Week-11 Challenge: Braking
1.For a defined driving cycle, calculate the energy required for braking.
Answer:-
Definition:-
driving cycle is a series of data points representing the speed of a vehicle versus
time.
Driving cycles are produced by different countries and organizations to assess the
performance of vehicles in various ways, for instance, fuel consumption, electric vehicle
autonomy and polluting emissions
calculate the energy required for braking.
we have been able to use the energy which is been disappeared at the point of
breaking. The kinetic energy which helps the vehicle to run also gets wasted while the
braking is done. Though it depends on various parameters on how effective the braking
would be it can be depended upon.
a. Number of Brake Pistons
b. Duration and Degree of Brake Pedal been Pressed
c. Road Condition
d. Temperature
e. Brake Pad and Disc Condition
f. Mass of the Vehicle
Still with a basic operation where the vehicle is in motion and the brakes are applied the
same efficiency could be calculated by the given equations.
where,
BE=braking energy
m=mass of the vehicle
v = velocity
In this manner, the same calculation is carried out for calculating the brake efficiency
required at the peak point. It is a drive cycle with speed variations the braking power
required would vary but still, the highest braking power required is mentioned below
please refer to the attached sheet for complete calculation of deacceleration energy
require in the UDDS cycle.
To reduce speed from 80 to 40 kmph in 20 sec =292 KJ
To reduce speed from 80 to 0 kmph in 0 sec =560 K
2.Why electric motor can’t develop braking torque at a high speed similar to
starting? How electric and mechanical brakes are coordinated?
Answer:-
Why electric motor can t develop braking torque at a high speed similar to
starting?
When the motor is at rest and it has to operate from a standstill position to reach the
moderate speed the higher torque is required to bring the motor into operation.
Whereas when the vehicle is already at high speed the capping or the limit is reached
by the motor operation and thus any further higher torque could not be obtained while
braking. The braking operation happens in the motion which is been distributed as per
proportion in the BRAKE ENERGY and the REGENERATIVE BRAKING.
• How electric and mechanical brakes are coordinated?
In Mechanical braking which we usually see and experience in all vehicles, the brake
pedal in the vehicle cabin helps us to engage or disengage the brakes. Currently,
braking technology has done wonders by inventing life-saving braking technologies
such as ABS, EBD, BA and many others. All these technologies play a vital role in
stopping the vehicle and coming back to rest at a high speed. In all these vehicles when
the driver applies the brakes the brake pads
come closer to the disc connected with the driving disc. The brake pads usually help
inefficient braking.
There are two generic methods by which the vehicle could be braked in the ELECTRIC
BRAKES.
1.Series - The Regenerative Braking of the Mechanical Braking are applied one
after another.
2.Parallel - The Regenerative Braking or the Mechanical Braking both are applied
Parallely.
When the brake pedal is pressed the hydraulic fluid reaches the brake piston and
created the braking pressure on the wheels and the same kinetic energy is been used
by the Regenerative Braking for generating more power using the Bi-directional motor
which operates as a
generator while braking An example of the proposition of Regenerative Braking and the
Mechanical Braking
NISSAN LEAF EDIB (ELECTRONIC-DRIVEN INTELLIGENT BRAKING)
EDIB (Electric Driven Intelligent Brake) controls the regenerative brake and friction
brake to support both of these requirements. Further, it also controls the reactive force
from the pedal in order to unify the feeling when stepping down on the pedal and the
sense of deceleration.
3.Make a MATLAB program that plots the contour of given motor speed, torque
and efficiency values. Attach the code as a .m file attach a screenshot of all the
plots.
Answer:-
a MATLAB program that plots the contour of given motor speed, torque and efficiency
values
% A MATLAB PROGRAMM FOR PLOTTING CONTOUR PLOT OF MOTOR SPEED
clear all
close all
clc
% SPEED ARRAY
w=linspace(0,1000)
% TORQUE ARRAY
T= linspace(0,300)
% LOSS COEFFICIENTS
kc = 0.15; % COPPER LOSSES
ki =0.005; % IRON LOSSES
kw =0.000012; % WINDAGE LOSSES.
% MESHGRID
[X,Y]= meshgrid(w,T)
copper_loss =(Y.^2)*kc
iron_loss= X*ki
wiindage_loss= (X.^3)*kw
cons = 20
output =X, Y
input_power = (copper_loss)+(iron_loss)+(wiindage_loss)+(output)+(cons)
Eff= (output)./(input_power)
n = linspace(0.7,0.95,10)
box off
grid off
contour (X,Y,Eff,n)
title(SPEED TORQUE CHARACTERISTICS)
xlabel('SPEED RAD/s')
ylabel('TORQUE N/m')
Explanation:
In this program, we are plotting speed Vs torque characteristics with the efficiency
values. For this, first, we are defining the speed and torque values of the motor.
Then as we need to draw a contour, we convert this ID array to a 2D array using the
"MESH GRID" command.
Then we are defining the Cu constants for losses, like Cu loss constants, iron loss
constant and windage loss constant.
Pi=Pout+KcT^2+Ki*w+Kw*^3+Const
Using this formula, we calculate the efficiency and then plot the contour.
workspace:-
Result:
