Abstract
In this study, a method for estimating the efficiency of electric bicycle power train systems consisting of typical components, such as an electric motor, gears, sprockets, and chains is presented. In order to calculate the efficiency of a power train system, the relationship between the drive motor torque and the road-load that is exerted on the rear wheel was derived, considering kinematic inertia effects and friction losses between power transmission elements. Among the factors that influence efficiency, it was found that friction losses play a dominant role, while the effects of inertia are insignificant. The factors that influence the efficiency of electric bicycles due to friction losses, such as the transmission efficiency of the chain system and the bearing in the sprocket and wheel, were quantified. To validate the proposed efficiency calculation procedure, an experimental electric bicycle was used, in which the driving torque and road-load could be quantitatively assessed, and the actual efficiency was measured on a chassis dynamometer. It is shown that for a given motor torque, a measured and estimated dynamometer torque obtained by the proposed method exhibits a good correlation, and the transmission efficiency of each component was quantified. This method provides a practical and accurate means to calculate the drive train efficiency of electric bicycles at the design stage to improve the efficiency of electric bicycles.
Highlights
Human-powered electric vehicles, such as electric bicycles, kick-scooters, and roller skates, have been widely and increasingly used due to their environmental friendliness
In order to predict the efficiency of electric bicycles at the design stage, even when a full vehicle is not available, this paper proposes a computational method for evaluating the efficiency of power train systems with consideration of the power train system components, as well as the chassis and road-load applied to the vehicle
It can be concluded that the estimated transmission efficiency in this study can evaluate the performance of electric bicycles with reasonable accuracy considering all the components of transmission systems
Summary
Human-powered electric vehicles, such as electric bicycles, kick-scooters, and roller skates, have been widely and increasingly used due to their environmental friendliness. In order to predict the efficiency of electric bicycles at the design stage, even when a full vehicle is not available, this paper proposes a computational method for evaluating the efficiency of power train systems with consideration of the power train system components, as well as the chassis and road-load applied to the vehicle. For this purpose, the dynamic and kinematic characteristics of a drive motor, chassis, and various power transmission elements, such as the chain, belt, bearing, sprocket, etc., are taken into account. To evaluate the performance of electric vehicles, the global positioning system, which can provide the motion information of vehicles, was used to estimate the power and energy consumption of electric vehicles [3,4,5]
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