Traditionally, the controls system in production vehicles with automatic transmission interprets the driver’s accelerator pedal position as a demand for transmission input torque. However, with the advent of electrified vehicles, where actuators are located at different positions in the drivetrain, and of autonomous vehicles, which are self-driving, it is more convenient to interpret the demand (either human or virtual) in vehicle acceleration or wheel torque domain. To this end, a Wheel Torque-based longitudinal Control (WTC) framework was developed, wherein demands can be converted accurately between the vehicle acceleration or wheel torque domain and the transmission assembly input torque domain. For powertrains with a step-ratio transmission and a torque converter (TC), a key challenge of this conversion is the determination of the Inertia Compensation Torque (ICT), which is the torque required to accelerate or decelerate the TC’s impeller when the TC operates in the slipping or open conditions. In the current work, the proposed system computes a target impeller speed, taking into account the states of both the TC (e.g., open, slipping, etc.) and the transmission (i.e., fixed gear or shifting), which is then used to determine this ICT. The developed strategy was baselined against the traditional strategy and was found to be less calibration-intensive and, at the same time, effective in delivering the vehicle acceleration targets.
