The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo m...The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching.In this work,an imaging simulation method consid-ering the attitude jitter is presented.The impact analysis of different attitude jitter on terrain undulation is conduct-ed by simulating jitter at three attitude angles,respectively.The proposed simulation method is based on the rigor-ous sensor model,using the lunar digital elevation model(DEM)and orthoimage as reference data.The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter.Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit.Experi-mental analyses were conducted by the DEM with the simulated stereo image.The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping.The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.展开更多
A fast-locking, low-jitter, phase-locked loop （PLL） with a simple phase-frequency detector is proposed. The phase-frequency detector is composed of only two XOR gates. It simultaneously achieves low jitter and short...A fast-locking, low-jitter, phase-locked loop （PLL） with a simple phase-frequency detector is proposed. The phase-frequency detector is composed of only two XOR gates. It simultaneously achieves low jitter and short locking time. The voltage-controlled oscillator within the PLL consists of four-stage ring oscillators which are coupled to each other and oscillate with the same frequency and a phase shift of 45. The PLL is fabricated in 0. 1Stem CMOS technology. The measured phase noise of the PLL output at 500kHz offset from the 5GHz center frequency is - 102.6dBc/Hz. The circuit exhibits a capture range of 280MHz and a low RMS jitter of 2.06ps. The power dissipation excluding the output buffers is only 21.6roW at a 1.8V supply.展开更多
By jitter performance comparison between PLL (Phase Locked Loop) and DLL (Delay Locked Loop),a helpful equation is derived for the structure choice between DLL and PLL based synthesizers fabricated in CMOS processes ...By jitter performance comparison between PLL (Phase Locked Loop) and DLL (Delay Locked Loop),a helpful equation is derived for the structure choice between DLL and PLL based synthesizers fabricated in CMOS processes to get an optimum jitter performance and power consumption.For a frequency synthesizer,a large multiple factor prefers PLL based configuration which consumes less power,while a small one needs DLL based topology which produces a better jitter performance.展开更多
This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to...This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.展开更多
A fully integrated frequency synthesizer with low jitter and low power consumption in 0.18 μm CMOS (complementary metal-oxide semiconductor) technology is proposed in this paper.The frequency synthesizer uses a novel...A fully integrated frequency synthesizer with low jitter and low power consumption in 0.18 μm CMOS (complementary metal-oxide semiconductor) technology is proposed in this paper.The frequency synthesizer uses a novel single-end gain-boosting charge pump, a differential coupled voltage controlled oscillator (VCO) and a dynamic logic phase/frequency detecor (PFD) to acquire low output jitter.The output frequency range of the frequency synthesizer is up to 1 200 MHz to 1 400 MHz for GPS (global position system) application.The post simulation results show that the phase noise of VCO is only 127.1 dBc/Hz at a 1 MHz offset and the Vp-p jitter of the frequency synthesizer output clock is 13.65 ps.The power consumption of the frequency synthesizer not including the divider is 4.8 mW for 1.8 V supply and it occupies a 0.8 mm×0.7 mm chip area.展开更多
Faults and failures of induction machines can indeed lead to excessive costs, hence, there is a strong demand in the industry for adopting diagnosis techniques to assess and evaluate current condition of electrical ma...Faults and failures of induction machines can indeed lead to excessive costs, hence, there is a strong demand in the industry for adopting diagnosis techniques to assess and evaluate current condition of electrical machines. Eccentricity related faults as well as clutch wobbling constitute major portions of the faults related to induction motors. This paper presents the effect of clutch wobbling and mixed eccentricity on induction machine stator currents and the possibility of distinguishing between each ailment via comparing the abnormal harmonics contained in stator current spectrums in each case. In this paper, the current spectrum of a four pole-pairs, 550 kW, induction machine were calculated for the cases of full symmetry, clutch wobbling, and mixed eccentricity. The calculations involve integration of 93 electrical plus four mechanical ordinary differential equations. Electrical equations account for variable inductances affected by slotting and eccentricities. The calculations were followed by Fourier analysis of the stator currents. Zooms of the current spectrums, around the 50 Hz fundamental harmonic as well as of the main slot harmonic zone, of both calculated and measured currents are included. The spectrums presented in this paper rely on calculations that are performed with dedicated software which is owned by AGH University of Science and Technology.展开更多
Tail buffeting at high angle of attack causes distinct fatigue problem on tail structure of twin tail fighters.In this study,a piezoelectric active control experiment of tail buffeting was performed in a wind tunnel u...Tail buffeting at high angle of attack causes distinct fatigue problem on tail structure of twin tail fighters.In this study,a piezoelectric active control experiment of tail buffeting was performed in a wind tunnel using arching PZT actuator(APA) and principal modal control(PMC) method.Test results showed the peak value of power spectral density(PSD) function of tail buffeting acceleration response could be suppressed by about 42% when the angle of attack reached 35°,indicating the validity and feasibility of PMC method and APA for tail buffeting alleviation at high angle of attack.展开更多
基金Supported by the National Natural Science Foundation of China(42221002,42171432)Shanghai Municipal Science and Technology Major Project(2021SHZDZX0100)the Fundamental Research Funds for the Central Universities.
文摘The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching.In this work,an imaging simulation method consid-ering the attitude jitter is presented.The impact analysis of different attitude jitter on terrain undulation is conduct-ed by simulating jitter at three attitude angles,respectively.The proposed simulation method is based on the rigor-ous sensor model,using the lunar digital elevation model(DEM)and orthoimage as reference data.The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter.Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit.Experi-mental analyses were conducted by the DEM with the simulated stereo image.The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping.The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.
文摘A fast-locking, low-jitter, phase-locked loop （PLL） with a simple phase-frequency detector is proposed. The phase-frequency detector is composed of only two XOR gates. It simultaneously achieves low jitter and short locking time. The voltage-controlled oscillator within the PLL consists of four-stage ring oscillators which are coupled to each other and oscillate with the same frequency and a phase shift of 45. The PLL is fabricated in 0. 1Stem CMOS technology. The measured phase noise of the PLL output at 500kHz offset from the 5GHz center frequency is - 102.6dBc/Hz. The circuit exhibits a capture range of 280MHz and a low RMS jitter of 2.06ps. The power dissipation excluding the output buffers is only 21.6roW at a 1.8V supply.
文摘By jitter performance comparison between PLL (Phase Locked Loop) and DLL (Delay Locked Loop),a helpful equation is derived for the structure choice between DLL and PLL based synthesizers fabricated in CMOS processes to get an optimum jitter performance and power consumption.For a frequency synthesizer,a large multiple factor prefers PLL based configuration which consumes less power,while a small one needs DLL based topology which produces a better jitter performance.
基金the Natural Science Foundation of China (No. 50075029)
文摘This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.
基金Funded by the Communication System Project of Jiangsu Provincial Education Committee under grant No.JHB04010
文摘A fully integrated frequency synthesizer with low jitter and low power consumption in 0.18 μm CMOS (complementary metal-oxide semiconductor) technology is proposed in this paper.The frequency synthesizer uses a novel single-end gain-boosting charge pump, a differential coupled voltage controlled oscillator (VCO) and a dynamic logic phase/frequency detecor (PFD) to acquire low output jitter.The output frequency range of the frequency synthesizer is up to 1 200 MHz to 1 400 MHz for GPS (global position system) application.The post simulation results show that the phase noise of VCO is only 127.1 dBc/Hz at a 1 MHz offset and the Vp-p jitter of the frequency synthesizer output clock is 13.65 ps.The power consumption of the frequency synthesizer not including the divider is 4.8 mW for 1.8 V supply and it occupies a 0.8 mm×0.7 mm chip area.
文摘Faults and failures of induction machines can indeed lead to excessive costs, hence, there is a strong demand in the industry for adopting diagnosis techniques to assess and evaluate current condition of electrical machines. Eccentricity related faults as well as clutch wobbling constitute major portions of the faults related to induction motors. This paper presents the effect of clutch wobbling and mixed eccentricity on induction machine stator currents and the possibility of distinguishing between each ailment via comparing the abnormal harmonics contained in stator current spectrums in each case. In this paper, the current spectrum of a four pole-pairs, 550 kW, induction machine were calculated for the cases of full symmetry, clutch wobbling, and mixed eccentricity. The calculations involve integration of 93 electrical plus four mechanical ordinary differential equations. Electrical equations account for variable inductances affected by slotting and eccentricities. The calculations were followed by Fourier analysis of the stator currents. Zooms of the current spectrums, around the 50 Hz fundamental harmonic as well as of the main slot harmonic zone, of both calculated and measured currents are included. The spectrums presented in this paper rely on calculations that are performed with dedicated software which is owned by AGH University of Science and Technology.
基金supported by the National Natural Science Foundation of China (Grant No. 11072198)the Basic Research Program of Northwestern Polytechnical University (Grant No. JC201102) "111" Project(Grant No. B07050)
文摘Tail buffeting at high angle of attack causes distinct fatigue problem on tail structure of twin tail fighters.In this study,a piezoelectric active control experiment of tail buffeting was performed in a wind tunnel using arching PZT actuator(APA) and principal modal control(PMC) method.Test results showed the peak value of power spectral density(PSD) function of tail buffeting acceleration response could be suppressed by about 42% when the angle of attack reached 35°,indicating the validity and feasibility of PMC method and APA for tail buffeting alleviation at high angle of attack.
