Final Project: Design of an Electric Vehicle
PROJECT: DESIGN OF AN ELECTRIC VEHICLE
Theory:-
An electric vehicle is a vehicle that runs on electricity alone. Such a vehicle does not contain an Internal
Combustion Engine like the other conventional vehicles. Instead, it employs an electric motor to run the
wheels. These vehicles are becoming very popular nowadays. They are considered to be promising
solution for the future transportation. The most common example is Tesla.
Main component of an Electric vehicles(EV):
The main component of an electric vehicle system are as below;
1. Electric Battery - Battery stores the electricity required to run the vehicle. The battery supplies
electric current to the motor. And thus, the vehicle runs. The higher the capacity of the battery the
higher is the range of an electric vehicles. Most modern electric vehicles uses Lithium-ion type
batteries. These batteries have higher energy density. It means they are capable of storing more
energy.
2. Inverter - Battery stores the electric current in the form of direct current (DC). But , the
majority of the motors used in the electric vehicle runs on alternating current (AC). So, an
inverter performs the function of converting DC into AC.
3. Electric Motor - An electric motor provides the power to rotate the wheels. Motor may be of
DC/AC type. However, the AC motors are more common.
4. Regenerative Braking System - An electric vehicle has only limited energy available. Hence,
we need to save every bit of it. This system recovers the energy lost in braking the vehicle and
utilizes it to change the batteries.
5. Power control unit - The control unit performs the main task. It controls the activities of all
the components of an electric vehicle. It monitors the output of the motor, charging of batteries.
Also, it provides the necessary information to the driver.
Advantages of using an Electric Vehicle:
1. Less air Pollution- There is an absence of any combution process. Hence, these vehicles do
not emit polluting gases into the atmosphere. So they cause less harm to the environment
compared to traditional IC engines powered vehicles.
2. Less Noise Pollution - An electric motor runs quietly. Hence, the noise level while operating
these vehicles is much lower than that of the petrol or diesel engine powered cars. Thus, it
results in very less noise pollution.
3. Higher Efficiency - An efficiency of operation of an electric vehicle is much higher. For e.g.
an efficiency of an electric motor is nearly 90% compared to an Internal Combution Engine.
Hence, in all an electric vehicle is more efficient than petrol or diesel vehicle.
4. Low Maintainance Cost .
5. Low fuel and Operating cost.
Limitations of an Electric Vehicles:-
1. High price - The production of an electric vehicles is not yet done completely on a commercial
basis. Hence, these vehicles are costly then conventional cars running on petrol or diesel.
2. Low Range - Range of an electric-vehicle is the distance that it cover on a single charge. There
have been recent advances in the battery technology. However, the range of these vehicles is still
not as per with that of the regular vehicles are suitable only for low-speed applications.
Block diagram of an EV:
OBJECTIVES:
1] System level configuration of EV:
1. Electric Propulsion Subsystem
2. Energy Source Subsystem
3. Auxiliary Subsystem
The electric propulsion subsystem consists of five components. They are:
A. The Electronic Controller
B. Power Converter
C. Electric Motor
D. Mechanical Transmission
E. Driving Wheels
The energy source subsystem consists of three components. They are:
A. Energy Source(ie Battery,Fuel Cell,Ultracapacitor and others)
B. Energy Refueling Unit
C. Energy Management Unit
The auxiliary subsystem consists of three components. They are:
A. Power Steering Unit
B. Temperature Control Unit
C. Auxiliary Power Supply
Figure 1
Figure 1 is a graphical representation of the general Ev configuration. The black lines have been
used to represent mechanical links. The green lines have been used to represent the electrical links.
The blue lines have been used to represent the transfer of information between the various
components. The power controller is used to provide control signals either switch on or switch off
power converter based on the input signal from the brake and accelerator. The power converter in
turn regulates the flow of power between the electric motor and the energy source. The regenerative
braking system of the EV generates a backward flow of power and this energy is stored in the energy
source. The Energy Management Unit(EMU) works along with the electronic controller to control the
operation of the regenerative, braking system and its energy recovery. Apart from working along with
the electronic controller, the EMU also works with the energy refueling system. It also monitors the
usability of the energy source. The auxiliary powersupply supplies the required amount of power at
different voltage levels to the components of the auxiliary subsystem.
The EV configurations are equipped with the following components. They are:
1. Three Phase AC Motors are used to provide the EV with traction force.
2. A Three-Phase Pulse Width Modulated Inverters are used as power converters.
3. Fixed gearing systems and a differential are used in the mechanical transmission system.
4. Lithium-ion battery packs are used as a source of energy for the EV.
Electric Vehicle Configurations Based On Drive Train Arrangements
There are various ways of arranging the drivetrain of the electric vehicle.
In this section, I will be explaining the six different electric vehicle configurations
based on drivetrain arrangements. They are as follows:
1. Electric Vehicle configuration with clutch, gearbox, and differential.
2. Electric Vehicle configuration without clutch and gearbox.
3. Electric Vehicle configuration with fixed gearing, motor and differential.
4. Electric Vehicle configuration with two Electric Motors(EM).
5. Electric Vehicle configuration with in-wheel motor and mechanical gear.
6. Electric Vehicle configuration with in-wheel motor and no mechanical gear.
Electric Vehicle configuration with clutch, gearbox, and differential:
In this configuration, the electric vehicle has a clutch, gearbox, and differential.
It also has an electric motor. The clutch is connected to the motor. The connection
or disconnection of the flow of power from the electric motor to the wheels is
controlled by the clutch. The gearbox comprises various gears with different gear
ratios. The driver can use the gearbox and clutch to shift the gear ratio to obtain
the required torque and speed for a given terrain.
Figure 2
(Electric Vehicle configuration with clutch, gearbox, and differential).
Electric Vehicle configuration without clutch and gearbox:
In this configuration, the electric motor is connected to a fixed gearing system.
The fixed gearing system is in turn connected to the differential. The weight of
the transmission system is reduced. In this type of configuration, the electric
motor needs to be equipped with a complex control system to provide the
required amount of torque for the wheels.
Figure 3
(Electric Vehicle configuration without clutch and gearbox).
Electric Vehicle configuration with fixed gearing, motor and differential:
In this configuration, the motor is connected to the front wheel. The fixed gearing
system,differential and motor are integrated as a single unit.A lot of space is available
at the rear end of the electric vehicle.
Figure 4
(Electric Vehicle configuration with fixed gearing, motor and differential).
Electric Vehicle configuration with two Electric Motors(EM):
This configuration has dual motors attached with fixed gearing systems to the front wheels.
The differential action required for the cornering is achieved electronically by the two electric
motors attached to the front wheels.
Figure 5
(Electric Vehicle configuration with two Electric Motors).
Electric Vehicle configuration with in-wheel motor and mechanical gear:
To reduce the mechanical transmission path from the electric motor to the wheel,
EV designers prefer to place an electric motor inside a wheel. This is called in-wheel
drive configuration.A fixed planetary gearing system is used to reduce the motor
speed to achieve the desired wheel speed.
Figure 6
(Electric Vehicle configuration with in-wheel motor and mechanical gear).
Electric Vehicle configuration with in-wheel motor and no mechanical gear:
This configuration is very much similar to the EV configuration with in-wheel motor and
mechanical gear but it has no fixed mechanical gearing system. The in-wheel drive system
can be achieved by a low-speed outer electric motor inside the wheel despite abandoning the
use of any type of mechanical gearing system along with the motor.
Figure 7
(Electric Vehicle configuration with in-wheel motor and no mechanical gear)
2] Model parameters
Simulink model for an Electric vehicle is as shown below:
Link: https://drive.google.com/file/d/1Ob71v6PquTDBgnWgkauNuXjbBDz6Kw1_/view?usp=sharing
Drive cycle and Longitudinal driver:
Drive cycle-
A drive cycle is a data set that contains velocity and time data for the purpose of modelling
the motion of a vehicle. It is a plot of the vehicle velocity against the time and it is made to
resemble typical driving conditions that a consumer may experience themselves in. For e.g.
here we have used 2 types of drive cycle data .
1. Newyork bus cycle
2. Artemis motorway of 150kmph.
Drive cycle are used by various testing procedures such as mileage, pollution tests, acc-
leration and top speed tests. There are 3 ways of implementing of a drive cycle. One method
is to create our own drive cycle ans spreadsheet or excel. Other method is signal method and
create signals according to the user and the method that we used is to implement standard
drive cycles which are previously used to test the parameters of the vehicles.
Block parameters of drive cycle source :
Longitudinal driver-
The longitudinal driver block is used for giving normalized acceleration and deceleration
commands to the controller based on two sets of data. The first data is the reference velocity
and second data is feedback velocity. The reference velocity data coming from drive cycle
source and is compared to the feedback velocity data coming from vehicle body. If the
reference velocity is greater than the feedback velocity, an acceleration command will be
given as an output to another control voltage sorce . For the output acceleration and
deceleration command we have used Simulink-PS Converter block. In this case the
input signal is velocity data and this is logic data which have to be converted to a voltage
signals. The ports of this block is follows;
1. Velref - This stands for reference velocity and it is the velocity data provided from a
drive cycle source.
2. Velfdbk - This stands for feedback velocity and it is coming from the vehicle's body
velocity port.
3. Grade - This port provides grade or inclination angle on which the vehicle is travelling
in degrees.
4. Info - This port is for the bus signals which consists of block calculations.
5. Accelcmd - This port provides the acceleration command to a controlled voltage source.
6. Decelcmd - This port provides the deceleration command to another voltage source.
Speed measurement:
In order to measure the speed we have modified the scope block to have two input ports
where one port takes the output and other takes the output signal from the drive cycle to the
reference velocity port on the longitudinal driver block. This has been done to compare the
two speeds and check whether they overlap and achieve the same speed.
Distance measurement:
Mathematical blocks and scope block is used to measure the distance travelled by the
vehicle. 1st we have to imlement the integrator block to integrate the velocity signal that
is output from the velocity subsystem. Divide block along with constant block having a
value of 3600 is used to divide the integrated speed. this will give us the distance travelled
in kilometers.
SOC ( state of charge) estimate subsystem:
To measure the state of charge of the battery , a subsystem was created of various blocks.
The 1st block integrator block is used to handle data transfer and integrate the value of the
current signal w.r..t. time and 2nd is the Gain block is used in order to multiplier-divide the
signal coming from the integrator block. This block will divide the current with the Ampere
rating of battery which is 140(Ah) * 3600(sec in Hour). Assuming the battery is always fully
charged we have added the constant block with a value of 1 representing 100%. After that
a sum block is used to perform addition and subtraction operations. This blocks are made
into a subsystem called SOC estimate. A scope block is used at the junction of the PS-
Simulink converter block to plot the output signal of the current from the battery.
Block parameters of the gain block:
Motor and controller Subsystem:
List of components:
1. DC motor
2. H-bridge
3.Controlled PWM voltage
4. Controlled voltage source
5. Current sensor
DC motor:
In this simulation, DC motor is used as it is easy to model and have a very few parameters
to run for the application. There are two sides of this DC motor block. The mechanical
side is on the right and the electrical side is on the left. Mechanical side has two ports
C and R. C stands for casing and is the stable part and R is the rotor which produces a
torque.The electrical side has a +ve and -ve side for voltage to be applied. If +ve voltage
is applied to the motor block from the +ve to the -terminal then a +ve torque will act
from C to R port. The direction of torque can be reversed by changing the sign of the back
emf or torque constant. C port is connected to the mechanical rotational reference. The
R port is connected to the gear in the vehicle body block.
Parameters of a DC motor:
H-bridge:
This is a power converter which is needed to provide power of the correct form and
magnitude from one component to other. In case of EV, a power converter is needed
to provide a DC voltage from the battery of the EV to the DC motor, so that it can
function properly at the required parameters . we have used an H-bridge motor drive
as a power converter. The left side is controlling a voltage signals and the right side
terminal to provide the controlled voltage to the DC motor . ports included as follows
1. PWM - Pulse Width Modulation
2. REF - Reference
3. REV - Reverse
4. BRK - Brake
Block parameters of an H-bridge:
The simulation is kept in an average mode because PWM mode will take longer
duration for simulation. Also bridge parameter output voltage amplitude was
modified to 400 volts according to DC motor.
Controlled PWM Voltage:
A controlled pwm voltage is used to provide a controlled pulse width modulated voltage
to the H-bridge block. The pulses of voltage are created by this block are dependent in
the duty cycle which is in that ratio of time that the switch is ON to the time taken for
one cycle. The duty cycle formula is given by,
Duty cycle = Ton/Toff + Toff
= Ton/Tcyc
where, Ton = On time.
Tcyc = Time taken for one cycle.
Block parameter of PWM voltage:
By adjusting simulation mode to an averaged the simulation will be quicker.
And keeping all remaining parameter by default.
Controlled Voltage Source:
This blocks provides a necessary voltage that is powerfull enough to mainatin the
voltage at the output regardless of the current that passes through it. In this
subsystem control voltage block have been used. One block is used for acceleration
and other to provide the voltage for deceleration.
Electrical reference block is used to create grounding effect for electrical circuits.
Solver configuration block is used to solve any necessary equations in a system.
it is used in the connection to the REV port of the H-bridge block.
Battery subsystem:
The battery used to store an energy in the EV and it contain the electrical energy in
the form of DC and provide energy to operate it.
Nominal voltage has been set to 600 volts, internal resistance has been set to 0.2
ohms and an infinite charging capacity.
Nominal voltage is sufficient for supplying the voltage to DC-motor and H-bridge block.
Block parameters of a battery:
Controlled Current Source:
This block is a part of a battery subsystem. Similar to the voltage source, this
block produces an ideal current that is powerfull enough to maintain the
specified current regardless of the voltage across it.
Current Sensor:
This current sensor block represents an ideal current sensor and is used to convert
the current measured in an electrical circuit to a physical signal that is proportional
to the current. It measures the current in the battery circuit and the DC motor. The
+ve and -ve terminal across which the current sensor is inserted in to the circuit. The
3rd port outputs the physical signal. In this model it sends the signal to the controlled
current source.
Vehicle body:
The above blocks forming a subsystem which serves as a part for the whole vehicle.
4 tires are connected, where the right two tires are the rear wheels and the remaining
two are the front wheels. They are interconnected to the hub of the vehicle body block.
and their respective axles are connected accordingly. We have connected the rear axle
with the gear as we want the model to be a rear wheel drive vehicle. Here the wind
velocity port and hill-climbing angle port are connected to physical constant blocks
which is kept as zero.
Tire:
Block parameters of Tire:
Simple gear:
Block parameter of a simple gear:
This block models a gear system with fixed gear ratio with no inertia effects. However,
we can modify the messing of the gear teeth. here the follower of the base teeth ratio
has been set to 2 and the output shaft rotates in the same direction as the input shaft.
All this blocks are categorised into a single subsystem which we have names as vehicle
body block, which takes the mechanical input from the motor and controlled block into
the gear and displays the velocity at which the vehicle body moves.
Results:
Artemis Motorway 150 kmph Drive cycle graph is given as a input to vehicle model;
After running the simulation, outputs such as speed, current and soc is obtained.
The distance covered in a time period of 1068 second is also calculated which can
be seen with the help of display block.
Output of Speed:
In this graph, 2 signal is showing in a scope result.
1. Blue signal represents Vehicle body speed
2. Yellow signal represents the artemis drive cycle data.
Overlapping of this 2 graph represents the acceleration and deceleration. From the graph
it can be seen that longitudinal driver successfully maintaining speed with respective to the
drive cycle data.
Output of Current:
From the graph flow of current can be observed which is flowing from battery to the motor
with variation in a drive cycle.
SOC Output:
The SOC scope shows how the state of battery varies over the drive cycle time. The battery
was modelled to 100% of soc during the begining with pf of 1.As the simulation starts the
charge of a battery gets decreases and when the vehicle is in braking mode the uplift in the
graph shows that regenerative braking is working to maintain the battery charge. Here we
can see that after the whole simulation is over the state of charge lies at75% after 1068 sec.
Output of a distance travelled:
With the help display block distance covered can be observed, which is 8.306 km in 1068s
with sop of 75%.
Conclusions:
1. Simulink model of an Electric Vehicle is created with the help of powertrain blockset,
various parameters from the simulink library along with Artemis motorway 150kmph
drive cycle.
2. This simulation is helpful in calculating the percentage of a battery criterion before
use and after the use of simulation of EV's.
3. speed can be calculated with the simulation of EV for various drive cycle.
4. Distance travelled by vehicle in a given period of time is calculated.
i.e. Time = 1068 sec
Distance covered = 8.306km
https://drive.google.com/file/d/1Ob71v6PquTDBgnWgkauNuXjbBDz6Kw1_/view?usp=sharing