Achieving Subnanometer Precision in a MEMS-Based Storage Device During Self-Servo Write Process

In probe-based data storage devices, microelectromechanical system-based microscanners are typically used to position the storage medium relative to the read/write probes. Global position sensors are employed to provide position information across the full scan range of these microscanners. However, to achieve repeatable positioning, it is also necessary to have medium-derived position information. Dedicated storage fields known as servo fields are employed to obtain this medium-derived position information. The servo-patterns on these servo fields have to be written using the global position sensors prior to the regular operation of the storage device by employing a scheme known as “self-servo write” process. During this process, subnanometer positioning resolutions, well below that provided by the global position sensors, are desirable. Such precise positioning at acceptable bandwidth requires the directed design of the closed-loop noise sensitivity transfer function so as to minimize the impact of sensing noise. This paper describes control architectures in which the impact of measurement noise on positioning is minimal while providing satisfactory tracking performance. It is estimated that the positioning error due to sensing noise is a remarkably low 0.25 nm. Experimental results are also presented that show error-free operation of the device at high densities.      

High track density for magnetic disk drives with an "Embedded servo" positioning system

The CII-HB "Embedded servo" original technique for disk drive units (such as the D 160) allows operation at high track densities ( 800 TPI) and fast access time. The overall information needed for head displacement and positioning is provided by the data head itself, without any other transducer. Servo transitions, written between the data sectors, are arranged to provide gain information, track logical address, and fine position. This information is used by a microcomputer program to move the head rapidly to the desired track and to lock it in position within an instantaneous error of less than 3 μm (120 μm inches). Practical results are presented and compared with a theoretical model. Limitations and improvements are discussed.     

A track locating servo system utilizing the data heads as absolute position transducers

Magnetic transitions may be compactly written in the normally unused deadspace between the data sectors on each data surface of a moving head disc drive, which may be read by ordinary data heads to obtain absolute position information for use by the track locating servo. A track following system which complements the track locating system is briefly described. Implementation of these techniques eliminates both the need for a servo surface or external encoder, and troublesome reference surface to data surface mechanical tolerance problems.     

Advantages of soft versus hard constraints in self-modeling curve resolution problems. Alternating least squares with penalty functions

A new algorithm for self-modeling curve resolution (SMCR) that yields improved results by incorporating soft constraints is described. The method uses least squares penalty functions to implement constraints in an alternating least squares algorithm, including nonnegativity, unimodality, equality, and closure constraints. By using least squares penalty functions, soft constraints are formulated rather than hard constraints. Significant benefits are (obtained using soft constraints, especially in the form of fewer distortions due to noise in resolved profiles. Soft equality constraints can also be used to introduce incomplete or partial reference information into SMCR solutions. Four different examples demonstrating application of the new method are presented, including resolution of overlapped HPLC-DAD peaks, flow injection analysis data, and batch reaction data measured by UV/visible and near-infrared spectroscopy (NIR). Each example was selected to show one aspect of the significant advantages of soft constraints over traditionally used hard constraints. Incomplete or partial reference information into self-modeling curve resolution models is described. The method offers a substantial improvement in the ability to resolve time-dependent concentration profiles from mixture spectra recorded as a function of time.     

基于电子地图的遥感影像自动粗定位研究

在GIS的基础上,提出了一种新的遥感图像自动定位方法．将GIS技术和遥感技术相结合．利用GIS软件从电子地图中提取出线状图层一定范围内各点的经纬度坐标,将这些信息作为参考源．同时对遥感图像进行二值化和边沿提取,将提取出来的遥感图像的线状特征作为目标源,然后在分辨率匹配和投影变换的基础上对二者进行匹配,引入Hausdorff距离作为相似性测度,最后获取遥感图像的定位信息．     

基于ScSPM-Reranking的高分辨率遥感影像的检索

为了从高分辨率遥感影像中获取详细的地表地物信息,为城市规划、环境监测以及灾情分析提供可靠的数据,进行了高分辨率遥感影像的检索研究,包括对图像的特征提取和图像之间相似度的描述。为了提高图像检索精度,运用了采用稀疏编码(Sc)的空间塔式匹配(Sc SPM)技术和重排序(Reranking)技术,提出了基于Sc SPM结合Reranking(ScSPM-Reranking)的遥感高分辨率影像的检索方法。该方法首先使用Sc SPM提取空间场景的特征,然后结合这些特征使用cityblock距离进行初步检索,最后对初步检索的结果进行Reranking排序,获得高精度的检索结果。同其他检索方法进行了对比实验,实验结果证明,该方法具有较高的检索精度。     

Using the spectral asymmetry of TEA CO2 laser pulses to determine the Doppler-shift sign in coherent lidars with low frequency stability

We develop a method for determinating the relative positions of the lidar transmitter (LT) and the local oscillator (LO) frequencies in Doppler CO(2) lidars. It uses the weak spectral asymmetry of TEA CO(2) laser pulses, defined by a number of secondary peaks at the high-frequency side of the main spectrum peak. Depending on the sign of the beat frequency, these peaks may appear in the demodulated spectrum at either the high- or the low-frequency side. Each laser pulse spectrum is compared with reference spectra with two types of asymmetry, with the cross-correlation coefficients used as criteria. The performance of the method at different values of signal-to-noise ratio is analyzed numerically. The method is also applied to raw data from the lidar reference channel and demonstrates good performance at noise levels lower than the secondary peaks in the pulse spectrum or at a signal-to-noise ratio of >/=20 dB. Application of the pulse spectrum asymmetry for lidar frequency stabilization is analyzed. Lidar operation without frequency stabilization is considered as well. The method offers a simple Doppler lidar hardware for the creation of low-cost coherent lidars, velocimeters-rangefinders, etc.     

A new approach to track finding and fitting in vector drift chambers

We describe the algorithm that is used to find and fit charged particle trajectories in the Mark III detector at SPEAR. The computer program uses a novel non-numerical pattern recognition technique analogous to that used by the digital hardware in the experiment's track finding trigger processor. The technique is both fast and efficient. The complete reconstruction of events is performed at a rate of 37 ms per track on an IBM 3081K, compared with 91 ms per track with a more conventional technique. A preliminary fit of all tracks, suitable for online monitoring, is available after 15 ms per track. Similar techniques are also applicable to future experiments operating in high multiplicity environments. The organization of the algorithms is such as to lead to simple implementation on vector processors.     

A new semi-blind watermarking algorithm using ordered Hadamard transform

An efficient and fast watermarking algorithm based on ordered Hadamard transform (HT) is proposed. Since it uses a few information of watermark image in secret key, it is categorised as a semi-blind method. In our algorithm, both host and watermark images are decomposed into non-overlapping blocks. Next, they are mapped into transform domain as Hadamard coefficients. Then, several high frequency AC components of host image are substituted with watermark coefficients without using any strength factor. Not employing this factor guarantees the embedded image to be retrieved with primary quality. Moreover, using HT offers several advantages of fastness, higher image fidelity, greater reliability of watermark detection and higher data hiding capacity. The experimental results show that our method keeps the quality of host image and is robust to common attacks. Compared to frequency domain and hybrid methods, it has advantages of shorter processing time, acceptable robustness and ease of hardware implementation.     

Information theoretic criterion-based spectrum sensing for cognitive radio

Energy detection is a promising candidate for spectrum sensing of cognitive radio systems due to its merits of simplicity and easy implementation. However, energy detection needs to subjectively pre-configure a threshold and requires the knowledge of noise power. Furthermore, energy detection is vulnerable to noise uncertainty, which inevitably occurs in practical implementations. To solve the above problems, two spectrum sensing methods requiring no knowledge of noise power and no subjective threshold settings are proposed based on the information theoretic criterion. Additionally, the most important advantage of these methods is that their performance is totally unaffected by noise uncertainty. Finally, simulation results are provided to demonstrate the benefits of these methods.     

Design of a wireless assisted pedestrian dead reckoning system - the NavMote experience

In this paper, we combine inertial sensing and sensor network technology to create a pedestrian dead reckoning system. The core of the system is a lightweight sensor-and-wireless-embedded device called NavMote that is carried by a pedestrian. The NavMote gathers information about pedestrian motion from an integrated magnetic compass and accelerometers. When the NavMote comes within range of a sensor network (composed of NetMotes), it downloads the compressed data to the network. The network relays the data via a RelayMote to an information center where the data are processed into an estimate of the pedestrian trajectory based on a dead reckoning algorithm. System details including the NavMote hardware/software, sensor network middleware services, and the dead reckoning algorithm are provided. In particular, simple but effective step detection and step length estimation methods are implemented in order to reduce computation, memory, and communication requirements on the Motes. Static and dynamic calibrations of the compass data are crucial to compensate the heading errors. The dead reckoning performance is further enhanced by wireless telemetry and map matching. Extensive testing results show that satisfactory tracking performance with relatively long operational time is achieved. The paper also serves as a brief survey on pedestrian navigation systems, sensors, and techniques.     

Signal space detection in colored noise

An appropriate adaption of the decision boundaries of the well-known signal space detector (SSD) yields a detector that whitens the input noise in the detector forward path. This new detector, called a whitening signal space detector (WSSD), offers higher reliability without increasing the dimensionality of the signal space. A WSSD can be designed by applying a transformation into the ordinary SSD case. We use the new concept to design a WSSD based on three-dimensional 110 equalization and demonstrate its feasibility and performance. The detector can be implemented with a small increase of hardware and offers a significant improvement in terms of bit error rate, especially at low to moderate channel densities     

A parallel tracking method for acoustic radiation force impulse imaging

Radiation force-based techniques have been developed by several groups for imaging the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one such method that uses commercially available scanners to generate localized radiation forces in tissue. The response of the tissue to the radiation force is determined using conventional B-mode imaging pulses to track micron-scale displacements in tissue. Current research in ARFI imaging is focused on producing real-time images of tissue displacements and related mechanical properties. Obstacles to producing a real-time ARFI imaging modality include data acquisition, processing power, data transfer rates, heating of the transducer, and patient safety concerns. We propose a parallel receive beamforming technique to reduce transducer heating and patient acoustic exposure, and to facilitate data acquisition for real-time ARFI imaging. Custom beam sequencing was used with a commercially available scanner to track tissue displacements with parallel-receive beamforming in tissue-mimicking phantoms. Using simulations, the effects of material properties on parallel tracking are observed. Transducer and tissue heating for parallel tracking are compared to standard ARFI beam sequencing. The effects of tracking beam position and size of the tracked region are also discussed in relation to the size and temporal response of the region of applied force, and the impact on ARFI image contrast and signal-to-noise ratio are quantified.     

Supercapacitive Iontronic Nanofabric Sensing

The study of wearable devices has become a popular research topic recently, where high‐sensitivity, noise proof sensing mechanisms with long‐term wearability play critical roles in a real‐world implementation, while the existing mechanical sensing technologies (i.e., resistive, capacitive, or piezoelectric) have yet offered a satisfactory solution to address them all. Here, we successfully introduced a flexible supercapacitive sensing modality to all‐fabric materials for wearable pressure and force sensing using an elastic ionic–electronic interface. Notably, an electrospun ionic fabric utilizing nanofibrous structures offers an extraordinarily high pressure‐to‐capacitance sensitivity (114 nF kPa^?1), which is at least 1000 times higher than any existing capacitive sensors and one order of magnitude higher than the previously reported ionic devices, with a pressure resolution of 2.4 Pa, achieving high levels of noise immunity and signal stability for wearable applications. In addition, its fabrication process is fully compatible with existing industrial manufacturing and can lead to cost‐effective production for its utility in emerging wearable uses in a foreseeable future.     

The detection of transient-like signals in the presence of a spatially inhomogeneous,nonstationary noise field

We will consider the problem of detecting transient-like signals by means of a spatially distributed array of sensors embedded in an inhomogeneous, nonstationary noise field. If each element of the array has an independent, uncorrupted reference sensor to estimate the noise statistics, then conventional adaptive noise cancellation algorithms can be used to improve the detection process. However, because of practical real-world constraints, independent, uncorrupted reference sensors for the noise might not be available. Thus, the applicability of conventional adaptive noise cancellation techniques is in question. This paper will discuss the development of a knowledge-based signal-processing system that uses Artificial Intelligence (Al) methodologies to adaptively cancel inhomogeneous, nonstationary noise from a distributed array of passive sensors that is constrained to have no noise-reference sensors.     

Digital processing of dual-frequency servo burst in hard disk drives

The trend of increasing areal density, i.e., the number of bits recorded in unit area of the media, continues in the hard disk drive (HDD) industry. This growth is sustained by increasing both the track density and bit density. The track density that can be achieved in a drive depends on many factors such as the dimensions of read/write head and the performance of the head positioning servomechanism. The higher the servo bandwidth, the better the precision achieved in controlling the position of the head. Most of the drives use an embedded servo scheme, which puts a physical constraint on the frequency at which the position error is sampled, and hence, on the achievable bandwidth. The need for a better position error sensing (PES) scheme is the motivation behind exploring alternative methods of servo encoding. This paper addresses different aspects of decoding position error from the dual-frequency servo bursts. It is shown, using both simulation and experimental results, that the proposed scheme offers a feasible solution for generating the PES signal in high-performance HDD.     

基于电感数字变换传感器的智能小车自动循迹系统

为了解决智能循迹小车常用的路径识别传感器易受电磁、光线等干扰的问题,提出了基于电感数字变换传感器的智能小车自动循迹系统。通过分析电感数字变换传感器的工作原理,得出通过扩展传感器感应线圈来扩展感应范围的方法,并基于该方法设计了一种使用单个LDC1000电感数字变换器的传感模块。该模块利用SN74LV4052A模拟开关实现对传感器线圈的扩展;采用MSP430单片机搭建了包括主控模块、电源模块、驱动模块和传感器模块的循迹硬件测试系统;通过实时采集和处理传感器的数据并对小车位置进行调整,实现了硬件测试系统循迹的功能;最后,在测试系统上进行了传感器对金属的感应实验和循迹测试。实验结果表明：该传感器可实时检测到轨道与线圈的水平和垂直距离的变化,可以为循迹功能的实现提供保证;该智能小车在5 mm宽的锡箔纸轨道上可以得到良好的循迹效果。研究结果表明该系统具有适用性强、检测技术稳定的特点,可以广泛应用于工业现场智能循迹。     

基于调频电台非合作式双基地雷达试验系统研究

简要介绍了基于调频电台非合作式双基地雷达试验系统的组成,解决了两个主要直达波对消和目标检测问题。使用基于NLMS方法的非因果滤波器完成阵列多通道的时域均衡, 通过时域、空域联合处理,对消了比噪声强80 dB以上的直达波信号,对民航飞机的探测距离超过300 km。试验验证了该算法的实用性。     

随机噪声对伺服系统跟踪精度的影响

文中以经典的三闭环伺服系统为研究对象,较为详细的论述了测流噪声、测速噪声、测位噪声以及力矩扰动噪声对跟踪精度的影响;推导了四种随机噪声与跟踪精度之间的传递函数;通过对传递函数的变换,得出了系统带宽及校正环节与随机噪声关系,为传感器选择、测量数据处理和校正环节的参数整定提供了参考;给出了随机噪声服从高斯分布情况下的仿真实验,针对随机噪声与跟踪精度的幅频特性,提出了一种分段线性化计算平均衰减倍数的方法.通过这种方法计算了四种随机噪声对跟踪精度的量化影响,并与仿真结果进行了比较,结果表明,这种分段线性化方法是正确可行的.最后,给出了四种噪声同时作用于伺服系统时的计算结果和仿真实验结果,得出了同样的结论.