Modelling of EV using MATLAB and Simulink

Aim: -
To create an Electric Vehicle model in Simulink and simulate it.
Theory: -
An electric vehicle (EV) is defined as a vehicle that uses an electric motor or a traction motor
for propulsion as opposed to an internal combustion (IC) engine used by conventional
vehicles. Electric vehicles use electricity for power instead of fossil fuels as conventional
vehicles would and because of this difference, electric vehicles do not produce any exhaust
gases or pollution. The power needed for the operation of an EV can come from a variety of
sources such as batteries, generators, or through a collector system. Batteries fitted in to the
body of an EV are capable of high energy densities in order for them to meet the power
demands and range requirements. Generators are machines which generate electrical
energy from an input of mechanical work and are a part of the electric motor, and they
operate during braking to produce the phenomenon of 'regenerative braking'. Collector
systems are off vehicle systems which allow for the charging of an EV from homes or public
charging stations. The electricity used for charging in these systems are generated from
solar panels which can be used by the grid or by homes of EV owners so that they can
charge their vehicles more conveniently.
EVS are increasing in demand in recent years due to the need to reduce vehicle
emissions which are damaging to the environment. Government incentives and private
companies are working on schemes to quicken the adoption of electric vehicles. Since EVs
do not produce any emissions, they are more environmentally friendly than conventional
vehicles are. The generation of the electricity used to charge the vehicles also comes from
solar energy (a renewable energy source) and not fossil fuels which makes them
sustainable. EVS can meet the same performance standards of conventional vehicles and
even surpass that of theirs and this has been seen with the automotive company Tesla. The
Tesla Model 3 is the bestselling EV in the world and is capable of a range of approximately
350km on single charge. It also has an acceleration of 0-60 mph in 5.6 seconds and a top
speed of 130 mph.
In this report, I will be modelling an electric vehicle with a DC motor and battery
system using the SIMULINK software. The components I will need for my model exist as
blocks in the SIMULINK block library. I will be modelling this EV for a drive cycle and
measure the velocity characteristics and the current and SOC characteristics of its battery
system.
Components: -
The main components of an EV are:
• Batteries
• Power Converters
• Motor Controllers
• Motor/Generator
• Transmission System
• Wheels/Tires
Batteries store the electrical energy needed to power the EV in all of its systems and needs.
Power converters convert the power coming from the battery to a usable form for the motor.
This conversion can be from DC to AC or vice versa and can even be between 2 different
magnitudes of DC to DC or AC to AC. Motor controllers are electronics which control the
amount of power delivered to the motor via control signals so that the motor is running as
commanded. The motor is used for propulsion in order to move the vehicle in forward or
reverse motoring. The generator is a part of the motor and just works in the opposite method
to the motor. When braking, the vehicle can generate electricity and send this power back to
the battery, charging it (regenerative braking). The transmission system is needed for the
vehicle to change speeds as it accelerates/decelerates. The wheels are needed for traction
on the roads and depending on the powertrain, the EV may be an FWD or RWD (forward or
rear wheel drive). If a vehicle is an FWD, only the front axle wheels produce propulsion i.e.,
rotate from motor effect and if it is an RWD, the back axle wheels produce it instead. All
wheel drives (AWDs) also exist where the front and rear axle wheels work together to
produce propulsion.
System Level Configuration
To model an EV in SIMULINK, we will need to model the aforementioned components
separately and then have them work together. All the main components are available in the
library of SIMULINK blocks and we will be adding each component and configuring its
parameters to fit the requirements of the model. First, I have modelled the vehicle main
body.
Vehicle Body:
To model a vehicle's body, we need to first add the vehicle body block.

This block contains 6 ports which can be used to model the various aspects of the vehicle
body. The ports are mentioned and elaborated below:
• H- This stands for ' Hub ' and is used to connect the hubs of the wheels to the main
body of the vehicle.
• V - This is a physical signal output port which stands for Velocity and is used to
output the speed / velocity at which the vehicle is moving at.
• W - This is a physical signal input part and allows us to model a headwind ' acting on
the vehicle by giving a speed for it.
• NR - This is a physical signal output port to model the rear wheel normal forces.
• NF - This is a physical signal output to model the front wheel normal forces.
• beta - This is a physical signal input port and allows us to model the vehicle on an
inclination angle to create the effect of a hill climbing force.
If we double click the vehicle body block, we can see and modify its parameters and this
is shown in the image below:
Tires:
The tires used in this EV model are the ' magic formula tires. There are several tire
blocks that can be used for modelling a vehicle but I have used the magic formula ones
because it allows us to model the longitudinal behaviours of vehicle tires on highways.
They also allow us to model extra effects such as tire inertia, stiffness which allow for
greater accuracy of real-world conditions. The magic formula tire block is shown below:

We can see that it has 4 ports and they are;
• N- This port stands for Normal and is the physical signal input port for the normal
force acting on the tire and is considered positive in the downwards direction.
• S - This port stands for ' Slip ' and is the physical signal output port is that reports
the slip acting on the tire.
• A- This port stands for Axle and is the mechanical rotational conserving port for
the wheel axle.
• H- This port stands for ' Hub ' and is the mechanical translational conserving port
for the wheel hub through which the thrust developed by the tires is applied to the
vehicle body.
Double clicking the magic formula tire block takes us to its parameters. And I had
designed the parameters like this;

Gear:
Next, we will model the transmission system of the EV. I have decided to use a Simple
Gear block so as to simplify the transmission system parameters. This block models a
gear system with a fixed gear ratio with no inertia effects, however we can modify the
effects of the meshing of the gear teeth. The simple gear block is shown below:

Double clicking the simple gear block takes us to its parameters and I had changed the
parameters like following;
Side Shaft:
An Inertia block has been added to the workspace to provide an ideal mechanical
rotational inertia for the simple gear block. This block has only one mechanical rotational
conserving port and the positive direction of the block is from the port to the reference
point which would be the simple gear in this case. The inertia torque acts in the positive
direction are the inertia is accelerated in the positive direction. The inertia block is shown
below:

Wind & Slope:
As mentioned earlier, the velocity block allows us to model the effects of wind resistance
and road inclination through the 'W' and 'beta' ports respectively. In my model, I have
used a PS - Constant block to model the parameters of wind and road inclination on the
vehicle's motion. For the wind effect, I have given a constant signal of 5m/s and this acts
in the opposite direction to the direction of motion i.e., headwind. For the road inclination,
I have given a constant signal of 0. The block parameters of the wind and slope effects
are shown in the images below:
Velocity Subsystem:
The velocity port which outputs the velocity signal of the vehicle body block has been
modified. By default, the velocity signal that is output from the vehicle body block is
measured in miles per hour. To change these units, I have implemented a small
subsystem from the output of the velocity port. This subsystem uses the following blocks:
• PS-Simulink converter - this block will convert the physical signal of velocity to a
logic signal.
• Gain - This block uses a multiplication factor of 1.8 to convert the miles per hour
units to kilometres per hour.
• Zero-Order Hold- This block is used implement a zero-order hold sample period.
The inside of the subsystem is shown below;
Vehicle Body Subsystem:
As seen in the diagram above, the various blocks are connected to model the
vehicle body. 4 magic formula tire blocks are used as the vehicle will have 4 tires, 2 on each
axle The tires are LR, LF, RR and RF (left rear, left front, right rear, and right front). The
normal ports of each tire are connected to the appropriate NR and NF ports on the vehicle
body block. The hubs of each tire are connected together and an extra connection is made
from them to the vehicle body block. The simple gear and inertia blocks are connected to the
axle port of the tires. The wind velocity and road incline are provided with constant physical
signals of 5m/s and 0 degrees respectively. The velocity port has been connected to the
velocity subsystem and the connection from the subsystem is open to the V port. The base
port of the simple gear has been left open to the ' R ' port to take in a rotational signal. If all
these connections are made, all of these components can be selected and made in to a
subsystem shown below:

Motor:
For the EV model, I have selected to use a DC motor block as the motor. This is because
DC motors are easier to model and have fewer parameters to modify for a particular
application. For this model, a DC motor will do just fine The DC motor block is shown below:

As we can see, there are 2 sides to the block: the mechanical side on the right
and the electrical side on the left. The mechanical side has 2 ports, C and R. C refers to the
casing and the R for the rotation of the rotor which produces a torque. The electrical side has
a positive and a negative terminal for the voltages to be applied. If a positive voltage is
applied to the DC motor block from the positive to the negative terminal, a positive torque will
act from the C port to the R port. The direction of the torque produced by the DC motor can
be changed by changing the sign of the back erf or the torque constant. The part of the
mechanical side needs to be connected to a mechanical rotational reference because it will
be stationary. The R port will be connected to the open connection of the simple gear from
the vehicle body block. The positive terminal on the electrical side is connected to the
positive terminal of a power converter which in my case will be an H bridge.
Double clicking the DC motor block takes us to its parameters. The
electrical torque parameters are first considered. Here, I have chosen to parameterize the
block 'By rated power, rated speed & no - load speed'. This lets us modify parameters such
as DC supply voltage, rated load. I have kept all values default except for the no load speed
rated speed, rated load and the DC supply voltage which were changed to the values shown
in the image below:
After that we can connect the motor to the vehicle subsystem.
Power Converter:
The power converter is needed to provide power of the correct form and magnitude from one
component to another. In the case of EVs, a power converter is needed to provide a DC
voltage from the battery of the EV to the DC motor so that it can operate properly with the
required parameters. As mentioned earlier, I have used an H - Bridge motor drive as my
power converter. Its block is shown below:

The H Bridge has 2 sides to it: the left side is for the controlling of the voltage signals and the
right side is for the terminals to provide the controlled voltage to the DC motor. The left side
ports of the H - Bridge blocks are;
• PWM - This stand for Pulse Width Modulation which will provide the voltage pulses to
the H - Bridge either in the PWM or average mode.
• REF - This stand for Reference.
• REV- This stand for Reverse.
• BRK - This stand for Brake.
Opening the H - Bridge block will take us to its parameters shown below:

Controlled PWM Voltage:
Next, I have used a ' Controlled PWM Voltage ' block to provide a controlled
pulse width modulated voltage to the H Bridge block. The block will output the PWM voltage
through its ' PWM and ' REF ' ports which will feed in to the same ports found on the H -
Bridge block. If the pulse is low the output voltage is considered OV whereas if the pulse is
high, the output voltage will be equal to the output voltage amplitude which was set to 330V
in the H - Bridge block. The pulses of voltage created by this block are dependent on the
duty cycle which is the ratio of the time that the switch is ON to the time taken for 1 cycle
(which is the time for which the switch is ON and OFF). The duty cycle is set by the input of
the controlled PWM voltage block. The Controlled PWM Voltage block and its parameters
are shown below:

Controlled Voltage Source:
The input ports of the controlled PWM voltage block ore still unconnected and that
is because they required controlled voltage source to provide the voltages to produce the
voltage pulses to be fed in to the H - Bridge. For this have used the controlled voltage source
block This block is useful because it will provide the necessary voltage mot is powerful
enough to maintain the voltage at the output regardless of the current that passes through it.
This controlled voltage source block is shown below:

In this model, 2 controlled voltage sources have been used. One block is to provide the
voltage for the acceleration of the vehicle and the other is to provide the voltage for the
deceleration of the vehicle.
Here is the connection to the electrical side of the motor;
Longitudinal Driver:
The longitudinal driver block is used for giving normalized acceleration and
deceleration commands to a controller based on 2 sets of data. The first data set is the
reference velocity and the second data set is the feedback velocity. The longitudinal driver
block is shown below:

The longitudinal driver block has the following ports:
• VelRef - This stand for the reference velocity and it is the velocity data provided from
a drive cycle source.
• VelFdbk - This stand for the feedback velocity and it is the velocity data provided
from the vehicle body's velocity port which outputs the velocity data.
• Grade - This port provides a grade or inclination angle for the surface on which the
vehicle is travelling in degrees.
• Info - This port is for the bus signals which consist of block calculations e.g.,
acceleration / deceleration command, difference between reference and vehicle
speed.
• AccelCmd - This port provides the acceleration command to a controlled voltage
source.
• DecelCmd - This port provides the deceleration command to another controlled
voltage source.
The working of the longitudinal driver block is simple. The reference
velocity data coming from a drive cycle source is compared to the feedback velocity data
coming from the vehicle body block. If the reference velocity is greater than the feedback
velocity, an acceleration command will be given as an output to the controlled voltage
source. If the reference velocity is lesser than the feedback velocity, a deceleration
command is given as the output to another controlled voltage source instead. For the
acceleration and deceleration commands to be given as output signals f have used a
Simulink - PS converter block. This block is needed whenever we wish to connect a Simulink
input signal to a physical signal. In this case, the input signal is velocity data and this is logic
data which we want to convert to a physical signal i.e., voltages to the controlled voltage
source.
Grade:
The grade port of the longitudinal driver block is connected to a constant block with a
constant value of 0. This is so thot no road inclination is modelled for the simulation. This
can be seen in the image below:

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. The drive cycle will be a plot of the velocity against the
time and it is made to resemble typical driving conditions that a consumer may experience
themselves in. For instance, they can model highway driving situations, driving in urban
areas, or driving with full power etc. Drive cycles are used by automotive companies for
various testing procedures such as mileage, pollution tests, and acceleration and top speed
tests. There are various different drive cycles that are industry standard e.g., Urban
Dynamometer Driving Schedule (UDDS), FTP 75.
In my EV model, a drive cycle is used as the reference velocity data for the
longitudinal driver block to send acceleration or deceleration commands according to the
drive cycle. There are 3 ways of implementing a drive cycle. One method is to create or own
drive cycle with a spreadsheet of velocity data in one column and time data in another
column. Another method is to use a signal builder block and create signals that represent the
velocities at which the vehicle should travel and the durations for which those velocities are
to be maintained. The last method is to use the industry standard drive cycles which are in -
built in to the SIMULINK library. In my case, I have used on industry standard WOT drive
cycle. This drive cycle stands for ' Wide Open Throttle ' and it models the situation where the
vehicle is made to accelerate at full power and maintained at a particular speed and made to
decelerate bock to rest.
The drive cycle block is shown below:

Drive Cycle Block parameters shown below;
As we can see, with the ' WOT ' drive cycle, we can modify the start
time, time to start deceleration and the entire duration of the drive cycle. I have used a start
time of 5 seconds meaning that the vehicle will begin acceleration after 5 seconds of starting
simulation. I have used a nominal reference speed of 30m/s and this refers to the maximum
speed the vehicle should achieve. I have set the deceleration to begin at t = 20 seconds and
the whole cycle is set for a duration of 30 seconds. The input and output velocity units are
both set to m/s.
The plot below shows the custom WOT drive cycle I have created:
Once the drive cycle parameters have been set as shown above, the output port of the drive
cycle can be connected to the reference speed port of the longitudinal driver block. If all the
parameters have been set as discussed, the connections can be made as shown in the
image below:
Battery System
Battery:
The battery will be the energy store of the EV and will contain the electrical energy
in DC form and provide this anergy to the DC motor for it to operate. The battery block used
is a simple one and considers only the basic parameters The battery block is shown below:

The battery parameters are showing below;
Controlled Current Source:
The controlled current source block is a part of the battery system used in the EV
model. Similar to the controlled voltage source, this block will represent an ideal current
source that is powerful enough to maintain the specified current regardless of the voltage
across it. The controlled current source block is shown below:

Current Sensor:
The 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. This block is used to measure the current between the battery circuit (controlled
current source) and the DC motor. The current sensor block is shown below:

The positive and negative terminals represent the terminals across which the current sensor
is inserted in to the circuit. The third port outputs the physical signal and in my model, it will
send the signal to the controlled current source.

From the image above, we can see that the current sensor is embedded in between the
electrical side of the DC motor and the H - Bridge. The current sensor can be connected
from its physical signal port to the remaining components in the battery system including an
electrical reference block. This is shown in the image below:

SOC & Current:
SOC stands for state of charge and it is a measurement of the available charge
in a battery. When a battery is fully charged, it is considered to have a 100 % charge and
conversely 0 % charge if fully discharged. In this EV model, I want to measure the current
and the SOC of the battery as the simulation is run. For this, I have used a scope block
which shows the output signal we wish to measure as a plot against time. 2 scopes have
been used, one for the current and the other for the SOC. In order for this to be measured,
we need to use a PS - Simulink converter ' block. This is because the current signal is a
physical one and we are measuring it as a logic signal in the SIMULINK workspace.
SOC Subsystem
To measure the state of charge of the battery, a subsystem was created of various
blocks. The first block is the ' Rate Transition ' block and it is used to handle data transfer
between different rates and tasks. Next, a ' Gain ' block is used in order to multiply or divide
the signal coming from the rate transition block. In this case, the gain block will divide the
current signal with the ampere rating of the battery which has been taken as 80Ah multiplied
by 3600 (seconds in an hour). This is shown in the gain block parameters below:

Then, a ' Discrete - Time Integrator ' block is used to perform a discrete integration of the
current signal with respect to the time. A constant block is used to represent the initial SOC
of the battery. Assuming that the battery is always fully charged when performing a
simulation, I have altered the constant block with a value of 1 representing 100%. Next, a '
sum ' block is used to perform addition and subtraction operations. The signal from the
discrete time integrator block will be subtracted from the constant block representing 100 %
charge. These components are connected as shown below:
These blocks are then made in to a subsystem called ' SOC Estimate ' and linked with the
battery circuit using the PS Simulink converter block. 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.
Another scope is used to plot the output signal of the SOC from the SOC subsystem. This is
shown in the image below:

Speed Measurement:
In order to measure the speed of the EV model, I needed to use the scope block once again.
I modified the scope block to have 2 input ports where one port takes the output velocity
signal from the vehicle subsystem block and the other port takes the output signal from the
drive cycle to the reference velocity port on the longitudinal driver block This has been done
so that the scope can show us the plots of the reference velocity and the actual velocity of
the vehicle to see how they compare with each other.
Distance Measurement:
I have used the scope block and mathematical operator blocks to measure the
distance travelled by the vehicle according to the drive cycle data. The area under a velocity
time graph tells us the distance travelled by an object and so in my model. This means that
the integral of the velocity with respect to time, gives us the distance travelled. So, I have
implemented the integrator block to integrate the velocity signal that is output from the
vehicle subsystem. From the integrator block, I needed to use the ' Divide ' block along with
a ' Constant ' block having a value of 3600 in order to convert the divide the integrated speed
signal which is in kilometres per hour by 3600. This will give us the distance travelled in
kilometres. And a display is connected to show the distance travelled.
These are connected as shown below:

After doing all connection we can simulate the model.
Final Model:
Observations: -
I ran the WOT drive cycle for my EV model and took the outputs given from the speed,
current and SOC scopes. The distance travelled by the vehicle in the drive cycle was also
measured using the display block. Before running, the ' Stop Time ' for the simulation was
first set to 30 seconds which is the duration of my customized WOT drive cycle.
Speed Scope:
From this scope, we can see 2 signals. The blue signal represents the
reference signal which originates from the drive cycle data whereas the red signal shows the
actual velocity of the vehicle. The WOT drive cycle had been customized so that the vehicle
begins acceleration under the WOT condition (full power) at t = 5 seconds. This is supposed
to be maintained till t = 20 seconds when the vehicle is supposed to begin deceleration.
From t = 20 seconds to t = 30 second, the vehicle speed is back to 0m/s i.e., rest. Because
this is a reference signal, all the commands are instantaneous. This is why the increase and
decrease in speed is very sudden within a fraction of a second. However, this effect will not
be observed on the actual velocity of the vehicle. This is because in real world conditions,
there are more considerations to factor in which will not make it possible for a vehicle to
accelerate and decelerate as instantaneously as the drive cycle commanded. In the real
world, the effects of rolling resistance, drag and road inclination make a difference because
their presence would cause the vehicle's motion to deviate from the drive cycle commands.
Other factors include, the vehicle's inertia and the inertia of the transmission system.
Observing the vehicle's actual velocity, as commanded, the vehicle begins
at rest before accelerating under the WOT condition at t = 5 seconds. This acceleration is
maintained till t = 20 seconds as the drive cycle commanded. At t = 20 seconds, the vehicle
achieves a top speed of 13.1m/s. After t = 20 seconds, the vehicle begins to decelerate
gradually till t = 30 seconds where the vehicle finishes with a velocity of approximately
3.1m/s. As mentioned earlier, the actual velocity could not match the drive cycle commands
perfectly and this is due to several factors which were discussed above. In my model, I have
not modelled a road inclination but I have used a wind velocity of 5m/s. I compared the effect
of this wind resistance on the top speed of the vehicle to when there was no wind resistance.
The effect was very insignificant, only affecting the top speed by 0.5m/s. However, the
vehicle velocity has accelerated and decelerated as the drive cycle commanded. Obviously,
the model is limited to the simulation time allotted. So, if a longer simulation time is used, the
vehicle may reach a higher top speed and may even decelerate back to rest.
Current Scope:
The current scope shows how the current flowing from the battery to
the motor varies with the drive cycle time. As we can see, initially the current flowing through
the circuit is 0A and this corresponds to the drive cycle commanding the vehicle to be at rest
for this time period. At t = 5 seconds, when the vehicle is commanded to accelerate, the
current instantaneously increases to a maximum current of 236.1A. This maximum current is
achieved because at t = 5 seconds, the vehicle accelerates at maximum power under the
WOT condition and so this will demand a high current from the battery. From t = 5 seconds
to t = 20 seconds, the current decreases gradually to 130A. The current must have
decreased over time because as the vehicle was accelerating, it required lesser current from
the battery to continue accelerating. The highest current is always required when
accelerating from rest due to the inertia of the vehicle. But once the vehicle is already in
motion, it requires significantly lesser energy to continue accelerating.
After t = 20 seconds, the vehicle decelerates, causing the current to
drop instantaneously to the negative axis to a value of -105A. There is now a negative
current flowing due to regenerative braking. When the vehicle decelerates, the throttle is no
longer applied and so the kinetic energy from the motion is converted to electrical energy fed
back to the battery of the EV. This reverse flow of current is what causes the negative
current measurement. From t = 20 seconds, the deceleration continues, however the current
flowing through the battery decreases in magnitude. This is because at t = 20 seconds, the
vehicle had reached its top speed and hence its maximum kinetic energy. So, at that point
there was more kinetic energy which could be converted to electrical energy for regenerative
braking. However, as the vehicle decelerates, there was lesser energy available for
regenerative braking causing the magnitude of the current to decrease. The polarity of the
current hence moves towards the positive direction because regenerative braking happens
lesser and lesser until the vehicle comes to rest. At t = 30 seconds, the vehicle is still
decelerating and finished with current measurement of -24.8A showing that regenerative
braking is still occurring.
SOC Scope:
The SOC scope shows how the state of charge of the battery varies over
the drive cycle time. The battery was modelled to begin with an SOC of 1 (100%) and so
when the simulation begins, the SOC is at 1 until t = 5 seconds. This is because the drive
cycle commands the vehicle to be at rest for that duration and so no discharge occurs from
the battery. At t = 5 seconds, the vehicle is commanded to accelerate under the WOT
condition and so the SOC of the battery decreases. Because the vehicle is accelerating at
full power, the SOC falls from 1 but the rate of discharge decreases over the acceleration
period eventually settling at a minimum SOC of 0.9909 at t = 20 seconds. This corresponds
to the current flow from the battery because as the vehicle accelerates, lesser energy is
demanded to Increase the speed. As mentioned before, the greatest discharge occurs when
the greatest current flows from the battery and this is during the initial acceleration period. As
the vehicle speed increases, the acceleration decreases causing the current and hence the
rate of discharge to decrease but in a mild fashion. At t = 20 seconds, the vehicle is
commanded to decelerate and so the vehicle velocity decreases. This results in regenerative
braking to occur which causes a negative flow of current back to the battery. Because this
effect charges the battery, the SOC of the battery increases during the deceleration period.
The SOC increases very gently from 0.9909 to 0.9929 and this is because the gets charges
by the regenerative braking effect. The negative flow of current corresponds to the increase
in the SOC of the battery. Since the vehicle is commanded to decelerate until t = 30
seconds, the vehicle speed decreases but does not reach 0m/s, so the vehicle is under
regenerative braking for the entire period after t = 20 seconds.
Distance Travelled:

From the image above, we can see that the display block has measured the distance
travelled by my EV model for the customized WOT cycle to be 0.05219km. This
measurement seems appropriate and correct since the WOT drive cycle is very short in
duration and only requires acceleration for half of the drive cycle's overall duration. The area
under the velocity time graph tells us the displacement of an object. From looking at the
speed scope, a rough calculation indicates that this distance measurement is correct.
Displacement is defined as distance in a given direction and is a vector quantity
meaning it has both size and direction. So, if the velocity data in a drive cycle was negative,
this would indicate that the vehicle is moving in the reverse direction and this would
correspond to a negative displacement. The display block would indicate the same if the
velocities in the drive cycle data were of that nature.
Conclusion: -
In conclusion, the EV model has been created with the necessary block
components using the SIMULINK software and the model has been simulated for a
customized WOT drive cycle. The simulation has produced results of the velocity of the
vehicle, current flowing from the battery, and the SOC of the battery as well as the distance
travelled by the EV. Since the EV model was parameterized to simulate averaged voltage
pulses in the H - Bridge and Controlled PWM voltage blocks to be fed in to the DC motor, the
simulation was run very quickly within a matter of seconds. The EV model was able to follow
the commands given by the reference velocities from the drive cycle data, although it could
have followed the reference signals more closely. The discrepancy between the reference
velocity and actual velocity of the vehicle may be attributed to a variety of factors e.g.,
vehicle inertia, transmission system, transmission inertia. If the EV model was designed in
such a way as to improve upon those factors, the model would follow the reference signals
more closely and would improve the performance characteristics as well. The distance
travelled by my EV model was measured at 0.05219km and seems to be an appropriate
value based on the WOT drive cycle used.
I had observed that the SOC of the battery used in my EV model did not get discharged in a
way I had expected it to. This could be because the drive cycle commands did not push the
EV model to its limits or it could be due to the fact that the battery model was very efficient
and was suitable for the driving application. My EV model had also included some actual
features of EVs such as regenerative braking and this was evident in the current - time and
SOC - time graphs whenever the EV decelerated. If the duration of the WOT drive cycle was
modified to be longer, I could have seen my EV model exhibit its true performance
characteristics. For instance, the EV model may achieve its top speed and it may also have
been possible to see the time it takes for the vehicle to decelerate from that top speed and
hence the time taken for the acceleration e.g., 0 to 60 kmph.