CPR1000型核电站给水泵事故瞬态分析

以CPR1000型核电站3×50%电动给水泵为研究对象,采用基于RELAP5和Simulink程序开发的CPR1000数字化仪控系统仿真试验台,详细计算分析了给水泵单泵故障和双重故障对反应堆运行的影响及相应的缓解措施。结果表明,给水泵单泵故障对反应堆运行的影响较小,各相关参数能够很快重回事故前的稳态工况。在给水泵双重故障情况下：初始核功率在75%FP及以下时,不会出现蒸汽发生器(SG)低-低水位;初始核功率高于75%FP、汽机初始负荷在90%FP及以下时,需将汽机负荷阶跃降至50%FP,才不会出现SG低-低水位;汽机初始负荷在90%FP以上时,建议停堆。     

Folding assembly of micro-actuators

A muscle-inspired linear actuator that combines many piezoelectric micro-actuator “cells” into a single functional unit is designed and fabricated via folding assembly technique. A bow-shaped epoxy beam structure amplifies the very small displacement of a thin film lead zirconate titanate (PZT) beam, generating a large orthogonal contractive displacement of 15.24 μm in a footprint of 515 μm. Then, three sets of three actuator cells are assembled out of plane by folding about thin gold hinges connecting each set. With the folded triplet array, an unblocked displacement of 5.16 μm and blocking force of 6.31 μN were obtained.     

主动隔振技术及其应用与发展

分析了主动隔振常用控制方法以及作动器的发展情况,指出控制方法与作动器技术未来的发展方向;对目前主动隔振技术的应用领域及其发展状况进行了分析,认为将主动隔振技术与传统被动隔振方法相结合是其主要的发展道路。     

基于GMA喷嘴挡板伺服阀的动态特性

提出基于GMA喷嘴挡板伺服阀的新结构,研制了GMM电－机械转换器及其喷嘴挡板伺服阀,分析其结构特点与需要解决的关键技术,建立动态数学模型。构建基于GMA喷嘴挡板伺服阀动态特性的试验系统,试验研究GMA喷嘴挡板伺服阀的阶跃和幅频响应特性,试验测得其阶跃响应上升时间为1 ms、幅频宽达680 Hz;将试验结果与仿真结果进行对比分析,两者基本吻合,论证动态数学模型的正确性。研究结果表明,用GMM设计新型电—机械转换器,可提高喷嘴挡板阀乃至整个电液伺服系统的频响和精度。     

Dynamic analysis of piezoceramic actuation effects on plate vibrations

This paper presents a simulation model for the active vibration control of a rectangular plate using piezoceramic elements of arbitrary shape. Experiments using multiple PZT patches were carried out to validate the model. An analysis was then undertaken to determine the dynamic effect of the piezoactuators. Numerical results showed that piezoactuators enhance the modal coupling of the structure under certain circumstances. Special attention should be paid to higher-order modes in both simulation and the development of active control strategies. Actuators of different shapes have been tested to show their influence on the dynamic behaviour of the structure. It was noted that actuators shapes affect the structure more in off-resonance regions than near resonance. This effect however remains weak as long as the actuators possess the same area and do not possess significantly different width to length dimensions.     

A fast tool servo design for precision turning of shafts on conventional CNC lathes

A technique for precision turning of shafts on conventional CNC turning centers is presented. The shaft is semi-turned on a conventional CNC lathe. The precision finish turning operation is delivered by a piezoelectric based fast tool servo which is mounted on the same CNC lathe's turret. The precision tool tip motion is delivered by a proposed sliding mode controller which is robust to changes in the cutting process and hysteresis in the piezo actuator. Sliding mode controller is also quick to compensate the cutting force disturbances, and keeps the tool tip at the desired location within the displacement measurement sensor resolution (±0.1 μm). The fast tool servo system is packaged in a PC, and its effectiveness is demonstrated on a bearing location turning.     

Latency and mode of error detection in a process industry

Licensee event reports (LERs) from an industry provide important information feedback about safety to the industry itself, the regulators and to the public. LERs from four nuclear power reactors were analyzed to find out about detection times, mode of detection and qualitative differences in reports from different reactors. The reliability of the codings was satisfactory and measured as the covariance between the ratings from two independent judges. The results showed differences in detection time across the reactors. On the average about 10% of the errors remained undetected for 100 weeks or more, but the great majority of errors were detected soon after their first appearance in the plant. On the average 40% of the errors were detected in regular tests and 40% through alarms. Operators found about 16% of the errors through noticing something abnormal in the plant. The remaining errors were detected in other ways. There were qualitative differences between the LERs from the different reactors reflecting the different conditions in the plants. The number of reports differed by a magnitude 1:2 between the different plants. However, a greater number of LERs can indicate both higher safety standards (e.g. a greater willingness to report all possible events to be able to learn from them) and lower safety standards (e.g. reporting as few events as possible to make a good impression). It was pointed out that LERs are indispensable in order to maintain safety of an industry and that the differences between plants found in the analyses of this study indicate how error reports can be used to initiate further investigations for improved safety.     

具有不确定性的主从机械手自适应模糊控制

针对具有不确定性且存在执行器未知约束的遥操作机器人系统，研究自适应模糊轨迹跟踪控制方案。该方案无需精确建立机器人遥操作系统的动力学模型，也不需要测量机械臂末端的运动参数与末端受到的外力。通过自适应模糊系统逼近未知的机器人动力学模型，利用运动学参数线性化特性构建预估机器人雅可比矩阵，辅以参数更新律实现跟踪目标的近似表示。此外，通过采用Nussbaum函数处理执行器受到的输入约束实现输入约束补偿。针对遥操作机器人系统主从端受到的相互作用力，借助自适应模糊系统，在控制律中添加模糊项实现对相互作用力的逼近，从而实现更为稳定、精确的轨迹跟踪。通过李亚普诺夫稳定性理论证明了闭环动力学系统是有界的，且位置误差收敛于零，仿真试验进一步证明了理论方案的有效性。     

Magnetic instability of giant magnetoresistance spin-valves due to electromigration-induced inter-diffusion

Electromigration-induced magnetic failures in NiFe/(Co)/Cu/(Co)/NiFe spin-valve (SV) multilayers have been investigated. Electrically stressed NiFe/Cu/NiFe SV multilayers showed a dramatic reduction of magnetic moment up to 41%, and a shift of interlayer coupling characteristics, while no obvious magnetic degradation was observed in the NiFe/Co/Cu/Co/NiFe SV multilayers. It was experimentally confirmed that the magnetic degradation of the NiFe/Cu/NiFe SV multilayers is primarily due to the formation of Ni-Cu intermixing caused by the electromigration-induced Cu spacer inter-diffusion. Furthermore, it was demonstrated that an ultra thin Co diffusion barrier at the NiFe/Cu interface is promisingly effective to improve the magnetic stability of NiFe/(Co)/Cu/(Co)/NiFe SV multilayers against electromigration.     

On the disturbance response and external stability of a saturating static-feedback-controlled double integrator

In this note, we identify a broad class of small but non-vanishing disturbances for which the state of a saturating static-feedback-controlled double integrator remains bounded.