Targeted energy transfer in powertrains to reduce vibration-induced energy losses

Systems that generate and transmit power (powertrains) in a variety of engineering applications (automotive, aeronautical, marine, turbo-machinery, renewable energy) can suffer from applied disturbances such as impact and impulsive loading, periodic or random excitation. Modern light weight philosophy and increased engine/generator output power often exacerbate the situation. The resulting vibrations increase fuel consumption unavoidably, which also results in increased emissions. Recent studies have demonstrated the potential to save up to 9.3 million tons of automotive CO2 emissions by reducing the effect of cyclic irregularities of internal combustion engines in automotive transmissions (Joachim et al. "How to minimize power losses in transmissions, axles and steerings", VDI Gears 2011). The use of palliatives to suppress drivetrain vibrations increases the product cost. Furthermore, component wear and fatigue are other effects, adding to operational costs.
Passively controlled transfer of vibrational energy in coupled systems to a target, where the excess or residual energy eventually diminishes, is a - relatively - new concept called Targeted Energy Transfer (TET). It is based on imposing conditions upon nonlinear resonance between a primary source (the powertrain in this case) and a secondary system in order to achieve transfer of energy from one system to the other in an irreversible manner. The secondary system possesses essential stiffness nonlinearity, thus altering the global dynamics because of the lack of a preferential resonant frequency. Therefore, the latter can act as a Nonlinear Energy Sink (NES) over a broad range of excitation frequencies.
Thus, the overarching question in this proposal is "How can one design and develop a sustainable vibration reduction technology for powertrains using the modern TET research method?" This is undertaken with the view of maximising the benefits and limiting the costs to the UK plc, as well as the consumers. Currently, the automotive industry represents 9.2% of the total UK exports (source: Society of Motor Manufacturers and Traders).
The program of research is split into a number of work-packages in order to address the stated key-objective questions:
1. How can a TET mechanism be conceived for powertrain systems to effectively absorb/harvest the excess energy? Therefore, parametric models for scenario-building simulations will be developed to fundamentally understand the energy exchange mechanisms.
2. How much energy would be absorbed by the NES and under what input conditions? Is this method robust to typical variations (and uncertainties) in system parameters, initial conditions and external excitations encountered in powertrain dynamics? How do TET-based designs compare to alternative currently commercialised designs? The latter will be examined at component and system levels.
3. Could the TET mechanism be used for energy harvesting purposes in real powertrain systems?
4. Lastly, effort will be expended in closing the loop between the above questions and consolidating on practical methods of implementing the outcomes of 1-3 above in powertrains according to specific design objectives.
The collaboration between the different project partners will be tightly managed, so that the project objectives are achieved. The generated methods will be made available in the public domain. Automotive systems represent common operating features of powertrains across a variety of engineering applications. Hence, they have been selected for this fundamental generic research. The knowledge and experience accrued in this project can be expanded to a variety of large and small scale power transmission applications for vibration reduction, including aeronautics, marine, renewable energy (wind turbines) and micro-electro-mechanical systems.

The impact of developing new technology for powertrain vibration reduction is generally difficult to quantify. The reduction of noise and adverse effects of incessant vibration have significant, though almost intangible social benefits. However, the optimised vibration-induced energy consumption in powertrains (conserving fuel energy) can be a major effect. This aim is crucial with the rising fuel cost and an imperative undertaking with the growing energy insecurity levels. The market trend to engine downsizing and improved fuel economy requires vibration palliatives that cost up to £65 per installed transmission (see GFT statement of support): dual mass flywheel, advanced torque converters, lock-up clutch and pendulum dampers. Recent studies have shown that optimised flywheels can reduce fuel consumption by up to 12% under regulatory and real-world driving conditions. In the renewable energy sector, advanced drivetrain technology can, on average, reduce the operational/maintenance cost by 7% and increase annual energy generation by 1-2% (source: NREL - USA). Should this new technology lead to benefits of the same order, there would be a significant financial benefit for the UK plc.
The above are just a few examples illustrating the outcome of improved energy efficiency in powertrains. Socio-economically, the project is expected to furnish the UK with unique niche capabilities in drivetrain engineering by developing novel concepts to improve fuel efficiency (via reducing powertrain vibration energy losses). Automotive systems have been selected as an application for this research due to the importance of this industry for the UK economy, since it represents 9.2% of the total UK exports and employs 720,000 people in the industrial arena. The project will support the following aspects of the UK's economy:
1. New commercial services for the supporting companies (Ford, Raicam and GFT). This vertically integrated consortium of vehicle, engine, drivetrain parts and transmission manufacturers will accrue significant benefits either directly by using the research results or indirectly as a result of the synergies between them. Benefits such as drivetrain vibration reduction are not currently realised to their optimal potential. This project will deliver the tools to achieve this central aim and thus enable a holistic approach in assessing the market penetration of the new technologies. It will also allow direct quantification of the benefits in a more detailed manner than hitherto achieved.
2. New or emerging industries. The project will highlight the effectiveness of applying the Targeted Energy Transfer (TET) method in automotive systems against unwanted operating conditions, supporting the UK drivetrain component industry to gain fundamental understanding of the commercial potential of investing in TET concepts. New products incorporating the proposed technological innovation can be developed with further R&D, including parts for use in hybrid drivetrains, where severe transient excitation conditions are encountered. The excess energy harvesting under nonlinear resonance can potentially lead to additional products that can be used to power auxiliary functions in drivetrains.
3. Other research areas. The knowledge and experience accrued in this project will be of a generic nature, enabling it to be expanded into a variety of large and small scale power transmission applications for vibration reduction, including aeronautics, marine, renewable energy (wind turbines), micro-electro-mechanical systems, to name but a few.
The project will also provide answers for key decision makers in the various companies involved with drivetrain technology. The impact will be enhanced technology tools for achievement of maximum accrued benefits to the UK plc. One needs to be prudent in stipulating or quantifying the impact of the proposed research, but the consortium is convinced of a significant commercial impact of the proposed undertaking.