Reducing Vibration in Idling Vehicles by Actively Controlling Electric Machine Torque

Abstract

A method is developed to reduce vehicle idling vibration caused by engine torque variation from individual cylinder combustion. This method is theoretically established and experimentally confirmed. Electric machine torque is actively controlled to reduce acceleration variation of the crankshaft, so that the electric machine torque and the engine torque variation cancel each other. This reduces crankshaft rotational speed variation and engine and vehicle vibration. Since the engine torque variation generally increases with engine load, it is desirable to control the electric machine torque so as not to increase the engine load. An electric machine such as a motor generator is used to provide and remove torque from the engine. This reduces vibration more than in machines that absorb engine torque, such as alternators. Experiments using test cars with four-cylinder engines validate these control concepts and clearly show that this control method reduces vibration.