Final Project: Design of an Electric Vehicle

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

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

• V_ref is the reference voltage across the ref+ and ref- ports.

• V_min is the minimum reference voltage.

• V_max is the maximum reference voltage.

• Asynchronous – Best for variable-step solvers — Asynchronous events are better suited to variable step solvers, because they require fewer simulation steps for the same level of accuracy. In asynchronous mode the PWM switching events generate zero crossings, and therefore switching times are always determined accurately, regardless of the simulation maximum step size.

• Discrete—time – Best for fixed-step solvers — Discrete-time events are better suited to fixed-step operation, because then the switching events are always synchronized with the simulation step. Using an asynchronous implementation with fixed-step solvers may sometimes result in events being up to one simulation step late. For more information, see Simulating with Fixed Time Step — Local and Global Fixed-Step Solvers.

• The sample time must be a multiple of the simulation step size.

• The sample time must be small compared to the PWM period, to ensure sufficient resolution.

Current Sensor:

The Current Sensor block represents an ideal current sensor, that is, a device that converts current measured in any electrical branch into a physical signal proportional to the current.

Connections + and – are electrical conserving ports through which the sensor is inserted into the circuit. Connection I is a physical signal port that outputs the measurement result.

Controlled Current Source :

The block represents an ideal current source that is powerful enough to maintain the specified current through it regardless of the voltage across it. The output current is I = Is, where Is is the numerical value presented at the physical signal 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 output voltage is V = Vs, where Vs is the numerical value presented at the physical signal port.

Multiport Switch :

Choose between multiple block inputs

Library

Simulink Signal Routing and Fixed-Point Blockset Select

The Multi-Port Switch block chooses between a number of inputs. The first (top) input is called the control input, while the rest of the inputs are called data inputs. The value of the control input determines which data input is passed through to the output port.

If the control input is an integer value, then the specified data input is passed through to the output. For example, suppose the Use zero-based indexing parameter is not selected. If the control input is 1, then the first data input is passed through to the output. If the control input is 2, then the second data input is passed through to the output, and so on. If the control input is not an integer value, the block first truncates the value to an integer by rounding to floor. If the truncated control input is less than 1 or greater than the number of input ports, an out-of-bounds error is returned.

You specify the number of data inputs with the Number of input ports parameter. The data inputs can be scalar or vector. The block output is determined by these rules:

• If you specify only one data input and that input is a vector, the block behaves as an "index selector," and not as a multi-port switch. The block output is the vector element that corresponds to the value of the control input.
• If you specify more than one data input, the block behaves like a multi-port switch. The block output is the data input that corresponds to the value of the control input. If at least one of the data inputs is a vector, the block output is a vector. Any scalar inputs are expanded to vectors.
• If the inputs are scalar, the output is a scalar.

When the Show additional parameters check box is selected, some of the parameters that become visible are common to many blocks. For a detailed description of these parameters, refer to Block Parameters in the Fixed-Point Blockset documentation.

Driving cycle Sources :

A driving cycle is a series of data points representing the speed of a vehicle versus time.

Driving cycles are produced by different countries and organizations to assess the performance of vehicles in various ways, as for instance fuel consumption, electric vehicle autonomy and polluting emissions.

Fuel consumption and emission tests are performed on chassis  dynamometers. Tailpipe emissions are collected and measured to indicate the performance of the vehicle.

Another use for driving cycles is in vehicle simulations. More specifically, they are used in propulsion system simulations to predict performance of internal combustion engines, transmissions, electric drive systems, batteries, fuel cell systems, and similar components.

Some driving cycles are derived theoretically, as it is preferred in the European Union, whereas others are direct measurements of a driving pattern deemed representative.

There are two types of driving cycles:

1. Transient driving cycles involve many changes, representing the constant speed changes typical of on-road driving.
2. Modal driving cycles involve protracted periods at constant speeds.

The American FTP-75, and the unofficial European Hyzem driving cycles are transient, whereas the Japanese 10-15 Mode and JC08 cycles are modal cycles.
Some highly stylized modal driving cycles such as obsolete European NEDC were designed to fit a particular requirement but bear little relation to real world driving patterns.On the contrary, the current WLTP is striving to mimic real word driving behavior. The most common driving cycles are probably the WLTC, NEDC, SORDS and the FTP-75, the later corresponding to urban driving conditions solely.

DC-DC Converter :

DC-to-DC converters are devices that temporarily store electrical energy for the purpose of converting direct current (DC) from one voltage level to another. In automotive applications, they are an essential intermediary between systems of different voltage levels throughout the vehicle.

The DC-to-DC converters convert one level of DC voltage to another level. The operating voltage of different electronic devices such as ICs, MOSFET can vary over a wide range, making it necessary to provide a voltage for each device. A Buck Converter outputs a lower voltage than the original voltage, while a Boost Converter supplies a higher voltage.

With the application of DC-to-DC Converters, the circuit’s efficiency, ripple, and load-transient response can be changed. Optimal external parts and components are generally dependent on operating conditions such as input and output specifications. So, while designing the products, the standard circuits must be varied or changed according to and as per the need to their individual specification requirements. Designing the circuit that satisfies the specification and all the requirements needs a great deal of expertise and experience in that field.

LONGITUDINAL DRIVER:

 

This longitudinal driver block uses a longitudinal speed – tracking controller. Based on feedback velocities and reference normalized acceleration and braking commands are generated which can vary from 0 through 1. This block is used to model the dynamic response of a driver.

A parametric longitudinal speed tracking controller for generating normalized acceleration and braking commands based on reference and feedback velocities.

Use the external actions to input signals that can disable, hold, or override the closed-loop commands determined by the block. The block uses this priority for the input commands: disable, hold, override.

• SIMULINK PS CONVERTER

 

The Simulink PS converter block converts the input Simulink signal into a physical signal. This block connects Simulink blocks to the inputs of a physical network diagram.

• DISPLAY

 

In this block the display outputs the value after the simulation is run

SIMULINK MODEL OF THE ELECTRIC VEHICLE :

 

Many advanced technologies are changing our lives every day. The advent and growth of the Electric Vehicle (EV) is a major example of just how much those changes can mean for our business life — and for our personal lives.

Technological advances and environmental regulatory pressures on internal combustion engine (ICE) vehicles are driving the expanding interest in the EV market. Many established automobile manufacturers are introducing new EV models, alongside new start-ups entering the market. With the selection of makes and models available today, and many more to come, the possibility that we all may be driving EVs in the future is closer to reality than ever.

The technology that powers the EVs of today demands many changes from the way traditional vehicles have been manufactured. The process to build EVs requires nearly as much design consideration as the aesthetics of the vehicle itself. That includes a stationary line of robots specifically designed for EV applications — as well as flexible production lines with mobile robots that can be moved in and out at various points of the line as needed.

In this issue we will examine what changes are needed to efficiently design and manufacture EVs today. We will talk about how processes and production procedures differ from those used to manufacture gas-powered vehicles.

Design, components and manufacturing processes

Although the development of the EV was vigorously pursued by researchers and manufacturers in the early twentieth century, interest was stalled due to cheaper cost, mass-produced gasoline-powered vehicles. Research waned from 1920 until the early 1960s when environmental issues of pollution and the fear of depleting natural resources created the need for a more environmentally friendly method of personal transportation.

EV design

Today’s EVs are very different from ICE (internal combustion engine) gasoline-powered vehicles. The new breed of EVs has benefited from a series of failed attempts to design and build electric vehicles using traditional methods of production used by manufacturers for decades.

There are numerous differences in how EVs are manufactured when compared to ICE vehicles. The focus used to be on protecting the engine, but this focus has now shifted to protecting the batteries in manufacturing an EV. Automotive designers and engineers are completely rethinking the design of EVs, as well as creating new production and assembly methods to build them. They are now designing an EV from the ground up with heavy consideration to aerodynamics, weight and other energy efficiencies.

• The single biggest modification of the car is the underbody. While this structure has been very similar in the past, with EVs there is no engine and there are no exhaust systems needed. There is an aerodynamically designed full belly pan under the EV that contains trays where the battery pack is placed. With more and more variations and shapes of battery packs available for different models, the challenge is to be able to make these variations on one Flexible Manufacturing System (FMS). Since all EV battery cells are quite heavy, flexible robotic lines are necessary.
• In addition, FMS production lines must accommodate many new robotically performed joining methods. In many instances spot welding is being replaced by an increased use of self-piercing rivets, gluing, sealing, flow drilling, and laser welding — and are specifically chosen depending on the tray used for each particular type of battery cell.
• The EV’s inner structure is called a “space frame” and is made of strong, lightweight aluminum — and for additional weight-savings, the wheels are also made of aluminum instead of steel. Using manufacturers molds, these aluminum parts are poured at a foundry. In addition, the steering wheel and seat frames are made of magnesium, a strong, lightweight metal. Even the body panels are made of lightweight aluminum, or an impact-resistant composite plastic. Both materials are recyclable, providing long-term disposal advantages.
• In an effort to reduce weight, the structural frame, seat frames, wheels and body are designed for high-strength, safety — and the lightest possible weight. New configurations have been developed that provide support for the components and protection of the vehicle occupants with minimal mass and use of high-tech materials, including aluminum, magnesium and advanced composite plastics.
• The windshield is solar glass that keeps the interior from overheating in the sun and frost from forming in winter. Materials that provide thermal conservation reduce the energy drain that heating and air conditioning impose on the batteries.
• Some features did have to be eliminated or changed while leaving all the comforts drivers find desirable and adding new considerations as well. One feature that was removed because of space restrictions was the spare tire. This was possible because the EV tires contain a sealant to repair any leaks automatically. In addition, the tires are rubber and designed to inflate to higher pressures, so the car rolls with less resistance to conserve energy.
• An added safety consideration was a pedestrian warning system, because EVs run so quietly that pedestrians may not hear them approach. Driver activated flashing lights and beeps warn pedestrians that the car is approaching. This system works automatically when the car is put in reverse as well.

EV battery

An electric vehicle battery (EVB) is the standard designation for batteries used to power electric motors of all types of EVs. In most cases, these are rechargeable lithium-ion batteries that are specifically designed for a high ampere-hour (or kilowatthour) capacity. Rechargeable batteries of lithiumion technology are plastic housings that contain metal anodes and cathodes. Lithium-ion batteries use polymer electrolyte instead of a liquid electrolyte. High conductivity semisolid (gel) polymers form this electrolyte.

Lithium-ion EV batteries are deep-cycle batteries designed to give power over sustained periods of time. Smaller and lighter, the lithium-ion batteries are desirable because they reduce the weight of the vehicle and therefore improve its performance.

These batteries provide higher specific energy than other lithium battery types. They are typically used in applications where weight is a critical feature, such as mobile devices, radio-controlled aircraft and, now, EVs. A typical lithium-ion battery can store 150 watt-hours of electricity in a battery weighing approximately 1 kilogram.

In the last two decades advances in lithium-ion battery technology has been driven by demands from portable electronics, laptop computers, mobile phones, power tools and more. The EV industry has reaped the benefits of these advances both in performance and energy density. Unlike other battery chemistries, lithium-ion batteries can be discharged and recharged daily and at any level of charge.

There are technologies that support the creation of other types of lighter weight, reliable, cost effective batteries — and research continues to reduce the number of batteries needed for today’s EVs. Batteries that store energy and power the electric motors have evolved into a technology of their own and are changing almost every day.

Traction system

EVs have electric motors, also referred to as the traction or propulsion system — and have metal and plastic parts that never need lubrication. The system converts electrical energy from the battery and transmits it to the drive train.

EVs can be designed with two-wheel or all-wheel propulsion, using either two or four electric motors respectively. Both direct current (DC) and alternating current (AC) motors are being used in these traction or propulsion systems for EVs. AC motors are currently more popular, because they do not use brushes and require less maintenance.

EV controller

EV motors also include a sophisticated electronics controller. This controller houses the electronics package that operates between the batteries and the electric motor to control the vehicle speed and acceleration, much like a carburetor does in a gasoline-powered vehicle. These on-board computer systems not only start the car, but also operates doors, windows, air conditioning, tire-pressure monitoring system, entertainment system, and many other features common to all cars.

The controller regulates energy flow from the battery to the motors and allows for adjustable speed. Specially designed Silicon-Controlled Rectifiers (SCRs) are used for this controller. They allow full power to go from the battery to the motor but in pulses, so the battery is not overworked, and the motors are not underpowered.

The controller transforms the battery’s direct current (DC) into alternating current (AC) and regulates the energy flow from the battery. The controller will also reverse the motor rotation — putting the vehicle in reverse — and converting the motor to generators, so that the kinetic energy of motion can be used to recharge the battery when the brake is applied.

EV brakes

Any type of brake can be used on EVs, but regenerative braking systems are preferred in electric vehicles. Regenerative braking is a process by which the motor is used as a generator to recharge the batteries when the vehicle is slowing down. These braking systems recapture some of the energy lost during braking and channel it back to the battery system.

During regenerative braking, some of the kinetic energy normally absorbed by the brakes and turned into heat is converted to electricity by the controller — and is used to re-charge the batteries. Regenerative braking not only increases the range of an electric vehicle by 5 to 10%, but it also has proven to decrease brake wear and reduce maintenance cost.

EV chargers

Two types of chargers are needed. A full-size charger for installation in a garage is needed to recharge EVs overnight, as well as a portable recharger. Portable chargers are quickly becoming standard equipment from many manufacturers. These chargers are kept in the trunk so the EVs’ batteries can be partially or completely recharged during a long trip or in an emergency like a power outage. In a future issue we will further detail the types of EV charging stations such as Level 1, Level 2 and Wireless.

Manufacturing process

Automotive engineers, as well as manufacturing professionals, have given the EV manufacturing process as much design consideration as the overall design of the vehicle itself. To illustrate how EV manufacturing can be successfully accomplished we’ve taken a brief look at how Tesla builds its EVs using many high-tech robotic approaches.

Tesla’s goal to sell 20 million vehicles by 2030 will undoubtedly be realized. With EV sales projected to hit 300 million by 2030, Tesla and other manufacturers will be working at a break-neck pace to meet consumer demand.

First US electric-only automotive manufacturer

Tesla, the first truly new US automotive manufacturer in 90 years, is the biggest electric-only car company — delivering over 936,000 vehicles globally in 2021 alone with a market cap of $948 billion. Tesla is one of the best examples of the philosophies and technologies being employed in the everwidening electric car manufacturing world.

In 2010, Tesla acquired New United Motor Manufacturing Inc (NUMMI), a former GM and Toyota manufacturing plant in Freemont, CA. The ceilings and columns where painted white and skylights were added to brighten and bring natural light into the plant. The psychology of this makeover is that if you want quality, you need people to feel at ease and to feel like they work in a quality place.

By June 2012, the first Model S rolled off the line. In some ways Tesla’s Freemont plant harkens back to the Ford River Rouge plant, which in 1927 had the distinction of “ore to assembly” of the Model A. While other manufacturers may use a network of suppliers to produce many of their sub-assemblies and components, Tesla does much of its manufacturing in house. (They like to keep “Everything Under Control” too.)

Body assembly

The body assembly process begins with coils of aluminum of different gauges, which are uncoiled into a blanking machine that flattens the metal into blanks. The blanks are then fed into an enormous stamping press. At this stage, large custom-made dies form the body panels, which are then transported to the body center.

This is where the EV begins to be assembled — starting with the underbody, which is the main floor system of the EV where the batteries are seated. The body sides are then added to provide internal reinforcement as well as the outer skin. Inside the framing is where the body sides, the underbody and the front end of the vehicle are all married together.

One of the most unique things about the body center is that there are five different overall joining methods for the body shell, including adhesive, self-piercing rivets and cold metal transfer, as well as conventional resistance welding and a delta spot welding system. When the body leaves the body center it is a fully completed body shell — ready to be prepped and painted.

Paint shop

A Kuka robot places the body onto a conveyor that transports it to the paint shop where multiple pretreatment primer base coats are applied. Specially designed paint robots work in an extremely clean environment to produce a beautifully painted body, ready for general assembly. At this point, each EV moves through the factory autonomously powered by its propulsion system and batteries. Since the EV has no internal combustion engine there is no potential danger of exhaust fumes as it travels to the general assembly area.

General assembly

The Tesla EV is assembled from inside out. Automation is used to the fullest — as the same robot that installs the seats, then changes tools to position the windshield, apply adhesive and seat it on the vehicle. In total, about 1,000 robots perform very diverse tasks in the production of the Model 3. Since robots are extremely good at repeatability and accuracy of motion needed, employees are utilized in more flexible situations where human intelligence is required.

EV manufacturing is unique in that many of the components are completely different than for traditional ICE powered vehicles, including the drive units, battery pack, and battery modules. Many of those components did not previously exist, which required Tesla to build them. However, there are also thousands of fewer components in an EV, so it only takes about two days for a Tesla Model 3 to go from raw material to a completed vehicle.

Quality control

Every part used in the operation of the EV has been tested during the many assembly steps at the production line. After the battery pack and propulsion unit have been installed, the car can be driven inside the plant. This shows that the EV is working several steps before it is completed. Due to the individual quality checks at each stage of assembly, the only major quality control requirements are a comprehensive set of tests and inspections.

 

PORT	DESCRIPTION	VALUE/CONNECTION
Headwind speed (W) (m/s) - INPUT	Physical signal input port for headwind speed.	1.38889 m/s value is fed using a constant block and a Simulink-PS connector.
Road incline angle (beta) (radians) - INPUT	Physical signal input port for road incline angle.	0.0698132 rad value is fed using a constant block and a Simulink-PS connector.
Centre of gravity (CG) (m) - INPUT	Physical signal input port for the center of gravity, in m, of the externally-defined mass relative to the CG of the vehicle body.	0.5 m
Mass (M) (kg) - INPUT	Physical signal input port for the mass, in kg, of the externally-defined mass.	600 kg
External moment of Inertia (J) (kg m2) - INPUT	Physical signal input port for the moment of inertia, in kg m2, of the externally-defined mass.	Not employed in this model.
Longitudinal velocity (V) (m/s) - OUTPUT	Physical signal output port for vehicle longitudinal velocity.	Output is collected by the Goto block
Front Axle Normal Force (NF) (N) – OUTPUT	Physical signal output port for normal force on the front axle. Wheel forces are considered positive if acting downwards.	Connected to the N ports of the front tires.
Rear Axle Normal Force (NR) (N) - OUTPUT	Physical signal output port for normal force on the rear axle. Wheel forces are considered positive if acting downwards.	Connected to the N ports of the rear tires.
Horizontal motion (H) - CONSERVING	Conserving port associated with the horizontal motion of the vehicle body. Connect tire traction motion to this port.	Connected to the H ports of the tires and to the Ideal translational motion sensor.

 Ports of vehicle body block in SIMULINK.

• The other values of the input for the vehicle body block are as follows:

Parameter	Value
Number of wheel per axle	2
Horizontal distance from CG to front axle	1.4 m
Horizontal distance from CG to rear axle	1.6 m
Externally defined additional mass	…
Gravitational acceleration	9.81 m/s2
Frontal area	2 m2
Drag coefficient	0.19
Air density	1.25 kg/m3
Pitch dynamics	OFF

 parameters of the vehicle body block in SIMULINK.

RESULTS :

The simulations are run for various drive cycles and the results are in the following table

	Case 1	Case 2	Case 3	Case 4
Drive cycle simulation time (s)	FTP75, 2474	US06,600	Artemis motorway 150kmph,1068	World Harmonized vehicle cycle(WHVC),900
Vehicle body wt. (kg), frontal area (m^2), Drag Coefficient, Rolling resistance	800,3,0.4,0.015	800,3,0.4,0.015	800,3,0.4,0.015	800,3,0.4,0.015
Battery Nominal Voltage (V)	300	300	400	200
DC Motor Rated load (kW), Rated Voltage (V)	60,300	75,200	85,350	60,150
H-Bridge Output voltage amplitude	300	200	350	150
Distance (km),Top speed (kmph)	4.97,25.2	3.54,30.8	7.77,32.6	1.52,18.2
SoC at the end of drive cycle (ini. SoC = 100%)	96	94	93	97
Top speed reached? kWh per km	Yes	No	No	Yes

 

Output Graphs :

A. Case - 1

1. Speed Characteristics :

 

2. SOC (%) :

 

B. Case - 2

1. Speed Characteristics :

 

2. SOC (%)

 

C. Case - 3

1. Speed Characteristics :

 

2. SOC (%)

 

D. Case - 4

1. Speed Characteristics :

 

2. SOC (%)

 

Conclusion :

• In the speed trace plot for all the drive cycles which are observed in this study, the feedback speed plot and the reference speed plot overlap each other almost completely but there are regions where both the speeds are different. It is when the vehicle is deceleration.
• The reference speed plot falls sharply but the feedback speed does not. This is due to the inertia of the vehicle body. As the inertia of the vehicle body is higher, it takes a longer duration for it to decelerate. That is why the overlapping is not 100%.
• The battery's state of charge for each drive cycle can be visualized from the SOC plot. As long as the vehicle is accelerating the SOC is decreasing but as soon as the deceleration starts, the SOC plot goes slightly up. This is because the battery is being charged, due to regenerative braking during deceleration.