Delay Decomposition Research Articles

On exponential and L2-exponential stability of continuous-time delay-difference systems

In this paper, the exponential stability (ES) and L2-exponential stability (L2-ES) of continuous-time delay-difference systems are studied. Firstly, the relationship between ES and L2-ES of the studied system is systematically presented. Secondly, a novel Lyapunov stability theorem is proposed to test both the ES and L2-ES with a guaranteed convergence rate of the system. Then, for a particular class of delay-difference systems with both point delays and distributed delays having exponential integral kernels, some stability criteria based on linear matrix inequalities (LMIs) are established by selecting suitable Lyapunov-Krasovskii functionals (LKFs) and using a delay decomposition technique. Finally, a numerical example is worked out to illustrate the effectiveness of the theoretical results.

Use of thermal drone in detection and assessment of larval mass temperature in decomposed rabbit carcasses.

Manual ground searches and cadaver dogs are traditional methods for locating remains, but they can be time- and resource-intensive, resulting in the decomposition of bodies and delay in victim identification. Therefore, thermal imaging has been proposed as a potentially useful tool for detecting remains based on their temperature. This study investigated the potential of a novel search technique of thermal drones to detect surface remains through the detection of maggot mass temperatures. Two trials were carried out at Selangor, Malaysia, each utilizing 12 healthy male Oryctolagus cuniculus European white rabbits and DJI Matrice 300 RTK drone China, equipped with a thermal camera; Zenmuse H20T to record the thermal imaging footage of the carcasses at various heights (15, 30, 60-100 m) for 14 days for each trial. Our results demonstrated that the larval masses and corresponding heat emissions were at their largest during the active decay stage; therefore, all the carcasses were observable in thermal images on day 5 and remained until day 7. Statistical analyses showed that (1) no statistically significant differences in thermal images between clothed and unclothed subjects (p > 0.05); (2) 15 m above ground level was proven to be the optimal height, as it showed the greatest contrast between the carcass heat signature and the background (p < 0.005). Our data suggested the potential window of detection of thermal signatures was detectable up to 7 days post-deposition. This could be an important guideline for the search and recovery teams for operational implementation in this tropical region.

Delay-Derivative/Distribution Dependent Stability and Stabilization Criteria for T–S Fuzzy Systems With Random Time-Varying Delay

This paper is concerned with the problems of stability and stabilization for Takagi-Sugeno(T-S) fuzzy systems with random time-varying delay. Since the stochastic nature of delay is considered, the original systems are transformed into equivalent new system models. Then, by borrowing the constant delay decomposition method, an appropriate Lyapunov-Krasovskii(L-K) functional is constructed. Based on the L-K functional, the variation range, the probabilities in intervals and the derivative of delay can be effectively utilized. And the reciprocally convex inequality is used to estimate the upper bound of the integral terms from the derivative of L-K functional. The new delay-derivative/distribution dependent stability and stabilization criteria are derived. Different from the previous works, the information of delay derivative is effectively utilized to analyze and design the systems with random time-varying delay for the first time. Moreover, if delay is a known time-varying function, less conservative stability and stabilization conditions can be obtained by the proposed delay decomposition method. Finally, the merits of the obtained stability and stabilization criteria are illustrated via several examples.

Design of High-speed Delay-FXLMS Hardware Architecture Based on FPGA

In order to improve the convergence and clock speed of DFxLMS adaptive filter, a hardware architecture of fine-grained retiming DFxLMS (HS-TF-RDFXLMS) filter in the form of hardware sharing transpose is proposed. Firstly, the architecture adopts delay decomposition algorithm to solve the problem that the convergence of filter decreases due to the increase of delay and output lag. Secondly, on the premise that the algorithm performance remains unchanged, the adaptive filter module and the secondary path module are transposed to further reduce the critical path to improve the clock speed of the system. The number of registers is reduced by optimizing circuit sub-module. Finally, the area/speed tradeoff of TF-RDFXLMS filter is realized by hardware sharing on the basis of constant critical path. Experimental results show that the convergence speed of the algorithm is 3.5 times that of DFxLMS algorithm, and the critical path is shortened by ([log2N]+1)TADD. The circuit structure of adaptive filter designed in this paper is realized by Xilinx Artix7 FPGA platform. The clock speed of HS-TF-RDFXLMS filter is reduced by 4.386% compared with TF-RDFXLMS filter. However, the resources of LUT and FF are saved by 10.964% and 28.322% respectively. The power consumption is 150.73 mW. This improves the performance of the system.

H∞ and Passive Fuzzy Control for Non-Linear Descriptor Systems with Time-Varying Delay and Sensor Faults

In this paper, the problem of reliable control design with mixed H∞ /passive performance is discussed for a class of Takagi–Sugeno TS fuzzy descriptor systems with time-varying delay, sensor failure, and randomly occurred non-linearity. Based on the Lyapunov theory, firstly, a less conservative admissible criterion is established by combining the delay decomposition and reciprocally convex approaches. Then, the attention is focused on the design of a reliable static output feedback (SOF) controller with mixed H∞ /passive performance requirements. The key merit of the paper is to propose a simple method to design such a controller since the system output is subject to probabilistic missing data and noise. Using the output vector as a state component, an augmented model is introduced, and sufficient conditions are derived to achieve the desired performance of the closed-loop system. In addition, the cone complementarity linearization (CCL) algorithm is provided to calculate the controller gains. At last, three numerical examples, including computer-simulated truck-trailer and ball and beam systems are given to show the efficacy of our proposed approach, compared with existing ones in the literature.

Delay optimization for ternary fixed polarity Reed–Muller circuits based on multilevel adaptive quantum genetic algorithm

Delay optimization has now emerged as an important optimization goal in logic synthesis. The delay optimization for ternary fixed polarity Reed–Muller (FPRM) circuits aims to find a ternary FPRM circuit with a minimum delay. Because the delay optimization for ternary FPRM circuits is a combinatorial optimization problem, in this paper, we first propose a multilevel adaptive quantum genetic algorithm (MAQGA), which divides individuals into three-level populations: high-level population, intermediate-level population, and low-level population and uses the proposed ternary quantum rotation gate, proposed ternary quantum correction gate, and proposed multi-operator adaptive mutation mechanism to make the three-level populations evolve. Moreover, based on the proposed delay decomposition strategy, we propose a delay optimization approach (DOA) for ternary FPRM circuits under the unit delay model, which searches for a ternary FPRM circuit with a minimum delay using the MAQGA. Experimental results demonstrated the effectiveness and superiority of the DOA in optimizing the delay of ternary FPRM circuits.

Stability of fractional neutral systems with time varying delay based on delay decomposition approach

Stability of fractional neutral systems with time varying delay based on delay decomposition approach

Stability Analysis of Real-Time Hybrid Simulation with Time-Varying Delay through a Delay Decomposition Approach

Stability of real-time hybrid simulation (RTHS) has attracted considerable attention given that actuator delay might destabilize the real-time test, especially when the compensation is not sufficient. Previous research by the authors explored the stability of RTHS with time-varying delay, but the derived stability criteria are relatively conservative due to the application of the Lyapunov-Krasovskii (L-K) theory. For overcoming such defect and pursuing a more accurate stability analysis, this study introduces a delay decomposition approach to reduce the conservatism of matrix inequality with convexity property. For both constant- and time-varying delay systems, the delay decomposition approach performed remarkably in stability analysis. Moreover, with the increase in number of decomposition, this approach can further improve the accuracy of analysis results and reduce its conservatism; however, the computational efforts will rise rapidly. Computational simulation verified the effectiveness of the delay decomposition approach especially for the physical substructure involving a small stiffness ratio.

Robust delay-dependent H∞ filtering for uncertain Takagi–Sugeno fuzzy neutral stochastic time-delay systems

This paper addresses the robust H∞ filter design problem for a class of uncertain fuzzy neutral stochastic system with time-delay through Takagi–Sugeno (T–S) fuzzy model. By constructing an augmented Lyapunov–Krasovskii functional, some novel delay-dependent stability criteria for uncertain fuzzy neutral stochastic system with time varying delay are obtained in terms of linear matrix inequalities. By using the integral inequality in the neutral stochastic setting combined with delay decomposition approach, the H∞ fuzzy filter is designed to guarantee the corresponding filtering error systems robustly asymptotically stable with a specified H∞ performance index. At last, two numerical examples are presented to show the less conservatism than the previous results.

EDOA: an efficient delay optimization approach for mixed-polarity Reed-Muller logic circuits under the unit delay model

Delay optimization has recently attracted significant attention. However, few studies have focused on the delay optimization of mixed-polarity Reed-Muller (MPRM) logic circuits. In this paper, we propose an efficient delay optimization approach (EDOA) for MPRM logic circuits under the unit delay model, which can derive an optimal MPRM logic circuit with minimum delay. First, the simplest MPRM expression with the fewest number of product terms is obtained using a novel Reed-Muller expression simplification approach (RMESA) considering don’t-care terms. Second, a minimum delay decomposition approach based on a Huffman tree construction algorithm is utilized on the simplest MPRM expression. Experimental results on MCNC benchmark circuits demonstrate that compared to the Berkeley SIS 1.2 and ABC, the EDOA can significantly reduce delay for most circuits. Furthermore, for a few circuits, while reducing delay, the EDOA incurs an area penalty.

Litter Traits of Native and Non-Native Tropical Trees Influence Soil Carbon Dynamics in Timber Plantations in Panama

Tropical reforestation initiatives are widely recognized as a key strategy for mitigating rising atmospheric CO2 concentrations. Although rapid tree growth in young secondary forests and plantations sequesters large amounts of carbon (C) in biomass, the choice of tree species for reforestation projects is crucial, as species identity and diversity affect microbial activity and soil C cycling via plant litter inputs. The decay rate of litter is largely determined by its chemical and physical properties, and trait complementarity of diverse litter mixtures can produce non-additive effects, which facilitate or delay decomposition. Furthermore, microbial communities may preferentially decompose litter from native tree species (homefield advantage). Hence, information on how different tree species influence soil carbon dynamics could inform reforestation efforts to maximize soil C storage. We established a decomposition experiment in Panama, Central America, using mesocosms and litterbags in monoculture plantations of native species (Dalbergia retusa Hemsl. and Terminalia amazonia J.F.Gmel., Exell) or teak (Tectona grandis L.f.) to assess the influence of different litter types and litter mixtures on soil C dynamics. We used reciprocal litter transplant experiments to assess the homefield advantage and litter mixtures to determine facilitative or antagonistic effects on decomposition rates and soil respiration in all plantation types. Although litter properties explained some of the variation in decomposition, the microclimate and soil properties in the plantations also played an important role. Microbial biomass C and litter decomposition were lower in Tectona than in the native plantations. We observed non-additive effects of mixtures with Tectona and Dalbergia litter on both decomposition and soil respiration, but the effect depended on plantation type. Further, there was a homefield disadvantage for soil respiration in Tectona and Terminalia plantations. Our results suggest that tree species diversity plays an important role in the resilience of tropical soils and that plantations with native tree species could help maintain key processes involved in soil carbon sequestration.

Novel synchronization conditions for time-varying delayed Lur’e system with parametric uncertainty

This paper investigates the synchronization stability conditions of uncertain chaotic Lur’e systems with time-varying delayed feedback control. In order to reduce the conservatism, we introduce a suitable Lyapunov–Krasovskii function with triple and quadruple integral terms. Based on some inequality properties, convex combination techniques and delay decomposition methods, we establish some novel synchronization conditions, which are given in terms of linear matrix inequalities (LMIs). Finally, numerical simulations examples demonstrate the effectiveness and advantages of our conclusions.

Delay-Dependent Stability Analysis of Modular Microgrid With Distributed Battery Power and SoC Consensus Tracking

The modular microgrid based on distributed battery storages is a simple and reliable power supply way for the islands. Modules are interconnected to the transmission network through the three-port converter. The three-port converter supplies the local ac bus voltage within the module and realizes the power exchange between the module and the transmission network. Distributed battery power and SoC consensus tracking model considering communication time delay is established on the leader-following multi-agent consensus tracking theory. By using the delay decomposition method, where the delay interval is discretized into two segmentations with an equal width, a modified Lyapunov-Krasovskii functional is constructed. A delay-dependent sufficient condition for the absolute stability of the battery power and SoC consensus tracking is derived in terms of linear matrix inequalities (LMIs) by using the free-weighting matrix method. The maximum delay margin corresponding to different controller parameters is calculated with the LMI toolbox of MATLAB. The case study is carried out based on the DongAo Island microgrid demonstration project. Simulations of battery power and SoC consensus tracking with constant time or time-varying delays verifies the effectiveness of the maximum delay margin determined by the stability criteria. Experiments reveal that the three-port converter can meet the requirements of the modular microgrid networking and operation control. The distributed battery power and SoC consensus tracking of the modular microgrid can be achieved when the communication time delay is less than the maximum delay margin.

Improved Reachable Set Bounding for Linear Neutral Systems with Disturbances via Triple Integral Functionals

This paper focuses on bound of reachable sets for linear neutral systems with bounded peak disturbances. To best of our knowledge, there were few results related to the ellipsoidal bound of reachable sets for linear neutral systems. By utilizing the Lyapunov-Krasovskii functional theory, delay decomposition technique, reciprocally convex method and free-weighting matrix approach, some new results expressed in terms of linear matrix inequalities are derived. Furthermore, triple integral functionals are introduced first time to derive bound of reachable sets for linear neutral systems. A tighter bound of the reachable set is obtained.

A Novel Stability Criterion of Lur’e Systems with Time-Varying Delay Based on Relaxed Conditions

This paper considers the absolute stability for Lur’e systems with time-varying delay and sector-bounded nonlinear. In this paper, a new relaxed condition based on delay decomposition approach is proposed. By using this technique and employing some inequality, the new delay-dependent stability criteria for Lur’e systems are derived in the form of linear matrix inequalities (LMIs). A numerical example is presented to show less conservatism of proposed methods compared with the previous.

Signal Priority Request Delay Modeling and Mitigation for Emergency Vehicles in Connected Vehicle Environment

Connected vehicle-based signal priority control is widely regarded as an advanced method for improving travel efficiency of an emergency vehicle when passing through intersections. However, the vehicle-to-everything (V2X) communication delay is a critical factor affecting the performance of signal request and has rarely been considered in existing studies. This paper conducted a comprehensive delay analysis of the preemption signal request and its influence on practical preemption control for the emergency vehicle. First of all, a general end-to-end delay decomposition model is formulated to analyze significant delay uncertainties from different sources. Then, a compensated distance strategy is adopted for cooperative preemption control to ensure the reliability of preemption control and minimize impacts on performance caused by communication delay. Based on the analysis of field data and numerical results, the proposed model is able to reveal characteristics of communication delay for multimodal traffic signal control with priority. The proposed communication delay compensation strategy shows clear benefits in improving the performance of signal preemption control priority for an emergency vehicle at intersections and therefore has potential to enhance V2X applications in a connected vehicle environment.

Stochastic stability for distributed delay neural networks via augmented Lyapunov–Krasovskii functionals

This paper is concerned with the analysis problem for the globally asymptotic stability of a class of stochastic neural networks with finite or infinite distributed delays. By using the delay decomposition idea, a novel augmented Lyapunov–Krasovskii functional containing double and triple integral terms is constructed, based on which and in combination with the Jensen integral inequalities, a less conservative stability condition is established for stochastic neural networks with infinite distributed delay by means of linear matrix inequalities. As for stochastic neural networks with finite distributed delay, the Wirtinger-based integral inequality is further introduced, together with the augmented Lyapunov–Krasovskii functional, to obtain a more effective stability condition. Finally, several numerical examples demonstrate that our proposed conditions improve typical existing ones.

Dual-side Event-triggered Output Feedback H∞ Control for NCS with Communication Delays

This paper studies the dual-side event-triggered output feedback H∞ control for networked control system with network-induced delays. Unlike continuous-time event-triggered mechanism (ETM) or state-dependent ETM, the discrete dual-side ETMs are firstly proposed by using plant output and controller output, respectively, which effectively reduce transmission rate of sampled data in both sensor-to-controller and controller-to-actuator channels. Then, the closed-loop system is modelled as a time-delay system, which characterizes effects of the dual-side ETMs and networked-induced delays in a unified framework. Based on the system model, asymptotic stability criterion satisfying H∞ performance is derived, and conservatism is reduced by the delay decomposition method and reciprocally convex approach. Moreover, a co-design scheme is presented to design the dual-side ETMs and controller simultaneously, which is more convenient than two-step design method requiring controllers to be given a priori. Finally, examples confirm effectiveness of the proposed method.

A generalized probability-interval-decomposition approach for stability analysis of T-S fuzzy systems with stochastic delays

Based on the generalized probability-interval-decomposition approach, the delay-dependent stability analysis for a class of T-S fuzzy systems with stochastic delays is investigated. The information of the probability distribution of stochastic delay is fully exploited and a series of sufficient stability criteria are obtained. A rigorous mathematical proof is provided that the conservatism of the proposed stability criteria can be reduced progressively by increasing the number of the probability interval. Based on this, a novel hierarchy of LMI conditions is established. It is rigorously proved that with the same decomposition of probability interval, the conservatism of the proposed stability criteria is less than the one obtained by time-varying delay decomposition approach. The computation burden of the proposed method is analyzed and compared with one of the time-varying delay decomposition approach. Finally, a numerical example is given to illustrate the validness and effectiveness of the proposed approach.

Non-fragile H&amp;infin; controller for combustion process in rocket motors

The aim of this paper is to analyse the problem of robust non-fragile H∞ controller for the combustion process in liquid propellant rocket motors chamber. Based on the delay decomposition approach, the whole delay interval is divided into two equidistant subintervals and a new Lyapunov-Krasovskii functional (LKF) which contains some triple-integral terms and augment terms is introduced on each interval. By using L-K stability theorem, integral inequality method together with free weighting matrix approach, a new delay-dependent bounded real lemma (BRL) is formulated. Then, by applying the BRL, non-fragile H∞ controller is formulated in terms of linear matrix inequalities (LMI), where no any parameter needs to be turned and apt to realisation. Finally, simulation results are given to illustrate that the designed controller has good robust and non-fragile performance.