Applied Mechanics and Materials Vols. 48-49

Abstract: A blind source separation (BSS) method base on second-order statistics was applied to separate the vibration mixtures based on the temporal structure of vibration signals. The single delay covariance matrix was used to compute the whiten matrix. A set of covariance matrices with different time delay was joint approximatively diagonalized to obtain their ‘average eigenstructure’. The separation of the real vibration mixtures from two motors illustrate that it is feasible to applied this method to the research of the health monitoring of the gearbox.

Abstract: Finite element method with experimental data was used to calculate and analysis the temperature field and machine assembly of a 150 engine cylinder liner. Using a series of evaluation criteria such as maximum, minimum radius, light leakage rate to analyze the influence of the main structural parameters on the cylinder liner deformation in the coupling effect of Thermal stress and mechanical stress. Comparative results show that: increasing the wall thickness of cylinder liner can reduce the radial deformation of the cylinder liner effectively, the diameter of the cylinder liner shroud has little effect on the cylinder liner radial deformation, but it can reduce the local stress concentration of the cylinder liner, cylinder shroud thickness increases can lead to the radial deformation of the cylinder liner increasing.

Abstract: The deregulation of power system brings a strong impact on all aspects of power industry, and especially the risk on the maintenance of system security. The problem is addressed and researched in this paper. Meanwhile, the paper presents a new price mechanism—security price, which is able to stimulate market participants to actively maintain system security. In addition, security price can also exert its economic leverage to alleviate the congestion of power network and the shortage of short-run capacity.

Abstract: For the multisensor Autoregressive Moving Average (ARMA) signals with unknown model parameters and noise variances, using the Recursive Instrumental Variable (RIV) algorithm, the correlation method and the Gevers-Wouters algorithm with dead band, the fused estimators of unknown model parameters and noise variances can be obtained. Then substituting them into optimal fusion signal filter weighted by scalars, a self-tuning distributed fusion Kalman filter is presented. Using the dynamic error system analysis (DESA) method, it is rigorously proved that the self-tuning fused Kalman signal filter converges to the optimal fused Kalman signal filter, so that it has asymptotic optimality. A simulation example shows its effectiveness.

Abstract: In order to learn gas flow state in the vacuum high pressure gas quenching furnace, this paper simulates and tests the gas flow under the no-loaded and cold state. Hot wire anemometer is used to measure the speeds of some feature points, on the one hand to provide boundary conditions for the numerical simulation, and on the other hand to compare with the numerical simulation results. FLUENT software is used to simulate the gas flow of nozzle-type vacuum high-pressure gas quenching furnace. The results show that at the center of the furnace appears high-pressure low-speed zone in which is resulted by the gas collision there, and the vortex also appears in the area around the furnace. The results mean that the cooling rate of works will be slow there. Different exit velocities of five nozzles cause the uneven flow distribution, which will affect the cooling uniformity of works. The comparison between the simulation results and the measured results shows that the error is within 10%. It means that numerical simulation method to predict gas flow is feasible and the results are reliable in high pressure gas quenching furnace.

Abstract: The stability and chaotic motions of a 3-D quadratic autonomous system with a four-wing chaotic attractor are investigated in this paper. Base on the linearization analysis, the stability of the equilibrium points is studied. By using the undetermined coefficient method, the heteroclinic orbits are found and the convergence of the series expansions of this type of orbits is proved. It analytically demonstrates that there exist heteroclinic orbits of Silnikov type connecting the equilibrium points. Therefore, Smale horseshoes and the horseshoe chaos occur for this system via the Silnikov criterion.

Abstract: Combine wavelet function “db10”with MATLAB band energy scale decomposition method, studied the characteristics of acoustic signals on different rubbing pair at low speed situations. The results indicate that acoustic signal generated by rubbing fault has obvious sudden; In general, the characteristics of acoustic signals induced by different rubbing pair is basically similar, so the characteristics of rubbing fault affected by rubbing pair of material is very small; The fault charac-teristic frequency is 328-420KHZ , 223-300KHZ at low speed.

Abstract: This paper is concerned with the design of a control system for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator (LUCIE). A nonlinear proportional-integral-plus (PIP) control algorithm is developed for regulating movement of excavator arm. The nonlinear dynamics of the hydraulic driven arm is represented using the quasi-linear state-dependent parameter (SDP) model, in which the parameters are functionally dependent on other variables in the system. The model is subsequently utilised to develop a new approach to control system design, based on nonlinear PIP pole assignment. Implementation results demonstrate improved tracking performance of excavator arm in comparison with both linear proportional-integral-derivative (PID) and conventional (linearised) fixed-gain PIP control.

Abstract: In this paper, a cooperative quantum genetic algorithm-particle swarm algorithm (CQGAPSO) is applied to tune both structure and parameters of a feedforward neural network (NN) simultaneously. In CQGAPSO algorithm, QGA is used to optimize the network structure and PSO algorithm is employed to search the parameters space. The amplitude-based coding method and cooperation mechanism improve the learning efficiency, approximation accuracy and generalization of NN. Furthermore, the ill effects of approximation ability caused by redundant structure of NN are eliminated by CQGAPSO. The experimental results show that the proposed method has better prediction accuracy and robustness in forecasting the sunspot numbers problems than other training algorithms in the literatures.

Abstract: User fatigue is an important issue in interactive evolutionary computation (IEC). A user’s evaluation will guide the evolution in IEC and a tired user probably misleads the algorithm. Firstly, the impact of the user fatigue is given. Secondly, the cause of the user fatigue is discussed: he/she will have to keep rational, which means that the user will have to keep the consistency between his/her evaluation and preference. And the necessity for the user to keep rational is also analyzed, which will ensure IEC to converge to the user-most-satisfactory individuals. The study of user fatigue established necessary foundation for future research.