A high sensitive optical amplitude modulation magnetometer is investigated and demonstrated experimentally. We build an experimental platform for the atomic magnetometer and configure it as a Bell-Bloom magnetometer w...A high sensitive optical amplitude modulation magnetometer is investigated and demonstrated experimentally. We build an experimental platform for the atomic magnetometer and configure it as a Bell-Bloom magnetometer with amplitude modulation of 50% duty cycle square waveform. The open-loop input-output model is deduced from the Bloch equation and is verified experimentally. Instead of locking the frequency by using a voltage control oscillator, we realize a closed loop using the coils to generate a feedback field which avoids the stringent require- ment of a high resolution frequency meter and markedly expands the dynamic range as well as the bandwidth. We realize an open loop sensitivity of 0.8pT/Hz1/2 at 20 Hz using a single light beam, which exceeds that of the state-of-the-art Bell-Bloom magnetometers, and the corresponding closed loop sensitivity is 1.2 pT/Hz1/2.展开更多
A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more infor...A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method （GLS） the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illnstrates its effectiveness.展开更多
In order to solve the problem of difficult modeling and identification caused by time-variable parameters,multiple inputs and outputs and unstable open loop,a subsystem model-based close-loop grey-box identification m...In order to solve the problem of difficult modeling and identification caused by time-variable parameters,multiple inputs and outputs and unstable open loop,a subsystem model-based close-loop grey-box identification method was put forward when consider the main coupling effects of hydraulic Stewart platform.Firstly,the whole system is divided into three TITO(Two Input Two Output) subsystems according to the characteristics of the pseudo-mass matrix,hence transfer function matrix model of the subsystem can also be found.Secondly,since the Stewart platform is unstable,the close-loop transfer model of the subsystem is derived under the proportional controllers.The inverse M serial is adopted as the identification signal to get the experimental data.All parameters of the subsystem are determined in close-loop indirect identification by PEM(Prediction Error Method).Finally,a case study validates the correctness and effectiveness of the subsystem model-based close-loop grey-box identification method for hydraulic Stewart platform.展开更多
针对Boost变换器存在多种干扰和电子元件具有非整数阶特性的问题,提出了一种分数阶PID(fractional order PID,FOPID)电压外环-分数阶滑模控制器(fractional order sliding mode control,FOSMC)电流内环双闭环控制系统。首先,利用Oustal...针对Boost变换器存在多种干扰和电子元件具有非整数阶特性的问题,提出了一种分数阶PID(fractional order PID,FOPID)电压外环-分数阶滑模控制器(fractional order sliding mode control,FOSMC)电流内环双闭环控制系统。首先,利用Oustaloup算法对电感和电容进行7阶拟合,得到分数阶电路模型;其次,设计了微积分阶次可调的FOPID,并将其作为电压外环的控制器;然后,设计扩张状态观测器(extended state observer,ESO)对系统状态、负载扰动和输入扰动进行估计;最后,基于ESO的估计值,用FOPID作为滑模面构建了FOSMC。结果表明,与其他控制算法相比,FOPID-FOSMC双闭环控制策略结合了电压外环的稳态调节能力和电流内环的快速响应能力,实现了对Boost变换器输出电压和电流的双重优化控制,具有更快的响应速度、更小的超调量、更短的恢复时间和更好的稳定性与鲁棒性。展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 61273067 and 61074171the National Basic Research Program of China under Grant No 2012CB934104
文摘A high sensitive optical amplitude modulation magnetometer is investigated and demonstrated experimentally. We build an experimental platform for the atomic magnetometer and configure it as a Bell-Bloom magnetometer with amplitude modulation of 50% duty cycle square waveform. The open-loop input-output model is deduced from the Bloch equation and is verified experimentally. Instead of locking the frequency by using a voltage control oscillator, we realize a closed loop using the coils to generate a feedback field which avoids the stringent require- ment of a high resolution frequency meter and markedly expands the dynamic range as well as the bandwidth. We realize an open loop sensitivity of 0.8pT/Hz1/2 at 20 Hz using a single light beam, which exceeds that of the state-of-the-art Bell-Bloom magnetometers, and the corresponding closed loop sensitivity is 1.2 pT/Hz1/2.
基金Project supported by National Natural Science Foundation ofChina (Grant No .60174030)
文摘A new identification method for a linear discrete-time closed-loop system is proposed based on an output over-sampling scheme. When the system outputs are over-sampled the new output sequences would contain more information about the plant structure. Using general least squares method （GLS） the plant over-sampled model should be recognized. Then the original plant model should be obtained by its relationship with the over-sampled model. Compared with conventional approaches the advantage of the new method is that even if the ordinary identifiability conditions are not satisfied, a close-loop system can be identified by using the oversampled output without utilizing any external test signal. Accuracy analysis shows the relationship between the estimation error and the over-sampling rate. Numerical simulation illnstrates its effectiveness.
文摘In order to solve the problem of difficult modeling and identification caused by time-variable parameters,multiple inputs and outputs and unstable open loop,a subsystem model-based close-loop grey-box identification method was put forward when consider the main coupling effects of hydraulic Stewart platform.Firstly,the whole system is divided into three TITO(Two Input Two Output) subsystems according to the characteristics of the pseudo-mass matrix,hence transfer function matrix model of the subsystem can also be found.Secondly,since the Stewart platform is unstable,the close-loop transfer model of the subsystem is derived under the proportional controllers.The inverse M serial is adopted as the identification signal to get the experimental data.All parameters of the subsystem are determined in close-loop indirect identification by PEM(Prediction Error Method).Finally,a case study validates the correctness and effectiveness of the subsystem model-based close-loop grey-box identification method for hydraulic Stewart platform.
文摘针对Boost变换器存在多种干扰和电子元件具有非整数阶特性的问题,提出了一种分数阶PID(fractional order PID,FOPID)电压外环-分数阶滑模控制器(fractional order sliding mode control,FOSMC)电流内环双闭环控制系统。首先,利用Oustaloup算法对电感和电容进行7阶拟合,得到分数阶电路模型;其次,设计了微积分阶次可调的FOPID,并将其作为电压外环的控制器;然后,设计扩张状态观测器(extended state observer,ESO)对系统状态、负载扰动和输入扰动进行估计;最后,基于ESO的估计值,用FOPID作为滑模面构建了FOSMC。结果表明,与其他控制算法相比,FOPID-FOSMC双闭环控制策略结合了电压外环的稳态调节能力和电流内环的快速响应能力,实现了对Boost变换器输出电压和电流的双重优化控制,具有更快的响应速度、更小的超调量、更短的恢复时间和更好的稳定性与鲁棒性。
