Week-11 Challenge: Braking

1. For a defined driving cycle, calculate the energy required for braking.
2. Why electric motor can’t develop braking torque at high speed similar to starting? How electric and mechanical brakes are coordinated?
3. 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

ANS1- using formula for ke=0.6*mass*(vinitial^2-vfinal^2)

total power=energy*time

DRIVE CYCLE
TIME IN SECONDS	SPEED IN KMPH
0	0
1	1
2	3
3	6
4	9
5	12
6	15
7	18
8	25
9	35
10	50
11	55
12	60
13	50
14	40
15	40
16	41
17	42
18	43
19	44
20	45
21	46
22	47
23	48
24	49
25	50
26	40
27	35
28	30
29	35
30	30
31	36
32	37
33	43
34	45
35	47
36	55
37	60
38	63
39	67
40	68
41	68
42	70
43	73
44	75
45	77
46	78
47	79
48	80
49	78
50	75
51	73
52	67
53	62
54	56
55	50
56	45
57	40
58	30
59	20
60	25
61	30
62	40
63	45
64	48
65	50
66	51
67	52
68	53
69	54
70	55
71	56
72	57
73	58
74	59
75	60
76	53
77	50
78	47
79	43
80	40
81	35
82	37
83	39
84	41
85	45
86	48
87	50
88	55
89	60
90	63
91	67
92	71
93	75
94	80
95	65
96	55
97	45
98	35
99	20
100	10
101	0

2. when electric brakes are aplly on motor ,motor works as generator.transfer elecrical energy from brake to energy storage device.electrical brake can not br large enough because it deteriorate system stability. acceleration torque from motor is more than the decceleration torque.

*at high speed motor is in constant power region which limits the apllied braking torque.

* due to high tempr gegenerative torque can not be made wholly so it aplly with combination of mechanical torque.two stategy is used

*series control strategy

* parallel control strategy.

series- a fiction mechanical brake with regenerative brake is applied. both distribute brake power between them.

this gives increase in fuel efficiency by upto 30%.\

parallel-both brakes are applied simultaneously.regenerative brake can not be control.renerative braking depends on motor capacity,vehicle velocity and battery soc.

application of braking in nissan leaf.

at high speed both brakes are apllied

*at lower speed more regenerstive brake is apllied.

3.

motor speed 0-1000 rpm

motor torque=0-700 n-m

clear all
close all
clc
%speed array
omega=linspace(0,300,100);
%torque_array
T=linspace(0,2000,100);
%mesh_grid
[X,Y]=meshgrid(T,omega);
%losses
cu=0.17;%copper_coeff;
fe=0.006;%iron coeef.;
win=0.000015;%windage_coeff.;
cu_loss=cu*(Y.^2);%copper_loss
fe_loss=fe*(X.^2);%iron_losses
win_loss=win*(X.^3);%windage lossed
cond_loss=18;%conduction losses
P_out=(X.*Y);%output power
P_in=P_out+cu_loss+fe_loss+win_loss+cond_loss;%input_power
n=((P_out)./(P_in));%efficiency
w=linspace(0.75,0.95,10);
contour(X,Y,n,w);
xlabel('angular speed(rad/s)')
ylabel('torque(n-m)');
title('speed,torue and efficiency characteristics of motor')