Energy-Efficient Closed-Loop Speed Control for 4WD Electric Vehicle E-Motors During the Disconnect Clutch Transient Periods

This paper deals with design of an energy-efficient e-motor speed control strategy, which is employed during the e-motor connect and disconnect transients occurring within electric vehicle powertrains with multiple e-motors and disconnect clutches. The proposed control strategy consists of open-loop feedforward control actions aimed to track energy-optimal speed and torque reference profiles, and a conventional speed feedback controller intended to enhance transient and steady-state control accuracy. The optimal feedforward control profiles are derived offline by using dynamic programming (DP) optimization and targeting different connect/disconnect motor speeds. The proposed control strategy is first verified through computer simulations against a conventional, nearly time-optimal baseline feedback speed controller, with the emphasis on energy savings during the clutch connect and disconnect transients. The strategy is then incorporated into the previously developed optimal front/rear-axle torque vectoring control law and executed over different certification driving cycles, in order to assess the overall energy savings gained by energy-efficient e-motor connect/disconnect control.