Online and real-time load monitoring for remaining service life prediction of automotive transmissions

This research work proposes the development and the validation of an online and real-time method to predict the remaining service life of the gearwheels of automotive transmissions, with the aim of implementing it on standard control units of series-production vehicles. By focusing on the proposition of a simple, reliable and easy-to-implement solution, the system relies on the combination of an acquisition method of the torques acting in the transmission and a continuous estimation of the damage levels of the gearwheels. Firstly, a state of the art and the theoretical basics are presented concerning a damage estimation based on a nominal stress concept and a linear damage accumulation. The global structure of the damage estimation algorithm is then analyzed and the methodological approach adopted for its development is explained. This is based in principal on a drivetrain model, validated with tests and measurements, where a particular attention is paid to the representation of the gear shifts and the transmission dynamics. Two types of transmissions are considered, namely a standard manual Transmission and a dual clutch transmission mounted in series-production cars. Respectively a requirement analysis for the configuration of the algorithm as well as a requirement specification for the torque acquisition method are performed. On this basis, a state observer is developed and validated, which is able to reconstruct the clutch torque and the transmission output torque. Finally, a synthesis of the complete method and the final version of the algorithm are addressed, and the economic and ecological advantages of the introduction of the method in the context of lightweight design measures are discussed and evaluated.