Fluid Limit For Cumulative Idle Time In Multiphase Queues

The object of this research in the queueing theory is the Functional-Strong-Law-of-Large-Numbers (FSLLN) under the conditions of heavy traffic in Multiphase Queueing Systems (MQS). A FSLLN is known as fluid limit or fluid approximation. In this paper, the FSLLN is proved for values of important probabilistic characteristic of the MQS investigated as well as the cumulative idle time of a customer

Trajectory planning method of rotating mobile piezorobot

This paper presents method of trajectory planning of mobile piezorobots. An algorithm is introduced to evaluate motional trajectory for this kind of robots that describe point-to-point motion by given function. Preliminary experimental results prove the feasibility of proposed mathematical mode

Formation of structural matrices for finite elements of piezoceramic structures

This paper deals with the description of a theoretical background of systematic computer algebra methods for the formation of structural matrices of piezoceramic finite elements. Piezoceramic actuators are widely used for high-precision mechanical systems such as positioning devices, manipulating systems, control equipment, etc. In this paper, the efficiency of computer algebra application was compared with the numerical integration methods of formation of the structural matrices of the finite elements. Two popular finite elements are discussed for modeling piezoceramic actuators: sector type and the triangular one. All structural matrices of the elements were derived using the computer algebra technique with the following automatic program code generation. Due to smaller floating point operations, the computer time economy is followed by an increased accuracy of computations, which is the most important gain achieved in many cases

Computer algebra for solving dynamics problems of piezoelectric robots with large number of joints

The application of general control theory to complex mechanical systems represents an extremely difficult problem. If industrial piezoelectric robots have large number of joints, development of new control algorithms is unavoidable in order to achieve high positioning accuracy. The efficiency of computer algebra application was compared with the most popular methods of forming the dynamic equations of robots in real time. To this end, a computer algebra system VIBRAN was used. Expressions for the generalized inertia matrix of the robots have been derived by means of the computer algebra technique with the following automatic program code generation. As shown in the paper, such application could drastically reduce the number of floating point product operations that are required for efficient numerical simulation of piezoelectric robots

New linear piezoelectric actuator based on traveling wave

A novel design of linear type piezoelectric actuator is proposed and analyzed in the paper. Actuator has a beam shape with cut-out hole. Traveling wave is generated on the top area of the actuator applying harmonic oscillations on the ends of the beam. These oscillations are generated by two piezoceramic elements and transferred to the ends of the beam. Electrodes of piezoceramic elements are excited by harmonic voltage with phase difference of ?/2. Numerical modeling based on finite element method was performed to find resonant frequencies and modal shapes of the actuator and to calculate the trajectories of contact point movements under different excitation schemes. A prototype of the piezoelectric actuator was built and measurements of top surface oscillations were performed. Results of numerical and experimental studies are discusse

Numerical study of cantilevers with non-uniform width for enhancing the performance of vibration-driven micropower generator based on piezoelectric conversion

This study is dedicated to investigation of rectangular- and trapezoidal-shaped cantilevers for achieving improved efficiency of the piezoelectric micropower generation. The developed finite element model of a unimorph piezotransducer with a proof-mass at the tip is used to examine how different cantilever shapes and proof-mass dimensions influence stress distribution, dynamic response and voltage output of the microgenerator. Numerical results indicate that cantilevers with increasingly triangular shape permit markedly larger kinematic excitation magnitudes and generate slightly larger voltages for a comparable deflection level

Miniature rotary tables with piezoelectric hemispheres: research and development

The aim of this research is to develop and investigate two modifications of high resolution miniature rotary tables, based on the transformation of 3D resonant oscillations of hemisphere actuators into continuous or start-stop motion of contacting rotary table. To generate 3D resonant oscillations of the contacting points, the electrodes of the actuators are sectioned into several parts, enabling the generation of traveling wave type higher forms of oscillations. The results of modeling of hemisphere actuators are presented together with experimental investigation of resolution and response time. It is shown that axial oscillations of the table and its torsional oscillations can be generated, extending the functionality of the devices

Development of two modifications of piezoelectric high resolution rotary table

The aim of this paper is to describe two modifications of high resolution rotary tables with angular position control, based on the transformation of resonant oscillations of piezoelectric transducers into continuous or start-stop motion. Exact angular position of the table is achieved by application of integrated classical rotary position encoders and feedback system, related to the given position or angular velocity of the device. Dimensions and cost of the table should be dramatically reduced, thus ensuring competitiveness in modern markets

Multiphysical modeling of a contact-type piezotransducer for the analysis of micro-energy harvesting from ambient vibrations

The paper presents development of a coupled-field finite element model of a contact-type piezoelectric transducer, which acts as a micropower source for MEMS sensors by harvesting energy from ambient vibrations. The proposed FE model of the cantilever-type piezotransducer couples three different physical domains: mechanical, piezoelectrical and fluidic. Both linear and nonlinear piezoelectric models are implemented. The fluid-structure interaction is modeled as viscous air damping, which manifests in the form of squeeze-film damping governed by the nonlinear compressible isothermal Reynolds equation. Vibro-impact interaction is modeled through implementation of a special adhesive-repulsive contact model that is suitable for contact simulations at the micro-scale. Performance of the FE model is demonstrated by representative dynamic simulations including parametric studies that reveal the influence of structural, excitation and ambient pressure parameters on dynamical and electrical performance of the device

Design and dynamic modeling of piezoelectric laser beam shutters

The paper presents the results of numerical modelling and experiments of piezoelectric bimorph-type bending actuator for laser beam shutting system. Theoretical calculations are realized by using finite element method. The purpose of these calculations is to optimize geometric parameters of a piezoelectric bimorph, ensuring maximum resonant frequency of the first bending form and stability of oscillation amplitude. Experimental performance of piezoelectric actuators is compared with results of finite element simulations