Method for determining a structural state of a mechanically loaded unit

The present invention relates to a method for determining a structural state of at least one component of a mechanically loaded target unit, in particular a target unit of a rail vehicle, the method comprising, in an actual excitation step (109.4) of an evaluation cycle (109.3), 5 introducing a defined actual mechanical input signal into the target unit (105.1), in an actual capturing step (109.5) of the evaluation cycle (109.3), capturing an actual mechanical response signal of the target unit (105.1) to the mechanical input signal, and, in an actual evaluation step (109.6) of the evaluation cycle (109.3), comparing the actual mechanical response signal to a previously recorded baseline signal to establish an actual differential o feature and using the actual differential feature to determine the structural state. The baseline signal is representative of a previous mechanical response signal of the target unit (105.1) to a previous mechanical input signal, the previous mechanical input signal having a defined relation to the actual mechanical input signal. In an actual differential feature comparison step (109.10) of the actual evaluation step (109.6), the actual differential feature 5 is compared to at least one reference to determine the structural state, wherein the at least one reference is established from at least one previous differential feature, the at least one previous differential feature having been previously established for the target unit (105.1) in a previous execution of the evaluation cycle (109.3). Figure 3 17704311_1 (GHMatters) P105652.AU.1 WO 2016/066819 PCT/EP2015/07529t DFMW/RE DFA/RE Fig. 4 DFNWIRE DFA/RE DFMW/RE 0TIWV TA t Fig. 5