Effects of transient powertrain shift dynamics on vehicle handling

This paper investigates the effect of drive shaft torque variations during transmission shifts on vehicle handling performance. In this paper, a lumped mass model for a four-speed automatic transmission powertrain and a 14-degrees-of-freedom vehicle model have been developed and used jointly for the simulation of vehicle transient behaviour during the shift processes. In the investigation, the powertrain model is used as the preprocessor to obtain realistic drive shaft torque that reflects the torque variations intrinsic of transmission shifts. The drive shaft torque thus obtained then serves as the input for the vehicle suspension model. This approach provides better accuracy for vehicle handling analysis than the existing approach that assumes a steady-state axle torque. A mid-size sedan was used as an example in the investigation. Based on model simulation, vehicle responses to powertrain shift transients under various road conditions were quantitatively analysed and compared with that obtained by the existing method.