Optimisation of electric motor acoustics of a hybrid dual clutch gearbox using virtual methods

摘要

The dual clutch gearbox DL382E-7A from the S tronic modular assembly matrix, developed jointly by Audi AG and Volkswagen AG Group Components, has been used since 2018 in the A6 and Q5 model series from Audi. In addition to the demands on the power density as well as the efficiency of the electric motor, high priority has been placed on the acoustic demands and, as such, the requirement for quiet driving in the course of the development process of the electrified gearbox. In order to do justice to the high acoustic demands, a (virtual) model has been employed with success in the course of development with a focus on the causes of electromagnetic-related noise. The methods contained therein make it possible to simulate the electromagnetic-related noise behaviour of the drive and to identify productive optimisation measures. The model primarily features a method for simulating the excitation of the electric motor in the form of dynamic air gap forces. The result of the simulation is the acoustic fingerprint, which represents a visualisation of the amplitudes of the air gap forces over the speed and the torque of the electric motor. The method of simulating the excitation is linked to the parameter variation and optimisation of the geometry of the electrical sheet section. In the case of the DL382E-7A, it was possible to successfully achieve a minimisation of the forces from air gap excitation on a virtual basis. The effect of less excitation of the optimised electrical sheet on structure-borne noise was confirmed, on one hand, through suitable structure-borne noise simulations and also, on the other, by relevant trial methods for determining the structure-borne and airborne noise of the drive unit on an acoustic test bed. Another method from the model for minimisation of the forces from air gap excitation is the adaptation of electric motor actuation. Here, in addition to the torque-forming basic harmonics of the inverter voltage, targeted harmonics of the voltage with a coordinated frequency, amplitude and phase were set in the inverter via an acoustic function. The result is optimised current harmonics in the electric motor that ultimately counteract the relevant forces from air gap excitation. By employing the method, it was possible to improve the acoustic properties of the DL382E-7A and as such the vehicle acoustics. Verfication of the optimisation measure using test instrument technology was carried out by measuring the calmed surface vibrations of the drive housing by means of 3D laser vibrometry.