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Key Problems in Microforming Processes of Microparts
Chunju WANG,Debin SHAN,Bin GUO,Jian ZHOU,Lining SUN,

材料科学技术学报 , 2007,
Abstract: From the viewpoint of production engineering, microforming is considered as an effective process to fabricate various microparts. Several key problems in microforming processes were investigated. A new microforming apparatus with a high stiffness piezoelectric actuator as the punch driver was developed to produce microparts.To improve the forming abilities and locate the billets, a floating microdie was designed. The size effects of the billets and die cavities on the microforming abilities were studied with upsetting and coining tests, respectively.And the isothermal microforming process of microgears was performed with the developed microforming apparatus. Several analysis methods were used to evaluate the forming quality of the microparts.
В. Макаренко
Proceedings of National Aviation University , 2012,
Abstract: In the article the control system is created, which is able to reduce steady-state vibration response of thinwalled flexible structure in the wide band of low frequencies. It is supposed, that the flexible structure is subject to external harmonic force with variable frequencies, and parameters of that force are available for the usage by the control system. The control system is based on pattern search algorithm and suggestion about the dependence of signal, which is formed by the control system, from the steady-state vibration response of the flexible structure. Developed software allows to use pattern search algorithm as the control system for plate vibration in real-time. The influence on control system operation of signal delay of executive device of compensating path and transition process after the change of control signal parameters is done by the usage of the additional idle time. During idle time the control signal is supported. It has parameters that have taken place before the beginning of idle mode. Step reset option for resuming of search after the long-term steady-state vibration of flexible structure do not derange control system operation, because step change take place only after polling cycle termination. The efficiency of proposed system is illustrated experimentally on the example of clamped plate. Experimental results analysis showed the necessity of multiple compensating devices application for vibration reduction in wide frequency range. Розглянуто синтезовану систему керування, яка здатна зменшувати сталу в брац йнув дпов дь тонкост нно гнучко конструкц в широк й смуз низьких частот. Показано, що воснов алгоритму шаблонного пошуку лежить припущення про наявн сть зв’язку м жсигналом, що утворю ться системою керування та усталеною в брац йною в дпов ддюгнучко конструкц . Ефективн сть запропоновано системи керування про люстрованоекспериментально на приклад затиснуто пластини.Ключов слова: в брац я, гнучка конструкц я, система керув
Vibration Adaptive Control of the Flexible Lunar Regolith Sampler
Wei LU,Hong ZENG,Ai-guo SONG,Wei-min DING
TELKOMNIKA : Indonesian Journal of Electrical Engineering , 2012, DOI: 10.11591/telkomnika.v10i8.1628
Abstract: With respect to the problem of big volume, large weight and high power consumption of lunar sampler nowadays, the paper firstly described a novel flexible mini lunar regolith sampler. Then the vibration model of it is established while drilling. The drilling efficiency can be improved more effectively by controlling the lunar regolith sampler always in the resonance state. But the dynamical modeling of the sampler-regolith system is difficult to obtain and time varies when the sampler is in different depth in the lunar regolith. So we present a method of the vibration frequency fuzzy adaptive control based on the dynamic prediction by using the Levenberg-Marquardt Back Propagation (LMBP) neural networks. The LMBP with a FIR filter in series is used to predict the resonant frequency dynamically. And the fuzzy adaptive control is used to calculate the sweeping frequency bandwidth with the input of the amplitude and variation. The simul
Mathematical modeling of mechanical vibration assisted conductivity imaging  [PDF]
Habib Ammari,Eunjung Lee,Hyeuknam Kwon,Jin Keun Seo,Eung Je Woo
Physics , 2014,
Abstract: This paper aims at mathematically modeling a new multi-physics conductivity imaging system incorporating mechanical vibrations simultaneously applied to an imaging object together with current injections. We perturb the internal conductivity distribution by applying time-harmonic mechanical vibrations on the boundary. This enhances the effects of any conductivity discontinuity on the induced internal current density distribution. Unlike other conductivity contrast enhancing frameworks, it does not require a prior knowledge of a reference data. In this paper, we provide a mathematical framework for this novel imaging modality. As an application of the vibration-assisted impedance imaging framework, we propose a new breast image reconstruction method in electrical impedance tomography (EIT). As its another application, we investigate a conductivity anomaly detection problem and provide an efficient location search algorithm. We show both analytically and numerically that the applied mechanical vibration increases the data sensitivity to the conductivity contrast and enhances the quality of reconstructed images and anomaly detection results. For numerous applications in impedance imaging, the proposed multi-physics method opens a new difference imaging area called the vibration-difference imaging, which can augment the time-difference and also frequency-difference imaging methods for sensitivity improvements.
Active Vibration Control of Satellite Flexible Structures during Attitude Maneuvers  [cached]
Saeed Hemmati,Morteza Shahravi,Keramat Malekzadeh
Research Journal of Applied Sciences, Engineering and Technology , 2013,
Abstract: The purpose of this study is controlling active vibration of satellite flexible structures during attitude maneuvers. A smart structure is a structure which is able to sense and control active reaction to any external factors and stimulation. As it comes from the definition of smart structures, development of this knowledge depends on the materials science development, theories and strategies for control. In materials science, smart materials are developed in such a way that they are able to sense and react in a controllable mode effectively. The smart materials are combined with conventional structures and they are used as sensors and actuators. Furthermore, smart structures subject include design, implementation methods and control systems over structures so that the control system receives signals from sensors after processing. Then, it sends signals to the actuator in order to achieve a desirable response to incoming stimuli. An issue taken into account in this monograph is active vibration control of satellite flexible structures in attitude maneuvers, which was done by the use of smart materials in satellite structure. For this purpose, a mathematical model of a satellite flexible panel was derived first. Then, a computer code was generated. Finally, by comparing the results of non-smart control and smart control, we came to this conclusion that the use of smart materials led to a decrease in the amplitude of the vibration and the reduction of the time required for damping vibrations.
The Comparative Study of Vibration Control of Flexible Structure Using Smart Materials  [PDF]
Juntao Fei,Yunmei Fang,Chunyan Yan
Mathematical Problems in Engineering , 2010, DOI: 10.1155/2010/768256
Abstract: Considerable attention has been devoted to active vibration control using intelligent materials as PZT actuators. This paper presents results on active control schemes for vibration suppression of flexible steel cantilever beam with bonded piezoelectric actuators. The PZT patches are surface bonded near the fixed end of flexible steel cantilever beam. The dynamic model of the flexible steel cantilever beam is derived. Active vibration control methods: optimal PID control, strain rate feedback control (SRF), and positive position feedback control (PPF) are investigated and implemented using xPC Target real-time system. Experimental results demonstrate that the SRF and PPF controls have better performance in suppressing the vibration of cantilever steel beam than the optimal PID control. 1. Introduction Actuators from piezoceramic materials have wide application ranging from active vibration control to nanoscale positioning tasks. This is due to their high-frequency response behavior and essentially infinite resolution. Because piezoelectric ceramic materials have mechanical simplicity, small volume, light weight, large useful bandwidth, efficient conversion between electrical energy and mechanical energy, and easy integration with various metallic and composite structures, smart structures with surface-mounted or embedded piezoelectric ceramic patches have received much attention in vibration control of structures in recent years. Within the last two decades, much attention has been focused on active control of structures to suppress their structural vibrations. Active control methods can be used to damp out undesirable structural vibrations. Strain rate feedback (SRF) control is used for active damping of a flexible space structure by Newman [1]. Crawley and de Luis [2] proposed piezoelectric materials to be built in laminated beams. Fanson and Caughey [3] carried out feedback control to suppress structural vibration with segmented piezoelectric actuators and sensors. Positive position feedback (PPF) [4–7] is applied by feeding the structural position coordinate directly to the compensator, and the product of the compensator and a scalar gain positively back to the structure. The model derivation for a vibrating beam is described in many texts. Choi and Lee [8] presented the derivation for the modeling of a beam with a piezoceramic actuator affixed near the base. Many approximate models have been developed to predict the behavior of flexible beams incorporating PZT actuators [9–11]. Adaptive sliding model controller with sliding mode compensator has
System identification and active vibration control of a flexible structure
Abreu, Gustavo Luiz C. M. de;Concei??o, Sanderson M. da;Lopes Jr., Vicente;Brennan, Michael John;Alves, Marco Túlio Santana;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2012, DOI: 10.1590/S1678-58782012000500007
Abstract: the aim of this paper is to illustrate the active control of vibration of a flexible structure using a model-based digital controller. the state-space model of the system is derived using a system identification technique known as the observer/kalman filter identification (okid) method together with eigensystem realization algorithm (era). based on the measured response of the structure to a random input, an explicit state-space model of the equivalent linear system is determined. the model is used in a linear quadratic regulator (lqr) to control the first two modes of vibration of a cantilever beam using a piezoelectric actuator/sensor pair. experimental results demonstrate the efficacy of the proposed approach.
Attitude and Vibration Control of Flexible Spacecraft Using Singular Perturbation Approach  [PDF]
Morteza Shahravi,Milad Azimi
ISRN Aerospace Engineering , 2014, DOI: 10.1155/2014/163870
Abstract: This paper addresses a composite two-time-scale control system for simultaneous three-axis attitude maneuvering and elastic mode stabilization of flexible spacecraft. By choosing an appropriate time coordinates transformation system, the spacecraft dynamics can be divided into double time-scale subsystems using singular perturbation theory (SPT). Attitude and vibration control laws are successively designed by considering a time bandwidths separation between the oscillatory flexible parts motion describing a fast subsystem and rigid body attitude dynamics as a slow subsystem. A nonlinear quaternion feedback control, based on modified sliding mode (MSM), is chosen for attitude control design and a strain rate feedback (SRF) scheme is developed for suppression of vibrational modes. In the attitude control law, the modification to sliding manifold for slow subsystem ensures that the spacecraft follows the shortest possible path to the sliding manifold and highly reduces the switching action. Stability proof of the overall closed-loop system is given via Lyapunov analysis. The proposed design approach is demonstrated to combine excellent performance in the compensation of residual flexible vibrations for the fully nonlinear system under consideration, as well as computational simplicity. 1. Introduction In many missions of today’s spacecraft with high resolution earth observation payloads and/or large flexible systems, the operation plan requires high precision control capability in order to point at certain area of interest. These missions impose increasingly severe requirements over the modeling and control of spacecraft dynamics. However the flexible structural elements such as solar arrays, antennas, and other light weight parts have received significant focus on providing the control effort for targeting flexible parts such as payloads and tracking maneuver with simultaneous vibration suppression to accomplish mission objectives. Design of such control system poses a challenging problem, including spill-over effects due to the unmodeled dynamics, nonlinear characteristics of rigid-flexible fully coupled dynamics, and unexpected perturbations [1]. From the mathematical point of view, the dynamics of flexible spacecraft involves the coupling of ODEs for attitude dynamics and PDEs for vibration of flexible appendages. This represented by a set of hybrid differential equations (HDE) of motion. Therefore, control strategies have emerged for smoothly shaped maneuvers with vibration excited [2]. Also, the actual performance of controllers is highly sensitive
Vibration Suppression Techniques in Feedback Control Loop of a Flexible Robot Manipulator  [cached]
Mohd Ashraf Ahmad,Zaharuddin Mohamed
Modern Applied Science , 2009, DOI: 10.5539/mas.v2n2p59
Abstract: This paper presents the use of angular position control approaches for a flexible robot manipulator with disturbances effect in the dynamic system. Delayed Feedback Signal (DFS), Linear Quadratic Regulator (LQR) and Proportional-Derivative (PD) controller are the techniques used in this investigation to actively control the vibrations of flexible structure. A constrained planar single-link flexible manipulator is considered and the dynamic model of the system is derived using the assumed mode method. A complete analysis of simulation results for each technique is presented in time domain and frequency domain respectively. Performances of the controller are examined in terms of vibration suppression and disturbances cancellation. Finally, a comparative assessment of the impact of each controller on the system performance is presented and discussed.
A Neural Fuzzy System for Vibration Control in Flexible Structures  [PDF]
Xiaoxu Ji, Wilson Wang
Intelligent Control and Automation (ICA) , 2011, DOI: 10.4236/ica.2011.23031
Abstract: An adaptive neural fuzzy (NF) controller is developed in this paper for active vibration suppression in flexible structures. A recurrent identification network (RIN) is developed to adaptively identify system dynamics of the plant. A novel recurrent training (RT) technique is suggested to train the RIN so as to optimize nonlinear input-output mapping and to enhance convergence. The effectiveness of the developed controller and the related techniques has been verified experimentally corresponding to different control scenarios. Test results show that the proposed RIN can effectively recognize the time-varying dynamics of the plant. The RT-based hybrid training technique can improve the adaptive capability of the control system to accommodate different system conditions and enhance the training convergence. The developed NF controller is a robust and stable vibration suppression system, and it outperforms other related NF controllers.
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