Required Delay Time Research Articles

АНАЛИТИЧЕСКОЕ РЕЗЕРВИРОВАНИЕ В СИСТЕМЕ АВТОМАТИЧЕСКОГО УПРАВЛЕНИЯ АВИАЦИОННОГО ТУРБОРЕАКТИВНОГО ДВУХКОНТУРНОГО ДВИГАТЕЛЯ НА ОСНОВЕ ОПТИМАЛЬНЫХ НАБЛЮДАТЕЛЕЙ

An analytical redundancy in the automatic control system of a bypass turbojet engine(ACS turbofan engine) based on optimal observers is proposed. This article is based on previouslyobtained results in previous author's works and is a generalization and analysis of these results inorder to develop a methodology for improving the fault tolerance of ACS turbofan engines. Thismethod is based on the use of optimal observers: the Kalman filter and the Yazvinsky filter, consistentwith the mathematical model of the ACS turbofan engine. The analysis of the mathematical model ofthe ACS was carried out using the least squares method in a moving window. The accuracy of identificationof the mathematical model and the required delay time are ensured by optimizing the widthof the moving window. Estimated with the help of optimal observers, the output vector of the ACSturbofan engine includes the following parameters: the rotor speed of the low-pressure compressorrotor nв, the rotor speed of the high-pressure compressor nk, the air pressure behind the highpressurecompressor PK, the gas temperature behind the low-pressure turbine TT. When modeling theKalman filter, a correlation analysis of the input signals was preliminarily carried out. The rationalefor the advantage of the adaptive Yazvinsky filter compared to the Kalman filter is given. The resultsof mathematical modeling of the algorithmic method of reserving the measurement channel of theACS turbofan engine based on the data of flight tests of a bypass engine of the PS-90A type as part ofthe main narrow-body aircraft TU-214 both in stationary and transient modes are presented. Statisticalanalysis of errors in estimation of the output vector of ACS turbofan engines based on the Kalmanand Yazvinsky filter has been carried out. It is shown that the proposed analytical redundancy algorithmensures the fulfillment of the requirements for the accuracy and stability of estimates of theoutput vector of ACS turbofan engines when using the Yazvinsky filter and can be recommended foruse in advanced ACS turbofan engines. Based on the results proposed redundancy method, a directionfor further research has been formed.

Regulating spin reversal in dipolar systems by the quadratic Zeeman effect

A mechanism is advanced suggesting the resolution of the dichotomy of long-lived spin polarization storage versus fast spin reversal at the required time. A system of atoms or molecules is considered interacting through magnetic dipolar forces. The constituents are assumed to possess internal structure allowing for the generation of the alternating-current quadratic Zeeman effect, whose characteristics can be efficiently regulated by quasiresonant dressing. The sample is connected to an electric circuit producing a feedback field acting on spins. By switching on and off the alternating-current quadratic Zeeman effect it is possible to realize spin reversals with a required delay time. The suggested technique of regulated spin reversal can be used in quantum information processing and spintronics.

Compensation of Variable Fractional Delays in the <inline-formula><tex-math notation="LaTeX">$6k\pm 1$</tex-math></inline-formula> Repetitive Controller

Repetitive schemes, aimed for harmonic compensation, are formed by the interconnection of delay lines. They are usually implemented in a digital way, where delay lines are replaced by discrete delays. Each discrete delay is obtained as the ratio between the required delay time in continuous time and the sampling period. A problem arises whenever the delay time of the controller is not an integer multiple of the sampling period. This is referred to in the literature as the fractional delay issue. In repetitive schemes, the delay time is a function of the fundamental frequency of the signals under study. Applications where the fundamental frequency varies with time entails variations in the delay time and, in particular, in its fractional part. This issue is referred to as variable fractional delay (VFD). This work presents a simple solution to implement repetitive schemes subject to a VFD issue. The introduction of an additional filter structure, called the Farrow structure, to each delay line is proposed. Theoretical analysis and design guidelines for the Farrow-structure-based repetitive scheme are provided. In particular, this paper focuses on the $6k\pm 1$ repetitive scheme. Experimental results are presented to confirm the benefits of the proposed solution.

Implementation of a <inline-formula> <tex-math notation="TeX">$6n \pm 1$</tex-math></inline-formula> Repetitive Controller Subject to Fractional Delays

Repetitive schemes represent an attractive solution for harmonic compensation, as they are easy to implement and require a reduced computational effort. Repetitive schemes involve the interconnection of delay lines usually implemented in digital form. A delay line is realized digitally by reserving a given number of memory localities, where samples are allocated and released after a specific number of sampling periods (discrete delay) equivalent to the delay time. Such a discrete delay computed as the ratio between the required delay time and the sampling period must be an integer number in the best scenario. However, the discrete delay may have a fractional part due to limitations on the sampling period or the required delay time. This issue is referred in signal processing literature as fractional delay (FD). This paper presents a solution to implement repetitive schemes subject to such an FD issue. The solution consists in the introduction, on each delay line, of an additional filter aimed to compensate such an FD. In particular, this paper focuses on a repetitive scheme that is able to compensate harmonics 6n ±1. Experimental results are presented to confirm the benefits of the proposed scheme.

A Nonparametric Adaptive Cusum Method And Its Application In Network Anomaly Detection

Detecting anomalies that disrupt the symmetry in two-way communications is an important task for network defense systems. The subtlety and complexity of anomalous traffic challenge the existing detection methods, and the bottleneck is how to set thresholds to adapt to the variability in network traffic. In this paper, a nonparametric adaptive CUSUM (Cumulative Sum) method is presented to meet this challenge. It has three distinct features. (i) No assumption is made on the distribution of the observations. (ii) Its detection threshold is self-adjusted so that it can adapt itself to various traffic conditions. (iii) It can react to the end of an anomaly within a required delay time. Several practical expressions for evaluating this method on its probability of false alarms and detection delays are deduced. Experiments on source-end defense against SYN flooding attacks show the efficacy of this method in detecting low intensity anomalies.

Novel adaptive repetitive algorithm for active vibration control of a variable-speed rotor

The paper describes experimental work that demonstrates the use of repetitive control to attenuate radial vibrations of a variable speed-rotor. The experiments were performed on a rotor test rig having a 3-kg rotor supported by journal bearings. The first bending resonance of the rotor shaft (i.e. the critical speed) was approximately 50 Hz. The objective was to control the radial response at the rotor midpoint by using an actuator located outside the bearing span. A novel aspect of the controller design is that the length of the control output vector of the repetitive controller was updated as a function of the speed of rotation. The speed of rotation determined the required delay time and the repetitive filter length that approximately matches with the delay time. The results obtained were comparable to those achieved in earlier studies with feedforward compensation methods. The best results were achieved when the frequency of rotation enables an integer ratio between disturbance period and sample rate.

An exact algorithm for scheduling identical coupled tasks

The coupled task problem is to schedule n jobs on one machine where each job consists of two subtasks with required delay time between them. The objective is to minimize the makespan. This problem was analyzed in depth by Orman and Potts [3]. They investigated the complexity of different cases depending on the lengths ai and bi of the two subtasks and the delay time Li. Open image in new windowOpen image in new window-hardness proofs or polynomial algorithms were given for all cases except for the one where ai=a, bi=b and Li=L. In this paper we present an exact algorithm for this problem with time complexity O(nr2L) where Open image in new window holds. Therefore the algorithm is linear in the number of jobs for fixed L.

Basic configuration of ATM network path failure restoration using diversity coding

This paper describes a failure resistant network using diversity coding. The technique uses error correcting codes constructed across logically independent virtual paths in ATM networks. This enables almost instantaneous data recovery from facility failure and does not need rerouting. The author proposes a basic system architecture suitable for fast path failure restoration in ATM-based networks. The analyses include the parity path capacity ratio, the required delay time for coding, the buffer size of the path delay equalizer, and the performance of the path failure alarm system. The author also shows that the proposed system efficiently reduces path failure recovery time. © 1998 Scripta Technica, Electron Comm Jpn Pt 1, 81(10): 30–40, 1998

Performance of the Viterbi algorithm for interleaved convolutional codes

This paper presents a maximum-likelihood decoder for error-burst channels with a very efficient implementation. In particular, the encoder is formed of an interleaved convolutional code with generator polynomials of the type [g/sup (1)/(D/sup I/), g/sup (2)/(D/sup I/)] (for a rate 1/2 coder), where I may assume a very high integer value. The decoder consists of the Viterbi algorithm (VA) optimized for these sparse polynomials. For a given decoded bit-error probability, the required delay time and memory requirements of this approach are more inferior by far than those of the traditional method of interleaving. Moreover, for bursts of an average length less than 1/2, this method provides better performance than the dual-mode burst-error-correcting algorithm.

Investigation of an SF/sub 6/ ultra high voltage circuit breaker using an opening resistor and auxiliary interrupter

Stresses of an interrupter during current interruption with a resistor in a UHV power system were calculated with a simple method. Interrupting abilities of some interrupters were compared by interrupting tests. A small puffer type interrupter showed the most suitable characteristics for the resistor interrupter. To realize a time interval of 28 ms from the opening of the main interrupter to the opening of the resistor interrupter, a delayed operating mechanism was constructed with independently movable parts. The operating characteristics of the mechanism were measured, and the required delay time was achieved. >

Constant and Variable Operating-Angle Sprinklers for Traveler Irrigation

ABSTRACT DIGITAL simulations were used to determine the amount of water applied by a traveler irrigation system. The simulations included an initial stationary set (travel delay) to provide additional water behind the start position of the traveler. A comparison of two series of simulations was made to determine the potential of utilizing an alternate sprinkler operating angle during the initial delay period. This was accomplished by conducting one series of simulations with a constant sprinkler operating angle and a second series with differing sprinkler angles for the delay and travel periods. Required delay time, uniformity of application and the volume of water applied beyond the effective field boundary were used as the performance criteria used in the comparison. Results show that, under certain conditions, uniformity can be improved in this initial set area if the angle of rotation during the initial delay period is smaller than the angle of rotation at which the sprinkler travels through the field.