Abstract
Operational Modal Analysis also known as Output Only Modal Analysis over a decade used for extracting modal parameters of civil engineering structures is now also being used for mechanical structures such as vehicles. The advantage of the method is that no artificial excitations need to be applied to the structure neither force signals to be measured. All the parameter estimation is based upon the response signals, thereby minimizing the work of preparation of the test. This implementation of Operational Modal Analysis uses two different estimation techniques: a non-parametric technique based of Frequency Domain Decomposition (FDD), and a parametric technique working on the raw time domain data, a data driven Stochastic Subspace Identification (SSI) algorithm. These are compared to other methods such as traditional Modal Analysis. This paper will discuss the use of Operational Modal Analysis of a car in operation as well as subassemblies in the car.