Simulation and Controls for Heavy Duty Dual Mode Hybrid Powertrain (Final CRADA Report) (2014)

Hybrid powertrains are of considerable interest because of potential reductions in fuel consumption, criteria pollutants and green house gas (GHG) emissions. Parallel hybrids have been applied to light and medium duty trucks, where urban driving cycles are prevalent, while series hybrids have been successfully used for other applications like transit and school buses. Unfortunately, hybridization of the Class 8, heavy-duty (HD) powertrain is inherently challenging due the expected long-haul driving requirements and limited opportunities for regenerative braking. The Participant has conceived and demonstrated a transformational Dual Mode Hybrid Powertrain (DMHP) technology developed specifically for the needs and function of Class 8 line haul trucks. The DMHP system enables a new paradigm in powertrain operational efficiency in the Class 8 truck segment. It decouples the connection between the engine operating point and the truck road load demands over a broad operating range through an innovative hybrid design. The DMHP operation choices include running in full series, full parallel and engine-off modes. The DMHP offers the opportunity for an engine to operate in a narrow range, thus providing a strategy for maximized fuel economy and minimized emissions. Further, it is expected that transient torque and power wheel demands are handled in whole or part by the electric system, thus reducing the frequency and intensity of engine transients and further improving the fuel economy and emissions. Fuel consumption and emissions have been further reduced through the elimination of overnight hoteling and idling at stops. Finally, based on the unique operating profile of an engine integrated into our hybrid powertrain, a transformational HD truck engine design concept next can emerge. Recent research activities by Oak Ridge National Laboratory (ORNL) have yielded significant data in real-life speed and load profiles of Class 8, long haul trucks. In addition, preliminary simulations of the DMHP carried out by ORNL reveal significant optimization opportunities of the DMHP by applying systematic simulation and controls approaches. An improved understanding of the complex interactions offered by the on-board engine, energy storing system, and electric machines is necessary for the development of control methodologies and practical implementation. We will continue to further this understanding through detailed experimentation and modeling, drawing on and expanding ORNL’s core competency in basic engine research and development (R&D) and advanced controls. This knowledge will be used to develop, implement, and evaluate control strategies on an actual DMHP using Meritor’s components and subsystems. Our initial focus will be on optimization of DMHP utilizing a “stock” diesel engine that is commercially available in the market place. A new DMHP-specific engine design concept will be pursued at a later phase of this Cooperative Research and Development Agreement (CRADA). Meritor will develop the experimental setup, conduct sub-system experiments at their facility, and implement and evaluate potential control strategies resulting from this CRADA partnership. Oak Ridge National Laboratory (ORNL) will develop a real-time simulation model for use in real-time control of the DMHP. The model and potential algorithms will be evaluated on a HD, hybrid powertrain dynamometer facility that will also be developed at the ORNL Vehicle Systems Integration facility.