断续型位式控制

本文研究了断续型位式控制系统的特点及其振荡的抑制问题,其中包括利用反馈校正抑制自激振荡和外加周期信号抑制自激振荡,并根据分析的结论,应用于一个实际的电阻炉温控系统,获得了较高的控制精度和控制质量。其结果说明,采用本文提出的若干措施,可以对现行的位式控制器的控制质量,从根本上加以改进,从而达到满意的效果。     

水轮发电机组轴系横向自振特性的有限元分析

对水轮发电机组轴系的横向振动的自振特性进行了分析。采用有限元法,考虑陀螺效应,给出了计算模型,编制了计算程序ROTOR。用ROTOR计算了三座电站的轴系,结果与美国西屋公司的相应软件的计算结果相吻合。特别结合对隔河岩水电站轴系的分析,对工程设计提出了建议。     

虚实结合负反馈放大电路性能分析实验

负反馈放大电路实验是模拟电子技术中涉及知识点较多的实验,而传统的负反馈放大电路实验受时空的制约,教学效果不理想。本文采用的虚实结合负反馈放大电路实验系统解决了线下实验和现有仿真软件器件为虚拟器件的不足,能够全面地对电路的性能进行分析和研究。本电路系统学生可以随时随地进行实验操作与实验复习,教学方法灵活多样,提高了教学质量。     

自激脉冲谐振射流喷嘴研发成功

文章阐述了硬质合金自激脉冲谐振射流喷嘴的开发背景、技术原理,通过硬质合金自激脉冲谐振射流喷嘴与传统喷嘴在现代油气钻井中使用效果的分析、比较,指出前者克服了现有连续射流喷嘴持续能量小的缺点,提高了射流的瞬时打击力、有效喷射距离和射流到达井底时的水力能量,为钻探工业提供了创造性的钻探工具,促进我国乃至世界钻探工业提升到了一个新的平台.     

气动自振荡机构的研究

将电学中的脉宽调制的方法引入到气动系统的流量控制,作为降低能耗的手段,并已由试验验证将间歇供气方式应用于气动喷嘴吹除杂质颗粒较连续供气方式更节能。提出一种为气动喷嘴提供间歇气流的自振荡机构。该机构采用阀式结构并以弹簧振子机构为基础,为使阀芯在弹簧力的作用下做周期振动,用压缩气体作用在阀芯上产生推力克服摩擦力,并从理论上分析稳定的周期振动产生的机理,振幅大小受到阀腔充放气基准时间的影响,当基准时间短时,振幅变小甚至不能稳定振动。通过设计弹簧的弹性系数和阀开口的位置,产生不同频率和占空比的间歇气流。通过仿真对振荡产生的机理做出研究,通过试验验证仿真结果,试验结果与仿真结果吻合。分析阀口打开过程中以及全开时,气体压力损失的机理,并结合试验数据计算本机构的效率为9%。     

奥地利WFL车铣中心功能缺失故障一例

奥地利WFL公司生产的车铣中心自投入使用以来一直无法进行重量较大轴类工件的加工,经过对主轴原理的深入研究和反复试验,找出原因在于设备功能的缺失,并采取有效方法恢复了机床功能.文中详细介绍了问题的分析方法和处理.     

Design of novel biomimetic polymer gels with self-oscillating function

We report a novel biomimetic gel that undergoes autonomous swelling-deswelling oscillations without on-off switching of external stimuli, similar to heartbeat. The mechanical oscillation of gel was produced via oscillating chemical reaction, called the Belousov-Zhabotinsky (BZ) reaction. We have prepared an ionic gel consisting of the cross-linked poly(N-isopropylacrylamide) chain to which ruthenium tris(2,2′-bipyridine), a catalyst for the BZ reaction, was covalently bonded. The BZ reaction occurring within the gel matrix generates periodic redox changes of the catalyst moiety. This chemical oscillation is converted into the mechanical oscillation of the polymer network. As a result, the gel exhibits a periodical swelling-deswelling change. The self-oscillating behaviors of the gel were investigated in detail. When the gel size is smaller than the chemical wavelength, the redox change occurs homogeneously in the gel. In this case, the volume change is isotropic and the mechanical oscillation synchronizes with chemical oscillation without a phase difference. The period and amplitude can be controlled by changing the outer substrate concentrations. In the case of rectangular shape, chemical wave propagates along the length of the gel. The wavelength and velocity depend on the reaction rate of autocatalytic process as well as the diffusivity of the activator. The dynamic behavior that locally shrunken (or swollen) parts propagate was observed, similar to the peristaltic motion of worms. By using lithography technique, a ciliary motion actuator made of the gel has been demonstrated. These self-oscillating gels may be useful in a number of important applications to intelligent biomaterials such as pulse generator or chemical pacemaker, auto-mobile actuators or micropumps with peristaltic motion, device for signal transmission, etc.     

电火花加工控制用辅助电源的设计

介绍一种应用于电火花加工控制和检测系统中的辅助电源的工作原理、参数设计及性能指标。     

Self-oscillation of polymer and photo-regulation by introducing photochromic site to induce LCST changes

We have developed polymers and gels with autonomous self-oscillating function by utilizing the Belousov–Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of poly(N-isopropylacrylamide), in which ruthenium tris(2,2′-bipyridine) is copolymerized as a catalyst for the BZ reaction. Under the coexistence of the reactants, the polymer undergoes spontaneous cyclic soluble–insoluble changes or swelling–deswelling changes (in the case of gel) without any on–off switching of external stimuli. In this study, spirobenzopyran was introduced into the self-oscillating polymer as the photochromic site. Under acidic condition necessary for the BZ reaction, photochromism of the spirobenzopyran occurs and the lower critical solution temperature of the polymer solution shifts to lower temperature with isomerization by photo-irradiation. As a result, on–off switching of the soluble–insoluble self-oscillation for the polymer solution is possible by photo-irradiation.     

Self-oscillating and chaotic behaviour of a PI-controlled CSTR with control valve saturation

The time response of a PI-controlled continuous stirred tank reactor (CSTR), where a first order irreversible reaction occurs, is analysed in this paper. The parameters of the PI controller and the saturation of the cooling water temperature flow are used as parameters to show that self-oscillations and chaotic dynamics can appear. The conditions under which self-oscillation occurs are investigated taking into account heat generation, heat removal and the variation of eigenvalues of the linearized system at the equilibrium points, respectively. Also, the appearance of a Silnikov type homoclinic orbit, giving chaotic dynamics, is realised. The existence of a new set of strange attractors with PI control has been verified and the sensitivity to the initial conditions is also analysed.