Impact hammer is the current modal testing way in Dynapac testing department. Due to highly damped characteristic of big construction machines, there are a few weaknesses for modal testing when using hammer, such as short response time, limited frequency resolution, poor quality of frequency response functions. Therefore, a more advanced excitation equipment is needed to improve the measurement quality.

The object for this study is to compare two different measuring methods. The thesis will show a comparison between the hammer testing and the shaker MIMO testing compared with analytical model in a highly damped system. It will also give a reference for further highly damped modal analysis and budgetary assessment to decide the budget expenditure.

Result from shaker testing shows a little better correlation than hammer testing compared with FEM model. While the correlation between FEM model and measurement is bad due to many reasons, such as many local modes that can not excited, lack of excitation points, unexpected noise and error from the measurement. While considering the compared results obtained from this machine for now, a simpler structure experiment is suggested to be carried on in the future. Shorter length of stinger can be used to enable higher amplitude of force to excite the property on this machine.