Week-11 Challenge: Braking

1)

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

drive cycle :

https://docs.google.com/spreadsheets/d/1aU936FnYFJhnoU3y9GgtPhwZTdkkiE4ht8LaSWbDFDI/edit?usp=sharing

From the drive cycle, there are 4 different situations of deceleration of which the energy has to be calculated.

First Braking: 24 - 15km/hr in 4 sec

Second Braking: 35 - 30km/hr in 1 sec

Third Braking: 45 - 23 km/hr in 5 sec

Fourth braking: 63 - 5 km/hr in 7 sec

Using Excel Calculator:

Total Braking energy required = 0.134 kWh

2)

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

The term braking comes from the term brake. We know that brake is equipment to reduce the speed of any moving or rotating equipment, like vehicles, locomotives. The process of applying brakes can be termed braking. We can classify the term braking into two parts:

• Mechanical Braking 
• Electrical Braking

Mechanical braking :

Mechanical brakes all act by generating frictional forces as two surfaces rub against each other. The stopping power or capacity of a brake depends largely on the surface area of frictional surfaces as well as on the actuation force applied. The friction and wear encountered by the working surfaces are severe. Thus, the durability of a brake or service life between maintenance depends heavily on the type of material used to line the shoe or pad. Mechanical brakes are assemblies consisting of mechanical elements for the slowing or stopping of shafts in equipment drives. They use levers or linkages to transmit force from one point to another. Braking slows or stops the movement of the coupled shafts. There are several types of mechanical brakes. Band brakes, the simplest brake configuration, have a metal band lined with heat and wear-resistant friction material. Drum brakes, which are commonly used on automobile rear wheels, work when shoes press against a spinning surface called a drum. Disc brakes are constructed of brake pads, a caliper, and a rotor. During operation, the brake pads are squeezed against the rotor. Cone brakes are made with a cup and a cone, which is lined with heat and wear-resistant material. During actuation, the cone is pressed against the mating cup surface.

Electric braking :

Electric brakes are devices that use an electrical current or magnetic actuating force to slow or stop the motion of a rotating component. They are used in industrial and vehicular braking applications that require fast response times and precise tension control. The magnet in the backing plate has 2 conductor wires which tap directly into the wiring. When electricity is on, it magnetizes the brake magnet. The magnet is attracted to the drum face. When it contacts this area, the friction causes it to rotate, which moves the actuating arm, and pushes the shoes out against the drum. Those shoes have a special brake pad material on them that resists the heat caused by that friction. When the shoes press against the inside of the drum, they prevent the hub, and consequently the wheel that's touching the ground from spinning.

clear all
close all
clc

%Speed Array
omega = linspace(0, 300, 100);

%Torque Array
T = linspace(0, 2000, 100);

%Meshgrid
[X,Y] = meshgrid(T, omega);

%Loss Coefficients:

%Copper coefficient
c = 0.17;
%Iron coefficient
I = 0.006;
%Windage coefficient
w = 0.000015;

%Losses :

%Copper Losses
closs = c*(Y.^2);
% Iron Losses
Iloss = I*(X.^2);
% Windage Losses
wloss = w*(X.^3);
% Conduction Losses% Output Power
closs = 18;

% Output Power :
Power_out = (X.*Y);      

% Input Power :
Power_in = Power_out +  (closs) + (Iloss) + (wloss) + (closs);

% Efficiency :
eta = ((Power_out)./(Power_in));

% Efficiency values for contour :
W = linspace(0.75, 0.95, 10);

% Contour Plot :

contour(X,Y,eta,W)
xlabel('Angular Speed, rad/s')
ylabel('Torque, Nm')
title('Speed, Torque, Efficiency characteristics of Motor')

matlab save file is in the link below

matlab save file