Applied Mechanics and Materials Vols. 291-294

Abstract: Based on the theory of failure physics, reliability enhancement test is a test technology of stimulation in order to improve reliability by discovering, researching and curing failure. In this paper, the main factors inducing failure modes of undercarriage light box were analyzed, and the environmental sensitive stresses affecting reliability were determined. The testing program was designed and test profiles were established based on the theory of reliability enhancement test. Additionally, the test results were analyzed based on failures of products in order to carry out improvement measures.

Abstract: A minimum-energy consumption control algorithm is applied to motion control of a four-wheel drive omni-directional mobile robot (FDOMR) in actual application environment. After establishing the robot’s dynamic equations with motor model, we have chosen a practical cost function as the total energy drawn from the batteries. Considering the translation and rotation, we have found out the velocity curve by optimal control theory. Various simulations are performed and the consumed energy is compared to the normal control method that without minimum energy consumption control. Simulation results reveal that the energy saving is much more compared to the traditional control, the operational time of the FDOMR with given batteries is lengthened and the efficiency of battery is improved.

Abstract: In this paper, we investigate of a class of predator-prey system with rate stocking and time delay, the existence positive periodic solution by using coincidence degree theory. We obtain the sufficient conditions which guarantee existence of the positive periodic solution of the periodic system. Some new results obtained.

Abstract: The pressurizer is an important device in nuclear reactor system, and the traditional PID regulator is usually used to control pressure system of pressurizer in modern reactors. However, it is difficult to get precise parameters of traditional PID controller, and the PID control method is relied on the precise mathematical model badly. And the response of PID controller is often shown by the large amount of overshoot and long setting time which are not the desired results. For such a large inertia and complex time-varying control system, the tradition PID controller can not obtain the satisfy control results. A controller based on BP neural network in this paper has a simple structure, and the parameters of PID controller can be tuned on-line by the neural network self-learning characteristics. The computer simulation experiment demonstrates that the BP neural network PID controller performs very well when compared with the tradition PID regulator in minimal overshoot and more quick response.

Abstract: This paper introduces the process of shield tunnel construction in the advanced synchronous automatic laser measurement oriented technology, overcomes the artificial measurement process cannot get boring machine real-time posture and deviation, construction more difficult to control, affect the construction progress and shortcomings, the similar project construction provides effective reference.

Abstract: In ultra-high voltage transmission system, the electrostatic induction generated by power frequency electric field will exerts negative effects on the electrical automation equipment within the substation and, in particular, will leads long-term harm to staffs’ health. However, researches of electric field environment in ultra-high voltage transmission system merely concentrate on calculating the electric field intensity caused by three-phase limited length wire or three-phase infinite wire within the transmission, without considering the method of calculating half-infinite wire which represents “one end is fixed, while the other end is infinite length’s wire”. Consequently, a new method named “Charge Simulation-Genetic Algorithm (CS-GA) method” which can efficiently calculate power frequency electric field inside of the substation is proposed in the paper. In CS-GA method, the effective calculating length is determined by genetic algorithm method’s optimization, which in other words, half-infinite length wire is substituted for limited length wire in calculating the electric field intensity. The simulation results indicate that CS-GA method is a relatively accurate, efficient and reasonable way on calculating the power frequency electric field inside of the substation.

Abstract: In the process of the Hilbert-Huang transform, empirical mode decomposition (EMD) may result in the end effect and modal aliasing when processing data, so proposing Ensemble Empirical Mode Decomposition (EEMD) instead of EMD, and assessing the accuracy of the two decomposition processes according to the total energy of the signal before and after the decomposition. Take a comparison between the Hilbert-Huang transform and the wavelet transform, the localization showed that the Hilbert-Huang transform is better than wavelet transform in the fault location of transmission line.

Abstract: Visual perception can provide environmental information for the control strategy of the unmanned surface vehicle, and the detection of wave grade is an important aspect of visual perception. Based on the theory of Fourier transform, this paper analyzes frequency domain characteristics of the wave image in different light and sea state. According to the relationship between different rectangle ring energy percentage, a method of judging wave grade is proposed. Firstly, the characteristic of the wave image is enhanced through histogram equalization; then, the image is transformed to frequency domain by FT; thirdly, the image features are extracted by the method of rectangle ring energy percentage; finally, waves grade are judged by the relationship between the first and the second stage rectangle ring energy percentage. The experimental results show that this method can effectively detect the wave grade and have the advantage that light condition has less effect on it.

Abstract: This paper presented a novel resonant frequency tracking control method for electronic ballast of electrodeless lamp. The proposed method enables the operation frequency of the electronic ballast to continuously track the resonant frequency of the resonant tank by detecting the phase difference between input voltage of resonant tank and resonant capacitor voltage . Using the proposed control method, the ballast can be optimized to operate with its maximum power capability and guarantee good load matching, even when the resonant tank parameters vary. The detailed implementation of the controller was presented in this paper. Simulation and experimental results verify the performance of the proposed control method.

Abstract: Grid-voltage feed-forward control was added to improve the grid-connected current quality on photovoltaic grid-connected inverter. The method decreases the phase difference between the grid-connected current and grid voltage and reduces the total harmonics distortion (THD) of grid-connected current. So the grid-voltage feed-forward compensation can improve grid-connected current availably and keep the current frequency and phase synchronous to the grid. The study is validated through simulations and field experiments. Experimental results obtained on 2.5-kw inverter demonstrate the feasibility of the proposed method.