双向压电驱动的二维快速伺服刀架

快速伺服刀架能够提供精确、快速的微纳米级运动。为了获得双向和二维运动,该文研制了一种双向压电驱动的二维快速伺服刀架。该刀架采用对称结构设计,结合柔顺放大机构和位移解耦机构,末端执行机构实现较大的输出位移,同时减小耦合位移。基于伪刚体模型,建立快速伺服刀架的静力学和动力学模型,得到机构的输出位移、输出耦合比、最大应力和固有频率。通过有限元仿真验证了模型的正确性。最后,采用电火花线切割加工快速伺服刀架原型样机,并搭建了实验测试系统。实验结果表明,快速伺服刀架在x、y方向的位移放大率分别为3.56和3.57;输出耦合误差分别为1.26%和1.00%,装配压电陶瓷驱动器后系统在x、y方向的一阶固有频率均是270 Hz,系统动态性能良好。     

基于多体动力学与有限元的油缸系统疲劳寿命研究

针对动力稳定装置关键部件疲劳寿命问题,文中采用基于多体动力学与有限元的方法,以动力稳定装置的夹钳油缸系统为研究对象,进行了仿真分析。该方法利用ADAMS软件对动力稳定装置进行多体动力学分析,得到夹钳油缸系统的受力载荷谱。将受力载荷谱导入有限元软件Ansys Workbench中,对夹钳油缸系统进行瞬态动力学分析。根据瞬态动力学分析结果,利用疲劳分析软件NCODE计算夹钳油缸系统的疲劳寿命状况。仿真分析结果表明,夹钳油缸系统疲劳寿命最薄弱的地方在其根部位置,最小循环次数为8.807×10⁵。     

车载状态下测风激光雷达的浮筏减振研究

为了减弱振动对车载激光雷达测量精度和稳定性的影响,借鉴浮筏减振系统在船舶领域的成功使用,对其进行了浮筏减振布局设计。采用多刚体动力学建模方法对系统在简谐激励下的减振性能进行了分析,得出系统各处减振器参量对系统减振效果的影响。根据选定的减振参量,结合所选车型,经过计算得到激光雷达主体的传递率峰值,有效避开了汽车运输过程中的激振频率,且几乎在有效的激振频率范围内传递率曲线都小于1;经计算得到冲击作用下的振动量程没有越过减震器的有效减震范围,符合理论要求;通过振动状态下激光雷达和探空气球所测风速数据的对比,验证了减振设计对保证测量精度的效果;通过静止和模拟振动状态下激光雷达的锁频效果对比,证明了浮法减振设计在车载系统中应用的可靠性。结果表明,浮筏减振设计应用于车载测风激光雷达是合理的、成功的。     

光学元件磁流变加工不确定度误差工艺方法

为减少磁流变抛光过程中误差对加工精度的影响,实现光学元件磁流变高精度加工,采用一种不确定度误差工艺方法对加工中的误差进行抑制。通过对磁流变加工过程中的位置误差和去除函数误差进行不确定度分析,在理论分析与实验分析的基础上进行验证实验。由仿真与实验结果可知,加工中面形误差与中频误差均存在3.5 nm的不确定度误差值,通过验证实验,得到了加工后的面形误差RMS值为20 nm,中频误差RMS值为14 nm。结果表明,采用误差不确定度的方法可优化加工工艺流程,减少误差对加工过程的影响,可以达到不确定度下的面形精度。该方法为磁流变高精度确定性加工以及面形误差与中频误差的抑制问题提供了一种解决方案。     

基于星敏感器的跟瞄系统在轨标定方法

为分析空间跟瞄机构光轴误差问题,建立了星上跟瞄系统模型,介绍了跟瞄系统不同坐标系间的转换形式,分析了跟瞄机构光轴的误差形式,提出了多星敏光轴标定算法,介绍了标定过程中的坐标转换过程和误差计算方法,通过仿真验证了算法的正确性,并比较了随机误差对光轴标定的影响,同时在引入星敏感器全天识别算法的情况下对双星敏标定算法的正确性进行了验证,对精确度进行了分析。经仿真,双星敏算法标定精确度可达25”以内,比例系数K值小于0.01,在跟瞄相机与星敏同时工作的情况下解决了跟瞄相机的在轨标定问题。     

光电设备的三维减振系统设计

分析了振动对光电设备的影响,针对光电设备中光学装置的减振设计,提出了三维减振设计构想。设计了一套既有隔振缓冲能力,同时也具备抑制角振动功能的三维减振系统。对三维减振系统的抗振动设计和抗冲击设计进行了分析计算,并通过台架试验验证了减振特性,能够满足光电设备的使用要求。     

一种跟瞄系统角误差的测量方法

介绍了跟瞄系统角误差一种测量方法的原理、数据处理方法以及测试结果。待测的跟瞄系统由光电跟踪引导系统和随动天线组成,先通过动力飞艇对跟瞄系统的跟瞄精度进行了测试,再利用无人飞机对跟瞄系统的跟瞄精度进行对比验证。测试得到的数据表明,该测试方法简单有效、费用低,可用于类似系统的角精度测量。     

某舰载雷达发射机机柜抗冲击仿真分析

针对某舰载雷达发射机机柜抗冲击设计要求,进行了机柜的抗冲击仿真分析。利用动力学分析方法,在抗冲击仿真软件中建立了机柜的仿真模型,在显式动力学分析步中将冲击谱时域曲线直接作用于机柜上的连接部位,并根据减振系统的实验数据计算得到发射机机柜在垂向、横向和纵向设计冲击谱作用下的冲击响应。结果显示,最大应力均不超过材料抗拉强度的90%,满足强度设计指标,为后续抗冲击试验提供了理论依据。     

光电平台无角位移减振机构运动分析

分析了光电平台的工作环境和角振动对成像质量的影响，应用空间机构学原理和减振理论，设计了一种既具减振功能又能抑制角位移的无角位移减振机构。对减振机构的减振机理及运动特性进行了分析，并利用三维建模软件和MSC．Visual Nastran 4D仿真分析软件对该减振机构进行了三雏实体仿真分析，通过输出的仿真数据及曲线检验无角位移减振原理的正确性。     

旋翼型无人直升机非线性飞行动力学模型与实验研究北大核心CSCD

以转旋型无人直升机为研究对象,文中对其飞行动力学进行了数学建模,针对主尾桨、旋翼、机身、垂尾以及平尾创建气动力学模型,根据各部件力矩及气动力,通过微分方程模拟运算机体运动姿态,实现对旋翼型无人直升机非线性飞行动力学模型的创建。把飞行控制系统、遥控遥测软件、后台模型解算、前台仿真控制台集成为一个完整的闭环系统,降低仿真系统复杂性,提高仿真有效性。在进行旋翼型无人直升机起飞、航路飞行、着陆仿真试验时,旋翼型无人直升机在飞行过程中侧偏较小,实际飞行航线基本覆盖给定航路。这表明该文对旋翼型无人直升机非线性动力模型具有较高的置信度,这对控制律设计、仿真验证比较适合,仿真系统实时性达到预期效果。     

Control and experimental study of 6-DOF vibration isolation platform with magnetorheological damper

Vibration is an inevitable excitation in the operation of the mechanical system, which reduces its reliability and service life. Therefore, a heavy-duty 6-DOF semi-active vibration isolation system (VIS) with magnetorheological (MR) damper was proposed in this paper. Firstly, A MR damper with large output force of 27 kN was designed. The properties test results showed that the dynamic range (the adjustable multiple of damping force) of the damper is as high as 15, which has excellent dynamic performance. And a Bouc-Wen model which can accurately describe the mechanical behavior of the MR damper was established. Secondly, the prototype of the MR 6-DOF vibration isolation platform (VIP) with cubic structure was developed. Thirdly, a on-off semi-active control strategy was proposed for the MR 6-DOF VIP. The numerical simulation results showed that the semi-active VIS can effectively isolate vibration in the working frequency domain. Finally, the vibration experiment on shaking table was carried out. The test results showed that the designed heavy-duty MR 6-DOF semi-active VIP can control the load's attitude in real-time according to the system state. Compared with the current of 0 A, the vibration isolation effect of the on-off control is improved by 63.27% in the resonance region. The MR 6-DOF VIP can effectively reduce the vibration transmitted to the isolated system through the platform.     

基于磁流变减震器的起落架着陆建模及仿真

磁流变减震器是一种半主动控制的阻尼装置,可显著改善起落架的减震效果。针对自行设计的多环形槽结构磁流变减震器,根据流变力学原理,建立了减震器力学模型,并据此建立基于Matlab的起落架系统动态力学模型。对于不同的机身质量和着陆垂直速度分量,得到励磁电流与振动幅值、频率及稳定时间等参数的关系。仿真结果表明,选用合适的励磁电流,可方便地控制振动参数,达到较理想的减震效果。     

Optimal design of MR damper via finite element analyses of fluid dynamic and magnetic field

In the last decade many researchers have been carried out on semi-active control systems, a large number of academic publications have been presented. Semi-active control systems which are used the magnetic field controlled fluid have been shown significant improvements by the researchers. In the study, a design optimization method that has been carried out for the objectives of target damper force and maximum magnetic flux density of an MR damper has been presented. Finite element methods, electromagnetic analysis of magnetic field and CFD analysis of MR flow, have been used to obtain optimal value of design parameters. The new approach that is use of magnetic field and MR flow together and simultaneously has specified optimal design values. Two optimal design of MR damper obtained have been verified with experimental study by manufacturing and testing of the dampers.     

Electrical harmonic oscillator with MR damper and energy harvester operating as TMD: Experimental study

In the study we propose and examine a novel concept, eMR-TMD as we call it, replacing a standard tuned mass damper (TMD) by an electrical harmonic oscillator (RLC circuit). The concept employs an electromagnetic energy harvester (EEH) to extract energy from vibrations, an RLC circuit in which serial resonance phenomenon occurs and a magnetorheological (MR) damper. The approach does not require modifications to the structural part of the system, i.e. no additional mass and spring are needed. The essence of the concept relies on the introduction of a tuned RLC circuit between the EEH coil and the control coil of the MR damper. The RLC circuit parameters we select in such a way so that the electrical resonance frequency is close to or equal mechanical resonance frequency in which the eMR-TMD concept is applicable. Moreover, it is required that the RLC circuit's quality factor is greater than 1 and then the voltage activated the MR damper is higher than the EEH induced voltage at the resonance frequency. Fulfilling the criteria allows tuning the current in the MR damper's control coil so that it is maximized at resonance frequency and minimized at high excitation frequencies. To prove the concept's potential we test the engineered eMR-TMD system experimentally under sinusoidal excitations. We compare the obtained test results with those acquired with the MR damper powered directly from the EEH (dMR-EEH concept) and when the MR damper's control coil is not powered (without TMD concept).     

Evaluation of Electrorheological Fluid Dampers for Applications at 3-T MRI Environment

This paper evaluates the use of electrorheological fluids (ERFs) within a magnetic resonance imaging (MRI) environment. ERF is a semiactive variable impedance material, which could be used as an alternative type of resistive force/torque generation or in combination with other actuators as a damper/clutch to modulate the output force/torque of the actuator. In this paper, an ERF damper/brake is introduced and its magnetic resonance (MR) compatibility is examined at a 3-T MR imaging environment by measuring the output performance of the damper and the SNR of the MRI images. The experimental results showed that damper's resistive force generation while positioned within the MRI is almost the same as that in normal operation. The signal-to-noise investigation was performed both with a phantom and human. The results indicated that the ERF damper did not affect the MRI images when it was operated over 30 cm away from the MRI's RF coil. We hope that the synthesis and tables presented in this paper can facilitate the choice of ERF brake actuation principle to various applications in an MR environment.     

Simple class-AB voltage follower with slew rate and bandwidth enhancement and no extra static power or supply requirements

A simple modification of the MOS voltage follower is introduced that provides it with efficient class-AB operation. The modified circuit has dynamic output currents and bandwidth that are essentially larger than the conventional MOS voltage follower. This is achieved with the same static power dissipation, very small additional circuit complexity and lower distortion. Experimental verification of all these characteristics is provided.     

Power-efficient class AB CMOS buffer

A novel class AB unity gain voltage buffer is proposed. It is based on the use of quasi-floating gate (QFG) techniques in a super source follower topology. The circuit achieves dynamic current boosting with accurate control of quiescent currents and without penalty in supply voltage requirements or quiescent power consumption. Measurement results of the circuit, fabricated in a 0.5 mm CMOS technology, show a slew-rate enhancement by a factor 18.5 against the conventional super source follower, for the same bias current and supply voltage.     

H∞ control of electrorheological suspension system subjected to parameter uncertainties

Vehicle suspension is normally used to attenuate unwanted vibration from various road conditions. The successful suppression of the vibration leads to the improvement of ride comfort as well as steering stability of the vehicle. One of attractive candidates to formulate successful vehicle suspension is to use electrorheological (ER) damper. This paper presents robust control performances of ER suspension system subjected to parameter uncertainties associated with sprung mass of the vehicle and time constant of the ER damper. After identifying dynamic bandwidth of a cylindrical ER damper operated with two different ER fluids (one has fast response characteristic, while the other slow response characteristic), a quarter car model is established by incorporating with time constant of the damping force. A robust H_∞ controller, which compensates the sprung mass and time constant uncertainties, is designed in order to suppress unwanted vibration of the vehicle. Control responses such as vertical acceleration of the sprung mass are presented in time and frequency domains. In addition, the effect of time constant of the damping force on the vibration control performance is investigated by undertaking a comparative work between fast and slow dynamic characteristics of the ER damper.     

磁共振心肌标记图像左心室壁边缘检测

磁共振标记（MR Tagging）技术于90年代初提出，作为一种有效的无创性检测手段，得到不断的研究和改进。它针对人体软组织（如心脏）的形变进行测量，定量分析其运动轨迹，从而判断其功能状况的好坏，具有较高的实用价值。论文提出一种结合形态学、增强的启发式图搜索和区域生长法进行磁共振心肌标记图像左心室壁分割的方法，实验证明这种方法可以很好地分割出磁共振心肌标记图像左心室心肌的内外边缘，并可以进一步用于提取心肌标记，分析心肌运动轨迹。     

Learning cooperative dynamic manipulation skills from human demonstration videos

This article proposes a method for learning and robotic replication of dynamic collaborative tasks from offline videos. The objective is to extend the concept of learning from demonstration (LfD) to dynamic scenarios, benefiting from widely available or easily producible offline videos. To achieve this goal, we decode important dynamic information, such as the Configuration Dependent Stiffness (CDS), which reveals the contribution of arm pose to the arm endpoint stiffness, from a three-dimensional human skeleton model. Next, through encoding of the CDS via Gaussian Mixture Model (GMM) and decoding via Gaussian Mixture Regression (GMR), the robot’s Cartesian impedance profile is estimated and replicated. We demonstrate the proposed method in a collaborative sawing task with leader–follower structure, considering environmental constraints and dynamic uncertainties. The experimental setup includes two Panda robots, which replicate the leader–follower roles and the impedance profiles extracted from a two-persons sawing video.