浸没式参数激励摆波能转换装置能量俘获特性研究

引入参数激励摆的非线性机制,应用于波浪能发电装置,并根据实际波浪低频、低幅值激励特性,提出浸没式单摆波能转换装置,研究其在规则波中的能量俘获情况。基于势流理论,针对垂荡运动,建立非线性运动方程,进行数值求解,分析摆球质量比、激励频率、幅值和系统阻尼对能量俘获效率的影响,并与空气中单摆的能量俘获效率进行对比。结果表明:合理选取质量比,可降低浸没式参数激励摆固有频率;与空气中单摆相比,浸没式参数激励摆在低频、小振幅的波浪激励环境下,俘获能量频谱带宽更宽,发电功率更高。     

利用球形弹簧摆对输电塔风振控制的有限质点法

为了研究球形弹簧摆对输电塔结构的风致振动控制效果,通过分段等刚度梁单元建立输电塔简化模型。给出了空间梁系结构基于Timoshenko梁理论的单元内力计算公式,并应用有限质点法对简化模型及其与球形弹簧摆的耦合系统进行风致响应分析。一方面,球形弹簧摆由于内共振性质实现非线性能量阱,从而增加振动抑制频带的宽度,提高了鲁棒性;另一方面,球形弹簧摆和结构的非线性耦合,使得顺风向的振动能量部分转移到横风向,尽管增大了横风向响应,但是降低了结构的总体响应。计算结果表明球形弹簧摆减振效果非常好,当将其安装在除塔顶外的三个位置时,位移最大值和加速度均方根减振率分别为32.5%~41.7%和35.7%~65.2%。保持质量比和安装位置不变,验证了球形弹簧摆具有较宽的设计频带。使用球形弹簧摆可以显著减小位移标准差,有利于降低结构的疲劳损伤风险。     

Quasistatic field responses of fluxoids in an Y1Ba2Cu3O7−δ film

The quasistatic magnetic field responses (typically 0.8 Hz) of fluxoids in ac-axis oriented Y₁Ba₂Cu₃O_7?δ (Y123) film have been studied using a computerized mechanical pendulum at 77 K. The resonance frequence of the pendulum is significantly shifted to higher values due to the interaction between the Y123 film and a magnet mounted on the pendulum. The contribution of the magnet-superconductor interaction to the shift of the squared resonance frequency shows, in a certain range, a logarithmic dependence on the driving force (proportional to the amplitude). The present results are consistent with the previous studies on the bulk Y123 materials for different configuration.     

Time measurement technique for internal friction studies with a torsion pendulum

A new technique for measuring internal friction by the free decay method using time measurements with a torsion pendulum is described. It has been applied for the automation of measurements with a Kê type pendulum. The method enables rapid and precise measurement of internal friction. Results of the grain boundary peak for aluminum are presented for illustration.     

三线摆方程简化及其共振问题研究

对于广泛用于测定不规则刚体转动惯量的三线摆方法,讨论了其方程的适用性和避免共振的条件。通过对扭振方程的推导与分析,得出了扭振方程线性化的条件;揭示了三线摆结构参数、被测刚体惯性与几何参数与对方程线性化的影响。通过比较扭振频率与摆振频率,得出了二者耦合的条件。这种耦合将导致惯性参数测试试验失败。结合一个测试实例,具体分析了发生振动耦合时被测刚体惯性参数与系统设计参数之间的关系,由此进一步阐述了三线摆设计与应用中的注意事项。     

Design and Implementation of a State-feedback Controller Using LQR Technique

The main objective of this research is to design a state-feedback controller for the rotary inverted pendulum module utilizing the linear quadratic regulator (LQR) technique. The controller maintains the pendulum in the inverted (upright) position and is robust enough to reject external disturbance to maintain its stability. The research work involves three major contributions: mathematical modeling, simulation, and real-time implementation. To design a controller, mathematical modeling has been done by employing the Newton-Euler, Lagrange method. The resulting model was nonlinear so linearization was required, which has been done around a working point. For the estimation of the controller parameters, MATLAB LQR function has been utilized. Simulation has been performed for the designed controller and it also has been implemented and tested over the real inverted pendulum. From the results, it is vivid that the designed controller keeps the inverted pendulum in an upright position and rejects the disturbances and falling under gravitational force by adjusting the rotation of the horizontal link.     

晃动液体单摆模型动力学参数的频域辨识

本文研究晃动液体动力学参数的频域辨识法,详细推导了晃动液体的等效单摆模型,研制了贮箱模型、悬挂装置和高灵敏度测力计。通过测量贮箱位移和激振力,求得其位移对激振力的频率特性数据。首先用误差校正法辨识传递函数系数,然后用数学规划法确定模型的动力学参数。同时,通过测量晃动液体的扰动力矩,直接推算单摆模型的悬挂点位置。辨识出的单摆模型动力学参数值与按位势理论计算的数值接近。研究结果表明本文采用的频域辨识法有效。     

An alternate method for determination of brittleness of ceramics and polymers

As opposed to a pendulum scratching test for the determination of brittleness parameter for ceramics and polymers, this paper proposes an alternate brittleness parameter based on indentation analysis. The important advantages are that (i) no elaborate experiments are needed, and (ii) the proposed brittleness parameter has physical implications. The proposed parameter is as effective as the pendulum test for categorizing the brittleness of ceramics and polymers.     

The influence of boundary conditions on the loading of rectangular plates subjected to localised blast loading – Importance in numerical simulations

A series of localised blast loading experiments are performed in order to understand how the experimental set-up influences the impulse imparted to a plate. The imparted impulse is measured using a ballistic pendulum. The experimental results show that for both rigid and deformable plates the impulse measured by a ballistic pendulum increases as the height of the boundary (clamps) increases. Significantly, it is found that although the measured impulse varies as a function of the boundary height, the plate deformation is unchanged. This suggests that not all of the impulse measured by the ballistic pendulum resulted in plate deformation. Therefore, in numerical and analytical modelling, the total impulse from the ballistic pendulum should not simply be applied as a centrally localised pressure load.     

海洋波力发电倒置摆系统的非线性振动实验研究

摘要：本文以振动基座上的倒置摆系统为研究对象,对该系统受竖向简谐激励作用时的非线性振动特性进行实验研究,探讨该系统应用于海洋波力发电的技术可行性,为海洋波力开发利用提供依据。实验设计倒置摆转动角位移采集系统,通过测试确定系统的阻尼、固有频率等,为数值模拟提供依据并指导倒置摆系统的振动实验。通过实测振动时域数据得到系统振动频谱及相图,证明该系统存在大阻尼条件下的大周期运动、共振状态下的周期振动和倒置摆稳定吸引域,这表明该模型具有海浪波力能源吸收好,消耗少的特点,同时表明该模型具有高效的动力输出能力．因此,振动基座上倒置摆模型在开发利用海洋波力能源发电中具有十分重要的应用前景。     

Torsion dynamometers

Conclusions Pendulum dynamometers are preferably used in the best machines for testing materials with static loads.The existing designs of torsion dynamometers have as yet no substantial advantages as compared with those of the pendulum type.Further attempts in producing low-inertia torsion dynamometers for static machines should aim at providing torsion bars with large twist angles,of the order of 0.5–0.7 rad.Torsion dynamometers in combination with inertialess indicators are preferable to those of the pendulum type for use in machines intended for high-speed loading and deformations.     

Decoupling of Confined Normal 3He

Anodic bonding was used to fabricate a 10 mm diameter × 640 nm tall annular geometry suitable for torsion pendulum studies of confined ³He. For pure ³He at saturated vapor pressure the inertia of the confined fluid was seen to be only partially coupled to the pendulum at 160 mK. Below 100 mK the liquid’s inertial contribution was negligible, indicating a complete decoupling of the ³He from the pendulum.     

Chaotic dynamics and reversal statistics of the forced spherical pendulum: comparing the Miles equations with experiment

The forced spherical pendulum is of intrinsic interest to dynamicists as well as to geophysicists as a simple mechanical analogue of the polarity reversals of the Earth's magnetic field. The system displays chaotic dynamics involving irregular reversals of its direction of motion, both in terms of its angular momentum and of its direction of precession. Here, we analyse the difference between angular-momentum and precession reversals and compare the results of experimental work that has been performed on chaotic reversals in a laboratory pendulum with numerical simulations of the Miles equations that represent the pendulum dynamics; we find good agreement.     

非线性悬吊质量摆对输电塔减振控制的研究

针对悬吊质量摆减控制研究中小摆角线性分析的局限性,本文提出考虑悬吊质量摆大摆角非线性特性来计算结构体系动力响应的方法,将传统分析中的悬吊质量摆的线性刚度修正为非线性。以一输电塔为例,通过线性和非线性计算结果对比可知,当摆角过大时线性计算方法不满足线性小摆角条件,而非线性计算方法则可很好模拟质量摆在大摆角下的响应。通过参数分析讨论了正弦激励周期、摆长及质量比对输电塔减震率的影响。选取三条不同场地地震记录,计算输电塔附加质量摆体系的地震响应,结果表明在不同场地条件下,输电塔均具有明显的减震效果。     

自然对流气体的摆特性及其在传感器中应用

根据自然对流气体具有摆的特性,从而提出气体摆新概念。分析了密闭腔中自然对流气体的浮升力,给出浮升力与温度变化的关系式。试验结果表明,与固体摆、液体摆一样,利用气体摆原理亦能检测加速度和倾角。     

Pendulum sensor for location of vertical by using polarization measurements

We consider a fast contactless sensor for information about the position of a pendulum relative to a platform; the sensor is based on the use of polarization modulation of a light beam. We investigate problems on reducing the moment of force due to friction in the axial system of the pendulum. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 18–21, January, 1998.     

利用扭秤进行空间干涉仪的地面测试技术

空间干涉仪作为下一代重力卫星、空间引力波探测计划的核心部件之一,其灵敏度远高于目前电容式读出的惯性传感器。但由于空间干涉仪涉及技术细节过多,需在地面研制阶段接受大量测试,而低频测试频段以及极低噪声环境的苛刻要求成为当前地面测试阶段的最大挑战之一。该文介绍以悬挂扭秤为核心技术的地面测试平台,其在竖直方向可由悬丝平衡地球所带来的引力影响,而在水平方向可模拟准自由落体状态。选用经过特殊设计而成的悬挂扭秤作为测试对象,可将地面测试中的主要噪声——地面振动噪声降低3~4个量级,使得加速度噪声在观测频段可低至10−13 m·s^−2·Hz^−1/2@mHz,已达到目前该频段的测量极限,该技术也是目前国际上公认的空间干涉仪地面研制阶段的最佳测试平台之一。     

Der Pendelfurcher – ein Prüfgerät zur Untersuchung des Formänderungsverhaltens duktiler Werkstoffe bei dynamischer Beanspruchung

The pendulum furrower – a test device for the investigation of the deformation behaviour of dilatable materials at dynamical loading Within this contribution a new test device is presented, allowing the investigation of the deformation behaviour of dilatable materials at shock loading. The base equipment is a commercial pendulum striking apparatus, equiped with a Brinell ball at the end of the pendulum. From the adjustable feeding of the rigid fixed flat specimen and the pendulum path through the material of the specimen follows automatically an arc-shaped wearing track. By means of the energy of friction, registered during the oscillation of the pendulum and the following measuring of the volums of the furrows new special charakteristic values of the materials can be find out.     

Nonlinear differential equations with fractional damping with applications to the 1dof and 2dof pendulum

Summary. Existence, uniqueness and dissipativity is established for a class of nonlinear dynamical systems including systems with fractional damping. The problem is reduced to a system of fractional-order differential equations for numerical integration. The method is applied to a non-linear pendulum with fractional damping as well as to a nonlinear pendulum suspended on an extensible string. An example of such a fractional damping is a pendulum with the bob swinging in a viscous fluid and subject to the Stokes force (proportional to the velocity of the bob) and the Basset-Boussinesq force (proportional to the Caputo derivative of order 1/2 of the angular velocity). An existence and uniqueness theorem is proved and dissipativity is studied for a class of discrete mechanical systems subject to fractional-type damping. Some particularities of fractional damping are exhibited, including non-monotonic decay of elastic energy. The 2:1 resonance is compared with nonresonant behavior.