Advanced Materials Research Vols. 383-390

Abstract: A vibration reducing system of seismic isolation bearings is introduced into beam string structures. The vibration control on seismic response of beam string structures (BSS) with seismic isolation bearings is discussed. Firstly finite element models for different analyses are established by using explicit dynamic analysis program LS-DYNA. Then the seismic response analyses are performed on a single beam string structure with and without seismic isolation bearings to investigate the effectiveness of the seismic isolation bearings in reducing vibration response of BSS. Furthermore, parametric analyses are conducted to examine the effects of lateral stiffness and damping of the seismic isolation bearings on seismic isolation. The analytical results indicate that the vibration reducing system can effectively reduce the vibration response of BSS against seismic force, and be applied in the vibration control of BSS.

Abstract: In order to ensure that small diameter steel pipes with thick wall have high intensity and high quality, ultrasonic immersion method with focusing probe was used to detect the flaw of the small-diameter steel pipes with thick wall. In practice, the echoes are often corrupted with external noise or internal noise, therefore, it is necessary to reduce the noise and to enhance the SNR of ultrasonic signals. A technique for improving the SNR of ultrasonic signals using wavelet transform is presented. In this method, WT, consider as one band-pass filter, is used to remove the noises. The performance of this technique has been verified by experimental, which is done by using a series of flaw ultrasonic echoes obtained from a specimen of the small-diameter steel pipes with thick wall. In particular we have found the processing of the ultrasonic signals using wavelet transform extremely useful for noise reduction. After processing, the SNR of ultrasonic signals are enhanced substantially. All experimental results show that this technique is effective for removing the white noise from the ultrasonic signals.

Abstract: In order to eliminate the friction force of linear motor nc machine tool feed system and improve the machining precision, a new Self Magnetic-Suspension Permanent Magnet Linear Synchronous Motor(PMLSM)is putted forward in this paper, which can generate the suspending power by itself. In this paper, the magnetic field distribution is calculated by means of equivalent magnetizing current and Schwarz-christoffel transformation, and is further analyzed and verified by using Finite Element Method. Furthermore, the method of optimizating the length of the primary iron-cored is adopted to design the motor. The experimental results shows that self magnetic suspension -PMLSM can generate thrust and suspending force separately, and the thrust and suspending force are improved by applying optimized method.

Abstract: Good dynamic performance of a system have great significance in the traditional sense, furthermore,it is more important at the point of energy saving. Particle swarm optimization (PSO) is a novel evolutionary algorithm which has a better convergence rate and computation precision compared with other evolutionary algorithms. In this paper an optimal design of PID controller based on particle swarm optimization approach for temperature control in HVAC is presented. The results show the adjustment of PID parameters converting into the optimal point and the good control response based on the optimal values by the PSO technique, and thus it achieves the purpose of energy savings.

Abstract: Five-axis turning-milling center is an important and advanced NC machine in fields of military industry, aerospace, automobile and medical machinery. The kinematics equation is built based on D-H method by the analysis of the structure of five-axis turning-milling center. The precision workspace is presented and its definition is given. The precision workspace of five-axis turning-milling center is analyzed based on Monte Carlo method. The mathematical model of precision reliability for machining center is built. The sensitivity of precision reliability for machining center is analyzed using analytical method. Finally, sensitivity histograms are given.

Abstract: Based on orthogonal design, a four factors and four levels experimental scheme were made. On a special test platform, under different heat transferring conditions, temperature fields of cylinder head were obtained. Results showed: among the four kinds of factors, the temperature of coolant water in jacket had serious influence on cylinder head, second was the heating temperature in chamber, third was the flow of coolant water in jacket, the last was surrounding temperature, which can give a gist for further optimizing cooling system of engine.

Abstract: Kernel principal component analysis (KPCA) is presented and is applied to predict the huge electro-mechanical system fault. Take the gas turbine set of Beijing Yanshan Petrochemical Refinery as the research object. KPCA uses the historical normal data of vibration intensity value to establish a prediction system. And then it is used to forecast the collected data for judging whether the turbine set is in normal. The simulation experiment result indicates the effectiveness of the method and the running state can be judged as normal or not from the result. And the experiment also shows KPCA can obtain a satisfactory prediction result.

Abstract: Subsynchronous Oscillation problems caused by HVDC system are studied and analyzed intensively in this paper based on eigenvalue analysis method. By establishing the small signal linearized model of a typical HVDC system, subsynchronous oscillation characteristics of the system with or without SSDC are obtained. Further more, the influence of SSDC parameters to the system subsynchronous oscillation characteristic can be illustrated clearly. This is significant for SSDC design in order to achieve a satisfied restraining effect. Comparing with more accurate electromagnetic transient simulation results, the consistency of the two methods is verified and it can be demonstrated that eigenvalue analysis method is adequate for studying subsynchronous oscillations.

Abstract: The method based on the theory of Fuzzy Pattern Recognition is divided into three parts. Firstly, use Hough transformation to extract the feature points of vehicles, and use the ratio between two absolute distance of adjacent feature points as the characteristic values of vehicles; secondly, use Fuzzy C-mean Classification to handle feature data of 75 car model, then establish a degree of membership matrix as the sample space; thirdly, consider the classification algorithm based on fuzzy approach degree and the credibility of the vehicle feature to propose a weighted close- degree recognition algorithm. This recognition method has a good effect.

Abstract: A new permanent magnet bias axial magnetic bearing (PMAB) is introduced, then the structure and operation principle are analyzed. The equivalent magnetic circuit is established to deduce the mathematic expression. The parameter design and calculation of the magnetic bearing are presented including available area of magnetic pole, ampere - turns of control coils etc. The parameters of the proposed prototype are also given. The 3-D magnetic field simulation is performed by using the Finite Element software. The theory analysis and the simulation show that the maximum suspension magnetic force satisfies the design requirement. The magnetic suspension forces have better linearity and symmetry around the balanced position. Therefore, the proposed PMAB is suitable for the high speed or low loss occasions.