A Real-Time Fortran Implementation of a Sensor Failure Detection, Isolation and Accommodation Algorithm

In recent years, advanced aircraft turbine engine controls have been implemented using digital electronic control mechanisms rather than the hydromechanical control mechanisms used in the past. Studies have shown, however, that digital electronic controls cannot attain sufficient reliability without some level of control component redundancy. There are three areas in which redundancy can be incorporated to improve the reliability of a digital electronic control system. They are the sensors, the actuators and the controls computer itself. The algorithm described herein addresses redundancy in the sensor set. An Advanced, Sensor Failure Detection, Isolation, and Accommodation (ADIA) algorithm for the F100 turbofan engine has been developed for NASA Lewis Research Center under contract. This algorithm uses software or analytical redundancy of the sensors to improve the reliability of the sensor set. The method used requires the controls computer, through software, to determine when a sensor failure has occured without the aid of redundant hardware sensors in the control system. The controls computer then provides an estimate of the correct value of the failed sensor´s output to the control system. This algorithm has been programmed at NASA Lewis on a real-time, microprocessor-based controls computer. A detailed description of the algorithm and its microprocessor implementation can be found in reference 9. Previous to the ADIA algorithm implementation, advanced control algorithms at NASA Lewis were programmed using fixed point assembly language.