Course: Electric Motor and Drive Systems for Electric Vehicle

Course code: BEE613D

Faculty: Dr. Marulasiddappa H B

Module 1: History of Electric and Hybrid Electric Vehicles

Introduction

General description of EV princple

Electric vehicle (EV) movement is driven by an electric motor that converts electrical energy into
mechanical energy to propel the vehicle forward. Here's a general description of how EVs move:

1. Energy Source: EVs are powered by electricity stored in rechargeable batteries, typically
lithium-ion batteries, which supply energy to the motor.
2. Electric Motor:
o The electric motor in an EV operates on the principle of electromagnetism. When
electricity flows through the motor's coils, it creates a magnetic field that interacts
with permanent magnets, causing the motor's rotor to spin.
o Unlike internal combustion engines (ICE), EVs use electric motors that provide
instant torque, resulting in smooth and quick acceleration from a standstill.
3. Transmission System:
o Most EVs use a single-speed transmission, which simplifies the drivetrain and
reduces mechanical losses. This is because the electric motor can operate efficiently
across a wide range of speeds without needing gears.
o Some high-performance or specialized EVs might use multi-speed transmissions to
optimize performance.
4. Torque Generation:
o Torque is the rotational force generated by the motor. Unlike ICEs that have a
narrow power band and need to shift gears to keep the engine in its optimal range,
electric motors provide full torque instantly and maintain it over a wide range of
speeds.
o This instant torque is one of the key characteristics of EVs, making them feel
responsive and quick.
5. Power Conversion and Control:
 o The battery supplies direct current (DC), which is then converted to alternating
current (AC) using an inverter, as many EVs use AC motors. The inverter also
controls the motor's speed and power output based on the driver's inputs (e.g.,
accelerator pedal).
o Regenerative braking is another feature in most EVs, where the motor acts as a
generator, converting kinetic energy back into electrical energy to recharge the
battery when the vehicle slows down.
6. Energy Flow:
o The energy stored in the battery is directed to the motor when the accelerator pedal
is pressed, creating movement. The vehicle’s onboard computer systems monitor
and control the flow of energy, balancing performance, range, and efficiency.
7. Vehicle Dynamics:
o EVs typically have a low center of gravity due to the battery placement, which
improves handling and stability. They also have fewer moving parts compared to
ICE vehicles, resulting in lower maintenance needs.
o With advanced control systems, the vehicle can adjust power delivery to optimize
traction, stability, and driving experience, especially in challenging conditions.

Electric and hybrid electric vehicles (EVs and HEVs) have a long history dating back to the early
19th century. Although internal combustion engines (ICEs) dominated for much of the 20th
century, concerns over fuel efficiency and environmental pollution have revived interest in EVs
and HEVs.

History of Electric Vehicles:

Early Development (1820s – 1900s)

• 1828: Hungarian engineer Ányos Jedlik built one of the first electric motors and used it to
power a small model car.
• 1832–1839: Scottish inventor Robert Anderson developed the first crude electric carriage.
 • 1859: Gaston Planté invented the lead-acid battery, making rechargeable electric cars
possible.
• 1881: Camille Alphonse Faure improved battery technology, leading to the first practical
electric vehicles.
• 1884: Thomas Parker, an English inventor, built an early production electric car.
• 1890s: Electric taxis were used in London and New York.

The Rise of Electric Vehicles (1900s – 1920s)

• 1900: Electric cars became popular due to their quiet operation, ease of use, and lack of
emissions.
• 1908: The Ford Model T (gasoline-powered) was introduced, significantly reducing car
costs and shifting market dominance to internal combustion engines (ICEs).
• 1912: The invention of the electric starter by Charles Kettering eliminated the need for
hand-cranking gasoline cars, making them more convenient.
• 1920s: Decline of EVs due to better road infrastructure, lower gasoline prices, and mass
production of ICE vehicles.

Dormant Period and Limited Use (1930s – 1970s)

• EVs remained in limited use for niche applications such as forklifts, trolleys, and golf carts.
• Gasoline vehicles became the primary mode of transportation due to their longer range and
lower cost.
• Rising oil consumption led to concerns about fuel availability and environmental impact.

Revival of Electric Vehicles (1970s – 1990s)

• 1973: The oil crisis increased interest in alternative fuels, including electric vehicles.
• 1974: The Citicar, a small EV produced by Sebring-Vanguard, gained popularity.
• 1990s: Automakers began experimenting with EVs due to growing environmental
concerns.
o 1996: General Motors (GM) released the EV1, one of the first mass-produced
electric cars.
 o 1997: Toyota introduced the Prius, the world's first mass-produced hybrid electric
vehicle (HEV).

The Modern Era (2000s – Present)

• 2000s: Improvements in battery technology, especially lithium-ion batteries, led to the

development of practical EVs and HEVs.
• 2008: Tesla launched the Roadster, proving that EVs could be high-performance vehicles.
• 2010: Nissan introduced the Leaf, a fully electric car with a long-range battery.
• 2012: Tesla introduced the Model S, setting new standards for EVs in range, speed, and
technology.
• 2020s: Major automakers such as Tesla, BMW, Ford, and Volkswagen continue
developing EVs with improved battery efficiency and fast-charging capabilities.

History of Hybrid Electric Vehicles (HEVs):

Hybrid Electric Vehicles (HEVs) use both an internal combustion engine (ICE) and an electric
motor to improve fuel efficiency and reduce emissions. The concept of hybrid powertrains has
been around for over a century, but modern HEVs gained popularity in the late 20th and early 21st
centuries due to advancements in battery technology and environmental concerns.

• William H. Patton filed a patent application for a gasoline-electric hybrid rail-car

propulsion system in early 1889, and for a similar hybrid boat propulsion system in mid-
1889.
• In 1896, the Armstrong Phaeton was developed by Harry E. Dey and built by
the Armstrong Company of Bridgeport, CT for the Roger Mechanical Carriage Company.
Though there were steam, electric, and internal combustion vehicles introduced in the early
days, the Armstrong Phaeton was innovative with many firsts.
 • In 1905, Henri Pieper of Germany/Belgium introduced a hybrid vehicle with an electric
motor/generator, batteries, and a small gasoline engine.
• A more recent working prototype of the HEV was built by Victor Wouk (one of the
scientists involved with the Henney Kilowatt, the first transistor-based electric car) and Dr.
Charles L Rosen. Wouk's work with HEVs in the 1960s and 1970s earned him the title as
the "Godfather of the Hybrid".[46] They installed a prototype hybrid drivetrain (with a 16-
kilowatt (21 hp) electric motor) into a 1972 Buick Skylark provided by GM for the 1970
Federal Clean Car Incentive Program
• In 1982, Fritz Karl Preikschat invented an electric propulsion and braking system for cars
based on regenerative braking.
• In 1989, Audi produced its first iteration of the Audi Duo (the Audi C3 100 Avant Duo)
experimental vehicle, a plug-in parallel hybrid based on the Audi 100 Avant quattro.
• 1998 saw the Esparante GTR-Q9 became the first Petrol-Electric Hybrid to race at Le
Mans, although the car failed to qualify for the main event. The car managed to finished
second in class at Petit Le Mans the same year.
• The Audi Duo III was introduced in 1997, based on the Audi B5 A4 Avant, and was the
only Duo to ever make it into series production
• The Honda Civic Hybrid was introduced in February 2002 as a 2003 model, based on
the seventh-generation Civic.[
• In 2006, General Motors Saturn Division began to market a mild parallel hybrid, the
2007 Saturn Vue Green Line, which utilized GM's Belted Alternator/Starter (BAS Hybrid)
system
• The Range Rover Hybrid diesel-powered electric hybrid was unveiled at the 2013
Frankfurt Motor Show, and retail deliveries in Europe are slated to start in early 2014.

Future of Electric and Hybrid Vehicles

• Advancements in Battery Technology: Solid-state batteries and ultra-fast charging.

• Government Policies: Many countries are setting targets to phase out gasoline and diesel
vehicles.
 • Autonomous & AI-Integrated Vehicles: EVs and HEVs are increasingly incorporating
AI for autonomous driving.
• Sustainability Initiatives: EVs play a crucial role in reducing carbon emissions and
reliance on fossil fuels.

Vehicle Fundamentals-

General Description of Vehicle Movement:

1. Introduction

A vehicle moves when the force generated by its powertrain (engine/motor) overcomes resistive
forces like aerodynamic drag, rolling resistance, and road gradient. The movement depends on the
interaction between tractive effort, powertrain efficiency, and vehicle dynamics.

2. Forces Acting on a Moving Vehicle

A moving vehicle experiences several forces:

• Tractive Effort (Ft): The force exerted by the powertrain on the road to move the
vehicle forward.
• Aerodynamic Drag (Fd): The resistance due to air, proportional to the square of
velocity.
• Rolling Resistance (Fr): The friction between tires and the road, mainly due to
deformation of the tires.
• Gravitational Force (Fg): The force acting due to the vehicle's weight when moving
on an incline.

The total resistive force (F_res) opposing motion is:

Fres=Fd+Fr+Fg

For a vehicle to accelerate:

Ft>Fres

For constant speed:

Ft=Fres

For deceleration:

Ft<Fres

List of General description of vehicle movement

Vehicle movement refers to the physical displacement or motion of automobiles, trucks,

motorcycles, or any other type of motorized transportation. It encompasses various aspects such
as acceleration, deceleration, steering, and navigation through different terrains and environments.

1. Acceleration and Deceleration

Vehicles accelerate to increase their speed and decelerate to decrease it. Acceleration involves the
vehicle’s engine generating power to propel it forward, while deceleration typically involves
reducing engine power or applying brakes to slow down.

2. Steering

Steering allows the driver to control the direction of the vehicle. This can be achieved through
various mechanisms such as a steering wheel, handlebars, or joystick, depending on the type of
vehicle.
3. Turning

Vehicles can turn left or right by adjusting the steering angle. This involves a combination of
steering input and differential wheel speeds to navigate curves and corners.

4. Braking

Braking is essential for slowing down or stopping a vehicle. Different braking systems, such as
hydraulic brakes or regenerative braking (common in electric vehicles), are used to reduce speed
safely.

5. Transmission

Vehicles may have manual or automatic transmissions that control the distribution of power from
the engine to the wheels. Shifting gears allows the vehicle to operate efficiently across different
speeds and terrains.

6. Terrain Adaptation

Vehicles must adapt to various terrains such as roads, highways, off-road trails, snow, mud, and
water. This often requires different driving techniques and specialized features such as all-wheel
drive, four-wheel drive, or off-road suspension systems.

7. Obstacle Avoidance

Drivers must navigate around obstacles such as other vehicles, pedestrians, animals, debris, and
road hazards. This requires vigilance, quick decision-making, and sometimes evasive maneuvers.

8. Navigation

Modern vehicles may utilize GPS navigation systems to assist drivers in finding routes, providing
real-time traffic information, and offering turn-by-turn directions.
Power Train Tractive Effort:

Tractive Effort (F_t) Definition

The tractive effort of an electric vehicle's (EV) powertrain refers to the force the electric motor
generates to move the vehicle forward. It is a key factor in determining the vehicle's performance,
especially in terms of acceleration and towing capacity. It is given by

F=P/v

Where:

• F is the tractive effort (force) in Newtons (N),

• P is the power output of the motor in watts (W),
• v is the vehicle speed in meters per second (m/s).

Alternatively, the tractive effort can also be expressed in terms of the motor's torque:

• F=T/r

Where:

• T is the torque produced by the motor (Nm),

• r is the radius of the driving wheels (meters).

For EVs, the tractive effort depends on several factors, including:

• Motor torque and power: The more torque the motor generates, the higher the tractive
effort.
• Transmission ratio: In vehicles with a multi-speed transmission, gear ratios can influence
the tractive effort.
• Vehicle weight: A heavier vehicle requires more tractive effort to move.
• Wheel size: Larger wheels may require more force to overcome inertia and friction.
Electric Vehicle Speed

The speed of an electric vehicle (EV) depends on several factors, including the power output of
the motor, the gearing system (if any), the vehicle's weight, and the conditions under which it is
driven. Here's a general breakdown of how EV speed is determined:

1. Motor Power and Torque

• Power Output: The power produced by the electric motor (measured in kilowatts, kW)
plays a crucial role in determining the maximum speed. A higher power output generally
allows for higher speeds, though this also depends on the motor design and its efficiency
at different speeds.
• Torque: EVs provide instant torque, which allows for quick acceleration, but as the vehicle
speed increases, the torque will typically decrease or stabilize, depending on the motor
design and controller system.

2. Vehicle Gear Ratios (or Direct Drive)

• Most EVs use a single-speed transmission or a direct drive system, which is different from
the multi-gear systems found in traditional internal combustion engine vehicles.
• In a single-speed system, the gearing is optimized to provide a balance between
acceleration and maximum speed. The gear ratio determines how the motor's rotational
speed is translated into wheel speed.
• The vehicle speed is a function of the motor's rotational speed and the wheel size. In some
high-performance EVs, multi-speed transmissions might be used for greater control over
the motor's RPM range.

3. Battery Voltage and Capacity

• The higher the voltage of the battery, the greater the current it can supply to the motor,
which in turn allows for higher speeds. However, the capacity (how much energy the
battery can store) influences range, not speed, though a larger battery might allow for
sustained high-speed driving.
4. Aerodynamics and Vehicle Design

• EVs, like all vehicles, face aerodynamic resistance at higher speeds. A vehicle’s design,
including the shape of the body, can impact how much energy is required to maintain a
particular speed.
• For example, electric cars like the Tesla Model S or Lucid Air are designed to be highly
aerodynamic to reduce drag and improve energy efficiency, which helps them achieve
higher speeds with lower energy consumption.

5. Vehicle Weight and Friction

• Heavier vehicles require more energy to overcome inertia, which can reduce acceleration
and top speed. However, the weight distribution in EVs is usually optimized for better
handling and performance (e.g., battery placement in the floor of the vehicle).
• Tire friction, road conditions, and environmental factors like wind also influence the
vehicle's top speed and efficiency.

Basic Formula for speed

 Vehicle performance:

Electric Vehicles (EVs) are evaluated based on several key performance parameters, including
maximum speed, gradeability, and acceleration performance. These factors depend on motor
power, torque, battery capacity, aerodynamics, and vehicle weight.

Maximum speed of a vehicle: The maximum speed of an EV is the highest velocity it can reach
under optimal conditions.

Factors Affecting Maximum Speed:

• Motor Power Output: Higher power enables higher top speeds.

• Aerodynamics & Drag Coefficient: Streamlined designs reduce air resistance.
• Electronic Speed Limiters: Manufacturers often impose speed caps for safety.
• Tire Size & Rolling Resistance: Wider and lower-resistance tires improve efficiency.

Gradeability (Hill Climbing Ability)

Gradeability is the maximum incline (%) an EV can climb while maintaining adequate speed and
performance.

Factors Affecting Gradeability:

• Torque-to-Weight Ratio: Higher torque helps in climbing steeper inclines.

• Tire Grip & Traction Control: Good traction prevents slipping on steep roads.
• Weight Distribution & AWD System: Better weight balance improves stability.

Acceleration Performance (0–100 km/h)

Definition:

Acceleration measures how quickly an EV reaches 100 km/h from a standstill.

Factors Affecting Acceleration:

• Instant Torque Output: EVs deliver power immediately, unlike IC engines.

• Weight & Battery Placement: Lower weight and better weight distribution improve
acceleration.
• Motor Control & Traction: Advanced software optimizes power delivery

Braking in EVs

Braking in electric vehicles (EVs) differs from conventional internal combustion engine (ICE)
vehicles due to the use of regenerative braking in addition to traditional friction braking. Efficient
braking improves safety, extends battery life, and enhances energy efficiency.

Types of Braking in EVs

EVs primarily use two braking systems:

i) Regenerative Braking

• Working Principle: Converts kinetic energy into electrical energy and stores it in the
battery.
• Process: When the driver lifts off the accelerator or presses the brake, the electric motor
reverses its operation, acting as a generator.

ii) Friction Braking (Conventional Brakes)

• Working Principle: Uses traditional disc or drum brakes to slow down the vehicle through
friction
Factors Affecting Braking Performance in EVs

Several factors influence the braking efficiency of EVs:

i) Vehicle Weight

• EVs are heavier due to battery packs.

• Increased weight results in a longer stopping distance compared to ICE vehicles.

ii) Tire Grip and Road Conditions

• Tire quality, road surface, and weather conditions (rain, snow) impact braking efficiency.

iii) Battery State of Charge (SOC)

• When the battery is fully charged, regenerative braking effectiveness decreases.

• More reliance on friction brakes in this scenario.

iv) Braking System Design

• Anti-lock Braking System (ABS): Prevents wheel lock-up and maintains control.
• Electronic Stability Control (ESC): Enhances stability during braking.
• Brake-by-Wire Systems: Uses electronic signals instead of mechanical linkages for
improved response.

The total braking force required to decelerate a vehicle is given by Newton’s second law:

Fb=ma

where:

Fb=Total braking force (N)

m = Mass of the vehicle (kg)

The stopping distance (d) depends on the initial speed (v) and deceleration (a):
 𝑉2
𝑑=
2𝑎

where:

d = Stopping distance (m)

v = Initial velocity (m/s)

a = Deceleration (m/s²)

In regenerative braking, the force generated by the electric motor can be expressed as:

𝑷𝒓𝒆𝒈𝒆𝒏
Freg=
𝒗

where:

Freg= Regenerative braking force (N)

Pregen = Regenerative power (W)

v = Vehicle speed (m/s)

Maximum Braking Force:

The maximum braking force that can be applied before wheel slip occurs is limited by the friction
between tires and the road:

Fbmax = μ m g

where:

• Fbmax = Maximum braking force (N)

• μ = Coefficient of friction between tire and road
• g = Gravitational acceleration (9.81 m/s²)
• If Fb>Fbmax , the wheels may lock up (unless ABS is used).
Braking Force Distribution on Front and Rear Axles in EVs

Electric Vehicles (EVs) use a combination of regenerative braking and friction braking to
decelerate. The braking force distribution between the front and rear axles is crucial for stability,
efficiency, and safety.

The total braking force

𝐹𝑏 = 𝐹𝑟𝑒𝑔 + 𝐹𝑓𝑟𝑖𝑐

It is distributed between the front and rear axles to maintain control and maximize energy recovery.

During braking, the vehicle's weight shifts forward, increasing the normal force on the front wheels
and reducing it on the rear wheels. This requires more braking force at the front axle.

The front and rear braking forces are given by:

ℎ𝑚𝑔 𝐹𝑏
𝐹𝑏𝑓𝑟𝑜𝑛𝑡 = +
𝐿 2

𝐹𝑏 ℎ𝑚𝑔
𝐹𝑏𝑟𝑒𝑎𝑟 = −
2 𝐿

where:

𝐹𝑏𝑓𝑟𝑜𝑛𝑡 , 𝐹𝑏𝑟𝑒𝑎𝑟 = = Braking forces on the front and rear wheels (N)

h= Center of gravity height (m)

m= Vehicle mass (kg)

g= Acceleration due to gravity (9.81 m/s²)

l= Wheelbase (m)

Fb= Total braking force (N)

Practical Braking Distribution in EVs

Typical EV braking force distribution:

• Front axle: 60-80% of total braking force.

• Rear axle: 20-40% of total braking force.

1.Example Calculation:

An EV has a mass of 1500 kg, center of gravity of 0.55 m and its wheel base=2.8m. Vehicle
deacceleration speed is 5 m/s². Calculate braking force on front and rear wheel.

Solution:

Given:

• Vehicle mass = 1500 kg

• Center of gravity height = 0.55 m
• Wheelbase = 2.8 m
• Deceleration = 5 m/s²

Step 1: Compute Total Braking Force

𝑭𝒃 = 𝑚𝑎=1500*5=7500N

Step 2: Compute Front and Rear Braking Forces

ℎ𝑚𝑔 𝐹𝑏
𝐹𝑏𝑓𝑟𝑜𝑛𝑡 = +
𝐿 2

0.55∗1500∗9.81 7500
= +
2.8 2
𝑭𝒃𝒇𝒓𝒐𝒏𝒕 =6640N

𝐹𝑏 ℎ𝑚𝑔
𝐹𝑏𝑟𝑒𝑎𝑟 = −
2 𝐿

7500 0.55∗1500∗9.81
= −
2 2.8

𝑭𝒃𝒓𝒆𝒂𝒓 = 𝟖𝟔𝟎 𝑵

Final Braking Distribution:

• Front axle braking force: 6640 N (88.5%)

• Rear axle braking force: 860 N (11.5%)