Final Project: Design of an Electric Vehicle

AIM: Create a MATLAB model of an electric car that uses a battery and a DC motor. Choose suitable blocks from the Powertrain block set. Prepare a report about your model including the following:

OBJECTIVE:

1. System-level configurations

2. Model parameters

3. Results

4. Conclusion

ELECTRIC VEHICLE – MODELLING AND SIMULATIONS

The Electric Vehicle was developed with the motor, battery, controller, converters, and wheels.

The motor is connected to the differential of the wheels.

In this basic configuration of EV, four wheels are used. Two wheels are connected in the front portion called front-wheel drive.

The rest of the two wheels are connected at the rear portion of the drive, so it is called real wheel drive.

Both the ends wheels are connected through the differential.

The differential is provided the balancing to the rear and front-wheel drive system.

The differential portion represents a gear mechanism that allows the driven shaft to spin at different speeds.

The fidelity of the gear model improved by specifying the parameters of the differential gear system like gear inertia, meshing, and viscous losses.

1. Modeling of Electrical Vehicle (EV)

We developed a four-wheel drive model of an electric vehicle.

Two wheels place at the front portion and the other two are placed at the rear portion. Both real and front wheels are controlled by an induction motor and synchronous motor with the help of the inverter controller circuit.

The vehicle body is placed on the four wheels of the drive with initial parameters of environments like wind, inclined, and throttle.

Before performing the modeling of the four-wheel electric vehicle drive train, we finalize the parameters and behavior of the vehicle body.

On the front wheel side, we used a synchronous motor with a controller connected to the battery voltage source.

Inverter circuit applied in the controller to provide a sufficient amount of electric supply to the motors.

Vehicle Longitudinal Dynamics For the evaluation of the longitudinal nature of electric vehicles some equations are used.

The Electric vehicle model is based on motion resistance forces like an aerodynamic drag, rolling and climbing resistance, and vehicle velocity.

The rolling resistance ( is that term related to the energy losses due to tire deformation and adhesion of contact area

The blocks comprising the model are explained below:

Simulink blocks	functions
Drive cycle	For input of vehicle driver
Longitudinal driver	For driving acceleration & deceleration command PWM
Pwm voltage controller	To generate controlled PWM voltage
H-bridge	To supply controlled power to motor
DC – motor for	For rotation of wheel vehicle
Vehicle
Battery	Supply for components
Display	To show output value
Scope	To show graph of output

1. Drive Cycle Source - The Drive Cycle Source block generates a standard or user-specified longitudinal drive cycle. The block output is the specified vehicle longitudinal speed. For our model, we have selected two different cycles, FTTP & WOT drive cycle.

Drive cycle plot FTP75:

2. Longitudinal Driver - The Longitudinal Driver block implements a longitudinal speed-tracking controller. Based on reference and feedback velocities, the block generates normalized acceleration and braking commands that can vary from 0 to 1. You can use the block to model the dynamic response of a driver or to generate the commands necessary to track a longitudinal drive cycle.

3. Power Controller – I’ve marked the area, this area consists of many blocks grouped, two controlled voltage sources, controlled PWM Voltage, H-Bridge., and solver configuration.

• Controlled Voltage Source - The Controlled Voltage Source block converts a Simulink^®input signal into an equivalent voltage source. The generated voltage is driven by the input signal of the block.

• Controlled PWM Voltage – The Controlled PWM Voltage block represents a pulse-width modulated (PWM) voltage source. You can model electrical or physical signal input ports by setting the Modeling option parameter to either:

Electrical input ports — The block calculates the duty cycle based on the reference voltage across its ref+ and ref- ports. This option is the default.

PS input — Specify the duty cycle value directly by using an input physical signal port.

• H- Bridge – This block represents an H-bridge motor drive. The block can be driven by the Controlled PWM Voltage block in PWM or Averaged mode. In PWM mode, the motor is powered if the PWM port voltage is above the Enable threshold voltage. In Averaged mode, the PWM port voltage divided by the PWM signal amplitude parameter defines the ratio of the on-time to the PWM period. Using this ratio and assumptions about the load, the block applies an average voltage to the load that achieves the correct average load current. The Simulation mode parameter value must be the same for the Controlled PWM Voltage and H-Bridge blocks.
• 
• Battery Capacity Area: This area is marked to show the SOC Estimate, that is it shows how the battery capacity drains when the motor is operated for the required drive cycle.

Vehicle – it is a substation block, which consists of the vehicle parameters that include the vehicle dimensions, tire dimensions, and gear ratio.

A vehicle body – Represents a two-axle vehicle body in longitudinal motion. The block accounts for body mass, aerodynamic drag, road incline, and weight distribution between axles due to acceleration and road profile. The vehicle can have the same or a different number of wheels on each axle. Optionally include pitch and suspension dynamics or additional variable mass and inertia. The vehicle does not move vertically relative to the ground.

Tire - Represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The block is built from Tire-Road Interaction (Magic Formula) and Simscape Foundation Library Wheel and Axle blocks. Optionally, the effects of tire inertia, stiffness, and damping can be included.

• Gear Ratio – Represents a fixed-ratio gear or gearbox. No inertia or compliance is modeled in this block. You can optionally include gear meshing and viscous bearing losses.

6. DC Motor - This block represents the electrical and torque characteristics of a DC motor. The block assumes that no electromagnetic energy is lost, and hence the back-emf and torque constants have the same numerical value when in SI units. Motor parameters can either be specified directly or derived from the no-load speed and stall torque. If no information is available on armature inductance, this parameter can be set to some small non-zero value.

SOC ESTIMATOR CIRCUIT:

After joining the blocks as shown in the SIMULINK MODEL, we run the model two times, for different drive cycles and see the results.

VEHICLE SPEED:

The reference speed value & feedback value of the drive cycle is plotted.

We have taken drive cycle ftp75, according to that drive cycle reference the velocity command is plotted.

ACCELERATION COMMAND FROM DRIVE CYCLE:

From the acceleration command of the drive cycle, the graph is plotted.

Here throttle input from the longitudinal driver model block is taken.

DC-MOTOR LOAD CURRENT:

Now, as the throttle input is given, the dc motor will give machinal output, concerning the electrical input supply.

To generate some RPM, it will require current according to load.

The same current drawn by the motor graph is plotted.

SOC %:

As we know, the main power source is the battery for the motor.

The battery provides the necessary power required by the motor at every stage of propulsion.

Now according to the usage of the battery, its state of charge is decreased.

That decrease in SOC is plotted.

DISTANCE TRAVELLED:

5.188 km

Using the basic formula of distance and velocity, we integrated velocity and obtained the total distance traveled in 2474 seconds.

Conclusion:

The proposed EV wheel drive system which is having individual front and rear control improves the EV performance such as torque and speed stability, steering ability, drivability, and safety at low-speed and high-speed operations.

Also, the wheel drive systems were founded in such a way that above stated EV performance requirements were attained more efficiently.

The drive systems are also successfully synchronized in such a way that, if in some adverse conditions torque generated from the front wheel drive is found insufficient to drive the EV at desired speeds at the same time rear wheel drive system provides adequate torque to the EV.