Showing papers on "Offset (computer science) published in 2014"

Online temporal calibration for camera-IMU systems

Abstract: When fusing visual and inertial measurements for motion estimation, each measurement's sampling time must be precisely known. This requires knowledge of the time offset that inevitably exists between the two sensors' data streams. The first contribution of this work is an online approach for estimating this time offset, by treating it as an additional state variable to be estimated along with all other variables of interest inertial measurement unit IMU pose and velocity, biases, camera-to-IMU transformation, feature positions. We show that this approach can be employed in pose-tracking with mapped features, in simultaneous localization and mapping, and in visual-inertial odometry. The second main contribution of this paper is an analysis of the identifiability of the time offset between the visual and inertial sensors. We show that the offset is locally identifiable, except in a small number of degenerate motion cases, which we characterize in detail. These degenerate cases are either i cases known to cause loss of observability even when no time offset exists, or ii cases that are unlikely to occur in practice. Our simulation and experimental results validate these theoretical findings, and demonstrate that the proposed approach yields high-precision, consistent estimates, in scenarios involving either known or unknown features, with both constant and time-varying offsets.

Minimum Pearson Distance Detection for Multilevel Channels With Gain and/or Offset Mismatch

Abstract: The performance of certain transmission and storage channels, such as optical data storage and nonvolatile memory (flash), is seriously hampered by the phenomena of unknown offset (drift) or gain. We will show that minimum Pearson distance (MPD) detection, unlike conventional minimum Euclidean distance detection, is immune to offset and/or gain mis- match. MPD detection is used in conjunction with T -constrained codes that consist of q-ary codewords, where in each codeword T reference symbols appear at least once. We will analyze the redundancy of the new q-ary coding technique and compute the error performance of MPD detection in the presence of additive noise. Implementation issues of MPD detection will be discussed, and results of simulations will be given.

On-board object tracking control of a quadcopter with monocular vision

Abstract: The development of an object tracking controller for a quadcopter using an on-board vision system is presented. Using low-cost components, a novel system is introduced that operates entirely on board the quadcopter, without external localization sensors or GPS. A low-frequency monocular computer vision algorithm is applied in closed-loop control to track an object of known color. Parallel PID controllers for aircraft bearing, relative height and range are implemented with feedback from object offset and size in the image frame. The noise exaggerated by measuring range from object pixel area is mitigated with a Kalman filter. Stable closed-loop tracking is demonstrated experimentally for all three control axes when tested individually and coupled together. Individual settling times were under 10 seconds and coupled control settling times under 25 seconds.

Velocity analysis from common offset GPR data inversion: theory and application to synthetic and real data

Abstract: We implemented a procedure to estimate the electromagnetic (EM) velocity using common offset ground penetrating radar (GPR) data. The technique is based on the inversion of reflection amplitudes to compute the series of reflection coefficients used to estimate the velocity in each interpreted layer. The proposed method recursively calculates the incident angles at any interface, taking into account the offset between antennas, and needs as input, in addition to the picked amplitudes values, a reference amplitude for each analysed GPR trace and a velocity value for the first (shallowest) layer. The latter two parameters can be estimated directly from the available data or can be better constrained by further dedicated GPR acquisitions or by additional direct measurements. We critically evaluated the performances for both synthetic and real data acquired with different antenna frequencies and we demonstrated that the new method can be applied in several real situations. Despite the necessary approximations and simplifying hypotheses, the velocity values calculated for each layer are consistent with direct information and with cross-validations obtained considering profiles acquired using different antennas and various path directions. Tests of the method on synthetic and real data sets show that the errors in the calculated velocity fields are quite low and comparable with more demanding velocity analysis techniques. The obtained EM velocity field is crucial in many processing steps, such as, for example, true amplitude recovery, depth conversion and imaging, and provide essential information to characterize the subsurface materials.

Single-phase phase locked loop with dc offset and noise rejection for photovoltaic inverters

Abstract: Proper work of grid-connected converters requires an accurate detection of phase angle, frequency and amplitude of grid voltage. Phase locked loops (PLLs) based on synchronous reference frame theory can be used for estimation of these grid parameters. One of the issues that could appear during estimation of grid parameters is appearance of DC offset in measured grid voltage. This DC component (offset) is usually entered in PLL structure via measurement and A/D conversion process. Undesirable induced DC offset could appear as part of the reference sine current of photovoltaic inverters or other grid-connected converters. A lot of standards define allowed PV inverter's DC current injection in the grid. In this study, we propose an improved PLL structure with capability to fully reject DC offset and noise which could appear in measured input grid voltage. The key component of the proposed PLL is two-phase generator with a closed control loop for DC offset and noise rejection. Obtained simulation and experimental results show that the proposed PLL structure can solve important issues of presence of noise and DC offset in measured grid voltage. The proposed PLL structure shows excellent dynamical performances in conditions of fast changes of grid parameters.

Analysis of the Frequency Offset Effect on Zadoff–Chu Sequence Timing Performance

Abstract: Zadoff-Chu (ZC) sequences have been used as synchronization sequences in modern wireless communication systems, replacing the conventional pseudorandom noise sequences due to their perfect autocorrelation properties. We first study the problem of ambiguity between a timing offset and a frequency offset, which arises when a ZC sequence is used as a synchronization signal. We then show how a frequency offset can impair the timing property of a ZC sequence, causing irreducible timing errors. An analytical framework, particularly the timing spectrum, is developed, which fully characterizes a ZC sequence's timing properties and its fundamental limitations as a time synchronization sequence in the presence of a frequency offset between the transmitter and the receiver. This analytical framework provides a powerful analytical tool for timing signal design and performance analysis of ZC sequences.

Data receivers and methods of implementing data receivers in an integrated circuit

Abstract: A data receiver implemented in an integrated circuit is described. The data receiver comprises an input receiving a data signal; a first equalization circuit coupled to receive the data signal, wherein the first equalization circuit is used to receive the data of the data signal; and a second equalization circuit coupled to receive the data signal, wherein the second equalization circuit is used to adjust a clock phase offset.

Signed distance fields for polygon soup meshes

Abstract: Many meshes in computer animation practice are meant to approximate solid objects, but the provided triangular geometry is often unoriented, non-manifold or contains self-intersections, causing inside/outside of objects to be mathematically ill-defined. We describe a robust and efficient automatic approach to define and compute a signed distance field for arbitrary triangular geometry. Starting with arbitrary (non-manifold) triangular geometry, we first define and extract an offset manifold surface using an unsigned distance field. We then automatically remove any interior surface components. Finally, we exploit the manifoldness of the offset surface to quickly detect interior distance field grid points. We prove that exterior grid points can reuse a shifted original unsigned distance field, whereas for interior cells, we compute the signed field from the offset surface geometry. We demonstrate improved performance both using exact distance fields computed using an octree, and approximate distance fields computed using fast marching. We analyze the time and memory costs for complex meshes that include self-intersections and non-manifold geometry. We demonstrate the effectiveness of our algorithm by using the signed distance field for collision detection and generation of tetrahedral meshes for physically based simulation.

Partial file restore in a data storage system

Abstract: The data storage system according to certain aspects can implement partial file restore, where only a portion of the secondary copy of a file is restored. Such portion may be designated by one or more application offsets for the file. The system may provide an in-chunk index that includes mapping information between the application offsets and the secondary copy offsets. Chunks may refer to logical data units in which secondary copies are stored, and the in-chunk index for a chunk may be stored in secondary storage with the chunk. Because the mapping information may not be provided at a fixed interval, the system can search through application offsets in the in-chunk index to locate the secondary copy offset corresponding to the portion application offset(s). In this manner, the system may restore the designated portion of the secondary copy in a fast and efficient manner by using the in-chunk index.

A Continuous-Time Ripple Reduction Technique for Spinning-Current Hall Sensors

Abstract: This paper presents a new ripple-reduction technique for spinning-current Hall sensors, which obviates the need for low-pass filtering to suppress the ripple caused by up-modulated sensor offset. A continuous-time ripple-free output is achieved by the use of three ripple reduction loops (RRLs), which continuously sense the offset ripple and then use this information to drive a feedback loop that cancels sensor offset before amplification. Since no low-pass filter is involved, the bandwidth of the resulting system can be much higher than the spinning frequency. Moreover, since the front-end no longer has to process sensor offset, the requirements on its dynamic range can be significantly relaxed. A prototype system consisting of a Hall sensor readout system realized in a 0.18 μm CMOS process was combined with three off-chip RRLs realized with off-chip electronics. At a spinning frequency of 1 kHz, the RRLs reduce the offset ripple by more than 40 dB to about 10 μT, while also achieving low offset (25 μT) and wide bandwidth (over 100 kHz).

Calibrating optimal read levels

Abstract: After a predetermined period of time in a life cycle of a flash memory device, a plurality of reliability values corresponding to a plurality of reads of one or more of the plurality of memory cells are generated; each of the reads using a variation of a predetermined read level voltage. An offset voltage is then identified, offset from the read level voltage. The offset voltage corresponds to a zero crossing point in the range of the reliability values. Once the offset voltage is identified, the read level voltage is set to a calibrated voltage based on the offset voltage.

Measuring Coseismic Displacements With Point-Like Targets Offset Tracking

Abstract: Offset tracking is an important complement to measure large ground displacements in both azimuth and range dimensions where synthetic aperture radar (SAR) interferometry is unfeasible. Subpixel offsets can be obtained by searching for the cross-correlation peak calculated from the match patches uniformly distributed on two SAR images. However, it has its limitations, including redundant computation and incorrect estimations on decorrelated patches. In this letter, we propose a simple strategy that performs offset tracking on detected point-like targets (PT). We first detect image patches within bright PT by using a sinc-like template from a single SAR image and then perform offset tracking on them to obtain the pixel shifts. Compared with the standard method, the application on the 2010 M 7.2 El Mayor-Cucapah earthquake shows that the proposed PT offset tracking can significantly increase the cross-correlation and thus result in both efficiency and reliability improvements.

Adaptive digital back-propagation for optical communication systems

Abstract: We study the performance of multicarrier offset modulation and root-raised-cosine shaped multicarrier modulation with aggregate 32.5 GBd symbol rate and show that offset modulation is preferable for non-zero rolloff factors.

Same-frequency full-duplex self-interference offset device

Abstract: The invention discloses a same-frequency full-duplex self-interference offset device. The same-frequency full-duplex self-interference offset device comprises a transmitting channel, an offset module, a receiving channel, a power detection module and a control module. A radio frequency signal is transmitted to the air by the transmitting channel, and the transmitted signal is coupled to the offset module by the transmitting channel; the offset module is controlled by the control module to adjust the transmitted signal coupled to the offset module by the transmitting channel and acquires an offset signal, wherein the amplitude of the offset signal equals that of a self-interference signal generated by the receiving channel and the phase of the offset signal is opposite to that of the self-interference signal generated by the receiving channel; after the radio frequency signal is received by the receiving channel from the air, the receiving signal and the offset signal output by the offset module are composited to achieve self-interference offset, and the receiving signal after self-interference offset is transmitted to a radio frequency signal receiving end and coupled to the power detection module; the power detection module detects the power intensity of the receiving signal after self-interference offset, and a power detection signal is generated and transmitted to the control module by the power detection module; the control module generates an offset module control signal according to the power detection signal. The same-frequency full-duplex self-interference offset device effectively solves the self-interference problem caused by simultaneous same-frequency signal receiving and transmitting in the wireless same-frequency full-duplex communication process.

Sample adaptive offset control

Abstract: Offset values, such as Sample Adaptive Offset (SAO) values in video coding standards such as the High Efficiency Video Coding standard (HEVC), may be improved by performing calculations and operations that improve the preciseness of these values without materially affecting the signal overhead needed to transmit the more precise values. Such calculations and operations may include applying a quantization factor to a video sample and at least some of its neighbors, comparing the quantized values, and classifying the video sample as a minimum, maximum, or one of various types of edges based on the comparison. Other sample range, offset mode, and/or offset precision parameters may be calculated and transmitted with metadata to improve the precision of offset values.

Multi-parameter inversion through offset dependent elastic fwi

Abstract: Method for multi-parameter inversion using elastic inversion. This method decomposes data into offset/angle groups and performs inversion on them in sequential order. This method can significantly speed up convergence of the iterative inversion process, and is therefore most advantageous when used for full waveform inversion (FWI). The present inventive approach draws upon relationships between reflection energy and reflection angle, or equivalently, offset dependence in elastic FWI. The invention uses recognition that the amplitudes of small angle (near offset) reflections are largely determined by acoustic impedance alone (1), independent for the most part of Vp/Vs. Large angle (middle and far offset) reflections are affected by Ip, Vp/Vs (2) and other earth parameters such as density (3) and anisotropy. Therefore, the present inventive method decomposes data into angle or offset groups in performing multi-parameter FWI to reduce crosstalk between the different model parameters being determined in the inversion.

Method and device for preventing shaking of video image

Abstract: The invention discloses a method and device for preventing shaking of a video image. The method for preventing shaking of the video image comprises the steps that the focusing positional value of a video image to be processed when focusing shooting is conducted by shooting equipment is obtained and serves as a current focusing positional value; a shooting object distance corresponding to the current focusing positional value is determined based on the corresponding relation between a focusing positional value and a shooting object distance which are established in advance, and the shooting object distance corresponding to the current focusing positional value serves as the current shooting object distance; the image offset corresponding to the current shooting object distance and a current camera lens rotating angle is determined based on the corresponding relation among the shooting object distance, a camera lens rotating angle and image offset which are established in advance, and the image offset corresponding to the current shooting object distance and the current camera lens rotating angle serves as the adjustment amount of image offset, wherein a camera rotating angle, of the video image to be processed, which is obtained when focusing shooting is conducted by the shooting equipment serves as the current camera lens rotating angle, and video image anti-shaking offset processing is conducted on the video image to be processed by means of the adjustment amount of image offset. By the adoption of the method for preventing shaking of the video image, the anti-shaking effect of the video image is improved.

Programming Select Gate Transistors And Memory Cells Using Dynamic Verify Level

Abstract: Programming accuracy is increased for select gate transistors and memory cells by using a dynamic verify voltage which increases from an initial level to a final level during a programming operation. Faster-programming transistors are locked out from programming before slower-programming transistors, but experience program disturb which increases their threshold voltage to a common level with the slower-programming transistors at the conclusion of the programming operation. For programming of memory cells to different target data states, an offset between the initial and final verify levels can be different for each data state. In one approach, the offset is greater for lower target data states. The increases in the dynamic verify voltage can be progressively smaller with each subsequent program-verify iteration of the programming operation. The start of the increase can be adapted to the programming progress or can be at a predetermined program-verify iteration.

Power distribution network fault arc extinction method by connecting neutral point to the ground through multi-level converter

Abstract: The invention relates to a power distribution network fault arc extinction method by connecting a neutral point to the ground through multi-level converter. The power distribution network fault arc extinction method is characterized in that the cascade H-bridge multi-level converter is adopted and directly connected at the position of the neutral point of a power distribution network through a reactor; at the initial moment when the power distribution network has a single-phase earth fault, synthetic operation is conducted to generate offset currents needed to be injected (img file='69356dest_path_image001. TIF'wi'19' he'=25' /), then the offset currents are quickly put into the multi-level converter, the multi-level converter is controlled by aid of the current tracking control algorithm and the PWM (Pulse-Width Modulation) modulation strategy to generate offset currents (img file='652784dest_path_image001. TIF'wi'19' he'=25' /), and the offset currents are put into the neutral point of the power distribution network so as to compensate grounding total currents of the fault point. In addition, the fault phase voltage is forced to be 0 constantly so the instantaneous grounding fault can be cleared automatically, and further the technical problem of the existing fault arc extinction technology of poor arc extinction effect can be solved.

Probabilistic solution of vibro-impact stochastic Duffing systems with a unilateral non-zero offset barrier

Abstract: This paper proposes a solution procedure for obtaining an approximate probability density function (PDF) of the response of vibro-impact Duffing systems with a unilateral non-zero offset barrier. The impact model is used with classical impacts with instantaneous velocity jumps and the excitation is modelled by a zero mean stationary Gaussian white noise. First the original vibro-impact system is converted into a system without barriers by adopting the Zhuravlev non-smooth coordinate transformation. Second the PDF of the converted system is obtained by solving the Fokker–Planck (FP) equation with the exponential–polynomial closure (EPC) method. Last the PDF of the original system is achieved using the well-established methodology on seeking the PDF distribution of a function of a random variable. A further parametric study is also conducted to evaluate the effectiveness of the proposed solution procedure. Comparison with the simulated result shows that when lightly inelastic impacts occur (i.e, the restitution coefficient is very close to 1.0), the technique of the Zhuravlev non-smooth coordinate transformation is feasible. The transformed system can adequately represent the original system. Consequently the EPC method can provide a good approximate PDF solution. The tail region of the PDF is also approximated well. The analysis further shows that the non-zero offset significantly affects the shape of the PDF distribution of displacement.

Offset range operation striping to improve concurrency of execution and reduce contention among resources

Abstract: An offset range striping technique increases concurrency of operation execution directed to metadata managed by a volume layer of a storage input/output (I/O) stack, while reducing contention among resources of one or more nodes of a cluster. A logical unit (LUN) may be apportioned into multiple volumes, each of which may be partitioned into multiple regions, wherein each region is represented by a dense tree. The technique increases concurrency of operation execution (e.g., modifications to the metadata at the offset ranges), while reducing contention among the resources (e.g., CPUs and NVLogs) by distributing the offset range operations among the regions and mapping the regions to services and NVLogs. Such increased concurrency and reduction of contention may be achieved by implementation of the technique to (i) apportion each region into disjoint chunks (i.e., stripes) of contiguous offset ranges; (ii) organize a plurality of regions into one or more zones and populate a first zone before allocating a second zone; and (iii) stagger the mapping of services to starting regions of the volumes.

Method and apparatus for optimizing finite automata processing

Abstract: A method, and corresponding apparatus and system are provided for optimizing matching at least one regular expression pattern in an input stream by walking at least one finite automaton in a speculative manner. The speculative manner may include iteratively walking at least two nodes of a given finite automaton, of the at least one finite automaton, in parallel, with a segment, at a current offset within a payload, of a packet in the input stream, based on positively matching the segment at a given node of the at least two nodes walked in parallel, the current offset being updated to a next offset per iteration.

Digital Offset Trimming Techniques for CMOS MEMS Accelerometers

Abstract: This paper presents a digital trimming technique for canceling the output offsets caused by sensor mismatches in an accelerometer design. The offset cancellation techniques provide fine trimming steps with higher chip area efficiency compared with that of conventional capacitor array compensation approaches. The accelerometer, fabricated in a 0.18- μm complementary metal-oxide-semiconductor micro-electro-mechanical-system process, containing the micro-mechanical structure and readout circuits, occupies only a 0.64 × 0.9 mm2 area. The chip draws 0.4 mA from a 1.8-V supply. The measured sensitivity is 195 mV/g and the nonlinearity is 0.78% within the ±12 g sensing range. The output noise floor is 150 μg/√{Hz}, corresponding to a 1-g 100-Hz sinusoidal acceleration. The output offset voltage can be trimmed from several tens to several hundreds of millivolts down to several millivolts.

Contact between rolling beams and flat surfaces

Abstract: SUMMARY This work presents a new approach to model the contact between a circular cross section beam and a flat surface. In a finite element environment, when working with beam elements in contact with surfaces, it is common to consider node or line to surface approaches for describing contact. An offset can be included in normal gap function due to beam cross section dimensions. Such a procedure can give good results in frictionless scenarios, but the friction effects are not usually properly treated. When friction plays a role (e.g., rolling problems or alternating rolling/sliding) more elaboration is necessary. It is proposed here a method that considers an offset not only in normal gap. The basic idea is to modify the classical definition of tangential gap function in order to include the effect of rigid body rotation that occurs in a rolling scenario and, furthermore, consider the moment of friction force. This paper presents the new gap function definition and also its consistent linearization for a direct implementation in a Newton-Raphson method to solve nonlinear structural problems modeled using beam elements. The methodology can be generalized to any interaction involving elements with rotational degrees of freedom. Copyright © 2013 John Wiley & Sons, Ltd.

Cross-layer parallel processing and offset delay parameters for video coding

Abstract: In an example, a method of coding video data includes determining a location of a reference sample associated with a reference picture of video data based on one or more scaled offset values, where the reference picture is included in a first layer of a multi-layer bitstream and the one or more scaled offset values indicate a difference in scale between the first layer and a second, different layer. The method also includes determining a location of a collocated reference block of video data in the first layer based on the location of the reference sample, and coding a current block of video data in the second layer relative to the collocated reference block.

Implementation and experience with luminosity levelling with offset beam

Abstract: The practice of luminosity levelling with an offset beam has been used as a routine operation in the LHC since 2011. This paper will describe how it has been implemented and what has been the operational experience with the system.

Signal Compensation for Analog Rotor Position Errors due to Nonideal Sinusoidal Encoder Signals

Abstract: This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.