pinecone/core-2020-05-10-deduplication huggingface dataset:
Optimized look-ahead tree policies: a bridge between look-ahead tree policies and direct policy search

Direct policy search (DPS) and look-ahead tree (LT) policies are two popular techniques for solving difficult sequential decision-making problems. They both are simple to implement, widely applicable without making strong assumptions on the structure of the problem, and capable of producing high performance control policies. However, computationally both of them are, each in their own way, very expensive. DPS can require huge offline resources (effort required to obtain the policy) to first select an appropriate space of parameterized policies that works well for the targeted problem, and then to determine the best values of the parameters via global optimization. LT policies do not require any offline resources; however, they typically require huge online resources (effort required to calculate the best decision at each step) in order to grow trees of sufficient depth. In this paper, we propose optimized look-ahead trees (OLT), a model-based policy learning scheme that lies at the intersection of DPS and LT. In OLT, the control policy is represented indirectly through an algorithm that at each decision step develops, as in LT using a model of the dynamics, a small look-ahead tree until a prespecified online budget is exhausted. Unlike LT, the development of the tree is not driven by a generic heuristic; rather, the heuristic is optimized for the target problem and implemented as a parameterized node scoring function learned offline via DPS. We experimentally compare OLT with pure DPS and pure LT variants on optimal control benchmark domains. The results show that the LT-based representation is a versatile way of compactly representing policies in a DPS scheme (which results in OLT being easier to tune and having lower offline complexity than pure DPS); while at the same time, DPS helps to significantly reduce the size of the look-ahead trees that are required to take high-quality decisions (which results in OLT having lower online complexity than pure LT). Moreover, OLT produces overall better performing policies than pure DPS and pure LT and also results in policies that are robust with respect to perturbations of the initial conditions.Peer reviewe
Global adaptive linear control of the permanent-magnet synchronous motor

International audienceWe contribute with a linear time-varying controller for the permanent magnet synchronous motor. We solve the open problem of speed-tracking control by measuring only stator currents and the rotor angular positions, under parametric uncertainty. Integral action is used to compensate for the effects of the unknown load-torque and adaptation is employed to estimate the unknown parameters. In the case that parameters are known (except for the load) we show that the origin of the closed-loop system is uniformly globally exponentially stable. For the case of unknown parameters we prove uniform global asymptotic stability hence, we establish parametric convergence. In contrast to other adaptive control schemes for electrical machines, we use a reduced-order adaptive controller. Indeed, adaptation is used only for the electrical dynamics equations. Moreover, not surprisingly, the closed-loop system has a structure well-studied in adaptive-control literature. Performance is illustrated in a numerical settin
Set-membership parity space approach for fault detection in linear uncertain dynamic systems

In this paper, a set-membership parity space approach for linear uncertain dynamic systems is proposed. First, a set of parity relations derived from the parity space approach is obtained by means of a transformation derived from the system characteristic polynomial. As a result of this transformation, parity relations can be expressed in regressor form. On the one hand, this facilitates the parameter estimation of those relations using a zonotopic set-membership algorithm. On the other hand, fault detection is then based on checking, at every sample time, the non-existence of a parameter value in the parameter uncertainty set such that the model is consistent with all the system measurements. The proposed approach is applied to two examples: a first illustrative case study based on a two-tank system and a more realistic case study based on the wind turbine fault detection and isolation benchmark in order to evaluate its effectivenessPeer ReviewedPostprint (published version
Leak localization in drinking water distribution networks using structured residuals

In this paper, a new model-based approach to leakage localization in drinking water distribution networks is proposed. In particular, a method for generating a set of structured residuals for water distribution networks systems is presented. Non-linear static equations are typically used in the modeling of such systems. Unfortunately, these non-linearities prevent explicit solutions and thus the subsequent analytical expressions of the residuals are not feasible. For this reason, the residual computation procedure presented here uses a numerical solver based on an enhanced Newton-Raphson algorithm. Moreover, because the water distribution networks usually present a high degree of interconnection between nodes, good leak isolability properties can easily be obtained by applying the proposed residual generation method. Nevertheless, not fully leak detection and isolation can always be achieved, thus a methodology for the analysis of leak diagnosis is also presented in this paper. To show the applicability and the potential of the proposed approach, the structured residual generators are tested on a real water network model and compared with another existing method based on directional residuals. Finally, the results of the two methods are combined in order to obtain the best of both methods.Postprint (author's final draft
Interval-based fast fault detection and identification applied to radio-navigation multipath

International audienceDetection and identification of faulty measurements like multipath is of prime importance for radio-navigation. A method based on interval analysis and constraint propagation is presented in this paper and applied to GPS positioning. This method is able to detect and identify erroneous measurements in real-time simultaneously with the computation of the positioning domain. With bounded-error measurements (GPS pseudoranges on visible satellites here), fault-detection is guaranteed not to trigger false alarms. A q-relaxed robust estimation method is studied. By the use of a breadth-first exploration strategy and of measurement consistency counters, the algorithm can promptly signal a detected fault during the set-inversion process. It can also be stopped at any time of the evaluation, and can instantly return the solution subpaving and the list of identified erroneous measurements. We demonstrate than the method is able to handle simultaneous faults as long as they are fewer than the degree of relaxation. The method has been evaluated with real GPS pseudodistances in an urban environment with a low-cost high-sensitivity GPS receiver providing numerous faulty multipath measurements and we report experiments. As the application of this method deals with road vehicles, a 3-D map of the drivable space has also been used to constrain the vehicle location to improve the performance of the method
Continuous higher order sliding mode control with adaptation of air breathing hypersonic missile

This is the peer reviewed version of the following article: Yu, P., Shtessel, Y., and Edwards, C. (2016) Continuous higher order sliding mode control with adaptation of air breathing hypersonic missile. International Journal of Adaptive Control and Signal Processing, which has been published in final form at 10.1002/acs.2664. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving: http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms}Hypersonic missile control in the terminal phase is addressed using continuous higher order sliding mode (AHOSM) control with adaptation. The AHOSM self-tuning controller is proposed and studied. The double-layer adaptive algorithm is based on equivalent control concepts and ensures non-overestimation of the control gain to help mitigates control chattering. The proposed continuous AHOSM control is validated via simulations of a hypersonic missile in the terminal phase. The robustness and high accuracy output tracking in the presence of matched and unmatched external disturbances and missile model uncertainties is demonstrate
Adaptive sliding mode observation in a network of dynamical systems

This paper considers the problem of reconstructing state information in all the nodes of a complex network of dynamical systems. The individual nodes comprise a known linear part and unknown but bounded uncertainties in certain channels of the system. A supervisory adaptive sliding mode observer conﬁguration is proposed for estimating the states. A linear matrix inequality (LMI) approach is suggested to synthesise the gains of the sliding mode observer. Although deployed centrally to estimate all the states of the complex network, the design process depends only on the dynamics of an individual node of the network. The methodology is demonstrated by considering a network of Chua oscillators
Robust hybrid estimation and rejection of multi-frequency signals

We consider the problem of output regulation for LTI systems in the presence of unknown exosystems. The knowledge about the multi-frequency signals exosystem consists in the maximum number of frequencies and their maximal value. The control scheme relies on two main components: an estimation algorithm, to reconstruct the signal generated by the exosystem, and a controller, to enforce the output regulation property to the closed-loop system. To tackle the first task, we propose a hybrid observer for the estimation of the (possibly piece-wise continuous) number and values of the frequencies contained in the exogenous signal. The hybrid observer is particularly appealing for numerical implementations, and it is combined with a self-tuning algorithm of the free parameters (gains), thus improving its performance even in case of noisy measurements. Semi-global exponential convergence of the estimation error is provided. As far as the second task is concerned, a robust hybrid regulator is designed for practical rejection of the multi-frequency disturbance signal acting on the plant. The result is achieved by exploiting the frequencies estimated by the hybrid observer. The effectiveness of the proposed control scheme is shown by means of numerical simulations
Fast bias-constrained optimal FIR filtering for time-invariant state space models

This paper combines the finite impulse response filtering with the Kalman structure (predictor/corrector) and proposes a fast iterative bias-constrained optimal finite impulse response filtering algorithm for linear discrete time-invariant models. In order to provide filtering without any requirement of the initial state, the property of unbiasedness is employed. We first derive the optimal finite impulse response filter constrained by unbiasedness in the batch form and then find its fast iterative form for finite-horizon and full-horizon computations. The corresponding mean square error is also given in the batch and iterative forms. Extensive simulations are provided to investigate the trade-off with the Kalman filter. We show that the proposed algorithm has much higher immunity against errors in the noise covariances and better robustness against temporary model uncertainties. The full-horizon filter operates almost as fast as the Kalman filter, and its estimate converges with time to the Kalman estimate
Combined state and parameter estimation for Hammerstein systems with time-delay using the Kalman filtering

This paper discusses the state and parameter estimation problem for a class of Hammerstein state space systems with time-delay. Both the process noise and the measurement noise are considered in the system. Based on the observable canonical state space form and the key term separation, a pseudo-linear regressive identification model is obtained. For the unknown states in the information vector, the Kalman filter is used to search for the optimal state estimates. A Kalman-filter based least squares iterative and a recursive least squares algorithms are proposed. Extending the information vector to include the latest information terms which are missed for the time-delay, the Kalman-filter based recursive extended least squares algorithm is derived to obtain the estimates of the unknown time-delay, parameters and states. The numerical simulation results are given to illustrate the effectiveness of the proposed algorithms
Issues in the design of switched linear systems: a benchmark study

In this paper we present a tutorial overview of some of the issues that arise in the design of switched linear control systems. Particular emphasis is given to issues relating to stability and control system realisation. A benchmark regulation problem is then presented. This problem is most naturally solved by means of a switched control design. The challenge to the community is to design a control system that meets the required performance specifications and permits the application of rigorous analysis techniques. A simple design solution is presented and the limitations of currently available analysis techniques are illustrated with reference to this example
Redundant wavelet processing on the half-axis with applications to signal denoising with small delays: Theory and experiments

International audienceA wavelet transform on the negative half real axis is developed using an average-interpolation scheme. This transform is redundant and can be used to perform causal wavelet processing, such as on-line signal denoising, without delay. Nonetheless, in practice some boundary effects occur and thus a small amount of delay is required to reduce them. The effect of this delay is studied using a numerical example of a signal with large noise and sharp transients. It is shown that the delay required to obtain acceptable denoising levels is decreased by using the proposed redundant transform instead of a non-redundant one. We also present results from the experimental implementation of the proposed algorithm for the denoising of a feedback signal during the control of a three-phase permanent-magnet synchronous brushless DC motor
Sensor fault detection and isolation for nonlinear systems based on a sliding mode observer

This is the peer reviewed version of the following article: Yan, X.-G. and Edwards, C. (2007), Sensor fault detection and isolation for nonlinear systems based on a sliding mode observer. Int. J. Adapt. Control Signal Process., 21: 657–673. doi: 10.1002/acs.967, which has been published in final form at http://dx.doi.org/10.1002/acs.967. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.In this paper, a sensor fault detection and isolation scheme for nonlinear systems is considered. A nonlinear diffeomorphism is introduced to explore the system structure and a simple filter is presented to 'transform' the sensor fault into a pseudo-actuator fault scenario. A sliding mode observer is designed to reconstruct the sensor fault precisely if the system does not experience any uncertainty, and to estimate the sensor fault when uncertainty exists. The reconstruction and estimation signals are based only on available information and thus can be implemented online. Finally, a mass-spring system is used to illustrate the approach. Copyright ©2007 John Wiley & Sons, Ltd
SMC framework in motion control systems

Design of a motion control system should take into account both the unconstrained motion performed without interaction with environment or another system, and the constrained motion where the system is in contact with environment or has certain functional interactions with another system. In this paper control systems design approach, based on siding mode methods, that allows selection of control for generic tasks as trajectory and/or force tracking as well as for systems that require maintaining some functional relation - like bilateral or multilateral systems, establishment of virtual relation among mobile robots or control of haptic systems - is presented. It is shown that all basic motion control problems - trajectory tracking, force control, hybrid position/force control scheme and the impedance control - can be treated in the same way while avoiding the structural change of the controller and guaranteeing stable behaviour of the system. In order to show applicability of the proposed techniques simulation and experimental results for high precision systems in microsystems assembly tasks and bilateral control systems are presented
Ageing in suburbia : designing for demographic change in Australia and New Zealand

In the next half-century, Australia's population of people aged over 65 is set to almost double. As a consequence, there is an urgent need in both Australia and New Zealand, where older people value their independence, for housing that fully supports them in their own suburban homes. With only a handful of models in place, Mark Taylor, Professor of Architecture at the University of Newcastle, Australia, and Laurie Buys, a Professor in the School of Design at Queensland University of Technology in Brisbane, have tracked down some promising precedents for suburban living in adapted homes and within community-based shared housing
Imagined community and networked hyperlocal publics

What is the place of both immediate and mediated information in forming publics and sustaining communities? And what can past communication practices teach us in our digitally hyperconnected age? With reference to the work of philosophers, sociologists and theorists including Hannah Arendt, Jurgen Habermas, Keith Hampton and Barry Wellman, cultural researcher John Bingham-Hall reflects on the nature of place, and highlights the phatic properties of online platforms such as Southeast London's Brockley Central blog that seek to reinforce local identity
Using Synthetic Biology to Engineer Spatial Patterns

Synthetic biology has emerged as a multidisciplinary field that provides new tools and approaches to address longstanding problems in biology. It integrates knowledge from biology, engineering, mathematics, and biophysics to build—rather than to simply observe and perturb—biological systems that emulate natural counterparts or display novel properties. The interface between synthetic and developmental biology has greatly benefitted both fields and allowed to address questions that would remain challenging with classical approaches due to the intrinsic complexity and essentiality of developmental processes. This Progress Report provides an overview of how synthetic biology can help to understand a process that is crucial for the development of multicellular organisms: pattern formation. It reviews the major mechanisms of genetically encoded synthetic systems that have been engineered to establish spatial patterns at the population level. Limitations, challenges, applications, and potential opportunities of synthetic pattern formation are also discussed
Photostimulation for in vitro optogenetics with high power blue organic light-emitting diodes

Funding: Leverhulme Trust (RPG-2017-231), the EPSRC NSF-CBET lead agency agreement (EP/R010595/1, 1706207), the DARPA NESD programme (N66001-17-C-4012) and the RS Macdonald Charitable Trust. C.M. acknowledges funding by the European Commission through a Marie Sklodowska-Curie Individual Fellowship (703387). Y. L. Deng acknowledges support from the Chinese Scholarship Council (CSC).Optogenetics, photostimulation of neural tissues rendered sensitive to light, is widely used in neuroscience to modulate the electrical excitability of neurons. For effective optical excitation of neurons, light wavelength and power density must fit with the expression levels and biophysical properties of the genetically encoded light‐sensitive ion channels used to confer light sensitivity on cells—most commonly, channelrhodopsins (ChRs). As light sources, organic light‐emitting diodes (OLEDs) offer attractive properties for miniaturized implantable devices for in vivo optical stimulation, but they do not yet operate routinely at the optical powers required for optogenetics. Here, OLEDs with doped charge transport layers are demonstrated that deliver blue light with good stability over millions of pulses, at powers sufficient to activate the ChR, CheRiff when expressed in cultured primary neurons, allowing live cell imaging of neural activity with the red genetically encoded calcium indicator, jRCaMP1a. Intracellular calcium responses scale with the radiant flux of OLED emission, when varied through changes in the current density, number of pulses, frequency, and pulse width delivered to the devices. The reported optimization and characterization of high‐power OLEDs are foundational for the development of miniaturized OLEDs with thin‐layer encapsulation on bioimplantable devices to allow single‐cell activation in vivo.Publisher PDFPeer reviewe
A New Reactive Atom Plasma Technology (RAPT) for Precision Machining: the
Etching of ULE® Surface

Results on reactive atom plasma etching performed on ULE® (Corning Ultra Low
Expansion) glass samples at atmospheric pressure are presented for the first
time. A reactive atomic plasma technology (RAPT®), has been developed by RAPT
Industries and employed for the finishing of optical surfaces. An atmospheric
pressure argon inductively coupled plasma (ICP) excites a reactive gas injected
through its centre. The plume of hot neutral excited species reacts at the
substrate yielding controlled and repeatable trenches. In the case of ULE a
material removal (up to 0.55 mm3/s) is obtained without pre-heating the samples.
Among the factors influencing the results, an increase in gas concentration at
the same power does not change the sample temperature, indicating that thermo-
chemical effects do not influence the removal rates. Due to the plasma
constructive constrains, increasing the gas concentration is more practical and
of wider effect than increasing the power. The benefits of the process are
illustrated and the extension of the technology to large optical surfaces
discuss
Epoxy-based fibre reinforced nanocomposites

The modification of epoxy resins with nanoparticles could endow the materials
with some superior properties such as broadening of the glass transition
temperatures, modest increases in the glassy modulus, low dielectric constant,
and significant increases in key mechanical properties. In the last 15 years,
some studies have shown the potential improvement in properties and performances
of fibre reinforced polymer matrix materials in which nano and micro-scale
particles were incorporated. From the existing literature, considerable effort
has been given to the synthesis and processing of these unique polymers, but
relatively little work has focused on the fibre reinforced epoxy composites. The
purpose of this work, therefore, is to review the available literature in epoxy-
fibre reinforced composites manufactured using carbon nanotubes, carbon
nanofibre and nanoclays for reinforcement