Project Description

Transportation accounts for 70% of the oil consumed in the United States (DOE data [1]), and 62% of this portion is used by automobiles [1, 2]. However, only 10–16% of the available fuel energy is used to drive the vehicle, i.e. to overcome the resistance from road friction and air drag (DOE and EPA data [3]). Besides engine cycle efficiency, one important mechanism of energy loss in transportation is the dissipation of kinetic energy during vehicle motion and vibration through braking and suspensions. In the past ten years, energy recovery from braking has achieved great commercialization success in hybrid vehicles. However, regenerative vehicle suspensions, which have the advantage of continuous energy recovery, have not come into practice.

The objective of this research paper is to comprehensively assess the potential of energy harvesting from vehicle suspensions and its effect to the vehicle ride comfort and road handling or safety. We will create a integrated modeling of road, vehicle, and harvester, to systematically investigate the road roughness, vehicle speed, tire stiffness, suspension stiffness, absorber damping, sprung and unsprung masses to the energy, comfort, and maneuverability. And based on this study, a scientific criterion will be set for regenerative suspensions on the energy saving, fuel efficiency improvement, environment benefits, and cost limit for various vehicles ranging from class-8 trucks to passenger cars.

Although a few researchers already looked into the regenerative shock absorbers to recovery the energy dissipated in the vehicle suspensions [4-9], the fundamental question is still not clear: How much power is available for harvesting in vehicle suspensions. The amount of harvestable power in literature [4-9] varies in a very large range, from negligible 46 watts to unreasonably high 7500 watts. An answer to this question with scientific confidence is very critical for transportation agencies, state and federal funding agencies, private investors, and researchers to make decision on whether or not worth of the money and effort to develop the energy harvesting technology for transportation applications. If yes, how much is the cost limit for a reasonable payback time like 3 years.

A systematical understanding of the road-vehicle-harvester dynamics is also critical for the development of the energy-harvesting suspensions. Due to the lack of such a system-level understanding, most of the energy harvesting shock absorbers either have very low energy efficiency, or have negative effect on vehicle vibration performance. For example, the ball screw mechanism investigated by [9-12] can significantly magnify the vibration motion and has good energy efficiency, but large force will transfer from the wheel to the vehicle chassis and significant ride comfort will loss at high frequency above 7-10Hz, even with active control. This research paper will provide valuable physical insights to guide the design of the energy harvesters by investigating the tradeoff among energy harvesting, ride comfort, and road handling.

In addition to the modeling, analysis, and simulation, experimental study based on road tests will also be conducted in this research paper. The energy and environment benefits to the individual vehicle and the whole New York State will be assessed.