Fault diagnosis

A diagnosis engine (100) for estimating a status of an entity (150, 200) with a plurality of components (c1, . . . , cn) which each is assumed to be in a fault-free mode or be in exactly one of at least one fault mode, the diagnosis engine (100) comprising:

• a processing unit (110) adapted to analyze test results (P1, PR);
• and
• at least one storage area (120, 130, 140) adapted to store diagnostic data in respect of the entity (150, 200), wherein said processing unit (110) is adapted to:
• receive an original disjunction of diagnostic expressions (D) indicating at least one of said modes for at least one of said components (c1, . . . , cn),
• receive test results (P) of a set of diagnostic tests (T) in respect of the entity (150, 200), the result of each test (t1, . . . , tx) being a disjunction of statements (P11 . . . P1x;
• . . . ;
• PR1 . . . PRz) wherein each statement (PJj) indicates at least one of said modes for one of said components (c1, . . . , cn),
• store the expressions in the original disjunction of diagnostic expressions (D) to a temporary disjunction of diagnostic expressions (Dold) in a first storage area (120),
• investigate, for each diagnostic expression in the temporary disjunction of diagnostic expressions (Dold), whether or not a currently investigated diagnostic expression (D1) implies the test result (PJ);
• if not so, remove the expression (D1) from the temporary disjunction of diagnostic expressions (Dold);
• and, for each statement (PJj) in the test result,
• generate a joint diagnostic expression (Dnew) representing a conjunction of the statement (PJj) and the currently investigated diagnostic expression (D1),
• compare the joint diagnostic expression (Dnew) with each diagnostic expression in the original disjunction of diagnostic expressions (D) except for the currently investigated diagnostic expression (D1), and if an original diagnostic expression (Dk) is found, where the joint diagnostic expression (Dnew) implies the original diagnosis expression (Dk),
• discard the joint diagnostic expression (Dnew), and otherwise,
• add the joint diagnostic expression (Dnew) to an updated disjunction of diagnostic expressions (Q) in a second storage area (130), the updated disjunction of diagnostic expressions (Q) representing an estimated status of the entity (150, 200), thereafter
• add all remaining diagnostic expressions in the temporary disjunction of diagnostic expressions (Dold) to the updated disjunction of diagnostic expressions (Q), and
• produce a status report (R[Q]) based on the updated disjunction of diagnostic expressions (Q).