Abstract: Taking a heavy-duty tractor as the research object and the sub-structure modeling method was used to establish a reduced vehicle dynamics simulation model including each suspension component and load. The intrinsic characteristics of the model were analyzed and compared with the inherent characteristics of the vehicle model established by the traditional modeling method. The correctness of the model was verified. The sub-structure modal synthesis method was used to study the dynamic response of the vehicle， and compared with the actual vehicle test results. Combined with six sigma optimization design theory and the robustness of heavy tractors was optimized. The results showed that the as-proposed dynamic simulation model can effectively simulate the dynamic characteristics of the vehicle. Under the premise of satisfying the design life， the heavy-duty tractor has improved the anti-interference ability of the system and realized the lightweight of the whole vehicle.

Key words: heavy-duty tractor, inherent characteristics, substructure modal synthesis method, robustness optimization, lightweight