Integration and Demonstration of High Efficiency Hydraulic Hybrid Propulsion Technology
From autolab
Contents |
[edit] Researchers
- Zoran Filipi, Program Director
- Huei Peng
- Hosam Fathy
- Fernando Tavares
- Rajit Johri
- Ashwin Salvi
- Kevin Morrison
[edit] Background
The State of Michigan started the 21st Century Jobs Fund in 2006 to encourage the development and commercialization of competitive edge technologies. The main goal is to capitalize on the research and commercialization opportunities to enhance economic growth and diversify our economy. By 2006 a strong foundation has been established through the basic research on hybrid propulsion for heavy vehicles in the Automotive Research Center. Early case studies indicated a great fuel economy potential of hydraulics for truck hybrid applications, due to their excellent power density and energy conversion efficiency. It presented a great opportunity to partner with Bosch-Rexroth, a global corporation with a strong presence in Michigan. The 21st Century Jobs Fund program allows the combining of complementary strength of the industry partner and the University of Michigan to develop solutions for practical vehicles.
[edit] Abstract
The project is focused on maximizing the benefits of a series hydraulic hybrid system, and demonstrating clean and efficient propulsion. In the series architecture, there is no mechanical coupling between the engine and the wheels. Instead, a hydraulic traction motor propels the vehicle, and the hydraulic fluid under pressure comes from the accumulator. The traction motor can be reversed to operate as a pump during vehicle braking, thus providing very effective regeneration. A second hydraulic pump coupled to a diesel engine charges the accumulator and ensures desired pressure levels at all times. As a consequence, there is full flexibility in controlling the engine operation and avoiding idling. The initial analysis and optimization of system design and supervisory control is pursued with physics-based simulation tools. However, the effect of realistic engine transients has to be considered when bringing the exhaust emissions into the analysis, and this is accomplished by integrating the real engine with a virtual vehicle simulated on the computer. Simulating the vehicle allows evaluation of alternative system configurations, while having the engine in the test cell enables application of advanced combustion and emission diagnostics. The on-going work expands the hardware-in-the-loop capability to couple a complete hydraulic hybrid propulsion system with the virtual vehicle and demonstrate solutions for different vehicle applications and duty cycles.
[edit] Goals of the work
In case of trucks, opportunities for reducing weight or aerodynamic drag are rather limited, and highly optimized diesel engines have already become a mainstay. Thus, hybridization offers the only path towards significant improvements of fuel economy. Our research aims to maximize the benefits of key mechanisms for improving propulsion efficiency, such as regenerating braking energy, optimizing engine operation and eliminating idling during extended vehicle stops. In addition, we plan to utilize the advanced engine- and powertrain-in-the-loop setup in the Autolab for in-depth studies of transient diesel emission and development of environmentally friendly strategies.
[edit] Achievements
A whole set of models for various hydraulic components has been constructed and coded. The component modules were integrated into a series hydraulic hybrid vehicle platform. The simulation studies allowed analysis of the architecture (e.g. one propulsion motor vs. two, operation in series vs. sequential, insertion of a transmission into the driveline), and optimization of design parameters for a fuel economy objective. The investigations of the supervisory control uncovered the advantages of operating the engine with a modulated strategy during recharging events, rather than insisting on engine operation at the “sweet spot” with frequent and very aggressive power-up events. The integration of the engine with simulated candidate driveline configurations has been fully accomplished and utilized to generate insight into causes for transient spikes of soot emission. Results of the simulation study
- have been validated, with demonstrated 72% improvement of fuel economy over the federal city driving schedule, and 73% reduction of the particle mass emission
- The industry partner Bosch-Rexroth has provided prototype digital displacement hydraulic pump/motors, and efforts are under way to pursue development of clean and efficient strategies with a complete hydraulic hybrid powertrain in the loop.
[edit] References
- SAE 2007-01-4151
- IFP paper (to be added)
