Abstract: With the rapid development of modern precision manufacturing industry,actuators with high resolution and long stroke are needed in many application fields. Linear piezoelectric motors adopting inertial impact driving mechanism has been driving the interests of many researchers for simple structure and compact size. To increase the efficiency of this type of stepping linear motor, a motor using two piezoelectric stacks was proposed in this work. Two piezoelectric stacks were placed in vertical and were pre-tightened by an elastic thin plate. Support for the stator was designed. Operation principle of this motor was analyzed. To validate this operation principle, a prototype was fabricated and testing on this prototype was conduct too. By applying saw wave voltage signal to piezoelectric stacked in this prototype, the stator of the motor is able to push its mover move with pace length of 2 micrometer.
Abstract: The dynamics of a rotating flexible cantilever beam is investigated by using assumed mode method, finite element method and Bezier curve interpolation method in this paper. The longitudinal deformation and the transverse deformation of the flexible beam are considered and the coupling term of the deformation which is caused by transverse deformation is included in the expression of longitudinal deformation. The assumed mode, finite element and Bezier interpolation are used to discretize the deformation of the flexible beam, and then the dynamics equations are built by Lagrange equation, and a software package for the dynamic simulation of the rotating cantilever beam is developed. Two cases are considered in the simulations. One is the dynamics study which the external rotating torque is known, another one is that a rotating fixed axis flexible beam falls with gravity. According to the simulation results, assumed mode, finite element and Bezier interpolation method can be well used for discretizing the deformation of the flexible beam; the computational efficiency of finite element method is the lowest, and Bezier interpolation method is the highest; the calculation accuracy of the assumed mode method is lower than the Bezier interpolation method.
Abstract: Combining the finite element method and the analytical method, a hybrid finite element-analytical approach is established to calculate the nonlinear dynamic responses of a micro-resonator driven by electrostatic combs accurately for the purpose of programmed dynamical simulations and great shortening of workloads. The spatially discretized equations obtained by using the analytical undamped global mode functions to the nonlinear integro-partial differential equations and the ordinary differential equations of the micro-resonator, in which the coefficients are estimated by the discrete global mode shapes from the finite element method, are used to calculate the nonlinear dynamic responses of the micro-resonator. The results are compared with those merely based on the analytical mode functions of the micro-resonator, which shows that they can reach high accuracy when the elements in the micro-resonator are sufficiently small.
Abstract: Considering the characteristics of an aero-engine whose main rotor, as an asymmetric structure, operating in a non-uniform temperature environment, a new dynamical modal of shaft is established for axial displacement analysis based on temperature internal force of non-uniform temperature field. The influence of non-uniform temperature field and the temperature changing are quantified. Based on the influence of temperature internal forces, the analytical formulae of axial displacement of a specified point in the shaft under a continuous temperature field and a discretized temperature field are derived, respectively. At last, the acceleration warming formula is used to simulate the warming up and stable time period, and its variation regularity is compared and analyzed. The relationship between strains of rotor main shaft and temperature internal forces are obtained through the new model and its analytical formulae. Furthermore, the feasibility and relevance of the new model are verified by an equivalent conclusion.
Abstract: The high speed machine tool spindle plays an important role in machining operations. Based on modal test techniques and rotating machinery signature techniques, the research focused on the test and analysis of the dynamic characteristics of spindle system of high speed grinder. First, an experimental modal analysis (EMA) is performed in the spindle system; then, the frequency response characteristics and the FRFs of the system should be considered. Furthermore, rotating machinery signature techniques are used to analyze the dynamic behavior of the spindle system in process due to the limitation of modal test techniques, and the theoretical proof is given to explain the spindle system order. The results show that it requires the machine tool to avoid the use of vibration-sensitive speed in the production process and the machine production process, especially bearing manufacturing to improve its accuracy.
Abstract: Hysteresis is a particular feature of a wide range of physical systems and devices such as electromagnetic fields, mechanical stress–strain elements and electronic relay circuits. The extended Bouc-Wen model is one of the most widely used hysteresis models in mechanics. It has the capability to emulate the behavior of a wide class of hysteretic systems. However multi parameters have plagued its further application because the capability of computer and algorithm available currently can not meet the need completely. Thus to exploit an effective parallel algorithm is very essential. This paper is committed to propose a novel Genetic Algorithm (GA) so as to identify the parameters of the Bouc-Wen model with noise disturbance efficiently and accurately. Finally a large amount of noise-involved experimental data obtained from a real MR damper is employed to verify the proposed approach has the capability to estimate the satisfactory parameters of the Bouc-Wen model. Also suggested are the implications of the present study on other nonlinear hysteretic models or other complex mathematical models.
Abstract: Increasing sophistication of naval shipboard machinery coupled with increasing competition for skilled manpower and tightening of defense budgets is forcing the Navy to consider alternative maintenance concepts. This paper proposes a health assessment process in condition-based maintenance architecture based on variable weight fuzzy comprehensive evaluation method. Through analyzing the variables affecting on warship electromechnical equipment condition, a layered assessment index system for warship electromechnical equipment health assessment is built. First, the AHP method is used to determine the constant weight of every index, and then the variable weight model is introduced based on balanced function, in which the constant weight is modified to get the variable weights. By comparing the fuzzy synthetic evaluation based on constant weights with that based on variable weighs, the results show that, the latter is more reasonable and objective, and is also more close to the actual condition of warship electromechnical equipment.
Abstract: According to the statistical data offered by US Bureau of Mines, belt conveyor fires account for about 20 percent of the mine fires Technologies on belt conveyor fire-monitoring system have drawn the attention from both scientific research institutions and manufacturing corporations. However, most methods and techniques available for monitoring the belt conveyor fire in mines are still not satisfactory. This paper presents a set of new methods and techniques for monitoring and forecasting the mine belt conveyor fire, and introduces a new practical system which is developed on the basis of them, including the design and installation of transducers, the design of conversion circuits, the design of monitoring and fault diagnosis software. Industrial applications as well as laboratory experiments have proved that this system is characterized by its simplicity in structure, convenience in installation, reliability in performance and strong environment adaptability, etc.
Abstract: With the development of aeroengine towards the direction of high speed and high performance, the clearance between rotor and stator in aerongine is reduced so that the possibility of rub-impact fault is increased. Since rub-impact signals often exhibits non-stationarity, an integrated approach, which combines the wavelet packet transform (WPT) with local discriminate bases (LDB), is presented in this study to diagnose the rub-impact faults. Specifically, the LDB algorithm is used to select an optimal set of orthogonal time-frequency subspaces resulted from WPT, which have the best discriminatory information for aeroengine rub-impact fault classification. Then the desired parameters generated by the LDB vectors were taken as input to a Bayes classifier for identifying rub-impact faults. Experimental results from the aeroengine vibration signals show that the fault diagnosis method can classify working conditions and fault patterns effectively.
Abstract: Shock and vibration response is a particularly important signal to characterize the system state. This paper analyzes the reason of fault generated high speed machine, vibration response mechanism and its frequency characteristic. According to the measured vibration signals, done time and frequency domain features analysis, wavelet packet analysis and frequency domain energy analysis, put forward a kind of fault comprehensive diagnosis method with accurate and rapid identification characteristics, can adapt to the complex vibration response signal with interference and low signal to noise ratio.