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In multi-modular process architectures with independent but interacting subsystems, identification may not be the first choice at hand for closed loop control. A robust relay-based PID autotuning strategy is presented and validated on a quadruple tank system with non-minimum phase dynamics. The controller ensures a specified closed loop robustness, which is of great benefit to the overall performance. The experimental results suggest that the proposed method fulfils the robustness requirement and performs well in various operating conditions of the testbench.

This paper shows a comparison between two linear controllers, a PI-LQR and a Soft-Constrained MPC applied to a Four-Tank process, which main characteristics are the nonlinearities, multiple inputs and outputs coupled together and slow behavior. The model was linearized around an operating point by using an optimization method, named least square. Also, a general mathematic formulation for both controllers is presented that can be extended to any process control. All the procedure was described in detail as well as the simulation results for both controllers. To achieve a real performance comparison the experimental data were obtained under the same conditions and all the response parameters were analyzed., Este documento presenta una comparación entre dos técnicas lineales de controladores conocidos como PI-LOR y MPC con restricciones suaves aplicada a un proceso de cuatro tanques acoplados, cuyas características principales son las no linealidades, múltiples entradas y salidas y una dinámica lenta. El modelo es linealizado alrededor de un punto de funcionamiento utilizando un método de optimización, denominado mínimos cuadrados. Además, se presenta una formulación matemática general para ambos controladores que puede ser fácilmente extendida a cualquier control de procesos. Todo el procedimiento es descrito en detalle, así como los resultados de la simulación para ambos controladores. Para lograr una comparación real del rendimiento, los datos experimentales son obtenidos en las mismas condiciones y se analizaron todos los parámetros de respuesta. &nbsp

For AHWR (Advanced Heavy Water Reactor), a pressure tube type Boiling Water Reactor (BWR) with parallel inter-connected loops, the Steam Drum (SD) level control is closely related to Main Heat Transport (MHT) coolant inventory and sustained heat removal through natural circulation, hence overall safety of the power plant. The MHT configuration with multiple (four) interconnected loops influences the SD level control in a manner which has not been previously addressed. The MHT configuration has been chosen based on comprehensive overall design requirements and certain Postulated Initiated Event (PIEs) for Loss of Coolant Accident (LOCA), which postulates a double ended break in the four partitioned Emergency Core Cooling System (ECCS) header. A conventional individual three-element SD level controller can not account for the highly coupled and interacting behaviors, of the four SD levels. An innovative three-element SD level control scheme is proposed to overcome this situation. The response obtained for a variety of unsymmetrical disturbances shows that the SD levels do not diverge and quickly settle to the various new set points assigned. The proposed scheme also leads to enhanced safety margins for most of the PIEs considered with a little influence on the 100% full power steady-state design conditions.