Week-11 Challenge: Braking

Question 1

Energy = `1/2mv^2`

for braking condition, we take 3 different Cases at different interval of time

1st braking/deceleration = 24km/h - 15km/h 6seconds

2nd braking/deceleration = 46km/h - 23km/h 6seconds

3rd braking/deceleration = 62km/h - 0km/h 7seconds

https://drive.google.com/file/d/1pDWOCKvmcH4AzNFTYjFUwduxJfL6PTdo/view?usp=sharing

Question 2

Regenerative braking allows EVs to use the electric motor as a generator when the brakes are applied. Regenerative braking is an effective approach to increase the driving range of an EVs.

Regenerative braking produces a torque which cannot be increased to the required braking torque as it will lead to the instability of the vehicle. At high-speed motor is on constant power region where torque produced is less which is a limited amount of torque used for regenerative braking.

Hence the peak value of motoring torque and braking torque is not equal.

There are 2 types of braking:-

1. Electric brakes
2. Mechanical Brakes

The electric braking system should not be used under the condition, such as high SOC or high temperature of the battery whereas in the case of mechanical braking the system works to cover the total braking required.

After combining the mechanical braking and regenerative braking there are 2 possible conditions:-

1. Series Control Strategy
2. Parallel Control Strategy

Series Control Strategy

A combination of mechanical braking with a regenerative braking system which transfers the energy to the battery which is control by an integrator, which distributes the braking force in the mechanical and regenerative braking system. Series Control Strategy can increase fuel efficiency by 15-30% and it has more consistent braking due.

Parallel Control Strategy

A combination of the mechanical braking system and regenerative braking system which operates without an integrated control. The regenerative braking is added to the mechanical braking force which cannot be controlled.

Regenerative braking is determined by the motor capacity, vehicle velocity and battery SOC, Regenerative braking is calculated by a brake control unit by comparing motor torque and demanded torque available.

Electric Driven Intelligent Brake (EDIB)

EDIB application can be seen is NISSAN LEAF. In EDIBit allows and controls the regenerative brakes and regular friction brake or the hydraulic brakes.

At high speed, both regenerative braking and hydraulic brakes are almost equal. At low speed, the regenerative braking increases because of motor torque characteristics. at low speed, the more braking torque is generated.

Question 3

clear all
clc
s = linspace(1, 1000);
T = linspace(1, 300);
kc = 0.1;       %copper loss
ki = 0.001;     %iron loss
kw = 0.0001;    %windage loss
Cm = 20;        %motor loss
[X,Y] = meshgrid(s,T);
Pout = X.*Y;
a = (Y.^2).*kc;
b = ki.*X;
c = (X.^3).*kw;
Pin = Pout + a + b + c + Cm;
eff = Pout./Pin;
EFF = [0.65, 0.69, 0.70, 0.75, 0.80, 0.85, 0.88, 0.91, 0.96];
contourf(X,Y,eff,EFF);
xlabel('speed(rad/s)');
ylabel('torque(N.m)');