高速数字跟踪位置测量系统警觉“振荡”的研究

高速数字跟踪位置测量系统在机床工作台妄动时容易产生振荡、从而使工作台出现抖动而不能正常工作文章中分析了测量系统初态振荡的原因，介绍了初态“低速化”的防振荡措施，即通过限制测量系统跟踪控制器中的速度。     

Exploiting natural dynamics for gait generation in undulatory locomotion

ABSTRACT

Robotic vehicles inspired by animal locomotion operate via periodic body movements. The pattern of body oscillation (gait) can be mimicked from animals, but understanding the principles underlying gait generation would allow for broad, flexible applications beyond nature's design. We hypothesise that travelling-wave oscillations observed in undulatory locomotion can be characterised as a natural oscillation of the locomotion dynamics and propose a formal definition of the natural gait for locomotion systems. We identify the essential dynamics and define the mode shape of natural oscillation by the free response of an idealised system. We then use body-environment resonance to define the amplitude and frequency. Explicit formulas for the natural gait are derived to provide insight into the mechanisms underlying undulatory locomotion. Examples of a swimming leech and a fictitious swimmer illustrate how undulatory gaits similar to those observed can be produced as the natural gait and modulated to achieve different swim speeds.     

振动场对聚合物熔体在异型材挤出口模内的流动影响

利用ANSYS软件对受口模入口处周期性振动的压力驱动的非牛顿幂率聚合物熔体在“Y”型异型材挤出口模内的流动过程进行了三维等温数值模拟。研究了入口压力的振动参数对流场压力和速度的影响情况。结果表明：流场中压力和速度的振动频率与入口压力的振动频率相等，而流场压力和速度的振幅随入口压力振幅的增大或者频率的降低丽增大，亦即低频高幅的振动容易得到较大的振动幅值。研究还表明流场速度的振动滞后于压力，且速度振动的衰减也比压力的衰减慢。     

振动技术在塑料挤出成型中的应用

介绍了振动技术在塑料挤出加工中的应用,分析了振动力场在挤出过程中的作用及其机理,并讨论了振动力场对聚合物挤出成型制品力学性能的影响。     

Design of robust electric power system stabilizers using Kharitonov’s theorem

A robust power system stabilizer (PSS) is proposed as an effective way to damp-out oscillations in electric power systems. Oscillations of small magnitude and low frequency, linked with the electromechanical models in power systems, often persist for long periods of time and in some cases present limitations on the power transfer capability. The proposed PSS is designed according to Kharitonov’s extremal gain margin theory. It has the following advantages: (i) it is based on simultaneous stabilization of limited number of extreme plants, (ii) the control design can be based on frequency response analysis techniques (root locus diagrams or Nyquist plots) and (iii) the resulting controller is a low-order phase-lead compensator, which is robust to the change of operating points. The proposed power system stabilizer is tested through simulation experiments.     

Oscillation theorems for second-order nonlinear neutral differential equations

The purpose of this paper is to study the oscillation of the second-order neutral differential equations of the form

(a(t)[z^′(t)]^γ)^′+q(t)x^β(σ(t))=0,     

Oscillation criteria for second order quasilinear neutral delay differential equations on time scales

In this paper, we consider the second-order quasilinear neutral dynamic equation

(r(t)|Z^Δ(t)|^α−1Z^Δ(t))^Δ+q(t)|x(δ(t))|^β−1x(δ(t))=0,     

高频热合机电磁辐射抑制技术的研究

根据国家电磁兼容标准(GB4824-2004-2A),针对传统高热合机在主频、二倍频和三倍频处的辐射强度严重超标的问题,结合高频热合机的工作原理对其电磁兼容性进行深入的研究,通过采取三种措施:1)在热合机机头部位设计制作谐振电路衰减器,通过建立陷波槽和反作用场的方法,削弱和吸收热合机机头强辐射电磁场,使电磁泄漏辐射场强得到衰减;2)采用电磁辐射屏蔽衰减技术,对高频功率的铜片馈线进行屏蔽;3)重新设计高频振荡电路,减少振荡输出的谐波分量.试验结果证明:采取对电磁辐射抑制措施后高频热合机的输出频率符合国家规定的频率标准,解决了目前高频热合机工作时的电磁泄露辐射污染问题,带来了很好的社会、环境和经济效益.     

结晶器振动类型与特点分析

结晶器振动有几种类型，每种类型有其固有的优缺点。合理的正确使用相应的结构，能够降低投资，减少维修维护成本，进而提高经济效益。     

连铸保护渣道动态压力的研究

通过Bikerman公式确定弯月面的形态，计算保护渣道内的压力随结晶器振动、拉坯参数的规律。发现随保护渣粘度、拉坯速度、振动的负滑脱时间的增加以及保护渣道的出口宽度的减小，保护渣道内的最大正压、最大负压均有增加，其中保护渣道内的压力受渣道出口宽度的影响最大。