Challenge

Week-11 Challenge: Braking

HEV WEEK 11 CHALLENGE

QUESTION 1:

BRAKING ENERGY CALCULATION FOR A DRIVING CYCLE:

DRVING CYCLE:

An excel file used to create a drive cycle with time and velocity values
Which import to matlab workspace to plot the driving cycle
The driving cycle graph is shown below
Braking happen at 3 instances in this driving cycle ,the further calculation is shown below

EXCEL SHEET CALCULATION:

The braking power and energy calculation done in a excel sheet
Mass of the vehicle assumed to 1000kg
The initial speed, final speed and decceleration time obtained from the driving cycle
Energy in joules can be calculated

E= m*(Vf^2-Vi^2)/2

Pbrake = E/t*1000

Where,Pbrake - braking power in kw
t-decceleration time in s
Total braking power for the driving cycle can be obtained by adding all braking power
Total energy required for braking in kwh can be calculated as

Ebrake = P*t/3600

CONCLUSION:

The total energy required for braking for the defined driving cycle is -0.0414 kwh

QUESTION 2:

REGENERATIVE BRAKING IN ELECTRIC VEHICLE:

Regenerating braking is technique when the braking action feed the power back to the battery
In regenerative braking,the motor runs above the synchronous speed
And the motor runs as generator and feed the power back to battery or simply charge the battery
Normally the torque is constant for low speed and gradually decrease as the speed increases (constant power region)
When the vehicle reach the high speed and we apply the brake ,the negative torque correponding to that speed will act which is lower than the acceleration torque
So for the high speed ,torque is less,which limits the braking toque
The peak acceleration torque is always greater than the peak breaking torque or they are not equal
Thats the reason electric motor cant produce braking torque similar to acceleration

ELECTRIC AND MECHANICAL BRAKES IN A VEHICLE:

The regenerative and mechanical brakes can be arranged in series or parallel configuration depends on the application
There will be a limit how much power should be generated back to batttery
This power converters limitations in the regenerative action,will bring the action of mechanical brakes in to the system
When we have only regenerative braking ,and we apply brake at high speed ,it may damage the system
So the electrical and mechanical brakes can work imultaneously to achieve a good braking system

Electric Drives Intelligent Brake (EDIB):

EDBI is a breaking technique ,in which regenerative and mechanical braking applied with repect to speed
For high speed ,more mechanical power applied than of regenerative braking
Because of the limitation of power converter on regeneration of power
As the speed increase ,the regenerative brake strength increases
And mechanical brakes applied on low magnitude
This coordination of electric and mechanical brakes according to speed of the vehicle more reliable

CONCLUSION:

The peak accelartion torque is higher than the peak braking torque
This why electric motor cant produce same torque at high speed during braking as of acceleration
The coordination of electric and mechanical brakess discusssed

QUESTION 3:

PLOTING CONTOUR OF MOTOR SPEED,TORQUE AND EFFICIENCY USING MATLAB

MATLAB CODE:

RESULT:

CONCLUSION:

The contour plot for motor speed,torque and efficiency is plotted using MATLAB

Ship work like this
in your own course.