Transactions of Nanjing University of Aeronautics & Astronautics
Volume 36,Issue 2,2019 Table of Contents
2019, 36(2):189-196.
DOI: 10.16356/j.1005-1120.2019.02.001
Abstract:
We review the controllability research on spacecraft attitude based on nonlinear geometry control theory. The existing studies on attitude controllability are mostly concerning the global controllability and small time local controllability (STLC). A presentation of study methods and connotation in both aspects is briefly carried out. As a necessary condition of reconfigurability, the controllability of the faulty attitude control system is studied. Moreover, two reconfigurability conditions based on controllability results that consider the actuator faults for a pyramid configuration spacecraft are provided.
We review the controllability research on spacecraft attitude based on nonlinear geometry control theory. The existing studies on attitude controllability are mostly concerning the global controllability and small time local controllability (STLC). A presentation of study methods and connotation in both aspects is briefly carried out. As a necessary condition of reconfigurability, the controllability of the faulty attitude control system is studied. Moreover, two reconfigurability conditions based on controllability results that consider the actuator faults for a pyramid configuration spacecraft are provided.
2019, 36(2):197-204.
DOI: 10.16356/j.1005-1120.2019.02.002
Abstract:
Achieving accurate navigation information by integrating multiple sensors is key to the safe operation of land vehicles in global navigation satellite system (GNSS)?denied environment. However, current multi?sensor fusion methods are based on stovepipe architecture, which is optimized with custom fusion strategy for specific sensors. Seeking to develop adaptable navigation that allows rapid integration of any combination of sensors to obtain robust and high?precision navigation solutions in GNSS?denied environment, we propose a generic plug?and?play fusion strategy to estimate land vehicle states. The proposed strategy can handle different sensors in a plug?and?play manner as sensors are abstracted and represented by generic models, which allows rapid reconfiguration whenever a sensor signal is additional or lost during operation. Relative estimations are fused with absolute sensors based on improved factor graph, which includes sensors’ error parameters in the non?linear optimization process to conduct sensor online calibration. We evaluate the performance of our approach using a land vehicle equipped with a global positioning system (GPS) receiver as well as inertial measurement unit (IMU), camera, wireless sensor and odometer. GPS is not integrated into the system but treated as ground truth. Results are compared with the most common filtering?based fusion algorithm. It shows that our strategy can process low?quality input sources in a plug?and?play and robust manner and its performance outperforms filtering?based method in GNSS?denied environment.
Achieving accurate navigation information by integrating multiple sensors is key to the safe operation of land vehicles in global navigation satellite system (GNSS)?denied environment. However, current multi?sensor fusion methods are based on stovepipe architecture, which is optimized with custom fusion strategy for specific sensors. Seeking to develop adaptable navigation that allows rapid integration of any combination of sensors to obtain robust and high?precision navigation solutions in GNSS?denied environment, we propose a generic plug?and?play fusion strategy to estimate land vehicle states. The proposed strategy can handle different sensors in a plug?and?play manner as sensors are abstracted and represented by generic models, which allows rapid reconfiguration whenever a sensor signal is additional or lost during operation. Relative estimations are fused with absolute sensors based on improved factor graph, which includes sensors’ error parameters in the non?linear optimization process to conduct sensor online calibration. We evaluate the performance of our approach using a land vehicle equipped with a global positioning system (GPS) receiver as well as inertial measurement unit (IMU), camera, wireless sensor and odometer. GPS is not integrated into the system but treated as ground truth. Results are compared with the most common filtering?based fusion algorithm. It shows that our strategy can process low?quality input sources in a plug?and?play and robust manner and its performance outperforms filtering?based method in GNSS?denied environment.
2019, 36(2):205-213.
DOI: 10.16356/j.1005-1120.2019.02.003
Abstract:
The complexity of flight safety system is usually affected by a variety of uncertainties.The uncertainty of overall security situation of flight safety system are hardly determined. In this work, flight safety assessment index system is firstly established based on software hardware environment liveware management(SHELM) model. And flight safety assessment is also carried out with matter?element theory algorithm to obtain safety state. According to correlation degree values of each evaluation index, key indexes affected flight safety are obtained. Under the assumption that the flight safety system is a linear dynamic system and combining the above evaluation analysis, Kalman filter algorithm is used to carry out prediction analysis on security situation. A simulation analysis is carried out based on an actual flight safety situation of an airline. The results show that the security state of airline flight safety system in a short period of time can be obtained, and main factors affecting flight safety are found out. This provides a viable way for airlines to further strengthen flight safety management.
The complexity of flight safety system is usually affected by a variety of uncertainties.The uncertainty of overall security situation of flight safety system are hardly determined. In this work, flight safety assessment index system is firstly established based on software hardware environment liveware management(SHELM) model. And flight safety assessment is also carried out with matter?element theory algorithm to obtain safety state. According to correlation degree values of each evaluation index, key indexes affected flight safety are obtained. Under the assumption that the flight safety system is a linear dynamic system and combining the above evaluation analysis, Kalman filter algorithm is used to carry out prediction analysis on security situation. A simulation analysis is carried out based on an actual flight safety situation of an airline. The results show that the security state of airline flight safety system in a short period of time can be obtained, and main factors affecting flight safety are found out. This provides a viable way for airlines to further strengthen flight safety management.
2019, 36(2):214-223.
DOI: 10.16356/j.1005-1120.2019.02.004
Abstract:
A robust adaptive control scheme with prescribed performance is proposed for attitude maneuver and vibration suppression of flexible spacecraft, in which the parametric uncertainty, external disturbances and unmeasured elastic vibration are taken into account simultaneously. On the basis of the prescribed performance control (PPC) theory, the prescribed steady state and transient performance for the attitude tracking error can be guaranteed through the stabilization of the transformed system. This controller does not need the knowledge of modal variables. The absence of measurements of these variables is compensated by appropriate dynamics of the controller which supplies their estimates. The method of sliding mode differentiator is introduced to overcome the problem of explosion of complexity inherent in traditional backstepping design. In addition, the requirements of knowing the system parameters and the unknown bound of the lumped uncertainty, including external disturbance and the estimate error of sliding mode differentiator, have been eliminated by using adaptive updating technique. Within the framework of Lyapunov theory, the stability of the transformed system is obtained. Finally, numerical simulations are carried out to verify the effectiveness of the proposed control scheme.
A robust adaptive control scheme with prescribed performance is proposed for attitude maneuver and vibration suppression of flexible spacecraft, in which the parametric uncertainty, external disturbances and unmeasured elastic vibration are taken into account simultaneously. On the basis of the prescribed performance control (PPC) theory, the prescribed steady state and transient performance for the attitude tracking error can be guaranteed through the stabilization of the transformed system. This controller does not need the knowledge of modal variables. The absence of measurements of these variables is compensated by appropriate dynamics of the controller which supplies their estimates. The method of sliding mode differentiator is introduced to overcome the problem of explosion of complexity inherent in traditional backstepping design. In addition, the requirements of knowing the system parameters and the unknown bound of the lumped uncertainty, including external disturbance and the estimate error of sliding mode differentiator, have been eliminated by using adaptive updating technique. Within the framework of Lyapunov theory, the stability of the transformed system is obtained. Finally, numerical simulations are carried out to verify the effectiveness of the proposed control scheme.
2019, 36(2):224-231.
DOI: 10.16356/j.1005-1120.2019.02.005
Abstract:
The cooperative localization (CL) is affected by the communication topology among the platforms. Based on the unscented Kalman filtering, the distributed CL (DCL) oriented to the unpredicted communication topology is investigated. To improve the adaptability, the character of the look-up Cholesky decomposition is exploited for the covariance matrix decomposing. Then, the distributed U transformation can be dynamically implemented according to the available communication topology. In the proposed algorithm, the global information is not required for the individual, and only the available information from the neighbor is used. Each platform’s state can be estimated independently. The error covariance of the state estimates can be updated in the single platform. The algorithm is adaptive to any serial communication topologies where the measuring to the measured platform is a starting path. The applicability of the proposed algorithm to unpredicted communication topology is improved, remaining equivalent localization performance to free connection communication.
The cooperative localization (CL) is affected by the communication topology among the platforms. Based on the unscented Kalman filtering, the distributed CL (DCL) oriented to the unpredicted communication topology is investigated. To improve the adaptability, the character of the look-up Cholesky decomposition is exploited for the covariance matrix decomposing. Then, the distributed U transformation can be dynamically implemented according to the available communication topology. In the proposed algorithm, the global information is not required for the individual, and only the available information from the neighbor is used. Each platform’s state can be estimated independently. The error covariance of the state estimates can be updated in the single platform. The algorithm is adaptive to any serial communication topologies where the measuring to the measured platform is a starting path. The applicability of the proposed algorithm to unpredicted communication topology is improved, remaining equivalent localization performance to free connection communication.
2019, 36(2):232-241.
DOI: 10.16356/j.1005-1120.2019.02.006
Abstract:
The research on multiple launch rocket system (MLRS) is now even more demanding in terms of reducing the time for dynamic calculations and improving the firing accuracy, keeping the cost as low as possible. This study employs multibody system transfer matrix method (MSTMM), to model MLRS. The use of this method provides effective and fast calculations of dynamic characteristics, initial disturbance and firing accuracy. Further, a new method of rapid extrapolation of ballistic trajectory of MLRS is proposed by using the position information of radar tests. That extrapolation point is then simulated and compared with the actual results, which demonstrates a good agreement. The closed-loop fire correction method is used to improve the firing accuracy of MLRS at low cost.
The research on multiple launch rocket system (MLRS) is now even more demanding in terms of reducing the time for dynamic calculations and improving the firing accuracy, keeping the cost as low as possible. This study employs multibody system transfer matrix method (MSTMM), to model MLRS. The use of this method provides effective and fast calculations of dynamic characteristics, initial disturbance and firing accuracy. Further, a new method of rapid extrapolation of ballistic trajectory of MLRS is proposed by using the position information of radar tests. That extrapolation point is then simulated and compared with the actual results, which demonstrates a good agreement. The closed-loop fire correction method is used to improve the firing accuracy of MLRS at low cost.
2019, 36(2):242-252.
DOI: 10.16356/j.1005-1120.2019.02.007
Abstract:
This paper presents a constrained control strategy for the hypersonic vehicle with actuator amplitude, rate constraints and aerodynamic uncertainties. First, a vehicle?actuator control model is derived in consideration of actuator dynamics properties explicitly. Second, a nonlinear disturbance observer is designed to estimate the aerodynamic uncertainties, and then an adaptive backstepping control technique is adopted with a modified first?order?filter to eliminate the “explosion of terms” problem. Next, for handling the actuator amplitude and rate constraints, a novel auxiliary compensation system is constructed to generate quickly compensating signals to ensure tracking performance of command signal. By the Lyapunov stability proof, the proposed control scheme can enssure that the tracking errors converge to an arbitrarily small neighborhood around zero when the actuator constraints and aerodynamic uncertainties exist. Finally, numerical simulations are implemented to illustrate the effectiveness of the proposed control method.
This paper presents a constrained control strategy for the hypersonic vehicle with actuator amplitude, rate constraints and aerodynamic uncertainties. First, a vehicle?actuator control model is derived in consideration of actuator dynamics properties explicitly. Second, a nonlinear disturbance observer is designed to estimate the aerodynamic uncertainties, and then an adaptive backstepping control technique is adopted with a modified first?order?filter to eliminate the “explosion of terms” problem. Next, for handling the actuator amplitude and rate constraints, a novel auxiliary compensation system is constructed to generate quickly compensating signals to ensure tracking performance of command signal. By the Lyapunov stability proof, the proposed control scheme can enssure that the tracking errors converge to an arbitrarily small neighborhood around zero when the actuator constraints and aerodynamic uncertainties exist. Finally, numerical simulations are implemented to illustrate the effectiveness of the proposed control method.
2019, 36(2):253-263.
DOI: 10.16356/j.1005-1120.2019.02.008
Abstract:
With the great development of unmanned aircraft system (UAS) over the last decade, sense and avoid (SAA) system has been a crucial technology for integrating unmanned aircraft vehicle (UAV) into national airspace with reliable and safe operations. This paper mainly focuses on intruder detection for SAA system. A robust algorithm based on the combination of edge-boxes and spatial pyramid matching using sparse coding (sc-SPM) is presented. The algorithm is composed of three stages. First, edge?boxes method is adopted to obtain a large number of proposals; Second, the optimization program is presented to obtain intruder area-of-interest (ROI) regions; Third, sc-SPM is employed for feature representation of ROI regions and support vector machines (SVM) is adopted to detect the intruder. The algorithm is evaluated under different weather conditions. The recall reaches to 0.95 in dawn and sunny weather and 0.9 in cloudy weather. The experimental results indicate that the intruder detection algorithm is effective and robust with various weather under complex background.
With the great development of unmanned aircraft system (UAS) over the last decade, sense and avoid (SAA) system has been a crucial technology for integrating unmanned aircraft vehicle (UAV) into national airspace with reliable and safe operations. This paper mainly focuses on intruder detection for SAA system. A robust algorithm based on the combination of edge-boxes and spatial pyramid matching using sparse coding (sc-SPM) is presented. The algorithm is composed of three stages. First, edge?boxes method is adopted to obtain a large number of proposals; Second, the optimization program is presented to obtain intruder area-of-interest (ROI) regions; Third, sc-SPM is employed for feature representation of ROI regions and support vector machines (SVM) is adopted to detect the intruder. The algorithm is evaluated under different weather conditions. The recall reaches to 0.95 in dawn and sunny weather and 0.9 in cloudy weather. The experimental results indicate that the intruder detection algorithm is effective and robust with various weather under complex background.
2019, 36(2):264-279.
DOI: 10.16356/j.1005-1120.2019.02.009
Abstract:
To reduce the uncertainty and reworks in complex projects, a novel mechanism is systematically developed in this paper based on two classical design structure matrix (DSM) clustering methods Loop searching method (LSM) and function searching method (FSM). Specifically, the optimal working areas for the two clustering methods are first obtained quantitatively in terms of non?zero fraction (NZF) and singular value modularity index (SMI), in which the whole working area is divided into six sub?zones. Then, a judgement procedure is proposed for conveniently choosing the optimal DSM clustering method, which makes it easy to determine which DSM clustering method performs better for a given case. Subsequently, a conceptual model is constructed to assist project managers in effectively analyzing the network of projects and greatly reducing reworks in complex projects by defining preventive actions. Finally, the aircraft design process is presented to show how the proposed judgement mechanism can be utilized to reduce the reworks in actual projects.
To reduce the uncertainty and reworks in complex projects, a novel mechanism is systematically developed in this paper based on two classical design structure matrix (DSM) clustering methods Loop searching method (LSM) and function searching method (FSM). Specifically, the optimal working areas for the two clustering methods are first obtained quantitatively in terms of non?zero fraction (NZF) and singular value modularity index (SMI), in which the whole working area is divided into six sub?zones. Then, a judgement procedure is proposed for conveniently choosing the optimal DSM clustering method, which makes it easy to determine which DSM clustering method performs better for a given case. Subsequently, a conceptual model is constructed to assist project managers in effectively analyzing the network of projects and greatly reducing reworks in complex projects by defining preventive actions. Finally, the aircraft design process is presented to show how the proposed judgement mechanism can be utilized to reduce the reworks in actual projects.
2019, 36(2):280-289.
DOI: 10.16356/j.1005-1120.2019.02.010
Abstract:
The energy-saving and environmental protection industry has vast development space and huge market increment in China. Selecting appropriate energy?saving and environmental protection enterprises is one of the important decisions of venture capital investment. In the paper, a fuzzy bilateral boundary data envelopment analysis(DEA) model with optimistic coefficient is proposed to select those companies with high financing efficiencies. Based on the characteristics of enterprise financing, undesirable outputs and dual-role factors are considered in the proposed model. The results show that the fifth enterprise has high comprehensive financing efficiencies and always ranks the first when the optimistic coefficients are 0.2, 0.5 and 0.8, respectively. In addition, most energy?saving and environmental protection enterprises have not efficient financing efficiencies. There is still much space for improvement.
The energy-saving and environmental protection industry has vast development space and huge market increment in China. Selecting appropriate energy?saving and environmental protection enterprises is one of the important decisions of venture capital investment. In the paper, a fuzzy bilateral boundary data envelopment analysis(DEA) model with optimistic coefficient is proposed to select those companies with high financing efficiencies. Based on the characteristics of enterprise financing, undesirable outputs and dual-role factors are considered in the proposed model. The results show that the fifth enterprise has high comprehensive financing efficiencies and always ranks the first when the optimistic coefficients are 0.2, 0.5 and 0.8, respectively. In addition, most energy?saving and environmental protection enterprises have not efficient financing efficiencies. There is still much space for improvement.
2019, 36(2):290-297.
DOI: 10.16356/j.1005-1120.2019.02.011
Abstract:
The effect of interconnect linewidth on the evolution of intragranular microcracks due to surface diffusion induced by electromigration is analyzed by finite element method. The numerical results indicate that there exists critical values of the linewidth , the electric field and the aspect ratio . When , χ < χ c or β < β c , the microcrack will evolve into a stable shape as it migrates along the interconnect line. When , χ ≥ χ c or β ≥ β c , the microcrack will split into two smaller microcracks. The critical electric field, the critical aspect ratio and the splitting time have a stronger dependence on the linewidth when . In addition, the decrease of the linewidth, the increase of the electric field or the aspect ratio is beneficial to accelerate microcrack splitting, which may delay the open failure of the interconnect line.
The effect of interconnect linewidth on the evolution of intragranular microcracks due to surface diffusion induced by electromigration is analyzed by finite element method. The numerical results indicate that there exists critical values of the linewidth
12 Dimensional Variation Modeling of Aircraft Compliant Part Assembly Considering Clamping Force Change
2019, 36(2):298-305.
DOI: 10.16356/j.1005-1120.2019.02.012
Abstract:
Compliant parts are widely applied to aircraft structures. Due to the ease of deformation of compliant parts in assembly, the prediction of assembly variation is especially important for assembly quality control. A dimensional variation model considering the clamping force change in assembly is proposed based on the method of influence coefficient (MIC). First, the assembly process is decomposed into several steps including positioning, clamping, joining, and spring?back. Then, the force?displacement relationship is formulated according to the varied force conditions on the parts in each assembly step. Finally, two examples are illustrated to validate the proposed assembly variation model. The results show the impact of clamping force change is significant on the assembly variation, and the proposed model can predict the assembly variation more accurately than the referred method without clamping force correction at the over?constrained locating points of fixture.
Compliant parts are widely applied to aircraft structures. Due to the ease of deformation of compliant parts in assembly, the prediction of assembly variation is especially important for assembly quality control. A dimensional variation model considering the clamping force change in assembly is proposed based on the method of influence coefficient (MIC). First, the assembly process is decomposed into several steps including positioning, clamping, joining, and spring?back. Then, the force?displacement relationship is formulated according to the varied force conditions on the parts in each assembly step. Finally, two examples are illustrated to validate the proposed assembly variation model. The results show the impact of clamping force change is significant on the assembly variation, and the proposed model can predict the assembly variation more accurately than the referred method without clamping force correction at the over?constrained locating points of fixture.
2019, 36(2):306-312.
DOI: 10.16356/j.1005-1120.2019.02.013
Abstract:
An experiment for rocket engine inducer cavitating flow is conducted on a new experimental platform. The experiment platform, using water as working medium, can be used to investigate the steady and unsteady flows of cavitating and noncavitating turbopumps. The experimental platform is designed as a flexible and versatile apparatus for any kind of fluid dynamic phenomena relating to high performance liquid rocket engine turbopumps. Design details for the platform is introduced. Various extend of cavitation images and dynamic pressure impulse are obtained, which provides a reference for cavitating flow study in rocket engine inducer.
An experiment for rocket engine inducer cavitating flow is conducted on a new experimental platform. The experiment platform, using water as working medium, can be used to investigate the steady and unsteady flows of cavitating and noncavitating turbopumps. The experimental platform is designed as a flexible and versatile apparatus for any kind of fluid dynamic phenomena relating to high performance liquid rocket engine turbopumps. Design details for the platform is introduced. Various extend of cavitation images and dynamic pressure impulse are obtained, which provides a reference for cavitating flow study in rocket engine inducer.
2019, 36(2):313-319.
DOI: 10.16356/j.1005-1120.2019.02.014
Abstract:
Safety is the foundation of sustainable development in civil aviation. Although catastrophic accidents are rare, indicators of potential incidents and unsafe events frequently materialize. Therefore, a history of unsafe data are considered in predicting safety risks. A deep learning method is adopted for extracting reactions in safety risks. The deep neural network (DNN) model for safety risk prediction is shown to extract complex data characteristics better than a shallow network model. Using extended unsafe data and monthly risk indices, hidden layers and iterations are determined. The effectiveness of DNN is also revealed in comparison with the traditional neural network. Through early risk detection using the method in the paper, airlines and the government can mitigate potential risk and take proactive measures to improve civil aviation safety.
Safety is the foundation of sustainable development in civil aviation. Although catastrophic accidents are rare, indicators of potential incidents and unsafe events frequently materialize. Therefore, a history of unsafe data are considered in predicting safety risks. A deep learning method is adopted for extracting reactions in safety risks. The deep neural network (DNN) model for safety risk prediction is shown to extract complex data characteristics better than a shallow network model. Using extended unsafe data and monthly risk indices, hidden layers and iterations are determined. The effectiveness of DNN is also revealed in comparison with the traditional neural network. Through early risk detection using the method in the paper, airlines and the government can mitigate potential risk and take proactive measures to improve civil aviation safety.
2019, 36(2):320-329.
DOI: 10.16356/j.1005-1120.2019.02.015
Abstract:
To study the influences of phase change material (PCM) microcapsules in clothing on human thermal responses, a mathematical model is developed. The improved Stolwijk’s model is used to simulate human thermo-regulatory process, and the coupled heat and moisture transfer including the moisture sorption /desorption of fibers and effects of phase transition temperature range on the phase change processes of the PCM is considered in clothing model. Meanwhile, the theoretical predictions are validated by experimental data. Then, the interactions between human body thermal responses and the heat and moisture transfer in clothing are discussed by comparing the prediction results with PCMs and without PCMs. Also the effects of fiber hygroscopicity on clothing and human thermal responses are compared. The conclusion shows that the clothing with PCMs microcapsules can delay the human temperature variations and decrease the sweat accumulation rate on the skin surface and heat loss during changing of ambient conditions, and fiber hygroscopicity reduces the effect of PCM microcapsules on delaying garment temperature variations very significantly.
To study the influences of phase change material (PCM) microcapsules in clothing on human thermal responses, a mathematical model is developed. The improved Stolwijk’s model is used to simulate human thermo-regulatory process, and the coupled heat and moisture transfer including the moisture sorption /desorption of fibers and effects of phase transition temperature range on the phase change processes of the PCM is considered in clothing model. Meanwhile, the theoretical predictions are validated by experimental data. Then, the interactions between human body thermal responses and the heat and moisture transfer in clothing are discussed by comparing the prediction results with PCMs and without PCMs. Also the effects of fiber hygroscopicity on clothing and human thermal responses are compared. The conclusion shows that the clothing with PCMs microcapsules can delay the human temperature variations and decrease the sweat accumulation rate on the skin surface and heat loss during changing of ambient conditions, and fiber hygroscopicity reduces the effect of PCM microcapsules on delaying garment temperature variations very significantly.
2019, 36(2):330-338.
DOI: 10.16356/j.1005-1120.2019.02.016
Abstract:
The pneumatic muscle actuator (PMA) has many advantages, such as good flexibility, high power / weight ratio, but its nonlinearity makes it difficult to build a static mathematical model with high precision. A new method is proposed to establish the model of PMA. The concept of hybrid elastic modulus which is related to the static characteristic of PMA is put forward, and the energy conservation law is used to achieve the expression of the hybrid elastic modulus, which can be fitted out based on experimental data, and the model of PMA can be derived from this expression. At the same time, a 3-DOF parallel mechanism (a new bionic shoulder joint) driven by five PMAs is designed. This bionic shoulder joint adopts the structure of two antagonistic PMAs actualizing a rotation control and three PMAs controlling another two rotations to get better rotation characteristics. The kinematic and dynamic characteristics of the mechanism are analyzed and a new static model of PMA is used to control it. Experimental results demonstrate the effectiveness of this new static model.
The pneumatic muscle actuator (PMA) has many advantages, such as good flexibility, high power / weight ratio, but its nonlinearity makes it difficult to build a static mathematical model with high precision. A new method is proposed to establish the model of PMA. The concept of hybrid elastic modulus which is related to the static characteristic of PMA is put forward, and the energy conservation law is used to achieve the expression of the hybrid elastic modulus, which can be fitted out based on experimental data, and the model of PMA can be derived from this expression. At the same time, a 3-DOF parallel mechanism (a new bionic shoulder joint) driven by five PMAs is designed. This bionic shoulder joint adopts the structure of two antagonistic PMAs actualizing a rotation control and three PMAs controlling another two rotations to get better rotation characteristics. The kinematic and dynamic characteristics of the mechanism are analyzed and a new static model of PMA is used to control it. Experimental results demonstrate the effectiveness of this new static model.
2019, 36(2):341-351.
DOI: 10.16356/j.1005-1120.2019.02.017
Abstract:
A propagator-based algorithm for direction of arrival (DOA) estimation of noncoherent one-dimensional (1-D) non-circular sources is presented such as binary phase shift keying (BPSK) and amplitude modulation (AM). The algorithm achieves DOA estimation through searching a 1-D spectrum, which is newly formed on the basis of the rank reduction criterion, and works well without knowledge of the non-circular phases. And then, a search-free implementation of the algorithm is also developed by using the polynomial rooting technique. According to the non-circular property, the algorithm can virtually enlarge the array aperture, thus significantly improving its estimation accuracy and enabling it to handle more sources than the number of sensors. Moreover, the algorithm requires no rotational invariance, so it can be applied to arbitrary array geometry and dispense with the high-complexity procedure of the eigen-decomposition of the correlation sample matrix. Finally, numerical simulations verify the performance and effectiveness of the proposed algorithm.
A propagator-based algorithm for direction of arrival (DOA) estimation of noncoherent one-dimensional (1-D) non-circular sources is presented such as binary phase shift keying (BPSK) and amplitude modulation (AM). The algorithm achieves DOA estimation through searching a 1-D spectrum, which is newly formed on the basis of the rank reduction criterion, and works well without knowledge of the non-circular phases. And then, a search-free implementation of the algorithm is also developed by using the polynomial rooting technique. According to the non-circular property, the algorithm can virtually enlarge the array aperture, thus significantly improving its estimation accuracy and enabling it to handle more sources than the number of sensors. Moreover, the algorithm requires no rotational invariance, so it can be applied to arbitrary array geometry and dispense with the high-complexity procedure of the eigen-decomposition of the correlation sample matrix. Finally, numerical simulations verify the performance and effectiveness of the proposed algorithm.
2019, 36(2):352-360.
DOI: 10.16356/j.1005-1120.2019.02.018
Abstract:
It is an important issue to assess traffic situation complexity for air traffic management. There is a lack of systematic review of the existing air traffic complexity assessment methods, and there is no consideration of the role of airspace and traffic coordination mechanism. A new 3-D airspace complexity measurement method is proposed based on route structure constraints to evaluate the air traffic complexity objectively. Firstly, the model of the impact on horizontal and vertical direction for "aircraft pair" is established based on the route guidance. After that, the coupled complexity model for 3-D airspace is given according to the modification on the model in terms of flight standardization. Finally, the global model of the airspace traffic complexity is established. It is proved by the experimental data from the actual operation in airspace that the proposed model can reflect the space coupling situation and complexity of aircraft. At the same time, it can precisely describe the actual operation of civil aviation in China.
It is an important issue to assess traffic situation complexity for air traffic management. There is a lack of systematic review of the existing air traffic complexity assessment methods, and there is no consideration of the role of airspace and traffic coordination mechanism. A new 3-D airspace complexity measurement method is proposed based on route structure constraints to evaluate the air traffic complexity objectively. Firstly, the model of the impact on horizontal and vertical direction for "aircraft pair" is established based on the route guidance. After that, the coupled complexity model for 3-D airspace is given according to the modification on the model in terms of flight standardization. Finally, the global model of the airspace traffic complexity is established. It is proved by the experimental data from the actual operation in airspace that the proposed model can reflect the space coupling situation and complexity of aircraft. At the same time, it can precisely describe the actual operation of civil aviation in China.
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