Torque fill-in for an automated shift manual transmission in a parallel hybrid electric vehicle

Abstract

An automated shift manual transmission (ASM) is utilized in a post-transmission parallel hybrid electric vehicle to take advantage of its high efficiency and lower cost compared to that of a fully automatic transmission with torque converter. However, a disadvantage of the ASM transmission is that the torque to the drive wheels is disrupted during gear shifts when the clutch is disengaged from the engine, resulting in degraded shift quality over an automatic transmission/torque converter combination. In the hybrid configuration presented here, an electric motor is utilized to provide torque directly to the drive wheels during gear upshifts when the engine is disengaged from the transmission. This torque applied during the shift is referred to as fill-in torque and, if properly applied, can emulate the continuous torque provided by the automatic transmission with torque converter. Effectively, the shift quality of an ASM transmission can be made to approach that of a fully automatic one via proper control of the fill-in torque and engine clutch slip. The amount of motor torque applied and the length of time it is applied are optimized by minimizing an objective metric of transmission shift quality. This paper presents such a control scheme, parameter optimization process, simulation results, and vehicle data that validates the simulation.