摘要 :
The rapid development of aerospace, automobile, national defense and other manufacturing industries has continuously improved the performance requirements of high speed and high positioning accuracy of the CNC machine tool feed sy...
展开
The rapid development of aerospace, automobile, national defense and other manufacturing industries has continuously improved the performance requirements of high speed and high positioning accuracy of the CNC machine tool feed system. As the thermal deformation error increases, the system structural rigidity decreases, the vibration increases, and accuracy of machine tool reduces. Existing research mainly focuses on the properties of mechanical and single thermal feed system, and less considers the dynamic performance under the action of thermal-mechanical coupling. For the improvement of feed system performance, it is very beneficiary. This paper takes the high-speed tool of CNC feed system as objective, combined with the actual working conditions to analyze the thermal characteristics, dynamic characteristics and vibration characteristics of the system under the effect of thermal-mechanical coupling. The thermal resistance and convective heat transfer of the key joint surface, the application of moving thermal loads, and the establishment of a simulation model to complete the steady-state temperature field, transient temperature field and thermal-structure coupling analysis. The results show that the maximum temperature rise of the feed system is 21.08 °C, The maximum thermal deformation is 17.264 um. The study found that the parameters such as flow rate and airflow temperature have a significant impact on the cooling effect, so the cooling device was further optimized. This paper proposes a control method for cutting chatter of CNC machine tools based on coupling of characteristics of thermal and mechanical. The thermal characteristic of the feed system and the thermal-mechanical coupling vibration characteristic test provides the maximum temperature error of 3.2 %, verifying the correctness of the theoretical method and analysis model. The highest temperature obtained by the test is 39.7 °C, indicating that the high-speed feed system has a large thermal effect. The relative error of the vibration amplitude of the test and simulation is 12.5 %, which verifies coupling in terms of thermal-mechanical. The accuracy of the vibration analysis method; the experiment depicts that the vibration amplitude increases by 19.7 % under the coupling effect of thermal and mechanical, indicating the effectiveness of dynamic characteristics of the high-speed feed system considering the thermal-mechanical coupling effect.
收起
摘要 :
The dimensional accuracy of components obtained as a result of conventional or pulse ECM is affected by random, systematic and regularly varying errors. On the basis of experimental studies, the effect of control parameters such a...
展开
The dimensional accuracy of components obtained as a result of conventional or pulse ECM is affected by random, systematic and regularly varying errors. On the basis of experimental studies, the effect of control parameters such as operating voltage, electrolyte pressure, relative pulse duration, etc., on interelectrode gap size has been revealed, and the tasks of electromechanical machine adjustment and readjustment have been developed taking into account the influence of disturbing factors and dimension scatter range in a batch of components.
收起
摘要 :
Electromechanical direct drives represent ultimate simplification of the electromechanical conversion systems because of they permit removal of parts of transmission system : reduction and multiplier gears, rotating to linear move...
展开
Electromechanical direct drives represent ultimate simplification of the electromechanical conversion systems because of they permit removal of parts of transmission system : reduction and multiplier gears, rotating to linear movementtransformation... This simplification of the transmission system has always been used always in certain applications where mechanical requirements are adjust easily with classical motors (speed from about 1000 to 3000 rpm). But in very low speed and hightorque, very high speed as well as linear drives, establishment takes slowly. In this paper, we aim to give numerous application examples where direct drives exist or emerge. We recall too their specific constraints. Finally, we develop a specific chapter on feasibility limits of very high speed rotating electromagnetic motors.
收起
摘要 :
A space-phase method for the mathematical simulation of electromechanical energy transformation in electrical machines of rotational motion is proposed. Results of numerical experiments with two-dimensional space-phase models of a...
展开
A space-phase method for the mathematical simulation of electromechanical energy transformation in electrical machines of rotational motion is proposed. Results of numerical experiments with two-dimensional space-phase models of a reverse-design valve machine with constant magnets are presented.
收起
摘要 :
To identify the parameters of asynchronous machines, many methods are used. Many of them need a derivative during the optimization process. Unfortunately, a derivative function amplifies any noise due to numerical calculation or t...
展开
To identify the parameters of asynchronous machines, many methods are used. Many of them need a derivative during the optimization process. Unfortunately, a derivative function amplifies any noise due to numerical calculation or to measurement. As a consequence the search of the vector of parameters becomes difficult. Three minimization methods without derivatives are presented and applied to the identification of the parameters of induction motors. They allow finding both electrical and mechanical parameters from the analysis of the starting stator current and the corresponding voltage. Firstly, each method is described. Secondly, for a 'given machine with known parameters, numerical simulations allow to test the methods in terms of computer consuming time, of convergence and uniqueness of solution. The last part is devoted to the applications of the methods in order to identify the parameters of two asynchronous machines.
收起
摘要 :
In the paper dynamic electromechanical interaction between the rotating machine drive system and the electric driving motor is considered. The investigations are performed by means of the circuit model of the asynchronous motor as...
展开
In the paper dynamic electromechanical interaction between the rotating machine drive system and the electric driving motor is considered. The investigations are performed by means of the circuit model of the asynchronous motor as well as using an advanced structural hybrid model of the drive system. Using the analytical solutions applied for the electrical and the mechanical systems the electromagnetic stiffness and coefficient of damping, both generated by the electric motor rotationally interacting with the mechanical system of the given dynamic properties, were determined. By means of experimentally validated computational responses obtained for torsional harmonic excitation induced by the driven machine working tool, a modification of dynamic properties of the mechanical system by the electromagnetic flux between the stator and the rotor has been studied.
收起
摘要 :
Purpose - The purpose of this paper is to optimise the electro-discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes. Design/methodology/approach - In...
展开
Purpose - The purpose of this paper is to optimise the electro-discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes. Design/methodology/approach - In this paper the effects of discharge current, pulse-on-time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi-based L{sub}9 orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance. Findings - Experimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using DMLS electrode. Excessive DMLS tool (electrode) wear was also reported, which limits the use of DMLS tool for EDM machining and it has been found out that porosity (which was about 20 per cent) was one of the primary cause. Research limitations/implications - This paper was focused on understanding the effects of important EDM parameters on three performance characteristics (TWR, MRR and surface roughness). While this study identifies that DMLS electrode wear rate is high and porosity could be one of the main cause, presently it does not cover the investigations on reducing the porosity level and its implications. Practical implications - The DMLS material had shown huge potential to be used as EDM electrode. The current investigation established a structured experimental approach to understand the effects of EDM parameters on multi response characteristics. The results derived from this study helps to focus future research on two aspects including enriching the copper content and reducing the porosity level, thereby the benefits of lead time reduction in EDM electrode making could be realized. Originality/value - The previous research attempts were notfocussed on optimising the EDM machining process using rapid tooling electrodes. With the best of author's knowledge none of the researchers have reported these aspects especially for DMLS electrodes. Application of grey relational analysis for performance evaluation of rapid tooling-based EDM electrodes (DMLS electrodes) appear to be completely new.
收起
摘要 :
Purpose. To establish analytical expressions of machine constant and electromagnetic parameters for a specific circuit of the armature winding of an electromechanical converter of an inertial energy storage device, which is a DC e...
展开
Purpose. To establish analytical expressions of machine constant and electromagnetic parameters for a specific circuit of the armature winding of an electromechanical converter of an inertial energy storage device, which is a DC electric machine with a semiconductor switch and excitation from permanent magnets. Methodology. For research the theory of electrical circuits is used to create a mathematical model of the processes of electromechanical energy conversion in an inertial storage device. The plots method is used to find the mutual inductance of the armature winding coils, which are presented in the form of infinitely thin single-turn contours of rectangular shape, located in three-dimensional space. Results. Mathematical models of the processes of electromechanical energy conversion in an inertial storage device are obtained reflecting the relationship between the exchange energy and drive power with geometric and electrophysical parameters of both the energy accumulator and the system of its electromechanical converter. A connection of the parameters of machine constant, active and inductive resistances with the configuration, wiring diagram and the geometric dimensions of the armature winding has been established. The wiring of sections in the phase of the armature winding depends on the required value of the voltage and current of the machine. The possibility of regulating the voltage of the drive by switching on and off the working phases of the system of electromechanical converter, as well as by changing the angle of the load is shown. Originality. Mathematical models are obtained that relate the indicators of the energy of exchange and the power of the drive to the geometrical and electro physical parameters of both the energy accumulator and the system of its electromechanical converter. A feature of these models is operating with an average value of induction and machine constants when determining the electromotive force and electromagnetic moment. Practical value. Recommendations are developed for determining the machine constant and electromagnetic parameters of electromechanical inertial energy storage devices. This allows to evaluate the properties of devices of this type in the modes of storage and delivery of energy during their operation on board the rolling stock.
收起
摘要 :
While there are many works about the development of computers, there is surprisingly little that focuses on early initiatives in digital computing. This article describes and elaborates on some of the early developments in digital...
展开
While there are many works about the development of computers, there is surprisingly little that focuses on early initiatives in digital computing. This article describes and elaborates on some of the early developments in digital computing. The logical machine of W. Stanley Jevons, for instance, interested others. The most promising offshoot was the work of Allan Marquand, who conceived of an electromechanical digital machine as early as 1885. Marquand moved from mechanical to electromechanical devices. A similar progression occurred in subsequent, but unrelated work by Konrad Zuse, who also began by constructing a mechanical digital machine
收起
原文获取