A Practical Control Methodology for Parallel Plug-In Hybrid Electric Vehicle Powertrains

This paper presents an original control algorithm for a parallel plug-in hybrid-electric vehicle powertrain. Two operational strategies using this algorithm are designated as EV/CS (battery-only operation followed by charge sustaining operation) and CD/CS (charge depleting blended operation followed by charge sustaining operation) with the same control algorithm used throughout both. An algebraic mapping of three observable variables outputs a single motor torque-command that can either propel or regeneratively brake the vehicle. This mapping is on-line feasible in real time, avoiding the use of look-up tables or some computationally complex optimization approach involving searches over an admissible control space. Another important feature of this methodology is that the highly developed engine and transmission controls of non-hybrid powertrains are essentially maintained. Using a Simulink model, the fuel economy and SOC (state-of-charge) as a function of driving distance for both strategies are presented. Most importantly, results of recorded on-road SOC data are included that shows practicality on a real vehicle in a real driving situation over 96 miles. Also presented are simulated and real driving acceleration results.