Applied Mechanics and Materials Vols. 220-223

Abstract: Basing on its advantages, doubly-fed wind power generator has become one of mainstream model of wind power generator which is connected with power network directly. But at present there is no relevant articles that can describe the operation principle of doubly-fed wind power generator in detail. The electromagnetism relation of doubly-fed wind power generator is discussed detailedly in this paper based on the basic theory of AC motor, and finds the equivalent circuit and vectorgraph, analyzes the energy transfer relation. This thesis offers theory basis for the design and control of doubly-fed wind power generator.

Abstract: A cluster kernel semi-supervised support vector machine (CKS3VM) based on spectral cluster algorithm is proposed and applied in winch fault classification in this paper. The spectral clustering method is used to re-represent original data samples in an eigenvector space so as to make the data samples in the same cluster gather together much better. Then, a cluster kernel function is constructed upon the eigenvector space. Finally, a cluster kernel S3VM is designed which can satisfy the cluster assumption of semi-supervised study. The experiments on winch fault classification show that the novel approach has high classification accuracy.

Abstract: This paper aimed at finishing a two-stage oil-free high-vacuum system using a molecular pump as the main pump and a rotary vane pump as the backing pump. Before the pump’s inlet, there is a molecular sieve. With the assistance of the high and low vacuum measuring instruments and other accessories, the system can achieve limiting vacuum of 5×10-5Pa in the vacuum chamber whose volume is 0.085m3 and provide the high vacuum needed for vacuum coating equipments whose magnitude is 100mm.

Abstract: The “stick-slip” motion or creep phenomenon is often observed in MW wind turbine yaw system. Yam system stick-slip coupling phenomenon was analyzed, and stick-slip coupling kinematic model was established and simulated by Simulink. The influence of torsional stiffness, friction coefficient difference, rotating speed, damping ratio and tightening torque on system was researched. Main measures for elimination of stick-slip coupling phenomenon were given through theoretical analysis and simulation calculation.

Abstract: A high performance speed-regulating control system with high power factor and small harmonic pollution was realized. Firstly, the mathematical model of the grid side PWM converter was derived, and then voltage, current double close-loop control strategy based on a grid voltage orientation was proposed. Secondly, the mathematical model of wound-rotor induction motor(WRIM) was derived, and then the rotor side PWM converter control strategy based on a stator voltage orientation was designed. Finally, experimental platform for doubly-fed speed-regulating control system was built. Experimental results showed that the control strategy is feasible and efficient.

Abstract: The power switch circuit of electrical power steering (EPS) is analyzed. A kind of PWM hybrid control algorithm combining the Unipolar reversible PWM mode of brush DC motors with its bipolar reversible PWM mode is put forward in this paper to improve the performance of current EPS system. The basic switch principle between Unipolar and Bipolar PWM mode is that the voltage during the switch process remains constant. The switch process and practical application of DC motor with Uni-Bipolar hybrid control mode in EPS is analyzed. The results show that PWM hybrid mode has exhibited good performance in vehicle electric power steering system.

Abstract: The paper presents a super capacitor energy storage device to recycle the power with regenerative braking which the elevator inverter generates. During the running of the elevator, the fluctuation of DC bus voltage is greater, this will impact on grid greatly, especially on energy feedback. It will disturb user electricity distribution system and endanger the operation of power system. Through switching control of the Bi-directional DC/DC converter, the converter can control charge and discharge of the super capacitor. When the elevator inverter generates a power with regenerative braking, the power energy is charged to the super capacitor. it discharges the energy power when the elevator is accelerated or load is added to the elevator. Experimental results carried out on a 10-kW elevator inverter are presented.

Abstract: According to the lack of the part of the equipment design parameters of a certain type of ship power systems, the algorithm of recursive least squares for model parameter identification is studied. The mathematical model of the propulsion motor is established. The model parameters are calculated and simulated based on parameter identification method of recursive least squares. The simulation results show that a more precise mathematical model can be simple and easily obtained by using of the method.

Abstract: A double-layer structure of oil storage tank was proposed in this paper to overcome the shortcomings of existing oil storage tanks and its detection method. Using 93# gasoline, diesel and water as working medium, the leakage diffusion characteristic of tank floor was researched based on a experimental system. The research results testify the reliability and sensitivity of the experimental system. Furtherly, the influencing rule of leak positions and leak volume (Q) on the leakage diffusion was studied by using 93# gasoline. The results show that for the same amount of leakage, the leakage on the center of tank floor diffused quickly, was the most easily detected part; and that on the edge of the tank floor was the most difficult to be detected. For leakage occurred in same position, the volume fraction (φ) in pipeline increased with the increase of leakage. The result of research has a great significance for fastening localization of double bottom structure of oil storage tank.

Abstract: Rope force of recoil starter is an important design parameter for starting safety. This paper analyzes the starting resistance torque of an internal combustion engine, and then proposes the appropriate calculation methods of friction resistance moment, compression resistance moment and inertia resistance moment. Taking several types of internal combustion engines for example, this paper analyzes the main factors influencing rope force, and then draws the conclusion that displacement and ambient temperature are the key to the rope force. The work provides the basis for the design and inspection of recoil starter.