Joint Error Research Articles

Video Analysis and Coding for Robust Transmission

Increasing heterogeneity of networks and diversity of user capabilities have determined and sustained a strong interest in robust coding of visual content and flexible adaptation of the bitstreams to network and user conditions. As a result, several methods for robust coding and transmission have been proposed that include multiple description coding, motioncompensated subband video coding, joint source-channel coding, integrated compression and error control, and adaptation/transcoding solutions. These typically increase transmission robustness and network and user awareness by using scalability, error resilience, and adaptivity at little or sometimes no extra cost in coding efficiency. However, the performance of these methods is affected by the diversity of, and complex interactions within, the visual content. Analysis methods can improve the performance of robust methods for coding and transmission by providing solutions to account for vastly different characteristics of the visual content and complex interactions among data components, to achieve optimal or near-optimal robust solutions. Among several benefits, the application of visual analysis methods within robust coding and transmission frameworks such as those mentioned earlier yields content-aware error resilient solutions and improves prioritization of the visual content for coding and transmission. This special issue focuses on the seamless integration of visual analysis methods in, or joint design with, robust compression and transmission solutions. The special issue consists of three sections that address robust video coding architectures and configurations, robust entropy coding methods, and quality issues related to robust coding, respectively:

1301 ワーク・ツール間の6自由度完全相対運動を目指した超精密機械の開発 : 第3報,受動的な連結連鎖の性能(OS4/OS6 パラレルメカニズムとその応用/設計における情報共有)

To realize ultra precise machining or measurement, a machine system generating accurately relative motion between its tool and the workpiece is required as well as the accuracy improvements of each element of the machine. This paper proposes a machine system using a compensation device for 6-degree-of-freedom (6-DOF) motion errors between the tool and the workpiece. A hexapod-type parallel mechanism installed between the tool spindle and the surface plate is passively actuated by a conventional machine. Then, the parallel mechanism measures the 6-DOF motions regardless with temperature fluctuation and external forces because the mechanism has a compensation system for elastic and thermal errors of the joints and the links. Therefore, the tool position and orientation are compensated by using the measured 6-DOF errors. This paper describes the conception and the fundamentals of the system. Moreover, a passively extensible strut with a compensation device for the joint's errors was tested.

Analysis of Decision Feedback Detection for MIMO Rayleigh-Fading Channels and the Optimization of Power and Rate Allocations

For an uncoded, K-transmit, N-receive antenna coherent narrow-band communication system employing a decorrelating decision feedback detector (D-DFD), the exact average (over channel realizations) joint error probability (JEP) as well as the average per-symbol error probabilities (SEPs) are derived without making any simplifying assumptions on error propagation. It is proved that the diversity orders of the JEP and the SEP (of every symbol) is limited by error propagation to N-K+1. Based on our exact error probability analysis, however, we suggest an optimization of JEP over nonnegative quadrature amplitude modulation (QAM) constellation sizes (rates) and average powers across transmitters which yield significant improvements over the usual equal power and equal rate assignment. In fact, the JEP of such an optimized design has the much improved diversity order of N (which is also the diversity order obtained through the optimum maximum-likelihood (ML) detector). Moreover, it is seen that these simple optimized designs can achieve a significant fraction of the /spl epsi/-outage capacity even without outer codes. It is also known-but only through simulations-that when the symbols are detected in certain channel realization-dependent orders it is possible to improve substantially over fixed-order detection in the case of the equal rate and equal power assignment. We provide an analysis for a recently proposed channel-dependent ordering rule and show that it does not provide an improvement of the diversity order of the JEP beyond N-K+1. Another ordering rule that was proposed earlier to maximize the worst case post-detection signal-to-noise ratio (SNR) under the perfect feedback assumption is shown to be optimal under a more compelling criterion that does not involve that simplifying assumption. While efficiently computable, this ordering rule is seen to perform almost as well as the optimal channel-dependent ordering rule that minimizes the conditional JEP (and hence the JEP). Nevertheless, a multiple-input multiple-output (MIMO) system with an optimized rate and power allocation and a fixed order of detection is not only less complex but also has a significantly lower JEP than that of the equal-power, equal-rate system, where transmitters are detected in a channel-dependent order, optimal or otherwise.

Decentralized robust tracking control for uncertain robots

To realize decentralized robust tracking control for robots with uncertain parameters, a new design method is proposed. A robust tracking controller designed by this method consists of two parts: a feedforward controller and a feedback robust controller. A feedforward control is first applied and error dynamics are introduced. For each joint error subsystem a robust controller is designed in two steps: first, a nominal controller is designed for the nominal plant to achieve desired tracking performance, then a robust compensator is added to restrain the influence of the perturbation, that is the difference of the real plant from the nominal plant. The controller designed by the proposed method is a linear time-invariant one. It is shown that robust stability and robust tracking property can be achieved by applying the controller with a sufficiently wide frequency bandwidth. An important feature of the method is that the controller parameters can be tuned on-line easily.

Adaptive control of free-floating space manipulators using dynamically equivalent manipulator model

In this paper, adaptive control of free-floating space manipulators is considered. The dynamics based on the momentum conservation law for the free-floating space manipulator has non-linear parameterization properties. Therefore, the adaptive control based on a linear parameterization model cannot be used in this dynamics. In this paper, the dynamics of the free-floating space manipulator system are derived using the Dynamically Equivalent Model (DEM) approach. The DEM is a fixed-base manipulator system and allows us to linearly parameterize the dynamic equations. Using this linearly parameterized dynamic equation, an adaptive control method is developed to control the system in joint space. Parameter identification and torque calculations are done using the DEM dynamics. Simulations show that the tracking errors of the manipulator joints to a given desired trajectory become zero when the calculated torques act on the joints of the space manipulator system.

パラレルメカニズム型マイクロCMMの研究(第3報) : 対偶誤差補正装置の改良(OS6 パラレルメカニズムとその応用)

パラレルメカニズム型マイクロCMMの研究(第3報) : 対偶誤差補正装置の改良(OS6 パラレルメカニズムとその応用)

Decision feedback with rollout for multiuser detection in synchronous CDMA

Decision feedback (DF) is one of the most popular methods in multiuser detection due to its simplicity and outstanding performance. Despite the efficiency of the DF detector, there is usually a large performance gap between the DF detector and the optimal maximum likelihood detector. Rollout, an emerging technique from planning and optimisation, is employed to improve the performance of the decorrelator-based DF detector for synchronous code division multiple access channels. Simulation results show that the proposed algorithm significantly improves the joint error rate of the DF detector, and even outperforms the sequential group decision feedback detector for similar time complexities. Further, owing to the inherent parallel structure of the proposed algorithm, the method is particularly useful in applications where speed and accuracy are both important.

Robust video transmission over error-prone channels via error correcting arithmetic codes

We propose arithmetic codes (ACs) with a forbidden symbol as a joint entropy coding and error protection tool for robust video transmission over error-prone channels. In particular, we introduce a MAP decoder of ACs, and apply it to the transmission of 3-D SPIHT coded video and RTP/UDP/IP H.264 video with data partitioning. Experimental results show that the proposed system exhibits several advantages with respect to other schemes, and outperforms rate-compatible punctured convolutional (RCPC) codes in the applications considered.

A general framework for determining cutoff values to select pollen analogs with dissimilarity metrics in the modern analog technique

The modern analog technique (MAT) is a quantitative calibration tool for using modern pollen assemblages to interpret fossil pollen assemblages for vegetation and climate reconstruction. When the MAT is applied using multivariate distance metrics, a cutoff value for the metric is often used to determine the presence/absence of analogs in a modern pollen reference set. Two kinds of error arise when a cutoff value is used: (1) false positive error, which occurs when analogy is falsely determined to exist between the vegetation (or other parameter) of a sample of interest and that of a sample in the reference set; and (2) false negative error, which occurs when analogy is falsely determined not to exist. The existing literature focuses primarily on examining cutoff thresholds from the perspective of reducing false positive error, with relatively little attention paid to false negative error and to the inherent trade-off between the two errors. This paper sets forth a general analytical framework for determining cutoff thresholds that minimize the joint occurrence of the two errors, and employs the squared chord distance metric with a newly developed reference set of modern pollen surface samples from southern California, USA, as a demonstration case. It also examines the nature of the tradeoffs that occur if an analyst decides to accept increased risk (beyond the joint minimum) of one of the kinds of error for additional reduction of the other. An asymmetric tradeoff in these risks above and below the joint error minimizing cutoff(s) is described (a more rapid proportionate increase of false negatives at cutoffs below the joint minimum in relation to the proportionate increase of false positives at cutoffs above it), which is controlled by the relative variances of the distributions of like- and non-like-vegetation sample comparisons in terms of the distance metric. This asymmetry is found to be general among sample sets reported using the squared chord distance, but is not general across other distance metrics.

Separate/joint optimization of error feedback and coordinate transformation for roundoff noise minimization in two-dimensional state-space digital filters

This paper is concerned with the minimization of roundoff noise subject to l/sub 2/-norm dynamic-range scaling constraints in two-dimensional (2-D) state-space digital filters. Two methods are proposed, with the first one using error feedback alone and the second one using joint error feedback and coordinate transformation optimization. In the first method, several techniques for the determination of optimal full-scale, block-diagonal, diagonal, and scalar error-feedback matrices for a given 2-D state-space digital filter are proposed. In the second method, an iterative approach for minimizing the roundoff noise under l/sub 2/-norm dynamic-range scaling constraints is developed by jointly optimizing a scalar error-feedback matrix and a coordinate transformation matrix, which may be regarded as an alternative approach to the conventional method for synthesizing the optimal 2-D filter structure with minimum roundoff noise. An analytical method for the joint optimization of a general error-feedback matrix and a coordinate transformation matrix under the scaling constraints is also proposed. A numerical example is presented to illustrate the utility of the proposed techniques.

Method for correcting the joint error of a laser writer

We present what we believe to be a new method for correcting the joint error of a laser writer without reduction of throughput. By digitization, we optimize the intensity data of the incident beam at the vicinity of the start point and the end point. The joint error will not be sensitive to lengthening of the start or end point by optimization. The advantage of this method over multipass writing and error scattering is that it requires only a single pass, and thus 80% of the fabrication time will be saved. Experimentation shows the method to be effective.

Microstructural analysis and discontinuities in the brazed zone of copper tubes

In this study, ISO Cu-DHP tubes were brazed using different filler metals such as AWS BCuP-2, BCuP-3, BCuP-5, BAg-16, and DIN L-CuP7 and L-Ag40Cd. The microstructures of the brazed zone of tubes were examined with optical and scanning electron microscopic studies. Hardness measurement and leak-tight tests were conducted. The discontinuities in the brazed zone were determined. The microstructures of the brazed zone of the filler metals generally included two or three different regions. The zones of BCuP-2 and LCuP7 consisted of round phosphorus poor dendrites in a matrix of Cu–P. Ag poor dendrites were observed in a silver rich matrix of BAg-16 filler metal. On the other hand, the microstructures of the BCuP-3, BCuP-5 and L-Ag40Cd consisted of three distinct regions. For instance, dendrites of copper solid solution, Ag–Cu–P eutectic and silver rich dendrites were observed in the brazed zone of BCuP-5 filler metal. Some discontinuities such as porosities, insufficient penetration and positioning errors were observed in the brazed zone of the different filler metals. It was observed that the positioning errors in joints strongly influenced the penetration of filler metal. Silver content decreased the ductility of the brazed zone.

Roundoff noise minimization of state-space digital filters using separate and joint error feedback/coordinate transformation optimization

This paper investigates the problem of minimizing roundoff noise under l/sub 2/-norm dynamic-range scaling constraints in state-space digital fibers by means of error feedback as well as joint error feedback/coordinate transformation optimization. First, several techniques, for the determination of optimal full-scale, diagonal, and scalar error-feedback matrices for a given state-space digital filter are proposed, where three realization schemes, namely, the general state-space realization, input-balanced realization, and optimal realization in the sense of Hwang-Mullis-Roberts are examined. Furthermore, an iterative approach is developed for jointly optimizing a scalar error-feedback matrix and a coordinate transformation matrix so as to minimize the roundoff noise subject to the l/sub 2/-norm dynamic-range scaling constraints. The proposed method may be regarded as an alternative, but much simpler and more general, approach to Hwang's method for synthesizing the optimal filter structure with minimum roundoff noise. A case study is included to illustrate the utility of the proposed techniques.

Application of Joint Error Mutual Compensation for Robot End-effector Pose Accuracy Improvement

A method of robot end-effector pose accuracy improvement using joint error mutual compensation is presented. The developed method allows locating special robot configurations with the highest robot end-effector pose accuracy using joint error maximum mutual compensation. The computer simulation and experimental results confirmed the theory. The method provides the basis for an industrial application of joint error mutual compensation in the conventional robotic manipulators and allows improving robotic manipulator end-effector pose accuracy up to 2 times. The practical areas and typical robotic systems, where the developed framework of joint error mutual compensation could be applied, were presented.

A Study on Abbe's Principle of Six Degree-of-Freedom Parallel Mechanism. Effect of Joint Runout on Motion Error of Mechanism.

Conventional machine tools or coordinate measuring machines consisting of XYZ mechanism have difficulty to satisfy the Abbe's principle which is the basis of the precision mechanism. In other words, there are some offsets between the scale unit axes and the machining point or the measuring point. However, the machining point of machines based on the parallel kinematics can be located in the extension lines of the axes. In this paper, the effects of the joint errors on the motion error of Hexapod mechanism has been analyzed by using a singular value decomposition. The obtained main results are as follows : (1) The joint runout in the direction of the actuated prismatic joint strongly affects the translational motion error of the mechanism ; (2) the joint runouts perpendicular to the direction are negligible ; (3) the optimum link configuration which minimizes the working space and the effects of the runouts is found ; (4) the machining point need not be in the prismatic joint directions ; (5) the tool extension is optimized when the distance between the extensional line of the prismatic joints and machining point is minimized in each link configuration.

122 6 自由度パラレルメカニズムにおけるアッベの原理に関する研究

Conventional machine tools or coordinate measuring machines consisting of XYZ mechanism have difficulty to satisfy the Abbe's principle which is the basis of the precision mechanism. In other words, there are some offsets between the scale unit axes and the machining point or the measuring point. However, the machining point of machines based on the parallel kinematics can be located in the extension lines of the axes. In this study, the effects of the joint errors on the motion error of Hexapod mechanism has been analyzed by using a singular value decomposition. In this paper, it is proved that the point don't have to be located in the lines in the Hexapod. Because six actuating struts are employed, not only positions but also attitudes of the moving platform are able to be measured and actuated. In other word, the Hexapod can control the whole positions and attitudes of the platform. Thus, even if any offset exists between the machining point and the extensional lines, the point can be positioned precisely. Consequently, Hexapod enables to realize accurate machining and measurement regardless of Abbe's principle.

Dual and dual-cross synchronizations in chaotic systems

In this paper we investigate dual synchronization and dual-cross synchronization between a transmitter and a receiver, each consisting of two master and slave systems. We demonstrate our approach using the example of synchronization of chaotic external cavity laser diodes . In the synchronization scheme under consideration the joint error signal, which is the difference between the sum of the outputs from the master systems in the transmitter and the sum of outputs from the slave systems in the receiver, is fed into each slave system and synchronizations between the master lasers and slave lasers under possible configurations are studied. By use of error dynamics we derive existence conditions for synchronization between the transmitter and receiver. We find that in all the studied cases synchronization between the transmitter and receiver occurs when the sum of the contributions from individual master (or slave) systems in the transmitter (or receiver) is equal to unity. For the first time we demonstrate that an arbitrarily chosen master system from the transmitter synchronizes with the slave system from the receiver which has an equal contribution weight to the joint error signal. These findings are considered to be of interest in multichannel communication schemes.

Error analysis of a parallel mechanism considering link stiffness and joint clearances

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

Joint error control and power allocation for video transmission over CDMA networks with multiuser detection

Error control and power allocation for transmitting wireless video over CDMA networks are considered in conjunction with multiuser detection. We map a layered video bitstream to several CDMA fading channels and inject multiple source/parity layers into each of these channels at the transmitter. At the receiver, we employ a linear minimum mean-square error (MMSE) multiuser detector in the uplink and two types of blind linear MMSE detectors, i.e., the direct-matrix-inversion blind detector and the subspace blind detector, in the downlink, for demodulating the received data. For given constraints on the available bandwidth and transmit power, the transmitter determines the optimal power allocation among different CDMA fading channels and the optimal number of source and parity packets to send that offer the best video quality. We formulate a combined optimization problem and give the optimal joint rate and power allocation for each of these three receivers. Simulation results show a performance gain of up to 3.5 dB with joint optimization over with rate optimization only.

2321 パラレルメカニズム型マイクロ CMM の研究(第 2 報) : 対偶部の誤差補正装置

2321 パラレルメカニズム型マイクロ CMM の研究(第 2 報) : 対偶部の誤差補正装置