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Design and control of deformable quadrotor with varying length arms

Science China(Technological Sciences) 2023年第5期66卷 1225-1234页

作者： SUN YiChong XIE MingNa LI YeHui NG WingYin ZHAng Heng LI Zheng Multi-Scale Medical Robotics Centre The Chinese University of Hong KongHong Kong 999077China Department of Surgery The Chinese University of Hong KongHong Kong 999077China Department of Electrical and Electronic Engineering The University of Hong KongHong Kong 999077China College of Optoelectronic Engineering Chongqing UniversityChongqing 400044China

Deformable quadrotors can manipulate their specific structure for specialized tasks or excellent flight performance under diverse conditions.With added deformation mechanism,the quadrotor exhibits higher flexibility;however,this is accompanied by difficulties in modeling analysis and controller design,which are crucial issues.Here,a novel deformable quadrotor that can alter its arm's length is designed by combining the crank-slider mechanism and cross-configuration.The dynamics,including the attitude and position systems,are analyzed and the former is further described as switched linear parameter varying(SLPV)systems from a control-oriented perspective.In addition,a combined SLPV/proportion-integration-differentiation(PID)attitude controller is developed to handle different deformable quadrotor modes,which guarantees the stability of the closed-loop attitude system during the deformation process and achieves attitude tracking.Furthermore,together with the cascade PID position controller,the entire flight controller is constructed whose feasibility is verified via fixed-point hovering and trajectory tracking experiments.

关键词： deformable quadrotor mechanics and control LPV systems switched control strategy specialized aerial system

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BIODIVERSITY AND CONSERVATION OF FRESHWATER FISH IN HOng KOng, CHINA

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水生生物学报 2006年第6期30卷 660-666页

作者： VIRGINIA Laifun Lee MARIA Lauching Young TONY Kingtung Chan SAMUEL Kinsan Lam FRANCO Kwokyan ng JULIA wingyin Chan Agriculture Fisheries and Conservation Department HKSAR Government Cheung Sha Wan Government Offices 303 Cheung Sha Wan Road Hong Kong

We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoirs in Hong Kong but no large natural water bodies. From the 220 sites surveyed, 114 species of 37 families were found. Gobiidae (with 24 species) and Cyprinidae (21 species) were the dominant families. This survey has increased the number of freshwater fish species recorded in Hong Kong to 167. Among these, 71 (42.5%) are primary freshwater fish, 44 are brackish and 46 are vagrants. The remaining 6 species are diadromous. In Hong Kong, freshwater fish are conserved by a combination of measures. About 38% of Hong Kong’s land area is designated as country parks and/or special areas, and is managed for nature conservation and educational purposes. In addition, another 5% of land area is zoned for conservation in the statutory land use zoning system to protect them from development and incompatible land uses. Major development projects have to go through the statutory environmental impact assessment process to ensure that they will not have adverse impact as far as practicable. There are conservation action plans for important species. For example, captive-bred individuals of the endemic Hong Kong Paradise Fish Macropodus hongkongensis have been released to suitable and secure sites inside country parks and their populations are regularly monitored. Other measures such as wetland creation, restoration and enhancement programmes are also implemented for freshwater fish conservation.

关键词： Freshwater fish biodiversity Family composition Species composition Conservation measures

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