Abstract: In this thesis, a kind of jitter is focused on, which is called Native Jitter (NJ) of the Voltage Controlled Oscillator (VCO). The cause of NJ is the high order effect of the transistor itself in the VCO, and almost has no correlation with the control voltage or supply. The detailed analysis of the cause and the evaluation of this NJ is proposed in this paper, and an Inter-locked Dual-loop VCO (ID-VCO) is put forward, in which most of the NJ is eliminated. A test chip of the ID-VCO based on 0.18μm CMOS process is established. Compared with the classical single end VCO, the result shows that the peak to peak value and mean-root-square values of period jitter reduce 15.4% and 16.3%, the same values of cycle-to-cycle jitter reduce 9.82% and 6.98%, respectively.
Abstract: This paper proposes a method for calculating generation shedding and load shedding in the emergency control of power system. The method is based on the theory of transient energy margin sensitivity, combining with the power flow distribution factor technology. It gives generation shedding and load shedding fast and efficiently. The simulation result proves that the method developed is feasible for the construction of emergency control strategy.
Abstract: A gas sensor based on MEMS (microelectro-machine system) has been developed to provide a sensitive means of detecting nitrogen dioxide. The structure, configuration and fabrication steps were described. The sensor was copper phthalocyanine (CuPc) films which caused a resistance change upon exposure to nitrogen dioxide. The sensor demonstrated a good response and recovery time about 4s and 7s separately. Results also indicate to be accordance with the sensitive mechanism of CuPc in terms of semiconductor theory.
Abstract: Double-winding AC-DC Generator are being widely used in self-contained electrical power systems for their obvious virtues. On their stator, two separate windings are distributed, one three-phase winding delivers AC power and the other twelve-phase winding, termed DC windings, are connected to the bridge rectifier to supply DC power. Unlike ordinary three-phase machines, there are four layers winding in each stator slot of the Double-winding AC-DC Generator and the total gap magnetic potential produced by the twelve-phase winding is more complex than 3-phase machines. By analyzing the leakage magnetic flux and the magnetic potential, relevant formulas are derived to calculate the leakage reactance of the machines. All the stator leakage reactance of a realistic Double-winding AC-DC Generator was calculated through the methods presented and the simulation of a sudden shortcut test of the machine was carried out with the parameters calculated. The simulation and test results agree quite well, and show that the formulas presented are correct.
Abstract: In this paper, a novel architecture of Pythagorean Hodograph (PH) curve interpolator based on Nios Ⅱ embedded processor and FPGA is proposed. The whole interpolator including NiosⅡ processor is built in a single FPGA chip. The interpolator uses a two-stage interpolation scheme to reduce the computational burden of PH curve interpolator. The Nios Ⅱ embedded processor implements 1st-stage interpolation, the FPGA receives the command from the Nios Ⅱ processor and implements 2nd-stage interpolation simultaneously. Therefore, the interpolator can implement the real-time PH curve interpolation algorithm steadily to meet the needs of high-speed and high-precision machining.
Abstract: The expression of calculation of the waveguide-stripling-coaxial line directional coupler, Coupling is through small apertures in the form of a circular hole, is derived. The relationships between Technology parameters with the geometric of the directional coupler are analyzed in detail, the numerical results indicate that, in order to get acceptable of coupling coefficient and directivity, ones may not only change the size of the small hole and rotate the probe in the waveguide - waveguide directional coupler, but also the size of stripline as well as the coupler position.
Abstract: In view of the large volume and complex control circuit of current AC regulated power supply, a unipolar AC regulated power supply with chopping control compensation is designed, and the calculation method of output filter parameter of chopping circuit is given. In the system, MCU of STC12C5A62AD with 8-bit A/D input and PWM output is adopted, by which not only simple structure and control but also fast dynamic response are get; DC voltage sampling technique is adopted, so sampling frequency is up to 12.8kHz, sampling precision is high too; PWM chopping frequency is 4kHz, so capacity of filter capacitor and inductors are small, and harmonic is little. Experiment results of prototype show that the system has high precision of output voltage and greater practical value.
Abstract: Permanent magnet linear synchronous motor (PMLSM) suspension system has the merits of no friction, high-speed, high response and so on, using the normal force achieve the mover suspension. The servo performance is affected by the nonlinear coupling between the horizontal trust and vertical normal force, parameters uncertainties and load disturbances. The feedback linearization method is used to achieve the dynamic decoupling of the PMLSM suspicion system and decoupling it Into two linear subsystems; to solve the conflict between disturbance restraint and fast tracking performance, increase the robustness and dynamic stiffness for system, H∞ speed controller based on PDFF and position proportional controller are designed. Simulation results show that the proposed control strategy guarantees the high speed and high precision positioning performance for horizontal axis; the good rigidity and stability for normal suspension length and the strong robustness against load disturbances and parameters variations for the two axes.
Abstract: A lot of ping-pong balls may fall on ground round the ping-pong table, whenever people take part in the ping-pong sport,. In order to collect them conveniently, this paper puts forward a new method that applies aerodynamic principles. By vacuum, ping-pong balls are collected into the collecting box. The special vacuum ball-collector is designed and made. The results show that ball-collector is better than current other ping-pong ball-collectors at time and work. It has broad application worth.
Abstract: High power InGaN-based blue LEDs have been commercialized despite the presence of a high dislocation density in the heteroepitaxial structures. Traditional trial-and-error techniques are very inefficient for improving the process of MOVCD. We analyze the effects of spontaneous and piezoelectric polarization on spontaneous emission rate of blue LEDs on SiC substrate by adjusting screening values and barrier doped concentration. The simulation results indicate to improve characteristics of blue LEDs on SiC substrate, interfacial charges for piezoelectric and polarization should get equilibrium with crystal defects and barrier doped concentration. There is an optimization point.