Exact Finite Dimensional Feedback Control via Inertial Manifold Theory with Application to the Chafee–Infante Equation

A class of nonlinear parabolic partial differential equations is considered, and an exact finite dimensional feedback control law is designed in order to force the systems to behave in a prescribed way. The feedback law is obtained via inertial manifold theory by reducing the system to finite dimensions. The control achieved is exact, as opposed to approximate, as obtained in a previous work. The result is applied to the Chafee–Infante equation, a one-dimensional scalar reaction-diffusion equation, with distributed control.     

线性系统模态控制及其时滞补偿

对线性系统模态控制及其时滞补偿进行研究。模态控制分控制全部模态和控制有限模态两种情况 ,时滞补偿采用移相补偿。最后结合算例对两种控制模态下的控制效果和控制有限模态时的时滞补偿进行了数值计算和结果对比     

Pendulation Reduction in Boom Cranes Using Cable Length Manipulation

A technique is proposed to reduce payload pendulations using the reelingand unreeling of the hoisting cable. The payload is modeled as a pointmass, the cable is modeled as a rigid link, and the assembly, aspherical pendulum, is attached to the boom tip. An excitation isapplied to the assembly at the boom tip. The motion of the payload isdescribed using two-dimensional and three-dimensional models. Ourresults demonstrate that cable-length manipulation can be used to reducepayload pendulations due to near-resonance excitations. Significantreductions can be obtained via an appropriate choice of thereeling/unreeling speed. We also demonstrate the limitations inherent intwo-dimensional modelings of a crane.     

主动振动控制中传感／作动元件配置问题的全局优化方法研究

提出了一种主动振动控制中作动／传感元件位置的复合优化方法，它能有效地解决全局优化配置问题；通过对单点并置问题的优化，证明了该优化方法的有效性，并对多点配置问题也具有一定的参考价值。     

磁悬浮列车系统的随机最优控制

本文根据磁悬浮列车和车行道的结构特点，将总系统模型按分块原则分成列车、磁执行环节和车行道系统，并在平衡点附近对非线性方程线性化处理，形成末加控制的总系统的状态方程，它是一组考虑外干扰情况下线性时变系统模型。而基于电磁关系原则建立的磁悬浮列车系统模型在末加控制状态下是不稳定的，为了保证列车的行驶舒适性、稳定性及可靠性，承重磁铁与导向磁铁必须加以控制。附加控制方程后，就形成了被控制的总系统的状态方程，从而实现车、磁及车行道模型的有机组合。对于实际工程问题，被控制的总系统的动力学性质由于维数较高，直接计算比较困难，本文采用计算机进行数值仿真，利用随机最优控制理论，对系统悬浮气隙和垂向加速度的变化规律进行了研究，并通过实例给出时变系统的仿真结果。     

Precise control for vibration of rigid–flexible mechanical arm

In the present paper, based on the nonlinear dynamic equation of spacial flexible mechanical arm with dual-link bar, the method of linear quadratic control is used to eliminate the remain vibration of mechanical arm. In the process of computation, the traditional differential algorithm is replaced by the time integration method. Because of taking the more precise time-intervals in the given time-interval and avoiding a lot of computational difficulties, the method of this paper has the characteristics of high precision and unconditional stable. For a typical structure, the precise control law is obtained and the advantages of the algorithm in this paper are shown.     

机翼/外挂颤振主动抑制的控制律研究

本文介绍了对机翼/外挂系统的颤振抑制控制律的研究。并用三种控制律的结果进行了风洞实验验证。结果表明:控制律的设计是成功的,理论计算与实验结果吻合良好。 文中重点介绍了两种控制律,它们都是以现代控制理论为基础。首先,把最优控制理论与颤振分析的状态空间法相结合,得到状态反馈。然后导出不同的输出反馈。文中,还讨论了该系统的阵风减缓和稳定裕度。 为对比起见,还给出了在同一模型上,用气动能量概念方法导出的控制律。由此,可看出它们在颤振抑制效益上的差异。     

Regulating Molecular Recognition with C‐Shaped Strips Attained by Chirality‐Assisted Synthesis

Chirality‐assisted synthesis (CAS) is a general approach to control the shapes of large molecular strips. CAS is based on enantiomerically pure building blocks that are designed to strictly couple in a single geometric orientation. Fully shape‐persistent structures can thus be created, even in the form of linear chains. With CAS, selective recognition between large host and guest molecules can reliably be designed de novo. To demonstrate this concept, three C‐shaped strips that can embrace a pillar[5]arene macrocycle were synthesized. The pillar[5]arene bound to the strips was a better host for electron‐deficient guests than the free macrocycle. Experimental and computational evidence is provided for these unique cooperative interactions to illustrate how CAS could open the door towards the precise positioning of functional groups for regulated supramolecular recognition and catalysis.     

Sonochemical Synthesis of Gold Nanoparticles by Using High Intensity Focused Ultrasound

The sonochemical synthesis of gold nanoparticles (GNPs) with different shapes and size distributions by using high‐intensity focused ultrasound (HIFU) operating at 463 kHz is reported. GNP formation proceeds through the reduction of Au³⁺ to Au⁰ by radicals generated by acoustic cavitation. TEM images reveal that GNPs show irregular shapes at 30 W, are primarily icosahedral at 50 W and form a significant amount of nanorods at 70 W. The size of GNPs decreases with increasing acoustic power with a narrower size distribution. Sonochemiluminescence images help in the understanding of the effect of HIFU in controlling the size and shapes of GNPs. The number of radicals that form and the mechanical forces that are generated control the shape and size of the GNPs. UV/Vis spectra and TEM images are used to propose a possible mechanism for the observed effects. The results presented demonstrate, for the first time, that the HIFU system can be used to synthesise size‐ and shape‐controlled metal nanoparticles.