Final Project: Design of an Electric Vehicle

THEORY

An Electric Vehicle (EV) is a vehicle  that user one or more electric motors or traction motors propulsion.An electric vehicle may be powered through a collector system by electricity from off- vehicle sources, or may be self-contained with a bettery,solar panels, fual cells or electrical generator to convert fual to electricity.EVs include, but are  not limitet to ,road and rail vehicles, surface and underwater vessels, electrical aircraft  and electric spacecraft. 

Component of an EV

• EVs no neet for the fual  engine and gear transmition, the two of the most crucial components for internal combustion vehicles.
• An electric powered car has three primary components-Battery,motor controller, and the electric motor.

(1) Battery: the battery of the electric car can be charge through the use of the ordinary grid  electricity at  a specialized power station. But aside from the conventional lithium -ion battery technolgies, there are also other major battery technologies, there are also other major battery technologies which can be use for the electric car.

• Lithium -ion battery

This battery technolgy gives extra perfomance and range. however, it also carries the higer price tage. lithium -ion battery are  higher then Lead acid  and Nickel metal. These are also the batteries  sued in digital cameras  and smart phones.

•  Lead Acid Batteries

This battery technology is the most popular. it is also the cheapest among the battery technologies . which good about it is 97% recyclable.

• Nickel  metal Hydride Batteries 

This battery technology provide higer output and better perfomance but its cost much more then lead acid batteries.

(2) Motor controller

The motor controller of the electric car addministers it complete opertation distrubution of its  power at any given moment. its acts as a floodage between the motor  and batteries. its help to moinitor and regulates all key perfomance indications such as the vehicles operators.motor battery and acceleator pedal. It has a  microprocessor which can limit or redirect current. it s used to either improve the mechanical performance of the  car or suit the operators driving style. There are also more refined controllers which are capable  of the grator accuracy and thus, higher efficiency.

 Electric motor

Unlike a gasoline engine with lots of moving parts, a motor only has one moving part. this makes it a very realble

source of motive power. choosing an electric motor depend on the cars system  voltage. They can be structured to use eitherAc or DC current. AC motors are less expensive  and lighter compared to DC motors. There are also more common and they tend to suffer from less mechanical wear and tear.however, AC technology requires a more refind or sophisticated motor contrller.

PROCEDURE

vehicle body subsystem

• The vehicle is assumed to be a front axle driven (4wheels -2 on each axle)
• The wheels are modelled using  simple Tire (magic formula ) simulink blocks.

• The  (N) port of the tire corresponds to Normal Reaction the acting on it.
• The (A) port corresponds to the Mechanical Rotational conserving port for the wheel axle. thus both the wheels on the same axle should from a connection through their respective A ports.
• connection H corresponds to the Mechanical Translational conseving port for the wheel hub through which the thrust developed by the tire is applied to the vehicle.Thus, all the 4 wheels from a connection through their.
• respective H port and this is in turn connected to the translational hub of the vehicle body. the connection S represents the output port for slip of the tire.

• The tire are parameterrized by peak longituditional Force and corresponding slip.
• The other block parameters such as - rated - vertical load, peak longitudinal force at rated load and slip at peak force at rated load- are kept with there default values.
• the tire radius given as 0.3m.
• The tire is kept as 1kg-m^2 Also, the rolling resistance is given with a constant  coefficient of 0.015.

This Two axle (4 wheel ) assembly is now connected to a velocity body simscape block

• This block basically represents a two -axle vehicle body in longitudinal motion. The block accounts for-
•  Body mass.
• Aerodynamic drag.
• road incline.
• weight distribution between axles due to acceleration.
• Road profile.
• Here, the connection H is the mechanical translational conserving  port hub.
• NF & NR correspond  to the normal reaction forces on out put ports for front axle wheels respectively.
• connection V represents the actual output translational velocity of the vehicle.
• beta is the road inclination  angle and W corresponds to the headwind speed(headwind dirrection opposite to that of vehical.
• The gross weight is given to be 1200kg
• The geometric parameters of the vehicle are given as:-

to account for  proper drage force on the vehicle,for related parameter are kept as

The pitch dynamic for the vehicle are not considered  for this simulation the complete sub system is shown below,

The input for this subsystem is taken as the Rotatioanal speed of the motor. This input is fed to the front axle through a simple Gear representing the Final Drive ratio of 3.73 Here, the rotational direction of the output shft is kept the same as that of the input shaft. Also,no meshing losses are considered for simulation.

(2) DC Motors

• Simulink provides an inbuild model block for DC motor which converts electrical input into mechanical Rotational output. 

         Note : Here, the blue colour corresponds to the elecrical side of the motor and green colour corresponds to the                        mechanical side.

• Here, the motor field type is kept as permanent magnet and the model parameterization is done by rated load and speed.
• the armature inductance and the mechanical parameters are givn their default values.
• All the other parameters are changed as shown below.

• The connection R represents the Rotor (rotational output) while the connection C is for the Casing (stationary ) Thus, the R port is connected to the input of the vehicle subsystem created earlier. The C port is connected to a Mechanical rotational reference.
• The + and - terminales of the motor are connected to the motor controller. if these terminals are  directly connected to a battery, the required DC motor will run on the rated capacity of the battery.this will eventually result into no control over the DC motor and the vehicle will run at top speed throughout the simulation.

(3) Motor controller

• H - Bridge circuit

• This block represents an H -bridge motor drive. The block can be driven by the controlled PWM voltage block in PWM or Averaged mode.
• in PWM mode, the motor is powered if the PWM port voltage is above the enabled threshold voltage.
• in Averaged mode, the PWM port Diverded by the PWM signal amplitude parameter defines the ratio of the on-time to the PWM period.
• connection REF is for the reference input. This combined with the PWM connected will from the pulse input for the H-Bridge.
• Here the REF input is connected to the electrical reference(ground)
• Connection REV corresponds to the reversevmotion of the motor which essentially means, the backward motion of the vehicle. Here, the backward of the motion vehicle is not accounted for and so , the  port is connected to the Electrical reference.
• connction BRK is for the braking of the vehicle.
• Since the PWM mode result in a huge amount of simulation time, Averaged mode is slected for this simulation.
•  Load current charecteristics are considered to be smoothed here.
• Also, the regenerative braking is enabled for the simulation. this means, when the vehicle starts decelerating, corresponding  amount of charge will be fed back to the battery.
• Acordingly, the BRK input is connected to a Controlled voltage sorce. This will generate emf corresponding to the internsity of brakes applied andfed the poer back to the battery.

The output voltage Amplitude of the H-bridge circuit is given the same value as the rated DC supply voltage of the DC motor. The input Threshold parameter are left with their defult vaules.

Simulink provides an inbuild controlled PWM Voltage This block is used for providing proper pulse  inputs to the H- bridge circuit.

• The PWM and REF connection are for the corresponding ports on the H- bridge circuit.
• The 2 reference  input correspond to the  throttle input given by the Driver. the block generator corresponding pulse  with as per the acceleration  and brakes applied by the driver himself.
• Hear the PWM  Frequency is 1000Hz . also the  simulation mode is as Average as that  in the H Bridge circuit.

The input scalling  parameters given are:-

0 for 0% duty cycle and 5v for 100% duty cycle accordingly the output voltage amplitude  become 5v.

The H -bridge circuit along with PWN input, together from the motor controller circuit.

(4) Longitudinal Driver:

Longitudinal Driver is an inbult block provided by the powertrain block set

• it is a parametric longituditional speed tracking controller for generating normalized Accelaration and braking commands based on reference and feedback velocities.
• The VelRef port is the reference velocity port where the input drive cycle data is fed.
• The VelFdbk port corresponds to the feedback velocity. the actual velocity output given by the vehicle body is connected here. by comparing the actual (feed back) velocity with the reference velocity, the Driver block generates Acceleration and breking signal order to minimise the error between the two concerned velocities.
• Grade corresponds to the grade angle. for this simulation, no inclination is considered and hence, a constant block with value 0 is connected.
• Info gives  the output for the bus signal for diffrent block calculation like difference in reference vehicle speed,etc.
• AccelCmd & DecelCmd correspond to the acceleration and deceleration commands generated respectively and are connected to the  corresponding port of the  Contrlled PWM Voltage block.
• Here, the seleced control type is  PL Acoordingly, the block implements proportional - integral (PI) control with tracking windup and feed forward gains.

(5) Battery Pack

• To model the Battery pack, a simple Battery block is used. This is because, if the generic battery block is used instead, the simulation will run for amuch longer time.
• Here, the selected option for Battery Charge Capacity is Finite. Accordingly, the block models the battery as a series internal resistance plus a charge-dependent voltage source. if the choisen option Infinite, the voltage source would have been constant.
• Also, the self-discharging of the battery  and the battery dynamic are disabled.
• The battery normal voltage given as 400v.
• The Ampere-hour rating is assumed to be 50.
• The rest all parameters are left with their default vallues.

• To ensure the battery supplies current as per the requirements of the motor controller and not the rated current, a Current sensor & controlled current source pair is connected.

(6) Reference velocity (DrivevCycle):

• The Drive cycle source  block is used to provide the reference speed for the simulation.
• it  generates a standard or user- specified longitudinal drive cycle.

• Here the selected drive cycle is the standard FTP75

• The plot of the drive cycle is shown below

(7) Battery state of Charge:

• A small subsystem is created to calculate the state of charge  of the battery.
• This subsystem takes the battery as the input.

• Accordingly, the current is integrrated W.r.t time to get the charge in coulumbs. now this coulumb value is modified into Ampere hours.
• this value is now subtracted from the charging capacity of the battery 50Ah.
• Finaly, the remaining charge is now converted into percetage value of the charging capacity of the battery.

Model

(The simulink model is attached  with the report for the reference)

Simulation:

• The system is ran for simulation for 2474 which is the total time for which the input drive cycle is defined.
• A solver configration is added to ensure prper solving of the mathermatical equations by the model.

• scopes are connected to analyze diffrent outputs such as the soc of the battery, the reference velocity & the actual velocity of the vehicle and the  distance covered by the vehicle during the total run.
• the 2 velocities are first converted from m/s to Kmph values. for this , simple Gain blocks are used.
• the distance is calculated by simply time - intergration of the vehicle velocity.

CONCLUSION

We learn quit a lot of iteresting thinkgs like-

1. how to model an EV and carry out a real time simulation
2. how a motor controller works and what role it plays in the control of the electric motor
3. how to calculate the soc of the battery
4. different powertrain blocks provided by simulink which can be used to simulate a vehicle model.

NOTE:- 

• Unable to run  the model because  mathwork not supporting ask lisence vertion,
• This model i was created when i have lisence, allready expired
• without run unable to take result output,
• I allready done mentoring section they say submit as is it