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Small-size unmanned helicopter, with its unique characteristics of hovering, flying sideways and backwards, is more superior in maneuverability and flexibility compared with fixed-wing aircraft, so it can be widely used in the military and civilian fields. This paper takes the Tiger-90 small-size unmanned helicopter as research object, developing a control system that is based on ARM, has provided a base for further research. Firstly, the experimental platform of small-scale helicopter is build according to the structure characteristics of helicopter which is selected. After that, the mathematical model of the vertical channel is identified, based on the flight data of the experimental platform. Finally, according to the established model in the vertical channel, a height controller is derived, using the PID control rule.

Coke oven gas collector is important in coking plant, and the pressure control of which is closely relevant to the coke oven gas collecting and the production afterwards. Pressure control of coke oven gas collector is difficult in the coking system, mainly due to the strong coupling and time delay. In this paper, a particular form of coke oven with symmetrical structure is studied, and a decoupling solution to the coking system based on the internal model control theory is proposed, using the feedforward controller combined with the decoupling controller. With the MATLAB toolbox, a numerical solution of the decoupling controller is derived. Simulation results of the real system indicate that the designed decoupling controller is effective in improving the performance of the gas collector to the selected coke oven with symmetrical structure.

In this paper, a geodesic-based method is proposed for the robot path planning problem. The geodesic, on the smooth curved surface constructed by potential field, is used to provide the robot a path to the target without trapping in the local minima. The relation between the potential and the geodesic is analyzed and some local properties of the geodesic are obtained, which are used to adjust the direction of the geodesic-based path. The proposed approach based on the data obtained by the sensor can be applied to the dynamical environment and it is verified by simulations.

A multiplex RT-PCR technique has been developed for differentiation of velogenic, mesogenic and lentogenic pathotypes of Newcastle disease virus (NDV), using a set of three oligonucleotide primers designed from NDV genomic RNA (P1, P2 and P3). The primer pair P1 and P2 generated a RT-PCR product of 204 bp, only with RNA from velogenic and mesogenic strains, whereas the P1 and P3 generated a 364 by product only with RNA from mesogenic and lentogenic strains. Thirty four NDV strains, including some reference strains (known pathotypes), NDV field isolates and NDV vaccine strains, as well as other avian virus strains, were tested with multiplex RT-PCR. All reference strains tested were differentiated in agreement with their intracerebral pathogenicity index (ICPI) values or with the pathotypes known in previous reports. The nucleotide sequence analysis of RT-PCR products for four NDV strains was fully in agreement with the RT-PCR characterisations of these strains. The RTPCR results of other avian RNA viruses further confirmed the reliability and specificity of this technique. However, the RTPCR failed to detect some other avian NDV which may not originate from chicken. This multiplex RT-PCR technique is simple and easy to perform. It could be applied not only to determine the origin of NDV but also may be used diagnostically in molecular epidemiological analysis of ND and for prediction of pathotypes of NDV isolates.

In arid regions, the conflict between forest carbon sequestration and its water consuming has severely limited regional sustainable development. Deeply understanding of the spatial distribution of vegetation carbon density for forest

Low frequency oscillation has been a serious threat to the security and stability of power system operation today. PSS is an effective damping controller to inhibit low frequency oscillation and has been widely used in power system. Location installation of PSS is mostly determined by the participation factors which can be calculated by right eigenvectors (lower frequency oscillation mode shapes) and left eigenvectors. However, in an n-machine system, there are n-1 low frequency oscillation modes whose frequencies are distributed in a small range of 0.2–3.0Hz, which leads close mode may occur. Study has shown that close mode shapes are sensitive to system structural parameters, that is, a small change of structural parameters may lead a big change of close mode shapes. This paper first theoretically analyze the failure of PSS led by the instability of close mode shapes, then New England 10-machine system is employed to validate the conclusion.

In order to solve mode mixing, an improved HHT (IHHT) is proposed to identify modes of low frequency oscillation (LFO) in power systems. Firstly, by means of Fourier transform the approximate frequency range of every mode is determined; then methods such as masking signals or filters are chosen to separate mixing modes. Finally mode parameters can be calculated by linear least quadratic fitting. Simulated signals are analyzed by conventional HHT and IHHT, results show that IHHT can correctly separate mixing modes and identify modes parameters, results are in advance of traditional algorithms, so the proposed algorithm is suitable to mode identification of LFO.