A real time microcomputer implementation of sensor failure detection for turbofan engines

An algorithm was developed which detects, isolates, and accommodates sensor failures using analytical redundancy. The performance of this algorithm was demonstrated on a full-scale F100 turbofan engine. The algorithm was implemented in real-time on a microprocessor-based controls computer which includes parallel processing and high order language programming. Parallel processing was used to achieve the required computational power for the real-time implementation. High order language programming was used in order to reduce the programming and maintenance costs of the algorithm implementation software. The sensor failure algorithm was combined with an existing multivariable control algorithm to give a complete control implementation with sensor analytical redundancy. The real-time microprocessor implementation of the algorithm which resulted in the successful completion of the algorithm engine demonstration, is described

Sensor failure detection for jet engines

The use of analytical redundancy to improve gas turbine engine control system reliability through sensor failure detection, isolation, and accommodation is surveyed. Both the theoretical and application papers that form the technology base of turbine engine analytical redundancy research are discussed. Also, several important application efforts are reviewed. An assessment of the state-of-the-art in analytical redundancy technology is given

Formal specification of requirements for analytical redundancy-based fault -tolerant flight control systems

Flight control systems are undergoing a rapid process of automation. The use of Fly-By-Wire digital flight control systems in commercial aviation (Airbus 320 and Boeing FBW-B777) is a clear sign of this trend. The increased automation goes in parallel with an increased complexity of flight control systems with obvious consequences on reliability and safety. Flight control systems must meet strict fault-tolerance requirements. The standard solution to achieving fault tolerance capability relies on multi-string architectures. On the other hand, multi-string architectures further increase the complexity of the system inducing a reduction of overall reliability.;In the past two decades a variety of techniques based on analytical redundancy have been suggested for fault diagnosis purposes. While research on analytical redundancy has obtained desirable results, a design methodology involving requirements specification and feasibility analysis of analytical redundancy based fault tolerant flight control systems is missing.;The main objective of this research work is to describe within a formal framework the implications of adopting analytical redundancy as a basis to achieve fault tolerance. The research activity involves analysis of the analytical redundancy approach, analysis of flight control system informal requirements, and re-engineering (modeling and specification) of the fault tolerance requirements. The USAF military specification MIL-F-9490D and supporting documents are adopted as source for the flight control informal requirements. The De Havilland DHC-2 general aviation aircraft equipped with standard autopilot control functions is adopted as pilot application. Relational algebra is adopted as formal framework for the specification of the requirements.;The detailed analysis and formalization of the requirements resulted in a better definition of the fault tolerance problem in the framework of analytical redundancy. Fault tolerance requirements and related certification procedures turned out to be considerably more demanding than those typically adopted in the literature. Furthermore, the research work brought up to light important issues in all fields involved in the specification process, namely flight control system requirements, analytical redundancy, and requirements engineering

Analytical Redundancy Based Predictive Fault Tolerant Control of a Steer-By-Wire System Using Nonlinear Observer

poster abstractA nonlinear observer based analytical redundancy methodology is presented for fault tolerant control of a steer by wire (SBW) system. A long-range predictor based on Diophantine identity has been utilized to improve the fault detection efficiency. The overall predictive fault tolerant control strategy was then implemented and validated on a steer by wire hardware in loop bench. The experimental results showed that the overall robustness of the SBW system was not sacrificed through the usage of analytical redundancy for sensors along with the designed fault detection algorithm. Moreover, the experimental results indicate that the faults could be detected faster using the developed analytical redundancy based algorithms for attenuating-type faults

Fault Residual Generation via Nonlinear Analytical Redundancy

Fault detection is critical in many applications, and analytical redundancy (AR) has been the key underlying tool for many approaches to fault detection. However, the conventional AR approach is formally limited to linear systems. In this brief, we exploit the structure of nonlinear geometric control theory to derive a new nonlinear analytical redundancy (NLAR) framework. The NLAR technique is applicable to affine systems and is seen to be a natural extension of linear AR. The NLAR structure introduced in this brief is tailored toward practical applications. Via an example of robot fault detection, we show the considerable improvement in performance generated by the approach compared with the traditional linear AR approach

Robotic Fault Detection Using Nonlinear Analytical Redundancy

In this paper we discuss the application of our recently developed nonlinear analytical redundancy (NLAR) fault detection technique to a two-degree of freedom robot manipulator. NLAR extends the traditional linear AR technique to derive the maximum possible number of fault detection tests into the continuous nonlinear domain. The ability to handle nonlinear systems vastly expands the accuracy and viable applications of the AR technique. The effectiveness of the approach is demonstrated through an example.NASANational Science Foundatio

Fault Tolerant Control for EMS systems with sensor failure

The paper presents a method to recover the performance of an EMS (Electromagnetic suspension) under faulty air gap measurement. The controller is a combination of classical control loops, a Kalman estimator and analytical redundancy (for the air gap signal). In case of a faulty air gap sensor the air gap signal is recovered using the Kalman filter and analytical redundancy. Simulations verify the proposed sensor Fault Tolerant Control (FTC) method for the EMS system

Directions in propulsion control

The research needs in the area of propulsion control as driven by trends in advanced aircraft are considered. Ongoing propulsion control research at NASA Lewis is discussed. Special emphasis is made on research to improve control system reliability through the use of analytical redundancy to accommodate failed control sensors. In conclusion, a discussion of new research thrusts in the area of supersonic STOVL integrated control and intelligent system control is presented

Advanced detection, isolation, and accommodation of sensor failures in turbofan engines: Real-time microcomputer implementation

The objective of the Advanced Detection, Isolation, and Accommodation Program is to improve the overall demonstrated reliability of digital electronic control systems for turbine engines. For this purpose, an algorithm was developed which detects, isolates, and accommodates sensor failures by using analytical redundancy. The performance of this algorithm was evaluated on a real time engine simulation and was demonstrated on a full scale F100 turbofan engine. The real time implementation of the algorithm is described. The implementation used state-of-the-art microprocessor hardware and software, including parallel processing and high order language programming