Nonlinear adaptive control using non-parametric Gaussian Process prior models

Nonparametric Gaussian Process prior models, taken from Bayesian statistics methodology are used to implement a nonlinear adaptive control law. The expected value of a quadratic cost function is minimised, without ignoring the variance of the model predictions. This leads to implicit regularisation of the control signal (caution), and excitation of the system. The controller has dual features, since it is both tracking a reference signal and learning a model of the system from observed responses. The general method and its main features are illustrated on a simulation example

Neural networks for modelling and control of a non-linear dynamic system

The authors describe the use of neural nets to model and control a nonlinear second-order electromechanical model of a drive system with varying time constants and saturation effects. A model predictive control structure is used. This is compared with a proportional-integral (PI) controller with regard to performance and robustness against disturbances. Two feedforward network types, the multilayer perceptron and radial-basis-function nets, are used to model the system. The problems involved in the transfer of connectionist theory to practice are discussed

Adaptive, cautious, predictive control with Gaussian process priors

Nonparametric Gaussian Process models, a Bayesian statistics approach, are used to implement a nonlinear adaptive control law. Predictions, including propagation of the state uncertainty are made over a k-step horizon. The expected value of a quadratic cost function is minimised, over this prediction horizon, without ignoring the variance of the model predictions. The general method and its main features are illustrated on a simulation example

Irreversible port-Hamiltonian systems : a general formulation of irreversible processes with application to the CSTR.

International audienceIn this paper we suggest a class of quasi-port Hamiltonian systems called Irreversible port Hamiltonian Systems, that expresses simultaneously the first and second principle of thermodynamics as a structural property. These quasi-port Hamiltonian systems are defined with respect to a structure matrix and a modulating function which depends on the thermodynamic relation between state and co-state variables of the system. This modulating function itself is the product of some positive function and the Poisson bracket of the entropy and the energy function. This construction guarantees that the Hamiltonian function is a conserved quantity and simultaneously that the entropy function satisfies a balance equation containing an irreversible entropy creation term. In the second part of the paper, we suggest a lift of the Irreversible Port Hamiltonian Systems to control contact systems defined on the Thermodynamic Phase Space which is canonically endowed with a contact structure associated with Gibbs' relation. For this class of systems we have suggested a lift which avoids any singularity of the contact Hamiltonian function and defines a control contact system on the complete Thermodynamic Phase Space, in contrast to the previously suggested lifts of such systems. Finally we derive the formulation of the balance equations of a CSTR model as an Irreversible Port Hamiltonian System and give two alternative lifts of the CSTR model to a control contact system defined on the complete Thermodynamic Phase Space

Solar thermo-chemical process assisting a pressure oxidation process for co-production of electricity and metal

The mining industry is looking at the use of solar energy to address issues related to highly variable energy prices, falling ore grades, and increasing concern about the industry’s carbon footprint. The pressure oxidation of ore sulfides is an economic alternative to the smelting process because it has the potential to reduce energy consumption and treat low-grade ores. In the pressure oxidation of ore sulfides, the purity and utilization of oxygen are key factors. Indeed, oxygen production and consumption constitute the major operating cost of the pressure oxidation process. Solar thermo-chemical looping processes have been identified as one of the most efficient pathways for the production and storage of oxygen. This study investigates the integration of a solar thermo-chemical looping process with a pressure oxidation process to treat ore sulfide and produce electricity. The analysis shows that the temperature of the cold storage tank has a strong influence on the performance of the complete system. The increase in the cold tank temperature results in a sharp decrease in the size of the receiver. This reduces the investment costs for both the solar receiver and the heliostat field. For the considered case, the useful heat of the solar receiver is 3.7 MWth when the cold tank temperature is set at 100°C. If the cold tank temperature is set at 400°C, the required useful solar heat is about 3.1 MWth and the nominal output of the gas turbine is 0.56 MWe. The analysis showed that about 80% of the useful solar heat can be used to generate oxygen when the temperature of the cold tank is as high as that of the reduction reactio

Health Education across Academic Disciplines (HEAAD): A Tool to Help Students Think Critically about the Risks of Excessive Cell Phone Use

Background and Purpose: Studies have shown that teens who hypertext are at a higher risk to engage in other health risk behaviors including binge drinking, tobacco use, illicit drug use, partaking in physical fights, engaging in risky sexual behavior, and driving distracted. Interventions addressing excessive use of mobile devices have mainly focused on mobile phone use while driving. The aim is to describe the Health Education Across Academic Disciplines (HEAAD) teaching tool and implementation, which may help to educate and raise awareness of the risks associated with excessive cell phone use among adolescents and young adults. Educational Teaching Tool: HEAAD includes introductory activities ranging from identifying risks related to excessive cell phone use to follow-up interactive activities with examples applied across academic disciplines other than health. HEAAD targets students in grades nine through twelve and can be adapted to the college population for freshmen and sophomores enrolled in personal health and wellness classes and/or other health orientation and first year experience classes. Conclusion: HEAAD intends to engage students in practicing decision-making skills related to excessive cell phone use, which may be applicable to their lives. Pilot testing of HEAAD is recommended to determine its effectiveness and potential

Management of community-acquired respiratory tract infections in an era of increasing antibiotic resistance.

Journal ArticleCommunity-acquired respiratory tract infections (RTIs) are prevalent conditions in U.S. and represent a major burden in health care. This article provides an overview of empirical antibiotic treatment options for patients with community-acquired RYIs, including newer classes of agents, such as the respiratory fluoroquinolones and the ketoides. We also discuss the clinical and economic utility of these agents in the current ear of high levels of antibiotic resistance

Modelling and control of multi-energy systems : An irreversible port-Hamiltonian approach.

International audienceIn recent work a class of quasi port Hamiltonian system expressing the first and second principle of thermodynamics as a structural property has been defined : Irreversible port-Hamiltonian system. These systems are very much like port-Hamiltonian systems but differ in that their structure matrices are modulated by a non-linear function that precisely expresses the irreversibility of the system. In a first instance irreversible port-Hamiltonian systems are extended to encompass coupled mechanical and thermodynamical systems, leading to the definition of reversible-irreversible port Hamiltonian systems. In a second instance, the formalism is used to suggest a class of passivity based controllers for thermodynamic systems based on interconnection and Casimir functions. However, the extension of the Casimir method to irreversible port-Hamiltonian systems is not so straightforward due to the "interconnection obstacle". The heat exchanger, a gas-piston system and the non-isothermal CSTR are used to illustrate the formalism

Feedback equivalence of input-output contact sysems.

International audienceControl contact systems represent controlled (or open) irreversible processes which allow to represent simultaneously the energy conservation and the irreversible creation of entropy. Such systems systematically arise in models established in Chemical Engineering. The differential-geometric of these systems is a contact form in the same manner as the symplectic 2-form is associated to Hamiltonian models of mechanics. In this paper we study the feedback preserving the geometric structure of controlled contact systems and renders the closed-loop system again a contact system. It is shown that only a constant control preserves the canonical contact form, hence a state feedback necessarily changes the closed-loop contact form. For strict contact systems, arising from the modelling of thermodynamic systems, a class of state feedback that shapes the closed-loop contact form and contact Hamiltonian function is proposed. The state feedback is given by the composition of an arbitrary function and the control contact Hamiltonian function. The similarity with structure preserving feedback of input-output Hamiltonian systems leads to the definition of input-output contact systems and to the characterization of the feedback equivalence of input-output contact systems. An irreversible thermodynamic process, namely the heat exchanger, is used to illustrate the results