PREDICTIVE VARIABLE STRUCTURE CONTROL FOR A CLASS OF NONLINEAR SYSTEM

Nonlinear sliding mode predictive controller is designed for a class of nonlinear system with unmodeled dynamic characteristics and nonlinear term. The method is based on nonlinear optimal predictive control. The variable structure control law minimizes the quadratic index of a predictive sliding mode, which contains the cost function of control preventing the control effect from saturation for in most practical implementation the control inputs are bounded by physical constraints and energy constraints. According to the immeasurable states, the variable structure observer for nonlinear systems is adapted. The variable structure system method is apt to the realization of observer with variable parameters and uncertainty. The proof shows that the states of the observer asymptotically convergence to the real states of the system although it is of uncertainty and nonlinear terms. Finally, the digital simulation results prove the effectiveness of the proposed method.     

Z-源稀疏矩阵变换器励磁的双馈风力发电系统

针对矩阵变换器电压传输比低和其励磁的双馈风力发电系统(DFIG)易受非正常输入波动影响的不足,提出了一种适用于DFIG励磁的Z-源稀疏矩阵变换器系统。利用Z-源的升压特性来提高电压传输比,检测电容电压实现对直通因子的自动调节,从而实现对网侧波动的自动抑制。建立了系统数学模型,推导了DFIG系统定子磁场定向矢量控制策略表达式,搭建试验样机对所提方案进行试验验证,在亚同步、同步、超同步三种发电状态下的波形和并网试验结果验证了方案的可行和有效性。     

基于裂比的非晶合金永磁电机设计技术

非晶合金材料电磁性能优异,应用于电机领域能显著降低电机铁心损耗,提高电机效率。针对非晶合金材料的特点,基于永磁电机基本设计理论,推导了非晶合金电机铜耗与铁心损耗的解析表达式。基于非晶合金永磁电机损耗的解析表达式对非晶合金永磁电机裂比(定子内外径之比)、磁密比值(气隙磁密与铁心磁密之比)的设计进行了研究,得出了非晶合金永磁电机裂比、磁密比值的设计规律。在对非晶合金永磁电机设计规律研究的基础上完成了一台非晶合金永磁电机的设计并进行了试验。所做的研究对非晶合金电机的设计及优化具有一定的参考价值。     

四相聚磁型无源转子横向磁通永磁电机交直轴电感及电磁转矩分析

以一种新型四相聚磁型无源转子横向磁通永磁电机为研究对象,基于三维有限元法,利用4/2变换公式计算出不同工况下电机的交、直轴电感大小,并深入分析其变化规律和影响因素。在此基础上,利用得到的电感数据,计算出不同电流控制角下的电磁转矩,并与仿真数据相比较,总结其变化规律。研究结果为该类电机的设计分析和控制方法提供了一定的参考依据。     

基于新型纯积分法的定子磁链在线辨识算法

针对气隙转矩法计算异步电机转矩时对定子磁链辨识精度的要求,提出了一种基于新型纯积分法的定子磁链在线辨识算法,采用了精度较高的复化辛普森积分模型。相比传统的梯形积分法,基于新型纯积方法的定子磁链在线辨识算法的磁链辨识精度显著提高;相比新型的基于低通滤波器的定子磁链观测器,该算法模型更简单,操作更便捷。通过MATLAB/Simulink搭建系统仿真平台进行验证,结果表明基于新型纯积分算法消除了传统积分法的主要缺陷,解决了积分饱和问题以及初值问题。基于新型纯积分算法的估计磁链与理论参考磁链基本吻合,表明其可靠性较高。     

Research on Fault-tolerant Control Method of ElectromechanicalActuating System Based on Sliding Mode Observer

机电作动器(Electro-Mechanical Actuator,EMA)正在逐步代替液压/气压作动器而广泛应用于航空航天、军事等领域,特别是在多电/全电飞行器中,机电作动系统已引来大量学者开展各类型研究。在 EMA 的控制方法和实际应用逐渐成熟的前提下,进一步提高系统的可靠性得到广泛的关注。在 EMA 运行过程中能够进行实时的故障检测并保证系统的正常运行,有效提高系统可靠性对于 EMA 的应用具有重要意义。本文提出一种基于滑模观测器的容错控制方法,为 EMA 在工程应用中有效识别系统的运行状态提供重要手段,具有重要的理论意义和工程应用价值。通过仿真验证得出此方法可靠有效,验证了在系统运行过程中能够快速的识别故障并切换控制,表明 EMA 系统在此控制方法下具有很好的故障识别和故障隔离能力。     

复杂约束下的编队姿态有限时间协同控制方法

综合考虑无角速度量测、外部扰动和系统参数不确定性等约束条件的影响，研究航天器编队姿态有限时间协同控制问题。首先建立航天器相对姿态协同控制模型，利用扩张观测器实现对系统姿态角速度及耦合扰动的估计；在此基础上提出了一种有限时间滑模姿态协同控制律；通过构造合适的Lyapunov函数证明了系统相对姿态误差能够在有限时间内收敛到有界域内；将该结果推广到存在饱和输入情形下，并设计了相应的有限时间滑模姿态协同控制律。仿真结果校验了算法的有效性。     

Inter-satellite calibration of FengYun 3 medium energy electron fluxes with POES electron measurements

We perform an L-shell dependent inter-satellite calibration of FengYun 3 medium energy electron measurements with POES measurements based on rough orbital conjunctions within 5?min?×?0.1?L?×?0.5 MLT. By comparing electron flux data between the U.S. Polar Orbiting Environmental Satellites (POES) and Chinese sun-synchronous satellites including FY-3B and FY-3C for a whole year of 2014, we attempt to remove less reliable data and evaluate systematic uncertainties associated with the FY-3B and FY-3C datasets, expecting to quantify the inter-satellite calibration factors for the 150–350?keV energy channel at L?=?2–7. Compared to the POES data, the FY-3B and FY-3C data generally exhibit a similar trend of electron flux variations but more or less underestimate them within a factor of 5 for the medium electron energy 150–350?keV channel. Good consistency in the flux conjunctions after the inter-calibration procedures gives us certain confidence to generalize our method to calibrate electron flux measurements from various satellite instruments.     

Fixed-time adaptive model reference sliding mode control for an air-to-ground missile

This paper addresses the fixed-time adaptive model reference sliding mode control for an air-to-ground missile associated with large speed ranges, mismatched disturbances and un-modeled dynamics. Firstly, a sliding mode surface is developed by the tracking error of the state equation and the model reference state equation with respect to the air-to-ground missile. More specifically,a novel fixed-time adaptive reaching law is presented. Subsequently, the mismatched disturbances and the un-modeled dynamics are treated as the model errors of the state equation. These model errors are estimated by means of a fixed-time disturbance observer, and they are also utilized to compensate the proposed controller. Therefore, the fixed-time controller is obtained by an adaptive reaching law and a fixed-time disturbance observer. Closed-loop stability of the proposed controller is established. Finally, simulation results including Monte Carlo simulations, nonlinear six-DegreeOf-Freedom(6-DOF) simulations and different ranges are presented to demonstrate the efficacy of the proposed control scheme.     

Local orbital debris flux study in the geostationary ring

A local orbital debris flux analysis is performed in the geostationary (GEO) ring to investigate how frequently near-miss events occur for each longitude slot in the GEO ring. The current resident space object (RSO) environment at GEO is evaluated, and publicly-available two-line element (TLE) data are utilized in tandem with a geostationary torus configuration to simulate near-miss events incurred by the trackable RSO population at GEO. Methodology for determining near-miss events with this formulation is introduced, and the results of the analysis for a one-year time frame are provided to illustrate the need for active GEO remediation.