Automatic Microassembly Using Visual Servo Control

We propose an automatic microassembly method that can be used to construct three-dimensional microelectromechanical system (MEMS) structures. A six degree-of-freedom micromanipulator, equipped with a passive microgripper, is employed to grasp, manipulate, and join the micropart using visual feedback from an optical microscope. The proposed process utilizes a two-stage alignment strategy to perform the micro-grasping and micro-joining tasks. Using a vision-based localization method, the Cartesian coordinates of the manipulated micropart in three-dimensional space are determined. Further, a vision-based contact sensor determines the contact state between two micro-components in three dimensions to facilitating the micro-joining tasks. Visual servo control is used for accurate position feedback in three Cartesian coordinates during microassembly tasks. The necessary steps towards construction of complex three-dimensional MEMS devices, i.e., grasping a micropart, manipulating it, joining it to another micropart, and finally releasing it from the microgripper, have been successfully carried out using a six degree-of-freedom micromanipulator. Experiments demonstrate both the efficiency and validity of the proposed automatic assembly approach.     

Development, Modeling, and Control of a Micro-/Nanopositioning 2-DOF Stick–Slip Device

The studies presented in this paper are motivated by the high performances required in micromanipulation/microassembly tasks. For that, this paper presents the development, the modeling, and the control of a 2-DOF (in linear and angular motion) micropositioning device. Based on the stick–slip motion principle, the device is characterized by unlimited strokes and submicrometric resolutions. First, experiments were carried out to characterize the performances of the micropositioning device in resolution and speed. After that, a state-space model was developed for the substep functioning. Such functioning is interesting for a highly accurate task like nanopositioning. The model is validated experimentally. Finally, a controller was designed and applied to the micropositioning device. The results show good robustness margins and a response time of the closed-loop system.      

A magnetically levitated, automated, contact analytical probe tool

With the challenge of the shrinking dimensions in the fabrication process, demands are growing for higher precision and more powerful analytical probing stations to be used for characterization and failure analysis of integrated circuits. A magnetic levitation-based approach to analytical probing stations is proposed and investigated in this paper. This approach permits the process to be automated while maintaining better resolution and easier operation than is currently available. Further, force control can be implemented to ensure that the probe contact does not scratch the device under testing. Feedback controllers are designed and used in both the suspension and the XY positioning. The suspension motion controller is implemented in analog circuitry while the XY motion controller is implemented in a digital controller. An air gap sensor and optical position sensors are used for the position feedback. A simple open loop control method is derived for the force control. A positioning repeatability of 0.2 μm and a force repeatability of 80 mgf are observed from the experimental results     

Development and Assessment of a Novel Decoupled XY Parallel Micropositioning Platform

This paper presents the development and performance assessment procedures for a new XY parallel micropositioning platform (PMP) aiming at a submicrometer accuracy for microscale manipulation. The uniqueness of the proposed microparallel platform lies in that it possesses an uncomplicated structure as well as actuation isolation and output motion decoupling properties, which facilitates the adoption of two single-input–single-output controllers. Based on the matrix method, the kinetostatics models of the PMP are established and verified by finite-element analysis. Via system identification, a digital lag--lead compensator is designed to compensate for the hysteresis of each piezoelectric actuator. A feedforward control is then implemented to construct a zero phase error tracking controller. Positioning performance of the PMP in terms of resolution, accuracy, repeatability, and contouring performances of 1-D and 2-D motions has been evaluated by several experimental studies. Experimental results not only validate the effectiveness of the designed controller but also show that both positioning and contouring of the PMP can achieve a submicrometer precision within a specified velocity range.      

Energy-efficient collaborative target tracking algorithm using cost-reference particle filtering in wireless acoustic sensor networks

Target tracking is one of the most important applications of wireless sensor networks. Optimized computation and energy dissipation are critical requirements to save the limited resource of sensor nodes. A new robust and energy-efficient collaborative target tracking framework is proposed in this article. After a target is detected, only one active cluster is responsible for the tracking task at each time step. The tracking algorithm is distributed by passing the sensing and computation operations from one cluster to another. An event-driven cluster reforming scheme is also proposed for balancing energy consumption among nodes. Observations from three cluster members are chosen and a new class of particle filter termed cost-reference particle filter (CRPF) is introduced to estimate the target motion at the cluster head. This CRPF method is quite robust for wireless sensor network tracking applications because it drops the strong assumptions of knowing the probability distributions of the system process and observation noises. In simulation experiments, the performance of the proposed collaborative target tracking algorithm is evaluated by the metrics of tracking precision and network energy consumption.     

Integrated micro- and miniscale electromechanical systems with permanent-magnet servo-motors and VLSI drivers–controllers

The current trends in development and deployment of advanced micro- and miniscale electromechanical systems (MEMS) have facilitated the unified fundamental, applied, and experimental research activities in the analysis and design of state-of-the-art motion devices (rotational and translational electromechanical motion devices), integrated circuits (ICs), and controllers. The objectives of this paper are to design, develop, and compare different control algorithms for high-performance MEMS with permanent-magnet rotational servo-motors controlled by ICs (VLSI driver–controller is fabricated using CMOS technology). The problems to be solved are very challenging because a number of long-standing issues in design, hardware integration, control, nonlinear analysis, and robustness have to be solved. The major emphases of this paper are the analysis and design of robust servo-systems, as well as the comparison of the dynamic performance of closed-loop MEMS with different control algorithms. We synthesize, verify, and test proportional–integral, integral with state feedback extension, relay, and sliding mode controllers. It is illustrated that the sliding mode control laws drive the states and tracking error to the switching surface and maintain (keep) the states and tracking error within this nonlinear switching surface in spite of different references, disturbances, parameter variations, and uncertainties. That is, robust tracking, desired accuracy, and disturbance attenuation are achieved. We report the experimental setup which was built to perform the advanced studies of high-performance MEMS. The testbed was built to integrate permanent-magnet microscale servo-motor and ICs (driver–controller).     

FPGA-based architecture for direct visual control robotic systems

This paper describes a whole new framework to quickly develop dynamic visual servoing systems embedded in an FPGA. Parallel design of algorithms increases the precision of this kind of controller, while minimizing the response time. Additionally, a control framework to dynamically visual control robot arms is proposed. The direct image-based visual controllers derived from the framework allow for tracking trajectories obtaining different dynamic behaviors depending on a weighting matrix. A new method to compensate the chaos behavior of this kind of system is also included in the proposed framework. To exemplify the feasibility of the FPGA-based proposed framework, and to demonstrate the effects of the metrics, some of the derived controllers are evaluated during the tracking of image trajectories.     

53cm双筒激光测距望远镜控制系统的设计与实现

研制53 cm双筒激光测距望远镜的快速平稳伺服控制系统,以实现快速空间目标的跟踪测量。模块化设计并构建望远镜的控制系统,伺服驱动器完成电流和速度的闭环,运动控制器实现位置环和复合PID算法。对控制机箱进行集成,并对控制器进行嵌入式开发,由控制器负责实时的运动控制,而上位机软件进行任务管理和人机交互。自定义通信协议以克服通信延时和VC++定时精度不高的问题,并提出位置二次闭环与混合PID的控制策略以提高望远镜的跟踪精度。实验结果表明:该望远镜在以3(°)/s的匀速运动和低轨卫星跟踪过程中,精度在5″内;在低速运动和中高轨卫星的跟踪中,能够达到角秒量级的精度,经测试该望远镜能快速平稳地跟踪400 km以上空间目标,并满足指标要求。     

Closed-loop optimal control-enabled piezoelectric microforce sensors

This paper presents a closed-loop optimally controlled force-sensing technology with applications in both micromanipulation and microassembly. The microforce-sensing technology in this paper is based on a cantilevered composite beam structure with embedded piezoelectric polyvinylidene fluoride (PVDF) actuating and sensing layers. In this type of sensor, the application of an external load causes deformation within the PVDF sensing layer. This generates a signal that is fed through a linear quadratic regulator (LQR) optimal servoed controller to the PVDF actuating layer. This in turn generates a balancing force to counteract the externally applied load. As a result, a closed feedback loop is formed, which causes the tip of this highly sensitive sensor to remain in its equilibrium position, even in the presence of dynamically applied external loads. The sensor's stiffness is virtually improved as a result of the equilibrium position whenever the control loop is active, thereby enabling accurate motion control of the sensor tip for fine micromanipulation and microassembly. Furthermore, the applied force can be determined in real time through measurement of the balance force.     

The dynamic response analysis of a pyroelectric thin-film infraredsensor with thermal isolation improvement structure

Both theoretical and experimental studies of the substrate effect on the thermal behavior of a PbTiO₃ infrared (IR) sensor have been reported. With active cantilever dimensions of 200×100×5 μm³ formed by etching processes, the pyroelectric micro-electro-mechanical system (pyro/MEMS) structure exhibits a much superior performance to that of a traditional IR-sensing bulk structure under the 800-μW incident optical light with wavelength of 970 nm. Two-order improvement in current responsivity is obtained for the pyro/MEMS structure. This shows the substrate effect on the performance of a pyro/MEMS IR sensor is very significant. A simple model has also been proposed to illustrate the substrate effect more comprehensively     

基于改进LK光流法的MEMS面内运动分析技术

为获取微机电系统(MEMS)面内运动过程中的动态 特征,文中提出了一个MEMS面内运 动测量系统．该系统通过FPGA产生相机外触发和频闪光源两路时钟同步驱动脉冲,利用频闪 成像的原理对谐振状态下的MEMS器件进行图像采样．对图像序列进行Canny边缘检测后,引 入Shi-Tomasi角点和Lucas-Kanade光流追踪的方法进行运动分析,获取器件的幅相信息参 数 ．使用该系统对一个定制的微陀螺仪进行实验测量,实验证明该技术可实现MEMS面内运动的 亚像素精度测量,与传统的LK光流法匹配相比,能够减少由图像灰度值变化带来的测量误差 ,同时该方法具有较好的测量精度,测量重复性可达10 nm。     

Autonomous mobile target tracking system based on grey-fuzzycontrol algorithm

This paper presents a new position-based tracking system for autonomous mobile target tracking task. A grey-fuzzy controller (GFC) is developed for motion control of the tracker, in which dynamics models of the target and tracker are not required a priori. The target detection is based on the adaptive visual detector (AVD), which can online adjust the histogram model based on the change of surrounding conditions, such as light variation, in a natural environment. The AVD and GFC are integrated together for mobile target-tracking applications. There are several advantages of the integrated system, in particular: (1) it can rapidly learn the target appearance model for the detection involved with the tracking task; (2) the temporal dynamics model of the target motion can be approximated for the predictive localization of the moving target; and (3) the system can deal with the uncertain environmental conditions to ensure the tracking performance by GFC. Three mobile robots in the authors' laboratory have been used to demonstrate the success of this integrated system experimentally. They also conduct target tracking experiments, in which Chung Cheng-I tracks various moving targets. The results demonstrate the robustness and flexibility of the overall system in dealing with mobile target-tracking problems under varied natural environment conditions     

一种直线轨迹跟踪的视觉传感器

提出了一种实现直线轨迹跟踪的视觉传感器方案，详细讨论了传感器的基本结构和工作原理，并对其中涉及的数字图像处理技术进行了深入研究。该传感器由激光扫描单元和图像采集处理单元2部分组成，其中，激光扫描单元采用三角法测量原理，利用一维视觉传感扫描的方法实现直线运动物体的轨迹跟踪；图像采集处理单元则利用FPGA和DSP对CCD的输出数据进行高速的数字化处理，并引导后端的执行机构进行相应动作。实验表明，本传感器能以60line／s的速度对被测物进行扫描，并在主机界面上清晰地显示被测物的直线距离信息，测量分辨率可达14μm。     

Interaction control of an industrial manipulator using LPV techniques

This paper presents the design and implementation of a hybrid force/motion control scheme on a six-degrees-of-freedom robotic manipulator employing a gain-scheduled linear parameter-varying (LPV) controller. A nonlinear dynamic model of the manipulator is obtained and the unknown parameters are estimated. The manipulator is decomposed into an inner and a wrist submodel, and a practical way is proposed to investigate the coupling between them. The motion control part of the hybrid controller which is the main focus of this paper is formed by a combination of an LPV controller and a model-based inverse dynamics controller for the inner submodel and the wrist joints, respectively. A quasi-LPV model with a reduced number of scheduling parameters is derived for the inner submodel, and a polytopic LPV gain-scheduled controller is synthesized in a two-degrees-of-freedom structure including feedback and feedforward parts, which is augmented by a friction compensation term. A PD controller with a feedforward path is designed to control the interaction force. The proposed hybrid force/motion scheme is implemented on the 6-DOF CRS A465 robotic manipulator to perform a writing task. Comparison of the results with those of a hybrid force/motion controller with a plain model-based inverse dynamics motion control and the same force control shows that the proposed controller improves the position tracking performance significantly.     

Computational sensor for visual tracking with attention

This paper presents a VLSI embodiment of an optical tracking computational sensor which focuses attention on a salient target in its field of view. Using both low-latency massive parallel processing and top-down sensory adaptation, the sensor suppresses interference front features irrelevant for the task at hand, and tracks a target of interest at speeds of up to 7000 pixels/s. The sensor locks onto the target to continuously provide control for the execution of a perceptually guided activity. The sensor prototype, a 24×24 array of cells, is built in 2-μm CMOS technology. Each cell occupies 62 μm×62 μm of silicon, and contains a photodetector and processing electronics     

Abrupt motion tracking via intensively adaptive Markov-chain Monte Carlo sampling

The robust tracking of abrupt motion is a challenging task in computer vision due to its large motion uncertainty. While various particle filters and conventional Markov-chain Monte Carlo (MCMC) methods have been proposed for visual tracking, these methods often suffer from the well-known local-trap problem or from poor convergence rate. In this paper, we propose a novel sampling-based tracking scheme for the abrupt motion problem in the Bayesian filtering framework. To effectively handle the local-trap problem, we first introduce the stochastic approximation Monte Carlo (SAMC) sampling method into the Bayesian filter tracking framework, in which the filtering distribution is adaptively estimated as the sampling proceeds, and thus, a good approximation to the target distribution is achieved. In addition, we propose a new MCMC sampler with intensive adaptation to further improve the sampling efficiency, which combines a density-grid-based predictive model with the SAMC sampling, to give a proposal adaptation scheme. The proposed method is effective and computationally efficient in addressing the abrupt motion problem. We compare our approach with several alternative tracking algorithms, and extensive experimental results are presented to demonstrate the effectiveness and the efficiency of the proposed method in dealing with various types of abrupt motions.     

Microcontroller‐based simple maximum power point tracking controller for single‐stage solar stand‐alone water pumping system

A simple microcontroller‐based maximum power point tracking controller is proposed for a single‐stage solar stand‐alone water pumping system for remote, isolated, and nonelectrified population, where less maintenance, low cost, and an efficient system is of prime interest. It consists of a photovoltaic (PV) module, a DC–AC converter utilizing space‐vector pulse‐width modulation, an induction motor coupled with a water pump, a voltage sensor, and a current sensor. A space‐vector pulse‐width modulation‐controlled DC–AC converter aided by a fast‐acting on–off supervisory controller with a modified perturb‐and‐observe algorithm performs both the functions of converting PV output voltage to a variable voltage, variable frequency output, as well as extracting the maximum power. A limited variable step size is preferred during transient state, and a steady frequency, which is calculated on the basis of steady‐state oscillation, is set during steady state. A fast‐acting on–off supervisory controller regulates DC link voltage during steady state and enables maximum power point tracking algorithm only during transient state to draw a new voltage reference. In the event of low voltage, the controller switches off the motor but continuously scans for an available PV voltage. The system is not protected against an overcurrent because the maximum current is equal to its short circuit current. The 16‐bit microcontroller dsPIC6010A (Microchip Technology, Inc., Chandler, AZ, USA) is used to implement the control functions. The proposed controller is verified through simulation as well as tested in the laboratory prototype model. The simulation and experimental results show good correlation. Copyright © 2011 John Wiley & Sons, Ltd.     

Sliding Modes in Constrained Systems Control

In this paper, a sliding-mode-based design framework for fully actuated mechanical multibody system is discussed. The framework is based on the possibility to represent complex motion as a collection of tasks and to find effective mapping of the system coordinates that allows decoupling task and constraint control so one is able to enforce concurrently, or in certain time succession, the task and the constraints. The approach seems naturally encompassing the control of motion systems in interaction, and it allows application to bilateral control, multilateral control, etc. Such an approach leads to a more natural interpretation of the system tasks, simpler controller design, and easier establishment of the systems hierarchy. It allows a unified mathematical treatment of task control in the presence of constraints required to be satisfied by the system coordinates. In order to show the applicability of the proposed techniques, simulation and experimental results for high-precision systems in microsystem assembly tasks and bilateral control systems are presented.      

Tracking and Interaction Based on Hybrid Sensing for Virtual Environments

We present a method for tracking and interaction based on hybrid sensing for virtual environments. The proposed method is applied to motion tracking of whole areas, including the user's occlusion space, for a high‐precision interaction. For real‐time motion tracking surrounding a user, we estimate each joint position in the human body using a combination of a depth sensor and a wand‐type physical user interface, which is necessary to convert gyroscope and acceleration values into positional data. Additionally, we construct virtual contents and evaluate the validity of results related to hybrid sensing‐based whole‐body tracking of human motion methods used to compensate for the occluded areas.