Abstract: A novel four-step commutation is proposed with unequal step for each bidirectional switch cell on the basis on analysis of many proposed commutation methods of matrix converter in this paper. The first and fourth step can be shorter than the second or third one because the actual switching on or off of output current happens on the second and third steps. Here the second step is equal to the third one. This method is implemented with four steps by programming in VHDL language. First, the special flip-flop, 74AHC16373, is obtained by programming so as to make input sector signals, output sector ones and active switching time PWM ones synchronize. Second, the required switching states are flexibly realized in the form of the look-up table by programming in VHDL language for 36 switching combinations of input sectors with output ones. Third, the obtained switching states are judged whether they need commutation by delayers. Finally, the novel method proposed is implemented by switching sequencers. The simulation results have verified its feasibility.
Abstract: A novel refractometer based on photoelectric sensor technology and differential method is proposed. Sensing principle and mathematical model are introduced; structure and key parameters of sensing probe are designed through detail calculation. Theoretical solution shows resolution reaches order of 10-5. Preliminary experiments verify the feasibility of the design, experimental results show stability error better than ±1.02×10-4, error caused by temperature is 6.65×10-6/°C.
Abstract: This paper focuses on the stratospheric airship in the level flight state, and designs a optimal method which combines the direct collocation method and sequentially quadratic programming algorithm to get the optimal trajectories. Both the minimum time and fuel are considered. The result indicates that this method is very efficient to the problem and can supply the idea to utilize the wind to save fuel and time in the actual flight.
Abstract: Monitoring method for dynamical stress of centrifugal blower vane based on Fiber Bragg Grating (FBG) sensing technique is presented in this paper. Consisting of FBG sensors, FBG interrogator and fiber optic rotary joint, this monitoring system has bare FBG as strain sensor, monitors stresses at the inlet and outlet of the centrifugal blower. Details about stick up method of FBG sensors are shown in this paper, either. In addition, this method has been applied to experimental model of centrifugal blower, and it was found that: stress at the outlet of the air vane is more than that at the inlet; within the working range, stress of air vane increases in company with increment of rotating speed, though it is not linear relation between them.
Abstract: Brushless Doubly Fed Machine (BDFM) shows economic promise as a variable speed drive or generator. Seeking for rotor structures with higher modulation effect will be the most important role at present for improving the efficiency and performance of BDFM. After presenting the principle and providing the parameters of BDFM, this paper analyzes the air gap flux density of BDFM with different rotor structures and various pole numbers by using finite element analysis software ANSOFT. The effect of rotor structures and pole numbers on magnetic field modulation of BDFM can be obtained, these conclusions could lay the foundation for BDFM structure optimizing design.
Abstract: According to the problem of the friction between the mover and the static guide rail in the linear motor drive system of CNC machine tool, this paper proposed the direct magnetic levitation permanent magnet linear synchronous motor to achieve friction-free feed. The mover of the direct magnetic levitation permanent magnet linear motor consists of two sets of windings. One is the thrust winding, which is used to generate electromagnetic thrust, the other is the suspension winding, which is used to generate magnetic levitation force. The mathematical model of the motor’s electromagnetic thrust and levitation force is derived by the Maxwell stress tensor method. Ansoft is used for making finite element analysis of the motor’s electromagnetic thrust and levitation force. The results verified the correctness of the mathematical model. The feasibility of friction-free feed with two-winding direct magnetic levitation permanent magnet synchronous motor is proved.
Abstract: In order to realize the pure rolling, improve the contact ratio, remove the backlash and raise the life, a new epicycloids gear drive is put forward. The drive part of the particular mechanism is a wheel with the roller tooth and is called the roller gear. And the driven part is the epicycloids gear. The tooth profile equation is achieved and meshing characteristics is also studied. The basic parameters of the new mechanism are researched and the 3D model is achieved. The research result shows that the new drive is workable and the new mechanism has a wide application prospect.
Abstract: The wheels will idle when the relative slipping speed between the wheel and rail exceeds the reference slipping speed. In order to avoid this phenomenon, the simplified model of wheel-rail traction torque transmission was established. And the adhesion coefficient and vehicle velocity are got through the disturbance observer. Then the recursive least squares method was used to forecast the slope of the adhesion-slip curve. Sliding variable structure controller was used to control the error of wheel velocity and reference velocity. From the results of simulation, this method can be effective to maintain the adhesion coefficient around the maximum. And the slipping speed approached the reference value, so the damage for wheel and rail was effectively prevented which achieved the desired effect.
Abstract: In order to improve the precision of side tone range measuring and realize the range measuring process by software, one kind of three parametric model third-order software phase-locked loop (SPLL) is designed based on three parametric loop filter model and the predominant closed-loop poles theory, which can apply the parameter setting principles of the second-order phase-locked loop; this kind of third-order SPLL is realized through C++ language programming and used as the range measuring system’s side tone phase-locked loop(PLL) to process the experiment data. The results indicates that the precision of phase measuring and capture time satisfy the system’s index.
Abstract: With the continuous development, the gas well productivity will decrease. The deliverability test can be used to evaluate gas well productivity, but this method always needs long test which will affect daily production seriously, especially for low permeability gas wells, also there always isn’t enough data in the field. Aiming at this problem, this article presents a new real time method to get the gas well productivity. This new method avoids deliverability test and only needs daily production and wellhead pressure data, so the analysis process is easy and this method has strong practicality. It is proved that this new method works well in the field case.