Modified feedback configuration for sensor fault tolerant control

Faults in process control systems can cause undesired reactions and shut-down of a plant, and could be damaging to components, to personnel or the environment. The improvement of reliability, safety and efficiency of the system has become increasingly important. The fundamental purpose of a FTCS scheme is to ensure that faults do not result in system breakdown and although at a lower degree of system performance. The correlative action or prevention measures can be taken to eliminate or minimize the effect of the fault. This paper demonstrates how a feedback control structure can tolerate sensor faults in a temperature control system. The proposed fault-tolerant control design consists of two parts: a nominal performance controller and a model based element to provide sensor fault compensating signals. The nominal controller can have any given structure that satisfies the performance specification, such as a PID controller. When a sensor fault is present, the controller input is augmented to compensate the fault. Results of real time implementation for temperature control are presented to demonstrate the applicability of the proposed FTCS scheme. Sensor faults and disturbance were included to test the proposed design. Deteriorated sensor performance is considered as fault.