Proposed FDII for Nonlinear Systems with Partial State Measurement
Similar to many of the existing fault diagnosis methods, the two FDII schemes developed in the previous chapter relied on the availability of full-state measurements. However, even with recent advances in sensor and instrumentation technology, all the states of a dynamical system may not be directly measurable. This might be due to unavailability of operational, accurate, or reliable (on-board) sensors for measurement of some specific physical variables. For example, the state of charge (SOC) in batteries – employed almost everywhere from portable electronics to hybrid electric vehicles (HEV) – cannot be directly measured while the battery is in operation. Some experimental methods certainly exist for measuring the SOC, but such measurements have to be taken under a controlled experimental setup and cannot be achieved while the battery provides power to the system (i.e., laptop, HEV, etc.).