Experimental identification of rigid body inertia properties using single-rotor unbalance excitation

Abstract

This article proposes a new experimental method for the identification of rigid body inertia properties. The test structure is suspended in an elastic wire and excited by a single-rotor unbalance actuator. Unlike a conventional shaker or impulse actuator, the proposed actuator can be rigidly attached to the test structure, whereby accurate alignment is made relatively easy. Moreover, because of a sensorless single-rotor design, the actuator can be built at minimal cost. Both the excitation force and the rotation frequency required as feedback to control the actuator are derived from the structure's acceleration response signal; as a result, the experiment requires no sensors other than one accelerometer. The acceleration response measurements are used in an identification algorithm based on models of the unknown rigid body inertia properties and of the suspension properties. In the process of identifying the inertia properties, the suspension model prevents errors otherwise caused by suspension and gravity effects. The proposed method was applied to two test cases: a beam structure and an assembled motorcycle frame and engine. In both cases, accurate rigid body properties could be identified.