Application of knowledge about residual dynamics for fault isolation and identification

This paper is a continuation of publication “Sequential Residual Design Method for Linear Systems” presented on SysTol´2010 conference. The method utilizes knowledge about dynamics of observed symptoms caused by occurring faults. This is an approach alternative to known methods of structural and directional residuals. Concept of designing secondary residuals allowing to obtain specific sequences of symptoms for each fault was proposed in previous work. This paper clarify under which conditions such sequence can be formulated. It also focuses on the way of realizing proper isolation as well as identification procedures. To compare the residuals time series for isolation purpose an index of estimation conformity of sequential residual trajectories is provided. Based on this index, the rules for fault isolation and identification are given. The method is illustrated with the use of application for three tank system. As as summary it is shown that proposed method of sequential residuals is simple to use and allows to design distinguishing sequences having required properties, i. e. simultaneous symptoms, symptoms appearing with required sequence delayed by designed period of time.