The Ocean 4A scatterometer, expected to be launched in 2024, is poised to be the world’s first spaceborne microwave scatterometer utilizing a digital beamforming system. To ensure high-precision measurements and perf...The Ocean 4A scatterometer, expected to be launched in 2024, is poised to be the world’s first spaceborne microwave scatterometer utilizing a digital beamforming system. To ensure high-precision measurements and performance sta-bility across diverse environments, stringent requirements are placed on the dynamic range of its receiving system. This paper provides a detailed exposition of a field-programmable gate array (FPGA)-based automatic gain control (AGC) design for the spaceborne scatterometer. Implemented on an FPGA, the algo-rithm harnesses its parallel processing capabilities and high-speed performance to monitor the received echo signals in real time. Employing an adaptive AGC algorithm, the system gene-rates gain control codes applicable to the intermediate fre-quency variable attenuator, enabling rapid and stable adjust-ment of signal amplitudes from the intermediate frequency amplifier to an optimal range. By adopting a purely digital pro-cessing approach, experimental results demonstrate that the AGC algorithm exhibits several advantages, including fast con-vergence, strong flexibility, high precision, and outstanding sta-bility. This innovative design lays a solid foundation for the high-precision measurements of the Ocean 4A scatterometer, with potential implications for the future of spaceborne microwave scatterometers.展开更多
An agile missile with tail fins and pulse thrusters has continuous and discontinuous control inputs.This brings certain difficulty to the autopilot design and stability analysis.Indirect robust control via Theta-D tec...An agile missile with tail fins and pulse thrusters has continuous and discontinuous control inputs.This brings certain difficulty to the autopilot design and stability analysis.Indirect robust control via Theta-D technique is employed to handle this problem.An acceleration tracking system is formulated based on the nonlinear dynamics of agile missile.Considering the dynamics of actuators,there is an error between actual input and computed input.A robust control problem is formed by treating the error as input uncertainty.The robust control is equivalent to a nonlinear quadratic optimal control of the nominal system with a modified performance index including uncertainty bound.Theta-D technique is applied to solve the nonlinear optimal control problem to obtain the final control law.Numerical results show the effectiveness and robustness of the proposed strategy.展开更多
A CMOS active mixer based on voltage control load technique which can operate at 1.0 V supply voltage was proposed, and its operation principle, noise and linearity analysis were also presented. Contrary to the conven...A CMOS active mixer based on voltage control load technique which can operate at 1.0 V supply voltage was proposed, and its operation principle, noise and linearity analysis were also presented. Contrary to the conventional Gilbert-type mixer which is based on RF current-commutating, the load impedance in this proposed mixer is controlled by the LO signal, and it has only two stacked transistors at each branch which is suitable for low voltage applications. The mixer was designed and fabricated in 0.18 tam CMOS process for 2.4 GHz ISM band applications. With an input of 2.44 GHz RF signal and 2.442 GHz LO signal, the measurement specifications of the proposed mixer are： the conversion gain （Gc） is 5.3 dB, the input-referred third-order intercept point （PIIP3） is 4.6 dBm, the input-referred 1 dB compression point （P1dB） is --7.4 dBm, and the single-sideband noise figure （NFSSB） is 21.7 dB.展开更多
A principle of fuzzy control for tracked vehicles is proposed to make its automatic transmission system be able to adapt complex running conditions, and a model of its power train is established to be used in simulati...A principle of fuzzy control for tracked vehicles is proposed to make its automatic transmission system be able to adapt complex running conditions, and a model of its power train is established to be used in simulation. Based on the fuzzy control method, a fuzzy shift control system composed of a basic shift strategy and a fuzzy modification module is developed to improve the dynamic characteristics and cross-country maneuverability. Simulation results show that the fuzzy shift strategy can improve the shift quality under manifold driving conditions and avoid cycled shift effectively.Therefore, the proposed fuzzy shift strategies are proved to be feasible and practicable.展开更多
The automatic chain shell magazine is the primary subassembly of the automatic ammunition loading system of a big-caliber howitzer. Due to the change of the shell amount in the magazine during firing, its positioning ...The automatic chain shell magazine is the primary subassembly of the automatic ammunition loading system of a big-caliber howitzer. Due to the change of the shell amount in the magazine during firing, its positioning control is a kind of control problem of systems with uncertain parameters. In order to realize accurate control of shell position, an optimal guaranteed cost control algorithm based on linear matrix inequality (LMI) theory was put forward. The motion equations of the magazine were built, and the motion equations for four special load situations were linearized; according to the basic theory of the guaranteed cost control, the motion equations were written as the standard forms for linear uncertain systems; the optimal guaranteed cost control law for the position control of the magazine was obtained by use of LMI toolbox in MATLAB package. Using this control law, the controlled dynamic simulation of the shell magazine was carried out. The simulation results indicate that the control algorithm has high control precision.展开更多
According to the production index of lint cotton yield over 100kg per mu(1/15ha)and the relationship between the climate factors and the distribution of time and space for cottonboll setting in 1985—1990,we establish...According to the production index of lint cotton yield over 100kg per mu(1/15ha)and the relationship between the climate factors and the distribution of time and space for cottonboll setting in 1985—1990,we established a model of cultural techniques of cotton leaf-age-ad-justing-controlling for enhancing early maturity.By utilizing the principle of leaf-age model andthe principle of regulating nutrient distribution with DPC(Mepiquate chloride),the plants weretreated with DPC in proper time.A new type of population plant patterns was set up.It character-ized by high population density,dwarf,high boll weight,bolls near nodes,high energy and lowconsumption,short distance transport of nutrients,high yield and good quality.We put forward aset of management measures,i.e.adjusting boll setting stage,adjusting and controlling boll set-ting structure,stably applying N,increasing P,supplementing plants with K,increasing irrigationefficiency,techniques were applied and demonstrated in large areas in high yield展开更多
文摘The Ocean 4A scatterometer, expected to be launched in 2024, is poised to be the world’s first spaceborne microwave scatterometer utilizing a digital beamforming system. To ensure high-precision measurements and performance sta-bility across diverse environments, stringent requirements are placed on the dynamic range of its receiving system. This paper provides a detailed exposition of a field-programmable gate array (FPGA)-based automatic gain control (AGC) design for the spaceborne scatterometer. Implemented on an FPGA, the algo-rithm harnesses its parallel processing capabilities and high-speed performance to monitor the received echo signals in real time. Employing an adaptive AGC algorithm, the system gene-rates gain control codes applicable to the intermediate fre-quency variable attenuator, enabling rapid and stable adjust-ment of signal amplitudes from the intermediate frequency amplifier to an optimal range. By adopting a purely digital pro-cessing approach, experimental results demonstrate that the AGC algorithm exhibits several advantages, including fast con-vergence, strong flexibility, high precision, and outstanding sta-bility. This innovative design lays a solid foundation for the high-precision measurements of the Ocean 4A scatterometer, with potential implications for the future of spaceborne microwave scatterometers.
基金supported by the National Natural Science Foundation of China(61174203)Aeronautical Science Foundation of China(20110177002)
文摘An agile missile with tail fins and pulse thrusters has continuous and discontinuous control inputs.This brings certain difficulty to the autopilot design and stability analysis.Indirect robust control via Theta-D technique is employed to handle this problem.An acceleration tracking system is formulated based on the nonlinear dynamics of agile missile.Considering the dynamics of actuators,there is an error between actual input and computed input.A robust control problem is formed by treating the error as input uncertainty.The robust control is equivalent to a nonlinear quadratic optimal control of the nominal system with a modified performance index including uncertainty bound.Theta-D technique is applied to solve the nonlinear optimal control problem to obtain the final control law.Numerical results show the effectiveness and robustness of the proposed strategy.
基金Project(61166004) supported by the National Natural Science Foundation of ChinaProject(09ZCGHHZ00200) supported by the International Scientific and Technological Cooperation Program of Science and Technology Plan of Tianjin,ChinaProject(UF10028Y)supported by the Doctoral Scientific Research Foundation for Guilin University of Electronic Technology,China
文摘A CMOS active mixer based on voltage control load technique which can operate at 1.0 V supply voltage was proposed, and its operation principle, noise and linearity analysis were also presented. Contrary to the conventional Gilbert-type mixer which is based on RF current-commutating, the load impedance in this proposed mixer is controlled by the LO signal, and it has only two stacked transistors at each branch which is suitable for low voltage applications. The mixer was designed and fabricated in 0.18 tam CMOS process for 2.4 GHz ISM band applications. With an input of 2.44 GHz RF signal and 2.442 GHz LO signal, the measurement specifications of the proposed mixer are： the conversion gain （Gc） is 5.3 dB, the input-referred third-order intercept point （PIIP3） is 4.6 dBm, the input-referred 1 dB compression point （P1dB） is --7.4 dBm, and the single-sideband noise figure （NFSSB） is 21.7 dB.
基金Sponsored by National Key Lab Foundation of Vehicular Transmission of China(51457070105j w0514)
文摘A principle of fuzzy control for tracked vehicles is proposed to make its automatic transmission system be able to adapt complex running conditions, and a model of its power train is established to be used in simulation. Based on the fuzzy control method, a fuzzy shift control system composed of a basic shift strategy and a fuzzy modification module is developed to improve the dynamic characteristics and cross-country maneuverability. Simulation results show that the fuzzy shift strategy can improve the shift quality under manifold driving conditions and avoid cycled shift effectively.Therefore, the proposed fuzzy shift strategies are proved to be feasible and practicable.
文摘The automatic chain shell magazine is the primary subassembly of the automatic ammunition loading system of a big-caliber howitzer. Due to the change of the shell amount in the magazine during firing, its positioning control is a kind of control problem of systems with uncertain parameters. In order to realize accurate control of shell position, an optimal guaranteed cost control algorithm based on linear matrix inequality (LMI) theory was put forward. The motion equations of the magazine were built, and the motion equations for four special load situations were linearized; according to the basic theory of the guaranteed cost control, the motion equations were written as the standard forms for linear uncertain systems; the optimal guaranteed cost control law for the position control of the magazine was obtained by use of LMI toolbox in MATLAB package. Using this control law, the controlled dynamic simulation of the shell magazine was carried out. The simulation results indicate that the control algorithm has high control precision.
文摘According to the production index of lint cotton yield over 100kg per mu(1/15ha)and the relationship between the climate factors and the distribution of time and space for cottonboll setting in 1985—1990,we established a model of cultural techniques of cotton leaf-age-ad-justing-controlling for enhancing early maturity.By utilizing the principle of leaf-age model andthe principle of regulating nutrient distribution with DPC(Mepiquate chloride),the plants weretreated with DPC in proper time.A new type of population plant patterns was set up.It character-ized by high population density,dwarf,high boll weight,bolls near nodes,high energy and lowconsumption,short distance transport of nutrients,high yield and good quality.We put forward aset of management measures,i.e.adjusting boll setting stage,adjusting and controlling boll set-ting structure,stably applying N,increasing P,supplementing plants with K,increasing irrigationefficiency,techniques were applied and demonstrated in large areas in high yield
