Linear Model-Based Predictive Control of the LHC 1.8 K Cryogenic Loop

The LHC accelerator will employ 1800 superconducting magnets (for guidance and focusing of the particle beams) in a pressurized superfluid helium bath at 1.9 K. This temperature is a severely constrained control parameter in order to avoid the transition from the superconducting to the normal state. Cryogenic processes are difficult to regulate due to their highly non-linear physical parameters (heat capacity, thermal conductance, etc.) and undesirable peculiarities like non self-regulating process, inverse response and variable dead time. To reduce the requirements on either temperature sensor or cryogenic system performance, various control strategies have been investigated on a reduced-scale LHC prototype built at CERN (String Test). Model Based Predictive Control (MBPC) is a regulation algorithm based on the explicit use of a process model to forecast the plant output over a certain prediction horizon. This predicted controlled variable is used in an on-line optimization procedure that minimizes an appropriate cost function to determine the manipulated variable. One of the main characteristics of the MBPC is that it can easily incorporate process constraints; therefore the regulation band amplitude can be substantially reduced and optimally placed. An MBPC controller has completed a run where performance and robustness has been compared against a standard PI controller (Proportional and Integral)

Non-Linear Advanced Control of the LHC Inner Triplet Heat Exchanger Test Unit

The future Large Hadron Collider (LHC) at CERN will include eight interaction region final focus magnet systems, the so-called "Inner Triplet", one on each side of the four beam collision points. The Inner Triplets will be cooled in a static bath of pressurized He II nominally at 1.9 K. This temperature is a control parameter and has very severe constraints in order to avoid the transition from the superconducting to normal resistive state. The main difference in these special zones with respect to a regular LHC cell is higher dynamic heat load unevenly distributed which modifies largely the process characteristics and hence the controller performance. Several control strategies have already been tested at CERN in a pilot plant (LHC String Test) which reproduced a LHC half-cell. In order to validate a common control structure along the whole LHC ring, a Nonlinear Model Predictive Control (NMPC) has been developed and implemented in the Inner Triplet Heat Exchanger Unit (IT-HXTU) at CERN. Automation of the Inner Triplet setup and the advanced control techniques deployed based on the Model Based Predictive Control (MBPC) principle are presented

Applying Advanced Control Techniques for Temperature Regulation of the LHC Superconducting Magnets

The temperature of the superconducting magnets for the future LHC accelerator is a control parameter with strict operating constraints imposed by (a) the maximum temperature at which the magnets can o perate, (b) the cooling capacity of the cryogenic system, (c) the variability of applied heat loads and (d) the accuracy of the instrumentation. A temperature regulation with narrow control band can i n principle be achieved by implementing a Model Predictive Control (MPC)-type controller. For this purpose, and for investigating the behaviour of the cooling system, a simulation program has been dev eloped. A prototype MPC controller has been installed and completed its first run

Posible resistencia de iDictyocaulus viviparus/i a fenbendazol en un bovino reporte de caso

Describir el caso de la posible resistencia al fenbendazol en una ternera Jersey infestada por Dictyocaulus viviparus. En el municipio de Entrerrios, Antioquia, Colombia, una hembra de la raza Jersey de 6 meses de edad, presento un serio cuadro de bronconeumonía el cual no mejoró a la aplicación de fenbendazol y enrofloxacina como terapia de mantenimiento. En la necropsia, se observó un número elevado de parásitos vivos compatibles con Dictyocaulus viviparus, determinando una bronquitis verminosa. Este nematodo el cual es tratado rutinariamente con fenbendazol en las fincas lecheras Colombianas, ha demostrado ser resistente frente algunos bencimidazoles, en el presente caso, se pretende describir las posibles causas de esta resistencia del Dictyocaulus viviparus, en la  ternera Jersey

La expresión dramática: un intento de globalización de la educación artística. Fundamentación y propuesta para la formación del maestro de educación primaria

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