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The system for adaptive control of axial tool oscillations in vibratory drilling: description and experimental study
Get PDFChips must be reliably segmented and evacuated from the cutting zone for effective deep hole drilling. Drilling with low-frequency axial vibrations ensures these useful effects because cutting edges periodically leave the cutting zone. Useful tool vibrations can be maintained using a special self-vibratory drilling head. The drilling head has an elastic element and ensures the self-excitation of vibrations due to the regenerative effect. However, high damping in the cutting zone suppresses axial self-vibrations and renders such a drilling head inexpedient for industry. This study develops a novel system of adaptive control for the vibration drilling process. The control objective is to maintain a specified peak-to-peak (PTP) value of vibration displacements. Due to the in-process adaptation of the feedback gain, the control system supplies additional energy if vibrations are not self-excited and removes energy if the PTP vibration displacements are greater than the specified value. To test the workability of the system, an experimental setup was made. In the setup, the actuator force acts on an elastically fixed workpiece. The dynamic properties of the setup are equivalent to those of the vibration drilling head. The algorithm of feedback gain adaptation was implemented with a microcontroller. A number of experiments for different drilling regimes revealed that the control system successfully maintains the specified PTP value of displacements. The developed control system can be implemented on a vibration drilling head because only an accelerometer is required for control and the required actuator force is under 100 N
The impact of occlusal plane rehabilitation on the face of a patient with traumatic peripheral facial paralysis by Timpanic jugular tumor – case report
Get PDFThe musculature of the face is innervated by cranial nerves, each with a motor, sensory and/or both function. The Facial nerve (FN) is responsible for the motor innervation of the muscles of the face. Some branches of the trigeminal nerve are responsible for the sensory part of the facial muscles and other branches act on the motor part of the chewing muscles. Traumatic Facial Paralysis (TFP) is the one where there was section or traction or compression or ischemia of the FN, in surgery for tumor resection or trauma in general. In this case occurs the nerve’s section in one surgery. Facial Paralysis (FP) can be evaluated subjectively through the House and Brackmann classification scale (HB) [1]. It is considered a chronic FP when it persists for a period longer than 6 months and leaves sequelae, such as synkinesis, contractures and lack of complete innervation of some nerve branches. Some patients who evolve with chronic FP may also evolve with alteration of the occlusal plane. The occlusal plane is the meeting point between the antagonist teeth, plane that is in the final stop of the masticatory cycle. The rehabilitation of this plan is performed according to the needs of each patient, in this case was made through implant prostheses
An improved semi-supervised prototype network for few-shot fault diagnosis
Get PDFThe collection of labeled data for transient mechanical faults is limited in practical engineering scenarios. However, the completeness of sample determines quality for feature information, which is extracted by deep learning network. Therefore, to obtain more effective information with limited data, this paper proposes an improved semi-supervised prototype network (ISSPN) that can be used for fault diagnosis. Firstly, a meta-learning strategy is used to divide the sample data. Then, a standard Euclidean distance metric is used to improve the SSPN, which maps the samples to the feature space and generates prototypes. Furthermore, the original prototypes are refined with the help of unlabeled data to produce better prototypes. Finally, the classifier clusters the various faults. The effectiveness of the proposed method is verified through experiments. The experimental results show that the proposed method can do a better job of classifying different faults
Experimental and performance analysis of carbon/carbon bolt
Get PDFIn this paper, the mechanical properties of C/C composite bolts at normal temperature are studied. The strength performance of bolts under different load conditions of tension and shear is tested, which shows that they have different failure modes. It is concluded that the strength performance and failure mode of C/C bolts are directly related to the structural size and the braiding characteristic of the bolt. This can provide a basis for the optimal design of C/C bolts
Tensor analysis of tornadoes: a new analytical and numerical model
Get PDFThis research proposes a new mathematical formulation of tornadoes based on the theory of tensor analysis and simulation in a non-inertial dynamics framework, both in two and three dimensions. This model may show the spherical upward movement of air in a tornado without taking into account vertical convection. A tornado requires several elements, including geocentric latitude, the Coriolis effect, increased airspeed in the upper atmosphere, and increased air pressure. Computing the three-dimensional location of the tornado or hurricane, as well as the mathematical models of airflow motion and the Earth's rotation in three-dimensional (3D) space, can determine a tornado's airflow characteristics. To show tornado patterns, we employed computer software that computed motion dynamics and did numerical computations. The results of 2-D modeling and simulation indicated that the greater the initial tornado angular speed, the larger the tornado area. Three-dimensional modeling and simulation also show that tornadoes are more powerful at higher geocentric latitude angles. The novelty of this study is that this model can be used to explain tornado patterns. In our research, we combine tensor analysis, computational modeling, as well as 2D and 3D simulations for simulating tornadoes for the first time. The scientific application of this finding is that researchers at the Meteorology, Climatology, and Geophysics Agency will be able to analyze a tornado and geophysical phenomena more readily with simulations and models
Research on the algorithm for optimal selection of detection modes for rail crack detection
Get PDFIn the application of ultrasonic guided wave testing for rail crack detection, it is necessary to select a guided wave mode that is more sensitive to cracks as the detection mode. However, ultrasonic guided waves have multi-mode and dispersive characteristics. In order to extract mode information from complex signals, this paper proposes an optimal detection mode selection method based on the sensitivity of guided wave modes to cracks. This method is different from the traditional method of determining mode types by calculating the mode velocity through the arrival time of wave packets in the time domain signal. Based on the dispersion characteristics and mode features of guided wave modes, this paper establishes a crack sensitivity evaluation index. In a wide frequency band and among numerous modes, the guided wave modes suitable for detecting cracks in different regions of the full cross-section of rails are accurately selected. Experimental results show that the guided wave modes selected by the mode selection method proposed in this paper, based on the crack area energy and crack reflection intensity evaluation indexes, can accurately identify rail cracks, laying a foundation for the research on rail crack detection and localization methods
Damage deformation properties and acoustic emission characteristics of hard-brittle rock under constant amplitude cyclic loading
Get PDFIn order to study the deformation and damage characteristics of the limestone specimens with high strength and brittleness under constant amplitude cyclic loading, the deformation and the acoustic emission (AE) characteristics were analysed, and the relationship between them was sought. The damage variables under different amplitude cyclic loading were defined by AE counts. The results showed that the radial deformation of the limestone specimens was more sensitive and unstable than the axial deformation. The concept of apparent residual strain was proposed to describe the specimen deformation characteristics, and it resulted that the radial apparent residual strain produced at higher stress state would recover at lower stress state. The limestone specimens showed obvious Kaiser effect and Felicity effect under cyclic loading. When the upper limit of the cyclic loading was close to the peak stress of the specimen, the AE counts generated in unloading sections were almost the same as that in the loading sections. The damage was increased as the amplitude and the stress level increased and the unloading process at higher stress level would also lead to the aggravation of damages. Specimens would absorb more energy under cyclic loading than under uniaxial loading. Reasonable driving parameters should be controlled in underground excavation practice, to ensure that the stress level of surrounding rock mass in a periodic stress state is located before peak stress and such that to limit the occurrence of rock burst to a certain extent
Displacement analysis and numerical simulation of pile-anchor retaining structure in deep foundation pit
Get PDFFoundation pit excavation can cause settlement and displacement of surrounding existing buildings and roads. In order to study the influence of soil unloading on the surrounding buildings during pit foundation excavation, the application of a pile-anchor retaining structure in a deep foundation pit was studied, with the deep foundation pit project of Anhui Bright Pearl Mall as the research subject. Through theoretical analysis, field measurements, and FLAC3D numerical simulations, the supporting structure was comprehensively analyzed. A comparison was made between the measured displacement data and the numerical simulation results of the supporting structure and the surrounding environment during the excavation process of the foundation pit. The results indicate that the model results, obtained through the use of the FLAC3D software for numerical simulations, generally align with the field data. This approach can more accurately reflect the evolutionary laws of soil pressure and deformation during the excavation of the foundation pit. The maximum displacement of the horizontal displacement monitoring point in this project's foundation pit is 25.96 mm, which is less than the monitoring alarm value of 30 mm. The horizontal displacement monitoring of the sidewall of the foundation pit is crucial among them. An analysis of the three major causes of numerical deviation provides valuable insights for the design of deep foundation pit supporting structures
YOLOv3-MSSA based hot spot defect detection for photovoltaic power stations
Get PDFWith the continuous development of the energy industry, photovoltaic power generation is gradually becoming one of the main power generation methods. However, detecting hot spot defects in photovoltaic power stations is challenging. Therefore, enhancing detection efficiency using information technology has become a crucial aspect. The study presents a defect detection model for PV power stations using the YOLOv3 (You Only Look Once v3) algorithm. The model incorporates coordinate attention module (CAM) and self-attention module (SAM) to improve feature extraction in low-resolution conditions. The Multi objective Sparrow is employed to achieve multiple objectives. It is very contributing in the detection of low-resolution features. It shows that the research method can reduce the loss value to 0.009 after 400 iterations of the loss curve test. The precision-recall (P-R) curve generated by the research method only starts to drop sharply when the Recall value reaches 0.96. The number of parameters generated by the research method is 3.46×106. The detection accuracy of the research method reaches 98.86 % when there are five defective fault types. The results indicate that the proposed research method offers improved detection speed and higher accuracy in identifying hot spot defects in PV power stations. This technology provides valuable support for hot spot defect detection and presents new opportunities for the field
Prediction of residual life of rotating components based on adaptive dynamic weighting and gated double attention unit
Get PDFGears and bearings play vital roles as essential transmission components in mechanical drivetrains. Accurately predicting the remaining useful life (RUL) of these components is paramount to ensure optimal performance and prevent unexpected failures. To enhance the precision of RUL prediction, a novel method has been developed which involves constructing health indicators (HI) and implementing an adaptive dynamic weighting (ADW) on a gated dual attention unit (GDAU). The process commences by extracting multi-dimensional time-frequency domain features from vibration signals, which are then refined using an improved kernel principal component analysis (Adaptive Kernel Principal Component Analysis – AKPCA) to extract key components. Subsequently, the constructed HI is fine-tuned through an optimization process utilizing the exponentially weighted moving average method. Finally, the ADW strategy dynamically adjusts the input weights of the HI, and the GDAU model is employed to predict the RUL of gears and bearings. Experiment and comparison results have validated the effectiveness and advantages of the proposed method