disturbance

摘要： Dear editor,This letter addresses the leader-following consensus problem(LFCP)for multiple Euler-Lagrange(EL)systems with a directed topology.Firstly,a local high-order disturbance observer(HODO)is put forward to estimate the compound disturbance for each EL system itself,and the estimate error can ultimately achieve zero.Based on this HODO,an event-based distributed sliding mode control protocol is proposed to solve the LFCP of multiple EL systems.Furthermore,the reachability of the sliding mode surface is analyzed.Besides,it should be pointed out that the interval between any two triggering instants is a strictly positive value,hence the well-known Zeno behavior is avoided for the developed event-based protocol.Finally,the effectiveness of the proposed HODO and control protocol is further verified by a numerical simulation.

摘要： In the state Meghalaya,northeast India,>80%of the forest lands are owned by local communities and managed by traditional institutions.These forests are under severe threats due to a number of human disturbances.The present study was conducted to assess the plant diversity and identify the community forests for priority conservation in Khasi Hills of Meghalaya.Floristic explorations carried out in the 87 forests reveals the presence of 1300 plant species of which 400 are either rare,endemic or threatened.Of the different forest categories,reserve forests had the highest number of species(1190),followed by sacred forests(987 species)and village forests(786 species).Majority of the forests(56)had high-species richness,irreplaceability level(42 forests)and vulnerability level(54).In terms of area,13.8%(1666.8 ha)fall under low risk while 1855 ha under high risk zone.High risk zone was mostly represented by village forests.An area of 7661.56 ha of community forests falls under high priority category and hence calls for immediate conservation actions.The conservation priority map generated in the present study will help to concentrate the protection strategy to the demarcated and adjoining areas and help conservationists and planners to evolve effective strategies for conservation of the community forests.

摘要： In this paper, we design a fault diagnosis scheme for a class of variable coefficient wave equation (an overhead crane system), which is composed of an observer and its output error is treated as residual signal. When the system is in a healthy state, the output residual signal decays exponentially. Due to the existence of external disturbance, the residual is not zero in the state without fault. Therefore, we further design a reasonable threshold which is based on the upper bound of the residual dynamics and external disturbance to reduce the influence of external disturbance and determine whether the system fault occurs. The convergence properties of partial differential equation (PDE) observer and residual signal are analyzed by Lyapunov stability theory. Finally, the effectiveness of this fault diagnosis is illustrated by simulation and we can judge whether this overhead crane system fails by this fault diagnosis scheme.

摘要： Dear editor,Fault-tolerant tracking control has recently become an area of research interest, in which fault detection, fault-tolerant control(FTC), and tracking-control techniques are integrated [1, 2]. It is noteworthy that disturbance is a critical factor that degrades system performance [3]. Therefore,disturbance attenuation is indispensable when designing a controller scheme. A common method is to develop a compensator, i.e., an anti-disturbance mechanism could be constructed to compensate for the effects of the disturbance.In previous studies, the disturbance observer based control has been reported as an efficient disturbance-attenuation method [4].

摘要： In the above paper,the afliation of Xin Zhang was incorrect.It should read``He is is with the College of Electrical Engineering,Zhejiang University,Hangzhou 310027,China and with Hangzhou Global Scientific and Technological Innovation Center,Zhejiang University,Hangzhou 310058,China.(e-mail:zhangxin_ieee@163.com).

摘要： Dear editor,The requirements for control performances(e.g.,the control accuracy)are highly increasing in practical engineering systems.However,multiple disturbances,which consist of internal disturbances,external disturbances,and model uncertainties in complex control systems may degrade the control performance[1].

摘要： In this paper, robust control problem is addressed for quad-rotor delivering unknown time-varying payloads. Firstly, the model of a quad-rotor carrying payloads is built. Dynamics of the payloads are treated as disturbances and added into the model of the quad-rotor. Secondly, to enhance system robust-ness, the extended state observer (ESO) is applied to estimate the disturbances from the payloads for feedback compensation. Then a type of predictive controller targeting multiple-input-multiple-output (MIMO) system is developed to degrade the influences caused by sudden changes from load-ing/dropping of the payloads. Finally, by making comparison with the con-ventional cascade proportional-integral-derivative (CPID) and the sliding mode control (SMC) approaches, superiority of the scheme developed is va-lidated. The simulation results indicate that the CPID method shows poor performance on attitude stabilization and the SMC shows input chattering phenomenon even it can achieve satisfied control performances.

摘要： The intelligence nonlinear control scheme via double power reaching law based sliding mode control method is proposed to solve the problems of model uncertainties and unknown outside disturbances.Firstly,the aerodynamic parameters of the morphing vehicle are replaced with curve-fitted approximation to build the accurate model for control design in the hypersonic flight.Then the nonlinear vehicle model is transformed into the strict feedback multi-input/multi-output nonlinear system by using the input-output feedback linearization approach.At the same time,the disturbance observer is used to approximate the unknown disturbance,and the sliding mode method is used to solve the problem of non-matching and uncertainty.Finally,according to the buffeting problem in sliding mode control,the double power is improved.Simulation results show that the proposed method can ensure the global stability of the closed-loop system,and has good tracking and robust performance.

摘要： Background: Particle size distribution and hydraulic conductivity of coastal no-agricultural lands are not available. This study characterized the particle size distribution and hydraulic conductivity on coastal non-agricultural land along the coastal plain of Gaza. Materials and Methods: Six soil profiles were digged along the coastal plain in Gaza Strip and soil samples were collected from 0 - 150 cm depth. Four soil plots around each site were used to determine the hydraulic conductivity using Infiltrometer method. Four particle size groups were identified, group 1 (630 nm), group 2 (200 nm), group 3 (63 nm) and group 4 (20 nm). Results: Dominancy of particle size group 2 was noticed in all sites followed by group 3. Groups 1 and 4 were less dominant in all sites. Hydraulic conductivity ranged from lower value 0.27 in the control soil plot in Khan Younis (site 1) to the highest value 1.76 m/s in disturbed soil plot in Shakhejjlen (site 3) with regression coefficient (R2) range of 0.9725 - 0.997 indicating strong positive association. Conclusion: It can be concluded that the coastal non-agricultural land is sandy with various hydraulic conductivity values due to different particle size distribution. These data are useful to the scientific community around the world and will be helpful to speculate potential risk factors to life of ecosystem.

摘要： Freshwater swamp forests are wetland ecosystems with poorly understood ecology. With increasing degradation across the Niger basin (where it is the most extensive across West Africa), it is deemed important to understand its distribution, patterns and composition. This is aimed at both increasing botanical inventories in the ecosystem and also elucidate vital steps that could guide its effective conservation. This study assessed the floristic composition and diversity across 16 one hectare forest plots and sought to show how varied the sites were in terms of diversity, stem density and basal area. The survey showed that the area had 116 species within 82 genera and 36 families. The number of species found in each of the disturbed sites was generally higher than the intact forest sites, which was not diverse but comprised many trees with higher basal area. While the stem density which ranged from 94 - 409 stems·ha-1 is comparable with that of other tropical forests, species richness was low (ranging from 8.65 - 0.52). Diversity ranged from 3.38 - 0.98 and was higher in disturbed sites than in intact locations. Species richness was generally low and implies that loss of species in the ecosystem could threaten species’ existence and conservation in the ecosystem. Disturbed locations had more species than the intact zones and as such show the importance of targeted conservation not only in the undisturbed locations but also in the disturbed locations with a higher species value and potential for species stability of the ecosystem.

摘要： A new congestion control algorithm of code division multiple access (CDMA) is developed to re-duce the cost of system. Firstly, the paper defines the utility function of resource throughout, and then set upthe mathematics model according to the wireless resource characteristic. In the approach only the non-linearcompensating term, solution of a sequence of adjoint vector differential equations, is required iteration. Bytaking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal conges-tion control algorithm of CDMA can be obtained. It is proved by analysis in theory and system level simula-tion that the congestion control algorithm can enlarge system throughput while controlling system load.

摘要： A new congestion control algorithm of code division multiple access (CDMA) is developed to re-duce the cost of system. Firstly, the paper defines the utility function of resource throughout, and then set upthe mathematics model according to the wireless resource characteristic. In the approach only the non-linearcompensating term, solution of a sequence of adjoint vector differential equations, is required iteration. Bytaking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal conges-tion control algorithm of CDMA can be obtained. It is proved by analysis in theory and system level simula-tion that the congestion control algorithm can enlarge system throughput while controlling system load.

摘要： A new congestion control algorithm of code division multiple access (CDMA) is developed to re-duce the cost of system. Firstly, the paper defines the utility function of resource throughout, and then set upthe mathematics model according to the wireless resource characteristic. In the approach only the non-linearcompensating term, solution of a sequence of adjoint vector differential equations, is required iteration. Bytaking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal conges-tion control algorithm of CDMA can be obtained. It is proved by analysis in theory and system level simula-tion that the congestion control algorithm can enlarge system throughput while controlling system load.

摘要： A new congestion control algorithm of code division multiple access (CDMA) is developed to re-duce the cost of system. Firstly, the paper defines the utility function of resource throughout, and then set upthe mathematics model according to the wireless resource characteristic. In the approach only the non-linearcompensating term, solution of a sequence of adjoint vector differential equations, is required iteration. Bytaking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal conges-tion control algorithm of CDMA can be obtained. It is proved by analysis in theory and system level simula-tion that the congestion control algorithm can enlarge system throughput while controlling system load.