Disturbance analysis using a system bond-graph model

Conventional failure effect analysis depends on the expert's judgement and experience, which may lead to an erroneous result. To solve this problem, this paper proposes a failure effect analysis using bond-graphs, which represent the system behavior in a unified way from the viewpoint of energy flow. The system state equations obtained from a system bond-graph represent the system behavior in the time space domain, and process variables can be obtained in functional forms of state variables and input variables. Qualitative evaluation of deviations caused by a component failure or external disturbance can be analyzed using a tree graph expression of the system state equations. Not only final deviations remaining under the component failure condition, but also initial transient deviations just after the failure occurrence can be obtained by propagating steady state conditions or assumed deviations along the tree graph. An illustrative example of a water flow control system shows the details of the proposed method.