A Study on the Engine Vibration Control of Parallel Hybrid Vehicle based on the On-line Estimation of Engine Torque Fluctuations

For a hybrid electric vehicle (HEV) with a crankshaft-integrated e-motor, the e-motor can be utilized to compensate for typical combustion engine vibrations. This paper presents a feedforward engine vibration control methodology based on efficient real-time estimation of engine torque fluctuation, primarily derived from in-cylinder pressure profiles obtained through steady-state dynamometer tests at various operating points. The measured pressure profiles are decomposed into motoring pressure and combustion pressure components, where the motoring pressure component is further decomposed into idle speed pressure and throttle-associated motoring pressure components. These pressure components are converted into corresponding fluctuating torque elements. The resulting torque profiles are tabulated, then scaled and shifted according to the torque demand and ignition angle under real driving conditions, thereby enabling estimation of the pressure torque and subsequently total torque fluctuation in combination with inertia torque components. The estimated fluctuating torques are compensated for by the integrated e-motor, controlled by the vehicle platform controller (VPC), where the anti-vibration torque is coordinated with other torque demands and system constraints. The proposed control method was validated using a unified simulation model that incorporates a powertrain rigid body vibration system, 1D driveline model, and 1D longitudinal vehicle dynamics, with operating CAN data acquired from on-road vehicle tests. In particular, the implemented vibration control logic accounts for the electrical/electronic (E/E) architecture, wherein all required information is transmitted through the CAN network with non-negligible delays. The results demonstrate that the proposed method effectively reduces engine vibrations, even under highly transient conditions such as engine start, without requiring additional calibration effort.