Ion cyclotron wave resonance heating(ICRH) is one of the most important auxiliary methods to heat plasma in the Experimental Advanced Superconducting Tokamak(EAST). Several megawatts of power is transmitted through se...Ion cyclotron wave resonance heating(ICRH) is one of the most important auxiliary methods to heat plasma in the Experimental Advanced Superconducting Tokamak(EAST). Several megawatts of power is transmitted through separate coaxial lines and coupled with the plasma through arrays of loop antennas. The parameters of the ICRH system, including the injected power and phasing between antenna straps, are critical to the coupling efficiency of the power as well as the resulting impact on the heating efficiency. In this paper, we present a system for feedback control of the phase between the current straps and the ICRH power on EAST. The feedback control system was tested using both a matched dummy load and a plasma load, and it successfully maintained stable operation in the 2016 EAST campaign. Good control of the injected power and wave phases was achieved during edgelocalized mode operation.展开更多
In this paper, an output-feedback tracking controller is proposed for a class of nonlinear non-minimum phase systems.To keep the unstable internal dynamics bounded, the method of output redefinition is applied to let ...In this paper, an output-feedback tracking controller is proposed for a class of nonlinear non-minimum phase systems.To keep the unstable internal dynamics bounded, the method of output redefinition is applied to let the stability of the internal dynamics depend on that of redefined output, thus we only need to consider the new external dynamics rather than internal dynamics in the process of designing control law. To overcome the explosion of complexity problem in traditional backstepping design, the dynamic surface control(DSC) method is firstly used to deal with the problem of tracking control for the nonlinear non-minimum phase systems. The proposed outputfeedback DSC controller not only forces the system output to asymptotically track the desired trajectory, but also drives the unstable internal dynamics to follow its corresponding bounded and causal ideal internal dynamics, which is solved via stable system center method. Simulation results illustrate the validity of the proposed output-feedback DSC controller.展开更多
Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate ...Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.展开更多
The laser output characteristics under elliptically polarized optical feedback effect are studied. Elliptically polarized light is generated by wave plate placed in the feedback cavity. By analyzing the amplitude and ...The laser output characteristics under elliptically polarized optical feedback effect are studied. Elliptically polarized light is generated by wave plate placed in the feedback cavity. By analyzing the amplitude and phase of the laser output in the orthogonal direction, some new phenomena are firstly discovered and explained theoretically.Elliptically polarized feedback light is amplified in the gain medium in the resonator, and the direction perpendicular to the original polarization direction is easiest to oscillate. The laser intensity variation in amplitude and phase are related to the amplified mode and the anisotropy of external cavity. The theoretical analysis and experimental results agree well. Because the output characteristic of the laser has a relationship with the anisotropy of the external cavity, the phenomenon also provides a method for measuring birefringence.展开更多
The voltage controlled oscillator-based （VCO-based） continuous-time delta-sigma （CTDS） analog to digital converter （ADC） suffers from nonlinearity and mismatch in its feedback network. A new feedback network con...The voltage controlled oscillator-based （VCO-based） continuous-time delta-sigma （CTDS） analog to digital converter （ADC） suffers from nonlinearity and mismatch in its feedback network. A new feedback network consisting of a phase shifter is proposed. The phase shifter replaces the digital to analog converter （DAC） in the proposed architecture. Feasibility of the proposed idea is discussed and its higher performance is illustrated through a behavioral simulation approach （CppSim）. We have also developed the phase shifter as a variable all-pass filter in the C language. The nonlinearity and mismatch of the system caused by DAC is mitigated, resulting in higher signal to noise ratio （SNR） and signal to noise and distortion ratio （SNDR）, respectively.展开更多
It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power ...It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power but also its grill phase shift. This paper presents a new kind of feedback control system for antenna phase difference in LHCD experiments. In this highspeed control system, a lot of new technologies and methods are incorporated. The results of the experiments show a very good agreement with the system design.展开更多
Radar leveling system is the key equipment for improving the radar mobility and survival capability. A combined quantitative feedback theory (QFT) controller is designed for the radar truck leveling simulator in this ...Radar leveling system is the key equipment for improving the radar mobility and survival capability. A combined quantitative feedback theory (QFT) controller is designed for the radar truck leveling simulator in this paper, which suffers from strong nonlinearities and system parameter uncertainties. QFT can reduce the plant uncertainties and stabilize the system, but it fails to obtain high-precision tracking. This drawback can be solved by a robust QFT control scheme based on zero phase error tracking control (ZPETC) compensation. The combined controller not only possesses high robustness, but greatly improves the system performance. To verify the effiectiveness and the potential of the proposed controller, a series of experiments have been carried out. Experimental results have demonstrated its robustness against a large range of parameters variation and high tracking precision performance, as well as its capability of restraining the load coupling among channels. The combined QFT controller can drive the radar truck leveling platform accurately, quickly and stably.展开更多
Differential detection of continuous phase modulation suffers from significant intersymbol interference. To reduce bit error rate, multi-branch fractional multi-bit differential detection (MFMDD) with decision feed-ba...Differential detection of continuous phase modulation suffers from significant intersymbol interference. To reduce bit error rate, multi-branch fractional multi-bit differential detection (MFMDD) with decision feed-back is proposed. By introducing decision feedback in multi-bit differential detected signals, severe inter-symbol interference can be removed. Simulation results show that the proposed structure can greatly im-proves the performance compared with MFMDD without decision feedback, and the performance of 9 FMDD is very near to the performance of the coherent detection.展开更多
An M/G/1 retrial queue with two-phase service and feedback is studied in this paper, where the server is subject to starting failures and breakdowns during service. Primary customers get in the system according to a P...An M/G/1 retrial queue with two-phase service and feedback is studied in this paper, where the server is subject to starting failures and breakdowns during service. Primary customers get in the system according to a Poisson process, and they will receive service immediately if the server is available upon arrival. Otherwise, they will enter a retrial orbit and are queued in the orbit in accordance with a first-come-first-served （FCFS） discipline. Customers are allowed to balk and renege at particular times. All customers demand the first “essential” service, whereas only some of them demand the second “multi-optional” service. It is assumed that the retrial time, service time and repair time of the server are all arbitrarily distributed. The necessary and sufficient condition for the system stability is derived. Using a supplementary variable method, the steady-state solutions for some queueing and reliability measures of the system are obtained.展开更多
Efficiency and emissions of spark-ignited engines are significantly affected by combustion phase which can usually be indicated by crank angle of 50% mass burnt （CA50）. Managing combustion phase at the optimal value...Efficiency and emissions of spark-ignited engines are significantly affected by combustion phase which can usually be indicated by crank angle of 50% mass burnt （CA50）. Managing combustion phase at the optimal value at which the maximal efficiency can be achieved is a challenging issue due to the cyclic variations of combustion process. This paper addresses this issue in two loops： CA50 set-point optimization （outer loop） and set-point tracking （inner loop） by controlling spark advance （SA）. Extremum seeking approach maximizing thermal efficiency is employed in the CA50 set-point optimization. A proportional- integral （PI） controller is adopted to make the moving average value of CA50 tracking the optimal CA50 set-point determined in the outer loop. Moreover, in order to obtain fast responses at steady and transient operations, feed-forward maps are designed for extremum seeking controller and PI controller, respectively. Finally, experimental validations are conducted on a six-cylinder gasoline at steady and transient operations to show the effectiveness of proposed control scheme.展开更多
To improve the robustness of high-precision servo systems, quantitative feedback theory （QFT） which aims to achieve a desired robust design over a specified region of plant uncertainty is proposed. The robust design...To improve the robustness of high-precision servo systems, quantitative feedback theory （QFT） which aims to achieve a desired robust design over a specified region of plant uncertainty is proposed. The robust design problem can be solved using QFT but it fails to guarantee a high precision tracking. This problem is solved by a robust digital QFT control scheme based on zero phase error （ZPE） feed forward compensation. This scheme consists of two parts： a QFT controller in the closed-loop system and a ZPE feed-forward compensator. Digital QFT controller is designed to overcome the uncertainties in the system. Digital ZPE feed forward controller is used to improve the tracking precision. Simulation and real-time examples for flight simulator servo system indicate that this control scheme can guarantee both high robust performance and high position tracking precision.展开更多
A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes wi...A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated.展开更多
A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation funct...A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation function. Compared with the piecewise-linear map, this map provides enhanced security in that they can maintain the original perfect statistical properties, as well as overcome the defect of piecewise-linearity and expand the key space. This paper presents a scheme to improve the local complexity of the chaotic stream cipher based on the piecewise-quadratic-equationmap. Both the theoretic analysis and the results of simulation show that this scheme improves the microstructure of the phase-space graph on condition that the good properties of the original scheme are remained.展开更多
This paper demonstrates wide-band CMOS VCO based on the transformer feedback from traditional circuit to our proposed work. The start up condition of the traditional cross-coupled pair is expressed by the high frequen...This paper demonstrates wide-band CMOS VCO based on the transformer feedback from traditional circuit to our proposed work. The start up condition of the traditional cross-coupled pair is expressed by the high frequency model. The wide band technique of this structure is derived with the help of the high frequency model of the transistor. Therefore, the wide band CMOS VCO based on the common source transformer feedback topology can achieves the high performance in the low voltage and low phase noise. The measurement result of the VCO exhibits the figure of merit, core power consumption and output power at supply voltage 0.8 V are –193.1 dBc/Hz, 4.4 mW and –2.3 dBm, respectively. The phase noise is –124.3 dBc/Hz at 1 MHz offset under the operation frequency 5.8 GHz. And the tuning range of the circuit can obtain 28%, this VCO is fabricated in TSMC 0.18 μm 1P6MCMOS process.展开更多
基金supported in part by the National Magnetic Confinement Fusion Science Program(No.2015GB101001)the National Natural Science Foundation of China(Nos.11375236 and11375235)
文摘Ion cyclotron wave resonance heating(ICRH) is one of the most important auxiliary methods to heat plasma in the Experimental Advanced Superconducting Tokamak(EAST). Several megawatts of power is transmitted through separate coaxial lines and coupled with the plasma through arrays of loop antennas. The parameters of the ICRH system, including the injected power and phasing between antenna straps, are critical to the coupling efficiency of the power as well as the resulting impact on the heating efficiency. In this paper, we present a system for feedback control of the phase between the current straps and the ICRH power on EAST. The feedback control system was tested using both a matched dummy load and a plasma load, and it successfully maintained stable operation in the 2016 EAST campaign. Good control of the injected power and wave phases was achieved during edgelocalized mode operation.
基金supported by National Natural Science Foundation of China(61403013)the Aero-Science Foundation of China(2015ZA51009)
文摘In this paper, an output-feedback tracking controller is proposed for a class of nonlinear non-minimum phase systems.To keep the unstable internal dynamics bounded, the method of output redefinition is applied to let the stability of the internal dynamics depend on that of redefined output, thus we only need to consider the new external dynamics rather than internal dynamics in the process of designing control law. To overcome the explosion of complexity problem in traditional backstepping design, the dynamic surface control(DSC) method is firstly used to deal with the problem of tracking control for the nonlinear non-minimum phase systems. The proposed outputfeedback DSC controller not only forces the system output to asymptotically track the desired trajectory, but also drives the unstable internal dynamics to follow its corresponding bounded and causal ideal internal dynamics, which is solved via stable system center method. Simulation results illustrate the validity of the proposed output-feedback DSC controller.
基金supported by the National Natural Science Foundation of China (Grant Nos.60573172 and 60973152)the Doctoral Program Foundation of Institution of Higher Education of China (Grant No.20070141014)the Natural Science Foundation of Liaoning Province,China (Grant No.20082165)
文摘Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.
基金Supported by the Program for Changjiang Scholars and Innovative Research Team in University under Grant No IRT160R7
文摘The laser output characteristics under elliptically polarized optical feedback effect are studied. Elliptically polarized light is generated by wave plate placed in the feedback cavity. By analyzing the amplitude and phase of the laser output in the orthogonal direction, some new phenomena are firstly discovered and explained theoretically.Elliptically polarized feedback light is amplified in the gain medium in the resonator, and the direction perpendicular to the original polarization direction is easiest to oscillate. The laser intensity variation in amplitude and phase are related to the amplified mode and the anisotropy of external cavity. The theoretical analysis and experimental results agree well. Because the output characteristic of the laser has a relationship with the anisotropy of the external cavity, the phenomenon also provides a method for measuring birefringence.
基金supported by Iran Telecommunication Research Center under Grant No. 4222/500
文摘The voltage controlled oscillator-based （VCO-based） continuous-time delta-sigma （CTDS） analog to digital converter （ADC） suffers from nonlinearity and mismatch in its feedback network. A new feedback network consisting of a phase shifter is proposed. The phase shifter replaces the digital to analog converter （DAC） in the proposed architecture. Feasibility of the proposed idea is discussed and its higher performance is illustrated through a behavioral simulation approach （CppSim）. We have also developed the phase shifter as a variable all-pass filter in the C language. The nonlinearity and mismatch of the system caused by DAC is mitigated, resulting in higher signal to noise ratio （SNR） and signal to noise and distortion ratio （SNDR）, respectively.
基金Meg-science Engineering Project of the Chinese Academy of Sciences
文摘It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power but also its grill phase shift. This paper presents a new kind of feedback control system for antenna phase difference in LHCD experiments. In this highspeed control system, a lot of new technologies and methods are incorporated. The results of the experiments show a very good agreement with the system design.
文摘Radar leveling system is the key equipment for improving the radar mobility and survival capability. A combined quantitative feedback theory (QFT) controller is designed for the radar truck leveling simulator in this paper, which suffers from strong nonlinearities and system parameter uncertainties. QFT can reduce the plant uncertainties and stabilize the system, but it fails to obtain high-precision tracking. This drawback can be solved by a robust QFT control scheme based on zero phase error tracking control (ZPETC) compensation. The combined controller not only possesses high robustness, but greatly improves the system performance. To verify the effiectiveness and the potential of the proposed controller, a series of experiments have been carried out. Experimental results have demonstrated its robustness against a large range of parameters variation and high tracking precision performance, as well as its capability of restraining the load coupling among channels. The combined QFT controller can drive the radar truck leveling platform accurately, quickly and stably.
文摘Differential detection of continuous phase modulation suffers from significant intersymbol interference. To reduce bit error rate, multi-branch fractional multi-bit differential detection (MFMDD) with decision feed-back is proposed. By introducing decision feedback in multi-bit differential detected signals, severe inter-symbol interference can be removed. Simulation results show that the proposed structure can greatly im-proves the performance compared with MFMDD without decision feedback, and the performance of 9 FMDD is very near to the performance of the coherent detection.
基金Research sponsored by BJTU Research Foundation (2005SM064),the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Education Ministry and the National Natural Science Foundation of China (10526004,60504016).
文摘An M/G/1 retrial queue with two-phase service and feedback is studied in this paper, where the server is subject to starting failures and breakdowns during service. Primary customers get in the system according to a Poisson process, and they will receive service immediately if the server is available upon arrival. Otherwise, they will enter a retrial orbit and are queued in the orbit in accordance with a first-come-first-served （FCFS） discipline. Customers are allowed to balk and renege at particular times. All customers demand the first “essential” service, whereas only some of them demand the second “multi-optional” service. It is assumed that the retrial time, service time and repair time of the server are all arbitrarily distributed. The necessary and sufficient condition for the system stability is derived. Using a supplementary variable method, the steady-state solutions for some queueing and reliability measures of the system are obtained.
文摘Efficiency and emissions of spark-ignited engines are significantly affected by combustion phase which can usually be indicated by crank angle of 50% mass burnt （CA50）. Managing combustion phase at the optimal value at which the maximal efficiency can be achieved is a challenging issue due to the cyclic variations of combustion process. This paper addresses this issue in two loops： CA50 set-point optimization （outer loop） and set-point tracking （inner loop） by controlling spark advance （SA）. Extremum seeking approach maximizing thermal efficiency is employed in the CA50 set-point optimization. A proportional- integral （PI） controller is adopted to make the moving average value of CA50 tracking the optimal CA50 set-point determined in the outer loop. Moreover, in order to obtain fast responses at steady and transient operations, feed-forward maps are designed for extremum seeking controller and PI controller, respectively. Finally, experimental validations are conducted on a six-cylinder gasoline at steady and transient operations to show the effectiveness of proposed control scheme.
基金This project was supported by the Aeronautics Foundation of China (00E51022).
文摘To improve the robustness of high-precision servo systems, quantitative feedback theory （QFT） which aims to achieve a desired robust design over a specified region of plant uncertainty is proposed. The robust design problem can be solved using QFT but it fails to guarantee a high precision tracking. This problem is solved by a robust digital QFT control scheme based on zero phase error （ZPE） feed forward compensation. This scheme consists of two parts： a QFT controller in the closed-loop system and a ZPE feed-forward compensator. Digital QFT controller is designed to overcome the uncertainties in the system. Digital ZPE feed forward controller is used to improve the tracking precision. Simulation and real-time examples for flight simulator servo system indicate that this control scheme can guarantee both high robust performance and high position tracking precision.
基金Project supported by the Natural Science Foundation of Beijing,China(Grant No.3091002)
文摘A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated.
文摘A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation function. Compared with the piecewise-linear map, this map provides enhanced security in that they can maintain the original perfect statistical properties, as well as overcome the defect of piecewise-linearity and expand the key space. This paper presents a scheme to improve the local complexity of the chaotic stream cipher based on the piecewise-quadratic-equationmap. Both the theoretic analysis and the results of simulation show that this scheme improves the microstructure of the phase-space graph on condition that the good properties of the original scheme are remained.
文摘This paper demonstrates wide-band CMOS VCO based on the transformer feedback from traditional circuit to our proposed work. The start up condition of the traditional cross-coupled pair is expressed by the high frequency model. The wide band technique of this structure is derived with the help of the high frequency model of the transistor. Therefore, the wide band CMOS VCO based on the common source transformer feedback topology can achieves the high performance in the low voltage and low phase noise. The measurement result of the VCO exhibits the figure of merit, core power consumption and output power at supply voltage 0.8 V are –193.1 dBc/Hz, 4.4 mW and –2.3 dBm, respectively. The phase noise is –124.3 dBc/Hz at 1 MHz offset under the operation frequency 5.8 GHz. And the tuning range of the circuit can obtain 28%, this VCO is fabricated in TSMC 0.18 μm 1P6MCMOS process.
