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

Inoculation route-dependent Lassa virus dissemination and shedding dynamics in the natural reservoir – Mastomys natalensis

Lassa virus (LASV), a Risk Group-4 zoonotic haemorrhagic fever virus, affects sub-Saharan African countries. Lassa fever, caused by LASV, results in thousands of annual deaths. Although decades have elapsed since the identification of the Natal multimammate mouse (Mastomys natalensis) as a natural reservoir of LASV, little effort has been made to characterize LASV infection in its reservoir. The natural route of infection and transmission of LASV within M. natalensis remains unknown, and the clinical impact of LASV in M. natalensis is mostly undescribed. Herein, using an outbred colony of M. natalensis, we investigate the replication and dissemination dynamics of LASV in this reservoir following various inoculation routes. Inoculation with LASV, regardless of route, resulted in a systemic infection and accumulation of abundant LASV-RNA in many tissues. LASV infection in the Natal multimammate mice was subclinical, however, clinical chemistry values were transiently altered and immune infiltrates were observed histologically in lungs, spleens and livers, indicating a minor disease with coordinated immune responses are elicited, controlling infection. Intranasal infection resulted in unique virus tissue dissemination dynamics and heightened LASV shedding, compared to subcutaneous inoculation. Our study provides important insights into LASV infection in its natural reservoir using a contemporary infection system, demonstrating that specific inoculation routes result in disparate dissemination outcomes, suggesting intranasal inoculation is important in the maintenance of LASV in the natural reservoir, and emphasizes that selection of the appropriate inoculation route is necessary to examine aspects of viral replication, transmission and responses to zoonotic viruses in their natural reservoirs.Peer Reviewe

Experimental Lagos bat virus infection in straw-colored fruit bats: A suitable model for bat rabies in a natural reservoir species

Rabies is a fatal neurologic disease caused by lyssavirus infection. Bats are important natural reservoir hosts of various lyssaviruses that can be transmitted to people. The epidemiology and pathogenesis of rabies in bats are poorly understood, making it difficult to prevent zoonotic transmission. To further our understanding of lyssavirus pathogenesis in a natural bat host, an experimental model using straw-colored fruit bats (Eidolon helvum) and Lagos bat virus, an endemic lyssavirus in this species, was developed. To determine the lowest viral dose resulting in 100% productive infection, bats in five groups (four bats per group) were inoculated intramuscularly with one of five doses, ranging from 100.1 to 104.1 median tissue culture infectious dose (TCID50). More bats died due to the development of rabies after the middle dose (102.1 TCID50, 4/4 bats) than after lower (101.1, 2/4; 101.1, 2/4) or higher (103.1, 2/4; 104.1, 2/4) doses of virus. In the two highest dose groups, 4/8 bats developed rabies. Of those bats that remained healthy 3/4 bats seroconverted, suggesting that high antigen loads can trigger a strong immune response that abrogates a productive infection. In contrast, in the two lowest dose groups, 3/8 bats developed rabies, 1/8 remained healthy and seroconverted and 4/8 bats remained healthy and did not seroconvert, suggesting these doses are too low to reliably induce infection. The main lesion in all clinically affected bats was meningoencephalitis associated with lyssavirus-positive neurons. Lyssavirus antigen was detected in tongue epithelium (5/11 infected bats) rather than in salivary gland epithelium (0/11), suggesting viral excretion via the tongue. Thus, intramuscular inoculation of 102.1 TCID50 of Lagos bat virus into straw-colored fruit bats is a suitable m

Robust Pid Design For Second-order Processes With Time-delay And Structured Uncertainties.

This paper deals with the problem of PID design for continuous-time systems with time delays. The system is assumed to be free of parametric disturbances and affected by a time-invariant discrete delay of known magnitude. The robustness of the PID control with respect to structured uncertainties is investigated with the small-gain theorem and better performance is sought through the minimization of an upper bound to the closed-loop system H ∞ norm. A Lyapunov-Krasovskii type functional is used yielding delay-dependent design conditions. The controller design is accomplished by means of a convex optimization procedure formulated using linear matrix inequalities (LMIs). Numerical experiments are provided to illustrate the main characteristics of the proposed design method. The particular case of a recycle process controller is addressed. © 2011 IFAC.18PART 146144619Asröm, K.J., Hägglund, T., (1995) PID Controllers, , Instrument Society of AmericaBoyd, S., El Ghaoui, K., Feron, E., Balakrishnan, V., Linear matrix inequality in systems and control theory (1994) Studies in Applied Mathematics, , SIAM, PhiladelphiaGe, M., Chiu, M., Wang, Q., Robust PID controller design via LMI approach (2002) Journal of Process Control, 12, pp. 3-13Grassi, E., Tsakalis, K., Pid controller tuning by frequency loop-shaping: Application to diffusion furnace temperature control (2000) IEEE Transactions on Control Systems Technology, 8 (5). , SeptemberGu, K., An integral inequality in the stability problem of timedelay systems (2000) Proc. 39th IEEE Conf. Decision Contr., 3, pp. 2805-2810. , Sydney, Australia, DecemberHara, S., Iwasaki, T., Shiokata, D., Robust PID control using generalized KYP synthesis (2006) IEEE Control Systems Magazine, pp. 80-91. , FebruaryHohenbichler, N., All stabilizing PID controllers for time delay systems (2009) Automatica, , doi:10.1016/j.automatica.2009.07.026Löfberg, J., YALMIP: A toolbox for modeling and optimization in MATLAB (2004) Proc. 2004 IEEE Int. Symp. on Comput. Aided Control Syst. Des., pp. 284-289. , http://control.ee.ethz.ch/joloef/yalmip.php, Taipei, Taiwan, SeptemberMadhuranthakam, C.R., Elkamel, A., Budman, H., Optimal tuning of PID controllers for FOPTD, SOPTD and SOPTD with lead processes (2008) Chemical Engineering and Processing, 47, pp. 251-264Martelli, G., Stability of PID-controlled second-order time-delay feedback systems (2009) Automatica, , doi:10.1016/j.automatica.2009.05.031O'Dwyer, A., PI and PID controller tuning rule design for processes with delay, to achieve constant gain and phase margins for all values of delay (2001) Proceedings of the Irish Signals and Systems Conference, pp. 96-101. , National University of Ireland, Maynooth, JunePanda, R.C., Yu, C., Huang, H., PID tuning rules for SOPDT systems: Review and some new results (2004) ISA Transactions, 43, p. 283295Rem, J., Zhang, Q., Robust H ∞ control for uncertain descriptor system by proportional-derivative state feedback (2010) International Journal of Control, 83 (1), pp. 89-96. , JanuaryRosinová, D., Veselý, V., Robust PID decentralized controller design using LMI (2007) International Journal of Computers, Communications & Control, 3 (2), pp. 195-204Saeki, M., Fixed structure PID controller design for standard H ∞ control problem (2006) Automatica, , doi:10.1016/j.automatica.2005.07.006Shamsuzzoha, M., Lee, M., Design of advanced PID controller for enhanced disturbance rejection of second-order processes with time delay (2008) AIChE Journal, 54 (6)Sturm, J.F., Using SeDuMi 1.02, a MATLAB toolbox for optimization over symmetric cones (1999) Optim. Method Softw., 11-12, pp. 625-653. , http://sedumi.mcmaster.ca/Ziegler, J.G., Nichols, N.B., Optimum settings for automatic controllers (1942) Transactions of the ASME, 64, pp. 759-768Zhou, K., Doyle, J.C., Glover, K., Robust and optimal control (1996) Upper Saddle River, , NJ USA: Prentice Hal

On the control of non-linear processes: An IDA-PBC approch

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