Control Allocation: A Brief Comparison between a Reference based and a Model Factorization Approaches

Nádia G. Sousa and Luís Cláudio Oliveira-Lopes


Fault Tolerant Control, Control Allocation, Redundancy of Actuators, Reference Model


Industrial process control has suffered significant changes due to pressures associated with increasing competition, rapid changes in economic conditions and tighter environmental laws, thereby promoting its modernization in chemical plants. Therefore, more sophisticated control strategies, which are able to tolerate failures and ensure an efficient response, are easily justifiable in order to maintain the plant operation closer to the economic optimum and within safety limits. In this sense, it is proposed in this work the study and implementation of control allocation methodologies applied to faulty tolerant control. The main feature of control allocation methods are the redundancy of actuators, which can improve performance and reliability of control systems. In this approach, a control law establishes the total control effort required and the distribution of control signals is determined separately by a control allocation module. This work introduces control allocation methodologies based on a reference model and on a model factorization. Benefits of these techniques are investigated in the management of constraints for manipulated variables when implemented on Chemical Engineering systems, in which scenarios with faults in actuators were tested. For all case studies it was observed the ability of the proposed strategies in relocating the control signals among the available actuators, minimizing the faulty effect.

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