Resolution of a Low Speed Vehicle Vibration Issue in EV Mode for a Hybrid Vehicle Prototype

A vehicle vibration issue emerged for a hybrid prototype during low speed driving in EV mode. This work is focused on the effort to identify the root cause and resolve the issue. The endeavor begins by performing a motor test in moderate acceleration with an imposed constant torque load. All relevant information is simultaneously recorded, including vehicle speed, vibration of motor structure and seat track, motor rpm, voltage and current signals, etc. Then analyses are carried out to strive for a better understanding of the vibration characteristics and identify its mechanism. It is found that the torque ripple from the driving motor is the root cause of the low speed vehicle vibration in EV mode, and the torque ripple is found to be induced by the current distortion resulted from the current sensor drift and electromagnetic interference due to high current signals. Finally, a countermeasure is in place which is basically a remedy strategy involving a dynamic compensation technique, a new three-phase cable design with better shielding capability, and a revised layout configuration. As a result, the motor torque ripple is reduced and the vehicle vibration issue is resolved.