Order Based Modal Analysis Using Vold-Kalman Filter

Abstract

Different from the operational modal analysis (OMA), the order based modal analysis (OBMA) is based on periodic sweep to obtain the dynamic behaviors of machinery. Therefore, its applicable condition is that the mechanical system generates periodic excitation force during the operational process. Due to the imbalance and misalignment of the rotating mechanical, it generates periodic excitation force whose frequency is proportional to the rotational speed during revolution. This paper utilizes OBMA to identify the resonances from the simulated signal with crossing order and white noise. First, the Vold-Kalman filter based order tracking (VK) method is utilized to extract harmonic response known as engine orders. Finally, the least-squares complex frequency-domain estimation method (PolyMAX) is applied to identify the resonance frequency, damping and modal shapes. Especially, two modes whose natural frequencies are close are successfully separated.