Week-11 Challenge: Braking

AIM: 

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

Definition:-

Electrical Braking is usually employed in applications to stop a unit driven by motors in an exact position or to have the speed of the driven unit suitably controlled during its deceleration. Electrical braking is used in applications where frequent, quick, accurate or emergency stops are required.

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.

1. Number of Brake Pistons
2. Duration and Degree of Brake Pedal been Pressed
3. Road Condition
4. Temperature
5. Brake Pad and Disc Condition
6. 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

Link:- https://drive.google.com/file/d/1GCIFObS9OWaKkV_r61DLeM1FjSbXKPh-/view?usp=sharing

 Braking Energy Require 

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 KJ

Question2

Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction motor uses the vehicle's momentum to recover energy that would otherwise be lost to the brake discs as heat. This contrasts with conventional braking systems, where the excess kinetic energy is converted to unwanted and wasted heat due to friction in the brakes, or with rhehostatic brakes, where the energy is recovered by using electric motors as generators but is immediately dissipated as heat in resisters. In addition to improving the overall efficiency of the vehicle, regeneration can significantly extend the life of the braking system as the mechanical parts will not wear out very quickly.

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

  QUESTION 3 

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:-