Real‐time hybrid control of electrohydraulic active suspension

Electrohydraulic actuators are an attractive choice for active suspension, because these systems provide a high power‐to‐weight ratio. However, their dynamics are highly nonlinear. In addition, the use of one simple controller for both position and force is complicated, because there is a compromise between them in the case of active suspension. Most existing controllers do not efficiently fulfill the requirements, because only one state variable is considered. In this paper, we address these problems by developing a new hybrid controller for both position and force and implementing it in a real‐time test bench. Our goal is to control the vertical position of the passenger seat while tracking the force transmitted to passengers and keeping it within tolerable and comfortable limits. Therefore, the proposed controller is a combination of two controllers. Its flexible structure redirects the control signal to control the proper controlled state variable. The real‐time results of the newly designed hybrid controller are compared with those obtained using a classical proportional integral derivative controller, because this is the most widely used controller in the industry. As expected, the proposed controller demonstrates better performance in real‐time operation. Copyright © 2017 John Wiley & Sons, Ltd.     

Incremental Branching Programs

We propose a new model of restricted branching programs specific to solving GEN problems, which we call incremental branching programs. We show that syntactic incremental branching programs capture previously studied models of computation for the problem GEN, namely marking machines (Cook, S.A. in J. Comput. Syst. Sci. 9(3):308–316, 1974) and Poon’s extension (Proc. of the 34th IEEE Symp. on the Foundations of Computer Science, pp. 218–227, 1993) of jumping automata on graphs (Cook, S.A., Rackoff, C.W. in SIAM J. Comput. 9:636–652, 1980). We then prove exponential size lower bounds for our syntactic incremental model, and for some other variants of branching program computation for GEN. We further show that nondeterministic syntactic incremental branching programs are provably stronger than their deterministic counterpart when solving a natural NL-complete GEN sub-problem. It remains open if syntactic incremental branching programs are as powerful as unrestricted branching programs for GEN problems. A preliminary version of this paper appears as (Gál, A., Koucky, M., McKenzie, P., Incremental branching programs, in Proc. of the 2006 Computer Science in Russia Conference CSR06. Lecture Notes in Computer Science, vol. 3967, pp. 178–190, 2006). A. Gal supported in part by NSF Grant CCF-0430695 and an Alfred P. Sloan Research Fellowship. M. Koucky did part of this work while being a postdoctoral fellow at McGill University, Canada and at CWI, Amsterdam, Netherlands. Supported in part by NWO vici project 2004–2009, project No. 1M0021620808 of MŠMT ČR, grants 201/07/P276, 201/05/0124 of GA ČR, and Institutional Research Plan No. AV0Z10190503. P. McKenzie supported by the NSERC of Canada and the (Québec) FQRNT.     

Oxydation De L'alliage De Titane Ta6V4 Par L'oxygene Sec Entre 700°C Et 1000°C—I. Resultats Experimentaux

The oxidation kinetics of the titanium-base alloy Ti4V6Al was studied between 700 and 1000°C at several pressures of pure oxygen. The result shows a difference in oxidation behaviour between the Ti4V6A1 alloy and pure Ti at high temperatures. (The distinct kinetic law reported has numerous stages corresponding to successive accelerations and reductions in corrosion rate.) The study of the products formed (microscopic observation of cross-sections, examination of the distribution of elements with the microprobe) showed a stratified scale structure with several sublayers of A1₂O₃ parallel to the reaction front.     

Sense induction in folksonomies: a review

Folksonomies, often known as tagging systems, such as the ones used on the popular Delicious or Flickr websites, use a very simple Knowledge Organisation System. Users have thus been quick to adopt this system and create extensive annotations on the Web. However, because of the simplicity of the folksonomy model, the semantics of the tags used is not explicit and can only be inferred from their context of use. This is a barrier for the automatic use of such Knowledge Organisation Systems by computers and new techniques have been developed to extract the semantic of the tags. In this article we discuss the drawbacks of some of these approaches and propose a generalization of the different approaches to detect new senses of terms in a folksonomy. Another weak point of the current state of the art in the field is the lack of formal evaluation methodology; we thus propose a novel evaluation framework. We introduce a dataset and evaluation methodology that enable the comparison of results between different approaches to sense induction in folksonomies. Finally we discuss the performances of different approaches to the task of homonymous/polysemous tag detection and synonymous identification.     

Numerical modelling of interfacial soil erosion with viscous incompressible flows

The aim of this study is to develop a numerical model for simulating surface erosion occurring at a fluid/soil interface subject to a flow process. Balance equations with jump relations are used. A penalization procedure including a fictitious domain method is used to compute the Stokes flow around obstacles, in order to avoid body-fitted unstructured meshes and instead use fast and efficient finite volume approximations on Cartesian meshes. The evolution of the water/soil interface is described by using a level set function. The ability of the model to predict the interfacial erosion of soils is confirmed by several numerical simulations.     

Guaranteed error bounds on pointwise quantities of interest for transient viscodynamics problems

A new method is developed to obtain guaranteed error bounds on pointwise quantities of interest for linear transient viscodynamics problems. The calculation of strict error bounds is based on the concept of “constitutive relation error” (CRE) and the solution of an adjoint problem. The central and original point of this work is the treatment of the singularity in space and time introduced by the loading of the adjoint problem. Hence, the adjoint solution is decomposed into two parts: (i) an analytical part determined from Green’s functions; (ii) a residual part approximated with classical numerical tools (finite element method, Newmark integration scheme). The capabilities and the limits of the proposed approach are analyzed on a 2D example.