Robotic Systems and Applications
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Vibration characteristics analysis of face gear transmission system considering gyroscopic effect
Get PDFTo improve the dynamics of the face gear transmission system, a nonlinear dynamics model considering gyroscopic effects and including parameters such as time-varying meshing stiffness, meshing damping, tooth side clearance, support stiffness and damping is developed. The Runge-Kutta method was used to solve the nonlinear kinetic equations and analyze the accuracy and reasonableness of the model calculation results. The vibration displacement, vibration velocity and vibration acceleration along each direction of the face gear and straight cylindrical gear were analyzed, and the torsional vibration characteristics of the center of mass of the two gears were studied
Controlling isolation system of initial combustion engines
Get PDFTo evaluate the effect of the engine vibration on the vehicle's ride comfort and improve the vehicle's ride comfort, three types of engine’s isolation systems including the traditional rubber mount (TRM), hydraulic mount (HM), and semi-active HM controlled by the PID control (SHM) are proposed. A dynamic model of the inline 4-cylinder engine is established to determine the excitation force of the engine. By the combination of the random excitation of the vehicle floor affecting the engine isolation system, the isolating performance of the TRM, HM, and HM is then simulated and evaluated on isolating the engine vibration and improving the vehicle’s ride comfort. Both the root mean square (RMS) values of the engine acceleration response (aRMSe) and isolation force (FRMS) of engine isolation systems are given as the objective functions. The research results show that the engine vibration combined with the excitation of the road surface roughness significantly affects the vehicle’s ride comfort. By using the SHM, both the engine acceleration and isolation force are significantly reduced in comparison with the TRM. Especially, the values of the aRMSe and FRMS are remarkably decreased by 9.32 % and 9.69 % in comparison with the TRM. Thus, to improve the vehicle's ride comfort and reduce the effect of the engine's vibration on the ride comfort, the engine isolation system used by the TRM needs to be replaced by using the SHM
Experimental study on influencing factors of anchorage performance of concrete bonded rebars
Get PDFHilti re-100 structural adhesive is used to plant reinforcement in concrete, and the factors affecting the anchorage performance of planted reinforcement are analyzed. The Planting reinforcement of the concrete specimen and the specimen with reinforcement anchored in concrete in advance are compared. A total of 36 groups of tests were carried out, including 27 groups of embedded reinforcement tests and 9 groups of embedded reinforcement tests. The test mainly analyzes the influence of concrete strength, reinforcement diameter and planting depth on the anchorage performance of planting reinforcement. There are three failure modes in the test, which are the separation failure of reinforcement and structural adhesive, the tensile failure of reinforcement and the separation failure of reinforcement and concrete. Through the analysis of the test data, the bond slip data curve is obtained
Hybrid energy efficiency mapping in major Saudi locations using small wind turbine-solar systems
Get PDFThe use of fossil fuels of all kinds, such as natural gas, coal and petroleum in energy production, is the main cause of environmental pollution from air, water and soil, which is the direct cause of acid rain, the destruction of forests, the acidity of lakes, and the extinction of many living creatures that could not resist what happened Burning this fuel is due to a change in the surrounding environment. From this, it becomes clear to us the need for new sources to produce clean energy that does not pollute the environment, and work must be developed on these new sources for use in the production of clean energy in the coming years. The purpose of this work is to determine the efficiency of vertical axis turbines to be among the components of a hybrid system (solar/wind) to generate electric power in the Kingdom of Saudi Arabia. The work seeks to answer the research question, what is the efficiency of vertical axis turbines in generating electricity within a hybrid system (solar/wind) to generate electric power in the Kingdom of Saudi Arabia. The aim of the work is to analyze the vertical axis turbines and determine efficiency within the hybrid system in the regions of Saudi Arabia. There are many renewable energy sources (wind, solar thermal energy, solar photovoltaic, biomass, small and large hydropower and geothermal energy). But their efficiency is not stable from time to time, so the idea of hybrid energy came to make up for the shortage, by integrating the energy source Renewables with one or more other sources of energy (In 1999, McGowan and Manwell (1999) presented a summary of WND-PV-DSL HPS progress in the United States.) whether it is a non-renewable or renewable source [1]
Multi-objective structural optimization of honeycomb cells
Get PDFThis paper develops an optimum cell structure design method considering the in-plane tensile/compression and shear properties to improve the stiffness and strength of the honeycomb core. The equivalent elastic modulus in the X or Y direction and shear modulus in the XY plane are derived using Energy Method for hexagonal, quadrilateral and concave hexagonal cells, and are compared with the results in the related literatures. The multi-objective optimization model in which the vertical wall length, wall thickness and inner angle of the cell are taken as design variables is solved by Genetic Algorithm to maximize the equivalent elastic moduli. The static and dynamic characteristics of the honeycomb cores with original and optimized cells are studied using Finite Element Method. The results show that after the cell optimization, the maximum displacement, stress and strain obviously decrease, thus improving the structural performance of the honeycomb core. The research provides significant guidance for the design of the cell structure
Research on 3D MFL testing of wire rope based on empirical wavelet transform and SRCNN
Get PDFMagnetic flux leakage (MFL) testing is one of the most effective methods in nondestructive testing of wire rope. However, traditional MFL testing devices have problems such as low recognition rate, single detection dimension and fuzzy magnetic leakage image. Based on the non-saturated magnetic excitation 3D MFL testing device, this paper proposes a wavelet denoising method based on empirical wavelet transform (EWT) to denoise the collected 3D MFL signal. After noise reduction, the Signal-to-Noise Ratio (SNR) and Root Mean Squared Error (RMSE) of the three dimensions have improved. Color imaging technology is used to fuse defect grayscale images into color images, and Super-Resolution Convolutional Neural Network (SRCNN) is applied to MFL images of broken wires. After SRCNN reconstruction, the resolution of defect color images is improved. The color moment feature of the defect color image is extracted as the input of the Elman neural network to quantitatively identify broken wires. Experimental results show that the noise reduction algorithm can effectively suppress the noise in three dimensions, and the broken wires recognition rate after reconstruction has been significantly improved, which verifies the effectiveness of SRCNN in wire rope MFL images
An on-line monitoring method for the flow excitation in francis hydraulic turbine based on dynamics
Get PDFDuring the operation of hydraulic turbine, the vibration often exceeds the standard due to flow excitation, which affects the safe and stable operation of the hydraulic turbine. In this paper, an on-line monitoring method for the flow excitation in Francis hydraulic turbine is proposed based on the dynamic characteristics of Francis hydraulic turbine. Firstly, based on the flow excitation characteristics in Francis hydraulic turbine and the dynamic equation of main shaft system, the internal relationships between the dynamic response of turbine bearing and the flow excitation in the Francis hydraulic turbine are clarified. Secondly, according to these relationships, a method based on wavelet transform (WT), particle swarm optimization (PSO), and variational mode decomposition (VMD) is proposed for extracting the flow excitation features in Francis hydraulic turbine. Then, by this method, the flow excitation features are acquired. Based on the obtained flow excitation features, the flow excitation can be monitored on-line. Finally, the proposed on-line monitoring method for the flow excitation in Francis hydraulic turbine is verified by experiments. Based on the results, the flow excitation components in the signal extracted by this method are about 35 % more than those extracted by the previous methods. The results show that the on-line monitoring method proposed in this paper is convenient and effective
Study of skeletal changes in individuals with anterior open bite treated with JFO
Get PDFAnterior Open Bite (AOB) is a type of malocclusion that promotes severe esthetic aesthetic and functional impairment. Its etiology is multifactorial and may involve several etiological factors, such as deleterious oral habits, hypertrophic tonsils, mouth breathing, dental ankylosis and eruption abnormalities either associated with genetic factors or not. AOB is one of the most challenging treatments in any treatment protocol. A retrospective study of 21 patients with anterior open bite treated with Jaw Functional Orthopedics (JFO) with improvement in overbite was conducted with the aim of understanding mandibular behavior during the treatment. Using SPSS 11.0, using Shapiro-Wilk test all variables showed Normal distribution (p> 0.05), in the comparison between the means at T0 and T1, the t-test for paired samples was used. In order to verify whether cooperative patients had better results than the non-cooperative group, a variable was created. For all tests, a significance level of 5 % was used. A weak statistical correlation (P< 0,1) was found for Bimler’s Factor 8. Change resulted from AOB treatment with FOA in a short time. There was no statistical correlation of Bimler’s Factor 8 when cooperative patients were compared with the non-cooperative group. It could be concluded that in the studied sample there was a weak correlation between overbite improvement during AOB treatment with JFO and mandibular rotation. Further studies are necessary to understand the skeletal behavior of the maxillary bones in the treatment of AOB with FOA
Preparation and water collecting properties of cement-based porous condensation material
Get PDFCommon Portland cement was used as the main matrix material and cementations material, fly ash as admixture, 30 % wt hydrogen peroxide as foaming agent and other additives to prepare cement based condensate porous material. The optimum amount of foaming agent was determined by water absorption and release experiment, and the metal fiber was added to the material to enhance the water collecting performance. As the amount of foaming agent increased, water absorption increased, water release rate decreased, the optimum content of foaming agent was 2.73 %, the material had better water absorption and water release performance, and the addition of metal fiber could obviously improve the water collection performance of cement-based porous condensate material
Effect of the geometrical parameters on the vehicle's moving stability
Get PDFTo enhance the moving stability and safety of vehicles, kinematics and dynamics model of the vehicle consisting of a guided front wheel and a free rear wheel is established based on the model of a four-wheeled vehicle when the vehicle moves on the curve-road. The effect of the geometrical parameters and dynamics parameters including the factor of the moving stability, vehicle moving speed, lateral stiffness parameters of the front and rear wheels, vehicle mass, vehicle length on the vehicle moving stability and safety is then simulated and analyzed, respectively. The research results indicate that the operating parameters of the vehicle greatly affect the vehicle moving stability. The lateral stiffness parameters of the front and rear wheels should be increased while the vehicle mass needs to be reduced in the operating condition of the vehicle to enhance the vehicle moving stability. Besides, the vehicle length L should be reduced and the longitudinal distance of a needs to be distributed by 0.95×a to further improve the vehicle moving stability