交流电机位置伺服系统的扰动补偿控制

针对交流电机伺服系统在未知负载条件下进行准确位置控制的需求,提出了一种参数化复合控制方案。该方案建立在交流电机磁场定向矢量控制构架的基础上,以转矩电流作为控制信号(电流内环的给定值),以电机转角位置信号作为可量测的系统输出量,设计了基于极点配置的状态反馈与扰动前馈补偿组成的参数化控制律,并利用一个降阶线性扩展状态观测器对电机转速(未量测)和未知负载扰动加以估计。该控制律通过TMS320F28335DSP编程,在一台永磁同步电机伺服系统上进行了实验测试,实验结果验证了伺服系统能在未知负载情况下对各目标位置进行平稳且准确地跟踪。研究结果表明,这种基于扩展状态观测器的复合控制方案可以有效地实现交流伺服系统的高性能位置调节,且对负载幅值和模型参数差异具有较好的鲁棒性。     

气液两相流强化卷式纳滤膜分离硫酸镁水溶液

气液两相流强化卷式纳滤膜分离实验是针对DK2540卷式纳滤膜,采用气液两相流强化分离技术,对硫酸镁溶液进行研究,较系统地研究了温度、料液浓度、过膜压力、料液流速、气体流速等因素在分离硫酸镁溶液时,对膜通量、截留率和膜通量增加率的影响,并总结了气液两相流强化效果。结果表明,气液两相流强化卷式纳滤膜分离有明显的效果。温度宜在30~40℃。料液浓度越大、过膜压力越小、气液比越大,气液两相流强化效果越明显。     

W‐Band MMIC chipset in 0.1‐μm mHEMT technology

We developed a 0.1‐μm metamorphic high electron mobility transistor and fabricated a W‐band monolithic microwave integrated circuit chipset with our in‐house technology to verify the performance and usability of the developed technology. The DC characteristics were a drain current density of 747 mA/mm and a maximum transconductance of 1.354 S/mm; the RF characteristics were a cutoff frequency of 210 GHz and a maximum oscillation frequency of 252 GHz. A frequency multiplier was developed to increase the frequency of the input signal. The fabricated multiplier showed high output values (more than 0 dBm) in the 94 GHz–108 GHz band and achieved excellent spurious suppression. A low‐noise amplifier (LNA) with a four‐stage single‐ended architecture using a common‐source stage was also developed. This LNA achieved a gain of 20 dB in a band between 83 GHz and 110 GHz and a noise figure lower than 3.8 dB with a frequency of 94 GHz. A W‐band image‐rejection mixer (IRM) with an external off‐chip coupler was also designed. The IRM provided a conversion gain of 13 dB–17 dB for RF frequencies of 80 GHz–110 GHz and image‐rejection ratios of 17 dB–19 dB for RF frequencies of 93 GHz–100 GHz.     

压电驱动的快刀伺服器的迟滞逆模型辨析与自抗扰复合逆控制

为了提高具有表面微结构零件的超精密加工中快刀伺服器的轨迹预测和跟踪精度与抗干扰性,设计一种新型复合控制:在前馈控制器中用Preisach逆模型补偿系统中压电陶瓷驱动器引起的非线性特性;针对前馈控制器未能补偿的非建模扰动、模型参数的不确定性以及其他外界未知扰动,设计了自抗扰控制作反馈控制器。推导了Preisach逆模型;用RBF神经网络实现了Preisach逆模型对压电陶瓷驱动器的线性化补偿;通过对快刀伺服器的建模分析,得到惯性环节和二阶振荡环节串联的等效模型,设计三阶四维扩张状态观测器,可对未知扰动的观测结果作出实时估计和补偿。根据快刀伺服器和超精密车削的特点,取消跟踪微分器,增加速度输入和加速度输入,设计了改进的自抗扰控制器。上述两种控制器组合成复合控制器。实验表明,该复合控制方法可以提高预测和跟踪精度与抗干扰性。     

宽带数字接收机I/Q幅相不一致性的校正

随着数字技术的发展,正交双通道变换在接收机中得到了广泛的应用。但是,由于各种因素的影响,I／Q通道的正交一致性并不能得到完全的保证,这会降低接收机的动态范围,进而影响接收机的性能。本文提出了一种宽带数字接收机I／Q幅相不一致性的校正方法,首先通过一种时域方法获得误差信息,接着构造滤波器组对I／Q信号进行校正。仿真结果表明,这种方法能有效提高宽带接收机I／Q通道的正交一致性。     

基于自抗扰的自主水下航行器地形跟踪控制

为保证自主水下航行器在进行地形跟踪任务时,可以更好地抵抗外界环境及自身信号传输的干扰作用,提出一种基于自抗扰控制技术的地形跟踪控制方法,可以将地形跟踪转化为水下机器人的纵倾控制,并设计有运动保护机制。在仿真实验中,利用所设计方法,进行了三维运动仿真,模拟了机器人从水面到水下完成地形跟踪任务的全过程,并与基于PID控制方法的控制器进行比较。结果表明,基于自抗扰控制技术的地形跟踪控制方法能够准确完成预定任务,同时,相比于基于PID的跟踪方法,能够更有效地抑制干扰所造成的超调和震颤等现象,具有更优的控制效果。     

MAN009铸造桥过桥箱工艺改进

对MAN009铸造桥过桥箱铸造工艺进行改进后,节约了生产成本,提高了生产效率,并大幅度降低了废品率。     

基于DR-BN的冷水机组故障检测

在冷水机组现场的故障数据通常难以获得,这是导致基于多分类算法的故障检测方法未被广泛现场应用的主要障碍之一。本文将距离拒绝(DR)机制融入贝叶斯网络(BN)中,将冷水机组故障检测转化为一类划分问题,提出一种基于DR-BN的冷水机组故障检测方法,该方法仅使用正常数据训练模型,从而有效克服上述障碍。本文通过使用ASHRAE RP-1043的故障实验数据对提出方法的性能进行验证,并与传统方法的性能进行了对比,可知基于DR-BN的模型具有更高的故障检测性能,尤其对低劣化等级下的故障,故障检测正确率最高时可高出94%。     

Evaluation of Prosopis juliflora as a potential feedstock for the production of sodium lignosulfonate from the spent liquor of a laboratory digester

Abstract

Chopped stems of Prosopis juliflora, an invasive xerophyte, were digested in a laboratory digester following alkaline sulfite pulping process to generate spent liquor whereby lignin underwent sulfonation to produce sodium lignosulfonate (SLS). SLS was concentrated from the spent liquor by ultrafiltration. Raw wood was featured by high lignin (23.5%), low extractives (1.0%), low wax (0.41), and low ash (2.25%) content thus making it an ideal feedstock to produce lignosulfonates with appreciable physico-chemical property and relatively high mechanical strength. Attempts were made to provide basic information on SLS structure and structural changes that might occur during pulping of P. juliflora under the present experimental conditions. Spectral and X-ray diffraction studies on as-produced SLS revealed substantial depolymerization and structural modification of lignin during sulfite pulping. The derived SLS had higher crystallinity index than the feedstock wood. Effect of average size of raw wood chip and dose of sodium sulfite in the overall yield of pulp and SLS along with the kappa number of the pulp were also analyzed. Findings from this study would serve to cultivate a better understanding of the potential of P. juliflora as a feedstock, so far unexplored, to produce SLS???a value-added product with numerous commercial applications. The use of this particular plant species in paper and pulp industry could also be considered as an effective means of integrated agro management in rural areas.     

可反馈线性化系统的鲁棒自适应容错控制设计

针对存在不确定执行器故障和未知不匹配干扰的可反馈线性化非线性系统, 提出一种鲁棒自适应容错控 制策略. 首先分别给出系统输入和扰动关于系统输出的相对阶, 针对两种相对阶之间的不同关系设计鲁棒控制器, 抑制干扰对系统输出的影响; 然后针对各故障情况分别设计容错控制器; 最后将各控制器进行融合得到一个综合 故障补偿控制器, 从而有效解决故障模式、类型、大小、时间和外界干扰等多重不确定性, 保证闭环系统稳定和渐近 输出跟踪性能. 仿真结果验证了所设计控制方案的可行性与有效性.