Controllable thermal rectification design for buildings based on phase change composites

Phase-change material(PCM)is widely used in thermal management due to their unique thermal behavior.However,related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level,which results in a gap to real applications.Here,we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material(TRM)based on PCM and reduced graphene oxide(rGO)aerogel to ordinary concrete walls(CWs).The design is evaluated in detail by combining experiments and finite element analysis.It is found that,TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification.The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m^(2).In addition,the larger the change of thermal conductivity before and after phase change of TRM is,the more effective it is for regulating temperature difference in two directions.The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.

Impact of GCP distribution on the rectification accuracy of Landsat TM imagery in a coastal zone

The purpose is to explore the effect of the spatial distribution of ground control points （GCPs） on the accuracy of imagery rectification. Both area-distributed and linearly distributed GCPs were used to rectify a Landsat TM image of a coastal zone. Rectification accuracy was checked against 99 independent points over the intertidal mudflats with no ground control. Results indicate that the root-mean-square error of residuals over these areas is several times larger than its GCPs-measured counterpart. If the GCPs are spatially dispersed over an area, residuals fluctuate but increase steadily with distance to the source of control in easting （R^2= 0. 827）. in northing they fluctuate around 150 m until 15 km, beyond which they rise steadily at a small range of fluctuation. These residuals are less predictable from distance to the source of control than in easting （R^2= 0.517 ）. If the GCPs are distributed along a control line, residuals rise with distance to it linearly and predictably （R^2 = 0. 877） in the direction perpendicular to it. In a direction parallel to it, the distance has little impact on rectification residuals.

Rectifying control of wire diameter during dieless drawing by a deformation measuring method of interframe displacement

A deformation measurement method of interframe displacement was proposed in this paper. By online monitoring the shape di- mensions of both the deformation zone and its adjacent zone by machine vision, the initial and terminative positions of deformation were dynamically identified during dieless drawing, and the global monitoring and online closed-loop control of the deformation zone were achieved. The dieless drawing process was systematically carried out on NiTi shape memory alloy wires. It is shown that the deformation measurement method of interframe displacement can track the axial displacement of the wires, but this cannot be achieved by traditional machine vision. The initial and terminative positions of deformation can be accurately identified by this method. The proposed rectifying control technology can effectively decrease the wire diameter fluctuation during dieless drawing, that is, the standard deviation of the wire diameter fluctuation could be decreased fi＇om 0.30 to 0.08 mm after three passes of dieless drawing, indicating that the control system has a good rectifying ability.

Inverter power supply system for high-power twin-wire pulsed GMAW

A type of novel inverter power supply system for high-power twin-wire pulsed gas metal arc welding （GMAW） is presented mainly for dealing with the disadvantages of the conventional power supply for twin-wire pulsed GMA W of which the output power is generally difficult to increase due to limitations of the power of semiconductors and the power density of magnetic devices. In the power supplies for the master and slave arcs, the digital signal processor （DSP） TMS320F28335 is used to form the DSP- based synergic control system for parallel high-power pulsed GMA W, which achieves high-power output of two parallel inverters controlled by a single DSP ; master-slave communication is achieved by using e controller area network （eCAN）module of DSP, thas realizing anti-phase pulse output of high-power twin-wire pulsed GMA W and reducing the interference between twin arcs. The experiment results demonstrate that the designed inverter power supply system for high-power twin-wire pulsed GMAW can bring about high-power efficiency of welding, stable welding process and proper formation of welds.

Variable Tension Control for Discontinuous Tape Winding of Composites Based on Constant Extension Ratio

Discontinuous tape winding, which has obvious advantages in large extension ratio winding, is widely used in the molding of composites. Therefore, the research on technological parameters becomes the focus of many scholars. However, how to accomplish the variable tension control is usually not fully considered. Accordingly, the constant extension ratio and the smoothness of winding process cannot be ensured. Aiming at the problem of tension control, this paper first gives a comparatively deep research on the control method and the interaction mechanism of tension, extension ratio, automatic lap and automatic rectification. Then, according to the winding process features, the mechanical device and the mathematical model of tension control system are established respectively. With regard to the characteristics of PID controller and fuzzy controller, the fuzzy self-tuning PID controller is designed. As a result, the variable tension control is realized during the winding and lapping process, and the constant extension ratio is guaranteed. Finally, a sample application is presented for demonstration. By presenting the variable tension control techniques for discontinuous tape winding, the constant extension ratio of tapes is achieved, the consecution and the automation degree of winding process is improved as well. Thus, the quality of wound products is guaranteed.

Indirect Adaptive Robust Trajectory Tracking Control of Hard Rock TBM with Load Variation of Tunneling Face

Posture adjustment of open-type hard rock tunnel boring machine(TBM) can be achieved by properly adjusting the hydraulic pressure of gripper cylinder and torque cylinders. However, the time-varying inhomogeneous load acting on tunneling face of TBM and complex stratum working condition can cause the trajectory deviation. In this paper,the position and posture rectification kinematics and dynamics models of TBM have been established in order to track the trajectory. Moreover, there are uncertain parameters and uncertain loads from complex working conditions in the dynamic model. An indirect adaptive robust control strategy is applied to achieve precise position and posture trajectory tracking control. Simulation results show when the position deviation only occurs in Y-axis and the current orientation is parallel with the designed axis, the deviation can be corrected by controlling the pressure of gripper cylinder and the actual trajectory meets the designed axis when TBM is pushed forward 0.14 m in X-axis. If the deviation only occurs in Z-axis, then the deviation can be corrected by controlling torque cylinders. If the position deviation occurs both in Y-axis and Z-axis at the same time, the pressure of gripper cylinder and torque cylinders should be controlled at the same time to rectify the deviation. Simulation results are shown to illustrate the e ectiveness and robustness of the proposed controller. This research proposes an indirect adaptive robust controller that can track the planned tracking trajectory smoothly and rapidly.

ControlLogix系统在煤气站的应用

为了改善操作条件,保证设备安全运行,设计了煤气站集中控制系统。利用ControlLogix系统,实现了18台煤气发生炉的集中控制。该系统采用3个处理器、2层网络结构,实现了集中控制、自动加煤、自动出灰、炉底饱和空气温度自动控制和电收尘等的控制。多个安全联锁措施和严谨的自动整流方案的应用,保证了电收尘的安全运行。

应用于储能系统的CLLLC谐振变换器控制策略研究

动态性能和运行效率是CLLLC谐振变换器的重要性能指标。针对传统电压闭环控制加入电流驱动同步整流后系统动态性能进一步变差的问题,提出一种谐振电流内环的电压电流双闭环变频控制策略,并给出双环控制和同步整流的综合控制方法。首先根据变换器的增益特性,分析电感比和品质因数对增益曲线和效率的影响,并据此进行谐振参数设计;其次根据不同谐振状态下的谐振电流特性实现同步整流;最后引入谐振电流内环控制,实现双环控制和同步整流的综合控制。仿真结果表明,所提综合控制策略能够产生精确的同步整流驱动信号,相比于传统电压闭环控制,能够显著改善变换器对负载扰动和电压扰动的动态性能。

海洋电磁发射机可控源整流电路动态性能优化

海洋电磁发射机在非理想状况工作时母线会产生冲击电压,严重时损坏开关管和滤波电容,为此提出一种混合控制策略。首先,基于dq坐标系的前馈解耦控制策略分析海洋电磁发射机可控源整流电路的动态性能,其次,通过理论证明负载扰动和无功电流iq≠0影响控制系统的动态性能,然后提出在dq电流解耦控制中引入瞬态直接电流思想的改进q轴混合控制方法,在dq电流解耦控制中引入负载电流前馈和无功电流iq≠0环节,改善了d轴电流id的响应速度,提高了控制系统的动态性能。最后,实验结果对比表明,混合控制方法在负载突变、直流侧电压给定值突变和船上柴油发电机电压跌落3种情况下,直流侧电压超调差最小,与最长调整时间相比减少了65%左右。

高层建筑竖向构件分离顶升纠偏关键技术研究

为了揭示高层建筑竖向构件分离顶升纠偏工艺的内在机理,给出了顶升系统的理论模拟方法,分别从千斤顶布置、顶升控制模式和顶升误差三个因素对结构内力的影响展开研究。通过对比各因素影响下结构的内力计算结果,总结了墙柱分离顶升纠偏设计、施工过程中的关键技术。结果表明:分离顶升过程中,单向双千斤顶布置形式不可取;“力为主、位移为辅”的双控顶升模式更适用于实际工程;顶升时的微小误差,可能会引起极大的结构附加内力,应通过理论分析和施工控制加以避免。

单相桥式全控整流电路晶闸管续流问题分析

本文以晶闸管单相桥式全控整流电路为研究对象,简述单相整流桥的工作原理及其特点,分析续流电阻在整流电路中的作用,分别从整流桥整流和逆变两种状态入手,研究续流电阻在不同工况下的工作原理及其对电路输出波形的影响,并通过Matlab仿真和现场试验对续流电阻的作用进行验证,以期为工程现场续流电阻的准确选取提供依据。

电液负载敏感分流同步纠偏驱动系统仿真分析

将负载敏感控制用于双缸同步驱动中,为提升系统的同步精度和效率,设计电液负载敏感分流同步纠偏驱动系统。在分析其工作原理的基础上,基于AMESim软件搭建此系统的仿真模型。在无同步纠偏系统参与工作时,分析偏载对系统分流精度和同步精度的影响规律;在所设计的同步纠偏系统参与工作时,分析不同偏载下液压缸的缸径相同与相差0.5 mm时的同步精度与位移损失效率。仿真结果表明:电液负载敏感分流同步纠偏驱动系统可通过损失较低的液压缸位移效率,使得同步精度得到极大的提高,此系统可用于高精度、高效率的同步驱动中。

Numerical Simulation of High-Power Synthetic Jet Actuator Flowfield and its Influence on Mixing Control

Detailed two-dimensional unsteady numerical simulation is carried out to investigate a high-power synthetic jet actuator flow field and its design characteristic. Simultaneously, mixing control mechanism of coaxial jets with actuators is also studied. Firstly, excitation frequency （rotating speed）, piston displacement and its exit slot width have effect on the controlling ability and controlling efficiency of actuator. With the invariable model and con- cerned parameters, the actuator becomes more desirable as the rotating speed increases. Average velocity and maximal velocity at the actuator exit section increase as the piston displacement enlarges or the exit slot width decreases. But the actuator does not always exhibit good performance with the narrower exit. Secondly, the synthetic jets also have the ＂push＂ effect on the coaxial jets, which results in the fluctuation of vorticity and temperature distribution of mixing flowfield. Finally, the employment of synthetic jet actuator can achieve mixing enhancement significantly.

基于DPC-MPC策略的潮流能永磁发电机PWM整流装置

为了改善潮流能发电系统的输出质量,使潮流能得到充分利用,深入分析了三相PWM整流系统的模型预测功率控制原理,推导了其中性能优化指标的计算方法。建立了该控制策略的Simulink仿真模型,搭建了潮流能永磁发电PWM整流系统实验平台,针对海流和负载这两类影响进行了充分的仿真与实验。实验结果证明了基于DPC-MPC控制策略的PWM整流装置的可行性。

铝模混凝土质量缺陷成因及整改管控措施探析

近年来,铝模在我国建筑业模板体系中快速、大面积推广使用。该支撑体系应用于装配式结构的混凝土施工过程中,在梁板柱与剪力墙一起浇筑时,由于其透气性较差,外加业界对其混凝土施工的工艺性能了解不够深入,设计和施工经验不足,容易导致现浇构件、预制构件与现浇构件的结合部位产生气泡麻面、蜂窝空洞等质量缺陷;但业界对此问题缺乏深入研究,对其经验教训未进行充分且有效的归纳总结。结合实际工程案例,对此类问题的成因和整改措施进行了深入探讨,提出的预防管控措施有效避免了此类问题的发生。项目分析处置经验完善可靠,为业界避免类似问题的发生,提供了有益的参考借鉴价值。

动态电压恢复器精准相控整流方法研究

动态电压恢复器是一种新型的电力电子装置,串联于电源和敏感负载之间,主要功能是治理电网电压扰动。动态电压恢复器主要由储能元件、双向变流器、静态转换开关和控制单元组成,电网电压处于稳定状态时,静态转换开关导通,电网通过此回路向负载供电;电网电压异常时,静态转换开关切换至由变流器为负载供电。在研制小容量动态电压恢复器过程中发现,储能元件(超级电容)相控整流充电过程中,出现交流侧充电电流突然急剧增大的现象,导致变流器IGBT模块损坏。针对出现的充电电流突增现象进行理论分析和仿真验证,根据分析验证结果更改设备控制策略和参数设置,解决了储能元件(超级电容)相控整流充电过程中电流激增的问题。

航空起发一体电机系统控制器的设计

提出了航空起发一体电机系统控制器的设计方案,采用矢量控制及弱磁扩速控制方式实现电动机起动控制,发电整流模块与起动模块分时共用MOSFET三相全桥主功率电路,采用专用芯片实现同步整流,采用BUCK电路并利用多相交错并联降低输出纹波,控制算法采用3零点3极点(3P3Z)补偿方法进行28V输出稳压控制,实现了航空发动机快速起动、永磁同步电机起动到发电的平稳转换以及28V直流电源输出。仿真研究表明系统的起动时间短、动态过程性能好,28V直流电源输出稳定,并联BUCK电路各支路均流理想,具有一定的工程应用价值。

超大断面矩形顶管姿态控制关键技术研究

针对深圳某地铁站矩形顶管隧道工程的超大断面、浅覆土、密贴顶进等特点,对顶管姿态控制难点进行分析,并对该工程采用的姿态测量、铰接纠偏、多螺旋机出土、多刀盘模式控制、注浆纠偏等多种技术结合的纠偏控制方案进行介绍。根据该工程实践表明:①顶管姿态偏移主要源于顶管开挖面及隧道两侧水土压力不平衡;②矩形顶管姿态控制重点是水平姿态以及垂直姿态控制;③通过采用铰接油缸控制、注浆纠偏、多螺旋机出土、多刀盘转动模式控制等技术,可有效控制顶管姿态。

基于UC3842反激式AC-DC开关电源设计

基于传统的反激开关电源使用二极管整流,开关电源损耗较大。设计了一种多路输出反激式AC-DC同步整流开关电源,输出分别为12 V和6 V。采用导通电阻极低的MOSFET代替二极管。介绍了开关电源的工作原理、UC3842内部结构、反激闭环控制以及同步整流。使用PSIM仿真软件搭建开关电源整体闭环模型,对电路进行仿真。结果表明,电路同步整流相比于二极管整流电路输出电压精度更高,同步整流输出电压、电流特性好、纹波小。

一种电流控制型并联24脉波整流器

为提高并联12脉波整流器谐波抑制能力及输出电流的动态性能,提出一种基于电流控制的双通道可控24脉波整流器。该整流器由并联12脉波整流器、带副边的平衡电抗器及单相整流桥组成,在输出脉波数倍增为24脉波的基础上,电流控制策略实现输出电流快速响应及可调。搭建MATLAB仿真模型进行全面仿真,验证了该方案有着常规24脉波整流器的谐波抑制能力的同时,带电流控制策略的电路具有更好的动态性能。