摘要 :
First,unscented Kalman filter parameter estimation method is proposed to solve the optimal low-thrust transfer problem to Geostationary Orbit.Due to operational constraints of attitude control actuators and uncertain perturbations...
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First,unscented Kalman filter parameter estimation method is proposed to solve the optimal low-thrust transfer problem to Geostationary Orbit.Due to operational constraints of attitude control actuators and uncertain perturbations, a robust closed-loop guidance scheme of constant low-thrust is implemented .The essential idea of the guidance law is to decouple the original multiple revolution optimal control problem into a sequence of trajectory tracking problem in one revolution. Analytical equations are deduced under the condition of continuous constant acceleration. Using these equations, taken the node times of the thrust arcs and the attitude of the thrust as variables, the trajectory tracking problem in one revolution is transformed into an optimization problem with the nonlinear constraints of minimum attitude maneuver time and the consistency of attitude. Finally the whole trajectory optimization approach developed in the paper is applied to low thrust GTO-GEO transfer design, the results show that the tracking error and boundary error are very small.
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摘要 :
First,unscented Kalman filter parameter estimation method is proposed to solve the optimal low-thrust transfer problem to Geostationary Orbit.Due to operational constraints of attitude control actuators and uncertain perturbations...
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First,unscented Kalman filter parameter estimation method is proposed to solve the optimal low-thrust transfer problem to Geostationary Orbit.Due to operational constraints of attitude control actuators and uncertain perturbations, a robust closed-loop guidance scheme of constant low-thrust is implemented .The essential idea of the guidance law is to decouple the original multiple revolution optimal control problem into a sequence of trajectory tracking problem in one revolution. Analytical equations are deduced under the condition of continuous constant acceleration. Using these equations, taken the node times of the thrust arcs and the attitude of the thrust as variables, the trajectory tracking problem in one revolution is transformed into an optimization problem with the nonlinear constraints of minimum attitude maneuver time and the consistency of attitude. Finally the whole trajectory optimization approach developed in the paper is applied to low thrust GTO-GEO transfer design, the results show that the tracking error and boundary error are very small.
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It is well known that human resource is the core component in nonprofit organizations, for mission driven organizations relies on their employees to deliver the services that nonprofit stakeholders expect. The understanding of...
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It is well known that human resource is the core component in nonprofit organizations, for mission driven organizations relies on their employees to deliver the services that nonprofit stakeholders expect. The understanding of issue why do people or what sort of persons choose to work in nonprofit sector goes prior to the competitive strategies nonprofit organizations should adopt to enlist the desirable employees not only in quantity but in quality. The paper begins with an idea that the nonprofit sector shall have its own landscape of the individuals and their service motivations distinctive from those in the for-profit and public sectors, and then follows an argument that egoism is the other side of the nonprofit coin based on analysis at both organization-level and individual-level. Finally, different from the conventional framework such as dichotomy of extrinsic and intrinsic supported by many scholars, a new analytical matrix is advocated, which categorizes the gene of individual into four types, which would help to understand the real demands underneath the individuals' option to work in nonprofit sector.
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摘要 :
It is well known that human resource is the core component in nonprofit organizations, for mission driven organizations relies on their employees to deliver the services that nonprofit stakeholders expect. The understanding of iss...
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It is well known that human resource is the core component in nonprofit organizations, for mission driven organizations relies on their employees to deliver the services that nonprofit stakeholders expect. The understanding of issue why do people or what sort of persons choose to work in nonprofit sector goes prior to the competitive strategies nonprofit organizations should adopt to enlist the desirable employees not only in quantity but in quality. The paper begins with an idea that the nonprofit sector shall have its own landscape of the individuals and their service motivations distinctive from those in the for-profit and public sectors, and then follows an argument that egoism is the other side of the nonprofit coin based on analysis at both organization-level and individual-level. Finally, different from the conventional framework such as dichotomy of extrinsic and intrinsic supported by many scholars, a new analytical matrix is advocated, which categorizes the gene of individual into four types, which would help to understand the real demands underneath the individuals' option to work in nonprofit sector.
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In order to meet the requirements of spacecraft fly-around technology in on-orbit service mission, spacecraft forced fly-around trajectory design and control scheme is investigated. Based on the analytic solution of the C-W equati...
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In order to meet the requirements of spacecraft fly-around technology in on-orbit service mission, spacecraft forced fly-around trajectory design and control scheme is investigated. Based on the analytic solution of the C-W equations, four fly-around trajectories are designed, including bi-elliptic, teardrop, bi-teardrop, multi-impulse fly-around based on nominal trajectory. The formula between initial states of following spacecraft and the shape of fly-around trajectory is derived, and the analytic expressions of four fly-around trajectories and the impulse control scheme are proposed. Simulation results verify that four trajectories designed could be used in spacecraft slow fly-around and fast fly-around. The velocity consumptions of different trajectories with fly-around period are compared. The theory of spacecraft forced fly-around trajectory design and control is improved, and the results provide reference for engineering application.
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摘要 :
In order to meet the requirements of spacecraft fly-around technology in on-orbit service mission, spacecraft forced fly-around trajectory design and control scheme is investigated. Based on the analytic solution of the C-W equati...
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In order to meet the requirements of spacecraft fly-around technology in on-orbit service mission, spacecraft forced fly-around trajectory design and control scheme is investigated. Based on the analytic solution of the C-W equations, four fly-around trajectories are designed, including bi-elliptic, teardrop, bi-teardrop, multi-impulse fly-around based on nominal trajectory. The formula between initial states of following spacecraft and the shape of fly-around trajectory is derived, and the analytic expressions of four fly-around trajectories and the impulse control scheme are proposed. Simulation results verify that four trajectories designed could be used in spacecraft slow fly-around and fast fly-around. The velocity consumptions of different trajectories with fly-around period are compared. The theory of spacecraft forced fly-around trajectory design and control is improved, and the results provide reference for engineering application.
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Agriculture equipment is the guarantee of materials and core support of methods of increase of rate of field yields, labor production and resource utilization. Its intelligent and advanced technology of manufacturing, represented ...
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Agriculture equipment is the guarantee of materials and core support of methods of increase of rate of field yields, labor production and resource utilization. Its intelligent and advanced technology of manufacturing, represented by the detection of information of agriculture equipment, has been effectively developed in recent years. However, it is lack of the research of the technology of load monitoring oftractors. The working environment of tractors is complicated due to un-uniform working load. Moreover, it is hard to wire and set sensors on tractors, so the expandability of device results is not satisfactory. In recent years, wire/ess sensor technology has been significantly developed. The technology of Short-distance self-organizing networks represented by ZigBee has become the first selection of wireless sensor network. ZigBee becomes an effective settlement of problems for traditional wired monitoring method. Therefore, this paper proposes a wireless monitoring system of working load of tractors based on ZigBee. In order to collect the data ofplowing, rotary tillage, joint tillage, deep pine and more work conditions of tractors, two-dimensional pin shaft sensors were selected to detect traction forces and dynamic torque sensors were selected to detect rotation rates and torque . For each detecting location, a node of the wireless network was arranged. Data was transferred from the nodes to aggregation node, which could transfer data coming from the wireless network nodes to a terminal. The data was able to be displayed by the terminal. Test results demonstrated that the system was effective and reliable to monitor the work load of tractors. This research provides a rapid and effective method for monitoring information of working load oftractors, giving a related reference for tractor research of low power consumption, high work efficiency and great security.
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Aiming at the characteristics of long delay, high error code, high dynamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on movin...
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Aiming at the characteristics of long delay, high error code, high dynamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on moving nodes is proposed. By using the numbering in the asking messages and response messages, the time required for each message transmission is determined, and the synchronization can be completed in different slots to improve the utilization efficiency of the time resource. Aiming at the high-speed motion of nodes, a change rule of propagation delay is assumed, which is calculated by increasing the number of message transmission times. Then, the slot deviation caused by node motion is calculated and the deviation is compensated and the synchronization accuracy and stability is improved. The simulation results show that the integrated data link slot synchronization algorithm improves the synchronization accuracy under the premise of completing the integrated data link synchronization.
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摘要 :
Aiming at the characteristics of long delay, high error code, high dynamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on movin...
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Aiming at the characteristics of long delay, high error code, high dynamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on moving nodes is proposed. By using the numbering in the asking messages and response messages, the time required for each message transmission is determined, and the synchronization can be completed in different slots to improve the utilization efficiency of the time resource. Aiming at the high-speed motion of nodes, a change rule of propagation delay is assumed, which is calculated by increasing the number of message transmission times. Then, the slot deviation caused by node motion is calculated and the deviation is compensated and the synchronization accuracy and stability is improved. The simulation results show that the integrated data link slot synchronization algorithm improves the synchronization accuracy under the premise of completing the integrated data link synchronization.
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摘要 :
Aiming at the characteristics of long delay, high error code, high dvnamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on movin...
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Aiming at the characteristics of long delay, high error code, high dvnamoic and asymmetric propagation of uplink and downlink in space-ground integrated data link, an integrated data link slot synchronization method based on moving nodes is proposed. By using the numbering in the asking messages and response messages, the time required lor each message transmission is determined, and the synchronization can be completed in different slots to improve the utilization efficiency of the time resource. Aiming at the high-speed motion of nodes, a change rule of propagation delay is assumed, which is calculated by increasing the number of message transmission times. Then, the slot deviation caused by node motion is calculated and the deviation is compensated and the synchronization accuracy and stability is improved. The simulation results show that the integrated data link slot synchronization algorithm improves the synchronization accuracy under the premise of completing the integrated data link synchronization.
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