Final Project: Design of an Electric Vehicle

Introduction :-A new study to vehicle/automobile engineering say that by coming 2025, there will be major transformation in the auromobile sector. many automaker are working to change the vehicle technology, the major area is to decerase the pollution and use electrification in the upcoming vehicle. the researchers and automakers are continuously working to reduce CO2 emission.

new technology like high capacity lithum typs battery will be a major energy source for the propulsion of electric vehicle.

At present with the new technology, some manufacturing has launched its products which are tesla, chevy bolt EVand nissan leaf which are fully electric battery based car.

the power and performance of electric vehicle is dependent upon the two machine i.e, a brushless DC motor (BLDC)or an induction motor. the DC (direct current) is replaced by DC brushless motors and induction motors. the lead acid battery is replaced by lithum ion battery for EV application. because the feautuer of both the component induction or brushless DC motors depends upon their demands and uses.

The important component of electric vehicle areas.

1. auxilliary battery:- In an electric vehicle drive vehicle, the auxilliary battery provides electricity to power vehicle accessories.

2. Traction battery pack:- Traction battery pack is also known as electric vehicle battery (EVB) which is store the electricity. some exples of traction battery energy storage system are given as.

3. Lithium-ion.

4. Nickel-metal Hybride

5. ultra-capacitors

7. DC/DC converter- Dc/DC converter is an electronic device which is used to converter higher-voltage DC power from the traction battery pack to the lower-voltage DC power. the converter power is used to run the vehicle accessories. it is also used to recharge the auxiliary battery.

8. Electric traction motor:- Another important componenet is electric traction motor and this device is used to provid motive power to the wheels.

9. onboard charger:- The incoming AC electricity supplied via the charger and converter it to DC power for charging for traction battery it monitors battery characteristic such as voltage, current, controlling the speed of electric traction motor and the torque it produce.

10. power electronic controller:-this unit manage the flow of electricel energy delivered by the traction battery, controlling the speed of electric traction battery pack.

11. charge port:- the charge port allow the vehicle to connect to en external power supply in order to cahnge the traction battery pack.

12. thermal system(cooling);- this system maintain the proper operation temperature range of vehicle motor power electronic and other componenet.

MATLAB modelling of electric car.

vehicle technical specification

. vehicle weight(kg): 1147

. number of wheel per axle:2

. total length:4.127mor 4,127mm

. total height:1.487m or 1,487mm

. total width:1.746m or 1,746mm

By using MATLB SIMULINK system block for electric vehicle design and the whole design is as :

Important simulink block used in electric vehicle design are

. drive cycle source :1

. constsnt:3

. longitudinal drive:1

. controlled voltage source:2

. controlled PWm voltage:1

. solver confriguration :1

. Electrical reference:2

. H-bridge:1

. DC motor:1

. Mechanical rotational reference:1

. current sensor:1

. Battery:1

. controllef current source:1

. PS-simulink converter:4

. vehicle body:1

. Tire:4

. simple gear:1

. inertia :1

. goto:2

. ps constant:2

. gain:2

. zero order hold:1

. Rate transition:1

. Discrete time integrate:1

. sum:1

. integrator:1

. Divide: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 different number of wheels on each axle.

The block conisist 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 includs an externally-define mass and externally-define inertia. the mass, inertia and centre of gravity of the vehicle body can very over the course of simulation in response to system changes.

In given block

1. NR:-it is physical singal output which is connect to the rear wheel axle. for this model, it is connect with a noraml force of rear tire.

2. NF:- it is physical singal output which is connect to front wheel axles and for this particular model it is connected with the normal force acting on the tire.

3. Beta:-beta is basically a road incline angle. here we can define a constant value for road angle inclination.

4. H:- this port is horizontal motion of the vehicle body. this connected will be connected with all four hub of the wheel for finding the thrust genertaed by the tire.

5. V:- this port is the vehicle longitudinal velocity.

6. W:- it is a headwind speed. basically we will define a particular wind speed by adding constant block.

. step for vehicle body just double click on the vehicle body and enter as per requirement.

. here i have done some change in vehicle confriguration, basically i changed the vehicle mass, langth and frontal area.

detail input of vehicle body:

Main setting

1. mass=1147kg

2. number of wheels per axles=2

. the horizontal distance from CG to front axles 1.854m

2. the horizontal distance from CG to the rear axles =2.2730m

4. CG height above ground=0.5m

5. externally-define additional mass=OFF

. gravitational acc=9.81m/s^2

. negative normal force warning=OFF

drag setting

2. frontal area=2.21m^2

3. drag coefficient=0.20

pitch setting

1. pitch dynamics=OFF

variable settings

1. Beginning value of velocity=0 m/s

other connected detail

. wind velocity=2.22222m/s

. road incline=0

The velocity here, we have created a subsystem i-e LOG mph, this block basically consist of PS simulink converter gain, zero order hold.

gain block : 1.61 and it multiple input value with constant input.

zero-order hold : 0.01, the zero-order hold block holds it inputs for the sample period you spacify

TIRE MODELLING

The tire (magic formula) block models a tire with longitudianl behaviour given by the maginic formula. an empiricalbased on four fitting coefficient. the block can be model tire dynamic under constant or variable pavement condition.

The tire blocke the tire ass a right wheel tire combination in contact with the road nad subject to slip. when torque is applied to the wheel axle the tire pushes on the ground and transfer to the resultating reaction as a force back on the wheel. this action pushes the wheel forward if you includes the optional tire compliance, the tire also flexible deforms under load.the

figure shows the forces acting on the tire.

where,

Fx = longitudinal force exerted on the tire at the contact point

Fz = verticle load on the tire

ohm = wheel angular velocity

Vx == wheel hub longitudinal velocity

the particlar block

. N = normal force acting on the tire and connected with NR of the vehicle boby.

. S = slip between the tire and road and connected with goto block

. H = hub and it used to fined the thrust createed by the tire and its connected with H inputs of vehicle body also including all four hub of the wheel.

. A = axel and rear axle are connected with the final drive system and the front axles is connected with the left and right wheel.

Tire block, we can change the parameter

Main setting

. parameterize- load - dependent magic formula coefficient, it is basically specifying the parameters that define the dependent dependent.

Tire nominal verticle load- this is basically a normal force on the tire (fz0), so, this particular model, the normal force i have taken is 4000N.

Magnic formula - C,D,E,BCD,H and V are defaults, basically it is a load-dependent magic formula coefficient.

Geometry setting

Rolling radius - 0.32, it is unloaded tire-wheels radius, rw.

Dynamic settings

inertia- specify inertie and final velocity which depend upon stiff, dampened spring and deforms under load.

Tire inertia- 0.5kg*m^2 and it is rotational inertia lw of the wheel tire assembly.

initial velocity - 0 rpm and it is an initial angular velocity,ohm(0), of thr tire.

Rolling resistance setting

. Rolling resistance-on, basically it includes the rolling resistance.

. Resistance model - by using constant coefficient we are neglect rolling resistance.

Advance setting

. velocity threshold - 0.1 m/s as i keep this value as default and value should be positive because it is wheel hub velocity Vth below which the slip calculation is modifified to avoid singular evolution at zero velocity.

INERTIA

T = j*(dw/dt)

t = inertia torque

j = inertia

ohm = angular velocity

t = time

The inertia value is 0.01kg*m^2 nad this block is connected with rear axle and final drive ration to the fined the inertia because axle and gear are a mechanical rotating device.

Simple Gear

Gear is a final drive ratio which is gear box that constrains the connected drivline axes of the base gear and follow gear.

B: the output B, base gear is connect with the input of DC motor R, it is rotational mechanical conerving port.

F: the output of F. follows gear is connected with the rear axles. it is also a rotational mechanical conservation port.

simple gear box we can also be do some changes according to our need

meshing losses

1.friction model - drop down

2.efficiency - 0.86

3.follower power threshold - 0.001w

confriguration battery and SOC

BATTERY

Battery system to run the vehicle system and vehicles too. so.for tht added battery from simlulink libary.

i used a simple battery model. for a particular battery, there is some changes inputs.

if we are selected battrey charge capacity as finite from the drop-down menu then thsi basically describes the seris resister and a change dependent voltage source and for the this, a particilar equation is which is dependent upon the voltage as a function of charge.

V = Vo(SOC/1-beta(SOC))

SOC- sate of chage is the ration 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, Vnom parameter.

beat - is a consatant that is calculate so that the battery voltage is V1 when the charge is Ah1.

the connection of battery is as follow , the negative (-) terminal is connected with the ground and controlled current source physical port the positive direction that indicates the flow.

the positive (+) terminal is also connected to the controlled to the current source of electrical conserving ports.

CONTROLLED CURRENT SOURCE

Thae controled current source block reperesnet an idea current source that is powerfull engugh to maintain the specific current through it regardless of the voltage across the source.

this particular, the two-port is connected with battery and one electrical conversing ports is connetced with PS- simulink converter to the rate transition block and scope block.

ELECTRICEL REFERENCE

The electricel reference block represents an electrical ground. for this block is connect with battery negative(-) terminal.

PS-SIMULINK CONVERTER

The ps-simliunk converter block converter a physical singnal intoa= a simulink output singal. use this block to connect output of a physical network diagram to simulink scopes or other simulink blocks.

the SOC (state of charge) we have to create a subsystem which will consist of rate transition, gain, time integrate, constant and sum blocks.

RATE TRANSITION

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

Input singal- input singal is the input singal converter to teh sample rate you specify.

GAIN BLOCK

the gain block multiplies the input by a constant value (gain). the input and the gain can each be a scalar, vector,or matrix.

here gain value is the multiplication elemet and the input is 1/(50*3600). where 50is battery amere and 3600 is second.

DISCREATE-TIME INTEGRATOR

. define initial condition on the block dialogue box

. define an input gain(k) value

. output the block state

. define upper and lower limits on the integral

. reset the state with an additional reset input

SUM BLOCK

the sum block perform addition or subtraction on its inputs.

the negative terminal will be connected with discreste-time integrator and positive terminal with constant.

the DCmotor block repreesent the electrical and torque characteristics of a DC motor using the following equivalent circuit circuit model.

. No load speed;- 11000rpm, this is the speed of the motor when not driving a load.

. rated speed( at load):- 10500rpm, this is the speed of the motor at rated mechanical power level.

H-BRIDGE

simulation mode and load assumotion settings.

. power supply :- the power supply is default mode i.e internal.

. simulation mode :- here i selected average mode and this mode has two load current characteristic options.

unsmoothed or discontinuous

. Regenertative braking :- always enables , this option can be used when the controller always sets the REV flag to ensure regenerative braking.

. load current characteristics :- smoothed , it is a default option and it assumes that the current is practically is practically continuous due to load inductance.

DRIVE CYCLE SOURCE

this particluar electric vehicle here i used FTP75 drive cycle. the plotted drive cycle is give

DISTANCE CALCULATION

the main block is an integrate, divide, time block and for the result we have to use disply block that will display the distance.

detail about connection

Integrator :- the output port of the vehicle body is connected with the intergal block.

Divide :- The output of the integrate block is connected with divide wher it will be divided by time to get the final output.

Time :- the output of time block is connected with the divide block. here time is taken as 3600s.

results

1. longitudinal driver/decel

positive duty cycle = 11.779%

negative duty cycle = 88.310%

2. SOC %

the battery start discharging after 17.272sec and its discharge till 2471.533sec. transition level.

. high = 7.7410e-01

. low = -5.690e-01

. Amolitude = 1.340e+00

. Fall time = 1.608ks

. slew rate = -666.517ms

3. current

the starts of current is 18.917 s and we can see that the current is constant for 602.051s starting from 1385.868s to 1987.918s

Transitions level

. high = 1.837e+02

. low = 1.121+02

. Amplitude = 7.162e+01 ( difference in amplitude between the high-state level and the low-state level)

. Rise time = 1.905s

. positive slew rate = 50.231/s

. fall time = 6.173s

. Negative slew rate = -21.216/s

cycle level

. period = 72.570s

. positive duty cycle = 40.173%

. negative duty cycle = 60.171%

4.speed

here the yellow graph indicates the vehicle speed whereas blue graph indicates the reference speed.

the difference timr between the reverse speed vs vehicle speed, this is basically starting of vehicle speed.

the reference speed starts at 20.097s whereas vehicle speed starts at 22.142s and the total difference between these two are 2.045s

transition level

. high; 1.373+01

. low: 1.283e-01

. Amplitude: 1.360e+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 5.318 m/s or 19.1448 kmph depending upon the FTP75 drive cycle and the total for simulation wea 2474 sec.

the battery is having 300v which is a nominal voltage and the battery ampere per hours rating is 50 by which we calculated the SOC ( state of charge) of battery.

the DC motor is used to run the rear axles of the vehicle and when the car is with no load condition them the motor operation RPM is 11000 and when the car is running at some load or we can say that some rated speed them the motor RPM is taken at 10500. the voltage supply to DC motor is 300v.