In a rotor-bearing system, there are usually some under- or unmodeled dynamic components that are considered frequency dependent, such as foundations, bearings, and seals. This paper presents a method to identify the dynamic behavior of these components using an otherwise accurate engineering model of the system in combination with available measurements of system frequency response functions. The approach permits treatment of flexible rotors and allows that the system test excitations and measurement sensors are not collocated. Because all engineering models contain some residual error and all measurements incorporate an element of noise or uncertainty, the quality of the identified parameters must be estimated. This paper introduces application of $μ$ analysis to solve this problem, resulting in acceptable solution time and hard guarantees of solution reliability. Two illustrative examples are provided, showing that the presented approach is an efficient method to identify and bound these parameters.

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