Abstract: Multi-transition gear-shift, which needs more than one pair of clutches to be controlled properly, is carried out along with the increasing development of gear number. The shift quality control of multiple transition gear-shift is a more challenging problem compared with the traditional single transition gear-shift process. To achieve a satisfying shift quality during both single and multi-transition gear shift, a dynamic model of automatic transmission containing engine, hydraulic torque converter, planetary gearbox, clutch and load of the vehicle is established. The experimental data of a test vehicle is used to verify the proposed dynamic model of the powertrain. The trajectory of clutch pressure during gearshift is optimized using hp-Legendre-Gauss-Radau method with the objective evaluation index. The test on a hardware in the loop (Hil) test bench is carried out, which can prove the proposed shift quality optimization method is effective to improve the shift quality during both traditional single transition gear shift and multi-transition gear-shift.

Key words: automatictransmission, shiftqualitycontrol, multi-transitiongearshift, trajectoryoptimization