压电加筋壁板结构的多模态自抗扰振动控制

针对压电加筋壁板结构多模态主动控制时存在振动模型和外界干扰难以确定等问题, 提出一种不依赖结构数学模型的多模态自抗扰振动控制方法. 首先,采用多回路的扩张状态观测器实时估计其他模态的输出叠加、输入耦合、高次谐波以及外界激励等组成的集总干扰, 并将估计值通过前馈补偿的方式消除干扰对整个控制系统的影响. 然后, 针对每个控制模态设计独立的PD反馈控制器. 为了提高整个控制系统的振动抑制性能, 结合多模态振动控制的特点, 引入一种具有实际意义的性能指标函数. 并基于此性能函数, 提出基于logistic映射的自抗扰振动控制器参数自动优化方法. 最后, 利用dSPACE半实物仿真平台, 搭建了四面固支壁板结构的压电振动控制实验系统.最后, 多模态干扰激励的实验结果表明了所提的多模态自抗扰振动主动控制方法的有效性.     

Four-leg independent mechanism for MEMS microrobot

In this paper, the development of a quadruped micro-electro mechanical system (MEMS) microrobot with a four-leg independent mechanism is described. As the actuator mechanism inside small robot bodies is difficult to realize, many microrobots use external field forces such as magnetism and vibration. In this paper, artificial muscle wires that are family of shape memory alloy are used for the force of the actuator. The artificial muscle wire shows the large displacement by passing the electrical current through the material itself. The double four-link mechanism is adopted for the leg system. The link mechanism transforms the linear motion of the artificial muscle wire to the foot step-like pedaling motion. The location of the backward swing motion is lower than that of forward swing motion. This motion generates the locomotion force. As a result, the total length of the constructed quadruped MEMS microrobot was 6 mm. The microrobot could perform similar gait pattern changes as the quadruped animal.     

An actively controlled harmonic force generator

Low frequency harmonic force generators (HFG) are broadly utilized in a variety of applications, in some cases for generating desired harmonic force excitations and in others for canceling vibration caused by harmonic forces. Among various HFGs, those with rotating eccentric masses offer attractive weight-to-force ratios. This advantage becomes more pronounced especially when the operating frequencies are low (10–30 Hz) and the harmonic force amplitudes are high. A novel design is the topic of this paper which deploys four rotating eccentric masses, which are deployed to adjust the three key characteristics of the resultant harmonic force: the amplitude, the frequency and the phase angle.     

Identification of a human walking force model based on dynamic monitoring data from pedestrian bridges

A general investigation procedure for the vibration serviceability of pedestrian bridges is accomplished by comparing the dynamic response of structures to vibration effects on serviceability limiting states. The purposes of this study were to investigate the dynamic response characteristics of pedestrian bridges and to develop a human walking force model to assist in the development and design of pedestrian bridges. Human walking force parameters were identified by a genetic algorithm (GA) from experimental forced vibration data. The results of the dynamic response obtained by the GA were in agreement with the experimental results. Therefore, the GA system was useful in the identification of pedestrian walking forces, and from the experimental and calculated results, it is considered that the walking force model identified by the GA is substantially accurate.     

磁悬浮效应的人行天桥振动参数测量研究

将磁悬浮技术应用于振动测量,设计了磁悬浮人行天桥振动监测系统,对振子的受力进行了分析,建立了振子的动力学方程.通过实测获得测试系统输出电压与桥梁振动幅度的关系.用虚拟仪器数据处理方法得到被测振动信号的功率谱.分别测量了自振状态、桥下有车经过、单人通过和多人通过的振动波形.通过波形分析、功率谱分析得出人行天桥的振动情况.实测表明:磁悬浮人行天桥振动测试系统测量频率下限可达到1 Hz,频率测量范围在1～190 Hz.     

An analysis of the effects of the leg-spacing on spectral response of offshore structures

The authors have applied a computer-based model to perform spectral analysis of jacket platforms. The analysis is carried out in a consistent manner using the finite element method. The proper estimation of the phasing effects of the ocean waves on structural responses is dependent, inter alia, on the accurate calculation of nodal forces. Using the finite element approach the vector of nodal forces can be most accurately computed taking into account the varying distributed loads along the structural members. The model, developed by the first author, calculates cross-receptances of response for all degrees of freedom that enable the phase effects due to the spatial extent of the structure to be properly accounted for. This model includes the phase effects of wave loadings on the platform and it can thus give a more accurate estimation of response spectra which are generally required for design calculations; this is far more accurate than calculating wave loadings on an equivalent cantilever as is often done.     

基于FPGA的色选机下料振动器振动状态检测系统设计

为了快速采集色选机下料振动器的振动参数,简单直观地获取振动器的振动状态,有效地改善振动器的工作性能,设计了一种基于FPGA的色选机下料振动器振动状态检测系统。系统主要由振动加速度传感器、FPGA处理板卡和上位机显示器件组成,通过传感器的振动数据采集、FPGA处理板卡的数据处理与通信以及上位机的数据接收,该系统能够在线显示振动器工作时的振动波形,并给出相关参考信息。经采样与通信过程中的时序仿真以及振动检测平台的实验测试,该系统能够在线得出振动器工作时的振动加速度波形,并给出最大振动加速度,通过相应的转化可作为振动器改进的参考依据,因此具有较高的应用价值。     

两项激励下石墨环氧叠层板的组合共振特性研究

对两项激励下石墨环氧叠层板的非线性特性进行了研究.根据板的非线性运动方程,应用伽辽金法得出了矩形叠层板在两项均布简谐激励力作用下的无量纲化达芬型非线性振动微分方程,用多尺度法对层叠板组合共振微分方程求解,得出发生组合共振的各种情形,对组合共振的稳定性进行了分析,得到稳态运动下的幅频响应方程.代入有关参数,分析了不同参数...     

汽车车内噪声主动控制系统仿真

降低汽车空腔的振动,是抑制汽车车内噪声的有效途径之一;以激振器、作动器和控制器等为主要部件,搭建了简化的汽车车内噪声主动控制系统,该系统通过将汽车空腔模型简化为板件,以减弱板件振动为目标,实现了汽车车内噪声主动控制;采用简谐正弦及余弦信号作为激振器发出的激励,用于模拟板件的初始振动,控制器通过采用模糊控制算法直接控制压电陶瓷作动器的振动,压电陶瓷作动器的振动用于抑制板件的振动,完成了汽车车内噪声主动控制系统仿真;仿真结果表明,研究采用的汽车车内噪声主动控制系统,使汽车空腔振动降低23%,为解决由汽车发动机和动力总成的振动所引发的汽车车内噪声问题提供了一个有效途径。     

一种新型手臂力触觉反馈装置的设计与实现

力触觉是重要的非视觉信息来源之一，通过触觉向人类传递丰富的信息被广泛应用于各个领域。为解决基于振动的力触觉反馈中所存在的振动器与皮肤之间接触力不可调和重复穿戴时接触力不一致而影响振动感知的问题，提出了一种利用气囊来调节振动器与皮肤之间的接触力的方法，并以此设计了一种新型手臂力触觉反馈装置。为验证装置的有效性，设计了不同的振动强度识别实验。实验结果表明，对于参与实验的受试者，振动器与皮肤之间的接触力对振动强度的识别的影响是显著的，在气囊内外气压差为15 mbar时，振动强度的识别率最高，为76.67%。     

An investigation on the relationship between grip, push and contact forces applied to a tool handle

Owing to the strong dependence of the health risks associated with vibration exposure of the human hand and arm on hand force, a laboratory study was conducted to develop a methodology for measurement of the contact force at the tool handle–hand interface, and to identify the relationship between the contact force and the hand grip and push forces. A simulated tool handle fixture was realized in the laboratory to measure the grip and push forces using compression/extension force sensors integrated within the handle and a force plate, respectively. The contact force was derived through integration of the interface pressure over the contact area. These were measured using a capacitive pressure-sensing grid. The measurements were performed with 10 male subjects and three circular cross-section handles of different sizes under different combinations of grip and push forces. The hand–handle interface pressure data were analyzed to derive the contact force, as functions of the constant magnitudes of the grip and push forces, and the handle size. The results suggest that the hand–handle contact force is strongly dependent upon not only the grip and push forces but also the handle diameter. The contact force for a given handle size can be expressed as a linear combination of grip and push forces, where the contribution of the grip force is considerably larger than that of the push force. The results further suggest that a linear relation can characterize the dependence of the contact force on the handle diameter. The validity of the proposed relationship is demonstrated by evaluating the magnitudes of errors between the estimated contact forces with the measured data for the range of handle diameters, and grip and push forces considered in the study.

Relevance to industry

The methodology proposed in this study can be applied to measure the effective hand–handle contact force at workplaces for assessing the health risks associated with exposure to hand-transmitted vibration exposure and hand–wrist cumulative trauma. The relationship proposed in the study could be effectively applied for estimating the hand–handle contact force from known grip and push forces that are conveniently and directly measurable in laboratory studies involving vibration analyses of the human hand, power tools and relevant vibration attenuation devices. It is expected to be most useful in field applications, where it could provide an estimate of the range of magnitudes of the hand-grip force applied to the handle of an actual tool, which is quite difficult and expensive to measure. The relationship is also expected to contribute to the on-going standardization efforts for defining a correction factor to account for the effects of hand force on the vibration transmission and hand injuries.     

双层预紧式6维力传感器预紧力对精度影响分析

针对传统Stewart结构6维力传感器性能的不足,设计并研制了一种双层预紧式6维力传感器,并进行了精度分析与实验研究.首先,介绍了该6维力传感器的结构特点,基于螺旋理论建立了其数学模型以及预紧力的数学描述形式.为了提高传感器的测量精度,在分析预紧支路结构的基础上,通过增大预紧力来降低由于预紧支路结构变形产生的误差.其次,对不同预紧力下预紧支路的结构变形进行了有限元仿真.最后研制并开发了6维力传感器样机和标定系统,进行了不同预紧力情况下的标定实验.通过增大预紧力,传感器的最大Ⅰ类误差和Ⅱ类误差分别由满量程的2.73%、2.43%降低到0.41%、0.64%.实验结果表明,增大预紧力有效地降低了预紧支路变形带来的测量误差,提高了传感器的测量精度,从而验证了理论分析与仿真的正确性.     

Interaction model between elastic objects for haptic feedback considering collisions of soft tissue

The simulation of organ–organ interaction is indispensable for practical and advanced medical VR simulator such as open surgery and indirect palpation. This paper describes a method to represent real-time interaction between elastic objects for accurate force feedback in medical VR simulation. The proposed model defines boundary deformation of colliding elements based on temporary surface forces calculated by temporary deformation. The model produces accurate deformation and force feedback considering collisions of objects as well as prevents unrealistic overlap of objects. A prototype simulator of rectal palpation is constructed on general desktop PC with a haptic device, PHANToM. The system allows users to feel different stiffness of a rear elastic object located behind another elastic object. The results of experiments confirmed the method expresses organ–organ interaction in real-time and produces realistic and perceivable force feedback.     

超高速电梯系统动态仿真分析

电梯的振动是影响舒适性的最主要因素,针对4.0 m/s 超高速电梯系统,以轿厢- 轿架-导轨-钢丝绳耦合系统为研究对象,建立垂直系统振动动力学模型,结合机械系统动力学自 动分析虚拟样机技术,通过建立钢丝绳动力学模型、添加导轨与导靴之间的接触力、水平振动 激励及垂直振动激励,建立电梯整机虚拟样机模型,设定约束与驱动,进行动态特性仿真分析。 仿真结果表明,电梯垂直振动加速度、水平振动加速度等性能指标满足要求,为超高速电梯的 开发提供了设计依据。     

Vibration induced low back disorders--comparison of the vibration evaluation according to ISO 2631 with a force-related evaluation

Long-term vibration stress can contribute to degenerative changes in the joints of the human body, especially in the lumbar spine. An important factor in the development of these diseases is given by the forces transmitted in the joints. Because the forces can hardly be measured a biomechanical model was developed which simulates the human body in the standing and the sitting posture. The vibration properties of the model were adapted to the transfer function provided in the standards and the literature. With the model the compressive forces at the driving point of the body, in the leg joints, and in two motion segments of the spine were simulated under a vertical pseudo random vibration. Transfer functions between the accelerations of the ground or of the seat and the forces were computed. Furthermore, based on the transfer function between seat acceleration and compressive force in the spinal motion segment L3-L4 weighting factors were derived. By means of these factors characteristic vibration values were computed for 57 realistic vibration spectra measured on 17 machines and vehicles. The consideration of the forces resulted in a stronger weighting of low-frequency vibrations compared to the weighted acceleration as suggested by ISO 2631-1. In order to enable an assessment of the health risk a force-related guidance value was derived which amounts to 0.81 ms(-2) (rms).     

柔性机械臂的变结构振动控制研究

当机械臂的质量很轻,尤其是空间应用场合,机器人系统将受到高度柔性限制并且不可避免地产生机械振动.本文为了证实提出的控制不期望残余振动的方法,设计并建立了柔性机器人实验平台.控制方案采用交流伺服电机通过谐波齿轮减速器驱动柔性机械臂,利用粘贴在柔性臂上的压电陶瓷片(PZT)作为传感器来检测柔性臂的振动.对由于环境激励,尤其是在电机转动(机动)时由于电机力矩产生的振动,采用了几种主动振动控制器包括模态PD控制,软变结构控制(VSC)和增益选择变结构方法,进行柔性臂的振动主动控制实验研究.通过实验比较研究,结果表明采用的控制方法可以快速抑制柔性结构的振动,采用的控制方法是有效的.     

Magnetically induced vibration of a flexible rotating disk-spindle system due to the internal magnetic force arising from the spindle motor of a HDD

This paper investigates the magnetically induced vibration of a flexible rotating disk-spindle system and stationary stator-base due to the internal excitation of the local magnetic force arising from the spindle motor of a HDD. A three-dimensional magnetic finite element model of the spindle motor is developed, and the Maxwell stress tensor method is applied to calculate the local magnetic force acting on the stationary teeth and rotating permanent magnet of the spindle motor. Also, a three-dimensional structural finite element model is developed and local magnetic force is applied to teeth and permanent magnet. The simulated forced vibration of the base plate matched well with the measured one. The dominant frequency component of local magnetic force is the 12th harmonic corresponding to the number of poles, but the dominant frequency component of vibration is the 36th harmonic corresponding to the least common multiple of the number of poles and slots because the 12 and 24th harmonics in local force are canceled out when they are summed up along the air gap. The 12th, 24th and 36th harmonics of the axial vibration are mostly affected by the axial magnetic force, and the amplitudes of those harmonics are increased with the increase of stator eccentricity.     

振动与力加载耦合的电液伺服控制

振动与力加载耦合的电液伺服系统具有集成模拟被测试件在振动与加载耦合工况下动态性能的优势,针对振动模拟对力加载系统产生的干扰多余力问题,提出了一种力干扰观测器,以提高加载力跟踪精度.首先,建立了振动与力加载耦合的电液伺服控制系统的数学仿真模型;其次,利用递推增广最小二乘算法辨识了力加载系统闭环传递函数;然后,利用零相差跟踪技术设计了力加载系统的前馈逆模型;最后,设计了力干扰观测器,搭建了水平向振动与力加载耦合的电液伺服系统实验台,仿真和实验验证了提出的力干扰观测器可有效降低由于振动扰动而产生的干扰多余力.     

正交各向异性叠层板的非线性主共振分析

研究了在四边简支的边界条件下,正交各向异性矩形叠层板在横向简谐激励作用下的非线性主共振及其稳定性问题．在给出了正交各向异性叠层板的振动微分方程的基础上,利用伽辽金法导出了相应的达芬型非线性强迫振动方程．应用平均法对主共振问题进行求解,得到了系统在稳态运动下的幅频响应方程．基于李雅普诺夫稳定性理论,得到了解的稳定性判定条件．作为算例,分别给出了不同条件下,系统运动的幅频响应曲线图、振幅-激励幅值响应曲线图和动相平面图,并对解的稳定性进行了分析,讨论了各参数对系统非线性振动特性的影响．