三轴转台速率的数字实现

本文针对用22位绝对式的光电编码器同时形成速率和位置信号的任务,设计了一种实用数字测速方法.从原理上进行了分析,并设计了硬件电路和软件程序.该方法使转台结构紧凑,增加了数字化程度.实践证明了其工程有效性.     

重力梯度测量中光栅角编码器安装误差的影响及分析

旋转加速度计式重力梯度仪中的台体旋转误差会影响梯度测量精度。若以光栅角编码器作为旋转控制的角度测量元件,其安装误差会产生相应的旋转控制误差。为此,需要对光栅角编码器安装误差的产生机理进行分析,了解其对旋转加速度计式重力梯度仪测量精度的影响程度。利用光学技术方法测量光栅角编码器安装误差所引起的角速度和角加速度的变化,最后通过角位置补偿修正光栅角编码器安装误差以减小运动不平稳性对重力梯度测量的影响。实验表明该方法对光栅角编码器进行补偿可以有效减小码盘安装误差对旋转控制的影响。     

光电倍增管脉冲性能研究

采用外腔式电光开关，调制主动照明探测光源，使光电倍增管处于脉冲工作状态下，以提高光电倍增管的输出幅度和动态范围，改善信号的信噪比，同时避免样品和探测器长时间受强激光照射。对滨松H6780光电倍增管进行了调试，使其线性输出电流由静态的0．1mA提升到脉冲状态的4．4mA，信噪比提高到6．6倍。     

小型自准直式光电传感器性能测试系统

为标定小型实心转子静电陀螺仪用自准直式光电传感器的性能，设计了一个专用的性能测试系统。传感器性能测试表明，被测小型自准直式光电传感器的分辨率优于1^#，传感器性能测试系统满足使用要求。     

静电陀螺数字式小角度读出系统研究

本探讨了一种用于静电陀螺的小角度光电信号读出的全数字方案，通过对比、分析和讨论，说明数字化静电陀螺小角度读出方案的优越性，并提出了针对静电陀螺光电读出系统随机误差的修正算法。     

转台速率系统的相差／电压转换问题

本文介绍由相差／电压转换原理构成的一种高精度速率系统的原理及硬件电路的实现，并对各环节的关键技术进行了详细阐述。经实际调整证明，本方案容易实现，可靠性高，克服了增量编码器速率系统中使用锁相回路的若干缺点。     

闪光照相图像光电接收系统的设计

在讨论数字图像信息几个概念的基础上，分析了闪光照相图像的基本特征和对图像接收系统的基本要求。介绍图像光电接收系统的组成和它们的功能。分析了各环节的噪声，建立了理想成像上图像光电接收系统的设计方程，说明图像接收繁育民照相系统参数和样品照相测试要求之间的关系，文中还引用信息论的观点，分析了模糊图像的接收问题，认为图像模糊的结果是图像对比度下降，从而需要更细小的分辨等级 是需要更高的信噪比才能记录。据此     

中国惯性技术学会光电技术专业委员会第五次学术交流会在深圳市召开

中国惯性技术学会光电技术专业委员会第五次学术交流会暨重庆惯性技术学会第九次学术交流会于2002年11月8日至12日在深圳市举行，与会代表共36人。中国惯性技术学会名誉理事、中国电子科技集团第26研究所所长吴旭峰研究员专程到会祝贺并在开幕式上讲了话，他希望把本次会议开成一次团结的大会，和谐的大会，胜利的大会。 开幕式结束后，与会代表进行了学术交流。会议征集论文43篇，会上交流27篇。这些论文充分体现了我国光电惯性技术的最新进展，以及采用的新技术、新工艺和新应用等。与会代表还对如何加快我国光纤陀螺工程化和可生产性等问…     

颗粒群冲击诱导光伏电池性能衰减的特性与机理

光伏电池由于具有较高的光电转化效率,在沙漠等太阳能充足的地方被广泛应用。但在沙尘长期冲击的环境下,光伏电池内部结构易出现累积损伤,使光电转化效率大幅降低。因此,研究颗粒群冲击条件下光伏电池的力-电行为具有重要意义。基于分离式霍普金森压杆,发展了一种驱动较大尺寸颗粒群高速冲击的实验方法,并系统测量了不同冲击条件下,多晶硅光伏电池的损伤行为与光电转化性能衰减规律。研究结果表明,随着颗粒直径、冲击速度和数密度的增加,光伏电池的光电转换效率快速降低;颗粒冲击后光伏电池表现出三种典型的损伤模式,并给出了对应的应力阈值条件。基于实验测试结果,发展了多晶硅光伏电池颗粒群冲击损伤诱导光电转化性能退化模型,为沙砾冲击环境下光伏电池光电性能衰减规律提供了有效的预测方法。     

陀螺经纬仪光电积分法中几个关键问题的技术途径

陀螺经纬仪光电积分测量系统,在我国属首次研制,已获成功。本文论述了研制中光电检测器的线性度及电压稳定度、光强、陀螺马达的指向精度、悬带零位稳定性、系统温度漂移误差等几个关键问题的技术途径。实践证明,光电积分法测量,可以自动精密寻北;缩短了观测时间;增强了抗干扰能力,便于在野外和机动条件下使用。这种测量方法在陀螺经纬仪中具有普遍推广应用价值。     

超磁致伸缩车削加工刀架特性实验分析

利用光栅测微传感器(DG-10)和自行开发研制的优化后的超磁致伸缩车削加工刀架,对不同预压力、电流强度下刀架性能进行实验研究。实验中分别由压力传感器和改进后的控制电路调整所加预压力、电流的大小,通过数据采集系统记录光栅测微传感器所测得的磁致伸缩量。实验结果表明:在不同预压力下,刀架输出位移随着激励电流的增大而增大,直到达到饱和;同时在最大工作电流作用下,刀架的输出位移随着预压力的增大而增大,但当预压力增大到一定数值后,刀架的输出位移随着预压力的增大而减小。利用最小二乘曲线拟合、线性回归等数学方法得出了刀架在最大工作电流下,预压力与磁致伸缩量之间的拟合曲线及函数多项式,并确立了最佳工作预压力。建立了最佳工作预压力下电流与磁致伸缩量之间的函数关系式。通过误差分析看出理论分析和实验结果吻合的很好。     

Calibration of encoder indexing of a redundantly actuated parallel mechanism to eliminate contradicting control forces

This paper presents the kinematic calibration of a two degree-of-freedom redundantly actuated parallel mechanism (RAPM), with the aim of eliminating contradicting control forces (CCF). The kinematic errors in the RAPM induce CCFs, especially in the case of decentralized individual position control, which is the standard control method used in industrial applications. The encoder indexing errors of the actuated joints are known to be of strong influence on the CCFs. Therefore, it is believed that the CCFs will be eliminated if the encoder indexing errors are corrected. We proved this through experiments. We performed the calibration using a projection technique, wherein we projected tracking error terms onto orthogonal complementary terms of the constraint Jacobian between the independent joints and actuated joints. Using this projection technique, the effect of tracking error terms from the joint stiffness and external force is eliminated. During the calibration process, the tracking errors in the actuated joints are measured. Using these errors, we derived the optimal values of the encoder indexing error by minimizing the objective function. We verified the calibration result by comparing the CCFs measured before calibration with those measured after calibration, for the case of individual PID position control. Our results confirmed that the calibration procedure of encoder indexing errors successfully reduces the average norm value of CCFs from 366 N to 13 N.     

A joint encryption and error correction scheme based on chaos and LDPC

Although some cryptosystems based on error correction code have been presented, the security and efficiency must be overcome before it can be realized. In this paper, a novel method of combined encryption and error correction based on hyperchaotic system and lower-density parity check (LDPC) code is proposed to provide both of the security and efficiency. The proposed system adopts a pseudorandom sequence generator based on hyperchaotic system for scrambling the plaintext and constructing the dynamic permutation box. The message is encoded by the LDPC encoder after it was scrambled and then encrypted by the permutation box. Different permutation patterns generated for different message blocks help to provide high security, while the encoder helps to provide capacity of error correction. MATLAB simulations reveal that the proposed scheme is more secure and effective than the existing joint encryption and error correction coding scheme. Moreover, the full error correction ability of LDPC is kept without confliction. So, the proposed scheme is suitable for secure communication system.     

Proper uncertainty bound parameter to robust control of electrical manipulators using nominal model

This paper focuses on the uncertainty bound parameter (UBP) to design the robust control of electrical manipulators. The UBP is commonly obtained by considering the worst case of uncertainties in bounding functions. However, too high estimation of UBP may cause saturation of input, higher frequency of chattering in the switching control laws, and thus a bad behavior of the whole system, while too low estimation of UBP may cause a higher tracking error. A proper UBP is preferred to improve the performance of robust control system. A simple, less dependent and proper UBP is proposed based on the nominal model of electrical manipulator and feedbacks of joint accelerations. This work is motivated by recent experimental results in measuring acceleration by optical encoder. Modeling of an electrical manipulator with presence of uncertainties is presented for control purposes. The proposed robust control is justified by stability analysis.     

Smoothing and statistical evaluation of laser Doppler velocimetry data of turbulent flows in rotating and reciprocating machinery

 Arbitrarily time-distributed velocity information acquired by laser Doppler velocimeter systems needs special care when evaluated wrt. the mean velocity and the components of the Reynolds stress tensor. In rotating machinery, the arrival time information can be uniquely mapped to the angular position ϕ of the runner blades by using encoder signals relating a fixed runner position to an arrival time. It is convenient to statistically evaluate the velocity information of the detected particles in an angular window [ϕ₀−Δϕ/2,ϕ₀+Δϕ/2] in order to obtain mean velocities and turbulence values for an angular position ϕ₀. This approach has the inconvenience that turbulence values calculated from standard deviations are influenced by a possible variation in the mean velocity in the evaluation window. Other problems that arise with this “evaluation window” method are the influence of unevenly angular-distributed velocity information on the mean velocity or the poor resolution of maxima and minima of the mean velocity, which is similar to the problem pointed out by Jakoby et al. but being of second-order nature. In this paper, different improvements in the “evaluation window” method wrt these problems based on ideas found in a paper by McDonald and Owen are presented. A confidence interval calculation, generalizing the methods of Boutier, for all calculated values is included, which allows an appropriate window size Δϕ to be chosen for each particular situation. The different methods are compared using examples from wake flows of axial hydraulic turbomachinery measured in air and water. Received: 7 July 1999/Accepted: 18 November 1999     

A phase-locked high-speed real-time interferometry system for large amplitude unsteady flows

A high-speed phase-locked interferometry system has been designed and developed for real-time measurements of dynamic stall flow over a pitching airfoil. Point diffraction interferograms of incipient flow separation over a sinusoidally oscillating airfoil have been obtained at framing rates of up to 20 kHz and for free stream Mach numbers of 0.3 and 0.45. The images were recorded on 35 mm ASA 125 and ASA 400 films using a drum camera. Special electronic timing and synchronizing circuits were developed to trigger the laser light source from the camera and to initiate acquisition of the interferogram sequence from any desired phase angle of oscillation. The airfoil instantaneous angle of attack data provided by an optical encoder was recorded via a FIFO data buffer into a microcomputer. The interferograms have been analyzed using software developed in-house to get quantitative flow density and pressure distributions.Mr. N.J. Brock and Mr. B.J. Weber of Aerometrics. Inc. in preparing the laser specifications are gratefully acknowledged.The project was supported by US Air Force Office of Scientific Research through grants, AFOSR-ISSA-89-0067 and AFOSR-MIPR-92-0004. Additional support was received from the Army Research Office grant ARO-MIPR-125-93. The support and encouragement of Dr. S.S. Davis, Chief, Fluid Mechanics Laboratory Branch and the help provided by     

A fluidic-muscle driven force-controlled parallel platform for physical simulation of virtual spatial force-displacement laws

Described in this paper is a six-legged Stewart-Gough parallel platform driven by a relatively new type of fluidic muscles. The advantage of the platform is that it is virtually free of stick-slip effects. Thus, the device is well-suited for fine-tuned force control and for physical simulation of virtual force-displacement laws. The legs of the platform are of type RRPS and are equipped with a coaxial coil spring and a fluidic muscle providing push and pull forces. Each leg is equipped with a force sensor, a pressure sensor, and a magnetostrictive position encoder. The control for the platform consists of six control loops for the six operated actuators with model-based force control comprising individual gas models as well as the rubber nonlinearities for each leg. The control law also includes the gas flow in the proportional directional control valve in 3/3-way function. The present paper describes the basic architecture of the platform, the dynamic models, as well as testbed results for the existing fluidic-muscle parallel platform DynaHex. It is shown that the presented control scheme leads to a stable force control of the platform for quasi-static motion. As an application, the device will be employed in fields of biomechanics, as well as in general environments requiring physical simulation.     

The Mechanical Response of Shape Memory Alloys Under a Rapid Heating Pulse

Shape memory alloy (SMA) actuators are very promising due to their large strain and work-output, but are considered to be very slow due to their cooling rate. In this article, we explore the capabilities of a fast one-directional actuation mode based on one-occasional rapid Joule heating of SMA elements. For this purpose, a unique experimental system has been developed that applies a high-voltage electric pulse to a detwined NiTi wire and measures the resulting displacement due to the martensite to austenite phase transformation. The electric pulse is tuned to produce variable temperature jump of up to 160°C within a risetime of few microseconds. One end of the wire is clamped while the displacement of the other end is monitored both by a laser doppler vibrometer and by an optical encoder that measures the displacement of a grating device. Analysis of experimental results reveals a dead time delay between the electric pulse and the wire’s response, which is attributed to the austenite nucleation time and which determines the limit on the fastest possible shape memory actuation. Further analysis reveals relations between the dead weight used and the average acceleration and maximal velocity obtained. In particular, the maximal velocity correlates to a constant kinetic energy delivered by the wire, which suggests a constant integrand over the stress-strain curve regardless of the dead-weight used. A comparison of actuation performances demonstrates that our actuation experiments are significantly advantageous over other fast actuation methods in almost every actuation aspect reviewed. This demonstrates the great potential of SMA for applications that require high speeds and large displacements one-occasional actuation.     

基于ED-LSTM的智能汽车神经网络横向动力学建模与控制

车辆动力学建模过程中通常会进行简化和假设, 导致模型在某些工况下无法准确反映车辆的实际动态特性, 影响控制精度甚至安全性. 鉴于此, 该文提出了一种基于数据驱动的非线性建模与控制方法, 建立了新型神经网络车辆横向动力学多步预测模型, 实现了智能汽车对参考轨迹的跟踪控制. 首先, 在分析车辆单轨模型并考虑轮胎非线性和纵向负载转移的基础上, 基于编码器?解码器结构设计神经网络横向动力学模型. 其中, 使用串行排列来扩展微分方程描述不完全的动力学信息, 隐藏层神经元学习车辆的高度非线性和强耦合特性, 进而提高模型全局计算精度. 利用所构建的数据集进行模型训练和测试, 结果表明, 相比于物理模型, 所提出的模型在不同路面附着系数条件下均具有更高的建模精度, 具有隐式预测路面摩擦条件能力. 其次, 利用提出的模型设计轨迹跟踪控制算法, 根据车辆稳态转向假设, 计算所需的前轮转向角和稳态质心侧偏角, 将稳态质心侧偏角纳入基于路径误差的转向反馈中, 实现参考轨迹跟踪控制. 最后, 使用CarSim/Simulink联合仿真及HIL实验测试进行不同工况试验的对比分析, 对所提出的基于神经网络模型的控制算法进行评价, 结果表明, 该模型能够实现智能汽车在高速下精确的跟踪控制效果, 并具有良好的横向稳定性.      

Control of flight forces and moments by flapping wings of model bumblebee

The control of flight forces and moments by flapping wings of a model bumblebee is studied using the method of computational fluid dynamics.Hovering flight is taken as the reference flight:Wing kinematic parameters are varied with respect to their values at hovering flight.Moments about(and forces along)x,y,z axes that pass the center of mass are computed.Changing stroke amplitude(or wingbeat frequency)mainly produces a vertical force.Changing mean stroke angle mainly produces a pitch moment.Changing wing angle of attack,when down-and upstrokes have equal change,mainly produces a vertical force,while when down-and upstrokes have opposite changes,mainly produces a horizontal force and a pitch moment.Changing wing rotation timing,when dorsal and ventral rotations have the same timing,mainly produces a vertical force,while when dorsal and ventral rotations have opposite timings,mainly produces a pitch moment and a horizontal force.Changing rotation duration has very small effect on forces and moments.Anti-symmetrically changing stroke amplitude(or wingbeat frequency)of the contralateral wings mainly produces a roll moment.Anti-symmetrically changing angles of attack of the contralateral wings,when down-and upstrokes have equal change,mainly produces a roll moment,while when down-and upstrokes have opposite changes,mainly produces a yaw moment.Anti-symmetrically changing wing rotation timing of the contralateral wings,when dorsal and ventral rotations have the same timing,mainly produces a roll moment and a side force,while when dorsal and ventral rotations have opposite timings,mainly produces a yaw moment.Vertical force and moments about the three axes can be separately controlled by separate kinematic variables.A very fast rotation can be achieved with moderate changes in wing kinematics.