Showing papers on "Offset (computer science) published in 2003"

Disturbance models for offset‐free model‐predictive control

Abstract: Model predictive control algorithms achieve offset-free control objectives by adding integrating disturbances to the process model. The purpose of these additional disturbances is to lump the plant-model mismatch and/or unmodeled disturbances. Its effectiveness has been proven for particular square cases only. For systems with a number of measured variables (p) greater than the number of manipulated variables (m), it is clear that any controller can track without offset at most m controlled variables. One may think that m integrating disturbances are sufficient to guarantee offset-free control in the m controlled variables. We show this idea is incorrect and present general conditions that allow zero steady-state offset. In particular, a number of integrating disturbances equal to the number of measured variables are shown to be sufficient to guarantee zero offset in the controlled variables. These results apply to square and nonsquare, open-loop stable, integrating and unstable systems.

A novel timing estimation method for OFDM systems

Abstract: We present a novel timing offset estimation method for orthogonal frequency division multiplexing systems. The estimator proposed here is designed to avoid the ambiguity which occurs in Schmidl's (1997) timing offset estimation method. The performance of the proposed scheme is presented in terms of mean and mean-square error (MSE) obtained by simulations. The simulation results show that the proposed estimator has a significantly smaller MSE than the other estimators.

Reliable packet monitoring methods and apparatus for high speed networks

Abstract: A method for controlling traffic on a network includes monitoring a data stream, determining a particular byte offset within the monitored stream at which to block flow of the stream, and blocking flow of the data stream at the determined byte offset.

Offsets in Global Positioning System time series

Abstract: [1] Site velocities are a common product of continuous Global Positioning System (CGPS) networks. Estimation of site velocities from their time series can be biased if offsets are present. If left uncorrected, offsets can dominate velocity uncertainties. Artificial (nontectonic) discontinuities may arise from environmental and equipment changes or human intervention and error. Analysis of present GPS data sets reveals that on a component by component basis, one offset occurs every 9 years, although it could be as frequent as one offset every 2 years. The effect offset estimation has on rate uncertainty depends on the noise characteristics in the series. If the noise is white, then estimating a single offset in the center of the series doubles the uncertainty. If the noise is random walk, then neither the position nor the number of offsets in the time series seriously alters the rate uncertainty. Undetected offsets in the time series mimic random walk noise. If an offset detection algorithm is implemented, then there is threshold size below which the algorithm can select the wrong offset epoch. Offset position uncertainty increases as offset size decreases. However, small offset position uncertainties will still result in lower rate uncertainties with respect to undetected offsets. Despite the appeal of estimating offsets by detrending and averaging data either side of the discontinuity, such a strategy only serves to increase the rate and offset uncertainties. The best strategy is still to use the maximum likelihood estimator to simultaneously estimate the linear parameters and the noise components.

Financial management system including an offset payment process

Abstract: The present invention is a system that includes a first financial management system handling receivables and a second financial management system handling payables. The receivables system sends debt offset information to an offset payment system and the payables system sends payment information to the offset payments system. The offset payment system either makes a payment or offsets the payment with the debt. Both of the financial management systems receive offset information from the offset payment system. The system designates, in the respective separate receivables and payables systems, debt and payments that are suitable for offset using threshold criteria such as age, amount, party, number of notices of delinquency, etc. The system allows administrative fees and other charges, such as interest and penalties, to be added to the debt as well as the limiting of the percentage applicable to the offset at the time of the referral. During the referral of the debt to the offset payments system, the debtor as well as other parties, such as credit bureaus, are informed or notified of the delinquent debt and the referral information can be stored in a data warehouse for later analysis. The documents associated with the debt can also be stored as images allowing those involved in the workflow associated with the debt and payments to view images of the documents as needed. When an offset occurs the system feeds the amount of the offset back to the receivables and payables systems to update the records therein to reflect the amount and that the amount was an offset. That is, an authorized payment is shown as fully or partially offset and a debt is shown as fully or partially satisfied via the offset. The records of financial management systems as well as the offset system are updated when a payment is made by the debtor after a referral has occurred, when a decision is made to write-off the debt as well as when the debtor is involved in bankruptcy. The invention also provides for reconciliation of the debts, payments and offsets. Online access to the records is also provided for the debtor as well as the personnel from the organizations of the payable, receivable and offset payment systems.

Offset-based response time analysis of distributed systems scheduled under EDF

Abstract: Offset-based response time analysis of tasks scheduled with fixed priorities has demonstrated to be a powerful tool to analyze many task models with different kinds of timing constraints, like regular periodic tasks, suspending tasks, distributed systems, tasks with varying priorities, multi frame models, etc. Offset-based analysis techniques are capable of performing a global schedulability analysis in distributed systems, as opposed to the less efficient techniques that consider each processing or communication resource as independent. In this paper we extend the offset-based schedulability analysis techniques to system with EDF (earliest deadline first) scheduling, using analytical techniques that are similar to those developed for fixed priority scheduling. With this new analysis, we now have a complete set of techniques to perform the analysis of different task models in distributed heterogeneous systems, i.e., processors and communication networks having either fixed priority or EDF schedulers.

Contour offset approach to spiral toolpath generation with constant scallop height

Abstract: Recently, the application of high-speed machining (HSM) is recognized as an economically viable manufacturing technology. Even though more HSM centers have increasingly been utilized, the conventional toolpath generation methods are usually employed in practice. But the conventional methods have inherent limitations for the HSM application. This paper presents a new toolpath generation algorithm for high-speed finish cutting process. In order to minimize the fluctuation of cutting load and the possibility of chipping on the cutting edge in HSM, a spiral topology toolpath that is to cut continuously with the minimum number of cutter retractions during the cutting operations is developed. This algorithm begins with the contour offset procedure along the boundary curve of the sculptured surface being machined. In the offset procedure, the offset distance is determined such that the scallop height maintains a constant roughness to ensure higher levels of efficiency and quality in high-speed finish machining. Then, the spiral path is generated as a kind of the diagonal curve between the offset curves. This path strategy is able to connect to a neighbor path without a cutter retraction. Therefore, the minimum tool retraction toolpath can be generated. And, it allows the sculptured surface incorporating both steeper and flatter areas to be high-speed machined. Based on these techniques, experimental results are given to verify the proposed approach.

Interpolation and multiple attenuation with migration operators

Abstract: A hyperbolic Radon transform (RT) can be applied with success to attenuate or interpolate hyperbolic events in seismic data. However, this method fails when the hyperbolic events have apexes located at nonzero offset positions. A different RT operator is required for these cases, an operator that scans for hyperbolas with apexes centered at any offset. This procedure defines an extension of the standard hyperbolic RT with hyperbolic basis functions located at every point of the data gather. The mathematical description of such an operator is basically similar to a kinematic poststack time-migration equation, with the horizontal coordinate being not midpoint but offset. In this paper, this transformation is implemented by using a least-squares conjugate gradient algorithm with a sparseness constraint. Two different operators are considered, one in the time domain and the other in the frequency-wavenumber domain (Stolt operator). The sparseness constraint in the time-offset domain is essential for resampling and for interpolation. The frequency-wavenumber domain operator is very efficient, not much more expensive in computation time than a sparse parabolic RT, and much faster than a standard hyperbolic RT. Examples of resampling, interpolation, and coherent noise attenuation using the frequency-wavenumber domain operator are presented. Near and far offset gaps are interpolated in synthetic and real shot gathers, with simultaneous resampling beyond aliasing. Waveforms are well preserved in general except when there is little coherence in the data outside the gaps or events with very different velocities are located at the same time. Multiples of diffractions are predicted and attenuated by subtraction from the data.

A 3D surface offset method for STL‐format models

Abstract: This paper presents a new 3D offset method for modifying CAD model data in the STL format. In this method, vertices, instead of facets, are offset. The magnitude and direction of each vertex offset is calculated using the weighted sum of the normals of the facets that are connected to each vertex. To facilitate the vertex offset calculation, topological information is generated from the collection of unordered triangular facets making up the STL file. A straightforward algorithm is used to calculate the vertex offset using the adjoining facet normals, as identified from the topological information. This newly developed technique can successfully generate inward or outward offsets for STL models. As with any offset methodology, this technique has benefits and drawbacks, which will be discussed in this paper. Finally, conclusions will be made regarding the applicability of the developed methodology.

Satellite antenna phase center offsets and scale errors in GPS solutions

Abstract: ITRF2000 solutions have shown that there are parts-per-billion (ppb)-level scale differences between GPS and other techniques, as well as among various GPS analysis centers (ACs). The trends of the scale differences reach 0.2 ppb per year. It is demonstrated that the uncertainty in the satellite antenna phase center offset (z-direction) is one of the major reasons for the scale differences. The scale change caused by an error in the z_offset can be approximately expressed as: scale change (in ppb)=7.8 × error of z_offset (in meters). Changing the z_offset value of the BLOCK II and IIA satellites from 102 to 95 cm could produce a 0.5-ppb scale variation. For BLOCK IIR satellites the uncertainty of the z_offset is much larger. The number of these satellites increases each year. The accuracy of IGS products could be significantly affected if this problem is not properly solved. Besides scale, satellite antenna phase center uncertainties have perceptible effects on also the clock, zenith path delay, and other solved-for parameters.

An offset-canceling low-noise lock-in architecture for capacitive sensing

Abstract: We describe an offset-canceling low-noise lock-in architecture for capacitive sensing. We take advantage of the properties of modulation and demodulation to separate the signal from the DC offset and use nonlinear multiplicative feedback to cancel the offset. The feedback also attenuates out-of-band noise and further enhances the power of a lock-in technique. Experimentally, in a 1.5-/spl mu/m BiCMOS chip, a fabrication DC offset of 2 mV and an intentional offset of 100 mV were attenuated to 9 /spl mu/V. Our offset-canceling technique could also be useful for practical multipliers that need tolerance to fabrication errors. We present a detailed theoretical noise analysis of our architecture that is confirmed by experiment. As an example application, we demonstrate the use of our architecture in a simple capacitive surface-microelectromechanical-system vibration sensor where the performance is limited by mechanical Brownian noise. However, we show that our electronics limits us to 30 /spl mu/g//spl radic/Hz, which is at least six times lower than the noise floor of commercial state-of-the-art surface-micromachined inertial sensors. Our architecture could, thus, be useful in high-performance inertial sensors with low mechanical noise. In a 1-100-Hz bandwidth, our electronic detection threshold corresponds to a one-part-per-eight-million change in capacitance.

Digital isolation system with ADC offset calibration

Abstract: An improved digital capacitive isolation barrier system is provided that is suitable for use in a telephone or modem where the locally powered circuits must be effectively isolated from the public telephone system, while permitting data transfer across the barrier. In particular, an automatic ADC offset calibration system is provided for determining the magnitude of the ADC offset signal required in the system during a calibration operation, and for providing the calibrated ADC offset signal during normal operation of the isolation barrier system. A modified hybrid circuit is provided for isolating the system input from the telephone line during calibration, and for completing the calibration loop. Fixed bias signals are also provided for the ADC and for a DAC in the system. In a preferred embodiment, the ADC is located on the isolated side of the isolation barrier, while the integrator and register that determine and hold the offset signal are located on the powered side of the isolation barrier.

Joint frequency offset and channel estimation for OFDM

Abstract: We investigate the problem of joint frequency offset and channel estimation for OFDM systems. The complexity of the joint maximum likelihood (ML) estimation procedure motivates us to propose an adaptive MLE algorithm which iterates between estimating the frequency offset and the channel parameters. Pilot tones are used to obtain the initial estimates and then a decision-directed technique provides an effective estimation technique. The joint modified (averaged) Cramer-Rao lower bounds (MCRB) of the channel coefficients and frequency offset estimates are derived and discussed. It is shown that, for the case of a large number of subcarriers in the OFDM system, there is approximately a 6 dB loss in the frequency offset estimate lower bound due to the lack of knowledge of the channel impulse response (CIR). The degradation of the CIR lower bound is less severe and depends on the channel delay spread. We show both analytically and by simulation, that the channel estimate accuracy is less sensitive to unknown frequency offset than the frequency offset estimation is affected by the unknown CIR. Comprehensive simulations have been carried out to validate the effectiveness of the adaptive joint estimation algorithm.

Auto-steering apparatus and method

Abstract: A vehicular guidance method involves providing a user interface using which data can be input to establish a contour for a vehicle to follow, the user interface further configured to receive information from a differential global positioning system (DGPS), determining cross track and offset data using information received from the DGPS, generating control values, using at least vehicular kinematics, the cross track, and the offset data, and providing an output to control steering of the vehicle, using the control values, in a direction to follow the established contour while attempting to minimize the cross track and the offset data.

Optical disk device

Abstract: In an optical disk device in which the focus offset for writing of data can be optimized, a mark is written onto an optical disk at a predetermined focus offset and a change in the signal quality is detected by replaying the mark at various focus offsets. The predetermined focus offset is adjusted based on the change in the signal quality so that the focus offset is set at an optimal value. When an error rate is employed to represent the change in the signal quality, a range of focus offset in which the error rate does not exceed a predetermined value is found. By adjusting the predetermined focus offset for the reference optical disk based on the detected range of focus offset, an optimal focus offset is set.

Calibrated data communication system and method

Abstract: A system includes a first integrated circuit device and a second integrated circuit device. The first device transmits a data sequence to the second integrated circuit device, and the second device samples the data sequence to produce receiver data. The second device then transmits the receiver data back to the first device. Within the first integrated circuit device, a comparison between the data sequence and the receiver data is performed, and based on the comparison, the first device generates information representative of a calibrated timing offset. The first device uses the information representative of the calibrated timing offset to adjust timing associated with transferring write data from the first integrated circuit to the second integrated circuit.

Method and system for calibration of a phase-based sensing system

Abstract: Calibrating the measurement of a distance between a transceiver and an object such as a radiating element (antenna) or a target by continuously changing the wavelength (frequency) of the transmitted wave and observing the rate of phase shift as a function of change in wavelength. The rate of phase shift change as a function of wavelength can be mathematically related to the total displacement to the reflecting object. This calibration technique is applicable to a sensing device comprising a transceiver configured to transmit a signal toward an object, detectors offset in phase to receive the transmitted signal and a reflected signal, and a processor configured with logic to measure a rate of phase shift proportional to the change in wavelength between the transmitted signal and the reflected signal at the detectors. The processor can be further configured with logic to relate the phase shift to displacement between the transceiver and the reflecting object.

Scheduling of Offset Free Systems

Abstract: In this paper, we study the problem of scheduling hard real-time periodic tasks. We consider independent tasks which are characterized by a period, a hard deadline and a computation time, but where the offsets may be chosen by the scheduling algorithm. We first show that we can restrict the problem by considering non-equivalent offset assignments. More precisely, we show that there are finitely many non-equivalent offset assignments and we propose a method to reduce significantly this number and consider only the minimal number of non-equivalent offset assignments. We then propose an optimal offset assignment rule which considers only the non-equivalent offset assignments. However the number of combinations remains exponential; for this reason, we also propose a nearly optimal algorithm with a more reasonable time complexity.

Azimuth measuring device and azimuth measuring method

Abstract: An azimuth measuring device capable of calibrating a magnetic sensor without putting load on a user is provided. When a point having amplified output values Sx, Sy, Sz after a sensitivity correction as x, y, z components is arranged on an xyz coordinate system, an offset information calculation section 8 calculates the center coordinates of such a sphere whose surface is located in the vicinity of each point and calculates an x component of the center coordinates of this sphere as a current offset Cx of an x-axis Hall element HEx, a y component of the center coordinates of this sphere as a current offset Cy of a y-axis Hall element HEy and a z component of the center coordinates of this sphere as a current offset Cz of a z-axis Hall element HEz. It is thereby possible to calibrate the magnetic sensor without putting load on the user.

System with dual rail regulated locked loop

Abstract: An integrated circuit device having a select circuit, a summing circuit and a phase mixer. The select circuit selects one of a plurality of offset values as a selected offset. The summing circuit sums the selected offset with a phase count value, the phase count value indicating a phase difference between a reference clock signal and one of a first plurality of clock signals. The phase mixer combines the first plurality of clock signals in accordance with the sum of the selected offset and the phase count value to generate an output clock signal.

Circuit and method for DC offset calibration and signal processing apparatus using the same

Abstract: A method and circuit for compensating for a DC offset generated in a signal processing apparatus are disclosed. The signal processing apparatus comprises a low noise amplifier; a mixer for mixing the signals outputted from the low noise amplifier with a local oscillation signal; a first offset compensation amplifier for amplifying the output signals of the mixer and compensating for a DC offset existing in the output signals of the mixer firstly according to a first control signal applied thereto; a second offset compensation amplifier connected to the output of the first offset compensation amplifier to amplify signals inputted thereto, the second offset compensation amplifier compensating for a DC offset existing in the input signals secondarily according to a second control signal applied thereto; a variable gain amplifier for amplifying the output signals of the second offset compensation amplifier while controlling gain of the output signals; an offset detector for detecting a DC offset existing in the output signals of the variable gain amplifier; and an offset compensator for generating the first and second control signals to compensate for the DC offset detected by the offset detector.

Switched capacitor circuit with reduced common-mode variations

Abstract: A circuit with a common-mode dual output includes a feedback circuit connected to alternate the states of the dual output between an average output level and a desired common-mode level. The difference between the average and desired levels is proportional to a signal offset level. An impedance matching circuit is connected to the feedback circuit to adjust the signal offset level.

Identification of cutter offset in end milling without a prior knowledge of cutting coefficients

Abstract: This paper presents a method for the identification of cutter offset through milling force without requiring the specific cutting coefficients to be known as priori. The total milling force in the presence of cutter offset is first obtained on the basis of dual cutting mechanisms, where the local force is comprised of a constant plowing force and a linear shearing force proportional to the chip load under the cutter offset. The total milling force is synthesized through convolution and is shown to be the sum of three force components: the nominal chip shearing force component, the plowing force components and the offset related shearing force component. Fourier analysis of these force components reveals the effects of offset geometry and yields formulas for the identification of offset geometry. The identification process requires only two cutting tests and the evaluation of two algebraic expressions; the shearing constants are found from the average forces of cutting tests and the offset geometry is identified from the force component at the spindle frequency. Through numerical simulation and experimental results, the efficacy of the identification method is demonstrated; the effects of feed per tooth and cutting depths on the accuracy of the model are investigated and criteria for the appropriate selection of these parameters are suggested.

Synchronizing Image Sequences of Non-Rigid Objects.

Abstract: For stereopsis, images of a given scene must be captured at the same instant to ensure temporal consistency. For sequences of images (i.e. video streams) this requires the potentially costly and technically complex process of synchronizing cameras. We present a simple but effective method for automatically recovering the sub-frame temporal offset between image sequences taken using unsynchronized cameras. Having recovered the offset, we obtain the affine structure of a non-rigid motion. The technique is demonstrated for the application of human motion capture.

System with phase jumping locked loop circuit

Abstract: An integrated circuit device having a select circuit, a summing circuit and a phase mixer. The select circuit selects one of a plurality of offset values as a selected offset. The summing circuit sums the selected offset with a phase count value, the phase count value indicating a phase difference between a reference clock signal and a first plurality of clock signals. The phase mixer combines the first plurality of clock signals in accordance with the sum of the selected offset and the phase count value to generate an output clock signal.

Contour-parallel offset machining without tool-retractions

Abstract: Contour-parallel offset (CPO) machining uses successive offsets of the boundary curves of the machining region as the tool-path-elements (TPEs) For the efficiency of the CPO machining, it is very important to minimize the number of tool-retractions, which cause additional tool movements and do not contribute to the actual cutting Presented in the paper is a CPO tool-path linking algorithm, which guarantees ‘zero’ number of tool-retractions The algorithm employs the concept of a ‘TPE-net’ providing the information on the parent/child relationships among the TPEs By planning a route through the TPE-net, a CPO tool-path without tool-retractions can be generated

System and method for efficient improvement of image quality in cameras

Abstract: A system and method is provided for efficiently correcting and/or normalizing individual pixel outputs in a sensor array, or another set of image data exhibiting fixed pattern noise, by classing various correction factors into a fixed set of classes and identifying each of the pixels in the array based upon its class. Most classes are used to define specific correction conditions (typically discrete gain/offset values), while some classes are set aside for certain bad pixel conditions. Pixels falling within a certain set of predefined gain/offset ranges that are largely similar, but possibly discrete for each other within an acceptable value range, are assigned to a given class during manufacture and this information is stored within a table in the camera's processor. When data is output from the pixels during runtime, the outputting pixel's given class is identified and the appropriate class-based gain/offset is applied to the output to normalize it as it is transmitted downstream to an image acquisition system (PC memory and/or view screen). When a given class indicates a bad pixel of a certain type (e.g. single bad pixel, bad pixel with right-side adjacent bad pixel, bad pixel with adjacent left-side bad pixel, etc.), the appropriate replacement procedure, using, for example an interpolation based upon neighboring pixels, is applied to generate an acceptable output for the bad pixel.

Method of correcting for time shifts in seismic data resulting from azimuthal variation

Abstract: A seismic data set is processed by applying a transform to the seismic data set that corrects for time shifts in the seismic data set resulting from azimuthal variation. Alternatively, a seismic data set is sorted to common offset gathers. Then, the following steps are applied to each common offset gather: A transform is applied to the common offset gather that corrects for time shifts in the common offset gather resulting from azimuthal variation. The transformed common offset gather is inverse transformed.

Delay mismatched feed forward amplifier system using penalties and floors for control

Abstract: A delay mismatched feed forward amplifier system employing a control system and method using floors and penalties is disclosed. The disclosed control system and method allows the second loop phase adjuster setting to be offset in a repeatable and controlled manner. Applying floors and penalties to offset the steady-state phase adjuster setting modifies the conventional pilot cancellation approach. In the conventional case, pilot cancellation has a distinct minimum that corresponds to the desired adjustment setting. In the disclosed approach, the measured pilot cancellation is clipped to a lower bound or floor to produce a set of equal valued minimum control results. The floor is selected to place a desired phase offset to the phase adjuster at the edge of minimum floor. To ensure that the correct phase adjuster offset is selected from the set of equal valued minimum control results, a control direction based penalty is added. By including both the floor and penalty, the phase adjuster steady state offset will be controlled to the edge of the minimum floor.

Offset assignment showdown: evaluation of DSP address code optimization algorithms

Abstract: Offset assignment is a highly effective DSP address code optimization technique that has been implemented in a number of ANSI C compilers. In this paper we concentrate on a special class of offset assignment problems called "simple offset assignment" (SOA). A number of SOA algorithms have been proposed recently, but experimental results and direct comparisons are still sparse. This makes the practical selection of a suitable SOA algorithm for implementation in a compiler very difficult. This paper aims at closing this gap by providing a comprehensive benchmark suite and empirical evaluation based on real-life application programs. Our results for the first time permit a detailed assessment of all major SOA algorithms. In addition, we propose a new and superior combination of SOA heuristics.