Robotic Systems and Applications
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Static analysis of dynamic servo tool rest considering the influence of precision error
Get PDFThe analysis of the reliability of dynamic servo tool rest using traditional methods is inaccurate because the influences of the accuracy of gear machining and assembly are not considered. In this study, a static analysis method for dynamic servo tool rest is conducted considering the influence of accuracy error. Firstly, the working principle of tool rest is analysed, and its working process is divided into two actions, namely, initial positioning and locking. Secondly, the error sources of dynamic servo tool rest are investigated, and the transmission angle error is divided into two kinds, namely, assembly error of shafting and machining error of gear. The static analysis of tool rest is performed by considering the influence of the transmission error of the tool rest. Results show that the assembly, machining and locking forces of the fixed tooth disc of the dynamic servo tool rest have important effects
Magneto-thermal coupling analysis of the permanent magnet eddy current brake under intensive impact load
Get PDFTo more realistically describe the operation of an eddy current brake under intensive impact load, a magnetic-thermal bidirectional coupling model of the eddy current brake is established considering the existence of temperature. The variation of material and convective heat transfer coefficient with temperature are considered in the model. The iterative method is used to decouple the model. Through the analysis of the numerical simulation results, the temperature distribution and transmission of the brake during operation are obtained. By comparison, it is found that the calculated braking force of the magneto-thermal coupling model is lower than the calculated value without considering the temperature field due to the influence of temperature. And the higher the temperature, the greater the decrease
Study on penetration characteristics of honeycomb aluminum
Get PDFIn order to analyze the mechanical properties of projectile penetrating honeycomb aluminum, a dynamic nonlinear finite element model of projectile penetrating honeycomb aluminum was established and verified by experiments. It is found that the numerical simulation results of projectile penetration into honeycomb aluminum are consistent with the acceleration variation of the test. When the projectile penetrates into the honeycomb aluminum, the acceleration waveform is trapezoidal and the peak and pulse width of the acceleration are related to the velocity of the projectile and the wall thickness of the honeycomb aluminum material. With the increase of the velocity of the projectile, the peak value of the acceleration increases and the pulse width of the acceleration decreases. With the increase of the wall thickness of honeycomb aluminum, the peak value of acceleration increases, while the pulse width of acceleration decreases
Identification and location of ship pipeline leakage based on VMD
Get PDFPipeline plays an important role in various systems of the ship. However, due to the harsh environment, leakage often occurs in ship pipeline. This paper proposes a method to identity and locate the pipeline leakage. Using the variational mode decomposition (VMD) algorithm, the vibration signal is decomposed into band-limited intrinsic mode functions (BIMFs). The effective BIMFs are then selected by the correlation coefficient. Center frequency and energy value of the effective BIMFs are extracted as feature vector. Radial Basis Function (RBF) neural network is then used as a tool to identify and locate the leakage. The proposed method is finally verified by experiments
Linear forced-rotordynamics analysis for optimizing the performance factors of machine motorized spindle using design explorer method
Get PDFA machine-tool structure optimization is an important technique that improves the machining efficiency and saves materials and the energy resource. In this work, dynamic design optimization method for Machine-Motorized-Spindle (MMS) subjected to a number of rotating unbalanced forces effects is presented. Linear forced-Rotordynamic analysis with design explorer method has been used to simulate the output response. The Design Variables (DVs) and their limits were carefully chosen and applied to develop the Design-of-Experiment (DOE). The Box-Behnken Design (BBD) method, because of its good organization in providing much information in a minor number of required statistical experiments was used to generate the DOE. The influences of DVs on the dynamic of MMS and their levels optimization were evaluated by utilizing the Response-Surface (RS) method. The results showed that the spindle shaft inner diameter of the motor-rotor seat and its rotating unbalanced mass, and modulus of elasticity have the highest contribution in effect on the dynamic of MMHS. As well, it is found that the proposed optimization method not only improves the structural weight of MMS, but also the potential saving can be achieved in term material and energy resource
Damage detection in sluice hoist beams subject to excitation at resonance frequency band based on local primary frequency
Get PDFCracks of sluice hoist beams due to the load and aging of the material threaten the safety of sluice structural system. As the one of the main methods of damage detection, the non-destructive detection method based on natural frequency is still insensitive to local damage. Therefore, this paper proposes a method for hoist beams damage detection driven by resonance frequency band based on local primary frequency in the local mode. Firstly, the possibility of damage detection based on local primary frequency is discussed and the procedure of determining resonance frequency band is explained. Then the damage identification index based on the change ratio of local primary frequency is provided. Finally, numerical results demonstrate the correctness and effectiveness of the proposed method. The proposed method can provide reference for damage detection of hoist beams and health monitoring of sluice structural system
Study on applicability of end corrections of extended inlet and outlet of expansion chamber hydraulic noise suppressor
Get PDFAt present, a study on the end corrections of extended inlets and outlets of expansion chamber gas mufflers is relatively mature. However, such a research for an expansion chamber hydraulic suppressor has not been made yet. A coaxial and a non-coaxial expansion chamber configurations were introduced into hydraulic systems in this paper, and one-dimensional (1D) analytical approach was used to construct mathematical models of these structures and to verify it by experiments. After that, combined with the finite element method (FEM), researches on whether end corrections of the structures are applicable or not were studied
Stability of stope structure under different mining methods
Get PDFThe ore body has a great influence on the stability of surrounding rock and mining safety under different mining modes, and the reasonable selection of mining mode depends on other characteristics, such as ore structure surface feature, rock mass mechanical property, and ground stress distribution. Given the insufficient mining research data, this study establishes a 3D model by using the FLAC3D calculation program. Through numerical simulation and other technical means, a preliminary study on plastic and minimum stress changes during horizontal pillar mining, stress changes under different mining modes, and the effect comparison of full filling mining modes is conducted. Results show that the surrounding rock at the corner of pillar 1 is damaged, the plastic zone decreases, and the minimum stress in each working procedure increases slightly. The area of the plastic zone in alternate mining is smaller to that in continuous mining. This study provides a theoretical basis for ore body mining
Fault diagnosis method for energy storage mechanism of high voltage circuit breaker based on CNN characteristic matrix constructed by sound-vibration signal
Get PDFAiming at the problem that some traditional high voltage circuit breaker fault diagnosis methods were over-dependent on subjective experience, the accuracy was not very high and the generalization ability was poor, a fault diagnosis method for energy storage mechanism of high voltage circuit breaker, which based on Convolutional Neural Network (CNN) characteristic matrix constructed by sound-vibration signal ,was proposed. In this paper, firstly, the morphological filtering was used for background noise cancellation of sound signal, and the time scale alignment method based on kurtosis and envelope similarity were proposed to ensure the synchronism of the sound-vibration signal. Secondly, the Pearson correlation coefficient was used to construct two-dimensional image characteristic matrix for the expanded sound-vibration signal. Finally, the characteristic matrix was trained by utilizing CNN. Local Response Normalization (LRN) and core function decorrelation were utilized to improve the structure of CNN model, which reduced the bad impact of large data fluctuation of energy storage process on the diagnostic accuracy of circuit breaker energy storage mechanism. Compared with the traditional method, the proposed method has obvious advantages, whose total accurate rate up to 98.2 % and generalization performance is excellent
Radiation damping for rigid foundations. Approximate expressions
Get PDFThe dynamic response of machine foundations was one of the first problems studied in soil dynamics with results going back to the 1930s. A number of approximations and graphical results were proposed in the 60s. In this paper we present a series of approximate expressions for the natural frequencies and effective damping of rigid masses on the surface of an elastic half space subjected to both vertical and coupled horizontal-rocking harmonic excitations. The formulas are obtained using the approximate expressions for the dynamic stiffness of circular foundations suggested by Veletsos et al [1, 2] for two different values of Poisson’s ratio of the soil. For the vertical case the expressions are only a function of the mass ratio (ratio of the mass of the foundation to an effective mass of soil) and of Poisson’s ratio. For the horizontal-rocking case they depend also on the ratio of the height of the foundation to its equivalent radius (a slenderness ratio)