Week-11 Challenge: Braking
1.For a defined driving cycle, calculate the energy required for braking.
ANSWER
As we know that the energy can never be created or niether destroyed with the today's development
we have been able to utilize the energy which is been wasted at the time of braking. The kinetic energy which assist
the vehicle to move also gets dissipated while the braking is done. Though it depends on multiple parameters on
how efficient the braking would be it can be depended upon.
Number of Brake Pistons
Duration and Degree of Brake Pedal been Pressed
Road Condition
Temprature
Brake Pad and Disc Condition
Mass of the Vehicle
Still with a basic operation where the vehicle in motion and the brakes are applied the same efficiency could be
calculated by the given equations.
BE = ,
BE = braking energy
m = mass of the vehicle
v = velocity
In this manner the same calculation is been carried out for calculating the brake efficiency that would be required at
the peak point. It bieng a drive cycle with speed variations the braking power required would vary but still the highest
braking power required is mentioned below-
BREAKING ENERGY REQUIRED IS 160 KJ for the speed of 57kmph
2.Why electric motor can’t develop braking torque at high speed similar to starting? How electric and mechanical brakes are coordinated?
ANSWER:
• Why electric motor can't develop braking torque at high speed similar to starting?
When the motor is at rest and it has to operate from standstill position to the reach the moderate speed the higher
orque is required to bring the motor in 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.
speed torque characterstics shown in below:
Here it is clearly shown in the first graph that till the motor reaches the critical speed it has constant torque and once it reaches the critical speed, the curve is having a down slope which is a constant power region. And this graph denotes the accelerating operation of the motor. For the deceleration or braking operation of the motor, this graph is mirrored down which will be having the speed (+ve) and torque (-ve).
• 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 the braking technology have done wonders by inventing life saving
raking technologies such as ABS, EBD, BA and mny others. All these technologies play vital role in stopping the
vehicle and coming back to rest from a high speed. In all these vehicles when the driver applies the brakes the brakep
eds come closer to the disc connected with the driving disc. The brake pads usually help in efficient braking.
here are two generic methods by which the vehicle could be braked in the ELECTRIC BRAKES.
series - The Regenerative Braking or the Mechanical Braking noth are applied one after another.
parallel - The Regenerative Braking or the Mechnical Braking both are applied Parallely.
hen the brake pedal is pressed the hydraulic fluid reaches the brake piston and created the braking pressure on
he wheels and the same kinetic energy is been used by the Regenerative Braking for generating more power using
he Bi-directional motor which operates as a generator while braking.
NISSAN LEAD - EDIB (ELECTRONIC DRIVEN INTELLEGENT 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 which plots contour of given motor speed, torque and efficiency values. Attach the code as a .m file attach a screenshot of all the plots.
ANSWER:
As we Know contour is a graphical technique of representing 3-dimensional surface. The same is mentioned below
for the given details-
% A MATLAB PROGRAMM FOR PLOTTING CONTOUR PLOT OF MOTOR SPEED, TORQUE
clear all
close all
clc
% SPEED ARRAY
w = linspace(0,1000)
% TORQUE ARRAY
T = linspace(0,300)
% LOSS COEFFICIENTS
kc = 0.18; % COPPER LOSSES
ki = 0.006; % IRON LOSSES
kw = 0.000015; % WINDAGE LOSSES
% MESHGRID
[X,Y] = meshgrid(w,T)
copper_loss = (Y.^2)*kc
iron_loss = X*ki
windage_loss = (X.^3)*kw
cons = 20
o_p = X.*Y
input_power = (copper_loss)+(iron_loss)+(windage_loss)+(o_p)+cons
Eff = (o_p)./(input_power)
n = linspace(0.710.95,10)
box off
grid off
contour(X,Y,Eff,n)
title('SPEED TORQUE CHARACTERISTICS')
xlabel('SPEED RAD/s')
ylabel('TORQUE N/m')
Program Description:
• Here in this program first two inputs were given. They are Speed & Torque using linspace command.
• Then the motor constant values are assigned namely Copper loss, Iron loss, Windage loss and Constant motor.
• Then meshgrid is used to evaluate functions of two variables and three-dimensional mesh/surface plots.
• Output Power is calculated by multiplying speed and torque.
• Then all the loss were calculated and the input powers were also calculated.
• Then comes the efficiency were calculated. And Contour graph is plotted between Speed, Torque and Efficiency.
• Title were given and labels were given
output:
https://drive.google.com/file/d/1-0khHN5u_Jxb9cJ4A2jGVIfbozJ_WjN6/view?usp=sharing
CONCLUSIONS:
1. For a defined driving cycle, the energy required for braking is calculated.
2. Why electric motor can't develop braking torque at high speed similar to starting and how electric and mechanical brakes are coordinated were dicussed.
3. A MATLAB program which plots contour of given motor speed, torque and efficiency values is coded.