Generation of control signals for adaptive systems using laser atmospheric backscatter

A method for controlling an adaptive optical system by using the intensity of laser atmospheric backscatter is studied. Mathematical modeling is used to study the generation of a control signal in a monostatic loop and, as a consequence, the range of beam focus with the closed loop. It is shown that this method of generation does not lead to beam collimation even for beams of diffraction quality.     

Time-dependent FEM simulation of dilution control of laser cladding by adaptive mesh method

Dilution is an important factor which influences the properties of clad layer. In this paper the change of dilution during laser cladding and the control of dilution are simulated by a finite element method. The adaptive mesh method is adopted for the time-dependent finite element method computation so that the shape of melt pool can be well represented. The situation of the width control of melt pool is also simulated, which indicates that the dilution can be controlled if the width of melt pool is controlled. Computational results indicate that if a line energy (input energy per unit distance) remains constant the dilution will increase with time, especially at the beginning. Simulation results show that it is possible to control dilution in a certain range if the line energy decreases with time. Experiment of Nd: YAG laser cladding with wire feeding is performed. Experiment results coincide well with the FEM results.     

多轴激光加工机器人光路几何误差建模方法研究

本文提出了一种激光光路几何精度建模的方法,用于多轴激光加工机器人光路几何误差的建模。在每个反射镜上定义一个与其固连的笛卡尔坐标系,用齐次列阵表示激光光路特征点(光源、入射点和激光光线末端点)和光线矢量在坐标系中的位置坐标和姿态方位,将激光光束在理想条件下和实际条件下的传输过程用4×4阶齐次方阵运算来实现,在此基础上提出光线几何误差反射传递函数,清楚地反映了各误差源对末端误差的影响情况,从而完整的描述了光束在传输过程中的实际误差。本文以五轴数控激光加工机器人为例,建立其光路传输路径和几何误差模型,试验结果表明了该方法的有效性。     

Wavefront sensors for adaptive optical systems

Possibilities of constructing a wavefront sensor for the adaptive system in the Big Solar Vacuum Telescope are considered. A modified correlation tracker (MCT) is proposed. The sensor is tested by measuring the displacement of the image of the solar granulation pattern in the first and second foci of the telescope under clear vision conditions. The change in the quality of the image being transferred to the second focus and the measured displacement of the image of solar granulation in the second focus with extremely good vision conditions and a certain granulation structure are analyzed. The effect of reduction of the input aperture to 170 mmon the image quality and, hence, on MCT operation is analyzed.     

适合于大气激光通信的双空间调制

相对于传统的光空间调制,光广义空间调制在传输速率和频谱效率上虽然有了较大的提升,但其误码性能不够理想。本文利用脉冲位置调制(PPM)和脉冲幅度调制(PAM),通过每次同时激活两个激光器而提出了一种双空间调制(DSM)。采用联合界技术推导出了DSM的误码率理论上界,分析了其频谱效率、传输速率和复杂度的影响因素,并与已有光空间调制的性能进行了对比。仿真结果表明:DSM不仅提升了系统的频谱效率和传输速率,而且有效地改善了系统的误码性能。在相同的传输速率下,当误码率为1×10-3时,相对于(4,4)-8PPM SPPM和(3,4)-4PPM GSPPM方案,(3,4)-8PPM-2PAM DSM的信噪比分别改善了约2.5 dB和6 dB,频谱效率分别提高了2.335 bits/(s·Hz)和0.375 bits/(s·Hz)。DSM方案为未来大气激光通信传输速率的提高提供了一种有效手段。     

用于多波段激光大气透过率测量的太阳辐射计

为了实时测量多个波段激光大气透过率,研制了ISP02型近红外太阳辐射计。详细阐述了该仪器的硬件组成、光学系统设计以及工作流程,并对仪器进行了定标,给出仪器能达到的性能指标。依据建立的基于太阳宽谱直接辐射测量获取激光波段大气透过率的方法,实测得到1.064,1.315,1.54μm大气透过率,将结果与POM02型太阳辐射计采用外推法获取的激光大气透过率进行对比,误差均小于6%,测量的水汽总量与POM02对比,误差均小于7%;然后,将两者外推的3.78μm透过率进行对比,误差均小于5%。秋冬季实测的1.315μm透过率与激光大气传输评估软件对比,误差小于2%。该仪器测量结果可靠、性能稳定,可为同时获取多个波段激光大气透过率提供有效测量手段。     

Computer simulation of wear

A digital record of the profile of a machined surface is processed by a computer to yield a number of wear-sensitive parameters such as mean slope and peak curvature. Numerical techniques are used to simulate removal of successive layers of the surface. Wear sensitive parameters are recomputed at each such removal. The results agree with experimental values obtained by a computer analysis of records, obtained by relocation profilometry, of a real wear experiment performed on the same surface. It is found that the variation with depth of wear of several surface parameters can be represented by the normal probability integral.     

A device for atmospheric laser deposition of noble metal nanostructures

An experimental device has been developed for atmospheric laser deposition of nanostructures of noble metals (Ag, Au, Pt, and Pd) on the surfaces of functional materials. This device is composed of functional units with a simple engineering design. A number of experimental samples have been obtained on the device in different laser-deposition modes; these were investigated using the scanning electron microscopy and atomic-force microscopy methods.     

Biomimetic control for adaptive camera stabilization in driver-assistance systems

Throughout the last decade, a large number of electronic driver-assistance systems have been developed in order to improve vehicles’ comfort and safety. Up to now, they more or less all rely on odometric data. However in the future, a new form of information is likely to be used: visual sensors, e.g. cameras, can provide additional knowledge on traffic and the vicinity. This paper presents an inertially stabilized camera platform for high precision tracking of points of interest, that has been developed within the project FORBIAS (Research cooperation for biomimetic assistance systems). The inertial stabilization is based on a specially designed sensor system that uses MEMS components in connection with a biologically inspired control algorithm for adaptive enhancement and online calibration of the gaze stabilization system.     

Modelling the application of adaptive optics to wide-field microscope live imaging

Wide‐field fluorescence microscopy is an essential tool in modern cell biology. Unfortunately the image quality of fluorescence microscopes is often significantly degraded due to aberrations that occur under normal imaging conditions. In this article, we examine the use of adaptive optics technology to dynamically correct these problems to achieve close to ideal diffraction limited performance. Simultaneously, this technology also allows ultra‐rapid focusing without having to move either the stage or the objective lens. We perform optical simulations to demonstrate the degree of correction that can be achieved.     

一种自适应激光电源的设计

本文介绍了一种自适应激光电源的设计。该电源基于电压源加大功率场效应管结构,采用小注入电流下检测负载电压的方法调整电压源电压,可最大限度提高电源效率,并降低系统散热量。该电源输出电压可在大范围内自适应,可通用于半导体单管激光器及其阵列。     

Novel adaptive laser scanning sensor for reverse engineering measurement

In this paper, a series of new techniques are used to optimize typical laser scanning sensor. The integrated prototype is compared with traditional approach to demonstrate the much improved performance. In the research and development, camera calibration is achieved by extracting characteristic points of the laser plane, so that the calibration efficiency is improved significantly. With feedback control of its intensity, the laser is automatically adjusted for different material. A modified algorithm is presented to improve the accuracy of laser stripe extraction. The fusion of data extracted from left and right camera is completed with re-sampling technique. The scanner is integrated with a robot arm and some other machinery for on-line measurement and inspection, which provides a flexible measurement tool for reverse engineering.     

Ground-based prototype quantum cascade laser heterodyne radiometer for atmospheric studies

The advent of quantum cascade lasers has provided matured continuously tunable solid state laser sources emitting from mid-infrared to terahertz wavelengths. Such sources, used as local oscillators, offer the practical prospect of aircraft, high altitude platform, and satellite deployment of compact and shot noise limited heterodyne radiometers for Earth observation and astronomy. A ground-based prototype of a quantum cascade laser heterodyne radiometer operating in the mid-infrared has been developed and is presented. The instrument design and concepts are described, together with evaluation of the instrument in the laboratory and during field measurements of atmospheric ozone. In this study the best performance achieved by the prototype quantum cascade laser heterodyne radiometer was a signal-to-noise ratio of three times the theoretical shot-noise limit. The prototype has allowed the main sources of excess noise to be identified as residual optical feedback in the local oscillator optical path and a lack of mechanical and thermal stability in the local oscillator collimation system. Instrument improvements are currently being implemented and enhanced performance is expected in the near future.     

大型曲面自适应研抛机器人运动学仿真

为了提高加工效率,提出了一种安装盘状工具在大型曲面上进行自适应研抛加工的机器人,可以在行进中进行作业.在分析了大型曲面的特征,针对盘状工具多点切触加工的特点,确定了机器人的技术构成.通过Pro/Engineer软件建立了研抛机器人的虚拟模型,研究了自适应研抛机器人和加工系统的运动学并建立了数学模型,应用Adams和Matlab软件对研抛机器人的自适应性和整机运动性能进行了联合仿真.仿真结果表明研抛机器人及其工具系统具有良好的动态性能,为研抛机器人系统的设计、制造和控制提供参考依据.     

汽车道路模拟系统的模糊自适应控制及仿真

以汽车道路模拟系统为研究对象,根据模糊控制理论,将模糊控制与常规的增量式PID控制相结合,设计出一套模糊自适应控制系统.并对C级路面谱进行仿真再现,仿真结果表明,该控制器比常规PID控制器具有更高的控制精度和更好的动态性能,在道路模拟仿真试验中可以达到非常满意的效果.     

大气电场仪标定系统的设计与仿真

文章介绍了大气电场仪的标定原理及意义,采用 ANSYS软件对大气电场仪标定系统进行仿真分析,依次分析了板间距离、探头位置和电场边缘效应对静电场环境的影响,为标定系统的设计提供了可靠的依据.     

Multilevel simulation for advanced manufacturing systems

This paper focuses on the techniques used to generate a multilevel simulation system that can optimise the design, layout, control and performance of a flexible manufacturing system (FMS). It discusses the software structures used to design and implement the simulator, which operates in the following modes: Off-line system-layout optimisation Off-line part-schedule evaluation Off-line control-algorithm evaluation/optimisation On-line state extrapolation and “what if?” testing All of these modes of operation are essential to the efficient running of a complex FMS. The techniques described have been applied and tested on an FMS at the Key Centre for Computer Integrated Manufacture at Swinburne Institute of Technology in Melbourne, Australia.     

Discrete adaptive controllers for systems with parametric disturbances

This paper presents synthesis procedures of discrete single-channel control systems with specified performance parameters of transient processes for an uncertain plant model. An integral law of adjusting the controller parameters with respect to the mismatch between the current and desired values of the output variable on the highest step is considered. Results of an analysis of a closed-loop system performed using a discrete analog of the Lyapunov second method are given.     

Computer simulation of rough-surface microtopography

The principle of building a computer model of rough-surface microtopography is proposed. A 3D computer model of rough surface is developed and tested. The compliance of reference profile graphs of real surfaces processed using different technologies and 3D models generated by their parameters is estimated.