Control Power Consumption Research Articles

Modulation of nonlinear coupling on the synchronization induced by linear coupling

Based on the Lyapunov stability theory, the Lyapunov function in the form of exponential type is constructed. The four-variable Chen hyperchaotic model is investigated as an example. The reliability of a linear coupling-inudced synchronization of hyperchaotic system is proofed analytically. Furthermore, the modulation effect of nonlinear coupling on the synchronization induced by linear coupling is investigated. A statictical function is defined to evaulate the power consumption of controller according to the dimensionaless dynamical equations, the appropriate parameter region for synchronization due to the joint action of linear and nonlinear coupling, and the extensive numerical results confirm the correctress of the theoretical predication.

Power Efficient Variability Compensation Through Clustered Tunable Power-Gating

Power efficiency and variability, currently, are the main aspects of concern of nanometer-scale CMOS technology. Both issues have been widely studied and described in the literature, and various options for their independent management are available. Unfortunately, their exacerbation on sub-40 nm processes will require new design solutions for concurrent optimization. This paper moves towards this objective, and presents a new, fully-automated, design methodology, based on the Monitor and Control paradigm, able to improve the timing yield of a system making use of traditional power-gating (PG) as a knob for controlling power consumption and performance. In particular, the design and implementation of tunable-size sleep transistors is described, as well as a methodology for inserting them in a row-based layout. In order to keep under control both area and power overhead that come from the insertion of the sleep transistors, this paper also proposes a new strategy for clustering and power-gating only the timing critical cells. The experimental results are extremely promising. In fact, the proposed approach guarantees 100% of the timing yield with average leakage-power savings of about 29%.

A self-adaptive thermal switch array for rapid temperature stabilization under various thermal power inputs

A self-adaptive thermal switch array (TSA) based on actuation by low-melting-point alloy droplets is reported to stabilize the temperature of a heat-generating microelectromechanical system (MEMS) device at a predetermined range (i.e. the optimal working temperature of the device) with neither a control circuit nor electrical power consumption. When the temperature is below this range, the TSA stays off and works as a thermal insulator. Therefore, the MEMS device can quickly heat itself up to its optimal working temperature during startup. Once this temperature is reached, TSA is automatically turned on to increase the thermal conductance, working as an effective thermal spreader. As a result, the MEMS device tends to stay at its optimal working temperature without complex thermal management components and the associated parasitic power loss. A prototype TSA was fabricated and characterized to prove the concept. The stabilization temperatures under various power inputs have been studied both experimentally and theoretically. Under the increment of power input from 3.8 to 5.8 W, the temperature of the device increased only by 2.5 °C due to the stabilization effect of TSA.

Design and fabrication of synthetic air-jet micropump

In this paper, we propose a synthetic jet-type micropump for supplying air. Synthetic jet actuators usually include a small single pumping cavity, inlet/outlet channels, and a Lead zirconate titanate(PZT) membrane that exerts the pumping pressure. To determine the optimum design parameters of the air pump, a numerical analysis was carried out by varying its geometry. The optimized air pump was fabricated by replicating PDMS parts from silicon masters patterned by the deep RIE process. The size of the fabricated micropump was 16 × 13 × 3 mm3. In order to control the frequency of the PZT membrane and reduce the controller size and power consumption, an SP4423 microchip was used. At a pumping frequency of 80 Hz, a flow rate of 9.5 cc/min, pumping pressure of 438 Pa, and power consumption less than 0.15 mW were achieved.

An Improvement of Slotted CSMA/CA Algorithm in IEEE 802.15.4 Medium Access Layer

The standard of IEEE 802.15.4 is able to achieve low-power transmissions in low-rate and short-distance wireless personal area networks. It employs the slotted carrier sense multiple access with collision avoidance (CSMA/CA) for the contention mechanism. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. Sensor node performs backoff process immediately when the clear channel assessment (CCA) detecting busy channel. It may neglect the implicit information of CCA failed detection and further cause the redundant senses. This paper proposes an additional carrier sensing (ACS) algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanisms in original slotted CSMA/CA. An analytic model is developed to evaluate the performance of ACS algorithm. The analytical and simulation results demonstrate that the proposed scheme significantly improves the throughput, average medium access control delay and power consumption of CCA detecting.

MIMO Power Control for High-Density Servers in an Enclosure

Power control is becoming a key challenge for effectively operating a modern data center. In addition to reducing operating costs, precisely controlling power consumption is an essential way to avoid system failures caused by power capacity overload or overheating due to increasing high server density. Control-theoretic techniques have recently shown a lot of promise for power management because of their better control performance and theoretical guarantees on control accuracy and system stability. However, existing work oversimplifies the problem by controlling a single server independently from others. As a result, at the enclosure level where multiple high-density servers are correlated by common workloads and share common power supplies, power cannot be shared to improve application performance. In this paper, we propose an enclosure-level power controller that shifts power among servers based on their performance needs, while controlling the total power of the enclosure to be lower than a constraint. Our controller features a rigorous design based on an optimal Multi-Input-Multi-Output (MIMO) control theory. We present detailed control problem formulation and transformation to a standard constrained least-squares problem, as well as stability analysis in the face of significant workload variations. We then conduct extensive experiments on a physical testbed to compare our controller with three state-of-the-art controllers: a heuristic-based MIMO control solution, a Single-Input-Single-Output (SISO) control solution, and an improved SISO controller with simple power shifting among servers. Our empirical results demonstrate that our controller outperforms all the three baselines by having more accurate power control and up to 11.8 percent better benchmark performance.

A New MPPT Method for Low-Power Solar Energy Harvesting

This paper describes a new maximum-power-point-tracking (MPPT) method focused on low-power (<; 1 W) photovoltaic (PV) panels. The static and dynamic performance is theoretically analyzed, and design criteria are provided. A prototype was implemented with a 500-mW PV panel, a commercial boost converter, and low-power components for the MPPT controller. Laboratory measurements were performed to assess the effectiveness of the proposed method. Tracking efficiency was higher than 99.6%. The overall efficiency was higher than 92% for a PV panel power higher than 100 mW. This is, in part, feasible due to the low power consumption of the MPPT controller, which was kept lower than 350 μW. The time response of the tracking circuit was tested to be around 1 s. Field measurements showed energy gains higher than 10.3% with respect to a direct-coupled solution for an ambient temperature of 26°C. Higher gains are expected for lower temperatures.

Analysis and reduction of phase variations of variable gain amplifiers verified by CMOS implementation at C-band

Phase variations of variable gain cascode amplifiers are analysed and a method, which significantly reduces the phase variations versus gain is presented. The operation point current and the load of the variable gain transistors are stabilised by current weighting using dummy paths. The approach is verified by a fully integrated CMOS variable gain amplifier at C-band. A maximum gain of 18 dB with a 1 dB bandwidth of 5.2–5.7 GHz is measured. At 5.7 GHz and within a gain control range of 23 dB the absolute phase difference is reduced to a minimum of±4° yielding an improvement by a factor of 5 compared with simple cascode topologies. A total supply power of 9 mW is consumed. A very low phase variation has been achieved at comparable gain control range and power consumption for a variable gain amplifier in CMOS.

Optimal Server Allocation and Frequency Modulation on Multi-Core Based Server Clusters

Multi-core processing has been widely used in high-performance computing systems. Power reduction and energy conservation are important in these systems to minimize operating cost. Two main strategies exist for power management: Dynamic Voltage/Frequency Scaling (DV/FS) and server number controlling: Vary-On Vary-Off (VOVF). In this paper, the authors explore the benefits of DV/FS and VOVF and apply them in a multi-core based server cluster. An optimization problem is formulated to get the optimal resource scheduling strategy given a parallel workload. The presented optimization model provides controllable and quantitative power consumption with theoretically guaranteed service performance. The authors further study the overhead of the proposed scheme and provide a Double Control Periods (DCP) method to compensate the transition overhead. The power optimization model is evaluated via extensive simulations. It is also justified by the real workload data trace. The results prove the effectiveness and efficiency of the proposed model.

Power and performance control of soft real-time web server clusters

This paper presents a novel way to control power consumption and performance in a multi-tier server cluster designed for e-commerce applications. The requests submitted to these server systems have a soft real-time constraint, given that although some can miss a pre-defined deadline, the system can still meet an agreed upon performance level. Clusters of servers are extensively used nowadays and, with the steep increase in the total power consumption in these systems, economic and environmental problems have been raised. We present ways of decreasing power expenditure, and show the implementation of a SISO ( Single Input Single Output) controller that acts on the speed of all server nodes capable of dynamic voltage and frequency scaling (DVFS), with QoS ( Quality of Service) being the reference setpoint. For QoS, we use the request tardiness, defined as the ratio of the end-to-end response time to the deadline, rather than the usual metric that counts missed deadlines. We adjust the servers operating frequencies to guarantee that a pre-defined p-quantile of the tardiness probability distribution of the requests meet their deadlines. Doing so we can guarantee that the QoS will be statistically p. We test this technique in a prototype multi-tier cluster, using open software, commodity hardware, and a standardized e-commerce application to generate a workload close to that of the real world. The main contribution of this paper is to empirically show the robustness of the SISO controller, presenting a sensibility analysis of its parameters. Experimental results show that our implementation outperforms other published state-of-the-art cluster implementations.

Study on Additional Carrier Sensing for IEEE 802.15.4 Wireless Sensor Networks

Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the guise of low-rate and short-distance wireless personal area networks (WPANs). The slotted carrier sense multiple access with collision avoidance (CSMA/CA) is used for contention mechanism. Sensor nodes perform a backoff process as soon as the clear channel assessment (CCA) detects a busy channel. In doing so they may neglect the implicit information of the failed CCA detection and further cause the redundant sensing. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. This paper proposes an additional carrier sensing (ACS) algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanism for the original slotted CSMA/CA. An analytical Markov chain model is developed to evaluate the performance of the ACS algorithm. Both analytical and simulation results show that the proposed algorithm performs better than IEEE 802.15.4, which in turn significantly improves throughput, average medium access control (MAC) delay and power consumption of CCA detection.

Flow transfer mode (FTM) as universal switching method in electronic and photonic networks

Packetized networks have been introduced to take advantage of communication flexibility and to cope with resource utilization inefficiencies caused by bursty traffic flows. Since then the mere switching task of networking has evolved towards a nightmare of control efforts, an el dorado for processing wastage, a black hole for power consumption, a guaranteed market for buffer chips, and actually a step back in performance quality for interactive real-time communications, which always will remain the most precious communication form between humans. It is time to change that. A novel technique, called flow transfer mode (FTM), allows to establish a universal switching method that preserves all packetized merits of user flexibility and effectiveness in resource utilization, while achieving predictable and constant end-to-end delays, whenever strictly required. It drastically reduces control efforts, processing wastage, power consumption, buffer requirements, and performance deficiencies of current packetized networks, even when operating with the newest networking achievements. In brief, flow transfer mode is a highly dynamic layer-1 switching technology with layer-2 or layer-3 control for scheduling of both continuous or periodic interleaved streaming data flows as well as short flows consisting of a single packet or a burst of aggregated packets to the same network destination. Each flow is triggered by a preceding control unit that is transmitted in due time in advance. In this respect, it can be regarded as a generalization of optical burst switching.

Guest Editors' Introduction: Raising the Abstraction Level of Hardware Design

Design complexity is continually rising with the higher levels of integration implied by Moore's law. Functional complexity increases as more computation is added to SoCs and as more-complex applications are developed. Additional complexity is introduced by the need to control power consumption and to tackle challenges with respect to physical timing closure and process variations. To manage this complexity requires automation, letting designers focus on high-level design decisions that have the most effect in the implementation's quality. A higher level of hardware design abstraction also enables an effective exploration of software and hardware architectures, making high-level synthesis a cornerstone of electronic system-level design. This special issue features nine articles that the authors believe will generate interest in the use of high-level synthesis and its further development.

On chip tunable micro ring resonator actuated by electrowetting

We demonstrate a tunable on chip polymer waveguide micro ring resonator (MRR) device. The transmission spectrum and extinction ratio are controlled by electrowetting on dielectric (EWOD), via the application of voltage to a droplet. As a result the droplet covers a portion of the MRR waveguide and changes its effective refractive index. This method can be used for efficiently tuning a variety of on chip optical devices, as it offers high index contrast, electrical control and low power consumption.

Synthetic Jet 마이크로 에어펌프의 개발

This paper presents a micro air pump based on the synthetic jet to supply reactant at the cathode side for micro fuel cells. The synthetic jet is a zero mass flux device that converts electrical energy into the momentum. The synthetic jet actuation is usually generated by a traditional PZT-driven actuator, which consists of a small cylindrical cavity, orifices and PZT diaphragms. Therefore, it is very important that the design parameters are optimized because of the simple configuration. To design the synthetic jet micro air pump, a numerical analysis has been conducted for flow characteristics with respect to various geometries. From results of numerical analysis, the micro air pump has been fabricated by the PDMS replication process. The most important design factors of the micro air pump in micro fuel cells are the small size and low power consumption. To satisfy the design targets, we used SP4423 micro chip that is high voltage output DC-AC converter to control the PZT. The SP4423 micro chips can operate from power supply(or battery) and is capable of supplying up to 200V signals. So it is possible to make small size controller and low power consumption under 0.1W. The size of micro air pump was and the performance test was conducted. With a voltage of 3V at 800Hz, the air pump`s flow rate was 2.4cc/min and its power consumption was only 0.15W.

A Compact and Low Power Consumption Optical Switch Based on Microrings

A compact optical switch array based on microrings using a high-index-contrast waveguide is presented with excellent performance. The 84 optical switch matrix occupies just 103mm and its extinction ratio is greater than 30 dB at a low control power consumption of 0.1 W per unit cell. The drop loss is around 2 dB. This device is particularly suitable for applications as a tunable filter array and wavelength selective optical switch.

Activity-Based Computing

This month's Works in Progress department features six projects related to activity-based computing—a hovering information service for mobile devices, a method for analyzing spatio-temporal data to learn activity patterns, a conflict-resolution method for context-aware applications, pervasive middleware for a mobile environment, a novel sensor network for controlling power consumption, and a system to help end users visually design context-aware activity-based ubiquitous applications. This is part of a special issue on activity-based computing.

Design and modelling of a multi-standard fractional PLL in CMOS/SOI technology

This paper deals with the design of a fractional PLL for wireless multi-standard applications. This circuit has been produced using CMOS/SOI technology, with body voltage to control power consumption and phase noise performance. Five standards are covered by this structure: GSM (900MHz), DCS (1.8GHz), Bluetooth (2.45GHz) and 802.11a (5.8GHz). Based on multi-engine simulators, associated with a hierarchical models library, a virtual RF system platform, which allows designing complex SoCs, is also presented. The PLL, including digital and analogue parts, constitutes a very good benchmark to validate this platform.

High-precision control of the observation satellite with small power consumption

An unified method of the control, orientation and stabilization is proposed; the method allows an observation satellite (OS) to be brought in the sliding mode with a specified accuracy and in a required time to the necessary angular terminal position in the conditions of the limited indefinite external disturbances. The method minimizes power consumption for control. An approach for regulation of the frequency and amplitude of steady-state control oscillations is presented.

Hearing aid with performance-optimized power consumption for variable clock, supply voltage and DSP processing parameters

The invention relates to a hearing aid with optimized and controllable power consumption. The power consumption is controlled by varying the voltage level of the supply voltage and/or the frequency of the clock signal. Furthermore the invention relates to a method of optimizing the power consumption of a hearing aid, by calibrating its supply voltage and its clock frequency, and the relation between them, according to the production characteristics of the digital signal processor.