A New finite sum inequality for delay-dependent H∞ control of discrete-time delay systems

This paper is concerned with the problem ofdelay-dependent H∞ control for linear discrete-time systems with time-varying delay. A new finite sum inequality is first established to derive a delay-dependent condition, underwhich the resulting closed-loop system is asymptoticallys table (internally stable) with a prescribed H∞ attenuation level via a memoryless state feedback. Then, an iterative algorithm involving convex optimization is proposed to obtain a suboptimal H∞ controller. Finally, a numerical example is iven to show the effectiveness of the proposed method

Further results on stability and stabilisation of linear systems with state and input delays

This article concerns the stability and stabilisation of a linear system with both state and input delays. First, the combination of an augmented Lyapunov functional and the free-weighting-matrix technique yields a new delay-independent stability criterion that includes the widely used one as a special case. This criterion is then extended to a new delay-dependent stability criterion by employing an integral inequality. Based on that, a stabilisation approach to design a state feedback controller is presented that requires no parameter tuning, as is needed with some existing methods. Finally, numerical examples illustrate that the method is effective and is an improvement over existing ones

Delay-dependent H∞ control of linear discrete-time systems with an interval-like time-varying delay

The free-weighting-matrix approach is developed to study the H control of linear discrete-time systems with an interval-like time-varying delay. First, a delay- and range-dependent criterion for a given H performance is derived. Second, a memoryless H state-feedback controller is designed based on a performance analysis. Finally, two numerical examples demonstrate the effectiveness of the proposed method and show that both the upper bound and range of an interval-like time-varying delay affect the stability and/or H performance of a system

Delay-dependent stabilization of linear systems with time-varying state and input delays

The integral-inequality method is a new way of tackling the delay-dependent stabilization problem for a linear system with time-varying state and input delays: ẋ(t)=Ax(t)+A1x(t-h1(t))+B1u(t)+B2u(t-h2(t)). In this paper, a new integral inequality for quadratic terms is first established. Then, it is used to obtain a new state- and input-delay-dependent criterion that ensures the stability of the closed-loop system with a memoryless state feedback controller. Finally, some numerical examples are presented to demonstrate that control systems designed based on the criterion are effective, even though neither (A,B1) nor (A+A1,B1) is stabilizable

A New integral inequality approach to delay dependent robust H∞ control

A design method for robust H∞ control of an uncertain linear system with a time-varying state delay is proposed. First, an integral inequality that we recently obtained is employed to establish a new delay-dependent bounded real lemma for a system with a time-varying delay. The lemma uses neither a model transformation nor a bounding technique for cross terms. Then, the lemma is used in combination with a matrix decomposition method to derive delay-dependent conditions for the existence of robust H∞ control based on linear matrix inequalities. Finally, some numerical examples are giving to demonstrate the validity of the method

An energy efficient and runtime-aware framework for distributed stream computing systems

Task scheduling in distributed stream computing systems is an NP-complete problem. Current scheduling schemes usually have a pause or slow start process due to the fluctuation of input data stream, which affects the performance stability, especially the high throughput and low latency goals. In addition, idle compute nodes at runtime may result in large idle load energy consumption. To address these problems, we propose an energy efficient and runtime-aware framework (Er-Stream). This paper thoroughly discusses the framework from the following aspects: (1) The communication between real-time data streaming tasks is investigated; stream application, resource and energy consumption are modeled to formalize the scheduling problem. (2) After an initial topology is submitted to the cluster, task pairs with high communication cost are processed on the same compute node through a lightweight task partitioning strategy, minimizing the communication cost between nodes and avoiding frequent triggering of runtime scheduling. (3) At runtime, reliable task migration is performed based on node communication and resource usage, which in turn helps the dynamic adjustment of the node energy consumption. (4) Metrics including latency, throughput, resource load and energy consumption are evaluated in a real distributed stream computing environment. With a comprehensive evaluation of variable-rate input scenarios, the proposed Er-Stream system provides promising improvements on throughput, latency and energy consumption compared to the existing Storm's scheduling strategies

A state lossless scheduling strategy in distributed stream computing systems

Stateful scheduling is of critical importance for the performance of a distributed stream computing system. In such a system, inappropriate task deployment lowers the resource utilization of cluster and introduces more communication between compute nodes. Also an online adjustment to task deployment scheme suffers slow state recovery during task restart. To address these issues, we propose a state lossless scheduling strategy (Sl-Stream) to optimize the task deployment and state recovery process. This paper discusses this strategy from the following aspects: (1) A stream application model and a resource model are constructed, together with the formalization of problems including subgraph partitioning, task deployment and stateful scheduling. (2) A multi-factor topology partitioning method is proposed using a quantum particle swarm algorithm. The assignment between tasks and nodes is optimized using a bipartite graph minimum matching algorithm. (3) A hierarchical local topology migration is performed when an online scheduling is triggered, which ensures the processing sustainability of data streams. (4) A fragment loss-tolerant jerasure tool is used to divide the state data into fragments and periodically save them in upstream vertex instances, which ensures the available fragments be able to reconstruct the whole state in parallel. (5) Metrics including latency, throughput and state recovery time are evaluated in a real distributed stream computing environment. With a comprehensive evaluation of variable-rate input scenarios, the proposed Sl-Stream system provides promising improvements on throughput, latency and state recovery time compared to the existing Storm's scheduling strategies

Liquid flow spinning mass-manufactured paraffin cored yarn for thermal management and ultra-high protection

Thermal management and ultra-high protection textiles are critical for polar scientists, astronauts and firefighters. Phase change materials (PCMs) effectively retard huge thermal changes, and thermal damage by absorbing or releasing heat during phase transition. However, due to the materials and engineering challenges inherent in PCMs based textiles, commercial PCMs usually suffer with high rigidity, no-breath-ability, easy leakage and abrasion, limiting their potential applications. Herein, we proposed a mass-producible liquid flow spinning (LFS) method, in which molten paraffin is poured into continuous hollow silicon tubes and then wrapped by staple fibers to form paraffin-coated yarns (PCYs) on a friction spinning frame. The obtained PCYs showed enhanced mechanical properties (break strength of 7.80 N, wear resistance of 2000 cycles) due to the novel core-sheath yarn structure. Besides, thanks to the high melting enthalpy (60.967 J/g) of PCYs, the yarns showed the excellent temperature regulating effect. A double-sided joint PCYs fabric (PCYF) is fabricated to study the PCYs performance further, results show that the PCYF can withstand 10,000 cycles of abrasion without breakage and PCMs leakage. Furthermore, owing to the much gaps provided by the stretch fibers and interweaving points, the fabric exhibits good breathability. In particular, compared with commercial PCMs based textiles, our PCYF is superior in thermal protection performance (9 °C lower). The fireproof performance is also excellent as our PCYF can withstand flame temperatures higher than 1142 °C. The PCYs production method provided here could pave the way for human thermal protection textiles