Abstract: The fault diagnosis problem is the resolving of a limited set of measurements in terms of a large set of possible but improbable malfunctions. The relation between the measurements and. malfunctions is modeled in part as a set of linear underdetermined equations y = AAx, where y ls a vector of the measurements and x is a vector of malfunction parameter. The least fault principle may be employed to solve the underdetermined equations. There are two kinds of methods for solving this class of problems: The integral minimization approach and the combination minimization approach. The two methods of constrained integral minimization based on the least fault principle are presented in the paper. The introduction of the least fault principle and constraints can ensure effectively the definition and reasonableness of the solution of engine fault equations. A practical example of engine fault diagnosis is given and an evaluation of the methods is made in the paper.

Key words: jet engine, fault diagnosis, minimization, least fault principle, integral minimization solution