2. DYNAMICS OF HYBRID AND ELECTRIC VEHICLES notes in english

2. DYNAMICS OF HYBRID AND ELECTRIC VEHICLES

The dynamics of hybrid and electric vehicles (HEVs and EVs) involve understanding the principles of motion, power sources, and how these vehicles function. Here, we’ll break down each topic in simple terms.

2.1 General Description of Vehicle Movement

The movement of a vehicle involves several forces acting on it, which affect its motion. These forces include the power generated by the engine or electric motor, the resistance from the road, and other factors like aerodynamics. The primary factors that determine how a vehicle moves are:

Power generation: In traditional vehicles, the internal combustion engine (ICE) generates power, while in electric vehicles (EVs) and hybrid vehicles (HEVs), electric motors generate power. This power is used to move the vehicle.
Transmission of power: This power is transmitted through the drivetrain (gears, shafts) to the wheels, which move the vehicle.
Friction and resistance: The movement of the vehicle is opposed by several resistances such as friction between the tires and the road, air drag, and rolling resistance.

2.2 Factors Affecting Vehicle Motion

Various factors affect the motion of a vehicle. Understanding these factors helps in improving vehicle performance, efficiency, and safety.

2.2.1 Vehicle Resistance

Vehicle resistance refers to the total opposition to the motion of the vehicle caused by various forces. These resistances include:

Rolling resistance: Resistance between the tires and the road.
Aerodynamic drag: Resistance due to air resistance when the vehicle moves.
Grading resistance: Resistance when the vehicle moves uphill or downhill.

This resistance must be overcome by the vehicle's engine or motor to maintain speed or accelerate.

2.2.2 Tyre Ground Adhesion

Tyre ground adhesion refers to the friction between the vehicle's tires and the road. It determines the vehicle’s grip on the road and plays a crucial role in safety, handling, and energy efficiency. More grip means better control and acceleration, but it also leads to higher rolling resistance.

The adhesion force is influenced by the tire material, tire pressure, and road surface.

2.2.3 Rolling Resistance

Rolling resistance is the force that resists the motion of a tire as it rolls on a surface. It is caused by the deformation of the tire and the road surface as the vehicle moves.

Factors: Tire type, pressure, and road surface.
Effect: The higher the rolling resistance, the more energy the vehicle needs to overcome it. In EVs and HEVs, reducing rolling resistance can increase energy efficiency and range.

2.2.4 Aerodynamic Drag

Aerodynamic drag refers to the resistance caused by the air as the vehicle moves forward. This force increases with the speed of the vehicle. It depends on the shape and design of the vehicle.

Factors: Vehicle shape, surface area, and speed.
Effect: A more streamlined vehicle has less aerodynamic drag, which results in better fuel or energy efficiency.

2.2.5 Equation of Grading Resistance

Grading resistance occurs when the vehicle is moving uphill or downhill. When driving uphill, the vehicle must overcome the force pulling it backward due to gravity, which adds to the resistance. Conversely, when driving downhill, the vehicle's momentum may make it harder to control speed.

Equation: Grading resistance = $W \times \sin(\theta)$ $W \times sin (θ)$
- Where: $W$ is the weight of the vehicle, and $\theta$ is the slope angle.

This equation helps calculate the extra force required to move the vehicle up an incline or the effect of gravity on the vehicle's motion downhill.

2.2.6 Dynamic Equation

The dynamic equation of a vehicle refers to the relationship between various forces and the motion of the vehicle. It combines all the resistances (aerodynamic drag, rolling resistance, grading resistance) and the power supplied by the engine or motor.

Basic form: $F = ma$ $F = ma$
- Where: $F$ is the total force acting on the vehicle, $m$ is the mass of the vehicle, and $a$ is the acceleration.

This equation helps to analyze how different forces impact the vehicle’s motion, especially when it changes speed or direction.

2.3 Drive Train Configuration

The drivetrain of a vehicle is the system that transmits power from the engine (or motor) to the wheels. There are different configurations for the drivetrain in hybrid and electric vehicles:

Electric vehicle (EV) drivetrain: Simple system where the electric motor is directly connected to the wheels.
Hybrid vehicle (HEV) drivetrain: A combination of an internal combustion engine and an electric motor, working together to move the vehicle.

The drivetrain configuration affects the performance, fuel efficiency, and cost of the vehicle.

2.4 Automobile Power Train

The powertrain of an automobile is the collection of components responsible for generating and transmitting power to the wheels. This includes:

Engine or motor: Provides power to move the vehicle.
Transmission: Adjusts the engine's power to provide different speeds.
Differential: Helps in distributing power to the wheels, especially when turning.
Driveshaft: Transfers power from the engine to the wheels.

In electric and hybrid vehicles, the powertrain is simplified due to fewer moving parts compared to conventional gasoline vehicles.

2.5 Classification of Vehicle Power Plant

The vehicle power plant is responsible for generating power in the vehicle. There are different classifications of power plants used in vehicles:

Internal Combustion Engine (ICE): Traditional power source that uses fuel (like petrol or diesel) to generate power.
Electric Motors: In EVs and HEVs, electric motors powered by batteries or a combination of batteries and gasoline are used to propel the vehicle.
Hybrid Power Plant: Combines both internal combustion engines and electric motors to provide more efficiency, especially in fuel usage and energy recovery.

2.6 Classification of Motors Used in Electric Vehicles

In electric vehicles, various types of motors are used to convert electrical energy into mechanical motion. These include:

DC Motors: Simple and cost-effective, but less efficient for high-performance EVs.
AC Induction Motors: More efficient and commonly used in EVs due to their ability to handle higher speeds and power.
Permanent Magnet Synchronous Motors (PMSM): Use permanent magnets for more efficient performance, especially in high-performance EVs.
Brushless DC Motors (BLDC): Efficient and reliable, used in most modern electric vehicles for better performance and longer lifespan.

2.7 Types of HEVs (Hybrid Electric Vehicles)

Hybrid Electric Vehicles (HEVs) are classified based on how the engine and motor work together. The types include:

Full Hybrid (FHEV): Both the internal combustion engine and the electric motor can independently power the vehicle or work together.
- Example: Toyota Prius.
Mild Hybrid (MHEV): The electric motor assists the internal combustion engine but cannot power the vehicle on its own.
- Example: Honda Insight.
Plug-in Hybrid (PHEV): These can be charged via an external power source and have a larger battery than regular HEVs, allowing them to run on electricity for longer distances.
- Example: Chevrolet Volt.

2.8 HEV Configurations: Series, Parallel, Series-Parallel, Complex

HEVs can be classified based on their drivetrain configuration:

Series Hybrid:
- In this configuration, the internal combustion engine (ICE) does not directly drive the wheels. Instead, the engine generates electricity that is used to power the electric motor, which drives the wheels.
- Example: Chevrolet Volt.
Parallel Hybrid:
- Both the electric motor and the internal combustion engine (ICE) can directly drive the wheels. The engine and motor work together or independently to propel the vehicle.
- Example: Honda Insight.
Series-Parallel Hybrid:
- This configuration combines both series and parallel systems. The vehicle can operate in both modes: the electric motor can drive the wheels, and the engine can either work alone or assist the motor.
- Example: Toyota Prius.
Complex Hybrid:
- A combination of the series-parallel system but with more advanced features. In some cases, it may use multiple electric motors or have more sophisticated power distribution to improve efficiency.
- Example: Lexus LS 600h.

2. DYNAMICS OF HYBRID AND ELECTRIC VEHICLES notes in english