A networks-on-chip architecture design space exploration – The LIB

Many on-chip network circuit and architecture techniques are incompatible with modern design flows, making them unsuitable for use in systems-on-chip. This paper presents a networks-on-chip (NoC) architecture design space exploration method for multi-processor systems-on-chip architecture. The NoC architecture design space is designed with a Layer-Interactive-Building block (LIB) methodology that is divided into three layers: application layer, link/network layer, and physical layer. The suggested LIB design paradigmatic philosophy provides modular building block structure in both hardware and software and the protocols for their interconnection in the three architecture layers. Using LIB the designer can easily select these building blocks to build application-specific NoCs to meet different application requirements such as media, graphic, software radio and communication network applications. The LIB provides the NoC building blocks, architecture interacting systems-on-chip components, the programming models and application mapping strategies. The LIB can be used as a complementary library and tools for future on-chip interconnection network design.     

NoC synthesis flow for customized domain specific multiprocessor systems-on-chip

The growing complexity of customizable single-chip multiprocessors is requiring communication resources that can only be provided by a highly-scalable communication infrastructure. This trend is exemplified by the growing number of network-on-chip (NoC) architectures that have been proposed recently for system-on-chip (SoC) integration. Developing NoC-based systems tailored to a particular application domain is crucial for achieving high-performance, energy-efficient customized solutions. The effectiveness of this approach largely depends on the availability of an ad hoc design methodology that, starting from a high-level application specification, derives an optimized NoC configuration with respect to different design objectives and instantiates the selected application specific on-chip micronetwork. Automatic execution of these design steps is highly desirable to increase SoC design productivity. This work illustrates a complete synthesis flow, called Netchip, for customized NoC architectures, that partitions the development work into major steps (topology mapping, selection, and generation) and provides proper tools for their automatic execution (SUNMAP, xpipescompiler). The entire flow leverages the flexibility of a fully reusable and scalable network components library called xpipes, consisting of highly-parameterizable network building blocks (network interface, switches, switch-to-switch links) that are design-time tunable and composable to achieve arbitrary topologies and customized domain-specific NoC architectures. Several experimental case studies are presented In the work, showing the powerful design space exploration capabilities of the proposed methodology and tools.     

Infinite horizon MPC with non-minimal state space feedback

In the MPC literature, stability is usually assured under the assumption that the state is measured. Since the closed-loop system may be nonlinear because of the constraints, it is not possible to apply the separation principle to prove global stability for the output feedback case. It is well known that, a nonlinear closed-loop system with the state estimated via an exponentially converging observer combined with a state feedback controller can be unstable even when the controller is stable.One alternative to overcome the state estimation problem is to adopt a non-minimal state space model, in which the states are represented by measured past inputs and outputs [P.C. Young, M.A. Behzadi, C.L. Wang, A. Chotai, Direct digital and adaptative control by input–output, state variable feedback pole assignment, International Journal of Control 46 (1987) 1867–1881; C. Wang, P.C. Young, Direct digital control by input–output, state variable feedback: theoretical background, International Journal of Control 47 (1988) 97–109]. In this case, no observer is needed since the state variables can be directly measured. However, an important disadvantage of this approach is that the realigned model is not of minimal order, which makes the infinite horizon approach to obtain nominal stability difficult to apply. Here, we propose a method to properly formulate an infinite horizon MPC based on the output-realigned model, which avoids the use of an observer and guarantees the closed loop stability. The simulation results show that, besides providing closed-loop stability for systems with integrating and stable modes, the proposed controller may have a better performance than those MPC controllers that make use of an observer to estimate the current states.     

基于Internet的遥操作系统带观测器的反馈控制

通常遥操作系统主、从机械手间存在通信时延,影响了系统的稳定性和操作性能.在基于Internet的遥操作系统中,时延是时变的,对系统的影响尤为剧烈.为了解决这个问题,在环境模型未知的条件下,首先提出在本地控制端用主手状态、预测的从手状态及接触力设计反馈控制器;接着用时间前向观测器预测从机械手的状态,并将时延变化率建模为系统不确定参数,最终得到稳定性和透明性条件.仿真结果表明了该方法的有效性.     

支持动态可重构片上系统的高效通信模型

针对片上网络通信延迟大、不能有效支持动态可重构等问题,提出一种新的片上通信模型GNLB。该模型在网络通信的基础上引入局部通信的思想,采用网络DMA通信机制,并利用网络接口对通信的控制,实现对动态可重构的控制。实验结果表明,基于GNLB构架的系统比基于总线和Mesh结构的系统在性能上分别提升了25％和14％,在硬件资源消耗上分别节省了15．87％和30．15％。     

Linear and nonlinear state-space controllers for magnetic levitation

The problem of precisely controlling (within sensor resolution) the height of a steel ball above the ground by levitating it against the force of gravity using an electromagnet is considered. The state variables used to model the system are the ball's position below the magnet, the ball's speed and the current in the electromagnet. Two state-space controllers are compared in terms of their performance in controlling the ball's position. The first controller is based on feedback linearization where a nonlinear state-space transformation along with nonlinear state feedback is used to linearize the system exactly. A linear controller is then used on the resulting system to control the ball's position. As a direct measurement of ball speed is not available, a nonlinear observer with linear error dynamics is used to estimate the speed. The second controller is a standard linear state feedback controller whose design is based on a linear model found by perturbing the nonlinear system model about an operating point. A linear observer is used to estimate the ball's velocity. Experimental results are presented to compare the effectiveness of the two controllers in terms of their ability to respond to step inputs and to track sinusoidal reference trajectories.     

Output feedback control of networked systems

This paper considers the problem of control of networked systems via output feedback. The controller consists of two parts: a state observer that estimates plant state from the output when it is available via the communication network, and a model of the plant that is used to generate a control signal when the plant output is not available from the network. Necessary and sufficient conditions for the exponential stability of the closed loop system are derived in terms of the networked dwell time and the system parameters. The results suggest simple procedures for designing the output feedback controller proposed. Numerical simulations show the feasibility and efficiency of the proposed methods.     

Observer-based predictive controller design with network-enhanced time-delay compensation

State feedback control is very attractive due to the precise computation of the gain matrix, but the implementation of a state feedback controller is possible only when all state variables are directly measurable. This condition is almost impossible to accomplish due to the excess number of required sensors or unavailability of states for measurement in most of the practical situations. Hence, the need for an estimator or observer is obvious to estimate all the state variables by observing the input and the output of the controlled system. As such, the goal of this paper is to provide a control design methodology based on a Luenberger observer design that can assure the closed-loop performances of a vehicle drivetrain with backlash, while compensating the network-enhanced time-varying delays. This goal is achieved in a sequential manner: firstly, a piecewise linear model of two inertias drivetrain, which takes into consideration the backlash nonlinearity and the network-enhanced time-varying delay effects is derived; then, a Luenberger observer which estimates the state variables is synthesized and the robust full state-feedback predictive controller based on flexible control Lyapunov functions is designed to explicitly take into account the bounds of the disturbances caused by time-varying delays and to guarantee also the input-to-state stability of the system in a non-conservative way. The full state-feedback predictive control strategy based on the Luenberger observer design was experimentally tested on a vehicle drivetrain emulator controlled through controller area network, with the aim of minimizing the backlash effects while compensating the network-enhanced delays.     

Output Feedback Control of Surge and Rotating Stall in Axial Compressors

Active control has been widely studied to expand the stable operating range of axial flow compressors in aero‐engines.In this paper, a nonlinear active state feedback controller is proposed first based on bifurcation analysis results of MG model.Then by taking pressure ratio as output parameter, a state observer is designed to estimate the compressor's flow coefficient. An output feedback controller is thus established by combining the observer with the state feedback controller.Finally, digital simulation shows that the proposed output feedback controller not only eliminates the hysteresis loop associated with rotating stall and emergence of surge, but also extends the stable operating range of axial flow compressors effectively.Furthermore, being flexible in using pressure transducer and throttle valve as sensor and actuator respectively, which have been equipped in common engines, the proposed controller has good applicability.     

一类线性时变系统的输出反馈控制

基于线性时不变系统能控能观标准型变换及非线性系统高增益观测器方法,本文研究了一类线性时变系统 的输出反馈控制问题. 通过引入时变的状态变量坐标变换,分别设计了线性时变系统的状态反馈控制器、状态观测器以及基于 状态观测器的输出反馈控制器. 进一步地,本文分别证明了观测器动态误差是渐近收敛于零的,而状态反馈控制器以及输出反馈控制器可以 保证闭环系统的渐近稳定性.     

线性系统的动态输出反馈最优扰动抑制

首先通过求解Riccati方程和Sylvester方程,推导出前馈反馈最优扰动抑制控制律．然后构建了能同时预估状态和扰动的降维观测器,解决了前馈控制的物理不可实现问题．进而结合降维观测器和前馈反馈最优控制律,提出了一种动态输出反馈扰动抑制控制器的设计算法．最后通过仿真实例表明本文提出的控制算法的可行性．     

Robust near-optimal output feedback control of non-linear systems

This work proposes a robust near-optimal non-linear output feedback controller design for a broad class of non-linear systems with time-varying bounded uncertain variables. Both vanishing and non-vanishing uncertainties are considered. Under the assumptions of input-to-state stable (ISS) inverse dynamics and vanishing uncertainty, a robust dynamic output feedback controller is constructed through combination of a high-gain observer with a robust optimal state feedback controller synthesized via Lyapunov's direct method and the inverse optimal approach. The controller enforces exponential stability and robust asymptotic output tracking with arbitrary degree of attenuation of the effect of the uncertain variables on the output of the closed-loop system, for initial conditions and uncertainty in arbitrarily large compact sets, provided that the observer gain is sufficiently large. Utilizing the inverse optimal control approach and singular perturbation techniques, the controller is shown to be near-optimal in the sense that its performance can be made arbitrarily close to the optimal performance of the robust optimal state feedback controller on the infinite time-interval by selecting the observer gain to be sufficiently large. For systems with non-vanishing uncertainties, the same controller is shown to ensure boundedness of the states, uncertainty attenuation and near-optimality on a finite time-interval. The developed controller is successfully applied to a chemical reactor example.     

A survey of routing algorithm for mesh Network-on-Chip

With the rapid development of semiconductor industry, the number of cores integrated on chip increases quickly, which brings tough challenges such as bandwidth, scalability and power into on-chip interconnection. Under such background, Network-on-Chip (NoC) is proposed and gradually replacing the traditional on-chip interconnections such as sharing bus and crossbar. For the convenience of physical layout, mesh is the most used topology in NoC design. Routing algorithm, which decides the paths of packets, has significant impact on the latency and throughput of network. Thus routing algorithm plays a vital role in a wellperformed network. This study mainly focuses on the routing algorithms of mesh NoC. By whether taking network information into consideration in routing decision, routing algorithms of NoC can be roughly classified into oblivious routing and adaptive routing. Oblivious routing costs less without adaptiveness while adaptive routing is on the contrary. To combine the advantages of oblivious and adaptive routing algorithm, half-adaptive algorithms were proposed. In this paper, the concepts, taxonomy and features of routing algorithms of NoC are introduced. Then the importance of routing algorithms in mesh NoC is highlighted, and representative routing algorithms with respective features are reviewed and summarized. Finally, we try to shed light upon the future work of NoC routing algorithms.     

Application of deterministic and stochastic Petri-Nets for performance modeling of NoC architectures

The design of appropriate communication architectures for complex Systems-on-Chip (SoC) is a challenging task. One promising alternative to solve these problems are Networks-on-Chip (NoCs). Recently, the application of deterministic and stochastic Petri-Nets (DSPNs) to model on-chip communication has been proven to be an attractive method to evaluate and explore different communication aspects. In this contribution the modeling of basic NoC communication scenarios featuring different processor cores, network topologies and communication schemes is presented. In order to provide a testbed for the verification of modeling results a state-of-the-art FPGA-platform has been utilized. This platform allows to instantiate a soft-core processor network which can be adapted in terms of communication network topologies and communication schemes. It will be shown that DSPN modeling yields good communication performance prediction results at low modeling effort. Different DSPN modeling aspects in terms of accuracy and computational effort are discussed.     

严格反馈非线性系统的自适应神经网络输出反馈控制

基于非线性反馈函数,文章设计神经网络状态观测器,解决一类非线性系统的输出反馈控制问题.非线性反馈神经网络观测器在系统存在不确定性函数的情况下实时估计系统状态.利用所获得的状态信号,设计了自适应神经网络动态面控制器,同时保证了闭环系统的稳定性和所有信号的有界性.通过调节设计参数的取值能够达到期望的闭环跟踪性能.数值仿真表明,所设计的状态观测器不需要对原系统做状态变换,能够克服输出反馈滑模控制器带来的抖震问题.     

基于观测器的受扰多项式系统H∞输出跟踪控制

考虑一类受到外部扰动影响的多项式系统在状态不完全可测情况下的H_∞输出跟踪控制问题.首先,综合前馈-反馈复合控制思想,设计基于观测器的输出跟踪控制器,其中反馈镇定控制器用于保证闭环系统稳定,前馈补偿控制器用以实现对参考模型输出信号的跟踪;然后,提出具有输出反馈结构的跟踪控制方法,其优势在于实现了分离原则,可单独设计观测器和控制器,降低计算复杂度;接着,利用依赖全状态的齐次多项式Lyapunov函数导出使得闭环系统渐近稳定且满足H_∞跟踪性能的充分条件,借助多项式平方和凸优化技术可直接求得相应的观测器和控制器;最后,通过数值仿真实例验证所提出设计方法的有效性和优越性.     

混合悬浮系统恒定气隙控制策略研究

本文对混合悬浮系统精确的数学模型进行了分析,分别对传统的PID直接反馈控制器和带状态观测器的状态反馈控制器进行了设计和比较,仿真结果表明,这两种控制器都能够使悬浮系统达到稳定,但是后者可以解决气隙速度信号估算的难题.     

Multi-hop communications on wireless network-on-chip using optimized phased-array antennas

Network-on-Chip (NoC) as a promising design approach for on-chip interconnect fabrics could overcome the energy as well as synchronization challenges of the conventional interconnects in the gigascale System-on-Chips (SoC). The advantages of communication performance of traditional wired NoC will no longer be continued by the future technology scaling. Packets that travel between distant nodes of a large scale wired on-chip network significantly suffer from energy dissipation and latency due to the routing overhead at each hop. According to the International Technology Roadmap for Semiconductors annual report, the RFCMOS characteristics will be steadily improved by technology scaling. As the operating frequency of RF devices increases, the size of Si integrated antenna will decrease and it is feasible to employ them as a revolutionary interconnect for intra-chip wireless communications. In this paper, we focus on physical requirements and design challenges of wireless NoC. It is demonstrated that employing an optimum-radiation phased array antenna and multihop communications will increase the reliability of on-chip wireless links by several orders of magnitude using a limited power budget less than 0.1 pJ/bit.     

遥操作系统基于观测器的预测控制

在遥操作系统中需要主、从机械手间进行通信,但通信通道中存在较大的通讯时延,这会降低系统操作性能,甚至会使系统不稳定.为了解决这个问题,首先建立系统的状态空间模型,接着提出用时间前向观测器预测从机械手状态,并结合力、位置和速度反馈消除或减小时延对系统影响.系统反馈参数可方便地通过线性矩阵不等式求解.该方法能使系统渐近稳定而且具有良好的透明性.仿真结果表明该方法是有效的.     

分数阶非线性多智能体系统的一致性研究

研究固定拓扑结构下的分数阶非线性多智能体系统协调控制的动力学模型问题。由于实际多智能体系统中,系统的状态变量难以全部测量,为了克服这一困难,利用状态观测器对系统状态进行重构并基于重构状态进行状态反馈。利用分数阶Lyapunov稳定性理论,证明了当反馈增益矩阵满足一定的线性矩阵不等式（LMI）条件时,系统中的智能体最终趋于所给定的目标状态。最后利用分数阶微积分的预估-校正算法进行数值仿真验证了理论分析的有效性和可行性。