Analysis Of The Effect Of Motor Excitation On Transient Torsional Vibration Of Hybrid Electric Vehicle Engine Shaft System

Due to engine working characteristics,the gas explosion pressure and reciprocating inertial force acts on the crankshaft.The tangential and normal forces that change in magnitude and direction periodically cause the crankshaft to produce forced torsional vibration and bending vibration during operation.The violent torsional vibration will cause the crankshaft to break.Hybrid electric vehicles introduce electric motors as a new source of power,thus it’s have more driving modes.Switch the driving mode according to different driving conditions,so that the engine achieves the best fuel consumption.In order to explore the influence of motor excitation on the torsional vibration of the engine shaft system under transient conditions,.This paper selects and matches electric motor of hybrid vehicle based on a certain four-cylinder engine of the company.According to the advantages and of the hybrid configuration,the hybrid vehicle with BSG motor,engine and P2 drive motor is determined.The transient torsional vibration characteristics of the shaft system under the starting conditions and rapid acceleration conditions are simulated and analyzed.First of all,the current research status of torsional vibration of traditional cars and hybrid vehicles at home and abroad and the theoretical basis of torsional vibration are described.Establish an engine model verified by measured cylinder pressure data,and simulate and calculate its universal characteristic curve.The power of the motor is matched and calculated on the basis of the three power requirements of the vehicle’s maximum speed,maximum gradeability,acceleration from 100 kilometers and the universal characteristic curve of the engine.Based on the principle of optimal engine and motor efficiency,hybrid vehicles are divided into driving modes such as pure electric mode,engine mode,motor assist mode,and extended range mode.According to the three-dimensional digital model of the crankshaft,the torsional vibration equivalent model of the engine crankshaft is established in the AVL-excite PU.The free vibration of the shaft system is calculated to obtain the natural frequency and the vibration mode.High-precision torsional vibration is obtained through the method of multi-level modal comparison.It’s forced vibration calculation results are in good agreement with the bench test.It has been verified that the matched rubber shock absorber can better suppress the torsional vibration of the front end of the crankshaft,which lays the foundation for the coupled torsional vibration analysis of the hybrid shafting basis.According to the power requirements of the motor,the motor is designed in AVL-EMT to obtain the parameters required to build the motor unit in AVL-excite PU.Torsional vibration model of the front-end hybrid drive shaft system is established.Simulate and analyze the torsional vibration of the shaft system under two typical transient conditions of startup and rapid acceleration.It is found that under the starting conditions,there is no obvious torsional vibration of the shaft system,but a relatively large 0.5 harmonic rolling vibration occurs.Under the condition of rapid acceleration,there is still a large 0.5 harmonic roll vibration,and the amplitude of the 4th and 6th main-harmonic torsional vibration exceeds the limit of 0.1° within a certain speed range.Combining the dual-mass flywheel with an active control strategy that adjusts the torque distribution of the engine and the motor can effectively reduce the torsional vibration of the shaft system.