Direct sensorimotor control for low-cost mobile trackingapplications

A biologically inspired system for tracking objects in a visual scene is presented. The uniqueness of the system is in the absence of a microcontroller to convert sensory information to tracking decisions, reducing power, size, weight, and cost of the overall system. The system consists of a mobile vehicle outfitted with a custom analog VLSI architecture for encoding the position of an object of interest in the vehicles's field of view. Once determined, the object of interest retains hysteresis proportional to its size and intensity to limit the potential for distraction by other objects in the sensing environment. The encoded position of the object of interest is directly converted to a series of motor control signals to drive the vehicle in the direction of the object. The motor drive signals are pulse width modulated to control the speed and direction of travel induced by two de motors via a conventional differential steering arrangement. Neural oscillators are used to drive the de motors to provide a compact single-chip system for tracking bright objects. The nature of the system is sufficiently modular so that it can be adapted relatively easily to tracking other features of visual objects and even to objects representative of other sensing modalities. The system described here is one of the first efforts to fully integrate and apply analog VLSI (aVLSI) sensorimotor control to a mobile vehicle and to analyze the complete system from a control systems' perspective. The system described here has the advantages of aVLSI integration in its small size (0.011-mm² elements), low power (0.3 μW per element), and fast system response time (1.5 ms from sensory input to motor response)     

Tracking control of a piezoceramic actuator with hysteresis compensation using inverse Preisach model

This paper presents the classical Preisach hysteresis modeling and tracking control of a curved pre-stressed piezoceramic patch actuator system with severe hysteresis. The actuator is also flexible with very small inherent damping. It has potential applications in active antennas. A series of tests are conducted to study the hysteresis properties of the piezoceramic actuator system. The numerical expressions of the classical Preisach model for different input variations are presented. The classical Preisach model is applied to simulate the static hysteresis behavior of the system. Higher order hysteresis reversal curves predicted by the classical Preisach model are verified experimentally. The good agreement found between the measured and predicted curves showed that the classical Preisach model is an effective mean for modeling the hysteresis of the piezoceramic actuator system. Subsequently, the inverse classical Preisach model is established and applied to cancel the hysteresis the piezoceramic actuator system for the real-time microposition tracking control. In order to improve the control accuracy and to increase damping of the actuator system, a cascaded PD/lead-lag feedback controller is designed with consideration of the dynamics of the actuator. In the experiments, two cases are considered, control with major loop hysteresis compensation, and control with minor loop hysteresis compensation. Experimental results show that RMS tracking errors are reduced by 50% to 70% if the hysteresis compensation is added in the feedforward path in both cases. Therefore, hysteresis compensation with the feedback controller greatly improves the tracking control accuracy of the piezoceramic actuator.     

AntiGroupWare and Second Messenger

Decision-making in groups has great potential due to the possibilities for pooling ideas and sharing knowledge, but also great drawbacks due to the social pressures inherent in these situations that can limit free exchange of these ideas and knowledge. This paper presents two technology-based approaches to improving group decision-making, Second Messenger and AntiGroupWare. Second Messenger — a system that encourages groups to change their interaction styles during meetings — is designed to improve meetings, while AntiGroupWare — an on-line polling system that allows companies to gather information through flexible, iterative polling of its employees — is designed to avoid them altogether.     

Space optical communications with the Nd: YAG laser

The development of a Nd : YAG space laser communication system is discussed with respect to history, potential applications, and present status. The basic design of an Air Force Space Communications Flight Test operable at a data rate of 1000 Mbit/s is described at both the system and component level. An engineering feasibility model of this system has been completed, and the results of tests data are reported. Communications at 1000 Mbit/s with a receiver sensitivity of 20 photoelectrons/bit was demonstrated for a bit error rate of 10^-6, interterminal tracking with angle erros less than 1 µrad, and station to station acquisition in less than 6 s. A simulated range of 40 000 km was used.     

Analysis of a satellite antenna tracking loop driven by BPSK modulated signals

The subject of this paper is an antenna tracking system used to maintain an antenna on board a geosynchronous (GEO) satellite, pointed towards a low earth orbit (LEO) satellite. The tracking system uses the BPSK modulated signals transmitted from the LEO satellite. The signal is received by an electronically switched antenna beam. A suitable processing of the received signal level then generates an error voltage which drives a tracking loop. The measurement of the received signal level is implemented by a power detector. Analysis of the antenna tracking algorithm is carried out and the performance is given in terms of linearized mean-square tracking error. The mean-square tracking error is related to the antenna beam parameters, to the closed loop bandwidth and to the statistics of the power measurement process. In particular, it is shown that a key parameter for the tracking loop performance is the signal-to-noise ratio (SNR) at the power detector output, which is inversely proportional to the variance of the pointing error, and a theory has been developed to find an accurate expression for the SNR. © 1997 John Wiley & Sons, Ltd.     

DT-MRI fiber tracking: a shortest paths approach

We derive a new fiber tracking algorithm for DT-MRI that parts with the locally “greedy” paradigm intrinsic to conventional tracking algorithms. We demonstrate the ability to precisely reconstruct a diverse range of fiber trajectories in authentic and computer-generated DT-MRI data, for which well-known conventional tracking algorithms are shown to fail. Our approach is to pose fiber tracking as a problem in computing shortest paths in a weighted digraph. Voxels serve as vertices, and edges are included between neighboring voxels. We assign probabilities (weights) to edges using a Bayesian framework. Higher probabilities are assigned to edges that are aligned with fiber trajectories in their close proximity. We compute optimal paths of maximum probability using computationally scalable shortest path algorithms. The salient features of our approach are: global optimality—unlike conventional tracking algorithms, local errors do not accumulate and one “wrong-turn” does not spell disaster; a target point is specified a priori; precise reconstruction is demonstrated for extremely low signal-to-noise ratio; impartiality to which of two endpoints is used as a seed; and, faster computation times than conventional all-paths tracking. We can use our new tracking algorithm in either a single-path tracking mode (deterministic tracking) or an all-paths tracking mode (probabilistic tracking).      

High Precision Image Centroid Computation via an Adaptive K-Winner-Take-all Circuit in Conjunction with a Dynamic Element Matching Algorithm for Star Tracking Applications

An approach for implementing a high precision image target centroid—center of mass (COM) detection system via an adaptive K-winner-take-all (WTA) circuit in conjunction with a 2-D dynamic element matching (DEM) algorithm implementation for image sensor arrays is proposed. The proposed system outputs a high precision COM location of the most salient target in a programmable active region of the field of view (FOV) for star tracking purposes and is suitable for real time applications. The system allows target selection and locking with multiple targets tracking capability. This solution utilizes the separability property of the COM, and therefore reduces the computational complexity by utilizing 1-D circuits for the computation. The DEM algorithm, commonly used in ADC and DAC circuits, allows reducing the required WTA circuit precision to 5–6 bits, while still achieving a high output precision. Simulation results prove the concept and demonstrate the high precision COM result. In addition, a possible low-level hardware implementation is described.     

用于多目标自动识别的光互连神经网络系统

本文报道了用于多目标自动识别的光互连神经网络系统。该系统不仅识别目标类别多、识别率高,而且结构小巧可离台工作。由于它在一定程度上模仿了视觉识别功能,故可广泛用于军事预警、目标跟踪、交通管理、产品分类、工业在线检测以及机器视觉等。     

被动导引头辐射源跟踪新算法研究

由于被动导引头辐射源跟踪系统非线性较强,传统的跟踪滤波算法是粒子滤波（PF）、U卡尔曼滤波（UKF）。但这些算法都存在着一定的缺陷,粒子滤波算法收敛速度慢、计算量大,UKF跟踪精度低。针对上述问题,提出了一种基于PF算法的新的跟踪滤波算法PUKF。该算法采用粒子滤波和U卡尔曼滤波加权的思想对目标实现初始的捕捉,然后通过UKF算法对目标进行跟踪保持。该算法受初始状态影响小,跟踪的精度高,收敛速度快,系统性能稳定。仿真实验表明了在被动辐射源跟踪系统中该算法的可行性和有效性。     

扰动对红外目标识别与跟踪的影响分析

作为精确打击武器系统的重要组成部分,红外跟踪系统主要用于在 运动载体上对目标进行搜索、识别、瞄准和跟踪。载体扰动会对红外跟踪系统的性能产生影 响,因此需要隔离扰动和消除扰动对跟踪的影响。通过对红外成像系统的原理进行研究,查 找出了可能造成红外图像扰动的因素,定性分析了扰动对设备造成的影响,最后为设备使用中如 何克服扰动影响提出了建议。     

湖面自由空间光通信信标光的粗跟踪设计与实验

以湖面信标光为真实移动跟踪目标,设计了二维粗跟踪演示系统,验证空间光通信捕获、跟踪和对准(ATP)系统对机动目标的跟踪性能。采用双DSP和两轴精密转台搭建了粗跟踪的硬件平台。采用直方图阈值分割法将信标光从复杂的湖面背景中分离出来。采用预测自校正控制算法设计粗跟踪系统的控制器,具有较好的鲁棒性。进行了针对湖面移动信标光的二维跟踪实验,实验结果表明,粗跟踪系统有较好的跟踪精度,跟踪精度与跟踪距离远近关系不大,满足空间光通信跟踪系统的要求。     

基于ARM的太阳跟踪控制系统设计

为提高跟踪式聚光光伏系统的发电效率,设计了一种基于ARM的太阳自动跟踪控制系统。系统采用视日运动与四象限传感器反馈相结合的太阳方向判断方法,同时增加了独立的光强传感器以确定是否启用跟踪系统(如阴天、雨天);论述了跟踪控制系统的机械结构及软硬件电路设计。测试结果表明,该跟踪系统功耗低、性能可靠且控制精度高(±1.5°),并可实现高精度跟踪太阳,满足了聚光光伏发电控制要求。     

A multiprocessor-oriented visual tracking system

The design and prototypal realization of a visual tracking system is presented. The approach to target identification is nonconventional, in that it relies on an architecture composed of multiple standard neural networks (multilayer perceptrons) and exploits the information contained in simple features extracted from images, performing a small number of operations. Therefore, the tracking functions are learned by examples, rather than implemented directly. The system demonstrates that a quite complex task such as visual target tracking can be easily obtained by a suitable neural architecture. The fast tracking algorithm and the parallel structure allow a true real-time operation. The system exploits a two-level neural-network hierarchy with a number of parallel networks and an “arbiter”. The training set consists of various geometrical shapes, preprocessed to yield the data vectors. The experimental hardware implementation is based on multiple processing units, implementing the neural architecture, and serves as a prototype for the analysis of the system in practice. A small-sized realization can also be obtained     

适用于光电跟踪仪的高速目标跟踪控制算法

为了提高光电跟踪仪对于高速运动目标的跟踪精度和稳定性,提出一种适用于光电跟踪仪的高速目标跟踪控制算法。利用光电跟踪仪、火炮、载体惯导系统、视频跟踪器和激光测距机输出的相关参数,通过一系列坐标转换、递推迭代和坐标反变换,完成瞄准线坐标系下方位速度环和俯仰速度环跟踪前馈补偿参数的计算,并将该参数分别叠加到方位、俯仰跟踪控制回路,参与跟踪控制;采用模拟航路进行验证,该跟踪控制算法对速度2.5 Ma的高速运动目标,跟踪系统误差和随机误差均小于0.15 mrad。实验结果表明,该方法能有效提高光电跟踪仪对高速运动目标的跟踪精度,响应速度快、动态滞后小。     

Road sign tracking for adaptive cruise control under nonlinear conditions

A vision-based system is described for adaptive cruise control to track road signs from within a moving vehicle. The proposed system has the standard architecture with a particle filter due to its robust tracking performance in a complex environment. In the case of tracking road signs in a real environment, it has great difficulty in predicting time series data by reason of its nonlinear characteristics. To overcome this problem, proposed is a state transition model to which the differences of affine parameters and a fuzzy-autoregressive model are applied. Also, to make an observation model, the Parzen window is used at a measurement step in the particle filter.     

Stochastic noise tolerance: Enhanced full state observer vs. Kalman filter from video tracking perspective

A control-based full state observer scheme is explored for video target tracking application, and is enhanced with a lowpass filter for improving the tracking precision, thus forming an Enhanced Full State Observer (EFSO). The whole design is based on the given lab-generated video sequence with motion of an articulate target. To evaluate the EFSO’s stochastic noise tolerance, a Kalman Filter (KF) is intentionally employed in tracking the same target with the given Gaussian white noises. The comparison results indicate that, for system noises of certain statistics, the proposed EFSO has its own noise resistance capacity that is superior to that of KF and is more advantageous for implementation.     

基于Camera Link接口的图像跟踪系统的设计与实现

为了提高图像跟踪对小目标的跟踪精度,采用高帧频和高分辨率的数字相机作为输入。系统采用以DSP和FPGA以及大容量缓存的硬件架构,通过FPGA的逻辑编程灵活调配系统的资源,将图像采集、图像预处理、图像跟踪、图像显示等功能合理分配至各个硬件单元。经实验验证,各个功能单元达到预期效果。这里介绍的基于Carema Link接口的图像跟踪系统,其显著特点在于图像处理能力强,跟踪精度高。     

Applicability of phase-locked loop to tracking the rhythmic activity in EEGS

Conventional methods of spectral analysis are based on mathematical or numerical algorithms applied to digitized signals. This paper discusses the applicability of the phase-locked loop (PLL) approach for tracking electroencephalogram (EEG) rhythmic bands (delta, theta, alpha, or beta). The use of the PLL for frequency tracking should also aid the development of online EEG interpretation and screening based on frequency characteristics when the PLL is realized by hardware. As a result, two factors in the applicability of the PLL are: (1) translation of the EEG spectrum to a higher-frequency band by a single-sideband (SSB) modulation scheme, and (2) the narrowband spectral feature of the EEG—a small difference between two major frequencies. The PLL output is further quantized according to the EEG rhythmic bands. Our analysis shows that the integrated system is capable of tracking the EEG rhythmic patterns.This work was supported by the National Science Council of Taiwan, Republic of China, under grant NSC87-2213-E-009-128.