Final Project: Design of an Electric Vehicle

1>>Ans: A new study related to vehicle engineering says that by coming 2025, there will be a major transformation in the automobile sector. Many automakers are working to charge the vehicle technologies, the major area is to decrease the pollution and use electrification in the upcoming vehicles, the researchers and automakers are connected working to reduce CO2 emissions. New technology like high capacity lithium-type batteries will be a major energy source for the propulsion of electric vehicles. At present, with the new technologies, some manufactures have launched their products which are Telsa, Chevy Bolt EV, and Nissan Leaf which are fully electric battery-based cars.

The power and performance of electric vehicles is depending upon the two machines are a brushless DC motor or an induction motor. The DC is replaced by DC brushless motors and induction motors. Also, the lead-acid battery is replaced by lithium-ion batteries for EVs.Because the future of both the components induction or brushless DC Motor depends upon their demand and uses.

The most important components of electric vehicles are:

1) Auxiliary Battery: In an electric vehicle the auxiliary battery provides electricity to power the vehicle accessories

2)Traction Battery Pack: The traction battery pack is also known as Electric Vehicle Battery (EVB) which is used to store electricity. Some examples of traction battery energy storage systems are given below:

3)Lithium-Ion

4)Nickel Metal Hydride

5)Lead Acid

6)Ultra Capacitors

7) DC-DC Converters: Basically DC-Dc converter is an electronic device that is used to convert higher voltage dc power from the traction battery pack to the lower voltage dc power. The converted power is used to run the vehicle accessories. It is used to recharge the auxiliary battery.

8)Electric Traction Motor: Another important component is the electric traction motor and this device is used to provide motive power to the wheels.

9)Onboard Charger: Takes the incoming AC electricity supplied through the charge port and converts it to DC power for charging the traction battery. It monitors battery characteristics such as voltage, current, temperature, and state of charge while charging the pack.

10)Power Electronics Controllers: This unit manages the flow of electrical energy delivered by the traction battery controlling the speed of the electric traction motor and the torque it produces.

11)Charge Port: The charge port allows the vehicle to connect to an external power supply in order to charge the traction battery pack.

12)Thermal System: This system maintains a proper operating temperature range of the electric motor, power electronics, and other components.

MATLAB Modelling of Electric Car:

Vehicle Technical Specification:

• Vehicle Weight(Kg):1147
• Number of Wheels per axle:2
• Total Length:4.127m or 4,127mm
• Total Height:1.487m or1,487mm
• Total Width:1.746m or 1,746mm

By using MATLAB SIMULINK System Block for Electric Vehicle design and the whole design is as:

Important Simulink Block used in Electric Vehicle Design are as follows:

• Drive Cycle Source:1
• Constant:3
• Longitudinal Drive:1
• Controlled Voltage Source:2
• Controlled PWM Voltage:1
• Solver Configuration:1
• Electrical Reference:2
• H-Bridge:1
• DC Motor:1
• Mechanical Rotational Reference:1
• Current Sensor:1
• Battery:1
• Controlled Current Source: 1
• PS-Simulink Converter:4
• vehicle Body:1
• Tire:4
• Simple Gear:1
• Interia:1
• GOTo:2
• PS Constant:2
• Gain:2
• Zero Order Hold:1
• Rate Transition:1
• Discrete Time Integrator:1
• Sum:1
• Integrator:1
• Divider:1
• Display:1
• Scope:4

MODELLING OF VEHICLE BODY SYSTEM:

The Vehicle Body block represents a two-axle vehicle body in longitudinal motion. The vehicle can have the same or a different number of wheels on each axle. The block consists of body mass, aerodynamic drag, road incline, and weight distribution between axles due to acceleration and road profile. In optionally we can include pitch and suspension dynamics. The block has an option to induce an externally defined mass and externally defined interia. The mass inertia and center of gravity of the vehicle body can vary over the course of simulation in response to system changes. In a given block:

1. NR: It is a physical signal output that is connected to the rear wheel axle. For this model, it is connected with a normal force of the rear tire.
2. NF: It is a physical signal output that is connected to the front-wheel axel and for this particular model it is connected with the normal force acting on a front-wheel tire.
3. Beta: Beta is basically a road inclined angle, here we can define a constant value for road angle inclination.
4. H: This port is a horizontal motion of the vehicle's body. This connection will be connected with all four hubs of the wheel for finding the thrust generated by the tire.
5. V: This port is the vehicle's longitudinal velocity.
6. W: It is a headwind speed. Basically, we will define a particular wind speed by adding a constant block.

For setup of vehicle body just double click on the vehicle body and enter as per requirement. Here I have done some changes in the vehicle configuration. Basically, I changed the vehicle mass, length, and frontal area.

Detail input of vehicle body.

Main Setting:

• Mass:1147kg
• Number of wheels per axle:2
• The horizontal distance from CG front axle:1.854m
• The horizontal distance from CG to the rear axle:2.2730m
• CG height above ground:0.5m
• Externally defined additional mass: OFF
• Gravitational acceleration:9.81m/s
• negative normal force warning: OFF

Drag Setting:

• Frontal area:2.21m^2
• Drag Coefficient:0.20
• Air Density:1.18kg/m^3

Pitch Setting:

• pitch Dynamics: OFF

Variable Settings:

• Beginning Value of Velocity: 0m/s

Other Connected detail:

• Wind Velocity:2.22m/s
• Road Incline: 0

For calculating the velocity here, we have created a subsystem that is LOG mph, this block basically consists of PS Simulink converter, Gain, Zero order Hold.

• Gain Block: 1.61 and it multiply input value with constant input.
• Zero Order Hold: 0.01, the Zero Order hold black holds its input for the sample period you specify.

Tire Modelling:

The Tire block models are a tire with longitudinal behavior given by the Magic Formula an empirical equation based on four fitting coefficients. The Block can model tire dynamics under constant or variable pavement conditions. The Tire block models the tire as a rigid wheel-tire combination in contact with the road and subject to slip. When torque is applied to the wheel axle, the tire pushes on the ground and transfer the resulting reaction as a force back on the wheel, this action pushes the wheel forward or backward. If you include the optional tire compliance, the tire also flexibly deform under load. The Figure the forces acting on the tire are as shown below:

Where

Fx= Longitudinal Force Exerted on the tire at the contact point.

Fz=Vertical load on the tire.

Omega: Wheel angular velocity.

Vx=Wheel hub longitudinal velocity.

In the particular block,

• N: Normal force acting on the tire and connected with NR of the vehicle body.
• S: Slip between the tire and road connected with Gotot block.
• H: Hub and it is used to find the thrust created by the tire and it is connected with H input of vehicle body also including all four hubs of the wheel.
• A: Axel and rear axle are connected with the final drive system and the front axle is connected with the left and right wheel.

In the tire block, we can change the parameter:

Main Settings:

• Parameterize by: Load dependent magic formula coefficient it is basically specifying the parameters that the load-dependent.
• Tire nominal vertical load: This is basically a normal force on the tire (FCO). So, for this particular model, the normal force I have taken is 4000N.
• Magic formulae C, D, E, BCD, H, and V are default. Basically, it is a load-dependent magic formula coefficient.

Geometry Setting:

• Rolling Radius: 0.32, it is unloaded tire-wheel radius(rw)

Dynamic Setting:

• Inertia: Specify inertia and initial velocity which depends upon stiff, dampened spring and deforms under load.
• Tire Inertia: 0.5kg*m^2 and it is rotational inertia low of the wheel-tire assembly.
• Initial Velocity: 0 rpm and it is an initial angular velocity. omega of zero of the tire.

Rolling Resistance Setting:

• Rolling Resistance: On basically, it includes rolling resistance.
• Resistance model: By using constant coefficient we are neglect rolling resistance.
• Constant coefficient: 0.015 the value should be greater than 0 and it is a coefficient that sets the proportionally between the normal force and the rolling resistance force.
• Velocity Threshold: 1*e^-3 m/s basically this input is a velocity at which the full rolling resistance force is transmitted to the rolling hub.

Advance Setting:

• Velocity Threshold: 0.1m/s as I keep this value ass default and this value should be positive because it is wheel hub velocity below which the slip calculation is modified to avoid singular evolution at zero velocity.

Inertia:

This block generally represents the mechanical rotational element.

T = J*((dw)/(dt))

where,

T= Inertia torque.

J=Inertia

Omega= Angular Velocity

T=Time.

So here the inertia value is 0.01kg/m^2 and this block is connected with the rear axle and final drive ratio to find the inertia because the axle and gear are mechanical rotating devices.

Simple Gear:

Simple Gear is a final drive ration which is a gearbox that constrains the connected driveline axes of the base gear and the following gear.

B: The output B base gear is connected with the input of DC motor R, it is a rotational mechanical conserving port.

F: The output F follower gear is connected with the rear axle. It is also a rotational mechanical conserving port.

In simple Gear Block, we can also do some changes according to our need and is as follows:

Main Setting:

• A follower to base teeth ratio: 2, the value should be positive and it is a fixed ratio FB of the following gear to the base gear.
• Output shaft rotates in the same direction as the input shaft, it is depending upon the direction of the follower and bias gear.

Meshing Losses:

• Friction model: From the drop-down, we can select constant efficiency which calculated the reduced torque transfer by a constant efficiency factor.
• Efficiency: 0.89, here we can change the efficiency depending upon our need. Basically, it is a torque transfer efficiency between the base gear shaft to the follower gear shaft.
• Follower Power threshold: 0.001WQ, it is an absolute value of the follower shaft power above which the full efficiency factor is in effect.

Configuration Battery and SOC:

Battery:

Here we will add a battery system to run the vehicle system and vehicle too. So for that added battery from Simulink library.

Here I have used a simple battery model for a particular battery there are some changes in the input.

If we are selecting battery charge capacity as finite from the drop-down menu then this basically describes the series resistor and a charge depending on voltage source and for this, a particular equation is which is dependent upon the voltage as a function of charge.

Where,

• SOC is the ratio of current charge to-rated battery capacity.
• VO is the voltage when the battery is fully charged at no load, as defined by the nominal voltage parameter
• Beta is a constant that is calculated so that the battery voltage is v1 when the charge is AH

The connection of the battery is as follows, the negative terminal is connected with the ground and controlled current source physical port to the positive direction that indicates the flow. The positive terminal is also connected to the controlled current source of electrical conserving ports.

Controlled Current Source:

The controlled current source block represents an ideal current source that is powerful enough to maintain the specified current through it regardless of the voltage across the source. In this particular block, the two-port is connected with the battery, and one electrical conversing port is connected with the PS Simulink converter to the rate transition block and scope block.

Electrical Reference:

The Electrical Reference block represents an electrical ground. For this model, this block is connected with a battery negative terminal.

PS Simulink Converter

The PS Simulink Converter block converts a physical signal into a Simulink output signal. Use this block to connect outputs of a physical networking diagram to Simulink scopes or other Simulink blocks.

Now for calculating the soc we have to create a subsystem that will consist of rate transition, Gain, Discrete-Time Integrator, Constant, and Sum Blocks.

Rate Transition:

It is used to transfer data from the output of a block operating at one rate to the input of a block operating at a different rate.

Input Signal: Input Signal to transition to a new sample rate, specified as a scalar, vector, matrix, or ND Array.

Output Signal: Output signal is the input signal converted to the sample rate you specified

A Basic input for this block is as follows:

Gain Block:

The Gain Block multiplies the input by a constant value. The input and the gain can each be a scalar, vector, or matrix

Here gain value is the multiplication element and the input is 1/(50*3600) where 50 is battery amperes and 3600 is second

Discrete Time Integrator:

The discrete-time integrator block is used for

• Define initial conditions on the block dialogue box or as input to the block.
• Define an input gain Value
• Output the block state.
• Define upper and lower limits on the integral
• Reset the state with additional reset input.

Sum Block

The sum block performs addition or subtraction on its inputs. In this block, the negative terminal will be connected with a discrete-time integrator and the positive terminal with a constant.

Detail about Electrical System:

DCMotor:

The DC Motor block represents the electrical and torque characteristics of a DC motor using the following equivalent circuit model.

here in this system, the positive terminal is connected with the current sensor negative terminal and the negative terminal is connected with the negative terminal of the H Bridge.

R is DC Motor which rotor is connected with the mechanical rotational port that is simple gear whereas C is DC Motor case and it is connected with mechanical rotational reference.

A Basic configuration of the DC motor is as follows:

Here for the particular model l configure in DC Motor and try to change a basic setting in electrical torque.

• No-load Speed: 11000rpm, this is the speed of the motor when not driving as a load.
• Rated Speed:10500 rpm, this is the speed of the motor at rated mechanical power level.

Another Mechanical detail of DC Motor is as follows:

• Rotor Inertia: Its a resistance of the rotor to change in motor motion
• Rotor Damping: It should be zero because it is energy dissipated by the motor.
• Initial Rotor Speed: This is the starting speed of the motor that at what speed the motor will start.

H-Bridge:

The H bridge block represents an H Bridge motor drive.

Simulation mode and load assumption settings:

• Power Supply: The Power supply is the default mode.
• Simulation Mode: here I have selected averaged mode and this mode has two load current characteristics options.

Smoothed

Unsmoothed or Discontinuous:

• Regenerative Braking: Always enabled this option can be used when the controller always sets the REV Flag to ensure regenerative braking.
• load Current Characteristics: Smoothed is a default option and it assumes that the current is practically continuous due to load inductance.

Input Thresholds:

• Enable Threshold Voltage: 1.5v, this is the above value of PWM at which H Bridge start.
• PWM Signal Amplitude: 5.0V this is the amplitude of the signal at the PWM input. Here I have used it as the default mode.
• Reverse Threshold Voltage: 0.1ohms
• Braking Threshold Voltage:0.005 ohm

Detail about connection:

• PWM: Pulse Width Modulation Signal
• REF: Reference, it is an electrical conversing port associated with the floating zero volts
• REV: Reverse, it is an electrical conserving port associated with the voltage that controls when to reverse the polarity of the H Bridge block output.
• BRK: Brake, is an electrical conserving port associated with the voltage that controls when to short circuit the H Bridge block output.

Here PWM output port is connected with the PWM input port of controlled PWM Voltage. The REF and REV ports are connected with the REF port of the controlled PWM voltage port. The BRK port is connected with a controlled voltage source.

The +ve terminal is connected with the +ve port of the current sensor and the -ve port is connected with the -ve port of the DC motor.

Controlled PWM Voltage:

The controlled PWM Voltage block represents a pulse width modulated voltage source. The input detail is as given below.

Detail about the connection

• ref+ - positive terminal this port is a positive electrical reference and connected with controlled voltage source positive terminal.
• ref- - Negative terminal this port is a negative electrical reference and connected with the negative terminal of the controlled voltage source.
• PWM- Pulse width modulated signal, this port is electrical reference port and connected with PWM port of H bridge.
• REF - Floating Zero volt reference this port is connected with the REF of the H Bridge port

Controlled Voltage Source:

The controlled voltage source block represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regarding the current flowing through the source. The Block has one physical signal input and two electrical conserving ports associated with its electrical terminals.

Solver Configuration

Solver configuration is used to begin the simulation and it's needed to solve the Simulink model. Here it is connected with controlled PWM Voltage and H Bridge Negative connectivity by combination with electrical reference.

longitudinal Driver:

The Longitudinal Driver block implements a longitudinal speed tracking controller.

The details of input are as given:

Detail about parameters:

• Controller Type: PI is a proportional-integral control with tracking windup and feedforward gains.

• Reference and Feedback unit:m/s

Detail about connection:

• VelRef: Reference vehicle velocity is connected with speed result block. Its unit is m/s
• VelFdbk: longitudinal vehicle velocity is connected with integrator block continuous time integration of VelFdbk signal
• Grade: Road grade angle is connected with constant block so that we can use our specific value, here the value is 0 which I have used.
• Info- Bus signal, here I have used this signal to terminate the signal block, basically it's an output port.
• AccelCmd: Commanded vehicle acceleration is connected with controlled voltage source input signal by combination with PS Simulink converter.
• DecelCmd: Commanded Vehicle Deceleration is connected with another controlled voltage source signal by combination with PS Simulink converter and to check the output result I have connected with scope block.

Drive Cycle Source:

For this particular electrical vehicle here I have used the FTP75 drive cycle. The Plotted drive cycle is as followas:

The connection drive cycle refused is connected with the Velref of the longitudinal driver and to the scoop results which generated the vehicle reference speed.

Distance Calculation:

here the main block is an integrator, divider, time block and for the result, we have to use a display block that will display the distance.

Details about connection:

Integrator: The output port of the vehicle body is connected with the integrator block

Divider: The output of the integrator block is connected with the divider where it will be divided by time to get the final output.

Time: The output of the time block is connected with the divider block, here timer is taken as 3600s

Results:

1. Longitudinal Driver/Decel:

positive Duty Cycle =11.779%

Negative Duty Cycle = 88.310%

2) SOC%:

• High:7.7410*e^-01
• low:-5.69*e^-01
• Amplitude:1340*e^+00
• Fall Time:1.608 ks
• Slew rate:-666.517m/s

3) Current: The starting of current is 18.917s and we can see that the current is constant for 602.051s starting from 1385.868s to 1987.918s.

Transition Level:

• High: 1.837*e^+02
• Low:1.121*e^+02
• Amplitude: 7.612*e^+01
• Rise time:1.905s
• Positive Slew rate: 50.231per sec
• Fall time: 6.173s
• negative Slew rate:-21.216 per sec

Cycle Level:

• Period:72.570s
• Positive Duty cycle:40.173%
• negative Duty Cycle:60.17%

4) Speed: Here the yellow graph indicated the vehicle speed whereas the blue graph indicated the reference speed.

As we can see the difference in time between the reverence speed versus vehicle speed is basically starting of vehicle speed. As we can also see that the reference speed starts at 20.097s whereas vehicle speed starts at 22.142sec and the total difference between these two is are2045sec

Transition Level:

• High:1.373*e^+01
• Low:1.283*e^-01
• Amplitude:1.360*e^+01
• Rise Time:26.988s
• Slew Rate:646.431Ks
• Fall Time:29.976s
• Slew Rate:-476.104ks

Conclusion:

>> The total distance travel by vehicle is 5.318m/s or 19.1448kmph depending upon the FTP75 drive cycle and the total time for simulation was 2474 sec

>> The Battery is having 300V which is a nominal voltage and the battery ampere per hour rating is 50 by which we can calculate the SOC of the battery

>> The DC Motor is used to run the rear axle of the vehicle and when the car is with no load condition then the motor operating RPM is 11000 and when the car is running at some load or we can say that some rated speed then the motor RPM is taken as 10500. The Voltage supply to DC Motor is 300v.