Week-11 Challenge: Braking

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

The energy required for braking is calculated for total load of 800kg- 63.088(kJ)

Link for excel sheet- https://docs.google.com/spreadsheets/d/1SptUNw9PU8W2LjAaLURpyF11XSGGU8Mj/edit?usp=sharing&ouid=109586349649833990045&rtpof=true&sd=true

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

In case of Dc motor starting there will be high torque as the vehicle picks up the speed Dc motor moves into constant power region and in case of high speed it's really hard get to high torque as in case of low speed.Peak acceleration and Peak deacceleration is not same in case of electric vehicle.

Braking control

1)Usually cars should have both rear and front brake active so that car dosen't loose it's motion and be on track

2)Braking is achieved by both mechanical and regenerative braking system.

3)At high speed regenerative braking is insufficent because it cannot produce high torque and battery have certain limit of charging, So these limits in this case cannot enforce the vehicle to just run on regenerative braking system.

4)This is the reason that it cannot produce high torque and at high speed it could be very risky, so to have sufficent braking Braking should be done in such a way that both mechanical and electric braking are used.

5)But In case of low speed the torque required is less and hence regenerative braking system can be used and there will be good amount of charging.

6) poweer converter limitation also add up in the case of reverse flow.

Brake control startergies-

Series braking-

In case this case regenerative braking and mechanical braking is applied one after the other, they both are not apllied at the same time.

Parallel braking-

In his case electric and mechanical braking are both applied at the same time.

Hence we can conclude that electric and mechanical braking are both co-ordinated each other for HEV And EV.

Depending upon the comfort any of both can be choosen.

So looking on the comfort and all Nissan has designed a braking system which is both comfortable and good at brakes called as intelligent automatic Braking system.cleary from the figure we can understand at high speed mechanical braking is higher and at low speed regenerative braking is more.

1. 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.

2. % Program to Calculate Efficiency of Motor and Plot its Contour Graph
   
   clear all
   close all
   clc
   
   % Speed and Torque array
   speed = linspace(1,1000); 
   torque = linspace(1,250);  
   
   % Constant values of Motor Losses
   KC = 0.2;            
   KI = 0.008;
   KW = 0.00001;
   Constant_loss = 20;
   
   [S,T] = meshgrid(speed,torque)
   Output_power = (S.*T);  % Power = speed * Torque
   
   Cu_loss = (T.^2)*KC;   % Copper Loss
   Fe_loss = S*KI;        % Iron Loss
   Wind_loss = (S.^3)*KW;    % Windage Loss
   
   In_power = Output_power + Cu_loss + Fe_loss + Wind_loss + Constant_loss;     
   
   Z = Output_power./In_power;
   
   % Plot the Contour Graph for Efficiency
   V = [0.70, 0.80, 0.85, 0.90 0.91, 0.92, 0.925, 0.93];
   box off
   grid off
   contour(S,T,Z,V);
   xlabel('Speed [rad/s]');
   ylabel('Torque [N.m]');
   title('Efficiency Contour of Electric Motor');
   hold on
   
   
   V = [4000,8000];
   contour(S,T,Output_power,V)
   shading interp

Array of speed and torque are given,Later consant losses considering copper loss, iron loss and windage loss are given.

Total power input = sum of ouput power and sum of all the losses.

efficency is calulated using formulae output/input power.

Then countour is plotted considering speed ,torque, efficency and the efficency points.