Modified feedback configuration via observer based sensor compensation

Sensor faults affect the system's performance in the closed loop when the faulty sensor readings are used in a feedback control system. This paper presents an observer based sensor fault tolerant control system for practical implementation on modified feedback configuration for close loop control systems. The purpose of this system is to maintain the safety of the system and reliability of the process even in presence of sensor fault by adjusting or modifying the control laws based on a comparison with the state observer. The observer based sensor fault compensating element that is physically connected in parallel with the nominal closed loop system does not interfere with nominal operations i.e. when sensors are not faulty, but will implicitly provide sensor fault compensation signals when sensor fault occurs. An augmentation of an observer based element is required to generate sensor fault compensating signals to a typical feedback control system when sensor fault occurs. In effect, sensor fault tolerance is introduced thus improving control system reliability. A temperature control system is used as a case study. Results of simulation and real time implementation for temperature control system concur and demonstrate the applicability and the obvious improvement of typical closed loop control system reliability via the proposed scheme.