Final Project: Design of an Electric Vehicle

Project:

Design of an electric vehicle:

Electric vehicle: A vehicle propulsion through the Electric motor is known as Electric vehicle. Electric motor is powered by AC or DC source. Many automakers are working to change the vehicle technologies, the major area is to decrease the pollution and use electrification in the upcoming vehicles. The researchers and automakers are continuously working to reduce CO2 emissions.

New technology like high-capacity lithium type battery will be a major energy source for the propulsion of electric vehicles.

At present, with the new technologies, some manufacturer has launched its products which are Tesla, Chevy Bolt EV and Nissan leaf which are fully electric battery-based car.

The power and performance of electric vehicles is depending upon the two machines i.e. a brushless DC motor (BLDC) or an induction motor. The DC (direct current) is replaced by DC brushless motors and Induction motors. Also, the lead-acid battery is replaced by lithium-ion batteries for EVs. Because the future of both the components induction or brushless DC motors depends upon their demands and uses.

Electric vehicle picture:

The most important components of electric vehicle areas:

1. Auxiliary Battery: In an electric drive vehicle, the auxiliary battery provides electricity to power vehicle accessories.
2. Traction Battery Pack: Traction battery pack is also known as Electric Vehicle Battery (EVB) which is used to store the electricity. Some examples of traction battery energy storage systems are as given:
3. Lithium-Ion
4. Nickel-Metal Hydride
5. Lead-Acid
6. Ultra-Capacitors
7. DC/DC Converter: Basically, DC/DC converter is an electronic device which is used to converts higher-voltage DC power from the traction battery pack to the lower-voltage DC power. The converted power is used to run the vehicle accessories. It is also used to recharge the auxiliary battery.
8. Electric Traction Motor: Another important component is electric traction motor and this device is used to provide motive power to the wheels.
9. Onboard charger: Takes the incoming AC electricity supplied via the charge port and converts it to DC power for charging the traction battery. It monitors battery characteristics such as voltage, current, temperature, and state of charge while charging the pack.
10. Power electronics controller: This unit manages the flow of electrical energy delivered by the traction battery, controlling the speed of the electric traction motor and the torque it produces.
11. Charge port: The charge port allows the vehicle to connect to an external power supply in order to charge the traction battery pack.
12. Thermal system (cooling): This system maintains a proper operating temperature range of the electric motor, power electronics, and other components.

Block diagram of Electric vehicle design:

Same as Block diagram, we are designing electric vehicle in step by step. From the block diagram, Drive cycle gives the reference signal to the Drive controller. Drive controller have the feed back signal from vehicle body. By scaling two input signals, drive controller gives control signal to H-bridge Converter (To accelerate or Brake are depending on control signal from driver controller). H-bridge converter receives the battery voltage and feed it to electric motor. Electric motor drives the vehicle. While in regenerative braking, Vehicle free wheels and rotates the motor shaft. the kinetic energy feed back to battery through H-bridge converter.

Simulink model of a Electric vehicle design:

Important Simulink Block used in Electric Vehicle design are:

1. Drive Cycle Source: 1
2. Constant: 2
3. Longitudinal Drive: 1
4. Controlled Voltage Source: 2
5. Controlled PWM Voltage: 1
6. Solver Configuration: 1
7. Electrical Reference: 1
8. H-Bridge: 1
9. DC Motor: 1
10. Mechanical Rotational Reference: 1
11. Current Sensor: 1
12. Battery:1
13. Controlled current source: 1
14. PS-Simulink Converter: 4
15. Vehicle Body: 1
16. Tire: 4
17. Simple Gear: 1
18. PS Constant: 2
19. Integrator: 1
20. Divide: 1
21. Display: 1
22. Scope: 3
23. Power gui:1

Vehicle body subsystem:

Vehicle body:

The Vehicle Body block represents a two-axle vehicle body in longitudinal motion. The vehicle can have the same or a different number of wheels on each axle.

The block consists of body mass, aerodynamic drag, road incline, and weight distribution between axles due to acceleration and road profile. In optionally we can include pitch and suspension dynamics.

The block has an option to include an externally-defined mass and externally-defined inertia. The mass, inertia, and centre of gravity of the vehicle body can vary over the course of simulation in response to system changes.

Vehicle body parameters:

1. NR: It is a physical signal output which is connected to the rear wheel axel. For this model, it is connected with a normal force of rear tire.
2. NF: It is a physical signal output which is connected to front-wheel axel and for this particular model it is connected with the normal force acting on a front-wheel tire.
3. Beta: Beta is basically a road incline angle. Here we can define a constant value for road angle inclination.
4. H: This port is a horizontal motion of the vehicle body. This connection will be connected with all four Hub of the wheel for finding the thrust generated by the tire.
5. V: This port is the vehicle longitudinal velocity.
6. W: It is a headwind speed. Basically, we will define a particular wind speed by adding constant block.

Vehicle Body Parameters:

Tire modelling:

The Tire (Magic Formula) block models a tire with longitudinal behaviour given by the Magic Formula, an empirical equation based on four fitting coefficients. The block can model tire dynamics under constant or variable pavement conditions.

The Tire (Magic Formula) block models the tire as a rigid wheel-tire combination in contact with the road and subject to slip. When torque is applied to the wheel axle, the tire pushes on the ground (while subject to contact friction) and transfers the resulting reaction as a force back on the wheel. This action pushes the wheel forward or backwards. If you include the optional tire compliance, the tire also flexibly deforms under load.

• N: Normal force acting on the tire and connected with NR of the vehicle body.
• S: Slip between the tire and road and connected with Go to block
• H: Hub and it is used to find the thrust created by the tire and it is connected with H input of vehicle body also including all four Hub of the wheel.
• A: Axel and rear axle are connected with the (Simple Gear) final drive system and the front axle is connected with the left and right wheel.

Tire parameters:

Rolling Resistance settings:

• Rolling resistance: On, Basically, it includes the rolling resistance.
• Resistance model: By using Constant Coefficient we are Neglect rolling resistance.
• Constant coefficient: 0.015 the value should be greater than 0 and it is a coefficient that sets the proportionality between the normal force and the rolling resistance force.
• Velocity threshold: 1e-3 m/s basically this input is a velocity at which the full rolling resistance force is transmitted to the rolling hub.

Velocity threshold: 0.1 m/s as I keep this value as default and this value should be positive because it is wheel hub velocity Vth below which the slip calculation is modified to avoid singular evolution at zero velocity.

Gear:

Simple Gear is a final drive ratio which is a gearbox that constrains the connected driveline axes of the base gear and the follower gear.

B: The output B, base gear is connected with the input of DC motor R. It is a Rotational mechanical conserving port.

F: The output of F, follower gear is connected with the rear axle. It is also a Rotational mechanical conserving port.

• Output shaft rotates: In the same direction as the input shaft, it is depending upon the direction of follower and base gear.

Meshing losses:

• Friction model: From drop-down, we can select Constant efficiency which calculates the Reduce torque transfer by a constant efficiency factor.

Simple Gear Parameters:

SOC%:

Here we will add a battery system to run the vehicle system and vehicle too. So, for that added battery from Simulink library.

SOC (state-of-charge) is the ratio of current charge to-rated battery capacity.

The positive (+) terminal is also connected to the controlled current source of electrical conserving ports.

Battery parameters:

Controlled current source:

The Controlled Current Source block represents an ideal current source that is powerful enough to maintain the specified current through it regardless of the voltage across the source.

In this particular block, the two-port is connected with battery and one electrical conversing port is connected with PS-Simulink converter .

Electrical reference:

The Electrical Reference block represents an electrical ground.

PS-SIMULINK Converter:

The PS-Simulink Converter block converts a physical signal into a Simulink output signal. Use this block to connect outputs of a Physical Network diagram to Simulink scopes or other Simulink blocks.

DC motor:

The DC Motor block represents the electrical and torque characteristics of a DC motor using the following equivalent circuit model:

Here in this system, the positive terminal is connected with the current sensor negative terminal and negative terminal is connected with the negative terminal of H-Bridge.

R is DC motor rotor which connected with mechanical rotational port i.e. simple gear whereas C is DC motor case and it is connected with mechanical rotational reference.

DC motor Parameters:

Here for the particular model, I configure in DC Motor and try to change a basic setting in electrical torque.

No-load Speed: 11000 rpm, this is the speed of the motor when not driving a load.

Rated speed (at load): 10500 rpm, this is the speed of the motor at rated mechanical power level.

Rotor Inertia: It’s a resistance of the rotor to change in motor motion.

Rotor Damping: It should be zero because it is energy dissipated by the motor.

Initial Rotor Speed: This is a starting speed of the motor that at what speed the motor will start.

H-Bridge converter:

H-bridge Parameters:

• Power Supply: The power supply is default mode - Internal.
• Simulation Mode: Here I selected Averaged mode
• Regenerative Braking: Always enabled (suitable for linearization), this option can be used when the controller always sets the REV flag to ensure regenerative braking.
• Load Current Characteristics: Smoothed, it’s a default option and it assumes that the current is practically continuous due to load inductance.

Input Thresholds:

• Enable threshold voltage: 1.5 V, this is the above value of PWM at which H-Bridge start.
• PWM signal amplitude: 5.0 V, this is the amplitude of the signal at the PWM input. Here I used it as the default mode.
• Reverse threshold voltage: 1.5 V, here I changed this value.
• Braking threshold voltage: 2.5 V

Bridge Parameters:

• Output voltage amplitude: 320 V, this parameter will be active only when we select Internal for Power Supply mode and it’s an amplitude of the voltage across the H-Bridge.
• Total bridge on resistance: 0.1 ohms,
• The freewheeling diode on resistance: 0.05 ohm

Detail about connection

• PWM: Pulse-width modulated signal.
• REF: Reference, it is an electrical conversing port associated with the floating zero volts.
• REV: Reverse, it is an electrical conserving port associated with the voltage that controls when to reverse the polarity of the H-Bridge block output.
• BRK: BRK, it is an electrical conserving port associated with the voltage that controls when to short circuit the H-Bridge block output.

Here PWM output port is connected with PWM input port of controlled PWM voltage. The REF and REV port are connected with REF port of controlled PWM voltage port. The BRK port is connected with a controlled voltage source.

The positive (+) terminal is connected with the positive (+) port of current sensor and negative (-) port is connected with the negative (-) port of DC motor.

Controlled PWM Voltage:

The Controlled PWM Voltage block represents a pulse-width modulated (PWM) voltage source.

Controlled PWM voltage Parameters:

1. ref+ — Positive terminal, this port is a positive electrical reference and connected with controlled voltage source positive terminal.
2. ref- — Negative terminal, this port is a negative electrical reference and connected with the negative terminal of the controlled voltage source.
3. PWM — Pulse-width modulated signal, this port is electrical reference port and connected with PWM port of H-Bridge.
4. REF — Floating zero-volt reference, this port is connected with REF and REV of H-Bridge port.

Controlled voltage Source:

The Controlled Voltage Source block represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current flowing through the source.

The block has one physical signal input port and two electrical conserving ports associated with its electrical terminals.

Solver configuration:

Solver configuration is used to begin the simulation and it is needed to solve the Simulink model. Here it is connected with controlled PWM voltage and H-Bridge negative connection by combination with electrical reference ground signal.

Longitudinal driver:

The Longitudinal Driver block implements a longitudinal speed-tracking controller

1. VelRef: Reference vehicle velocity is connected with speed result block. Its unit is m/s.
2. VelFdbk — Longitudinal vehicle velocity is connected with integrator block for continuous-time integration of VelFdbk signal.
3. Grade — Road grade angle is connected with constant block so that we can use our specific value, here the value is 0 which I used.
4. Info — Bus signal, Here I used this signal to terminate the signal block, basically it’s an output port.
5. AccelCmd — Commanded vehicle acceleration is connected with controlled voltage source input signal by combination with PS-Simulink Convertor.
6. DecelCmd — Commanded vehicle deceleration is connected with another controlled voltage source signal by combination with PS-Simulink converter

Longitudinal driver Block parameters:

Drive Cycle Source:

Drive cycle source Parameters:

The connection drive cycle RefSpd is connected with the VelRef of Longitudinal driver and to the Scoop results which generate the vehicle reference speed.

Distance Calculator:

Here the main blocks is an integrator, Divide, time block and for the result we have to use display block that will display the distance.

Detail about connection:

Integrator:

The output port of the vehicle body is connected with the integrator block.

Divide:

The output of the integrator block is connected with divide where it will be divided by time to get the final output.

Time:

The output of time block is connected with the divide block. Here time is taken as 3600 s.

Results:

Speed:

Comments: From the output, yellow line shows the reference drive cycle to the Longitudinal driver (which is FTP75 drive cycle). Blue line is the Vehicle drive cycle(speed). The function of longitudinal driver is to Maintain Vehicle speed to be same as Reference speed. here Both reference speed and vehicle speed go same with some deviation at deceleration.

SOC%:

Comments: SOC (state of charge) is decreases with increases in acceleration. The above output shows SOC % decreases when Vehicle goes to acceleration. At few point of time SOC % increases due to Braking( Re-Generative braking).

Current:

Here Current draws at vehicle acceleration time , it is at positive value . where the vehicle goes to braking, the current flows in opposite direction (like motor to battery), it is in negative Value.

Conclusion:

Design of an electric vehicle is done and shown above and Explained about its results and results are satisfactory. The total distance travel by vehicle is 5.03 m/s or 18.10 kmph depending upon the FTP75 drive cycle and the total time for simulation was 2474 sec. The battery is having 300 V which is a nominal voltage and the battery ampere per hour rating is 100 by which we calculated the SOC (state of charge) of battery. In this design I have used the DC electric motor to drive the vehicle.