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Mechanical systems with set-valued force laws

Lecture Notes in Applied and Computational Mechanics 2008年 36卷 79-107页

作者： Leine, Remco I. van de Wouw, Nathan Department of Mechanical and Process Engineering Institute of Mechanical Systems ETH Zurich CH-8092 Zurich Switzerland Dynamics and Control Group Department of Mechanical Engineering Eindhoven University of Technology PO Box 513 5600 MB Eindhoven Netherlands

ISBN: (纸本)9783540769743

Some theoretical background on non-smooth systems has been discussed in the previous chapter. Mechanical multibody systems form a special and important class of non-smooth systems, because they can be cast in an elegant structured form. The special structure of mechanical systems is due to the fact that the dynamics is described by the Lagrangian formalism, which links dynamics to variational calculus. Moreover, contact forces are incorporated in the equation of motion by using the Lagrange multiplier theorem. But most importantly, contact forces are (mostly) derived from (pseudo-)potentials or dissipation functions. In this chapter we will discuss the mathematical formulation of Lagrangian mechanical systems with unilateral contact and friction modelled with setvalued force laws. It is important to note that (finite-dimensional) Lagrangian mechanical systems encompass rigid multibody systems as well as discretized continuous systems (e.g. through a Ritz approach or a nite-element discretization) with possible frictional unilateral contacts. First, we discuss how set-valued force laws can be derived from non-smooth potentials. Subsequently, we treat the contact laws for unilateral contact and various types of friction within the setting of non-smooth potential theory. This leads to a unified approach with which all set-valued forces can be formulated. Finally, we incorporate the set-valued forces as Lagrangian multipliers in the Newton-Euler equations. The notation in this chapter is kept as close as possible to the notation of Glocker [63].

关键词： Friction

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Lyapunov stability theory for measure differential inclusions

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Lecture Notes in Applied and Computational Mechanics 2008年 36卷 109-152页

作者： Leine, Remco I. van, de Wouw, Nathan Department of Mechanical and Process Engineering Institute of Mechanical Systems ETH Zurich CH-8092 Zurich Switzerland Dynamics and Control Group Department of Mechanical Engineering Eindhoven University of Technology PO Box 513 5600 MB Eindhoven Netherlands

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ISBN: (纸本)9783540769743

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Stability properties in mechanical systems

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Lecture Notes in Applied and Computational Mechanics 2008年 36卷 153-190页

ISBN: (纸本)9783540769743

In this chapter, we apply the stability results of Chapter 6 for measure differential inclusions to Lagrangian mechanical systems with set-valued force laws, which have been formulated in Chapter 5. The special structure of Lagrangian mechanical systems allows for a natural choice of the Lyapunov function, a systematic derivation of the proof for this large class of systems as well as a physical interpretation of the results. In the following, we study stability properties of equilibrium sets of the measure differential inclusion (5.96) M(q)du - h(q, u)dt = WN(q)dPN+WD(q) dPD ∀t, where dPN and dPd obey the set-valued constitutive laws (5.98). We assume existence of solutions of (5.96) for all admissible initial conditions. We denote an equilibrium position of (5.96) by q*. The generalised velocities u vanish at an equilibrium point as we assume all contacts to be scleronomic (i.e. the normal contact distances gN(q) as well as all relative velocities γD(q,u) do not explicitly depend on time). With Ε we denote an equilibrium set of the measure differential inclusion in first-order form, while Εq is reserved for the union of equilibrium positions q*, i.e. Ε = {(q,u) ∈ n × n q ∈ Εq, u = 0}.

关键词： System stability

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Concluding remarks

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Lecture Notes in Applied and Computational Mechanics 2008年 36卷 217-219+223-232页

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ISBN: (纸本)9783540769743

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"right-first-time" production: A reality or a myth?

"right-first-time" production: A reality or a myth?

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作者： Mahfouf, Mahdi Gama, Miguel Angel Panoutsos, George Institute for Microstructural and Mechanical Process Engineering: the University of Sheffield Department of Automatic Control and Systems Engineering University of Sheffield Sheffield United Kingdom Institute for Microstructural and Mechanical Process Engineering: the University of Sheffield Department of Automatic Control and Systems Engineering University of Sheffield Mappin Street Sheffield S1 3JD United Kingdom

There is no doubt that the move towards the development of cost-effective quality products in a highly competitive market has shaped engineering practices and processes in the production of components. The constituents as well as the processing of materials have now become an integral part of the design process where the required mechanical properties have to be optimized for a given application and at minimal cost not only to the economy but also to the environment. In the case of steel-making companies, very high standards of surface quality and tighter specifications on hot-rolled strips are constantly being set which, more often than not, result in stringent demands being imposed on the specified metallurgical properties. The quality of the strip product may vary depending on how the strip is processed when it passes through the hot strip mill. It is, therefore, important to develop thermomechanical process models which will allow one to predict the evolution of microstructure and the mechanical properties of the strip during the course of fabrication. The acid test, of course, rests with the ability to reverse-engineer (invert) such models in order to control (optimize) the microstructure, and one might argue the ensuing mechanical properties of the material, via the chemistry, the temperature profiles, and the mill schedule. The research activities associated with the Institute for Microstructural and Mechanical process engineering: The University of Sheffield (IMMPETUS) which was founded in 1997 lead to truly integrated interdisciplinary research across the disciplines of systems, mechanical, and metallurgical engineering. The article focuses on the integration of systems engineering paradigms for intelligent modeling and optimization of the mechanical properties of materials, in particular steel, to achieve right-first-time production, a challenge for academia in general, and in particular for IMMPETUS.

关键词： Cost effectiveness

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Application of slope-seeking to a generic car model for active drag control

Application of slope-seeking to a generic car model for acti...

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26th AIAA Applied Aerodynamics Conference

作者： Brunn, André Nitsche, Wolfgang Henning, Lars King, Rudibert Department of Aeronaves and Astronautics Berlin Institute of Technology Germany IAV GmbH Diesel Control Systems Berlin Germany Department of Process Engineering Berlin Institute of Technology Germany

Experimental investigations were carried out aiming at the reduction of the total aerodynamic drag of a generic car model by means of active flow control. Considering the complexity of the near wake of the car model the actuation system consists of steady blowing to influence streamwise vortices, while periodic perturbations were used to control shear layer vortices. This study describes a successful approach for active drag reduction of a generic car model using these different types of actuation simultaneously. A slope-seeking controller is used to And the optimal forcing parameters in order to reduce the overall drag.

关键词： Aerodynamic drag

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An immune algorithm based fuzzy predictive modeling mechanism using variable length coding and multi-objective optimization allied to engineering materials processing

An immune algorithm based fuzzy predictive modeling mechanis...

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IEEE International Conference on Granular Computing (GRC)

作者： Jun Chen Mahdi Mahfouf Department of Automatic Control and Systems Engineering Institute for Microstructural and Mechanical Process Engineering University of Sheffield UK

ISBN: (纸本)9781424425129

In this paper, a systematic multi-objective fuzzy modeling approach is proposed, which can be regarded as a three-stage modeling procedure. In the first stage, an evolutionary based clustering algorithm is developed to extract an initial fuzzy rule base from the data. Based on this model, a back-propagation algorithm with momentum terms is used to refine the initial fuzzy model. The refined model is then used to seed the initial population of an immune inspired multi-objective optimization algorithm in the third stage to obtain a set of fuzzy models with improved transparency. To tackle the problem of simultaneously optimizing the structure and parameters, a variable length coding scheme is adopted to improve the efficiency of the search. The proposed modeling approach is applied to a real data set from the steel industry. Results show that the proposed approach is capable of eliciting not only accurate but also transparent fuzzy models.

关键词： Optimization Fuzzy sets Modeling Clustering algorithms Encoding Accuracy Data models

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Floating pressure conversion and equipment upgrades of two 3.5KW, 20K, helium refrigerators

Floating pressure conversion and equipment upgrades of two 3...

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25th Space Simulation Conference 2008, SSC 2008

作者： Homan, Jonathan Linza, Robert Garcia, Sam Vargas, Gerardo Lauterbach, John Ganni, Venkatarao Sidi-Yekhlef, Ahmed Norton, Robert Creel, Jonathan Urbin, John Howe, Don NASA JSC United States Jacobs Engineering Houston United States GeoControl Systems Houston United States Thomas Jefferson Laboratory United States Linde Cryogenics Division of Linde Process Plants Inc Tulsa United States

ISBN: (纸本)9781622769483

Two helium refrigerators, each rated for 3.5KW at 20K, are used at NASA's Johnson Space Center (JSC) in Building No. 32 to provide cryogenic-pumping within two large thermal-vacuum chambers. These refrigerators were originally commissioned in 1996. Equipment refurbishment and upgrades to the controls of these refrigerators were recently completed. This paper describes some of the mechanical and control issues that necessitated the equipment refurbishment and controls change-over. It will describe the modifications and the new process control which allows the refrigerators to take advantage of the Ganni Cycle "floating pressure" control technology. The upgrades - the controls philosophy change-over to the floating pressure control technology and the newly refurbished equipment - have greatly improved the performance, stability, and efficiency of these two refrigerators. The upgrades have also given the operators more information and details about the operational status of the main components (compressors, expanders etc.) of the refrigerators at all operating conditions (i.e. at various loads in the vacuum chambers). Capabilities, configuration, and performance of the systems, pre and post upgrading are presented.

关键词： Refrigerators

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Modelling Imprecise and Scattered Multidimensional Data Using Granular Data Compression and Multiple Granularity Modelling

Modelling Imprecise and Scattered Multidimensional Data Usin...

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International Conference on Granular Computing

作者： George Panoutsos Mahdi Mahfouf The University of Sheffield UK Department of Automatic Control and Systems Engineering Institute for Microstructural and Mechanical Process Engineering The University of Sheffield (IMMPETUS)

ISBN: (纸本)9781424425129

In this paper a systematic modelling approach is presented, involving two algorithmic procedures: a) a data pre-processing algorithm using granular computing and statistics and b) a granular neural-fuzzy ensemble network consisting of multiple granularity models. Both algorithmic procedures aim to reduce the data and modelling scatter often found in real industrial data. The study focuses on predicting the mechanical property of heat treated steel, in particular Charpy Toughness. This mechanical property yields high data scatter caused by unknown underlying fractural dynamics. The proposed methodology is shown to successfully model the process under investigation using a real industrial data set.

关键词： Data models Predictive models Modeling Testing Computational modeling Energy measurement Noise measurement

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Intelligent control Based on Reinforcement Learning for Batch Thermal Sterilization of Canned Foods

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IFAC Proceedings Volumes 2008年第2期41卷 3568-3573页

作者： S. Syafiie Carlos Vilas Miriam R. Garcia Fernando Tadeo Antonio A. Alonso Ernesto Martinez Department of Systems Engineering and Automatic Control University of Valladolid 47011 Valladolid Spain { Process Engineering Group IIM-CSIC Vigo Spain National Research Council of Argentina Avellaneda 3657 3000-Santa Fe Argentina

A control technique based on Reinforcement Learning is proposed for controlling thermal sterilization of canned food. Without using an a-priori mathematical model of the process, the proposed Model-Free Learning controller (MFLC) aims to follow a temperature profile during two stages of the process: first heating by manipulating the saturated steam valve and then cooling by opening the water valve) by learning. From the defined state-action space, the MFLC agent learns the environment interacting with the process batch to batch and then using a tabular state-action mapping. The results show the advantages of the proposed technique for this kind of processes.

关键词： Reinforcement Learning Intelligent process control Sterilization process Batch process

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