46

CHAPTER 3

HYBRID ELECTRIC VEHICLE DESIGN AND

ANALYSIS

In a country like India, the usage of two wheelers for daily activities is high.

To bring the advancements in these two wheelers, hybrid electric vehicle prototype is

being developed. Presently all two-wheeler vehicles are running on internal

combustion engine for which the propulsion is derived from petrol fuel. Only small in

number the two-wheelers driven with electric motor whose propulsion is derived from

electric batteries. The mixture of both is named as hybrid electric vehicle. Generally

ICE driven two-wheelers can attain high speed, high torque with trustable attributes in

maintenance and replacements. Electric motor driven vehicles can attain

comparatively less speed, less torque with feasible maintenance and replacements.

ICE can serve more life time comparatively to electric motors. Charging the batteries

in electric motor driven vehicles will consume more time and become unavailable for

usage in terms of emergency. Though ICE is efficient comparatively to electric motor,

as of hardly bearable petrol prices the availability to common man is least in usage.

The batteries used in electric vehicles will have a valid life cycle for charging and

discharging and has to be replaced after that. The battery cost will be about 25%-35%

of actual electric vehicle cost which makes the consumer to think twice before buying

these types of vehicles. All these points are justified in the survey conducted on

electric scooter which is already explained in deriving the objectives for designing

and developing this hybrid electric scooter.

3.1 DRIVETRAIN CONFIGURATIN AND DESIGN

Figure 3.1 shows the drivetrain structure in case of parallel hybrid or torque

coupled hybrid electric vehicles. Engine controller, motor controller and electric

motor are the main components present in this drivetrain arrangement. An advance

controller available will be utilized for controlling the engine power and motor speed

through accelerator, involving engine and vehicle speed based on throttle position.

The vehicle controller communicates with the components through drivetrain

algorithm designed for synchronization of the components with each other by

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processing the signals used for communication. Some of the components rely on

component controllers for processing the signals coming from the vehicle controller.

By controlling the propulsion sources present in this drivetrain configuration, ICE,

electric motor, the torque coupling has to be made controlled in this arrangement.

Figure 3.1: Drive train structure of the parallel (torque coupling) hybrid vehicle

In this type of drivetrain arrangements, important factors to be considered are

Engine power

Electric traction motor

Energy sources

Control strategy of the drive train

With the following factors in mind the parallel drive train design is being carried out

Satisfying the gradeability, acceleration and maximum speed

Overall high efficient hybrid electric vehicle

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3.2 PARAMETRIC DESIGN OF DRIVETRAIN

3.2.1 ENGINE POWER

Based on control strategy and sources, in case of parallel hybrid electric

vehicles, the drive train parameters are internal combustion engine, electric motor,

energy capacity and gear ratios. Depending on the vehicle performance and need,

these parameters has to be selected.

Considering flat road and constant speed, the tractive power required in

overcoming the road load or road resistance is given by expressions 3.1 and 3.2.

Where 𝑓𝑟 is the rolling resistance coefficient, M is the mass of the vehicle,

𝑃𝑒 is the engine power, V is speed, 𝜌𝑎 is the air density, 𝐴𝑓 is the frontal area of the

vehicle, 𝐶𝐷 is the aerodynamic drag coefficient, 𝑔 is the gravity due to acceleration

and 𝑖 is the percentage road gradient.

𝑃𝑒 =𝑉

1000𝜂𝑡 ,𝑒 ( 𝑓𝑟𝑀𝑔 +

1

2𝜌𝑎𝐶𝐷𝐴𝑓𝑉

2 + 𝑀𝑔𝑖) KW (3.1)

𝑃𝑒 =𝑉

1000𝜂𝑡 ,𝑒 ( 𝑓𝑟𝑀𝑔 + 𝐹𝑤 + 𝐹𝑔) KW (3.2)

The sum of tractive power required for acceleration and tractive power

required in overcoming the resistances will form the whole engine tractive power of

the vehicle is given by expression 3.3, where 𝛿 is the mass factor coefficient.

𝑃𝑒 =𝑉

1000𝜂𝑡 ,𝑒 ( 𝑓𝑟𝑀𝑔 +

1

2𝜌𝑎𝐶𝐷𝐴𝑓𝑉

2 + 𝑀𝑔𝑖 + 𝑀𝛿𝑑𝑉

𝑑𝑡) KW (3.3)

The transmitted torque from the engine, as applied on driven wheels that is the power

flow is given by the expression 3.4.

𝑇𝑤 = 𝑖𝑔𝑖0𝜂𝑡𝑇𝑃 (3.4)

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Where, 𝑇𝑃 is the torque output with respect to power flow, 𝑖𝑔 is the ratio of

input rotating speed to output rotating speed, 𝑖0 is the gear ratio with respect to the

final drive, 𝜂𝑡 is the efficiency with respect to power driveline.

Figure 3.2: Tractive effort on the driven wheels

The tractive effort on the driven wheels as shown in the Figure 3.2 is given by

expression 3.5.

𝐹𝑡 =𝑖𝑔 𝑖0𝜂𝑡𝑇𝑃

𝑟𝑑 (3.5)

The rotating speed (RPM) of the driven vehicle is given by expressions 3.6 and 3.7.

𝑁𝑤 =𝑁𝑃

𝑖𝑔 𝑖0 (3.6)

𝑉 =𝜋𝑁𝑚 𝑟𝑑

30𝑖𝑔 𝑖0 𝑚/𝑠 (3.7)

Where 𝑁𝑃 is the transmission rotating speed (RPM), which will be equal to

engine speed in manual transmission vehicles and equal to turbine speed with respect

to torque converter in automatic transmission vehicles.

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For the vehicle propulsion, sufficient power has to be delivered by the engine.

During the stop-go conditions, the average power delivered by the engine should be

more than the required average load.

3.2.2 ELECTRIC MOTOR POWER DRIVE DESIGN

Based on the selected motor, the parameters acceleration, power demand and

performance plays major role in vehicle propulsion. The motor acts as supportive

propulsion unit during the peak requirements in parallel type of hybrid vehicles.

The characteristics of variable speed electric motors are shown in the Figure

3.3. In low-speed region, motor will operate at constant torque, whereas in high-speed

region, motor will operate at constant power. This characteristic is represented as the

ratio of its maximum speed to its base speed, that is the speed ratio x. This parameter

can be used for designing geared propulsion vehicles with electric motor.

Figure 3.3: Characteristics of variable speed electric motor

Gradeability, cruising time and maximum speed determines the actual vehicle

performance.

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The tractive effort developed by a traction motor on driven wheels and the

vehicle speed are given by expressions 3.8 and 3.9.

𝐹𝑡 =𝑇𝑚 𝑖𝑔 𝑖0𝜂𝑡

𝑟𝑑 (3.8)

𝑉 =𝜋𝑁𝑚 𝑟𝑑

30𝑖𝑔 𝑖0 (3.9)

Where 𝑇𝑚 and 𝑁𝑚 are the torque corresponding to motor in N-m and speed in

RPM respectively, 𝑖𝑔 is the gear ratio of transmission, 𝑖0 is the gear ratio of final

drive, 𝜂𝑡 is the efficiency of the whole driveline from the motor to the driven wheels,

𝑟𝑑 is the radius of the driven wheels.

3.2.3 ENERGY SOURCES

The Internal combustion engine uses the petrol fuel as energy source for

propulsion and electric traction motor uses rechargeable lead-acid battery power as

energy source for propulsion in the design of the hybrid electric vehicle.

3.3 CONTROL STRATEGIES

The overall control scheme is as shown in the Figure 3.4. In this drivetrain

design, vehicle controller plays major role. The vehicle controller should be

compatible with engine alone mode, motor alone mode and hybrid mode of

operations. The various operation modes are described in Figure 3.5.

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Figure 3.4: Schematic arrangement of control scheme

Figure 3.5: Various operations modes based on Power demand

The operation modes of the drivetrain are explained below

Motor alone propelling mode: when the vehicle speed is less than preset

value 𝑉𝑒𝑏 , which is considered to be the bottom line of the vehicle speed

below which the engine cannot operate stably, or operated with more fuel

consumption and high emissions. The electric motor provides the required

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propulsion with the engine in idling state. The engine power, electric traction

power is given by expressions 3.10 and 3.11.

𝑃𝑒 = 0 (3.10)

𝑃𝑚 = 𝑃𝐿 (3.11)

Where 𝑃𝑒 is the engine power output, 𝑃𝐿 is the propelling power

provided by the driver through the motor controller.

Hybrid propelling mode – Representing the point A in the graph, both the

engine and the motor combine and provide the power to the driven wheels at

the same time. In this case the engine operation will be at optimum operation

line by controlling the engine accelerator or engine operated throttle. Electric

motor provides the remaining power required. The motor power output is

given by expression 3.12.

𝑃𝑚 = 𝑃𝐿 − 𝑃𝑒 (3.12)

Engine alone propelling mode – In this mode, the total propulsion of the

vehicle relies only on the engine. The traction motor will not be powered or

used for propulsion, which can act as generator. Now the motor power is given

by expressions 3.13 and 3.14.

𝑃𝑚 = ( 𝑃𝑒 − 𝑃𝐿) 𝜂𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐 𝑚𝑜𝑡𝑜𝑟 (3.13)

𝑃𝑒 = 𝑃𝐿 (3.14)

The main principle which can be obtained from this control strategy is that, the

optimal utilization of engine and electric motor during the drive with relevant vehicle

controllers employed in the design.

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3.4 PERMANENT MAGNET BLDC MOTOR

Figure 3.6 shows the control arrangement employed generally for Brushless

DC motors. It contains power converter and DSP controller.

Figure 3.6: BLDC motor with control configuration

The torque and speed of the machine is controlled by maintaining the positions

of hall sensors H1, H2 and H3 of the motor rotor. The DSP controller receives the

information regarding these rotor sensors and relevantly provides the gating signals to

the power converter by turning on and off the specific stator pole winding of the

motor.

Based on the geometrical mounting of the permanent magnet in the rotor, the

BLDC motors are categorized as interior mounted motor and surface mounted motor.

This categorization is as shown in the Figure 3.7 (a) and Figure 3.7(b)

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Figure 3.7: (a): Surface mounted (b): Interior mounted

Based on the shape of the EMF waveforms, trapezoidal or sinusoidal the stator

windings are categorized in BLDC motors. The trapezoidal-shaped back EMF BLDC

motor is designed to develop trapezoidal back EMF waveforms. It has the following

ideal characteristics.

Rectangular distribution of magnetic flux in the air gap

Rectangular current waveform

Concentrated stator windings

Excitation waveforms take the form of quasisquare current waveforms with

two 60𝜊 electrical intervals of zero current excitation per cycle. These trapezoidal

back EMF waveform permits some important significations compared to sinusoidal

back EMF machines, stating the resolution requirements for the rotor position sensor

are much lower since only six commutation instants are necessary per electric cycle.

The Figure 3.8 shows the winding configuration of the trapezoidal back EMF BLDC

motor.

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Figure 3.8: Winding configuration of the trapezoidal back EMF BLDC motor

The Figure 3.9(a) shows the equivalent circuit, trapezoidal back EMF and hall

sensor signals of the BLDC motor drive. The coils of the stator are positioned in the

standard three-phase full-pitch, concentrated arrangement and thus the phase

trapezoidal back EMF waveforms are displaced by 120𝜊 electrical degrees. Current

pulse generation is 120𝜊 on and 60𝜊 off type, meaning each phase current is flowing

for 2/3 of an electrical 360𝜊 period, Figure 3.9(b).

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Figure 3.9: (a) Equivalent circuit, (b) Trapezoidal Back EMF and hall sensor signals

A sinusoidal shaped back EMF BLDC motor is designed to develop sinusoidal

back EMF waveforms. It has the following ideal characteristics

Sinusoidal distribution of magnetic flux in the air gap

Sinusoidal current waveforms

Sinusoidal distribution of stator conductors

The fundamental aspect in case of BLDC motor is the back EMF generation in

each phase of the stator winding by the rotation of the magnet producing sinusoidal

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function of the rotor angle. The operation of sinusoidal type of BLDC motor is similar

to that of AC synchronous machine operation. The Figure 3.10 shows the winding

configuration of sinusoidal EMF BLDC machine.

Figure 3.10: The winding configuration of sinusoidal EMF BLDC machine.

Speed-Torque analysis is done considering various applications of electric

motors. The interaction of current and magnetic field will give rise to torque and the

magnetic field is generated by permanent magnets. Magnetic field, source voltage,

back EMF and speed of the machine decides the current drawn by the machine. To

obtain the torque and speed for a particular load, current has to be controlled.

Considering the equivalent circuit for BLDC motor as shown in the Figure

3.11, the analysis can be done.

Figure 3.11: Equivalent circuit for BLDC motor

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The expression for the circuit shown in Figure 3.11 is given by the expressions 3.15 to

3.18.

𝑉𝑡 = 𝐼𝑠𝑅𝑠 + 𝐿𝑠𝑑𝐼𝑠

𝑑𝑡+𝐸𝑠 (3.15)

Where, 𝑉𝑡 is the power supply voltage, 𝑅𝑠 is the resistance of the winding, 𝐿𝑠

is the leakage inductance and 𝐸𝑠 is the back EMF induced in the winding by the

rotating rotor.

𝐸𝑠 = 𝑘𝐸𝜔𝑟 (3.16)

𝑇𝑒 = 𝑘𝑇𝐼𝑠, (3.17)

𝑇𝑒 = 𝑇𝐿 + 𝐽𝑑𝜔𝑟

𝑑𝑡+ 𝐵𝜔𝑟 (3.18)

Where, 𝑘𝐸 is the back EMF constant, which is associated with the permanent

magnets and rotor structure, 𝜔𝑟 is the angular velocity of the rotor, 𝑘𝑇 is the torque

constant, 𝑇𝐿 is the load torque, and 𝐵 represents the viscous resistance coefficient.

Applying Laplace transformation for the above expressions, the transfer function of

the BLDC motor driving system is given by expression 3.19.

𝜔𝑟 𝑠 =𝑘𝑇

𝑅𝑠+𝑠𝐿𝑠 𝑠𝐽+𝐵 +𝑘𝑇𝑘𝐸𝑉𝑡 𝑠 −

𝑅𝑠+𝑠𝐿𝑠

𝑅𝑠+𝑠𝐿𝑠 𝑠𝐽+𝐵 +𝑘𝑇𝑘𝐸𝑇𝐿 𝑠 (3.19)

With variable voltage supply, the winding current can be controlled to its

maximum by actively controlling the voltage. Thus a maximum torque can be

produced as shown in the Figure 3.12

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Figure 3.12: Torque characteristics

3.4.1 CONTROL OF BLDC MOTOR DRIVES

In the case of traction motor applications, by using the accelerator and brake

pedals the torque produced by the electric motor can be made to follow the desired

torque by the driver commanding the vehicle. The Figure 3.13 shows the torque

control scheme for BLDC motor drives. The desired current I is derived from the

torque commanded T through torque controller. The current controller and the

commutation sequencer receives the desired current I, the position information from

the position sensors, the current feedback through current transducers and then

produce the gating signals. These obtained gating signals are sent to three-phase

inverter to produce the desired phase current to the BLDC machine.

Figure 3.13: Torque control scheme for BLDC motor drives

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The speed control may be required during the cruising applications majorly in

case of traction applications. Current feedback is required for high performance

applications for achieving torque control methodology. The DC bus current feedback

is provided to the machine to protect the machine from overcurrents. The

proportional-integral controller or artificial intelligence controller may be used in this

methodology. The methodology may be adopted by utilizing peak current control or

PWM type current control method as shown in the Figure 3.14.

Figure 3.14: Peak current control or PWM type current controls

3.5 DESIGN OF TWO-WHEELER HYBRID ELECTRIC VEHICLE

HEV are the vehicles with more than two energy sources are present. The

major challenges for HEV design are managing multiple energy sources, highly

dependent on driving cycles, battery sizing and battery management. HEV‟s take the

advantages of electric drive to compensate the inherent weakness of ICE, namely

avoiding the idling for increasing the fuel efficiency and reduce emission during

starting and speeding operations. HEV can meet customer‟s need and has added value

but cost is the major issue. These vehicles are of high cost and certain program should

be supported by the specific government for marketing HEVs. The HEVs are

classified into two basic kinds- series and parallel. Recently with introduction of some

HEVs offering the features of both series and parallel hybrids, the classification has

been extended to three kinds- series, parallel and series-parallel. It is interesting to

62

note that some newly introduced HEVs cannot be classified into these three kinds.

Hereby final classification involves series, parallel, series-parallel, complex hybrid.

With respect to all above said factors, considering any ICE driven two-wheeler

vehicle, if the front free wheel is replaced by electric motor in-wheel of hub motor, a

parallel Hybrid Electric –ICE vehicle can be developed . Here both the wheels of the

vehicle will gain individual propulsions. Front wheel will gain propulsion by electric

motor with electric batteries as energy source, whereas rear wheel will gain

propulsion by ICE with petrol as energy source. The vehicle complete motion will be

derived by summing both the propulsions derived. The rear wheel motion is

controlled by accelerator whereas the front wheel motion is controlled by motor speed

controller similar to accelerator. By synchronizing the propulsions of both the wheels

the required total propulsion for the gradient movement in the vehicle can be easily

obtained. Consumption of petrol by only ICE driven vehicle for driving through one

Km distance can be minimized in this case by moderately operating the ICE

accelerator in Sync with electric motor speed controller. Consumption of battery

power by electric motor compared to electric vehicle through a distance of one Km

will be minimized here as its speed is in sync with ICE propulsion. The arrangement

is as shown in the Figure 3.15 and Figure 3.16.

Figure 3.15: Concept of two-wheeler parallel configuration

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Figure 3.16: Concept of two-wheeler parallel Configuration Scooter

As the primary need for this work, the chosen test vehicle for the analysis

purpose is Kinetic Honda Y2K, made, two-stroke, continuously variable transmission,

shown in Figure 3.17, more suitable for testing purpose. Here, the parameters of this

two-wheeler ICE operated vehicle that is the technical specifications are shown in

table 3.1.

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Table 3.1: Technical specification of ICE vehicle (Kinetic Honda) considered for

design

Engine Two-Stroke (petrol)

Transmission Automatic

Engine displacement 98cc

Maximum power 7.7bhp@5600rpm (5.74KW)

Maximum Torque 1.0kgm@5000rpm (9.80665Nm)

Wheelbase 1215mm

Ignition Electronic

Dry Weight 99kg

Battery 12Volts

Front suspension Bottom link hydraulic damper

Rare suspension Unit swing arm/ hydraulic damper

Front tyre size 3.50 X 10.4 Pr

Rear tyre size 3.50 X 10.4 Pr

Figure 3.17: Kinetic Honda Y2K, ICE operated Scooter considered for design

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For obtaining all the result in designing, simulating software MATLAB is

used. The Programs written for the obtained results are attached in Appendix. With

rolling resistance 𝑓𝑟 = 0.01, air density 𝜌𝑎 = 1.205𝑘𝑔/𝑚3, frontal area𝐴𝑓 = 0.7𝑚2 ,

aerodynamic drag coefficient 𝐶𝐷 = 0.3, transmission efficiency from engine to drive

wheels 𝜂𝑡 ,𝑒 = 0.9, and transmission efficiency from motor to drive wheels 𝜂𝑡 ,𝑚 =

0.95, it is seen from the engine characteristics obtained for maximum speed of

60Kmph on flat road is as shown in the Figure 3.18, Considering the force required

for propelling the vehicle summing with respect to acceleration and for overcoming

the road resistances, the engine power for maximum speed of 60Kmph is given also

shown in Figure 3.18.

Figure 3.18: Engine power required (Blue: power for overcoming only road

resistances, Green: overcoming the acceleration criteria along with road resistances)

The vehicle considered for the testing purpose took 12 seconds to reach the

maximum speed of 60Kmph with only the ICE provided for propulsion. The

acceleration curve obtained for the vehicle considered is shown in Figure 3.19.

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Figure 3.19: Acceleration curve for the vehicle considered

Considering the transmission gear ratio, 𝑖𝑔 = 1 (As the engine considered is

continuously variable transmission type and analyzed for flat road) and final wheel

gear ratio 𝑖0= 0.9, the engine power-speed curve obtained is shown in the Figure 3.20.

Figure 3.20: Engine power Vs Speed curve

0 2 4 6 8 10 120

10

20

30

40

50

60

Speed(K

mph)

time(sec)

0 100 200 300 400 500 600 700 8000

0.5

1

1.5

2

2.5

3

3.5

Pow

er

(KW

)

Speed (RPM)

67

In the design of HEV, the main objective lies with the electric motor are to

provide peak power to the drivetrain. It is difficult directly to design the motor power

from the acceleration performance of the vehicle, as we have two power sources, we

can assume or estimate that, the rolling resistance and aerodynamic drag is handled by

the engine and the dynamic load (inertial load in acceleration) is handled by the

motor. With this assumption, acceleration is directly related to the output of electric

motor, the expression for selection of suitable motor can be given by the expression

3.20.

𝑇𝑚 𝑖𝑡𝑚 𝜂𝑡𝑚

𝑟𝑑= 𝛿𝑚𝑀

𝑑𝑉

𝑑𝑡 (3.20)

Where, 𝑇𝑚 is the motor torque, 𝑖𝑡𝑚 is the gear ratio from the motor to the drive

wheel, 𝜂𝑡𝑚 is the transmission efficiency, 𝑟𝑑 is the radius in meters corresponding to

the driven wheel, 𝛿𝑚 is the rotating inertia factor, M is mass in Kg,

The power rating of the motor suitable can be found by using the expression

3.21.

𝑇𝑚 =30𝑃𝑚

𝜋𝑛𝑚 (3.21)

Where 𝑃𝑚 is the motor power rating, 𝑛𝑚 is the motor maximum speed (RPM).

The technical specification of the motor is given in table 3.2

Table 3.2 : Rating of the motor considered for the design

Type of Motor Hub motor

Design of motor BLDC (Brushless DC)

Torque 12Nm

Speed 300RPM

Voltage 60Volts (5 batteries each of 12V, 20Ah)

Efficiency ≥80%

Weight 7Kgs

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The Speed-Torque and Speed-Power characteristics of the motor considered

are shown in the Figure 3.21, Figure 3.22 and Figure 3.23.

Figure 3.21: Speed-Torque Characteristics

Figure 3.22: Speed-Power characteristics

0 2 4 6 8 10 12 14 16 18 200

20

40

60

80

100

120

140

160

180

Speed

Torq

ue

0 2 4 6 8 10 12 14 16 18 20250

250

250

250

250

250

250

Speed

Pow

er

69

Figure 3.23 : Speed-Torque/Power characteristics (Blue: power, Red: Torque curve)

The design concept is developed for driving a scooter with individual wheels

of the vehicle separately propelled with different sources. The rear wheel will be

coupled to the vehicle as in before driven by ICE, whereas the front wheel is replaced

with an electric motor in-wheel hub motor drive driven by five DC batteries. For

analysis, the mechanical arrangements with respect to suspension in the front wheel

are being altered as per the required design for holding the motor wheel as shown in

Figure 3.24 and Figure 3.25.

Figure 3.24: Designed vehicle with front wheel as hub motor

0 2 4 6 8 10 12 14 16 18 200

50

100

150

200

250

300

Speed

Torq

ue/P

ow

er

70

Figure 3.25: Mechanical arrangement made for fixing the hub motor as front wheel

The controller for the motor is being interfaced with the motor speed

regulation shown in Figure 3.26. The speed controlling throttle is being interfaced

through the motor controller circuit. The motor used here is 60V, 250W, Ampere

made hub motor. The controller for the motor is also Ampere made suitable for

controlling the specified motor. The throttle or accelerator is an ampere made throttle

for speed regulation of the specified motor shown in Figure 3.27.

Figure 3.26: motor controller connected to front wheel

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Figure 3.27: Left hand Throttle / Accelerator used for controlling the speed of the

motor

The input to the motor is supplied by five Exide made Electra lead-acid

batteries each of 12V, 20Ah through controller for testing purpose as shown in Figure

3.28.

Figure 3.28: Battery units interconnected and placed on leg guard

Two independent propelling sources are being employed for obtaining total

propulsion of the vehicle. The overview of the vehicle is shown in Figure 3.29. The

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right hand side throttle / accelerator in the vehicle handle corresponds to ICE speed

control, whereas the left hand side throttle / accelerator in the vehicle corresponds to

speed control of electric motor providing the option for the driver to operate the

vehicle in engine-alone mode, motor-alone mode and Hybrid mode(combination of

engine and motor). When the vehicle will be operated in hybrid mode, engine is used

for vehicle propulsion during initial conditions (from the rest) and as the speed of the

vehicle increases engine will be maintained at idling or optimal state by maintaining

the speed of the motor for vehicle propulsion.

Figure 3.29 : overview of the hybrid electric-ICE vehicle

3.6 DESIGN OF DRIVING CYCLE

As the primary need for this work is to record the data, the method of

recording the speed is done through dynamometer provided in the vehicle. For better

analysis of the driving conditions and for classifying it, a survey on specific route of

test area is conducted where a part of Mysore city is considered. The test vehicle, only

in ICE is driven in the test route shown. The route chosen in the test area in Mysore

city as shown in the Figure 3.30.

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Figure 3.30: Driving Route chosen in the test area (Googlemaps, 2014)

The speed in Kmph is recorded in intervals of 10 seconds through the

speedometer present in the vehicle. The speed time curve is plotted with the recorded

data as shown in the Figure 3.31.

Figure 3.31: Speed-Time curve for the derived driving cycle for the test route chosen

0 50 100 150 200 250 3000

5

10

15

20

25

30

35

40

45

50

time(sec)

Speed(K

mph)

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The total distance covered in this trip is 3Km. The time taken for covering this

distance is 280 seconds under moderate traffic condition. The obtained speed-time

curve is analyzed as quadrilateral type. The parameters obtained from the curve are as

follows as shown in table 3.3.

Table 3.3: Parameters obtained from the quadrilateral type analysis for the test route

derived driving cycle

Maximum speed attained

at the end of acceleration

period

50kmph

Speed at the starting of

braking retardation

30kmph

Starting acceleration 6.25kmphps

Braking retardation 7.5kmphps

Coasting retardation 0.07kmphps

Total time of run 280 seconds

Total distance 3.4km

Average speed 44Kmph

From the obtained average speed, it can be concluded that, the driving cycle

comes under Extra Urban Driving Conditions. The distance covered by the vehicle at

the rate of time consideration is shown in the Fig 3.32.

Figure 3.32: Distance-time curve for the derived driving cycle in the test route chosen

0 50 100 150 200 250 3000

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Dis

tance(K

M)

time(sec)

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As it is estimated that, motor is delivering the force for acceleration and ICE is

delivering the force for overcoming the resistances encountered in the road, the

tractive effort Vs Speed curve for flat road is as shown in the Figure 3.33. , where Red

curve indicates the Hybrid operation, Total or combined effort of both motor and ICE

for propulsion), Green curve indicates the Motor operation (tractive effort with

respect to acceleration), Blue curve indicates the engine operation in overcoming the

road load resistances.

Figure 3.33 : Speed-Tractive force curves ( Red: Hybrid operation , Green: Motor

operation, Blue: Engine operation)

The Time Vs Tractive force curves for the driving cycle are shown in the

Figure 3.34 where Red curve indicates the Hybrid operation, Total or combined effort

of both motor and ICE for propulsion), Green curve indicates the Motor operation

(tractive effort with respect to acceleration), Blue curve indicates the engine operation

in overcoming the road load resistances.

0 5 10 15 20 25 30 35 40 45 500

20

40

60

80

100

120

140

160

180

Speed(Kmph)

Tra

ctive f

orc

e(N

ew

tons)

76

Figure 3.34: Time-Tractive force curves (Red: Hybrid operation , Green: Motor

operation, Blue: Engine operation)

The power consumption curve for flat road for the derived driving cycle by

motor and ICE is as shown in the Figure 3.35. Where Red curve indicates the Hybrid

operation, Total or combined power delivered by both motor and ICE for propulsion),

Green curve indicates the Motor power delivered (power delivered with respect to

acceleration), Blue curve indicates the delivered engine power in overcoming the road

load resistances.

Figure 3.35 : Speed-power curves ( Red: Hybrid operation , Green: Motor operation,

Blue: Engine operation)

0 50 100 150 200 250 3000

20

40

60

80

100

120

140

160

180

time(sec)

Tra

ctive f

orc

e(N

ew

tons)

0 5 10 15 20 25 30 35 40 45 500

0.5

1

1.5

2

2.5

3

Speed(Kmph)

Pow

er(

KW

)

77

Considering the gradient from one percent to ten percent in the drivetime,

estimating the engine is being overcoming the road gradient, the power consumption

curve for the drive cycle is as shown in Figure 3.36. Where Red curve indicates the

Hybrid operation, Total or combined power delivered by both motor and ICE for

propulsion), Green curve indicates the Motor power delivered (power delivered with

respect to acceleration), Blue curve indicates the delivered engine power in

overcoming the road load resistances.

Figure 3.36 : Speed-power curves ( Red: Hybrid operation , Green: Motor operation,

Blue: Engine operation) for road gradient from 1 to 10 percent

The Energy curve with the gradient consideration from 1% to 10% in the

driving cycle is shown in Figure 3.37. Where Red curve indicates the Hybrid

operation (both motor and ICE combined), Blue curve represents engine alone mode,

and Green curve represents motor alone mode.

0 5 10 15 20 25 30 35 40 45 500

0.5

1

1.5

2

2.5

3

3.5

4

Speed(Kmph)

Pow

er(

KW

)

78

Figure 3.37 : Energy curves ( Red: Hybrid operation , Green: Motor operation, Blue:

Engine operation) for road gradient from 1 to 10 percent

The energy consumption by the motor, engine and combined mode is as

shown in the Figure 3.38. Where Red curve indicates the Hybrid operation, Total or

combined power delivered by both motor and ICE for propulsion), Green curve

indicates the Motor power delivered (power delivered with respect to acceleration),

Blue curve indicates the delivered engine power in overcoming the road load

resistances.

Figure 3.38: Speed- Energy curves ( Red: Hybrid operation , Green: Motor operation,

Blue: Engine operation) for road gradient from 1 to 10 percent

0 50 100 150 200 250 3000

0.002

0.004

0.006

0.008

0.01

0.012

time(sec)

Energ

y(K

Wh)

0 5 10 15 20 25 30 35 40 45 500

0.002

0.004

0.006

0.008

0.01

0.012

Speed(Kmph)

Energ

y(K

Wh)

79

The time rate of fuel consumption is calculated by expression 3.22.

𝑄𝑓𝑟 =𝑃𝑒𝑔𝑒

1000𝛾𝑓 𝑙/𝑕 (3.22)

Where 𝑔𝑒 is the specific fuel consumption of the engine in g/KWh, 𝛾𝑓 is the

mass density of the fuel in Kg/L, The total fuel consumption for a distance S, with

constant cruising speed of V is given by expression 3.23.

𝑄𝑓𝑟 =𝑃𝑒𝑔𝑒

1000𝛾𝑓 𝑆

𝑉 𝑙𝑖𝑡𝑟𝑒𝑠 (3.23)

3.7 RESULTS OF THE DESIGNED HEV TWO-WHEELER FOR THE

DERIVED DRIVING CYCLE FROM THE TEST ROUTE MYSORE CITY,

INDIA

With an average speed of 40Kmph in the derived driving cycle, for flat road, if

the vehicle is propelled completely by only ICE (engine provides complete tractive

effort, both resistance overcoming and with respect to acceleration), then it should

deliver 2.05KW of power for the vehicle propulsion. With constant 𝑔𝑒 = 250-350

g/KWh, and 𝛾𝑓= 0.737 Kg/ liter, the petrol consumption by the engine in whole

driving cycle derived will be approximately 90ml for engine-only mode. By

considering the combined operation of both ICE (in overcoming the road resistances)

and motor operations (tractive effort with respect to acceleration) for complete

propulsion of the vehicle, with an average speed of 40Kmph, with a motor tractive

power of 1.52KW and engine tractive power of 0.52KW

(1.52KW+0.52KW=2.04KW), the fuel consumption by the engine in the driving cycle

derived will be approximately 25ml. About 50% to 70% of the fuel for ICE can be

saved in this derived driving cycle of the test route chosen if this type of hybrid ICE-

electric vehicle is being designed and followed in driving.

The results show that the simulated vehicle components are compatible and

support the basic requirements of the driving in selected driving cycle of the test area,

Mysore city, Karnataka, India.