Asymptotic reconstruction of the Fourier expansion of inputs of linear time-varying systems with applications

International audienceLinear time-varying systems driven by periodic input signals are ubiquitous in control systems. For various reasons, including disturbance rejection and diagnosis by analysis of the trajectories, estimation of their input signals is often desirable. In the present paper, we illustrate a recently proposed general method to solve such problems by an asymptotic reconstruction of the Fourier expansion of the unknown input signal along with several examples from the automotive engine industry, and with an oscillating water column retrieving wave energy

Anomalous spin-charge separation in a driven Hubbard system

Spin-charge separation (SCS) is a striking manifestation of strong correlations in low-dimensional quantum systems, whereby a fermion splits into separate spin and charge excitations that travel at different speeds. Here, we demonstrate that periodic driving enables control over SCS in a Hubbard system near half-filling. In one dimension, we predict analytically an exotic regime where charge travels slower than spin and can even become 'frozen', in agreement with numerical calculations. In two dimensions, the driving slows both charge and spin, and leads to complex interferences between single-particle and pair-hopping processes.Comment: arXiv admin note: text overlap with arXiv:2002.0231

Experimental control of Variable Cam Timing actuators

International audienceIn this paper, we propose a control scheme for the position of Variable Cam Timing (VCT) actuators. We take into account the observation by (Genç et al., 2001) that these actuators feature a significant nonlinearity, but we use a different approach. We perform a model reduction of mechanics, pressure, flows and balance equations. It serves to design an observer used in a motion planning strategy that is ultimately complemented by a tracking controller. Supportive vehicle experimental results are presented

Carbon-rich planet formation in a solar composition disk

The C--to--O ratio is a crucial determinant of the chemical properties of planets. The recent observation of WASP 12b, a giant planet with a C/O value larger than that estimated for its host star, poses a conundrum for understanding the origin of this elemental ratio in any given planetary system. In this paper, we propose a mechanism for enhancing the value of C/O in the disk through the transport and distribution of volatiles. We construct a model that computes the abundances of major C and O bearing volatiles under the influence of gas drag, sublimation, vapor diffusion, condensation and coagulation in a multi--iceline 1+1D protoplanetary disk. We find a gradual depletion in water and carbon monoxide vapors inside the water's iceline with carbon monoxide depleting slower than water. This effect increases the gaseous C/O and decreases the C/H ratio in this region to values similar to those found in WASP 12b's day side atmosphere. Giant planets whose envelopes were accreted inside the water's iceline should then display C/O values larger than those of their parent stars, making them members of the class of so-called ``carbon-rich planets''.Comment: 8 pages, 4 figures, accepted for publication Ap

Transient Burned Gas Rate Control on VVA equipped Diesel Engines

International audienceThis paper addresses the problem of cylinder burned gas rate transient control of VVA equipped Diesel engines. This problem is of importance for NOx emissions reduction. The proposed strategy coordinates existing low-level intake manifold burned gas rate and VVA controllers. To determine relevant control actions, a model of cylinder filling phenomenon is determined. It expresses, under the form of a discrete event dynamics, the behavior of the cylinder burned gas rate at intake valve closure. Interestingly, the model is invertible, thanks to its analytical nature. This property directly suggests an inverse formula that serves as control law. The strategy is efficient as is highlighted by experimental results obtained on a 1.6 L Diesel engine test bench. As a result, NOx emissions are largely diminished during transients

An evaluation framework for pre-distribution strategies of certificates in VANETs

Security and privacy in vehicular communication are expected to be ensured by the pervasive use of pseudonymous certificates and signed messages. The design and establishment of necessary public key infrastructure and hierarchies of cer- tificate authorities is ongoing in industry consortia, such as the Car-to-Car Communication Consortium. The privacy pre- serving dissemination of pseudonymous certificates is however still expected to be limited to single-hop exchanges between vehicles. This limitation to one-hop strategies might not be ideal, especially considering the importance of ensuring trustworthy stateless information exchange upon reception of the very first communication packets. We propose to investigate multi-hop pre- distribution strategies for certificates to significantly reduce this first encounter problem

Congestion-based Certificate Omission in VANETs

Telematic awareness of nearby vehicles is a basic foundation of electronic safety applications in Vehicular Ad hoc Networks (VANETs). This awareness is achieved by frequently broadcasting beacon messages to nearby vehicles that announce a vehicle's location and other data like heading and speed. Such safety-related beacons require strong integrity protection and high availability, two properties that are hard to combine because the communication and computation overhead introduced by security mechanisms affects reliability. This applies especially to the signatures and certificates needed for authentication. We propose a mechanism to reduce the communication overhead of secure safety beacons by adaptively omitting the inclusion of certificates in messages. In contrast to similar earlier proposals, we control the omission rate based on channel congestion. A simulation study underlines the advantages of the congestion-based certificate omission scheme compared to earlier approaches. Moreover, we show that the benefits of certificate omission outweigh the negative effect of cryptographically unverifiable beacons

Adaptive Backstepping Controller for Uncertain Systems With Unknown Input Time-Delay. Application to SI Engines

International audienceIn this paper, we study the equilibrium regulation of potentially unstable linear systems with an unknown input time-delay and unknown parameters in the plant. We extend recent results from the literature where such systems are treated using a backstepping approach applied to a distributed parameters system representation of the delay. We develop a local result, robust to delay errors and apply it for the control of the Air-Fuel Ratio in Spark Ignition engines. A proof of convergence is established for this particular example. Experimental results stress the relevance of the proposed control algorithm

Prediction-Based Stabilization of Linear Systems Subject to Input-Dependent Input Delay of Integral-Type

International audienceIn this paper, it is proved that a predictor-based feedback controller can effectively yield asymptotic convergence for a class of linear systems subject to input-dependent input delay. This class is characterized by the delay being implicitly related to past values of the input via an integral model. This situation is representative of systems where transport phenomena take place, as is frequent in the process industry. The sufficient conditions obtained for asymptotic stabilization bring a local result and require the magnitude of the feedback gain to be consistent with the initial conditions scale. Arguments of proof for this novel result include general Halanay inequalities for delay differential equations and build on recent advances of backstepping techniques for uncertain or varying delay systems

Cooperative home light: assessment of a security function for the automotive field

Crime and feeling of security are omnipresent and can be influenced by lighting conditions. However, lighting improvements are generally concentrated on street lighting. Meanwhile, a vast variety of new technologies, including innovative lighting systems and connected mobility, are entering into the automotive field. Hence, opportunities are not limited only to provide traffic improvements, entertainment features or driver assistance functions but also measures to tackle (vehicle-related) crime and to increase feeling of security. In this paper, we suggest a security function, namely the cooperative home light (CHL), which makes use of new technologies and has the potential to tackle crime as well as to increase drivers’ feeling of security. We also provide an overview of an implementation. However, because of the underlying challenges, the main focus of this paper is to assess the CHL. Therefore, we introduce our three-steps approach consisting of a transfer of related work, a customer survey and results from our proprietary simulation environment in order to assess the CHL