Vehicle Surge Reduction Technology during Towing in Parallel HEV Pickup Truck 2022-01-0613

This paper proposes a technology to reduce vehicle surge during towing that utilizes motors and shifting to help ensure comfort in a parallel HEV pickup truck. Hybridization is one way to reduce fuel consumption and help realize carbon neutrality. Parallel HEVs have advantages in the towing, hauling, and high-load operations often carried out by pickup trucks, compared to other HEV systems. Since the engine, motor, torque converter, and transmission are connected in series in a parallel HEV, vehicle surge may occur when the lockup clutch is engaged to enhance fuel efficiency, similar to conventional powertrains. Vehicle surge is a low-frequency vibration phenomenon. In general, the source is torque fluctuation caused by the engine and tires, with amplification provided by first-order torsional driveline resonance, power plant resonance, suspension resonance, and cabin resonance. This vibration is amplified more during towing. Therefore, this paper proposes two surge reduction technologies to help achieve fuel efficiency and surge at the same time during towing. One technology is a gear shift control that avoids engine operating zones where two or more resonance frequencies coincide, which is realized by changing the equivalent inertia via appropriate gear selection. The second technology is an anti-vibration control, which makes effective use of the hybrid system motors by adding motor torque to suppress the relative displacement between the driveline and the tires.