Applied Mechanics and Materials Vols. 130-134

Abstract: In this paper, a remote real-time online rotating machinery monitoring system, which was developed and tested in the Industrial application, is presented including its remote monitoring sub-system, fault diagnosis sub-system. First, the system architecture is introduced. Next, a web-based remote monitoring system is designed, which allows researches and engineers to remotely monitor the health of the machine from any remote geographic location through the Internet. Finally, the holographic spectrum technology in this system is discussed as well for the purpose of providing accurate and reliable diagnosis of the machine states and accident prevention.

Abstract: This paper presents a brushless DC (BLDC) motor drive with direct torque control (DTC).The detailed hardware and software design are analyzed and designed. The performance of the BLDC employing DTC is compared with that of BLDC utilizing PWM current control. A prototype of BLDC motor drive based on the DSP controller with DTC control is implemented and validated by the exhibition of waveforms measurement for currents, torque, flux linkage, and speed. The experimental results not only verify the feasibility of designed system but also demonstrate that BLDC with DTC control has superior characteristics than that with PWM current control.

Abstract: Giant magnetostrictive actuator (GMA) has advantages over other actuator made of intelligent materials in aspects like quick response, large output force, and high precision. But the lack of displacement, relatively big size and heavy weight block its popularization. In this paper, a new mini linear motor based on three GMAs is designed. It is the second generation motor derived from the improvement of the first generation linear motor that is realized in our previous work. To compensate the structural defects and to improve the traveling performance of the previous one, we redesign the motor in the structure, especially the frame as a whole by considering not only the basic supporting and connecting role but also the displacement amplifying function in it. The paper presents the process of the structural design of the mini linear motor, the establishment of the motor’s system dynamic model and the traveling simulation under SIMULINK. The new structural scheme and the motor’s system modeling approach are validated by the simulation results. Keywords: magnetostrictive; inchworm linear motor; structural design; dynamic modeling

Abstract: This paper proposes a low voltage ride through (LVRT) scheme of doubly fed induction generator (DFIG) based on the supercapacitors energy storage. The novel control strategy of the bi-directional converter and the grid side converter is established. Simulation model of the DFIG system is developed. Simulation results show that the presented scheme can efficiently reduce the DC-link overvoltage, supply reactive power to the power system through grid side converter, and help grid recovery under system fault, improving the LVRT capability of the system.

Abstract: On the basis of intensive study on the characteristics of structure and standards of wind turbine pitch bearing, the paper established the parameters level model of pitch bearing, analyzed the vague relationship between the size of pitch bearing and the capacity of wind turbine and determined the main design parameters of pitch bearing. Via combining open parametric method for part family and parameter-driven technology, this paper also developed a faster design support system of pitch bearing of wind turbine, which effectively cut down repetitive design work and improved the efficiency of design and the reliability of pitch bearing.

Abstract: Based on conventional drive train model of wind turbines, a planetary gearbox with flexible supporting between gearbox case and nacelle base is considered, and the coupled dynamic model of the drive train system is derived. The gearbox inner vibration performances are evaluated under different flexible parameters by means of dynamic simulation. It is shown that natural frequencies of each shaft are drifting while damping and elastic coefficients changing. Analysis also reveals that the flexible supporting mitigates torsion vibrations of each shaft. To minimizing torsion vibrations, a new searching approach is used to find out optimal parameters of the flexible supporting. Simulation results show that dynamic torque loads of the drive train are reduced, which is useful to wind turbine structure design.

Abstract: The ordinary differential equations coupling electromagnetic force of dynamics were established for split Stirling engine. The transient displacement vectors of the two pistons were disposed of feedback vectors in numerical computation models of Matlab/Simulink computing environment. Since the total mass of the working fluid remains constant, the instantaneous cyc-pressure was computated by the characteristic gas equation. The differential pressure vector of the expansion space between the compression space was computated by the flow loss in the regenerator. The instantaneous current of generator winding was computated by the balance equation of motional electromotive force. The displacement wave forms was contrast to the expansion piston and the compression piston. In addition, one of the necessary conditions of steady operation was reduced by oscillation theory for split Stirling engine.

Abstract: This study is carried out to characterize the size distribution of exhaust particulate from gasoline engine. Accordingto the results,particulate number concentrations show bimodal size distribution including nucleation and accumulation mode below the range of 50nm in coldstarting. While in hot start state, number concentration with bimodal size distribution different from coldstarting are less than 40nm in size.The distribution of particulate number,surface area and particulate mass characterized by nucleation and accumulation distribution mode goes below 40nm,and the trends go up with the increase of engine speed.

Abstract: Conventional single closed-loop system of DC motor with speed-feedback has poor performance when some stochastic disturbances take place. To handle this shortcoming, the control system with full-state feedback and integral output feedback of DC motor is proposed. The state-space model of the full-state feedback of DC motors is established. The feedback gains of the control system are optimized by Particle Swarm Optimization algorithms based the simulation model. The simulation results show that the control system with full-state feedback of DC motors has better dynamic performance.

Abstract: The objective of this paper is to predict the flaw response in an inhomogeneous solid medium. Multi-Gaussian Beam (MGB) model is used to represent the incident ultrasonic beam. The effect of ultrasonic attenuation and phase velocity dispersion due to grain scattering is included in the predictions. The effect of variation of mean diameter of the grains on the received voltage for different domain of interest is studied through the experimental results.