Stabilization system on an office-based ear surgical device by force and vision feedback

An “office-based surgical device” is a kind of device which aims to shift the conventional surgical procedures from the operating room to the confines of the doctor’s/surgeon’s office as well as to assist the surgeons to carry out the surgeries on the patients automatically or semi-automatically. In this paper, an office-based surgical device suitable for patients with Otitis Media with Effusion (OME) is introduced. Due to the office-based design, it is not possible to subject the patient to general anesthesia, i.e., the patient is awake during the surgical treatment with the device. To ensure a high success rate and safety, it is very important that the relative motion and the contact force between the tool set of the device and the tympanic membrane (TM) can be stabilized. To this end, a control scheme using force and vision feedback is proposed. The force feedback controller is a PID-based (proportional-integral-derivative) controller, which is designed for force tracking. The vision feedback controller is a vision-based motion compensator, which is designed to measure and compensate the head motion since it is equivalent to TM motion. Furthermore, the control scheme is implemented and tested in a mock-up system. The experimental results show that the proposed composite controller can achieve much better performance in force tracking than a pure force feedback controller. The performance can at least improve by 20% after augmenting the motion compensator, which helps the system to stabilize the relative motion indirectly and maintain the contact force precisely.     

自适应光学中变形镜的研究

大气对激光束的湍流效应是制约激光通信技术发展的一个主要因素,研究发现自适应光学技术可以有效的缓解激光束在大气中传输受到的影响。自适应光学系统由探测器、控制器和校正器3部分组成。首先由探测单元和控制单元确定控制信号,然后通过控制器改变变形镜的镜面,以达到校正波前的目的。变形镜是自适应光学系统中实现波前校正的关键器件．其特性将直接影响系统对波前光束的改善结果。通过对变形镜的工作原理、分类、技术要求和性能指标的研究．该系统补偿效果达到90％。     

Real-time carbon content control for PECVD ZrO/sub 2/ thin-film growth

We present a methodology for real-time control of thin-film carbon content in a plasma-enhanced metal-organic chemical vapor deposition process using combination of online gas phase measurements obtained through optical emission spectroscopy and off-line (ex situ) measurements of film composition obtained via X-ray photoelectron spectroscopy (XPS). Initially, an estimation model of carbon content of ZrO/sub 2/ thin films based on real-time optical emission spectroscopy data is presented. Then, a feedback control scheme, which employs the proposed estimation model and a proportional-integral controller, is developed to achieve carbon content control. Using this approach, a real-time control system is developed and implemented on an experimental electron cyclotron resonance high-density plasma-enhanced chemical vapor deposition system to demonstrate the effectiveness of real-time feedback control of carbon content. Experimental results of depositions and XPS analysis of deposited thin films under both open-loop and closed-loop operations are shown and compared. The advantages of operating the process under real-time feedback control in terms of robust operation and lower carbon content are demonstrated.     

保护箱中激光沉积的粉末流、熔池观测与分析

通过CCD摄像机对保护箱中的同轴送Nb,Ti,Al混合金属粉的喷嘴出口的粉末汇聚情况和沉积过程的熔池形貌进行了实时观察与分析。根据微粒光散射理论对CCD拍摄的粉末流图像进行分析,得出了不同位置处粉末流的分布模型,并结合实验获取了用于激光沉积的同轴送粉喷嘴到沉积表面的适用距离区间。通过图像处理程序对熔池形貌进行提取,分析了工艺参量对熔池形貌的影响;对多层沉积过程中沉积层的熔池形貌特征、熔池波动现象等进行了较详细的分析探讨。通过系统的观测与分析,深入理解粉末流的汇聚与熔池的实时变动行为,有利于更好地控制激光沉积过程。     

Run by run process control: combining SPC and feedback control

The run by run controller provides a framework for controlling a process which is subject to disturbances such as shifts and drifts as a normal part of its operation. The run by run controller combines the advantages of both statistical process control (SPC) and feedback control. It has three components: rapid mode, gradual mode, and generalized SPC. Rapid mode adapts to sudden shifts in the process such as those caused by maintenance operations. Gradual mode adapts to gradual drifts in the process such as those caused by build-up of deposition inside a reactor. The choice between the two modes is determined by the outcome from generalized SPC which allows SPC to be applied to a process while it is being tuned. The run by run controller has been applied to the control of a silicon epitaxy process in a barrel reactor. Rapid mode recovered the process within 3 runs after a disturbance. Gradual mode reduced the variation of the process by a factor of 2.7 as compared to historical data     

Robust motion controller design for high-accuracy positioningsystems

This paper presents a controller structure for robust high speed and accuracy motion control systems. The overall control system consists of four elements: a friction compensator; a disturbance observer for the velocity loop; a position loop feedback controller; and a feedforward controller acting on the desired output. A parameter estimation technique coupled with friction compensation is used as the first step in the design process. The friction compensator is based on the experimental friction model and it compensates for unmodeled nonlinear friction. Stability of the closed-loop is provided by the feedback controller. The robust feedback controller based on the disturbance observer compensates for external disturbances and plant uncertainties. Precise tracking is achieved by the zero phase error tracking controller. Experimental results are presented to demonstrate performance improvement obtained by each element in the proposed robust control structure     

低空高分辨率激光雷达光学系统设计

针对“低慢小”目标光学成像识别能力差、复杂背景下信噪比低等问题，设计了一款低空高空间分辨率激光雷达光学系统。发射光学系统扫描器件采用MEMS反射镜，设计了专用扩束光学系统保证不同扫描角度发射激光的光束质量；接收光学系统采用物镜、数字微反射镜器件结合偏振器件，可同时实现激光回波接收与可见光成像，相较于采用单点探测器接收的激光接收系统，具有背景噪声低的优势。给出了光学系统的性能参数，利用光学设计软件设计了光学系统，该系统空间分辨率为0.5 mrad/pixel，扫描点阵列规模为200×200。模拟结果表明设计方法可行，计算其在大气中的探测距离可达到1000 m，背景噪声相较于单点探测器接收系统可降低约22162倍。     

自由空间光通信中光电子器件的现状分析

对自由空间光通信中的光电子器件包括激光器、光电探测器、光学滤波器的现状做了系统分析,结果表明:CO2激光器、半导体激光器和LD泵浦的YAG固体激光器成为目前和未来自由空间光通信系统的重要光源;PIN和APD光电二极管成为自由空间光通信系统探测器的最佳选择;干涉滤波器和原子滤波器成为自由空间光通信系统滤光器的发展重点。     

分布反馈激光器温度与电流控制研究

为了精密控制分布反馈激光器的温度与电流, 采用数字信号处理芯片, 设计了分布反馈激光器驱动装置。通过该装置设定激光器温度和电流的参考电压, 经数模转换, 再通过温度和电流驱动模块, 馈入并驱动分布反馈激光器, 进行了实验验证。结果表明, 40min内温度变化极差与标准差分别不超过5mK和0.7mK, 电流变化极差与标准差不超过40μA和6μA; 驱动半导体光放大器, 关断时间小于1μs, 具有良好的瞬间响应特性; 该装置具有较高的温度和电流稳定性, 流控模块具有良好的瞬态特性, 能够精密控制分布反馈激光器的温度和电流。该控制装置可用于光腔衰荡光谱研究, 控制分布反馈激光器并驱动光放大器来关断激光。     

Fast Steering Mirror Control Using Embedded Self-Learning Fuzzy Controller for Free Space Optical Communication

Coarse and Fine tracking in free space laser communication is very crucial. This paper presents architecture for laser beam acquisition, tracking and pointing mechanism. The centroid of the received image beam is calculated and then error is computed using reference position. Embedded self-learning fuzzy controller (SLFC) is used to drive the fast steering mirror mechanism to point the laser beam on receiver detector. The SLFC is embedded in hardware using Arduino development board. The performance of the SLFC is compared with the standard PID control. It is shown that the proposed architecture successfully track the laser beam and the SLFC shows the robustness against model uncertainties and reject disturbances.     

中心开孔型四象限探测器光纤定位闭环控制方法

光纤定位技术是多目标光纤光谱望远镜中的关键技术,光纤定位精度是影响望远镜观测效率的重要因素,随着光谱巡天项目的开展,光纤定位单元的小型化、高密度化、集成化和高精度定位要求成为普遍趋势,这对光纤定位系统提出了更高技术要求和挑战。光纤定位技术也期望实现高精度的实时监测和反馈系统,形成有效的闭环控制。基于此提出了一种中心开孔型四象限探测器光纤定位技术,并利用二维高斯模型对中心开孔型四象限探测器定位算法进行了设计,该算法对单元光斑束腰单次标定,可实现高精度的多次实时光斑位置确定和光纤位置调整。利用光纤光谱仪望远镜原理搭建了模拟实验对此装置和算法的性能进行了模拟,应用此闭环控制方法,在四象限探测器零点偏置直径为4 mm、光纤截面积达到1 000 μm2情况下,绝对定位误差可以控制在6 μm之内,相对误差可控制在0.15%范围内,可以有效提高望远镜星象和光纤的耦合效率。     

波形控制功率负反馈YAG激光焊接机的设计

为了提高激光焊接机激光输出的能量稳定度,采用了在输出端加激光功率检测装置并将其实时信号反馈到控制端,形成一个闭环控制系统的控制方法,进一步提出了在激光功率负反馈信号中加入相位补偿信号以达到提高激光能量控制精度的目的.同时,在激光焊接机软件设计上加入了激光能量波形控制功能,以拓宽激光焊接加工的应用领域.与传统的激光电流负反馈的能量波动为8%以上相比,采用功率负反馈可使激光能量波动控制在3%以内.实验结果表明,选择激光功率波形,可以改善焊接质量.     

Model Predictive Control of Si1−xGex Thin Film Chemical–Vapor Deposition

This paper integrates in situ robust and efficient fundamental models and noninvasive optical sensors with state-of-the-art estimation and model predictive control techniques in order to grow unusual and aggressive Si_1-xGe_x alloy films. A model predictive controller is presented that utilizes a dynamic process model and feedback from a spectral ellipsometer to reconstruct the current state of a Si_1-xGe_x growing film in real time. Si _1-xGe_x films grown utilizing feedback from a spectral ellipsometer are compared to films grown using open-loop recipes, which is the current industrial practice. These films are compared quantitatively utilizing the offline characterization techniques, auger spectrometry, and secondary-ion-mass-spectrometry analysis. The model predictive controller presented in this paper detects and rejects unmeasured disturbances allowing for precise control over film qualities. In this paper, films grown utilizing feedback from an optical sensor are shown to be up to 51% truer to desired profiles, when compared with similar films grown using open-loop recipes. The experimental results presented in this paper provide the first demonstration of feedback control using online optical film measurements to grow aggressive alloy composition profiles in which flow rates of several component gases and reactor temperatures must be varied simultaneously in order to achieve the profile of interest     

Resistance based iterative learning control of additive manufacturing with wire

This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of former control solutions of the process, providing more robust and industrially acceptable measurement techniques. The system uses a solid state laser that melts metal wire, which in turn is deposited and solidified to build the desired solid feature on a substrate. The process is inherently subjected to disturbances that might hinder consecutive layers to be deposited appropriately. The control action is a modified wire feed rate depending on the surface of the deposited former layer, in this case measured as a resistance. The resistance of the wire stick-out and the weld pool has shown to give an accurate measure of the process stability, and a solution is proposed on how to measure it. By controlling the wire feed rate based on the resistance measure, the next layer surface can be made more even. A second order iterative learning control algorithm is used for determining the wire feed rate, and the solution is implemented and validated in an industrial setting for building a single bead wall in titanium alloy. A comparison is made between a controlled and an uncontrolled situation when a relevant disturbance is introduced throughout all layers. The controller proves to successfully mitigate these disturbances and maintain stable deposition while the uncontrolled deposition fails.     

利用快速相位反馈控制输出变换极限飞秒激光脉冲

报道了利用简化的频率分辨光学开关法快速测量飞秒激光脉冲,并形成反馈,控制液晶空间光调制器,补偿非线性光纤飞秒激光放大器输出脉冲的啁啾,获得了脉冲宽度74 fs的变换极限脉冲。     

高功率激光实时检测与控制系统的研究

为了提高激光功率的稳定性和控制精度,设计了一种新颖的高功率激光实时检测与控制装置。该系统由光功率采样单元和反馈控制单元两部分组成。采样单元利用尾镜的微量透射光进行激光采样,经衰减后再由探测器进行接收并对其加以处理;然后将处理信号送到反馈控制单元去自动调节放电电流,以保证输出激光功率的稳定。实验表明,该系统能够实时监控激光的输出功率,有效提高激光功率的控制精度和稳定性。在4kW轴快流CO2激光器上的实际运行结果表明,该系统可使得激光功率稳定度达到±0.1%水平。     

Inverse model-based real-time control for temperature uniformity ofRTCVD

A reduced-order model describing a rapid thermal chemical vapor deposition (RTCVD) process is utilized for real-time model based control for temperature uniformity across the wafer. Feedback is based on temperature measurements at selected points on the wafer surface. The feedback controller is designed using the internal model control (IMC) structure, especially modified to handle systems described by ordinary differential and algebraic equations. The IMC controller is obtained using optimal control theory on singular arcs extended for multi-input systems. Its performance is also compared with one based on the Hirschorn inverse of the model. The proposed scheme is tested with extensive simulations where the full-order model is used to emulate the process. Several cases of significant uncertainty, including model parameter errors, process disturbances, actuator errors, and measurement noise are used to test the robustness of the controller to real life situations. Both controllers succeed in achieving temperature uniformity well within the desirable bounds, even in cases where several sources of uncertainty are simultaneously present with measurement noise     

Characteristics of mode-hopping noise and its suppression with the help of electric negative feedback in semiconductor lasers

Some detailed properties of mode-hopping noise in semiconductor injection lasers are reported, and the validity of electric negative feedback as a method of suppressing the noise is demonstrated. Mode-hopping noise was found to be an intrinsic property of the laser, independent of optical feedback (reinjection of the output light) reflected at the surface of an external device. The optical feedback works to shift the operating point of the laser from a stable condition having single-mode operation to an unstable condition revealing the modehopping phenomena. Characteristics of the mode-hopping noise support well the theoretical analysis in which the source of the noise is assumed to be fluctuations of the emission and the electron wave accompanied by spontaneous emission and in which the noise is amplified through mechanism of the mode competition phenomena. Mode-hopping noise was suppressed with the help of the electric negative feedback from the optical detector to the injection current source more effectively than by another reducing method of superposition of the high-frequency current. The suppressed noise level was lower than that at stable single-mode operation.     

激光金属沉积成形基板预热的研究

为了降低激光金属沉积成形过程中试样和基板间的温度梯度,减小和抑制成形过程的热应力,提高试样的成形质量,提出并设计了一种用于激光金属沉积成形的基板预热系统。该系统由基板预热器、智能比例微分积分控制器以及计算机串口温度采集反馈控制等3部分组成。利用自行研制的激光金属沉积成形设备和基板预热系统进行了成形实验。实验结果表明,基板预热可以改善试样的成形质量,降低成形过程的热应力。     

New hybrid controller for systems with deterministic uncertainties

In this paper, a new hybrid controller for systems with deterministic uncertainties is developed. The proposed controller identifies and compensates deterministic uncertainties simultaneously. It is the combination of a time-domain feedback controller and a frequency-domain iterative learning controller. The feedback controller decreases system variability and reduces the effect of random disturbances. The iterative learning controller shapes the system input to suppress the error caused by deterministic uncertainties such as friction and backlash. The control scheme use only local input and output information, no system model is required. The uncertainties can be structured or unstructured. The effectiveness of the proposed controller is experimentally verified on a servo system with gearbox