Applied Mechanics and Materials Vols. 236-237

Abstract: This paper presents an automatic judgement method for wheelset press-fit curve, in which thirteen technical conditions are examined for qualified wheelset assembly or not. In order to meet the requirements of Criterion of inspection and repair - railway vehicles [2007]95, some algorithms are designed to identify several traits on press-fit curve, such as force zoom, force decrease, flat line, concave-up shape and so on. In accordance with the Criterion 95 and the algorithms, a quality judgement software attaching to the computer control system in a wheelset assembly machine is developed. The practical application shows that the software’s judgement accuracy is up to 99.4%. Compared with artificial approach, the accuracy, reliability and efficiency of the new judgement method all improve greatly. It also avoids influences of personal factors and makes great sense to the assurance of press-fit quality and transportation security.

Abstract: Material degradation is usually preceded by nonlinear ultrasonic, and higher harmonics will be generated. The project studied the method to improve the second harmonic signal to noise ratio with pulse-inversion technique. A finite element method model of nonlinear was established by a special element which account for a nonlinear stress-strain relation. Calculation was performed for the influence of the pulse-inversion technique to ultrasonic nonlinearity parameters. The simulation results show that the second harmonic signal to noise ratio is obviously improved. Measurement method of nonlinearity parameters and signal processing algorithms with pulse-inversion technique were established, and a robust experimental procedure was developed. Using this method, ultrasonic nonlinearity parameters of a group of LY12 aluminum samples stretched were measured. The experimental results show that the pulse-inversion technique is very efficient in extracting this second-harmonic amplitude by canceling out the odd harmonics which are mainly due to the instrumentation. Introduction

Abstract: Time grating is a novel displacement sensor with new principle which employs time to measure space. This sensor avoids relying on the precise mechanical spatial division technology to realize precise measurement which challenges the traditional view of measuring space by precise mechanical spatial division. Research on dynamic grey model for time grating applied for full closed loop numerical control rotary table instead of optical grating is presented. According to dynamic model, a next angular displacement of data series can be forecasted based on series of previous angular displacement value before corresponding sampling time comes. So forecasting incremental angular displacement can be converted into continuous pulses to sent out with PWM technology. Original absolute angular displacement signal sampled during equal time interval can be converted into incremental continuous pulses which enable time grating applied for numerical control system. As regard to error control, actual output incremental continuous pulses represent differentials between forecasting incremental angular displacement and forecast error of last measurement period. In this way, forecast error can be calibrated between neighbouring measurement periods, so cumulative errors can be eliminated. The accuracy of incremental type time grating signal can reach -2.8″~3.87″which proves dynamic model validity.

Abstract: In order to achieve the digital design of solid rocket motors, the MFC module of Visual Studio2010 is used for interface software programming in this paper. Beginning with the initial performance parameters, the software receives the input parameters and gives the results of grain design and its interior ballistic calculation. Given all the results, we can evaluate the performance of grain. The design cases show that the design results of the software are correct and reliable.

Abstract: The salient effect of the rotor structure of the interior permanent magnet synchronous machine (IPMSM) makes it more suitable for running in the zone that exceeds the rated revolution by flux-weakening control. Therefore, the closed-loop speed regulation system composed by IPMSM can achieve excellent dynamic performance, high precision and wide speed performance. On the basis of the mathematical model of d / q coordinates of IPMSM, this paper discusses the control proposal of IPMSM: to control the current of d / q axis to maximize the speed range.

Abstract: The medium frequency induction furnace power control system of industrial grade includes the microcontroller STC89C52RC, power converters, data amplifiers, analog to digital converter, stepper motor and excitation regulator, etc. The medium frequency generator’s output voltage and current signals are passed to the power converter to transform the millivolt DC signal into a linear relationship. The outputs from the power amplifier controlled by the data conversion single-chip are input through the ADC. The signals are compared with the power base value set by the user to calculate the control commands, to control the stepper motor action and control the stepper motor to forward or reverse, as well as to adjust the excitation current. Therefore, the medium frequency generator output power is stable. The heating temperature of the work pieces are precise controlled. A detailed description of the system's hardware and software composition and design methods are illustrated in this paper.

Abstract: The bias derivative method for aeroengine’s State Variable Model(SVM) doesn’t have a satisfying accuracy. This method usually needs a linear modification to achieve a higher accuracy. In order to obtain a SVM with a good accuracy, this paper proposes a process identification based method. In this method, the coefficient matrices of the SVM are identified based on the input and output of the nonlinear model, according to the principle that the step responses of the SVM and the nonlinear model should be consistent. Then, the SVMs of small perturbation about steady operating points of an engine are established. Simulation results show that the SVMs established by the process identification based method have a good fidelity both in terms of steady and dynamic performance.

Abstract: In electric vehicle management system, the key technology is to estimate the SOC (state of charge) of battery in dynamic process. This paper builds the state space equation of lithium battery based on improved Randle’s model, realizes the tracking estimation of SOC using modified STF(strong tracking filter) algorithm. The simulation result proves that compared with the original algorithm, modified algorithm can greatly improve the system’s tracking ability as well as the estimation accuracy of SOC.

Abstract: Papers on cantilever piezoelectric resonators experiment research in the low frequency vibration environment. The study proved that, to choose a proper mass can effectively regulate the cantilever piezoelectric vibrators natural frequency The more close to the incentive frequency and the natural frequency of piezoelectric vibrators, the better the results of piezoelectric vibrators power generation.

Abstract: Traditional Static Synchronous Compensator(STATCOM ) compensates most singly for reactive power or steady state voltage in high power field. On this point, the paper puts forward a harmonic frequency compensation technique, which can realize dynamic reactive power compensation as well as harmonic control of less than 20th power. Then, using average switching method, it gives the mathematical model on the device. Active and reactive current decoupling is realized. For the electrical model, the compensator developed uses 8-cascaded H bridge structure, together with the carrier phase-shifted SVM technology, can realize 17 level voltage waveform output, having high utilization and easy to realize digital. Finally, simulation and experimental results show that the harmonic frequency control technology developed for 6kV cascade compensator can be used on the actual electric network, with low switching frequency. The device can together compensate reactive power and control harmonic accurately and effectively.