery treatment, especially in gait rehabilitation. The main goal of rehabilitation training is to restore patients’ physical abilities to average by improving and monitoring their posture and gaining weight. In this paper, a classification of various types of exoskeletons is provided, a comparison between the different lower limb exoskeletons for gait rehabilitation presents, the gait anatomy, mechanical design, and control strategy for the prototype of lower limb exoskeleton studies, and the end, some concluding remarks are stated that may be useful for future work. The paper concludes with conclusions and a significant reference list
Research on the relationship between feature extraction time and training samples of hyperspectral image based on spatial domain
No full textHyperspectral image (HSI) feature extraction is an important means to improve the classification of different ground features. According to the structural characteristics of hyperspectral data, the general feature extraction scheme can extract features from the point of view of spectral dimension, spatial and spatial spectrum. And the feature extraction time is also an index to measure the feature extraction method. Therefore, from the perspective of spatial dimension, this paper explores the relationship between HSI feature extraction time and training sample ratio. Three groups of HSIs sets were used for correlation test and analysis in the experiment. According to the characteristics of different data sets, the best selection scheme between spatial domain feature extraction method and training samples is given
Simulation of locomotion conditions of an enhanced vibration-driven in-pipe robot
No full textThe paper aims to analyze the improved design of an in-pipe vibration-driven robot, which is equipped with a self-locking mechanism, electromagnetic exciter, and size-adapting devices. The study focuses on examining the robot’s locomotion conditions at different working regimes. The research methodology contains four main stages: analysis of the design peculiarities of the enhanced wheeled in-pipe vibration-driven robot; developing a simplified dynamic diagram and deriving the differential equations to describe its locomotion conditions; carrying out numerical modeling with the help of Mathematica software to analyze the robot’s basic dynamic parameters; conducting virtual experiments and testing the robot locomotion characteristics by means of the computer simulation in SolidWorks Motion software. The results obtained include the time-based data on the robot’s displacement, speed, acceleration, and consumed power under different operating conditions, such as varying forced frequencies and excitation force amplitudes. The novelty of this investigation lies in identifying efficient working regimes for the improved wheeled vibration-driven robot intended for moving inside the pipelines. Future research will focus on developing a full-scale experimental prototype of the robot and conducting laboratory investigations at different working regimes. The findings of this research are valuable for scientists and engineers involved in the study and design of similar vibration-driven locomotion systems