Week-11 Challenge: Braking

Q1.For a defined driving cycle, calculate the energy required for braking.

In a vehicle, the amount of power required for deceleration and acceleration are the same. the power required for braking can be calculated

Given:

E = 1/2.M.V^2

M = Mass of vehicle

V = velocity of a vehicle

Vi = Initial velocity

Vf = Final velocity

mass=500kg

Time	Velocity
1	0
2	15
3	28
4	50
5	68
6	80
7	75
8	35
9	22
10	15

At Time= 2

E = 0.5*500*(15-0)^2

E = 56250 J

E = 56.25 KJ

At T= 4

E = 0.5*500*(50-28)^2

E = 121000 J

E = 121KJ

At T= 6

E = 0.5*500*(80-68)^2

E = 36000J

E = 36KJ

At T= 8

E = 0.5*500*(35-75)^2

E = 400000J

E = 400KJ

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Q2.Why electric motor can’t develop braking torque at high speed similar to starting? How electric and mechanical brakes are coordinated?

At low speed the torque is constant and at hight speed, the maximum torque is decreased, In a motor, the torque-speed relation is governed by a constant torque up to speed when maximum power is achieved. when a motor runs at high speed the torque is less. The motor at high speed which generates less torque now the braking torque will not be as similar as starting torque Therefore the maximum torque of acceleration and deceleration is not equal it varies with vehicle speed.

There are two types of control strategy:

1. Series

2. Parallel

In series, the mechanical brakes will be applied first then regenerative braking follows.

In parallel, both mechanical and regenerative braking will be applied for decelerating the vehicle faster.

Mechanical braking:

The most common method of braking in motor vehicles is mechanical or friction braking. In this method, some or all of the vehicle wheels are fitted with brake pads that apply a friction force that inhibits the motion of the wheels. Frictional braking results in a conversion of the kinetic energy gained from fuel consumption to thermal energy. This thermal energy then dissipates into the atmosphere in the form of waste heat.

Regenerative braking:

Regenerative braking involves the removal of the kinetic energy of a moving object by converting it into another form of useful energy, such as electric, pneumatic, or stored kinetic energy. The use of regenerative braking can increase the overall efficiency of a motor vehicle by conserving some of its kinetic energy which can then be used to bring the vehicle back up to speed.

Electric driven Intelligent Brake(EDIB):

EVs and hybrid vehicles use regenerative braking, which utilizes the motor to convert the kinetic energy during deceleration into electrical energy. With energy regeneration, an EV is able to run on less electricity and a hybrid vehicle on less fuel.

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.

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Q3.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

Program:

% A program for plotting efficiency contours for electric motors.
close all
clear all
clc

% set up arrays for range.
x=linspace(1,1500);
y=linspace(1,120);

% Allocate motor loss constants.
% For copper losses iron losses windage losses and  constant motor losses
kc=1.5; 
ki=0.1; 
kw=0.00001; 
ConL=20; 

% Now make mesh and Torque(y) x speed(x) = power
[X,Y]=meshgrid(x,y);
Outputpower=(X.*Y); 

B=(Y.^2)*kc; 
C=X*ki; 
D=(X.^3)*kw; 
Inputpower = Outputpower + B + C + D + ConL;
Z = Outputpower./Inputpower;

% We now set the efficiencies for which a contour will be plotted.
V=[0.5,0.6,0.7,0.75,0.8,0.85,0.88];

% Poltting
box off
grid off
axis([-inf inf -inf inf])
ML = contour(X,Y,Z,V);
clabel(ML);
xlabel('Speed/rad.s^-^1'); 
ylabel('Torque/N.m');
hold on
% Now plot a contour of the power output. We draw contours at
% 3 and 5 kW.
V=[3000,5000];
contour(X,Y,Outputpower,V);

Results:

Output Graph: