Vehicle dynamics is the study of how a vehicle reacts to driver inputs based on classical mechanics. It examines attributes like body roll, bump steer, weight transfer, and ride quality. There are different types of engine power like indicated power (at the cylinder) and brake power (at the crankshaft). Automotive resistances that reduce usable power include rolling resistance, road gradient resistance, and air resistance. Tests are conducted to find properties like the center of gravity location, moments of inertia, and brake force distribution which enhance vehicle stability, steering control, and overall design.

1. VEHICLE DYNAMICS
• PRESENTED BY
• NIKHIL PAWAR
• (2130331612031)
• F.Y. MECHANICAL ENGINEERING

3. 2. INTRODUCTION
It is the study of how the vehicle will react to driver inputs on a given road. Vehicle dynamics is a
part of engineering primarily based on classical mechanics.
Vehicles
• Wheels
• Motion
• Self-powered
Dynamics
• Greek “DYNAMIS”
• power
• Vehicle Ride and Handling
• Ride is associated with comfort and grip
• Handling is associated with path following
• Driving task has two components: Command and control

4. 2. ASPECTS OF VEHICLE DYNAMICS
Some attributes or aspects of vehicle dynamics are purely dynamic. These include:
1.Body flex
2.Body roll
3.Bump Steer
4.Bundorf analysis
5.Directional stability
6.Understeer, oversteer
7.Pitch
8.Roll
9.Yaw
10. Noise, vibration, and harshness
11. Ride quality
12. Speed wobble
13. Weight transfer and load transfer

5. 3.POWER AND TORQUE CHARACTERISTICS OF AUTOMOBILE

6. 4. ENGINE POWER OUTPUT
Following types of powers are being quoted with reference to engines.
1. INDICATED POWER
The power developed inside the cylinder by combustion of gases is called indicate horsepower.Anindicating device an oscilloscope is used
to determine IP.
IP = pLANK/1000×kW
2. BRAKE POWER
The power available at the crankshaft (for onward transmission to drive the vehicle) is called thebrake power. Rating of automotive
engines is done m terms of BP. Brake power can be measured by dynamometer.
BHP = 2πNT/4500
where N is in rpm and T in kgf-m.
If N is in rps and T in Nm, then 4500 will be replaced by 1000 and power will be kW. Then it will be calculated by,
BP = 2πNT/1000
3. FRICTION POWER
A larger proportion of brake horsepower goes waste in overcoming various resistances in a movingvehicle. Rest of the Power is utilized to
propel the vehicle. This power which is utilized to propel thevehicle is known as drawbar horsepower (DHP).
FP = IP-BP

7. 4. TAXABLE HORSEPOWER
It is also used to categorize engines on a uniform basis. To illustrate, we consider a race event of auto
vehicles in which all types of vehicles ranging from mopeds, scooters, motorcycles, cars etc. are thep
participants. Question arises whether all these vehicles should run together, or they be grouped indifferent
categories.
THD = D^2N/2.5
5. DRAWBAR HORSEPOWER
A larger proportion of brake horsepower goes waste in overcoming various resistances in a movingvehicle.
Rest of the Power is utilized to propel the vehicle. This power which is utilized to propel the vehicle is
known as drawbar horsepower (DHP).
DHP = BHP - RESISTANCES

8. 5. AUTOMOTIVE RESISTANCES AND PROPULSIVE POWER
The brake horsepower available at the crankshaft of an automotive engine is not fully utilized to Speed up the vehicle much of it goes waste to overcome various
resistances which are given as under.
1. ROAD RESISTANCE
(A) ROLLING RESISTANCE
It mainly occurs due to the deformation of road and tyre, and dissipation of energy through impact.The rolling resistance depends upon,
• Mass of the vehicle
• Material of the road surface such as; asphalt, macadam, gravel, clay, wood or sand.
• Nature (quality) of the road surface such as poor, good, dry or wet.
• Material of the tyres
• Inflation of the tyres
The rolling resistance R, can be expressed by,
R r = C r mg
Where Cri is rolling resistance constant and m is mass of the vehicle. The value of Cr, depends upon the condition of tyre and road surfaces in contact..
(B) FRICTIONAL RESISTANCES
Another kind of road resistance is frictional resistance that includes resistance due to transmissionlosses also. Such losses are owing to
• Lower gear efficiencies in first, second, and top gears.
• Churning of oil in gearbox and the rear axle system.
• Adhesion of tyre which is about 65% of the total losses in chassis. The frictional resistance R can be approximated by
R f = 132.5 + 50.5 m

9. 2. ROAD GRADIENT RESISTANCE
Slope (Gradient) of the road has considerable effect on the
resistance to motion of the vehicle. The gradient resistance
depends upon
• mass of the vehicle
• slope of the Road on which vehicle is moving
The road gradient resistance Rg is expressed by
. R g = mg sin θ
3. AIR (or WIND) RESISTANCE
The air resistance faced by an automobile depends upon
• Speed of the vehicle
• Size and shape of the vehicle
• Speed of moving air
• Direction of wind with respect to direction of the vehicles motion
Ra is expressed by :
R a = C a AV^2
Gradeability of vehicle
Effect of Speed on Aur Resistance

10. 7. MEASUREMENT OF THE TEST VEHICLES
7.1 BENCH TESTS
(A) LOCATION OF CENTRE OF GRAVITY
The location of centre of gravity of the test vehicle is determined in a longitudinal, lateral and verticaldirection. Below, the longitudinal
direction is called the x coordinate, the lateral direction y coordinate andthe vertical direction z coordinate. The location of centre of gravity in the x and y directions is
determinedby measuring the four wheel loads by means of wheel-load scales, onto which the vehicle is placed.
Alongside the overall weight of the vehicle determined in this way, the position of the centre of gravity in an x and y direction can be calculated with the known wheel base and
track width variables by productionof torque equilibria.
The height of the centre of gravity is determined by weight displacement
when lifting an axle. In thisprocess, the brakes are released and the
transmission is in neutral, through which the wheels can be freelyturned.
The efficiency lines of the axle loads pass through the wheel centre lines.
To detect the axle load of the axle which has not been lifted, two wheel-
load scales are used.
As a function of the inclination of the vehicle, the axle loads on the front
and rear axle change. The height h of the centre of gravity above the level
passing through the front and rear wheel centre linecan be calculated via
the torque equilibrium around the rear wheel centre line from the difference of
the axle loads and the angle of inclination of the vehicle in question
. H cog = (∆G.I)/[tan(a)
Measurement of the vehicle’s centre of gravity height H cog

11. (B) MOMENT OF INERTIA
The moment of inertia, otherwise known as the angular mass or rotational inertia, of a rigidbody is a quantity that determines
the torque needed for a desired angular acceleration about arotational axis; similar to how mass determines the force needed
for a desired acceleration. It dependson the body's mass distribution and the axis chosen, with larger moments requiring more
torque tochange the body's rotation rate.
Now that the location of centre of gravity is known, the moments of inertia (MOI) around the longitudinal, lateral and vertical
axes can be measured. This is done by the vehicle oscillating aroundthe corresponding axes at the centre of gravity of the vehicle
against springs of a known stiffness. Bymeasurement of the oscillation time T, the moments of inertia can be calculated with
known spring stiffness.
To determine the moments of inertia around the lateral axis of the vehicle, the vehicle is placed on a cutting line transverse to
the direction of travel. The cutting line is aligned in such a way that theCentre of gravity of the vehicle in a horizontal position of
the vehicle is vertically above the cuttingline. In the longitudinal direction of the vehicle, springs on which the vehicle supports
itself via the auxiliary frame are clamped in at identical distances
Euler's theorem is used to calculate the moment of inertia of the vehicle/frame unit around the cuttingb line axis from the
frequency of the oscillations of this system:
,Frame from the overall moment of inertia around the cutting line Θy, total, the
moment of inertia of the vehicle alone around the cutting line axis.
Θ y,Veh = Θ y,total – Θ y,Frame
The second item having an influence on the moment of inertia around the lateral axis is the so-called
“Steiner ratio” of the vehicle.
. Θy,CoG = Θy,Veh -mVeh ∆h2

12. 7.2 BRAKE FORCE DISTRIBUTION
These measurements are done on the “ABS test bench” of the ika. The ABS test bench has four sets
of rollers driven independently of one another onto which the vehicle is placed. Thanks to a movable
frame for the rollers for the rear axle, the test bench can be adjusted to various wheel bases. All four
wheels are driven evenly via the rollers with a speed corresponding to a traction of 6.5 kph. The
reaction torque and thus the effective brake power up to a
maximum of 5 kN are measured by a force
transmitter interposed between the drive
unit support and the frame. A detection
roller measures the actual wheel speed in
order to switch the test bench off automa-
tically in the event of excessive slip
between the rollers and the wheel. A principal
diagram of the ABS test bench is shown in Figure. ABS Test Bench

13. 7.3 DRIVING TESTS
Driving Test Instruments

14. 8. CONCLUSION
1. Enhance vehicle steerability and stability
Steerability is enhanced in normal driving condition.
Braking is involved only when the vehicle tends to instability
2. Precise steering control requires understanding of interaction between tyre and road.
Treated as disturbance to be cancelled out.
3. Vehicle state estimation uses interaction between tire and road as source of information.
Seen by observer as force that govern vehicle’s motion.
4. Vehicle dynamics are important to enable a good overall design of such a complex product
as a vehicle intended for mass production at affordable cost for the customers.

15. 9. REFERENCES
1. K.M. Gupta, “Automobile Engineering” by Umesh Publications, Third Edition, Page no. 78-84,
87-90,.
2. R.S. Khurmi, J.K. Gupta, “ Theory Of Machines” by S. Chand Publications, Third Edition Page
no. 253-255.
3. K.M. Moeed, “Automobile Engineering” by Katson Publications, Revised Edition 2016, Page
no. 63-64.
4. J. J. Uicker; G. R. Pennock; J. E. Shigley (2003). Theory of Machines and Mechanisms (3rd ed.).
New York: Oxford University Press. ISBN 9780195155983.
5. Marion, JB; Thornton, ST (1995). Classical dynamics of particles & systems (4th ed.).
Thomson. ISBN 0-03-097302-3.

16. THANK YOU