Development Of The Energy Management Strategy For A Hybrid Tricycle

The purpose of this research is to develop an energy management strategy for a hybrid tricycle. The hybrid tricycle has two wheels at the front and one wheel at the rear. The front wheels are driven by in-wheel motors and the rear wheel is driven by an engine power train. The transmission of the engine power train is a Continuous Variable Transmission (CVT) and a final gear. The engine power train is that on the KYMCO Downtown scooter. By doing this, motorcycle manufactures can upgrade their motorcycles to hybrid tricycles easily. From the engine fuel consumption map, one can learn that engine usually has worse performance in low power zone than that in high power zone. Thus, the idea for the energy management strategy design is to activate the motor when the driver required power is low and to activate the engine when the driver required power is high. Simulations show that the fuel consumption rate of the hybrid tricycle is 26.28 km/L and the fuel consumption rate of an engine tricycle is 20.2 km/L. This shows that about 30% of the fuel can be saved with the developed hybrid tricycle.


Introduction
Due to the reason of energy shortage and global warming, Electrical Vehicle (EV) has been a solution to solve the problem among international societies.Among the different types of electrical vehicles, Hybrid Electrical Vehicle (HEV) integrating motor and engine powers is the most successful one.This is because it can provide similar performance as the conventional Internal Combustion Engine (ICE) vehicle in terms of cruising range and power.Also, by an appropriate control strategy, the engine operation can be confined at a fuel efficient zone such that the fuel consumption and emission can be reduced [1].
Currently, many HEVs have been introduced to the market, which includes TOYOTA Prius, FORD Prodigy, Mercedes-BenzBlueHYBRID etc.. Most of these vehicles are middle size and are not suitable for crowded urban area.Thus, to develop a small size hybrid vehicle for urban commuter is the goal of this project.Also, with the concern of market feasibility, a low cost vehicle is desired.Thus, the vehicle uses a KYMCO mass production motorcycle engine EVS25 World Battery,Hybrid and Fuel Cell Electric Vehicle Symposium World Electric Vehicle Journal Vol. 4 -ISSN 2032-6653 -© 2010 WEVA such that the cost of the vehicle can be minimize.
The HEVs can be simply divided into two groups; serial HEV and parallel HEV.Configurations of these two groups of HEV are shown in Figure 1.For the serial HEV, the engine drives a generator to charge the battery and the vehicle is propelled by the motor.Examples of serial HEV are in [2].On the other hand, there are three types of parallel HEV.For the first type, the motor and the engine share the same shaft.For the second type, the motor and engine are coupled by a coupler.Finally, for the third type, the front wheels and rear wheels are driven by motor and engine individually and the configuration of the hybrid Tricycle of this project is the same as the third type of parallel HEV.A typical case of parallel HEV is the TOYOTA Prius [3].

System Configuration And Specification
Figure 2 shows the configuration of the hybrid tricycle.It shows that this tricycle has two seats and has two wheels at the front and one wheel at the rear.
The front wheels are driven by in-wheel motors and the rear wheel is driven by an engine power train.The transmission of the engine power train is a Continuous Variable Transmission (CVT) and a final gear.
A generator is coupled to the output shaft of the engine to charge the battery.The batteries are located at the bottom of the chassis to lower the center of gravity.The total weight of the vehicle including two passengers is 510 kgw is about the size of a mini car.The motor performance curve and engine brake specific fuel consumption (BSFC) map are obtained using testing benches and the results are shown in Figure 3 and Figure 4. Due to the need of the energy management strategy, a fuel efficient variation curve is located and is plotted in Figure 4.
The above results are then summarized into a specification table as shown in Table 1.

Energy Management Strategy
From the engine BSFC map, one can learn that engine usually has worse performance in low power zone than that in high power zone.Thus, the idea for the energy management strategy design is to activate the motor when the driver required power is low and to activate the engine when the driver required power is high.Thus, motor is activated to meet In the charging mode, at every instance, engine is controlled to operate at an optimal point.The optimal point is chosen from the engine fuel map in terms of fuel efficiency and is related to engine speed (i.e.
In this situation, The proposed energy management strategy is shown in Figure 5.

Simulation Results
Figure 6 shows a simulation result of the tricycle dynamics.This simulation assumes that the driver handles the vehicle to follow ECE40 speed pattern perfectly.In this simulation, 0.2 SOC th , W 3600 th P , and the initial SOC is 0.6.One can see that, in this driving pattern, most of the required power is below 3600 W. Thus, motor is activated most of the time, the charging mode is activated rarely, and the SOC drops continuously down to the threshold level of 0.

Conclusion
The purpose of this research is to develop an energy management strategy for a hybrid tricycle.
In this research, a rule base algorithm is adopted for the development of the energy management strategy for its easiness to design.The idea for the energy management strategy design is to activate the motor when the driver required power is low and to activate the engine when the driver required power is high.Simulation results show that the fuel consumption rate of the hybrid tricycle is 26.3 km/L and the fuel consumption rate of an engine tricycle is 16.1 km/L.This shows that about 60% of the fuel can be saved with the developed hybrid tricycle.

Figure 1 :
Figure 1: Configurations of the HEVs

Figure 2 :
Figure 2:configuration of the hybrid tricycle

Figure 3 :Figure 4 :
Figure 3:in-wheel motor performance curve such groups of optimal points are chosen from the fuel consumption map (i.e.

Figure 6 :
Figure 6:(a)ECE40 (b)required power (c)engine power (d)motor power (e)generator power (f)battery SOC (g)operation modesTable 2: Comparison of fuel consumption between hybrid vehicle and engine vehicle

Table 1 :
Specifications of motor and engine EVS25 World Battery,Hybrid and Fuel Cell Electric Vehicle Symposium World Electric Vehicle Journal Vol. 4 -ISSN 2032-6653 -© 2010 WEVA between engine vehicle and hybrid vehicle is shown in Table2, which shows that a dramatic improvement can be reached.