MODELING AND SIMULATION OF GEAR SHIFT CONTROL FOR THE U340 AUTOMATIC TRANSMISSION USING MATLAB–SIMULINK AND STATEFLOW

Abstract

This study presents the modeling and simulation of shift control for the U340 automatic transmission using MATLAB–Simulink and Stateflow software based on a model-based design approach. The objective of this study is to build a system-level model combining physical blocks (engine, hydraulic torque converter, CR–CR planetary gearbox, powertrain – vehicle) and electro-hydraulic control blocks to evaluate the shift pattern, performance, and smoothness of the shifting process. The torque converter is modeled through dimensionless characteristics in the form of lookup tables in Simulink, while the transmission is simulated with discrete gear ratios corresponding to the closed/open states of the clutches and brakes. Simulation scenarios were performed in two cases: changing throttle opening while the vehicle was running on a flat road and fixing throttle opening but changing the simulated rolling resistance torque to simulate steep road conditions. Simulation results show that the model accurately simulates the shifting pattern of the U340 transmission; turbine shaft torque is significantly amplified in the low speed ratio range, improving acceleration capability, while pressure regulation and torque converter lock-up reduce speed fluctuations, enhancing transmission efficiency and smoothness during shifting. The proposed model can be used as an effective tool in research, teaching, and optimization of automatic transmission control strategies, as well as extended to more modern power transmission systems.