Self-tuning of disk input–output in operating systems

The final publication is available via http://dx.doi.org/10.1016/j.jss.2011.07.030One of the most difficult and hard to learn tasks in computer system management is tuning the kernel parameters in order to get the maximum performance. Traditionally, this tuning has been set using either fixed configurations or the subjective administrator's criteria. The main bottleneck among the subsystems managed by the operating systems is disk input/output (I/O). An evolutionary module has been developed to perform the tuning of this subsystem automatically, using an adaptive and dynamic approach. Any computer change, both at the hardware level, and due to the nature of the workload itself, will make our module adapt automatically and in a transparent way. Thus, system administrators are released from this kind of task and able to achieve some optimal performances adapted to the framework of each of their systems. The experiment made shows a productivity increase in 88.2% of cases and an average improvement of 29.63% with regard to the default configuration of the Linux operating system. A decrease of the average latency was achieved in 77.5% of cases and the mean decrease in the request processing time of I/O was 12.79%

Robust multivariable predictive control: how can it be applied to industrial test stands ?

To cope with recent technological evolutions of air conditioning systems for aircraft, the French Aeronautical Test Center built a new test stand for certification at ground level. The constraints specified by the industrial users of the process seemed antagonistic for many reasons. First, the controller had to be implemented on an industrial automaton, not adaptable to modern algorithms. Then the specified dynamic performances were very demanding, especially taking into account the wide operating ranges of the process. Finally, the proposed controller had to be easy for nonspecialist users to handle. Thus, the control design and implementation steps had to be conducted considering both theoretical and technical aspects. This finally led to the development of a new multivariable predictive controller, called alpha-MPC, whose main characteristic is the introduction of an extra tuning parameter alpha that has enhanced the overall control robustness. In particular, the H1-norm of the sensitivity functions can be significantly reduced by tuning this single new parameter. It turns out to be a simple but efficient way to improve the robustness of the initial algorithm. The other classical tuning parameters are still physically meaningful, as is usual with predictive techniques. The initial results are very promising and this controller has already been adopted by the industrial users as the basis of the control part for future developments of the test stand

Full-range birefringence control with piezoelectric MEMS-based metasurfaces

Dynamic polarization control is crucial for emerging highly integrated photonic systems with diverse metasurfaces being explored for its realization, but efficient, fast, and broadband operation remains a cumbersome challenge. While efficient optical metasurfaces (OMSs) involving liquid crystals suffer from inherently slow responses, other OMS realizations are limited either in the operating wavelength range (due to resonances involved) or in the range of birefringence tuning. Capitalizing on our development of piezoelectric micro-electro-mechanical system (MEMS) based dynamic OMSs, we demonstrate reflective MEMS-OMS dynamic wave plates (DWPs) with high polarization conversion efficiencies (∼75%), broadband operation (∼100 nm near the operating wavelength of 800 nm), fast responses (<0.4 milliseconds) and full-range birefringence control that enables completely encircling the Poincaré sphere along trajectories determined by the incident light polarization and DWP orientation. Demonstrated complete electrical control over light polarization opens new avenues in further integration and miniaturization of optical networks and systems.publishedVersio

A PLL control for self-tuning of parallel wireless power transfer receivers utilizing switch-mode gyrator emulated inductors

In multiple receivers wireless power transfer (WPT) systems, it is preferable to retune the resonant frequency of every receiver to the transmitter operating frequency in front of frequency mismatches. This paper discusses a proposal for electronic tuning for WPT receivers by means of a variable active switch-mode inductance. The proposed method benefits from the gyrator concept to emulate a variable inductance. Instead of the conventional approach of linear amplifier based implementation of a gyrator, a switch-mode gyrator circuit is exploited for more efficient operation. Additionally, a PLL-like control is presented to enable self-tuning for the receiver resonant tank. Furthermore, a design-space characterization for the system dynamic behavior has been discussed to show the control robustness and the instabilities (including slow-scale and fast-scale chaotic instabilities) it may undergo.Peer ReviewedPostprint (published version

A Gray-Box Dynamic Modeling Method for Variable Speed Direct Expansion Systems

In this paper, a gray-box dynamic modeling approach for variable-speed direct-expansion systems is presented. The overall approach incorporates a multi-stage training procedure that consists of 1) identification of component sub-models from quasi-steady-state performance data, 2) system model integration with estimation of refrigerant charge and 3) fine tuning of thermal capacitances of the evaporator and condenser to capture the system dynamic responses. Compared to traditional physics-based models, the proposed modeling approach has advantages including reduced engineering efforts in the model development phase, improved computational efficiency and reduced uncertainties. The modeling method was applied to a 3-ton variable-speed heat pump and proved to be capable of accurately capturing the system transient behaviors over a wide range of operating conditions

A software controlled voltage tuning system using multi-purpose ring oscillators

This paper presents a novel software driven voltage tuning method that utilises multi-purpose Ring Oscillators (ROs) to provide process variation and environment sensitive energy reductions. The proposed technique enables voltage tuning based on the observed frequency of the ROs, taken as a representation of the device speed and used to estimate a safe minimum operating voltage at a given core frequency. A conservative linear relationship between RO frequency and silicon speed is used to approximate the critical path of the processor. Using a multi-purpose RO not specifically implemented for critical path characterisation is a unique approach to voltage tuning. The parameters governing the relationship between RO and silicon speed are obtained through the testing of a sample of processors from different wafer regions. These parameters can then be used on all devices of that model. The tuning method and software control framework is demonstrated on a sample of XMOS XS1-U8A-64 embedded microprocessors, yielding a dynamic power saving of up to 25% with no performance reduction and no negative impact on the real-time constraints of the embedded software running on the processor

Design principles for riboswitch function

Scientific and technological advances that enable the tuning of integrated regulatory components to match network and system requirements are critical to reliably control the function of biological systems. RNA provides a promising building block for the construction of tunable regulatory components based on its rich regulatory capacity and our current understanding of the sequence–function relationship. One prominent example of RNA-based regulatory components is riboswitches, genetic elements that mediate ligand control of gene expression through diverse regulatory mechanisms. While characterization of natural and synthetic riboswitches has revealed that riboswitch function can be modulated through sequence alteration, no quantitative frameworks exist to investigate or guide riboswitch tuning. Here, we combined mathematical modeling and experimental approaches to investigate the relationship between riboswitch function and performance. Model results demonstrated that the competition between reversible and irreversible rate constants dictates performance for different regulatory mechanisms. We also found that practical system restrictions, such as an upper limit on ligand concentration, can significantly alter the requirements for riboswitch performance, necessitating alternative tuning strategies. Previous experimental data for natural and synthetic riboswitches as well as experiments conducted in this work support model predictions. From our results, we developed a set of general design principles for synthetic riboswitches. Our results also provide a foundation from which to investigate how natural riboswitches are tuned to meet systems-level regulatory demands

A cascaded brushless doubly fed induction generator for wind energy applications based on direct power control

This paper proposes a direct power control (DPC) strategy for cascaded brushless doubly fed induction generator (CBDFIG), which eliminates the slip rings and brushes in conventional DFIG wind turbine systems and features quick dynamic response and excellent steady state performance. Prior methods for controlling CBDFIG are based on vector control (VC), which is complicated and requires much tuning work and machine parameters. Appropriate decoupling and fine PI tuning are mandatory to obtain good performance over the entire operating range. Furthermore, there are few papers regarding the grid synchronization issue of CBDFIG. This paper firstly analyzes the influence of each voltage vector on active/reactive powers and then proposes a unified switching table for both grid-connected operation and grid synchronization process. The effectiveness of the developed DPC method for CBDFIG is confirmed by the presented simulation results. © 2011 IEEE

Generating Information-Diverse Microwave Speckle Patterns Inside a Room at a Single Frequency With a Dynamic Metasurface Aperture

We demonstrate that dynamic metasurface apertures (DMAs) are capable of generating a multitude of highly uncorrelated speckle patterns in a typical residential environment at a single frequency. We use a DMA implemented as an electrically-large cavity excited by a single port and loaded with many individually-addressable tunable metamaterial radiators. We placed such a DMA in one corner of a plywood-walled L-shape room transmitting microwave signals at 19 GHz as we changed the tuning states of the metamaterial radiators. In another corner, in the non-line-of-sight of the DMA, we conducted a scan of the field generated by the DMA. For comparison, we also performed a similar test where the DMA was replaced by a simple dipole antenna with fixed pattern but generating a signal that spanned 19-24 GHz. Using singular value decomposition of the scanned data, we demonstrate that the DMA can generate a multitude of highly uncorrelated speckle patterns at a single frequency. In contrast, a dipole antenna with a fixed pattern can only generate such a highly uncorrelated set of patterns when operating over a large bandwidth. The experimental results of this paper suggest that DMAs can be used to capture a diversity of information at a single frequency which can be used for single frequency computational imaging systems, NLOS motion detection, gesture recognition systems, and more

Robust control of room temperature and relative humidity using advanced nonlinear inverse dynamics and evolutionary optimisation

A robust controller is developed, using advanced nonlinear inverse dynamics (NID) controller design and genetic algorithm optimisation, for room temperature control. The performance is evaluated through application to a single zone dynamic building model. The proposed controller produces superior performance when compared to the NID controller optimised with a simple optimisation algorithm, and classical PID control commonly used in the buildings industry. An improved level of thermal comfort is achieved, due to fast and accurate tracking of the setpoints, and energy consumption is shown to be reduced, which in turn means carbon emissions are reduced