Practical techniques of characterising unknown dynamic inputs to structures rely on accurate measurements of the response of the system and the application of inverse techniques to identify the different forces and moments applied at the interfaces between the sources and the receiving structure. The sources may be the result of several generating mechanisms contained within a single mechanical unit linked to the structure or the combination of several different components, that are connected independently. This paper discusses some aspects of methods that may be used to separate and evaluate the characteristic force inputs generated by a specific source at the structure interface in a multiple source situation. Inverse methods of force identification are linked with the signals from reference transducers to reduce the effects of interference from secondary sources. It is shown that different types of estimator produce different types of result if signal conditioning is applied to the inverse method. The application of these techniques is illustrated by experiments conducted on a test bench intended for electric motors. The aim of the experiments was to test different ways of reducing errors in identifying the force inputs generated by the motor due to the vibrations of the generator used as a brake on the test bench.
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