Raman spectra of purified oxygen evolution core complexes (Pd OECC) thin films on silver mirror substrates have been taken over the frequency range of 250-3100 cm -1 by surface enhanced Raman scattering (SERS). B...Raman spectra of purified oxygen evolution core complexes (Pd OECC) thin films on silver mirror substrates have been taken over the frequency range of 250-3100 cm -1 by surface enhanced Raman scattering (SERS). Besides the fundamental frequency modes of β_carotene in Pd OECC, many weak peaks are observed. According to the selection rules of overtone and combination bands, most of them are attributed to the second_order Raman spectra of β_carotene. Compared with the SERS of normal Pd OECC, the SERS of Pd OECC after strong illumination shows a decrease in scattering intensity and an increase in line widths, indicating changes of conformation and micro_environment of β_carotene. The results of SERS are consistent with the changes of absorption spectrum of Pd OECC induced by strong illumination. There are no changes that can be ascribed to new vibration bands, so it is deduced that Pd OECC on the silver mirror is identical to that in the solution. In summary, SERS proved a good method to study the photodamage mechanism of photosynthesis.展开更多
The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings ...The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings between the engine dynamics and flight dynamics.To overcome the analytical intractability of this model,a nominal control-oriented model is constructed for the purpose of feedback control design in the first place.Secondly,the multi-input multi-output（MIMO） quasi-continuous high-order sliding mode（HOSM） controller is proposed to track step changes in velocity and altitude,which is based on full state feedback.The simulation results are presented to verify the effectiveness of the proposed control strategy.展开更多
A novel high-order sliding mode control strategy is proposed for the attitude control problem of reentry vehicles in the presence of parametric uncertainties and external disturbances, which results in the robust and ...A novel high-order sliding mode control strategy is proposed for the attitude control problem of reentry vehicles in the presence of parametric uncertainties and external disturbances, which results in the robust and accurate tracking of the aerodynamic angle commands with the finite time convergence. The proposed control strategy is developed on the basis of integral sliding mode philosophy, which combines conventional sliding mode control and a linear quadratic regulator over a finite time interval with a free-final-state and allows the finite-time establishment of a high-order sliding mode. Firstly, a second-order sliding mode attitude controller is designed in the proposed high-order siding mode control framework. Then, to address the control chattering problem, a virtual control is introduced in the control design and hence a third-order sliding mode attitude controller is developed, leading to the chattering reduction as well as the control accuracy improvement. Finally, simulation examples are given to illustrate the effectiveness of the theoretical results.展开更多
This paper proposes a higher order sliding mode controller for uncertain robot manipulators. The motivation for using high order sliding mode mainly relies on its appreciable features, such as high precision and elimi...This paper proposes a higher order sliding mode controller for uncertain robot manipulators. The motivation for using high order sliding mode mainly relies on its appreciable features, such as high precision and elimination of chattering in addition to assure the same performance of conventional sliding mode like robustness. Instead of a regular control input, the derivative of the control input is used in the proposed control law. The discontinuity in the controller is made to act on the time derivative of the control input. The actual control signal obtained by integrating the derivative control signal is smooth and chattering free. The stability and the robustness of the proposed controller can be easily verified by using the classical Lyapunov criterion. The proposed controller is tested to a three-degree-of-freedom robot to prove its effectiveness.展开更多
The method to design sliding-mode observers for systems with unknown inputs and measurement disturbances is presented in the paper. An augmented system is constructed by viewing the measurement disturbances as unknow ...The method to design sliding-mode observers for systems with unknown inputs and measurement disturbances is presented in the paper. An augmented system is constructed by viewing the measurement disturbances as unknow inputs. For such an augmented system, the so-called observer matching condition is not satisfied. Based on the construction of auxiliary outputs, the observer matching condition may be satisfied. High-order sliding-mode differentiators are developed to obtain the estimates of those unmeasurable variables contained in the auxiliary output vector. Employing the estimate of auxiliary output vector, a sliding-mode observer is designed. The simulation results to a real model show that the proposed method is effective.展开更多
In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-...In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.展开更多
激光光束的指向噪声对物理量的精密测量、激光材料加工、自由空间远距离光通讯、星载激光对准系统等许多应用场景都有负面影响,抑制光束指向噪声的研究有着重要意义。本文在实验上利用Sagnac干涉仪针对压电陶瓷产生的倾斜指向噪声抑制...激光光束的指向噪声对物理量的精密测量、激光材料加工、自由空间远距离光通讯、星载激光对准系统等许多应用场景都有负面影响,抑制光束指向噪声的研究有着重要意义。本文在实验上利用Sagnac干涉仪针对压电陶瓷产生的倾斜指向噪声抑制开展了研究,系统通过高阶模式滤波原理将指向噪声激发的厄米-高斯光模分离。理论上使用传输矩阵进行分析,给出了干涉仪抑制指向噪声的原理及与相关参数的关系。实验上搭建Sagnac干涉仪,对装有反射镜压电陶瓷产生的指向噪声进行抑制,并与压电陶瓷随驱动电压相同的指向噪声直接探测的情况进行了相应的对比。实验结果表明,当压电倾斜镜产生2.5μrad的信号时,干涉仪能抑制43.3 d B的指向噪声。该方法不需要闭环反馈技术,适用于连续波激光系统中,尤其是需要快速修正的场景。展开更多
分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simul...分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simulink环境下构建了复合式高速直升机姿态控制系统,并与PID(proportion integral differential)控制器和LQG(linear quadratic Gaussian)控制器进行了仿真对比。研究结果表明:所提出的基于高阶滑模微分器的姿态自抗扰控制器能够实现对姿态角的无超调跟踪,相较于PID控制器和LQG控制器,误差收敛速度分别提升31.5%和64.2%,且在噪声干扰下,最大跟踪误差比LQG控制器小34.2%,比PID控制器小39.5%。展开更多
基金The State Key Basic Research and Developmental Plan(G1998010100).
文摘Raman spectra of purified oxygen evolution core complexes (Pd OECC) thin films on silver mirror substrates have been taken over the frequency range of 250-3100 cm -1 by surface enhanced Raman scattering (SERS). Besides the fundamental frequency modes of β_carotene in Pd OECC, many weak peaks are observed. According to the selection rules of overtone and combination bands, most of them are attributed to the second_order Raman spectra of β_carotene. Compared with the SERS of normal Pd OECC, the SERS of Pd OECC after strong illumination shows a decrease in scattering intensity and an increase in line widths, indicating changes of conformation and micro_environment of β_carotene. The results of SERS are consistent with the changes of absorption spectrum of Pd OECC induced by strong illumination. There are no changes that can be ascribed to new vibration bands, so it is deduced that Pd OECC on the silver mirror is identical to that in the solution. In summary, SERS proved a good method to study the photodamage mechanism of photosynthesis.
基金supported by the National Natural Science Foundation of China(9101601861273092+3 种基金61203012)the Foundation for Key Program of Ministry of Education of China(311012)the Key Program for Basic Research of Tianjin(11JCZDJC25100)the Key Program of Tianjin Natural Science(12JCZDJC30300)
文摘The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings between the engine dynamics and flight dynamics.To overcome the analytical intractability of this model,a nominal control-oriented model is constructed for the purpose of feedback control design in the first place.Secondly,the multi-input multi-output（MIMO） quasi-continuous high-order sliding mode（HOSM） controller is proposed to track step changes in velocity and altitude,which is based on full state feedback.The simulation results are presented to verify the effectiveness of the proposed control strategy.
基金supported by Major State Basic Research Development Program(2012CB720000)National Natural Science Foundation of China(11372034)Innovative Research Team of Beijing Institute of Technology
文摘A novel high-order sliding mode control strategy is proposed for the attitude control problem of reentry vehicles in the presence of parametric uncertainties and external disturbances, which results in the robust and accurate tracking of the aerodynamic angle commands with the finite time convergence. The proposed control strategy is developed on the basis of integral sliding mode philosophy, which combines conventional sliding mode control and a linear quadratic regulator over a finite time interval with a free-final-state and allows the finite-time establishment of a high-order sliding mode. Firstly, a second-order sliding mode attitude controller is designed in the proposed high-order siding mode control framework. Then, to address the control chattering problem, a virtual control is introduced in the control design and hence a third-order sliding mode attitude controller is developed, leading to the chattering reduction as well as the control accuracy improvement. Finally, simulation examples are given to illustrate the effectiveness of the theoretical results.
文摘This paper proposes a higher order sliding mode controller for uncertain robot manipulators. The motivation for using high order sliding mode mainly relies on its appreciable features, such as high precision and elimination of chattering in addition to assure the same performance of conventional sliding mode like robustness. Instead of a regular control input, the derivative of the control input is used in the proposed control law. The discontinuity in the controller is made to act on the time derivative of the control input. The actual control signal obtained by integrating the derivative control signal is smooth and chattering free. The stability and the robustness of the proposed controller can be easily verified by using the classical Lyapunov criterion. The proposed controller is tested to a three-degree-of-freedom robot to prove its effectiveness.
基金Funded by the National Natural Science Foundation(No.61203299/F030506)
文摘The method to design sliding-mode observers for systems with unknown inputs and measurement disturbances is presented in the paper. An augmented system is constructed by viewing the measurement disturbances as unknow inputs. For such an augmented system, the so-called observer matching condition is not satisfied. Based on the construction of auxiliary outputs, the observer matching condition may be satisfied. High-order sliding-mode differentiators are developed to obtain the estimates of those unmeasurable variables contained in the auxiliary output vector. Employing the estimate of auxiliary output vector, a sliding-mode observer is designed. The simulation results to a real model show that the proposed method is effective.
基金Supported in part by the National Natural Science Foundation of China(62401125)the Natural Science Foundation of Sichuan Province(2023NSFSC1376)the Fundamental Research Funds for the Central Universities(ZYGX2024J008)。
文摘In this paper,a scheme of commonly-resonated extended interaction circuit system based on high order TMn,mode is proposed to lock the phases of two extended interaction oscillators(EIOs)for generating high power at G-band.Two separate EIOs are coupled through a specific single-gap coupling field supported by a designed gap waveguide with length Lg,which form the phase-locked EIOs based on the commonly-resonated system.As a whole system,the system has been focused on with mode analysis based on different single-gap coupling fields,mode hopping,which present the variation of phase difference between the two-beam-wave interactions when changing Lg.To demonstrate the effectiveness of the proposed circuit system in producing the phase locking,we conducted particle-in-cell(PIC)simulations to show that the interesting mode hopping occurs with the phase difference of O and r between the output signals from two output ports,corresponding to the excitation of the TMn mode with different n.Simulation results show that 1)the oscillator can deliver two times of the output power obtained from one single oscillator at 220 GHz,2)the two EIOs can still deliver output signals with phase difference of O and when the currents of the two beams are different or the fabrication errors of the two EIO cavities are taken into account.The proposed scheme is promising in extending to phase locking between multiple EIOs,and generating higher power at millimeter-wave and higher frequencies.
文摘激光光束的指向噪声对物理量的精密测量、激光材料加工、自由空间远距离光通讯、星载激光对准系统等许多应用场景都有负面影响,抑制光束指向噪声的研究有着重要意义。本文在实验上利用Sagnac干涉仪针对压电陶瓷产生的倾斜指向噪声抑制开展了研究,系统通过高阶模式滤波原理将指向噪声激发的厄米-高斯光模分离。理论上使用传输矩阵进行分析,给出了干涉仪抑制指向噪声的原理及与相关参数的关系。实验上搭建Sagnac干涉仪,对装有反射镜压电陶瓷产生的指向噪声进行抑制,并与压电陶瓷随驱动电压相同的指向噪声直接探测的情况进行了相应的对比。实验结果表明,当压电倾斜镜产生2.5μrad的信号时,干涉仪能抑制43.3 d B的指向噪声。该方法不需要闭环反馈技术,适用于连续波激光系统中,尤其是需要快速修正的场景。
文摘分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simulink环境下构建了复合式高速直升机姿态控制系统,并与PID(proportion integral differential)控制器和LQG(linear quadratic Gaussian)控制器进行了仿真对比。研究结果表明:所提出的基于高阶滑模微分器的姿态自抗扰控制器能够实现对姿态角的无超调跟踪,相较于PID控制器和LQG控制器,误差收敛速度分别提升31.5%和64.2%,且在噪声干扰下,最大跟踪误差比LQG控制器小34.2%,比PID控制器小39.5%。
