> []# Futuretron EV Course_CHAPTER8

# CHAPTER 9: Vehicle Dynamics

Vehicle Dynamics is a study of vehicle activity when under conditions of operation they are exposed to various types of loads and forces. It is a principal concept in automotive design and production. For forecasting vehicle failure in the long term, a Knowlegde of Vehicle Dynamics is necessary.

## 9.1 Acceleration
It is velocity transition rate with respect to time. Acceleration is a quantity of the vector which has both direction and magnitude. This is expressed mathematically as the second time-related derivative of position, or as the first time-related derivative of velocity.

Formula is expressed as:


Where,
a is the acceleration in m.s-2
vf is the final velocity in m.s-1
vi is the initial velocity in m.s-1
t is the time interval in s
Δv is the small change in the velocity in m.s-1

### 8.1.1 Types of Acceleration

#### 1. Uniform and Non Uniform Acceleration

Uniform acceleration is a method of motion in which an object's velocity varies by the same amount over each equivalent time frame.

Non-uniform acceleration means an object's acceleration is not continuous, but increases or decreases over a period of time

Ref:https://tse1.mm.bing.net/th?id=OIP.lvNRiNjnY2q--o2SGIclqQHaCr&pid=Api&P=0&w=487&h=176

There is a state of constant speed with acceleration of the body. It happens when a body moves in circular manner when speed remains constant but changes its direction which results change in velocity and the body is accelerated.

#### 2. Average Acceleration and Instantaneous Acceleration

The average acceleration is calculated by the cumulative change in velocity in the given period divided by the overall time taken for change. For a given interval of time, it is denoted as ā.
Mathematically,

v2 and v1 denote instantaneous velocities at time interval of t2 and t1.
ā denote average acceleration.

#### Examples
**Q1.** What will be the acceleration of an object which moves with uniform velocity?
Ans:
Given,
The velocity is uniform, therefore the initial and final velocities are equal and is given as V.
∴From definition, acceleration is given as:
a=vf−vit a=0t ∴ a = 0

**Q2.** A truck is moving with a constant velocity, v = 5 m.s-1. The driver stops for diesel and the truck accelerates forward. After 20 seconds, the driver stops accelerating to maintain a constant velocity, v = 25 m.s-1. What is the truck’s acceleration?
Ans:
Given,
Initial velocity, vi = 5 m.s-1
Final velocity, vf = 25 m.s-1
Time interval, t = 20 s
∴From definition, acceleration is given as:
a=vf−vit a=25−520 ∴a=1 m.s-2

**Q3.** Find the final velocity of the ball that is dropped from the second floor if the ball takes 18 seconds before hitting the ground. The acceleration due to gravity is g = 9.80 m.s-2.
Ans:
Given,
Initial velocity, vi = 0 m.s-1
Final velocity, vf = ?
Acceleration due to gravity = a = g = 9.80 m.s-2
Time interval, t = 18 s
∴From definition, acceleration is given as:
a=vf−vit Rearranging the formula,
vf=vi + at
vf= 0+(9.80×18)
vf=176.4 m.s-1

Video reference: https://www.youtube.com/watch?v=vxFYfumAAlY
## 9.2 Braking

Braking is an application of frictional force to reduce the speed of the moving object and bring it to halt. Friction is necessary to start, stop and change the direction of the rolling object.

To bring the rolling object to half frictional force is applied between object and the surface. The friction allows the wheel to hold in pure rolling motion, which prevents the slipping which skidding motion.

#### 9.2.1 Braking Force and Braking Torque
The normal reaction on the wheel is one of the primary considerations to remember when determining the braking force, as the braking force depends primarily on the friction ratio between the tyre and the ground and 38 normal reactions on the axle.
The factor in which braking force is depend is COF acting between tire and the ground which decides the magnitude of the applied force required.

#### 9.2.2 Method to control Wheel Locking
In the present scenario the braking force may be controlled by two methods.
1. ABS
2. EBD

#### 1. Anti Lock Braking System (ABS)

ABS is a safety technology used to prevent the vehicle wheel locking during braking at high speed. It helps to maintain the vehicle directional stability and control the vehicle on severe braking in uneven road conditions.
##### ABS Operation
This works efficiently by tracking each wheel's rotational speed, and during braking, regulating the brake line pressure on each wheel.

Ref: https://tse1.mm.bing.net/th?id=OIP.zN3E-36P58Mnih7rIQwFTQHpi&P=0&w=258&h=172

ABS does no work on snow and loose gravel because there is no peak. Encoders detect excessive wheel slippage and not lock-up. The sensors - one at each wheel, send a variable voltage signal to the control unit, which monitors these 43 signals, compares them to its program information, and determines whether a wheel is about to lock up

#### Coefficent of friction Vs Slip on various surfaces

Ref: https://tse2.mm.bing.net/th?id=OIP.qQlh4AVWuWvmtyeiyoYdWQHaF9&pid=A

When a wheel is certain to lock up, the control unit signals the hydraulic unit at that wheel's brake pedal to reduce (or not further increase) the hydraulic pressure, which helps preserve vehicle stability and steering control in emergency braking conditions as shown in Figure. Modulation of pressure is done by solenoid valves which are operated electrically.

### 2. Electronic Brake Force Distribution (EBD)
An extension of anti-lock braking system (ABS) technology, EBD monitors rear-wheel braking based on front and rear wheel traction failure monitoring when the brakes are applied. By regulating the distribution of braking force to the front and rear wheels by passenger and payload, EBD minimizes variations in braking performance whether vehicle load is light or heavy as LTE is greater with laden automobiles.

Ref: https://tse4.mm.bing.net/th?id=OIP.FMpxOFo-ECEHg1X2y87wHAHaE8&pid=A

Distribution of braking force is now carried out under the electric energy of the electronic control unit ( ECU) for the skid control. The skid management ECU controls the braking force exactly according to the operating conditions of the vehicle.

Generally the load transfer effect reduces the load on the rear wheels when the brakes are applied. Once the skid control ECU detects this state (based on the feedback of the speed sensor), the brake actuator is signaled to regulate the rear braking force so the vehicle stays under control during the stop.

The amount of force applied to the rear wheels varies according to the deceleration rate of 45. The amount of braking force applied to the rear wheels often varies depending on whether or not the carries a load.

The load applied to the inner wheels reduces when the load added to the outer wheel increases as the brakes are applied when the vehicle is cornering. If the skid control ECU detects this state (based on the feedback of the speed sensor), the brake actuator is indicated to regulate braking force between the left and right wheels to avoid skid. Figure indicates an EBD response for the vehicle.

It balances the brake force between left and right, and if there is some variation in the degree of the braking force between the left and right wheels, the car can be exposed to a yawing moment that affects the vehicle's stability.

Ref: https://tse1.mm.bing.net/th?id=OIP.5bNFaaTWRK-M-wEmbgJ_IAHaDv&pidw=317&h=161

Video reference: https://www.youtube.com/watch?v=6H7nwlT_qNY

## 9.3 Suspension System

Suspension is the term given to the system of springs, shocks absorbers and linkages which link a vehicle to its wheels.This acts as a dual purpose, helping to carry and improve the stability of the vehicle. Suspension protects and defends the body and any load or cargo from injury and tear.
Source: https://www.kylinmotors.com/wp-content/uploads/2016/04/suspension-repair.jpg

#### (Refer Chapter1 to know about the suspension types)

#### Suspension System Terms

• **Camber**: Looking directly at the front of the vehicle, camber refers to the tilt in (+) or out (‐) of the bottom half of the tire.
• **Caster**: Looking directly at the side of the vehicle, caster refers to the tilt rearward (+) of the bottom half of the tire.
• **Toe**: Looking directly at the top of the vehicle, toe refers to the slant in (+) or out (‐) of the front half of the tire.
• **Jounce**: Jounce refers to the bounce or vertical movement of the vehicle suspension upward when it contacts a bump in the road.
• **Rebound**: Rebound refers to the movement of the vehicle suspension in the opposite direction of jounce.
• **Shimmy**: Shimmy is an uncontrollable oscillation of the steering system experienced by two opposing wheels.
• **Knuckle**: The knuckle is the suspension component that incorporates the spindle or hub that the wheel bearings and wheels mount on.
• **King Pin**: The king pin is the vertical component in the knuckle that the wheels turn on when the vehicle is steered.
• **Spindle**: The spindle is the long tapered bar‐shaped piece that is fitted to the knuckle on which the wheel bearings and wheels are mounted.
• **Hub**: The hub is the hollow part of the knuckle that replaces the spindle in mounting the bearings that support the wheel.
• **Ball Joint**: A ball joint is a fastener or connector that allows movement in all directions.
• **Tie Rod**: A tie rod is a component that firmly connects one wheel of a vehicle to the wheel on the opposite end to provide steering.
• **Track Bar**: A track bar is a rod that connects a suspension beam to the frame to give lateral support.
• **Unsprung Weight**: Unsprung weight is the total weight of all components in a vehicle that are not dampened by the springs and shocks like the wheels and other closely associated equipment.
• **Scrub**: Scrub is the lateral movement of a tire against the pavement due to suspension system camber changes during jounce and rebound.

source: https://i.pinimg.com/originals/96/23/56/962356f55b5ac76c7d9a4ec0a17a7891.jpg

Source: https://cdn.hswstatic.com/gif/car-suspension-1.gif

**Calculations involved in suspension system**
The vehicle's suspension system decides the vehicle's performance and it carries an automobile's most crucial roll. To make it perfect, calculation for a suspension system should be done with care. The estimate and the assumptions and the estimates to be made are.,

1.Decide track width, wheel base, type of suspension, ground clearance.
2.Assume the CoG based on the location of the engine. 40% and 60% weight distribution most probably for a rear engine vehicle.
3.Calculate the scrub radius required, camber, caster, kingpin inclination required.
4.Make a 2D sketch of the suspension system to get the length of the control arms and their angle.
5.The 2D diagram will give you the parameters such as Roll center, instant center.
6.And using these parameters Carry on with the calculation for the load transfers for different dynamic conditions.
7.The calculation for the load transfer will give you the other parameters such as,
* Roll rates (to be assumed at the first).
* Lateral and Longitudinal acceleration.
* Roll gradient.
* Lateral weight transferred.
* Ride rate for the suspension travel selected.
* Ride frequencies.
* Wheel rates.

8.Decide the Installation ratio, and get the Spring stiffness.

## 9.4 Steering system of Automobile

Ref: https://tse3.mm.bing.net/th?id=OIP.x8zPnIfAmYmv9luGMyZ4wAHaHa&pid=Api&P=0&w=300&h=300

The car steering system is the most important part in automobile vehicle steering control, respond so well to the driver while driving.

The system allows a driver to use only light forces to steer a heavy car.
Steering is also possible by the turning of the rear wheels, which is used generally in low-speed slow floor vehicles, for lifting and transporting the heavy parts to a short distance for example forklift.



Ref:https://tse4.mm.bing.net/th?id=OIP.GrSQHZ-JrVzuHM0zoUFfHQHaIR&pid=Api&P=0&w=300&h=300

Automobiles are always equipped with front-wheel steering. A simple sketch of a car steering system as shown in the figure.

### 9.4.1 Working of Steering System
Steering system will convert the rotary motion of the steering wheel into the angular turn of the front wheels.Steering wheel rotates the steering column.

The steering gearbox is fitted to the end of this column. Therefore, when the wheel is rotated, the cross shaft in the gearbox oscillates.The cross shaft is connected to the drop arm. This arm is linked by means of a drag link to the steering arms.

Steering arms on both wheels are connected by the tie rods to the drag link.When the steering wheel is operated the knuckle moves to and fro, moving the steering knuckle are connected to each other. One end of the drag link is connected to the tie rod. The other end is connected to the end of the drop arm.

### 9.4.3 Purpose of a Steering System
For effective control of the vehicle throughout its speed range with safety and without much effort to the driver on different types of the road surface, proper steering is necessary.

For proper performance and useful service of the automobile, it is necessary that the moving vehicle should be under the perfect control of the driver. Thus the control of the automobile is done by means of a steering system which provides directional changes to the moving automobile.

### 9.4.4 Function of Steering System
The important function of steering system as follows:

* With the help of the steering system, the driver can control the vehicle.
* The steering provides stability to the vehicle on the road.
* It minimizes tyre wear and tear.
* It prevents road shocks from reaching to the driver.
* The steering provides self-rightening effect after taking a turn.

### 9.4.5 Wheel Alignment
Wheel alignment is defined as the correct adjustment of the pivot axes controlling the movement of the wheels.

The wheels alignment, therefore, refers to the correct positioning of the front wheels and steering mechanism for promotion easy of steering, reduce tyre wear to a minimum as well as to provide directional stability to the vehicle.

Proper aligned front wheels result in.
* Steering comfort.
* Uniform wear of tyres.
* Minimum energy consumption.
* Minimum vibrations.
* No wheel wobbling.
* Reduce the driver effort to turn the vehicle.
* To achieve self-centring of the wheel after turning.
* To achieve directional stability of the vehicle while running.

### 9.4.6 Types of The Steering System in an Automobile
Following are the three types of steering system:

1. Bicycle steering.
2. Turntable steering or centre pivot steering.
3. Ackarman steering or side pivot steering.

### 1. Bicycle Steering

Ref: https://tse2.mm.bing.net/th?id=OIP.IDEqeqrU48QBd1rZvx24SwHaEK&pid=Api&P=0&w=277&h=157
In these types of steering system, the rare wheel is fixed while the front wheel is steered. For a safe turning, it is essential that the two wheels must roll about a point. In this case, the perpendicular of the front wheel when produces cut the addition of the perpendicular to the rear wheel and that point is saying as the instantaneous centre.

### 2. Turntable or Centre Pivot Steering

Ref: https://mg.com/images/i/391261507155-0-1/s-l1000.jpg
In a four-wheel vehicle, the front two wheels are mounted on the axle and the axle, in turn, is fixed to a turntable having a single pivot.When the front wheels are turned, the whole front axle is turned about the central pivot. In this case, also the perpendiculars of all the wheels meet at a point during any turn, so that the turning is safe and wheels roll freely.

This type of steering system is commonly used in horse-drawn coaches and trails. This is unsuitable for automobile vehicle because it is unstable at high speeds. Moreover, a centre pivot steering arrangement requires a lot of space and because for the whole axle to turn.

### 3. Ackerman Steering or Side Pivot Steering
Ref: https://tse4.mm.bing.net/th?id=OIP.YfH8Ox31kvv5HT8xavPSmQHaFj&pid=Api&P=0&w=

This is the modern steering layout of almost all automobiles. In this type of steering system, each front wheel is turned individually about the side pivot.The front axle is pivoted on either side of the axles. And as the stub axles, the wheels are mounted. The stub axles are turned by steering arms connected to the tie rod.

The steering arms are not parallel but are inclined. The line produced from the inclined arms will meet at the centre of the rear axle line forming an angle called the “Ackerman Angle”.

To obtain a good alignment it is necessary to understand the following factors,
1. Camber (Wheel rake or Camber angle).
2. Caster.
3. King Pin inclination.
4. Toe-in.
5. Toe-out.

#### 1.Camber
The angle between the centre line of the tyre and the vertical line, when viewed from the front of the vehicle, is known as camber. When the wheels are tilted outwards at the top is called positive camber, and if titled inward at the is called negative camber. Equal camber angle is provided on both the front wheels.

Ref: https://tse4.mm.bing.net/th?id=OIPZAHaFj&pid=Api&P=0&w=224&h=169

With the positive camber, wheels become verticle under load on the tyre will have full contact with the road, hence the tyre wear will be uniform. If the positive camber is excessive then tyres outer edge will rear will to wear out faster. If the negative camber is excessive the tyres inner edge will wear out faster.

Unequal camber on both the front wheels will results in wheels vibration at low speed. Older models have considerable camber. Present-day cars use improved design and materials they have very little camber. The camber should not exceed 2°. The camber on modern vehicles is adjusted by means of an eccentric cam in the control arm shaft.

#### 2.Caster
The Kingpin axis or steering axis may be tilted forward or backward from the vertical line. This tilt is known as Caster. Caster Angle: The caster angle is the angle formed by the forward or backward tilt of the steering axis from the vertical when viewed from the side of the wheel.
Ref: https://tse1.mm.bing.net/th?id=OIP.0DKdoSw3gHaE8&pid=Api&P=0&w=239&h=160
A backward tilt is known as a positive caster and a forward tilt is known as a negative caster. If the caster is not equal on both sides it will cause the vehicle to pull to the side of the wheel having lesser caster angle. The caster angle in modern vehicles varies from 2° to 8°.

##### Purposes of Caster
* To maintain directional stability and control.
* To increase steering stability.
* Reduce drives effort to turn the vehicle.

#### 3 King Pin Inclination

Ref: https://tse4.mm.bing.net/th?id=OIP.PQiEE-Dy6-nA8Dxeb0&w=194&h=189
The angle between the vehicle line and centre of the kingpin or steering axis, when viewed from the front of the vehicle, is known as Kingpin inclination.

The Kingpin inclination in modern cars varies from 7° to 8°. It must be equal on both sides. It is greater on one side than the other, the vehicle will tend to pull to the side having a greater angle.

##### The main functions of Kingpin inclination as follows,
* It helps in self-centring of wheels after taking a turn.
* To provide directional stability.
* It reduces steering effort.

#### 4. Toe-in
Front wheels are slightly tilted inward at the front of the distance between the front wheels at the front (A) is less than the distance at its rear (B) measured at the height of the hub level and at the centre of the wheel tread.

The difference in its distance is ‘Toe-in’ (B-A). it is usually 2 to 3 mm. The purpose of the toe-in is to overcome the bad effect of camber. The toe-in is adjusted by tie-rod ends.

#### 5. Toe-out
Whenever the vehicle is taking a turn with Ackerman steering geometry the inner wheel turn more degrees that the outer wheel so that the perpendiculars of all four wheels at a point when produced. This point is called the instantaneous centre so that all the wheels roll very easy without scuffing.

### 9.4.7 Types of steering system depending upon the leverage
There are two types of steerings depending upon the leverage provided between the road wheel and the steering wheel and also the number of shocks and vibrations transmitted from the road wheels to the steering wheels, namely,
1. Reversible steering.
2. Irreversible steering.

##### 1.Reversible Steering
Reversible steering is one in which the gear ratio is 1:1.
For example bicycle or scooter steering. In gear case, any angular movement of the handle causes the same angular movement to the wheel and the wobbling or vibrations of the wheel is faithfully transmitted to the steering handle. This arrangement is suitable for only bicycles, motorcycles, scooters etc.

##### 2. Irreversible Steering
Here gear reduction between and wheels and the steering wheel is very high. Ex-In road rollers it is about 40:1.
Here very high gear reduction is necessary. Because the load carried on the wheel is very high. With this type of steering, there will not be any transmission of notion due to vibration of the wheel from road wheels to steering wheels.

### 9.4.8 Steering Gears

If the steering wheel is connected directly to the steering linkage it would require a great effort to move the front wheels. Therefore, to assist the driver a reduction system is used. The Steering gear is a device for converting the rotary motion of the steering wheel into the straight-line motion of the linkage with a mechanical advantage. The steering gears are enclosed in a box called the steering gearbox.

### Types of Steering Gears
Following are the eight important steering gears:
1. Recirculating ball steering gear.
1. Rack and pinion steering gear.
1. The Worm and sector steering gear.
1. Worm and roller steering gear.
1. Worm and ball bearing nut steering gear.
1. Cam and roller steering gear.
1. The Cam and peg steering gear.
1. Cam and double lever steering gear.

### 1. Recirculating Ball Steering Gear

Ref: https://tse1.mm.bing.net/th?id=OIP._lDcDcqsbDjzz8FsW8dMQgHaF7&pid=Api&P=0&w=203&h=163
The circulating ball gear is similar to the worm and ball bearing not steering gear. The balls are contained in half nut and a transfer tube. As the cam or worm rotates, the balls pass from one side of the nut to the transfer tube to the opposite side. As nut cannot turn, and movement of the balls along the track of the cam carries the nut allowing with it and rotates the rocker shaft.

### 2. Rack and Pinion Steering Gear

Ref: https://tse3.mm.bing.net/th?id=OIP.hR-3pUKuxCUlzfbgUl4M-AHaEV&pid=Api&P=0&w=279&h=164
In the rack and pinion steering gear, a pinion is mounted on the end of the steering shaft. It engages with the rack which has a ball joint at each end to allow for the rise and fall of the wheels.
The roads connect the ball joints to the stub excels. The rotary movement of the steering wheel turns the pinion which moves the rack sideways. This movement of the rack is converted into wheels.

### 3. Worm and Sector Steering Gear

Ref: https://tse2.mm.bing.net/th?id=OIP.o6uvMdFoLS5tXx9dsNPkWwAAAA&pid=Api&P=0&w=219&h=164
In the worm and sector steering gear, the worm on the end of the steering shaft meshes with a sector mounted on a sector shaft. When the worm is rotated by rotation of the steering wheel, the sector also turns rotating a sector shaft. Its motion is transmitted to the wheel through the linkage.
Note that 6the sector shaft is also known as pitman arm shaft, pitman shaft, roller shaft, steering arm shaft, cross shaft.

### 4. Worm and Roller Steering Gear

Ref: https://tse1.mm.bing.net/th?id=OIP.5VDQdaxiMV3ArF2wQU3BiQHaIa&pid=Api&P=0&w=300&h=300
In the worm and roller steering gear, a two-toothed roller is fastened to the sector or roller shaft so that it meshes with the threads of the worm gear or shaft at the end of the steering shaft or tube.
When the worm shaft is turned is it causes the roller to move in an arc so as to rotate the roller shaft, and at the same time turn on the pin connecting it to the shaft. The roller is mounted on a ball bearing.

The worm shaft is mounted on bearing designed to resist both radial and end thrust. This type of steering gear is widely used on American passenger cars.

### 5. Worm and Ball Bearing Nut Steering Gear

Ref: https://tse4.mm.bing.net/th?id=OIP.DlviBWMwHaF3&pid=Api&P=0&w=230&h=183
In the worm and ball bearing nut steering gear, a ball nut is mounted on the worm of the steering shaft. The worm and the nut have mating spiral grooves in which steel balls circulate to provide a frictionless drive between the worm and nut.
Two sets of balls are used, with each set operating independently of others. A ball return guide is attached to the outer surface of the nut. When the steering shaft is turned to the left or right, the ball nut is moved up and down by the balls which roll between the worm and nut.
A sector gear mounted on the sector shaft meshes with the ball nut, so that it gets motion by the ball nut.

### 6. Cam and Roller Steering Gear
Ref: https://tse1.mm.bing.net/th?id=OIP.Ke3wNUiu2IYxFkDXOw67QgHaFj&pid=Api&P=0&w=200&h=151
In the cam and roller steering gear, a cam meshes with the roller. As the cam rotates, the roller is compelled to follow the cam and in doing so causes the rocker shaft to rotate, thus moving the drop arm.
The contour of the cam is designed to mesh with the arc made by the roller so maintaining a constant depth of mesh and evenly distributing the load and wear on the mating parts.

### 7. Cam and Peg Steering Gear
Ref: https://tse2.mm.bing.net/th?id=OIP.2c1YBPiEJ2lJ_jhECxve1QHaEt&pid=Api&P=0&w=255&h=163
In the cam and peg steering gear attached to the rocker arm is a tapered peg which engages in the cam. When the cam rotates, the peg moves along the groove causing the rocker shaft to rotate.

### 8. Cam and Double Lever Steering Gear
Ref: https://tse4.mm.bing.net/th?id=OIP.sdPw58mbAGcYU1oC0kY-hAHaEK&pid=
In the cam and double lever steering gear, a special worm called a cam, replaces the worm used in the two types worm and sector steering gear and worm and roller steering gear.

The cam is cylindrical in shape, its actuating part being a groove of the variable pitch made narrower at the centre than at the end. This provides non-reversibility in the centre part of the cam where most of the car steering takes place.

The twin levers are mounted on the cross shaft and are located so that the stubs engage the cam from the side. When the cam is turned, the stubs move along the cam groove to cause the lever to swing through an arc and thus turning the cross shaft.

Video reference: https://www.youtube.com/watch?v=_k0Gjre1QlY

## 9.5 Rollover Control
A rollover is defined as any vehicle rotation of 90° or more about any true longitudinal or lateral axis.

Roll Stability Control is active safety system which reduces the risk of rollover of the passenger vehicles in some critical maneuvers such as severe cornering and during steering suddenly. This system is especially useful for the vehicles having the high centre of gravity (C.G.) like SUVs as they are more prone to rolling over.

### Rollover occurring conditions
• Traveling at high speed on curved road.
• Sever cornering maneuver.
• Traveling on collapsing road and suddenly providing steering input for a vehicle with a low level of roll stability.
• Losing control due to a rapid decrease of friction, such as driving on icy road.
• Laterally sliding of the road.
• Sliding from a cliff.

Ref: https://tse2.mm.bing.net/th?id=OIP.ErMBM2yzLlRNzF1iVR5w&pid=Api&P=0&w=300&h=300

### Factors effect vehicle to Rollover
• These factors are tire and vehicle characteristics, environmental conditions, and drivers.
• Rollover can happen on a flat road, on a cross-slope road, or off road.
• Rollover can be divided into two categories: tripped rollover, and untripped rollover.
• Tripped rollover is caused by a vehicle hitting an obstacle.
• Traveling at high speed on a curved road: When a vehicle travels on a curved road, lateral centrifugal force will pull it in an outboard motion, as shown in below figure.

### Effect of Speed and Centrifugal Force
• If a vehicle is forced to take instant action, the centrifugal force is multiplied.
• If you double your speed, the overturning force will be four times higher. As the speed increases the trailer tracks wider and forces increase on rear axle. This means that a slight increase in speed can be critical.
• It increases by squaring so that 10% increase in speed causes 100% increase in force. Double the speed is four times the force.

Ref: https://tse4.mm.bing.net/th?id=OIP.ZdItlTq9JsTZOa1WDqgHaFV&pid=Api&P=0&w=237&h=172

### 9.5.1 Working of Rollover control system
While taking a turn, it may happen that the vehicle fails to keep contact with the ground & maintaining proper ground clearance resulting in a rollover, if the maneuver is critical and is done at very high speed. In such a situation, Roll Stability Control comes into action.

RSC works with the help of a gyro sensor and Electronic Stability Program (ESP/ESC) of the vehicle. The gyro sensor continuously monitors the roll angle of the vehicle with respect to ground. If it is observed that roll angle of the vehicle is exceeding its normal limit, then this system reduces the speed of the entire vehicle or specific wheels by applying brakes with the help of ESP. Some systems also possess the ability to reduce the engine power. This system reduces the chances of tumbling over the curves.

Ref: https://tse2.mm.bing.net/th?id=OIP.XUZ2LKqXpFuxggHaFi&pid=Api&P=0&w=215&h=161

Video reference: https://www.youtube.com/watch?v=Mmja6bC03Yw

## 9.6 Tyres
Tyres are one of the most important and most overlooked parts on a modern day vehicle.They are the main contact your vehicle has with the road

### 9.6.1 Tyre Dynamics

### 1. SLIP ANGLE
To fully understand tyre dynamics, the first thing you need to get to know is slip angle. This is defined as the angle (degrees) formed between the actual direction of travel of the wheel and the ‘pointing’ direction of the wheel (perpendicular to the axis of rotation). There is always an angle between the two when a lateral acceleration is experienced by a vehicle.

Ref: https://tse3.mm.bing.net/th?id=OIP.BOt28lzdqUOxY8FEQGCOeAAAAA&pid=Api&P=0&w=181&h=163
The diagram above shows how the elements within the contact patch have been displaced in alignment with the direction of travel. These elements then return to the neutral condition towards the rear of the contact patch as the reaction force reduces.

Ref: https://tse4.mm.bing.net/th?id=OIP.1Lvq1BTZ227kc5Rj-VwvFAHaIE&pid
Typical trend in slip angle vs lateral force – a clear peak in lateral force can be seen at around six degrees of slip angle.

Whenever slip angle is introduced, the contact patch deforms as lateral forces act on the tyre. This deformation generates strain (elongation) within the molecular structure of the tyre rubber. Furthermore, the elasticity of the tyre compound resists this strain which generates a force normal to the axis of rotation.

This stretch-relaxation cycle that the tyre repeats every revolution also generates internal friction and therefore heat within the tyre; increasing tyre grip. This increases up to a point until the tyre rubber has been overworked and grip reduces dramatically, also known as the ‘cliff’.

### 2 CORNERING STIFFNESS
A fundamental measure of the grip capability of a tyre in the lateral sense is known as the cornering stiffness. This is expressed as the force generated per degree of slip angle (N/°). For a given slip angle, a tyre with a higher cornering stiffness will produce a greater lateral acceleration and this is a key performance measure of any tyre.

### 3 SLIP RATIO
The concept of slip angle is applied in describing lateral force production only. In the longitudinal sense, this is known as the slip ratio. The slip ratio is similar to slip angle but instead of being measured in angular displacement, it relates the amount of slip a tyre experiences relative to a sliding condition. For example, a slip ratio of 0 is a free rolling tyre and a ratio of 1 is a tyre that has lost traction. A general trend seen in tyres is a longitudinal force peak at a slip ratio of around 0.3 – 0.4.

### FRICTION CIRCLE

Ref: https://tse3.mm.bing.net/th?id=OIP.SsXfTmOudVZlkwEs9NxXGwHaGN&pid=Api&P=
The blue circle denotes the current acceleration of the vehicle. Here it is showing that the car is braking whilst making an easy left turn.

The last fundamental of tyre dynamics that is necessary to understand is that of the friction circle or g-g diagram. The friction circle graphically illustrates the limits of a tyre generating both longitudinal and lateral acceleration simultaneously, and allows understanding of how the vehicle is being driven relative to this.

### 4 THE COEFFICIENT OF FRICTION – ‘MU’

Ref: https://tse1.mm.bing.net/th?id=OIP.kIkU1P3W6TUJv93eV2X_9QHaGH&p
Graph of CoF vs reaction force showing the disproportionality of their relationship. This data is taken from a FSAE single seater
The Coefficient of Friction (CoF), sometimes referred to as mu (μ) relates the frictional force to the reaction force between two objects in contact

It is important to understand that the CoF does not increase proportionally with increasing reaction force (vertical tyre load). In other words, the doubling of the reaction force does not double the CoF and therefore does not double the tyre grip level.

This becomes important to vehicle dynamics in understanding grip levels when the reaction force is not equally loaded across the left and right, or front and rear of the car due to weight transfer.

Imagine the contact patch as a matrix of discrete elements. A wider tyre reduces the contact pressure at each element for a given vehicle weight which increases the CoF. With this, each element of the tyre is able to generate a slightly lower force, but this balance is outweighed by the presence of a larger number of elements (contact area). The effect is a net increase in tyre grip. This also explains why motorsport often uses the largest tyres possible in the search for performance.

### 5 Compound Temperature
The temperature of the tyre compound affects adhesion by increasing both the conformance and the penetration of peaks and valleys in the road into the contact patch. This also increases the rate of chemical reaction between the tyre rubber and asphalt, but only up to a point, after which the tyre will “go off” and grip levels reduce.

### 6 Inflation Pressure
Due to the flexible nature of tyre rubber, inflation pressure introduces deformation at the contact surface, ranging from a concave profile (low pressure) to a convex profile (high pressure). This affects the surface area of the contact patch. Somewhere in between the two is a flat profile which provides maximum contact area and the optimal adhesion. This is the goal of the dynamicist.

Interestingly, sometimes if teams are struggling for tyre temperature, they boost the tyre pressures which results in a convex profile and a very narrow contact patch. This contact patch heats up quicker, which then radiates throughout the rest of the tyre, increasing its overall temperature.

However, it is important to understand the properties of gas in that for a given volume, if the temperature increases so does the pressure – leading to a compounding effect of both reduced adhesion and reduced contact patch area.

### 7 Track Conditions
Variables such as track surface roughness, wet track, dusty track all influence the level of adhesion.


Surface roughness can be described by micro and macro roughness

Overall, in the search for maximising cornering stiffness, the CoF must be maximised at all times. This is why the wheels, suspension chassis and set-up are all vital tools which can help to tune tyre grip.

Video reference: https://www.youtube.com/watch?v=BPYxLeW6WjM
### 9.7 Ride Comfort
Ride comfort control systems improve vehicle comfort and increase driving pleasure. As drivers will experience the ride in a different way depending on how these systems are adjusted, the systems have considerable influence on the vehicle.

A ride should be as pleasant as possible for the occupants of a vehicle. Systems such as Active Body Control (ABC) ensure that any road irregularities are cushioned so that passengers hardly notice them.

In order to continuously improve ride comfort, ride comfort control systems are undergoing further development and are also becoming increasingly networked. In contrast to ABC, by integrating camera-based sensor data, cross-domain systems such as Magic Body Control are able to anticipate road irregularities and react accordingly.

Some vehicle have the option of switching between various driving modes. The driver can create a standard, sporty or energy-efficient driving experience with just the push of a button. The ride comfort control system includes different control characteristics for each driving experience.
Due to the continued development of the systems, the broad range of vehicle variants, and the various driving styles which must be taken into account, there is considerable effort involved in the testing and validation of ride comfort control systems.

The use of virtual test driving makes it possible to manage this effort. With the help of our simulation solutions, you can test and approve systems at an early stage of development – and in the context of the whole virtual vehicle.

Understanding ride comfort starts with understanding the basics of suspension, in specific the 2 main components of suspension – springs and dampers:

### 9.7.1 Springs:
Ref: https://tse4.mm.bing.net/th?id=OIP.k8g9mQHaHa&pid=Api&P=0&w=300&h=300
These are coil springs, the most common type of spring found in modern passenger vehicles.
Springs support the weight of the vehicle. They’re the most easily identifiable piece of a car’s suspension visually (leaf springs aside unless you know what you’re looking for), and are the main controlling component in whether or not a vehicle rides ‘hard’ or ‘soft’. When you drive over bumps or through dips, the firmness of the springs dictates how easily the wheels recoil towards the body, or how quickly they rebound down into the dip to keep the body of the car level. Hard springs resist body roll, whereas soft springs result in large amounts of body roll – a trait which can greatly improve, or reduce handling ability, and to an extent, ride comfort.
Springs control the firmness of a ride.

### 9.7.2 Dampers:
Ref: https://tse3.mm.bing.net/th?id=OIP.kvzMnIzYcEjSc7oN1FTx0QHaLc&pid
These are common shock absorbers, otherwise known as ‘dampers’.
Dampers are more commonly known to the layman as shock absorbers. As their more common name suggests, these are responsible for absorbing shocks and bumps. Where springs control the firmness of a ride, dampers are the main controlling component in the comfort of a ride over anything less than a perfect surface.

Dampers, or shock absorbers, feature a piston housed within a fluid-filled cylinder. When travelling over corrugated surfaces and small road imperfections, the piston reacts and moves within the cylinder, with the compression of the oil converting vertical movement into other forms of energy (mainly heat) and cushioning the ride.
Dampers, simply put, absorb vibrations and prevent them from permeating into the cabin.

### 9.7.3 Ride Comfort:
Ride comfort isn’t just about how hard or soft a car feels. Ride comfort is the culmination of firmness and the way a car’s suspension filters out imperfections on the road surface. The more comfortable a car is, the less you’ll feel every bump through your seat, and ultimately your body – even if you may feel those changes through the steering wheel in a truly communicative driver’s car.

Take for example a car with soft springs (generally thought to be comfortable) – this will absorb larger bumps in the road quite easily. However, if equipped with sub-standard dampers, every single little bump in the road surface would shake its way into the cabin – likely resulting in more visits to the chiropractor’s office than the soft suspension is worth.

On the contrary, a car equipped with firm springs and a sporting inclination will be affected by larger bumps, resulting in the need to take speed bumps slower. But, if said car is equipped with high performance dampers, every ripple in the road’s surface will be absorbed and cushioned resulting in a smooth ride, free from vibrations through the cabin.

In the second example, a large bump can be pre-empted and planned for, but small imperfections would be effortlessly absorbed – whereas the first example would need constant micro-management to negotiate pockmarked roads in comfort, and even the best driver wouldn’t be able to completely take the edge off a poor road.

### 9.7.4 Other factors affecting ride comfort:
While suspension, predominantly dampers, plays a massive role in ride comfort, there are other factors that influence how comfortable a car will be.

Tyres can have a relatively big role to play too – some tyres are engineered for comfort and reduced noise, while other are more performance orientated. Generally, firmer compound tyres will be more uncomfortable. Low profile tyres also reduce comfort as they reduce the amount of cushioning when the wheel meets imperfections on the road surface.
However, no traditional tyre compromises ride quality more than run-flat tyres (RFTs). With their rigid side walls, the rubber compound RFTs are made of does a poor job of absorbing bumps.

### 9.7.5 Improving and adjusting ride comfort:
When developing a car, manufacturers often can’t justify the costs of equipping high-quality dampers to a budget, or mass-production vehicle. They opt instead for cheaper dampers that improve the affordability and give ample comfort levels for the intended target markets.

Some vehicles – usually performance vehicles – feature dampers that can be adjusted from within the cabin. Magnetorheological dampers feature a magnetic fluid in the dampers instead of the usual oil. The viscosity of this fluid can be changed by electro-magnetic currents to make the dampers firmer or softer depending on road conditions. This is usually controlled via buttons or dials in the cockpit.

Alternatively, ride comfort can be managed and improved in a variety of aftermarket ways. For example; equipping adjustable dampers that can be tuned for different scenarios – these types of dampers are a great option for cars that need to double up as weekend track cars, and daily drivers.

There are many determining factors in a vehicle’s ride comfort, but none has as big a role to play than the dampers. A firmly sprung vehicle can be made comfortable with dampers that mitigate every undulation in the road, and likewise a soft suspension can be crashy if every pebble on the road reverberates

Video reference: https://www.youtube.com/watch?v=_k0Gjre1QlY

### 9.8 Free body of vehicle

Every body or object in the universe exerts different forces on the surroundings, as well as experiences the effect of various forces on it. It is possible to study such physical entities with the help of a free body diagram.

The free body diagram of a car traveling at a constant speed consists mainly of five forces, when considered in an actual situation. These vectors are that of friction, gravity, normal force, air resistance, and engine driving force. In a hypothetical situation without external forces (friction and air resistance), only the three remaining forces will act on the vehicle.

A free body diagram is defined as an illustration that depicts all the forces acting on a body, along with vectors that are applied on it. Apart from the acting forces and subsequent work done, the moment magnitudes are also considered to be a part of such diagrammatic representations. These diagrams are then used to calculate these forces, estimate their directions, and also to thoroughly analyze them. One should keep in mind that these representations only consist of vector quantities, and scalars like distance and speed are not to be drawn in the diagrams.

### 9.8.1 Explanation
Free body diagrams are always represented in the form of two-dimensional figures, which consist of the ‘X’ and ‘Y’ axis. In classical mechanics. The three main aspects that need to be considered in drawing these diagrams are: the direction of the force, the magnitude of the force, and the origin/source/application point of the force.

### 9.8.2 Types of Forces

### Applied Force
This vector is applied to cause a change in the state of the body (in terms of rest or motion), along with an effect on other objects, surfaces, or mediums. Its magnitude depends on the action of all the other forces, and in some instances, more than one applied force may be present. When this force is exerted, work is done by the body.

### Normal Force
It acts in exactly the opposite direction as that of the gravitational force, and perpendicular to the surface. In most cases, the surfaces are shown to be horizontal, and hence, the normal force can be said to act in the upward direction. Simply said, it is the force exerted by the surface on which the body rests, to counter gravity.

### Gravitational Force
According to Newton, every object attracts every other object with a force that is directly proportional to the product of their masses, and inversely proportional to the square of distance between them. Thus, any object on land, air, water, or even space will experience some effect of gravity. Its direction is opposite to that of the normal force. On our planet, the average value of gravitational attraction is about 9.8 m/s2.

## Frictional Force

This vector acts in the opposite direction to the applied force, and exists because of some discrepancies present on the surface of contact with the body. Though its magnitude is mostly small as compared to the applied force, it can cause the opposite effects as compared to those of the applied force on the body, thus slowing it down (deceleration). Smoother the surface, less will be the friction.

### Tensional Force
It exists when an object is stretched or deformed from its original shape and structure. This vector may be influenced by an additional applied force and gravity. Many complex free body diagrams exhibit such vectors, and tensional forces are often accompanied with stress and strain of a body. This might include temporary or permanent deformation of the body.

### Air Resistance/Drag
In case an object is in motion in the air, it shows the presence of air resistance, which acts in the opposite direction as that of the applied force. This vector is also called drag, which can act on the back-end of the body in motion. It is a type of friction, which exists mainly due to the relative movement of the body with respect to the air current movements.

Ref: https://tse1.mm.bing.net/th?id=OIP.hLsB5Idy3u5FJBDzs
A box is being shifted on a horizontal surface towards the right. Thus, the applied force is towards the right, whereas, the frictional force is towards the left. The weight acts in the downward direction due to the effect of gravitational force, while the normal force acts in the upward direction, opposite to gravity.

Ref: https://tse2.mm.bing.net/th?id=OIP.LX2v5Jxzf_vvnvwlMEwU2wHa
The diagram above shows the same box, but on an inclined surface. Thus, the force of gravity will be acting in multiple directions; at an angle to the surface, as well as perpendicular to the surface. The angle of the ramp is 30 degrees. If we assume that the box is accelerating towards the slope bottom, then ‘Fa’ can be said to be equal to ‘mgsinθ’, whereas, the gravitational force perpendicular to the inclined surface is equal to ‘mgcosθ’. In these terminologies, ‘m’ is the mass and ‘g’ is gravitational acceleration.

### 9.8.3 How to Draw a Free Body Diagram

When you draw these diagrams, you first have to recognize the various kinds of forces that are acting on the object. After this, note down their directions, along with the respective symbols. Then, you can draw any representative geometric figure like a square, circle, or a rectangle, etc., along with all the particular force directions in the form of arrows.

The labellings and values, if present, can also be written. In the final step, describe all the forces briefly in order so that you clearly understand the entire diagram. Mostly, if a single body is concerned, all the forces will coincide at the center of gravity of that object.

One important thing to keep in mind is to draw the arrow lengths as per the force magnitude. Also, the net vector for two or more forces acting in different directions is not to be drawn; they can be represented as separate ones. An ‘X’ and ‘Y’ axis is also drawn sometimes so that the orientation of vectors with respect to horizontal and vertical directions can be shown. These axes are either connected to the central point of the diagram, or can be present toward one side.

8.8.4 A cyclist is moving up an incline on a ramp, which has an angle of 30 degrees with the surface
Ref: https://tse2.mm.bing.net/th?id=OIP.TcALEqUu5uUP-Qlk6XkWw

In this scenerio, when a cyclist is travelling the road surface isn't always even, so there will be shift in the force acting on a body when a vehicle moves from flat surface to inclined one. The gravitational force plays an major role which acts in three directions: perpendicular to inclined surface,normal to floor, and in the direction of applied force.

Video referene: https://www.youtube.com/watch?v=

# 9.10 Electric Vehicle Traction Force

Tractive force is the force applied between the tire and road surface to move a car or any vehicle from that position. The maximum permissible traction force that can be applied to the wheels is governed by two things: the weight of the vehicle and the adhesion coefficient between the tire and the road surface.

Traction control is an important element in modern vehicles to enhance drive efficiency, safety, and stability. Traction is produced by friction between tire and road, which is a nonlinear function of wheel slip. Traction control of electric vehicles has drawn extensive attention since electric motors can produce very quick and precise torques compared to conventional internal combustion engines.

### Traction system
A system which causes the propulsion of vehicle in which tractive or driving force is obtained from various devices such as diesel engine drives, steam engine drives, electric motors, etc. is called as traction system.

The traction system can be classified as non-electric and electric traction systems.

### Non-electric traction system

A traction system that doesn’t use electrical energy for the movement of vehicle at any stage is referred as non-electric traction system.The steam engine drive is the best example of a non electric traction system and it is the first locomotive system used before the invention of actual electric traction systems.

The steam locomotive system uses the superheated steam to produce mechanical energy for the movement of vehicle. This may use coal or petroleum as fuel, liberates thermal energy to produce the steam pressure and then it is converted into kinetic energy so that mechanical movement of the vehicle is produced.


Ref: https://tse3.mm.bing.net/

The disadvantages of steam locomotive systems are: low fuel efficiency, poor technical performance, maintenance of a large number of water supply facilities, and high maintenance cost makes them to be replaced by alternative traction systems.

The following are the two types of non electric traction systems.

* Steam engine drive based vehicles
* Internal combustion (IC) engine

### Traction system in EV
Electric traction involves the use of electricity at some stage or all the stages of locomotive movement. This system includes straight electrical drive, diesel electric drive and battery operated electric drive vehicles.

In this, electrical motors are used for producing the vehicle movement and are powered by drawing electricity from utilities or diesel generators or batteries.

It has many advantages over non-electric traction systems such as more clean and easy to handle, no need of coal and water, easy speed control, high efficiency, low maintenance and running costs, etc.

As mentioned above, electric traction systems can be self contained locomotives or vehicles that receive power from electric distribution system Self contained locomotives includes:

* Battery operated electrical drives
* Diesel operated electrical drives

### Supply Systems of Electric Traction

The way of giving the power supply to locomotive unit is generally referred as traction electrification system. Presently, there are four types of track electrification systems are available based on the availability of supply.

* DC traction system
* Single phase AC traction system
* Three phase AC traction system
* Composite traction system

### DC Traction System
In this traction system, electrical motors are operates on DC supply to produce necessary movement of the vehicle. Mostly DC series motors are used in this system. For trolley buses and tramways, DC compound motors are used where regenerative braking is required.

The various operating voltages of DC traction system include 600V, 750 V, 1500V and 3000V.

This three phase high voltage is stepped-down and converted into single phase low voltage using scott-connected three phase transformers.

This single phase low voltage is then converted into DC voltage using suitable converters or rectifier such as power electronic converter, rotary converters, mercury arc converters, etc. The DC supply is then applied to the DC motor via suitable contact system and additional circuitry.


### The advantages of this system include

* In case of heavy trains that require frequent and rapid accelerations, DC traction motors are better choice as compared AC motors.
* DC train consumes less energy compared to AC unit for operating same service conditions.
* The equipment in DC traction system is less costly, lighter and more efficient than AC traction system.
* It causes no electrical interference with nearby communication lines.
* Despite all these advantages, DC electrical system necessitates AC to DC conversion substations relatively at very short distances. This is the main disadvantage of DC traction system.

Video reference: https://www.youtube.com/watch?v=WpOfDI4zoS8

# 9.11 Electric Vehicle Powertrain and Drivetrain

#### 1 POWERTRAIN

The powertrain is a set of components that generates the power required to move and deliver to the wheels.

### 1.1 Powertrains of EVs and ICE vehicles
The Powertrain of an electric vehicle is a simpler system, comprising of far fewer components than a vehicle powered by an internal combustion engine.

Ref: https://tse4.mm.bing.net/th?id=OIP.QnnSIITiJ90

### 1.2 Main components of an ICE vehicle powertrain
An ICE vehicle has several moving parts. It includes Engine, Transmission, and Driveshaft. Power is generated by the engine and transmitted to the driveshaft. Other internal parts and components of the engine, differentials, axels, emissions control, exhaust, engine cooling system, etc.

Ref:https://tse4.mm.bing.net/th?id=OIP.IDMC1_

### 1.3 Main Components of an EV Powertrain
An EV powertrain has 60% fewer components than the powertrain of an ICE vehicle. The components are described below.

Ref: https://tse1.mm.bing.net/th?id=OIP.9_9d6xj-Ye

**Battery Pack:** The battery pack is made up of multiple lithium-ion cells and stores the energy needed to run the vehicle. Battery packs provide direct current DC output.

**DC-AC Converter:** The DC supplied by the battery pack is converted to AC and supplied to the electric motor. This power transfer is managed by a motor control mechanism as a Powertrain Electronic Control Unit that controls the frequency and magnitude of the voltage supplied to the electric motor to manage the speed and acceleration as drivers input via acceleration or brakes.

**Electric Motor:** Converts electrical energy to mechanical energy that is delivered to the wheels via single ratio transmission. Many EVs use motor generates that can perform regeneration as well.

**On-board Charger:** Converts AC received through charge port to DC and controls the amount of current flowing into the battery pack.

Ref: https://tse3.mm.bing.net/th?id=OIP.rvyUY

Apart from the above core parts, there are multiple hardware and software components in an EV powertrain. Electronic Control Unit(ECUs) are software programs integrated with the powertrain components to help data exchange and processing. There are several small ECUs in an EV that perform specific functions. The communication between different ECUs in a vehicle is commonly carried over CAN protocol.

**Battery Management System:** A BMS continuously monitors the state of the battery and is responsible for taking necessary measures in case of a malfunction. BMS performs cell balancing to deliver maximum efficiency from the battery pack. It is responsible for communication with other ECUs and sensors, as well as ECUs to control the charging input, check the current state of charge and share data about battery specifications.

**DC-DC Converter:** A battery pack delivers voltage, but the requirement of different accessory systems like infotainment systems, lights, mirror control. The DC-DC converters help distribute power to different systems by converting the output power from battery pack to the expected level, After conversion, power is delivered to respective smaller ECUs wiring harness.

**Thermal Management System:** Responsible for maintaining optimum operating temperature range for powertrain components.

**Body Control Module:** The BCM is responsible for supervising and controlling the functions of electronic accessories such as power windows, mirrors, security, and vehicle access control.