Flow Control Signals Research Articles

Steady flow control for a novel lattice hydrodynamic model with time delay based on discrete‐time system

This paper aims to investigate the influence of time delay effect and steady flow control strategy on traffic flow. Consider that the time delay in sensing flux information during the operation of traffic system is inevitable. Meanwhile, a new method is applied to model and analyse traffic system. A novel discrete‐time lattice hydrodynamic model considering time delay is introduced in this paper. Based on the proposed model with constant and varying time‐delay, the asymptotic stabilities are investigated and corresponding stable conditions are derived. The traffic flow evolution trend with and without time delay is conducted and compared by numerical simulations. Also, under the influence of different control gain conditions, density wave characteristics for traffic flow system with time delay are intuitively shown. The results indicate that time delay effect in sensing density and flux information can aggravate traffic congestion, and traffic congestion will be effectively relieved by considering steady flow control signal.

Mathematical Modeling with Friction of a SCARA Robot Driven by Pneumatic Semi-rotary Actuators

This article approaches the problem of the modeling of a SCARA (Selective Compliance Assembly Robot Arm) manipulator designed by two semi-rotating pneumatic servo-actuators in the presence of friction in view of the precise control for a future application of a non-linear controller. Even though pneumatic systems are widely used in industry, it is found that the robustness of pneumatic servo-positioning solutions is limited by the positioning accuracy of the system controllers, that is, these controllers require complete knowledge of the system because they depend on sophisticated algorithms which should contemplate the highly non-linear nature of the operation of the pneumatic system. As precise model of SCARA pneumatic driven robots are not found in the bibliography, present study deal with such task, being continuation of a modeling procedure executed for an isolated semi-rotary pneumatic actuator, where the dynamic relationship among the pressures in the semi-rotary actuator chambers, the rotational piston position and velocity, and the flow mass rate, was achieved. In that work, the friction was expressed through the LuGre model and curves of mass flow rate, pressures and control signal of the servovalve were obtained by means of experimental identification procedures. Therefore, current article uses the modeling of the same semi-rotary pneumatic actuator to consolidate a mathematical model of a SCARA manipulator consisting of two semi-rotary pneumatic actuators and a linear pneumatic actuator that will support the future development of non-linear controllers. Open loop validation was performed through comparisons between experimental and simulation results.

The Mesochronous Dual-Clock FIFO Buffer

To increase system composability and facilitate timing closure, fully synchronous clocking is replaced by more relaxed clocking schemes, such as mesochronous clocking. Under this regime, the modules at the two ends of a mesochronous interface receive the same clock signal, thus operating under the same clock frequency, but the edges of the arriving clock signals may exhibit an unknown phase relationship. In such cases, clock synchronization is needed when sending data across modules. In this brief, we present a novel mesochronous dual-clock first-input–first-output (FIFO) buffer that can handle both clock synchronization and temporary data storage, by synchronizing data implicitly through the explicit synchronization of only the flow-control signals. The proposed design can operate correctly even when the transmitter and the receiver are separated by a long link whose delay cannot fit within the target operating frequency. In such scenarios, the proposed mesochronous FIFO can be extended to support multicycle link delays in a modular manner and with minimal modifications to the baseline architecture. When compared with the other state-of-the-art dual-clock mesochronous FIFO designs, the new architecture is demonstrated to yield a substantially lower cost implementation.

NOCHI: Network-on-Chip with Hybrid Interconnect

As processor core counts increase, networks-on-chip (NoCs) are becoming an increasingly popular interconnection fabric due to their ability to supply high bandwidth. However, NoCs need to deliver this high bandwidth at low latencies, while keeping within a tight power envelope. In this paper, we present a novel NoC with hybrid interconnect that leverages multiple types of interconnects - –specically, conventional full-swing short-range wires for the datapath, in conjunction with low-swing, multi-drop wires with long range, ultra-low-latency communication for the flow control signals. We show how this proposed system can be used to overcome key limitations of express virtual channels (EVC), a recently proposed flow control technique that allows packets to bypass intermediate routers to simultaneously improve energy-delay-throughput. Our preliminary results show up to a 8.8% reduction in power and up to a 44% improvement in latency under heavy load compared to the original EVC design that only uses the conventional full-swing interconnects.

Adaptive Transmission Control based Secured Multimedia Data Traffic Distribution Scheme over Integrated Wireless Networks

Flow mobility distribution for mobile devices is essentially important for IP-based environments in order to efficiently manage the load of data traffic. For Heterogeneous hierarchical mobility management protocol, the load of traffic is concentrated on the mobility anchor point (MAP) for it acts as the central controller for all connecting mobile devices. Whenever, the MAP handoff is breached, the entire operation that goes through the MAP is compromised. This paper deals with the analysis of a secured distribution of traffic load within the MAP domain over hierarchical mobility management environments. The overview of hierarchical mobility management will be discussed as well as securing the flow control signaling scheme will be introduced in order to determine and ensure the optimized flow of traffic, considering the amount of traffic that every MAP handles.

Coordination and control for energy distribution in distributed grid networks: Theory and application to power dispatch problem

This paper presents a new framework considering decentralized energy coordination and generation, and flow control for supply–demand balance in distributed grid networks. Consensus schemes using only local information are employed to produce energy coordination, generation, and flow control signals. For the supply–demand balance, it is required to determine the amount of energy needed at each distributed resource. Also, due to the different generation capacities of each energy resource, coordination of energy flows among distributed energy resources is essentially required. Thus, this paper proposes a new framework which gives decentralized energy coordination scheme, generation, and flow control method considering these constraints based on distributed consensus algorithms. The proposed framework in this paper can be nicely utilized in energy dispatch or energy flow scheduling. Furthermore, it can be applied to various engineering problems including water irrigation systems, traffic networks, and building automation systems since it deals with attributed distribution and resource allocation in large scale distributed systems. Through illustrative examples, the effectiveness of the proposed approaches is illustrated. A possible application to power dispatch problem in the IEEE-14bus is also addressed for more detailed and realistic evaluation.

Finite element modelling of Coriolis mass flowmeters with arbitrary pipe geometry and unsteady flow conditions

The behaviour of Coriolis mass flowmeters (CMFs) with arbitrary pipe geometry is investigated in this paper regarding the effects of unsteady flow, geometry and damping. Timoshenko׳s beam theory, the finite element method (FEM), Mathworks Matlab and Simulink are used for creating a suitable model. Various physical quantities such as Coriolis, centrifugal and gravitational forces, mass inertia, mass flow, unsteady flow forces, damping and material parameters are considered to increase model precision. Stiffening effects due to fluid deflection are partly neglected in the model. The use of exact finite elements and model reduction via modal transformation results in fast and accurate numerical computation which corresponds well with experimental data. As a consequence, this approach allows further optimization of pipe geometries, actuation positions and concepts, actuation und flow control systems and signal processing concepts without co-simulation.

Low latency and efficient optical flow control for intra data center networks

We experimentally demonstrate a highly spectral efficient optical flow control technique for intra data center networks. A bi-directional system is implemented for generating flow control signal by reusing label wavelength and the transmission link within the same WDM channel. Dynamic operation shows high-quality flow control signal with 265 ns latency including 220 ns propagation delay and 500 mV amplitude with low input power and low bias current. Error free operation with 0.5 dB penalty for 40 Gb/s payload indicates that no distortion has been caused due the transmission of label and flow control signal.

Measurement and Analysis Possibilities of Pulse Wave Signals

This article deals with the implementation of wireless data transfer in biomedical applications concretely in photoplethysmography and pressure wave measurements. It deals with the application of a Bluetooth module for data transfer to the computer where further signal processing can be performed. The work describes a use of microcontroller serving for data flow control, communication and analog signal digitalization.

Next-generation integrated microfluidic circuits

This mini-review provides a brief overview of recent devices that use networks of elastomeric valves to minimize or eliminate the need for interconnections between microfluidic chips and external instruction lines that send flow control signals. Conventional microfluidic control mechanisms convey instruction signals in a parallel manner such that the number of instruction lines must increase as the number of independently operated valves increases. The devices described here circumvent this "tyranny of microfluidic interconnects" by the serial encoding of information to enable instruction of an arbitrary number of independent valves with a set number of control lines, or by the microfluidic circuit-embedded encoding of instructions to eliminate control lines altogether. Because the parallel instruction chips are the most historical and straightforward to design, they are still the most commonly used approach today. As requirements for instruction complexity, chip-to-chip communication, and real-time on-chip feedback flow control arise, the next generation of integrated microfluidic circuits will need to incorporate these latest interconnect flow control approaches.

A multi Gbit/s backplane for the RPC DAQ and L1 Trigger of the ATLAS Muon Spectrometer

The Read Out Driver (ROD) of the RPC detectors in the ATLAS Muon Spectrometer is a VME64x board designed to perform sub-event building for one of the 32 sectors in which the apparatus is divided. Each ROD receives data fragments from two companion boards placed in the adjacent VME slots. These two boards also send trigger data to the nearest slot, respectively at their right and left hand side. Due to the large amount of data to be transferred with a known latency, an auxiliary bus named RODbus has been designed and deployed in order to link the five boards.In this paper we present the logical and physical architecture of the RODbus, which implements multiple point-to-point LVDS links for high-speed data transfer and parallel TTL busses for commands, flags and flow-control signals. A prototype of the bus embedded into a VME64x 21-slot backplane has been recently developed together with HARTING, the firm which designed the connectors specified by the VME64x standard. We also discuss the test results on signal integrity, crosstalk and impedance profile made with Time Domain Reflectometry.

Feedback-based synchronization in system area networks for cluster computing

Many applications in cluster computing require QoS (quality of service) services. Since performance predictability is essential to provide QoS service, underlying systems must provide predictable performance guarantees. One way to ensure such guarantees from network subsystems is to generate global schedules from applications' network requests and to execute the local portion of the schedules at each network interface. To ensure accurate execution of the schedules, it is essential that a global time base must be maintained by local clocks at each network interface. The task of providing a single time base is called a synchronization problem and this paper addresses the problem for system area networks. To solve the synchronization problem, FM-QoS [K. Connelly (1999)] proposed a simple synchronization mechanism called FBS (feedback-based synchronization) which uses built-in flow control signals. This paper extends the basic notion of FM-QoS to a theoretical framework and generalizes it: 1) to identify a set of built-in network flow control signals for synchrony and to formalize it as a synchronizing schedule and 2) to analyze the synchronization precision of FBS in terms of flow control parameters. Based on generalization, two application classes are studied for a single switch network and a multiple switch network. For each class, a synchronizing schedule is proposed and its bounded skew is analyzed. Unlike FM-QoS, the synchronizing schedule is proven to minimize the bounded skew value for a single switch network. To understand the analysis results in practical networks, skew values are obtained with flow control parameters of Myrinet-2000. We observed that the maximum bounded skew of FBS is 5.79/spl mu/sec or less over all our experiments. Based on this result, we came to a conclusion that FBS was a feasible synchronization mechanism in system area networks.

Markov-Chain Modeling for Multicast Signaling Delay Analysis

Feedback signaling plays a key role in flow control because the traffic source relies on the signaling information to make correct and timely flow-control decisions. However, it is difficult to design an efficient signaling algorithm since a signaling message can tolerate neither error nor latency. Multicast flow-control signaling imposes two additional challenges: scalability and feedback synchronization. Previous research on multicast signaling has mainly focused on the development of algorithms without analyzing their delay performance. To remedy this deficiency, we have previously developed a binary-tree model and an independent-marking statistical model for multicast-signaling delay analysis. This paper considers a general scenario where the congestion markings at different links are dependent - a more accurate but complex case. Specifically, we develop a Markov-chain model defined by the link-marking state on each path in the multicast tree. The Markov chain can not only capture link-marking dependencies, but also yield a tractable analytical model. We also develop a Markov-chain dependency-degree model to evaluate all possible Markov-chain dependency degrees without any prior knowledge of them. Using the above two models, we derive the general probability distributions of each path becoming the multicast-tree bottleneck. Also derived are the first and second moments of multicast signaling delays. The proposed Markov chain is also shown to asymptotically reach an equilibrium, and its limiting distribution converges to the marginal link-marking probabilities when the Markov chain is irreducible. Applying the two models, we analyze and contrast the delay scalability of two representative multicast signaling protocols: Soft-Synchronization Protocol (SSP) and Hop-By-Hop (HBH) algorithms.

Wrapper-based bus implementation techniques for performance improvement and cost reduction

A low-cost wrapper-based bus implementation is described that performs well in system-on-chip (SOC) designs. Novel wrapper implementation techniques are used to create wrappers without embedded data buffers. The bus uses 1) a novel slave wrapper interface that supports flow control signals, 2) a write buffer switching technique for the master wrappers to achieve good performance at a small hardware cost, 3) a novel retry management technique called slave designated retry control (SDRC) to enable slow IP core connections and a livelock avoidance scheme using the SDRC technique, and 4) a novel bit-width conversion technique using data-width converters embedded in the bus multiplexers. A CPU-based SOC designed with the proposed bus showed that these techniques can increase throughput by about 14%, and reduce read and write latencies by about 16% and 11% compared to a conventional wrapper-based bus, when running a modeled average traffic pattern for this chip. The implemented results show that these techniques can reduce the hardware costs by 28% or 50% compared with two conventional wrapper-based conversion techniques. The chip is implemented using 0.15-/spl mu/m CMOS process technologies. The area for the on-chip bus is 3.3 mm/sup 2/ and the operation clock frequency is 200 MHz.

Delay analysis of feedback-synchronization signaling for multicast flow control

Feedback signaling plays a key role in flow control because the traffic source relies on the signaling information to make correct and timely flow-control decisions. Design of an efficient signaling algorithm is a challenging task since the signaling messages can tolerate neither error nor latency. Multicast flow-control signaling imposes two additional challenges: scalability and feedback synchronization. Previous research on multicast feedback-synchronization signaling has mainly focused on algorithm design and implementation. However, the delay properties of these algorithms are, despite their vital importance, neither well understood nor thoroughly studied. We develop both deterministic and statistical binary-tree models to study the delay performance of the multicast signaling algorithms. The deterministic model is used to derive the expressions of each path's feedback roundtrip time in a multicast tree, while the statistical model is employed to derive the general probability distributions of each path becoming the multicast-tree bottleneck. Using these models, we analyze and contrast the signaling delay scalability of two representative multicast signaling protocols - the soft-synchronization protocol (SSP) and the hop-by-hop (HBH) scheme - by deriving the first and second moments of multicast signaling delays. Also derived is the optimal flow-control update interval for SSP to minimize the multicast signaling delay.

A Comparison of Router Architectures for Virtual Cut-Through and Wormhole Switching in a NOW Environment

Most multicomputer interconnection networks use wormhole switching, leading to fast and compact routers. Current routers incorporate virtual channels and even fully adaptive routing. Networks of workstations (NOWs) inherited multicomputer technology. Most commercial routers designed for NOWs implement wormhole switching. However, wormhole switching is not well suited for NOWs. The long wires required in this environment lead to large buffers to prevent buffer overflow during flow control signaling. Moreover, wire length is limited by buffer size. Virtual cut-through (VCT) achieves a higher throughput than wormhole switching. However, buffer requirements and packetizing overhead prevented its widespread use in multicomputers. Nevertheless, wormhole and VCT switching require similar buffer capacity in NOWs. Moreover, some messaging layers such as Illinois Fast Messages (FM) and BIP split messages into packets for increased performance. Therefore, the traditional disadvantages of VCT switching disappear in NOWs. In this paper, we show that VCT routers can be simpler than wormhole routers, while still achieving the advantages of using virtual channels and adaptive routing. We also propose a fully adaptive routing algorithm for VCT switching in a NOW environment. Moreover, we show that VCT routers outperform wormhole routers in a NOW environment at a lower cost. Also, VCT routers require buffer capacity independent of wire length, making them suitable for networks of workstations.

Integration of synchronous and asynchronous traffic on the MetaRing and its performance study

The main motivation for developing the MetaRing architecture was to increase the throughput of a ring-based local area network beyond its single link capacity by means of spatial bandwidth reuse. We describe and evaluate a protocol for integrating two types of traffic on the MetaRing architecture. Synchronous (reserved or real-time) traffic which is periodic and requires a connection set-up and will have guaranteed bandwidth and bounded delay, and asynchronous or bursty traffic with no real-time constraints that can use the remainder of the bandwidth in a fair manner. The integration mechanism is functionally equivalent to the timed-token function in FDDI, which is a shared media ring protocol. Simulation results are also presented to show the effects of the fairness and flow control signals on the performance of the network.