Experimental Identification and Parameter Estimation of the Mechanical Driveline of a Hybrid Bus

Driveline resonances are one of the major reasons for poor vehicle drivability, passenger discomfort, and premature wear of the mechanical parts of the driveline. Therefore, adequate models generated by system identification are essential in order to analyze resonances, and especially to design solutions to mitigate these adverse effects by means of control. In this paper, the resonating mechanical driveline of a hybrid city bus is identified by feeding different excitation signals, such as a pseudo-random binary signal, stepped sine, and chirp to the driveline, and by measuring the frequency response at a standstill and during on-road experiments. The identification experiments are conducted by operating the bus in the series electric hybrid mode, that is, in an operating mode that corresponds to a full electric mode powered by energy storages. Resonating two-mass system models are parametrized based on the obtained frequency responses and used to validate the identification experiments.