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In order to improve the virtual flux oriented vector control performance of PWM rectifier, an improved observation method of virtual flux-linkage is proposed. To avoid the relevant problems of pure integrator, and to achieve the accurate observation of the grid voltage’s phase, three first order low-pass filters are cascaded to displace the pure integrator. Based on the SVPWM modulation module and the presented algorithm, grid voltage sensorless control system of three-phase PWM rectifier is given. Simulation results have shown that: either in rectifying or inverting status, the amplitude and phase of virtual flux-linkage can be observed accurately, i.e. the control system of PWM rectifier can operate reliably without the grid voltage sensors; the presented estimation method of virtual flux-linkage is effective.

This research proposes an Accelerated Life Test System and has realized the reliability test of water quality analyzer. ALT (Accelerated Life Test) system is based on the principle of step stress accelerated life test and takes temperature as the accelerated stress. The system includes lower computer PLC and upper computer software of MCGS. In this research, Upper computer using configuration software to connect with the SIEMENS S7-300 PLC, in order to realize data acquisition and system control. This system improves the reliability test efficiency of the water quality analyzer, reduces the cost of test and has good economic efficiency.

In order to solve the difficult problem of the transmission-type smoke meter response time, which needs to be settled urgently, response time testers have been developed, according to China's metrological verification regulation JJG 976-2010《Calibration procedures of transmission-type smoke meter》. The tester integrated several communication protocols of transmission-type smoke meter manufacturers, takes measurements at every 20ms, draws absorptance N curves in real time and displays the final response time in man-machine interface. The measuring range of the tester is (600~2000) ms, and the error is ±20ms. It is very convenient, fast, and accurate to verify for transmission–type smoke meter and traffic analyzer.

The short life due to heavy wear is a bottleneck that limits the usage of mechanical excavators for hard rock cutting. Thermally stable diamond composite (TSDC) tipped cutting tools have the main advantages of good thermal stability, high wear resistance and ability to mine harder deposit compared to the conventional tungsten carbide (WC) tipped cutting tools. Super Material Abrasive Resistant Tool (SMART*CUT) based on TSDC tip has been developed by CSIRO to improve the effectiveness of cutting tools when dealing with hard deposit in mining and civil industries. In this study, the effects of attack angle and depth of cut on the cutting performance of SMART*CUT picks in different cutting orientations were investigated. A tri-axial dynamometer and a data acquisition system were used to measure the cutter forces. Normal force, cutting force and resultant angle were correlated with depth of cut and attack angle. Cutting performances were compared in different cutting orientations. The results would be beneficial to the selection of mechanical excavator motor and the optimization of cutting drum design to some extent.

For the strong coupling problem of three-phase bearingless induction motor which is a multi- variable and nonlinear object, a kind of decoupling control strategy based on inverse system method is proposed. The reversibility of torque subsystem was analyzed based on rotor flux orientation, and the decoupling control strategy based on inverse system method was analyzed. Then the torque system was decoupled into two second-order linear subsystems, i.e. the rotor speed subsystems and the rotor flux subsystems. The suspension system adopts negative feedback control; the required air-gap flux linkage of torque system was obtained from the rotor flux and stator current. Finally, synthesis and simulation of the overall control system were researched. Simulation results demonstrate that good performance of decoupling control can be achieved. The presented control strategy is feasible and available.

In order to improve the efficiency of metrological ordinary work in water pollution source online monitor instrument and reduce the measurement personnel's labor intensity. 3G technology has been used to connect test instrument with the client's network through the study of the STM32 type microprocessor and analog-to-digital conversion to test instruments output current. DTU and 3G wireless network have been used to complete the testing data of the transmission, as well as formulate the corresponding server and client software,which perfect man-machine interface and facilitate man-machine interaction. Field experiments show that the system is stable and reliable, which can effectively meet the demand of the measurement and have a broad application prospect.

to hold the merits of the traditional hysteresis controller, and at the same time, hold back the change of switching frequency and reduce the switching power loss in hysteresis control of PWM rectifier, based on the relationship between line currents and switching status, an improved algorithm of double-hysteresis current control method for three-phase voltage-type PWM converter was proposed. In the strategy, the position of reference voltage vector can be detected by double hysteresis, PLL circuit can detect the output of switching states. The proposed algorithms not only hold the merits of traditional hysteresis, such as quick current response and current limited capacity, but also, it can overcome the drawback of non-fixed switching frequency of traditional hysteresis. The algorithm has been simulated and verified by MATLAB/simulink platform, and the system operates stably.

Linear discriminant analysis (LDA) is a popular method among pattern recognition algorithms of machine olfaction. However, “Small Sample Size” (SSS) problem would occur while using LDA algorithm with traditional Fisher criterion if the within-class scatter matrix is singular. In this paper, maximum scatter difference (MSD) criterion and LDA were combined to solve SSS problem, so that three kinds of Chinese herbal medicines from different growing areas were accurately classified. At the same time, the classification result was enhanced. It works out that only a few samples of Anhui Atractylodes are classified incorrectly, however, the classification rate reaches 97.8%.

In order to address the limitations of single parameter evaluation of engine oil performance, a portable vehicle oil performance detector is designed, realizing comprehensive on-line detection of oil rapidly, easily, and accurately. The detector takes oil performance as study object and proposes an on-line measuring method of oil performance through detection of oil viscosity, dielectric constant and temperature. Data and information collected by transmitter are sent to PIC single-chip microcomputer through RS485 communication module. Measured values are displayed on the LCD by SCM receiving the key signals. Test results show that, the detector works stably and is easy to use with small error, and is able to further determine the extant of oil contamination through a comprehensive analysis of the three measuring parameters. To a certain extant, it promotes the rational use of oil.