# Development of a Hybrid Electric Motorcycle that
## 1 Introduction  
To alleviate the effects of global warming caused by greenhouse gas emissions, governments across the world are actively promoting the development of sustainable energy and green industries as well as the reduction of carbon emissions. In response to this trend, electric vehicles have been listed as an important development objective for the automobile industry in Taiwan, particularly the electric motorcycle. Since 2015, at least 10% of locally produced or imported motorcycles in Taiwan must be pure electric motorcycles, hybrid electric motorcycles, or motorcycles with a start-stop function that meets the idling emission standards and hydrocarbon (HC) emission standards for the motorcycle crankcase, fuel tank, and fuel supply system set by the Taiwan Environmental Protection Administration [1]. To comply with this regulation, the Taiwan Industrial Development Bureau has also been promoting electric motorcycles since 2009. However, as of March 2019, the total number of electric motorcycles in use was only 176,000. This low number of electric motorcycles was attributed toconcerns about mileage and kinetic efficiency. The kinetic efficiency may be improved by an optimum design of a hybrid power system [2]. Mileage anxiety can be solved by the development of alternative energy sources [3; 4]. However, there remain major challenges to optimize the power utilization of electric motorcycles. With regard to the development of hybrid electric motorcycles, Piaggio of Italy initially introduced a three-wheel hybrid motorcycle (MP3 Hybrid, Piaggio & C. SpA, Pontedera, Italy) in 2006. The MP3 Hybrid featured a 125-cc internal combustion engine (ICE) and a 2.6-kW electric motor. In addition, using a coaxial parallel system architecture, this motorcycle had five modes: electric motor drive, ICE drive/recharging, dual power drive, braking kinetic energy recycling, and reverse mode. Compared with other gasoline engine motorcycles in the same class, the MP3 Hybrid had 33% less CO\({}_{2}\) emissions and 45% less fuel consumption [5]. In 2009, Yamaha showcased a hybrid motorcycle (HV-X Hybrid, Yamaha Motor Co. Ltd., Iwata, Shizuoka, Japan), which was equipped with a 250 cc ICE and a 15-kW electric motor. Based on the biaxial parallel-type system architecture, these two power sources were integrated or distributed by a single epicyclic gear train. The drive of the HV-X Hybrid could be manually switched between the pure ICE power mode or dual power mode. When traveling under 20 km/h, the vehicle was driven by the electric motor; otherwise, the vehicle was driven by the ICE. Thus, the prevention of both low-efficiency engine operation and idle-stops could be achieved [6]. Subsequently, PGO introduced their hybrid motorcycle (Leon Hybrid 125, PGO Scooters Co. Ltd., Changhua, Taiwan) in 2010, which was equipped with a 125 cc ICE and an 800-W wheel-hub motor. A uniaxial parallel-type system architecture was designed because both the wheel-hub motor and ICE were powered by the rear wheel. The Leon Hybrid was driven by the electric motor at vehicle speeds under 15 km/h and by the dual power mode when speeds exceeded 40 km/h. The average fuel consumption was 70 km/L at a fixed speed of 50 km/h [7]. In recent years, many studies have been conducted on hybrid electric vehicles to improve their performance or reduce environmental pollution. [PERSON] and [PERSON] [8] modified the design and production of the energy management system for a hybrid motorcycle, which carried a 125 cc ICE and a 1-kW electric motor based on a uniaxial parallel system architecture. At vehicle speeds less than 15 km/h, the motorcycle was driven by the electric motor. When the motorcycle speed exceeded 15 km/h, the ICE took over the power output. The ECE-40 (automobile regulations defined by Economic Commission of Europe) test showed that the ICE off-time accounted for approximately 47.5% of the total experiment time, which effectively reduced the quantity of pollutant emissions. [PERSON] et al.