1 天津市复杂控制理论与应用重点实验室，天津300384
2 天津理工大学, 天津 300384
针对四旋翼飞行器执行器发生故障同时存在扰动时的姿态控制问题，设计了一种基于模型参考自适应(MRAC）的容错控制器。通过分析四旋翼飞行器的动力学特性，将执行器故障以加性因子的形式加入系统模型中，得到执行器故障下的动力学模型。所设计控制器的自适应律由参考模型和执行器故障下的模型的误差信号驱动，可实现较好的姿态控制。利用Lyapunov的分析方法证明了所设计控制器的渐进稳定性,最后在Matlab下进行了仿真实验。仿真结果表明，系统能克服扰动且在执行器故障下可良好地跟踪参考姿态角，验证了该算法的可行性和有效性。
四旋翼飞行器 容错控制 姿态控制 执行器故障 模型参考自适应控制 quad-rotor UAV Fault Tolerant Control (FTC) attitude control actuator failure model reference adaptive control
Author Affiliations
Abstract
State Key Lab of ASIC, Department of Communication Science and Engineering, Fudan University, Shanghai 200433, China
With the rapid development of the light-emitting diode (LED) industry, interest in visible light communication (VLC) is growing. The limited bandwidth of commercial LEDs is one of the main challenges to achieve high-speed VLC. In this Letter, a kind of bandwidth-efficient VLC system based on carrierless amplitude and phase (CAP) modulation is proposed, where a simple differential faster-than-Nyquist (FTN) pre-coding scheme is employed to compress the spectrum and further improve the overall system baud rate. The system is experimentally demonstrated with a data rate of 1.47-Gb/s over 1.5 m free space transmission. The results indicate that an improvement of 80 Mbaud is achieved by FTN-CAP4 at 20% subband overlap and 40 Mbaud rate improvement by FTN-CAP16 at 7.5% subband overlap. Compared with traditional CAP, the FTN pre-coded CAP shows a better performance in spectral efficiency (SE) and intercarrier interference resistance. To the best of our knowledge, it is the first time to employ FTN pre-coded CAP in indoor high-data-rate VLC systems.
060.2605 Free-space optical communication 060.4510 Optical communications Chinese Optics Letters
2017, 15(8): 080601
Author Affiliations
Abstract
Key Laboratory for Information Science of Electromagnetic Waves (MoE), Department of Communication Science and Engineering, Fudan University, Shanghai 200433, China
Light-emitting diode (LED)-based visible light communication (VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation (QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular (7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak (vpp) value and bit error rate (BER). Next best is rectangular, followed by triangular; circular (4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular (7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of 3.8 × 10?3. Compared with circular (4,4), the traditional 8-QAM constellation, circular (7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge, this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular (7,1) is the optimal option.
Free-space optical communication Free-space optical communication Optical communications Optical communications Light-emitting diodes Light-emitting diodes Photonics Research
2016, 4(6): 06000249
复旦大学通信科学与工程系电磁波信息科学教育部重点实验室, 上海 200433
可见光大气传输系统面临的主要问题在于由大气湍流引起的光强闪烁和来自日光及其他照明设备的强背景光干扰，为了克服大气湍流造成的信道衰落效应及强背景光带来的噪声干扰问题，对室外可见光通信(VLC)强背景光大气湍流信道进行了建模。在接收端采用分集接收技术，在相同的发射功率下提高系统误码率(BER)性能。构建了在强背景光大气湍流信道模型下基于强度检测脉冲位置调制(PPM)方式的室外长距离可见光分集接收系统模型，在几十微瓦功率背景光噪声下，实现了800 Mb/s PPM 信号的仿真系统传输。基于此系统分别研究对比了最大比合并(MRC)、等增益合并(EGC)、选择性合并(SC)3 种分集合并方式的误码率性能。结果表明，在相同的发射功率下，误码率性能提升最大的是MRC，其次是EGC，SC 最差。以7%前向纠错码(FEC)误码门限作为参考，MRC 能显著降低对LED 发射功率的要求，并且随着分集支路个数的增多，分集效果越好。
大气光学 可见光通信 脉冲位置调制 信道建模 分集接收 大气湍流
Key Laboratory of Opto-Electronic Information and Technology, Ministry of Education, Institute of Modern Optics, Nankai University, Tianjin 300071, China
Frontiers of Optoelectronics
2010, 3(3): 283
研制成横向磁场中全内腔单模1.52μmHe—Ne激光器.提出了一种在锁定情况下,激光频率沿最佳S曲线连续调谐的方法.采用这种方法,激光频率在较宽范围内调谐,均达到较高频率稳定性.适于作单模光纤通讯的相干光源.
横向塞曼稳频激光器 连续可调谐激光器 1.52μm He—Ne激光器
