Design of an Unknown Input Observer for Leak Detection under Process Disturbances

Software-based analysis is one of the main methods for detecting and locating a leak from pipelines without the need for extensive instrumentation. However, software-based methods are generally sensitive to process disturbances, which cause the method to fail. In order to deal with these disturbances without increasing the number of measurements, an observer is designed for leak detection in natural gas pipelines as a case study. The proposed design implements a linear unknown input observer with time delays that considers changes of temperature and pressure as unknown inputs and includes measurement noise in the process. The unknown input observer found in the literature is modified for an application of leak detection. Nonisothermal modeling and simulation of a natural gas pipeline with time-variant consumer usage are performed to test the proposed method. Effects of pressure drop and temperature change on observer estimation are simulated and compared to a simulated leak event