Vehicle Duty Cycle Characteristics for Hybrid Potential Evaluation 2012-01-2023
A range of cycle characteristics have been used to estimate the hybrid potential for vehicle duty cycles including characteristic acceleration, aerodynamic velocity, kinetic intensity, stop time, etc. These parameters give an indication of overall hybrid potential benefits, but do not contain information on the distribution of the available braking energy and the hybrid system power required to capture the braking energy. In this paper, the authors propose two new cycle characteristics to help evaluate overall hybrid potential of vehicle cycles: P50 and P90, which are non-dimensional power limits at 50% and 90% of available braking energy. These characteristics are independent of vehicle type, and help illustrate the potential hybridization benefit of different drive cycles.
First, the distribution of available braking energy as a function of brake power for different vehicle cycles and vehicle classes is analyzed. A non-dimensional power limit is introduced, which allows the definition of a vehicle independent cycle braking power distribution. Each vehicle cycle is found to have a unique curve of fraction of braking energy available as a function of this non-dimensional power limit. Second, two cycles characteristic parameters that characterize the shape of the braking power distribution curve are introduced. These parameters give valuable insight into the hybrid braking power needed to capture the braking energy. A variety of cycles were analyzed using the conventional cycle characteristics and the proposed parameters. The results were compared with hybrid simulations of different hybrid vehicles over the same cycles. The simulation results show good correlation between the hybrid vehicle performance, and the proposed cycle characteristics. The new characteristics not only give some indication of the benefits of hybridization for different cycles, but also provide some insight into the required capability of the hybrid system to achieve those benefits for a given cycle.