Science & Technology Development Journal - Engineering and Technology

Simulating the piezoelectric substrate influence on the characteristics of surface acoustic wave-magnetostriction sensor based on the FeNi magnetic sensitive material

2022-05-15T21:59:53+00:00

This paper simulates the influence of two piezoelectric substrate types on the sensitivity and measuring range of surface acoustic wave-magnetostriction (SAW-MO) sensor by the finite elements method (FEM) based on using the FeNi magnetic sensitive layer with E-H chacrateristics (Young’s Modulus – Magnetic field intensity). The sensor structure selected for the study is the delay-line: the distance between the two sets of electrodes is 5mm, the number of finger pairs of each electrode set is 25, and the distance-width between the fingers is 10m regularly, the electrode material is aluminum. The piezoelectric substrates chosen for simulation are LiNbO3 and AlN in which the LiNBO3 piezoelectric substrate is the block form with the surface velocity of 3318.1m/s and the AlN piezoelectric substrate is the thin film with the surface wave velocity of 5598.9m/s. So the generality is ensured when evaluating their influence on the response of SAW-MO sensor. For magnetic sensitive materials, the group selected the FeNi which E-H characteristics was experimentally built. During simulation by finite elements method, the sensor structure is tested with many datasets whose number of divided elements is different. However, the simulation results have converged with the number of divided elements is 113556. The simulation result shows that the sensivity of the FeNi/IDT/AlN structure magnetic sensor is larger than the FeNi/IDT/LiNbO3 structure magnetic sensor with sensitivities of 8.698kHz/Oe and 2.345kHz/Oe, respectively. The result also indicates that the response range of the FeNi/IDT/AlN magnetic sensor is [0 ÷ 109]Oe, which is smaller than the FeNi/IDT/LiNbO3 magnetic sensor is [0 ÷ 190]Oe.

Selective harmonic elimination for cascade modular multi-level inverters using GA and GWO algorithms

2022-05-24T22:33:24+00:00

Nowadays, the study of methods to control the inverter by applying optimization algorithms to eliminate selective harmonics (Selective Harmonic Elimination (SHE)) is attracting more and more attention of researchers. These studies are divided into two directions: evolutionary algorithms and swarm intelligence, in which genetic algorithm (GA) represents the group of evolutionary algorithms, and one solution recently appeared is the gray wolf algorithm (Grey Wolf Optimizer: GWO) which represents the group of swarm intelligence algorithms. When applied to the SHE problem for the inverter, these algorithms show positive results. However, there has not been an evaluation of both time and total harmonic distortion (THD) over the entire range of modulation index between the two methods GA and GWO when applied to multi-level inverters. Therefore, the article gives detailed evaluations in terms of time and harmonics of the above methods to see the advantages and limitations of each algorithm on each segment of the modulation ratio to the modular 11 -levels cascade inverter. Modular multi-levels cascade inverter is simulated by Matlab/Simulink software to verify GA and GWO control algorithms.

Applying image processing for autonomous finding welding line for industrial robot

2022-05-25T22:24:22+00:00

Currently, at the Vietnamese factory, continuous straight-line welding is still done manually or by workers. Some factories have manipulators to do this, but workers have to teach the robot to recognize the weld using a Teach-pendant device. Those jobs will take a lot of time for a welding job as well as uneven product quality. The purpose of the research is to develop an automatic system that combines computer vision and an industrial manipulator with 6 degrees of freedom (6DOF) that can recognize the weld line automatically and command the manipulator to follow the line profile. First, by using a 3D camera and laser system mounted at the end of the 6DOF manipulator and combined with the laser triangulation image processing algorithm, the position of the path from the starting point, sub-point and point weld end are extracted. Then, using an interpolation algorithm, the trajectory is calculated and transmitted to the manipulator. By using this method, the quality of the welded product is guaranteed and also the quantity of welding is increased as the Robot can work from time to time and especially for repetitive tasks. The installation time to weld the product is significantly reduced with the help of the computer vision system. The efficiency of the system is proven through experiments.

Modeling and Simulation of New PWM Techniques for Hybrid 7-Level Inverters Using Simplified Switching Table

2022-06-03T13:18:00+00:00

Nowadays, Cascade H-bridge (CHB) multi-level inverters (MLI) have many applications in the fields of electric drive control, high-power energy control, medium-voltage power grids, and popularization in the conversion of renewable energy power. In order to improve the quality of MLI to meet today's needs while reducing costs, it is necessary to have new methods to improve the working efficiency of the converter. Therefore, this paper presents a novel PWM control for single-phase cascaded hybrid 7-level inverter using simplified switching table (SST). The SST table converts switching states of the traditional multi-level inverter to the switching state of the hybrid cascaded inverter. The SST table is effectively designed to reduce the number of switching when performing output voltage control, thus improving the converter's working efficiency. The PWM method using proposed SST has the advantage of simple implementation, utilizing the traditional Sin-PWM techniques without re-calculating the control function or changing the carrier waveforms. The effectiveness of the proposed method will be evaluated through the voltage and current harmonic distortion factors when applying level shift carrier arrangements (LS-PWM) and speed control application of 3-phase asynchronous motor. Furthermore, in order to prove the advantage of the PWM technique using the proposed SST, the power loss of the 7-level hybrid cascaded inverter is also calculated and compared with traditional seven-level inverter and 3-level inverter. The analysis and modeling results of the 7-level hybrid inverter control are verified and evaluated using MATLAB SIMILINK and PLECS software.

Damage localization in reinforced concrete beams strengthened with FRP sheets using modal strain energy method

2022-06-03T13:24:16+00:00

Civil structures are affected by many different factors from the environment, loads, aging of materials, … These factors are uncertain variables and affect the health of the structures. Therefore, structural health monitoring (SHM) is very essential to detect damages early for necessary maintenance. In this paper, damaged locations in reinforced concrete beams strengthened with FRP (Fiber Reinforced Polymer) sheets are identified by using the modal strain energy method. First, a reinforced concrete beam strengthened with FRP sheets is simulated by ANSYS APDL software in order to analyze the beam’s behavior and get vibration responses. The reliability of the simulation is verified by comparing the load - displacement relationship between numerical and experimental results. Next, the modal strain energy method is employed to determine the damaged locations (crack and debonding) in the beam. In which, a set of indicators to evaluate the accuracy of damage localization results is proposed. The feasibility of the method is demonstrated through two problems. For problem 1, five different damage scenarios including concrete damage and FRP debonding are examined to evaluate the modal strain energy method’s feasibility for damage detection in the target beam. For problem 2, damages occurring in the beams are analyzed and determined according to each load level corresponding to the real working of the target beam. The results show that the modal strain energy method has high accuracy in detecting and locating damages in reinforced concrete beams strengthened with FRP sheets.

Application of deep learning in brain tumor segmentation

2022-06-12T03:10:53+00:00

Glioma is one of the most common brain tumor worldwide. Nowaday, glioma identification and segmentation is essential when making clinical decisions. Obviously, manual segmentation is not only time consuming but also subjective, in addition to this task, it is rather difficult to solve the solution of the automated segmentation methods. U-net architecture is one of the popular deep learning models for segmentation of biomedical images. This study implements a 2 dimensional convolutional neural network based on a U-net architecture. The proposed model is trained only with 2D images (slices) from 3D MRI dataset to segment the different tumor regions. Futhermore, in the preprocessing step some methods are applied to deal with imbalanced data for three brain tumor regions, and then data augmentation is utilized to prevent overfitting when training with a small dataset. The evaluated results based on the Multimodal Brain Tumor Segmentation Challenge (BraTS) 2018 dataset get the high accuracy for Dice scores of whole tumor, tumor core and enhancing tumor being 0.88, 0.81 and 0.76, respectively. The performance of the proposed model show that the brain tumors can be recognized with high accuracy compared to the similar studies. The proposed study has provided an analytical procedure for glioma brain tumors, from preprocessing to the training model, and then assessing factors that may affect the performance of the achived results.

Modelling of the cooling effect enhancement in drilling fluid using nanotechnology

2022-06-29T04:22:22+00:00

Drilling fluid is indispensable to assure the safety and success of a drilling operation. Besides the normal drilling fluid such as water-based mud or oil-based mud, a new kind of drilling fluid has emerged recently, which consisted of the use of nanotechnology. The aim of this paper is to study the cooling effect of nano-drilling fluid used in the petroleum industry. A dynamic model that included a reservoir formation, a well, and a drill string in the drilling process with drilling fluid circulation was built for this objective. Navier-Stoke equation was used for the fluid flow inside the well and the drill string, while Darcy’s equation was used for the flow inside the formation. The rise of temperature due to friction was also accounted for in this model. Two types of drilling fluid were used in the simulation: the normal drilling fluid and the one using nanotechnology. The change of temperature in the wellbore and in the formation over time with these two types of drilling fluid was observed at various positions: at the bottom hole where the drilling bit is constantly in contact with the formation, and at other places further away from the bottom hole. The simulated results showed that, although the temperature fluctuated in the two cases but on average, the nano drilling fluid gave a better cooling effect in comparison with the normal one. This article is the first study about the application of nanoparticles in drilling fluid in Vietnam using an integrated modeling method. The approach proposed in this article can be applied efficiently in practical applications of nano drilling fluid for petroleum drilling in Vietnam. However, it is noted that this research treated typically the technical side of the application of nanotechnology in drilling fluid, while it will be necessary to asset the financial aspect in order to make this technology a real-life application.

Investigating droplet size and spraying span of pesticide Drone

2022-06-30T20:47:35+00:00

This study investigates the characteristics of the spraying system on unmanned aerial vehicles developed by the company NOBA Robotics. Four spraying methods including: manual and with hand-held machine, tractor and UAV as well as the experimental arrangement are presented. The results show that the effectiveness of the UAV method is clear in terms operating time. Parameters such as coverage area, spraying span, size and uniformity of droplet are calculated by the analytical method and compared with those provided by the manufacturer and experimental results from which to evaluate the effectiveness of using UAV in pesticide spraying. Different nozzle layouts that can lead to different spraying effects are analyzed based on experimental results. The specifications and characteristics of the pump system are tested against different power levels to ensure the reality of the operating system. Droplet size, flying altitude on sprayed object and horizontal wind speed are also discussed in evaluating spraying efficiency. The results of this study show that the method of using UAV gives 20 times more productivity than the manual method without reducing the effectiveness of pest control.