Final Ppt-Auto Lab
Transcript of Final Ppt-Auto Lab
Project IntroductionProblem Statement
• Design a car with multiple platforms integrated into a hybrid chassis
Concept
• The concept is a four wheeler, from which a two wheel vehicle can be detached and used independently
• While the car is powered by a front mounted, front wheel drive IC engine, the bike is designed to have a rear wheel electric drive.
Team Structure➔ Concept ➔ Design➔ Structure➔ Suspension➔ Engines➔ Transmission➔ Tyres➔ Safety
StructureBackbone Chassis
• Type a chassis that is similar to ladder type. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone that connects the front and rear suspension attachment areas.
Advantages
• Single point connection which enables easy coupling and decoupling of the two modules
• Flexible design to accommodate design contraptions for transformations
SuspensionFour-wheeler module
• Idea 1- dependent leaf springso Lower torsional forceso Poor road comfort and road holding capability
• Idea 2- double wish-bone suspension with Mac-Pherson strutso Higher torsional forceso Better comfort, road holding capability
Idea 1 Idea 2
SuspensionTwo-wheeler module
• Based on independent Mac-Pherson struts
• Redesigned to fit in the steering mechanism of the bike
• Uni-fork design to act as fixed support for car and steering mechanism for bike
Rear Module Uni-fork design
Transmission
Fuel tank IC Engine Clutch Gear box
Differential
Front wheelsGenerator Bike battery
Clutch/Controller
Engine stalling rpm 1000
Engine max. rpm 4000
Wheel diameter 0.4826
Reduction at Differential (assumed) 3
First gear ratio 3.5
Second gear ratio 2.5
Third gear ratio 1.6
Fourth gear ratio 1.1
Fifth gear ratio 0.75
Reverse 3.5
first gear second gear third gear fourth gear fifth gear
min max min max min max min max min max
Vehicle wheel speed (rpm) 95.24 380.95 133.33 533.33 208.33 833.33 303.03 1,212.12 444.44
1,777.78
Speed in mps 2.41 9.63 3.37 13.48 5.26 21.06 7.66 30.63 11.23 44.92
Speed in kmph 8.66 34.65 12.13 48.52 18.95 75.81 27.57 110.26 40.43 161.72
Transmission in bike
Battery Motor WheelsDischarging
Charging
Powering
Braking
TyresMotor bike tyres are predominantly bias where-as car tyres are radial
Possible configurations:
• All radialo Improper cornering for the two-wheeler module; leaning the tyre is harder when it is flato Tyre strength while cornering is lesser compared to biaso The fuel efficiency will reduces if the motor-bike has radial tyreso Symmetry; Better handling characteristics
• Front radial, rear biaso Non-uniform brake forces might lead to oversteero Compromise on ride comfort
Final configuration: Front radial and rear bias
Tentative dimensions:
Radial: 140/65 15’’ (From Toyota Prius)
Bias: 140/50 17’’ (From Ducati) Outer diameter (Both) ~ 22’’
Hybrid Convertible- End review
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CAD Model
Engine - Car
Tractive forces:1. Aerodynamic Forces(Fae) = ½ * Cd* d*A*V2
2. Acceleration or Inertial forces(Facc) = M*a 3. Rolling resistance(Fr) = frr * N4. To overcome gradient = W*sint
● Equation of motion:
● Maximum Tractive force that can be obtained from the road for a real wheel driven car:
Maximum Force that can be achieved at wheel = 4920 N Maximum Torque that can be achieved at wheel = 1380
Nm
Mass (kg) 1300
gravity (m/s2) 9.8
mass distribution (front:rear) 60:40
rear wheel RR 0.02
front wheel RR 0.012
Drag coefficient (Cd) 0.4
width (m) 1.5
Proj. height (m) 1.2
Center of gravity height (m) 0.5
Tyre Diameter (inch) 22
Mu (friction b/w tyre and road) 0.75
Velocity (m/s) Acceleration (m/s^2) Gradient (deg) Torque at wheel (Nm) rpm of the wheel
0 3 5 1450 0
12 1 12 1360 410
45 0.75 3 760 1540
70 0 0 650 2400
Powertrain Design● Higher Gear (Nt4) assumed as 1.1 (close to direct drive)
● Differential Gear ratio (Nd) = ne* r / (Vmax*Nt4)
● Selecting Lowest Gear (Nt1) :
Gradient that the car can overcome =
Lowest Gear ratio =
Intermediate Gears: Usually gears are placed so that they are in geometric progression
Engine and Transmission specificationsAfter several iterations of1. Looking for available Torque vs rpm and Power vs rpm characteristics of IC engines2. Trying to fit gears so that torque and rpm needed at wheels matches with that of obtained torque
vs rpm curve
Differential gear ratio 2.13
First Gear 3.4
Second Gear 2.3
Third Gear 1.6
Fourth Gear 1.1
Maximum Torque 240 Nm at 3500 rpm
Maximum Power 110 kW at 5500 rpm
Engine capacity 2.9 litres
Engine type V6
Electric Two Wheeler Mass (kg) 150
Gravity(m.s-2) 9.8Mass distribution [front] 0.5Mass distribution [rear] 0.5
Rear wheel RR 0.02Front wheel RR 0.012
Drag coefficient [Cd] 0.7Width (m) 0.8
Proj. height (m) 1Length (m) 1.5
Wheel Base (m) 1.4Proj. area (m2) 0.8
Density of air (Kg.m-3) 1.22Height of CG (m) 0.5
Friction b/w tyre n road [μ] 0.75Tyre Dia (inch) 22
● The two wheeler at the rear when detached from the car frame runs on an individual electric motor powered by a battery which derives its charge from the IC engine.
● Maximum torque that can be generated at the wheel turns out to be 122 N.m based upon the parameters mentioned. Calculation approach is same as that used in the four-wheeler.
● Torque vs. rpm characteristics at wheel were found out through the desired vehicle performance parameters shown in the next slide.
Velocity acceleration grade rpm Torque Power
0 2 10 0 119 0
10 1 5 341.778689531629 98 3.5075161059413
20 0.5 1 683.557379063258 72 5.15390121689334
25 0 0 854.446723829073 66 5.90551181102362
Choosing the Appropriate Motor
Batterylithium ion battery pack.20 cell packcapacity: 70Ahweight : ~48 kgs
Final drive ratio (chain drive): 2.05
Brake force calculations
Braking Performance
Assumed brake force distribution 78:22For this condition front wheel locks up and a/g = 0.775
Vehicle parametersParameter Symbol Units Value
Mass M kg 1300
Wheel Base l m 2.2
Height of CG above ground h m 0.5
Fixed brake ratio frontrear
KbfKbr
_ 0.780.22
Braking force on front axleBraking force on rear axleTotal Braking force
FbfFbrFb
N7582.082138.549720.62
Tyre diameter d m 0.5588 (22 in)
Braking Torque on front axle Braking Torque on rear axle
TfTr
Nm 2118.43597.51
Stopping distance
Stopping distance =
= 194 massumed V1 = 200km/h
Cae = 0.02Additional stopping distance Sa (brake system response time) = tdV1
assuming td = 0.3 s
Total stopping distance = 210 m
Disc brakes
F = Actuation forceT = Friction torque
re = effective radius
Force location =
ri=inner diameter of the padro=outer diameter of the padѲ1, Ѳ2=caliper angles
Material Friction coefficient(f)
Maximum Pressure(Pmax, Mpa)
Max Instantaneous temp(°C)
Max continuous temp(°C)
Rigid MoldedAsbestos
0.31-0.49 5.2 500-700 230-350
Brake pad material taken: Rigid Molded Asbestos
We chose rotor of diameter 260 mm and with piston area 410mm^2
Parameter Symbol Units Value
Inner diameter of the padOuter diameter of the pad
ri
ro m0.098425(3.875in)0.1397(5.5 in)
Hydraulic cylinder diameter rc m 0.0381(1.5 in)
Normal pressure(max) pa Mpa 0.87
Actuation force Fa kN 6.59
equivalent radius re m 0.1022096
Reqd hydraulic pressure ph Mpa 5.7
Energy analysis of disc brakesBraking energy
Braking energy = 2302.4kNmAverage braking power = 131.4kW
Temperature analysis
Mass of disc brakeTemperature Rise for Brake Assembly
Overall Coefficient of Heat Transfer
Maximum Temperature of Brake Assembly
Backbone Structure
“I” frame with hollow circular shafts.
Static loading, acceleration and braking for front and rear shafts
Shaft-2
Acceleration
Braking
Braking
Structure stresses
Max stress at static loading Max stress at acceleration Max stress at braking
9.92 Mpa 7.16 MPa 1.3 MPa
1.3 MPa 2.1 MPa 1.48 MPa
6.62 MPa 1.27 MPa 6.86 MPa
Final geometry and material parameters
L1 1.5
L2 3.6
L3 1.5
D1 0.15
d1 0.13
D2 0.15
d2 0.13
D3 0.15
d3 0.13
E1 210000000000
E2 210000000000
E3 210000000000
Cornering Stiffness SelectionParameters
C-alpha-f(N/rad) 59000
C-apha-r(N/rad) 53000
Wf(N) 7644
Wr(N) 5096
Turning Radius(m)
30
Lateral Vehicle Dynamics
Lateral Acceleration Gain
Velocity
Curvature GainYaw Rate Gain
Velocity
Velocity
Understeer Coefficient = 0.0334Critical Speed = 192 kmph
Suspension Characteristicssprung mass acceleration
sprung mass acceleration suspension deflection
Suspension stiffnesses Ks=11000 to 30000Damping Coefficient bs= 800 to 1200
Bounce and Pitch Frequencies
Kf = 1250 to 12000 and Kr= 11000 to 22000For these stiffness values, bounce frequency was between 1.2 - 1.8 Hz and the pitch frequency 1.8 - 2.3 Hz.
Thank You!