Model following with output feedback for Fault Tolerant Control

The increasing control demands for safety-critical applications have led to the need for a new type of control system, capable of guaranteeing that the desired system performances are met, as well as ensuring the system operational safety, both under normal operating conditions and in the presence of system faults. Such systems are known in the literature as Fault Tolerant Control Systems (FTCS) regarding the procedure of redesigning a controller after a fault occurs so that the control objectives from the nominal regime are still achieved - this is referred to as fault accommodation. This paper investigates and applies two controller reconfiguration strategies based on the principles of Model Following (MF) control, namely the Implicit MF (IMF) and the Explicit MF (EMF) approaches, while developing the new control configurations where output feedback is used. The advantages and disadvantages of each technique are briefly discussed and an application example is provided showing how the I/E-MF can be used in aircraft Fault Tolerant Control (FTC).