Diagnostic schemes for biomedical and engineering systems

For some years the authors have been involved in projects in medical diagnostics and have recently been active in the area of engineering system fault detection and control. The paper is a review of aspects of this work for the purpose of considering similarities and differences with regard to the signal processing and diagnostic techniques appropriately applied in these areas. The basic fact that human biological systems are protected by powerful ethical constraints, both legal and personal, would seem to lead to fundamental differences of approach to medical problems. In particular, there are restrictions on the measurement sites and test protocols appropriate to medical investigations, which means that there are special challenges when designing techniques for processing the limited data so generated. The use of system simulators as reference standards and blackboard schemes for knowledge integration has shown to advantage in medical diagnostics. Experience in the medical field provides new ideas and opportunities for engineering systems diagnostics. In particular, those techniques shown to increase the usefulness of limited data can, conversely, be used to decrease the cost associated with sensors for a given standard of diagnostic reliability. The science of engineering control and diagnostics has benefited from the use of observers based on state space descriptions of the system. An observer provides an alternative reference model and can also be used to generate residuals when faults occur. A new technique employing sliding mode observers to recreate fault signals in engineering systems is introduced. This idea is then extended for use in a medical context.