On-Line Parameter Estimation Issues for the NASA IFCS F-15 Fault Tolerant Systems
Mario G. Perhinschi, Marco Lando, Luca Massotti, Giampiero Campa Marcello R. Napolitano, Mario Luca Fravolini *Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506/6106, -Department of Aeronautical Engineering, Polytechnic of Torino, 10129 Torino, Italy. +Department of Electronic and Information Engineering, University of Perugia, 06100 Perugia, Italy.
Overinstrumented Systems
Advances in sensors and instrumentation have enabled the measurement of variables once thought to be inaccessible. Moreover, sensors have such high reliability that one can safely assume they will operate correctly. A case in point is the instrumentation in commercial aircraft with multiple built-in redundancy. We consider that it has become necessary to revisit the need for state observers. We submit that there is a significant number of dynamic systems where the complete state can be considered available. This class of systems we call overinstrumented and are the subject of our study. We show that it is possible to develop simple identification algorithms that permit speedy determination of system parameters. Moreover, the technique can be easily extended to include systems whose parameters can vary abruptly. This property in turn can be very important in the detection and identification of faults and in the development of adaptive and fault tolerant control algorithms. The paper develops the concept of observation model for the class of overinstrumented system. This model is linear in the system parameters and depends only on available measurements. The paper analyzes the observation model and establishes conditions for the model to be solvable for the system parameters. In particular, the paper shows that controllability is necessary. The paper analyzes the case study of a suspension system using the well known "quarter car model" on a Simulink implementation. Simulation results show that the technique permits identification of multiple changes in the value of the shock absorber constant.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.