Final Project: Design of an Electric Vehicle

SOLUTION:

. Electric vehicle (EV) is defined as a vehicle that uses an electric motor or a traction motor for propulsion unlikely to an internal combustion (IC) engine used by conventional vehicles.

. Electric vehicles use electric power instead of fuels as conventional vehicles would and because of this difference, electric vehicles do not produce any exhaust gases or pollution(Zero emission).

. 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.

. MATLAB model of electric car which uses lithium ion battery and induction motor.

The Components are:

The main components of modelling an EV are

. Vehicle body

. Motor & motor controllers

. Power converters

. Batteries

. Drive cycle

BLOCK DIAGRAM:

DETAILED MODEL STUDY:

Sub -systems :

.Vehicle body

. Represents a two-axle vehicle body in motion.

Input Ports:

. W - Wind Velocity in m/s

. beta - Grade angle in radians

Output Ports:

. V - Velocity in m/s

. NR - Normal force on Rear Axle (N)

. NF - Normal Force on Front Axle (N)

Vehicle Body Parameters:

Tires

. used to model a tire with longitudinal behavior given by equation based on four fitting coefficients.

. The vehicle is assumed to be a front axle driven (4 wheels - 2 on each axle).

. The wheels are modelled using simple Tire (Magic formula) simulink blocks

Input Port:

. N - Normal force acting on tire, positive when force is acting downwards/towards the contact surface,

Output Port:

. S - Slip value relative to tire and surface of contact.

Conserving Ports:

• H - represents wheel hub which transmits thrust generated by the wheel to the body of the vehicle.
• A - represents axle on which the tires are mounted.

Gear

• A simple gear block is used to connect the motor to the rear axle of the vehicle.
• It represents the gearbox which connects the input shaft to the base gear and ouput from the foller gear.

Conserving Ports:

• B - port associated with input shaft (motor shaft)
• F - port associated with ouput shaft (axle / differential)

Simple Gear Parameters:

• Gear ratio and output direction is modified.
• Meshing loss is kept constant and gear is having a constant efficiency throughout the simulation.
• Viscous losses and faluts are kept at default conditions.

MOTOR & POWER CONVERTER:

The motor & its control block is as shown below:

H-Bridge

The H-Bridge helps in controlling the power that is input according to the requirement. The output provided are converted voltage as per the controlled parameters.

. DC Motor

This is the DC Motor which would give the rotational power to the wheels and become the sole power generation source.

The DC Motors terminals are connected as mentioned below,

+ = Electrical signal to the motor Positive Terminal

- = Electrical signal to the motor Negative Terminal

R = Casing of the Motor connected with the Mechanical Rotational Reference Block

C = Rotor Case connected to the Mechanical Rotational reference.

Battery Source

The battery is connected as the power source to the model so that the power could be generated and the same power is transmitted accordingly to all the operating sources.

The terminals connected are to,

+ = The positive terminal of the operating sources

- = The negative terminal of the operating sources.

Components of battery block is depicted below:

The paramters considered of the battery are -

The battery Nominal Voltage is rated as per 300 Volts,

The internal resistance is as per 0.5 Ohms and others set as default.

. Driver Model

The Driver Model has the Input and Output Ports which are connected to the following,

Velocity Reference - Drive Cycle

Velocity Feedback - Distance Calculation

Grade - Constant 0

Info - Not Connected

Acceleration Command - Controlled PWM Source

Deceleration Command - Brake in H-Bridge to maintain the speed according to the Drive Cycle.

. Drive Cycle :

starting with the Drive Cycle,let consider a WOT Drive Cycle for the operation of the Cycle in which the test duration would be 60 seconds.

Outputs :

The model with the above details is simulated and the results are as follows :-

1) Ref. Speed v/s Actual vehicle speed :

Distance Covered :

• It may be noted that, since, the reference velocity of the drive cycle never becomes negative (i.e. there is no backward motion of the vehicle), the distance is increasing throughout.
• The total distance covered by the vehicle is about 3.8 km.
  
  

Battery State of Charge :

CONCLUSION : The model was succesfully ran for simulation under the standard FTP75 drive cycle. The results have been properly analyzed.