Week-11 Challenge: Braking
Q.1.
Braking: The brake system in cars is easily the most important part of any vehicle simply because your well-being depends entirely on it. Brakes are so important that it’s actually not possible to live with a vehicle with a brake system that’s not in good shape. Any car’s braking system works on the simple laws of motion from Newton, especially the second law, which says – “A body continues to be in its state of rest or of motion unless an external force acts on the same.” Today, in this post, we tell you everything there’s to know about the braking system of a vehicle. In case there is a car that doesn’t have a good braking system, the stopping distance would increase by a huge margin, and this would lead to accidents. Hence, a car’s brake system should always be in perfect shape in order to be able to stop a vehicle at the least possible distance without putting the occupants in any sort of discomfort. Brake systems have come a long way since the time the first car went on sale. Below, we have explained the brake systems in cars in reasonable detail.
Basically, a car’s brake system is designed in a way that it stops/reduces the speed of the vehicle through a set of components that convert the vehicle’s kinetic energy into heat through the generation of friction. For the uninitiated, friction is the energy generated during resistance between two surfaces. Therefore, in a nutshell, the brake system of a car works by a generation of friction by bringing in contact a stationary surface with a kinetic surface.
The brake system in cars is easily the most important part of any vehicle simply because your well-being depends entirely on it. Brakes are so important that it’s actually not possible to live with a vehicle with a brake system that’s not in good shape. Any car’s braking system works on the simple laws of motion from Newton, especially the second law, which says – “A body continues to be in its state of rest or of motion unless an external force acts on the same.” Today, in this post, we tell you everything there’s to know about the braking system of a vehicle.
In case there is a car that doesn’t have a good braking system, the stopping distance would increase by a huge margin, and this would lead to accidents. Hence, a car’s brake system should always be in perfect shape in order to be able to stop a vehicle in the least possible distance without putting the occupants in any sort of discomfort. Brake systems have come a long way since the time the first car went on sale. Below, we have explained the brake systems in cars in reasonable detail.
As soon as you press the brake pedal of a car, the brake pads or the brake shoes start rubbing against the disc or drum, respectively. Thus, the kinetic energy is converted into heat energy through friction generated between the two surfaces. Once the vehicle comes to a full stop, it stays stationary through the static friction. Over here, the friction generated between the tires and the road, and even the brakes and the wheels, keep the vehicle from moving forward.
Regenerative braking:
When you step on your petrol or diesel car’s brake pedal, the hydraulic fluid pushes brake pads against brake discs on each wheel (or drums on older and cheaper models). The resulting friction works to slow the car down, generating heat and wearing away at the material on the pads and discs in the process. Regenerative braking is a way of taking the wasted energy from the process of slowing down a car and using it to recharge the car’s batteries. On a normal car, braking simply wastes energy - but with regenerative braking, some of the energy is able to be reused.
Regenerative braking systems are common on many modern cars. On petrol and diesel models, it’s used to charge the battery that runs various ancillary systems in the car, meaning less work for the engine and less fuel burned. In these cars, the system is virtually imperceptible to the driver but in hybrid and pure electric cars, regenerative braking takes a more active and obvious role. In these models, brake regeneration can help charge the larger batteries that directly drive the car. The electric motor in your hybrid or the electric car runs in two directions - one to drive the wheels and move the car, and the other to recharge the battery. When you lift your foot off the accelerator pedal and onto the brake, the motor swaps directions and starts to put energy back into the battery. When this process kicks in, you can feel the car start to slow down. It’s a different sensation in each car that has this function because manufacturers can program how much regenerative braking occurs when you lift off the pedal. All cars still have normal brakes, so if you push the pedal hard enough then the hydraulic system will kick in to get you stopped quickly (depending on your speed). Again, different cars will have different amounts of force on the pedal needed to get the brakes to kick in.
Braking efficiency = 0.5*mass*V^2
= 0.5*800*V^2
Excel link :- https://1drv.ms/x/s!AsOQ8CgSAoRM5lRNcy2DaPTtMBLZ
Hence the total energy braking is = 316.197 KJ.
Q.2.
An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor's shaft.
Most electric motors are designed to run at 50% to 100% of rated load. Maximum efficiency is usually near 75% of rated load. Thus, a 10-horsepower (hp) motor has an acceptable load range of 5 to 10 hp; peak efficiency is at 7.5 hp. A motor's efficiency tends to decrease dramatically below about 50% load.Electric motors work by converting electrical energy to mechanical energy in order to create motion. Force is generated within the motor through the interaction between a magnetic field and winding alternating (AC) or direct (DC) current.
Eectric motor can't develop braking torque at high speed similar to starting, because Braking torque is applied in the opposite direction of the rotation. We can use a mechanical brake to produce a braking torque.
Q.3.
% A MATLAB PROGRAMM FOR PLOTTING CONTROL
clc
% SPEED ARRAY
N = linspace(0, 1000)
% TORQUE ARRAY T=linspace(0,300)
kc = 0.18; % COPPER LOSSES
% LOSS COEFFICIENTS 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
wiindage_loss = (X.^3) *kw
cons 20
o_p = x. *Y
input power = (copper_loss)+(iron_loss)
Eff (o_p)./ (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')
label('TORQUE N/m')
(Output is given in the screenshot attached below)