Software Requirements Specification (SRS)cse435/Projects/F2014/Groups/CACC/web/... · The purpose...

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Template based on IEEE Std 830-1998 for SRS. Modifications (content and ordering of information) have

been made by Betty H.C. Cheng, Michigan State University (chengb at chengb.cse.msu.edu)

Software Requirements Specification (SRS)

Cooperative Adaptive Cruise Control System

Authors: Andy Lieblich, Elizabeth Florian, Marco Botros, Zachary Ray

Customer: William Milam, Ford Motor Company

Instructor: Betty H.C. Cheng

1 Introduction This document outlines the requirements of the Cooperative Adaptive Cruise Control

system (CACC). Following the introduction, the purpose of this document as well as the

scope, definitions, and organization of the project are expanded. After this, the system is

described in more detail with respect to product perspective and function as well as user

characteristics. This section of the document also describes constraints, assumptions and

dependencies, and the appropriation of requirements. To aid in the formalization of the

system, a detailed list of requirements is used to capture the overall functionality. Next,

models are provided to show visually how the system interacts with users, other vehicles,

and the surrounding environment. Finally the prototype is described in detail to give the

customer a better idea of how the system functions. The last section of this document

gives all references and points of contact for further inquiries about the system.

1.1 Purpose

The purpose of the Software Requirements Specification (SRS) is to describe how the

CACC system behaves functionally so that the customer understands exactly what is

being developed for their desired product. The document also helps to complete the

agreement between the developer and customer so that the specified requirements are

being implemented to the customer’s satisfaction.

The SRS explicitly defines requirements, system behavior through modeling diagrams,

and prototypes to aid the customer in their understanding. This document also helps to

aid programmers in the solidification of requirements to be implemented and as a general

guide to aid future development, improvement, and maintenance.

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1.2 Scope

The software system being developed is the CACC system. This system is being

implemented as an embedded system for automobiles. The goal of this system is to make

highway travel safer by automating tasks typically handled by a human driver.

The CACC system functions much like the standard cruise control system that most users

are familiar with. The CACC system also utilizes forward facing radar and camera

systems. Both the camera and radar systems work to track vehicles in front of the user’s

vehicle. Once a vehicle has been detected, the CACC system automatically decreases the

user’s vehicle to the following distance specified by the user. After a vehicle is detected

the user has the option to start or join a platoon. Once the user is part of a platoon, the

vehicle communicates via radio to other vehicles in the platoon to get their GPS

information including speed, position, and direction of travel. Once the system is

engaged, the user has the option to increase or decrease the speed by increments of one

mile per hour. The user is still responsible for keeping their vehicle in its lane as the

system only affects the vehicle’s forward motion. The GPS system then works to help

detect possible collisions. Since all of the vehicles in the platoon are sharing information,

if one vehicle has to stop suddenly, then there is a significantly reduced chance of getting

into an accident because all of the vehicles are connected and can share data almost

instantly effectively making highway cruise control safer.

1.3 Definitions, acronyms, and abbreviations

Table 1.1 contains the definitions of all terms, acronyms, and abbreviations used in this

document.

Term Description

CACC The Cooperative Adaptive Cruise Control software system is responsible for tracking

other vehicles through GPS, radar, and camera systems and adjusting the braking and

acceleration of a user's vehicle accordingly

GPS The Global Positioning System is used to determine where a vehicle is, what speed

the vehicle is traveling at, and what direction the vehicle is headed. This system is

also used to help track and detect possible collisions between vehicles in the platoon

Lead Vehicle The vehicle at the front most position in the platoon that sets the speed of the platoon

Platoon A group of vehicles all engaged in the Cooperative Adaptive Cruise Control system.

The group may only travel in a single lane. A vehicle leaving the lane results in the

vehicle leaving the platoon

Target Vehicle The vehicle directly in front of the user’s vehicle. This is the vehicle that will be

tracked by the camera and radar systems

Trailing Vehicle The vehicle directly behind the user’s vehicle

CAN BUS The Controller Area Network Bus is the primary way that subsystems in the vehicle

will communicate with each other

VC The Vehicle Controller is responsible for coordinating all CACC subsystems and

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ultimately the main controller of the vehicle’s throttle and braking systems

ETC The Electronic Throttle Control is responsible for managing the power of the engine

CC The Cruise Control system ensures speed of the vehicle is constant and equal to the

speed set by the user

ACC The Adaptive Cruise Control system controls a vehicle’s acceleration and braking

depending on the location of the vehicle in front of it

Performance

Envelope A data set shared between vehicles in a platoon that describe a vehicle’s acceleration

and braking capabilities

Table 1.1: Definitions, acronyms, and abbreviations

1.4 Organization

Following the introduction of the CACC system the SRS describes the system in further

detail. The SRS does this by defining system design and layout through product

perspective and function as well as user characteristics and constraints. The CACC

system is then described in terms of requirements and accompanying models. Finally the

system prototype is explained as a practical implementation of the listed models. Lastly

references and points of contact are listed.

2 Overall Description This section provides a detailed description of the system. First the system’s functionality,

constraints, use prerequisites, and dependencies are discussed. This section also discusses the

context in which the system is used and what other subsystems it makes use of.

2.1 Product Perspective The CACC system will work closely with different subsystems in the vehicle. As shown in

Figure 2.1 below, the system receives information from the radar, GPS, and camera systems. The

system then sends this information to the radio where it is broadcast to other vehicles in the

platoon. The system also controls the Electronic Throttle Control system (ETC) and the Braking

system. Both of these subsystems work to control the speed of the vehicle. The system works with the limited resources of processing and memory in the vehicle while still

being very reliable. The system works in the current context of the vehicle using the Controller

Area Network (CAN) bus. The system also uses different peripherals that are shared between

systems. For instance, the camera is also used by the lane keeping system which is separate from

CACC. The user is also able to interact with the system easily. In the event of software failure,

the system informs the user that they are resuming control of the vehicle.

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Figure 2.1 Block Definition Diagram

2.2 Product Functions The system maintains a constant forward vehicle speed, as specified by the user. In addition,

using a combination of forward facing radar and camera systems, the system detects when a

target vehicle is in the user vehicle’s forward path and adjusts its own speed via throttle and

braking control to maintain one, two, or three car length(s) behind the target vehicle. The system

also receives GPS information such as, location, speed, and direction from other vehicles in the

platoon, and broadcasts its own GPS information. The system also receives information from the

satellite which helps with collision avoidance by checking to see if any vehicles are going to

collide with each other. Using the information from the different subsystems, the CACC system sets up a platoon of

vehicles that follow a lead vehicle with at least one car length of space between each vehicle. Any

vehicle with the system can receive requests to lead a platoon or send requests to join one. The

vehicle at the forefront of the platoon sets the speed for the whole platoon. Each following

vehicle in the platoon uses a combination of GPS information from the vehicles in front of it,

along with information from its own radar and camera sensors, to control its throttle and brakes to

achieve the desired following distance. A description of the vehicle’s performance envelope is

also shared among vehicles in the platoon, which includes acceleration and braking abilities of

the vehicle. The braking capabilities are shared in units of gravitation force (Gs). The

performance envelope helps the vehicles in the platoon make decisions about their braking when

it needs to be applied.

2.3 User Characteristics The user is expected to know how to drive a vehicle, have some minimal training about operating

a cruise control system, and have prior knowledge about the functionality of the buttons and

dashboard indicators.

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2.4 Constraints The system must be secure and safe to use in order for it to be used commercially. The constraints

of the system are:

1. The system must process information and make decisions in real-time.

2. The system must be able to inform the users of its status effectively and clearly.

3. The system must be able to hand control to the user in case of a system failure.

2.5 Assumptions and Dependencies The main dependency for the system is that all subsystems that the CACC system requires such

as camera, GPS, radar, radar transponder, radio, brakes, and ETC are all in place, operable, and

can communicate with the VC.

2.6 Appropriating of Requirements All the requirements of the project will be included in this version of the system.

3 Specific Requirements This section defines the requirements of the CACC system. The requirements are

enumerated below for clarity.

1. Radar Sensing

1.1. Radar will look to the target vehicle and constantly monitor for vehicles in

the vehicle’s path. If a vehicle is outside of the safe range, then the vehicle

will maintain its current speed. Once a vehicle enters an unsafe range in

front of the vehicle, this data would be given to the VC to handle when the

speed would be adjusted. The safe and unsafe ranges are determined by

the following distance that the user set. Anything less than the following

distance set by the user is considered an unsafe range. Anything greater

than or equal to the following distance is considered a safe range.

1.2. The system transponder is constantly monitoring at a rate of one cycle per

10 milliseconds for incoming link requests and sending out link requests

for other vehicles to connect to.

2. Radio Communication

2.1. The system will constantly broadcast its current speed and position to the

rest of the platoon and it will constantly communicate with the

infrastructure to get environmental conditions.

2.2. Radio communication will also be responsible for receiving metrics such

as speed and position from the rest of the platoon and the infrastructure.

3. ETC

3.1. The system will regulate the vehicle’s speed based on environmental

conditions such as rain or snow, and speed limits that are determined by

the infrastructure communication, by adding or removing power to the

vehicle.

3.2. The ETC will also increase or decrease the speed by adding or removing

power when the user increases or decreases the speed control.

4. The system will apply the vehicle’s brakes to a force that does not exceed 2Gs.

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5. The system will give its ID to requesting trailing vehicles on demand. The two

vehicles will then stay in contact with each other after initializing the radio

communication to relay GPS and speed data.

6. GPS System

6.1. The GPS system will communicate with satellite data to get the vehicle’s

position, speed, and direction information.

6.2. The GPS system will aid the radar system in compensating for curves and

hills on the roadway by communicating the information about their

location several seconds in advance.

6.3. If the radar system fails, then the GPS system will be used in place of

radar to maintain current platoon function.

7. Camera Sensing

7.1. Along with the radar system, the system will use a camera to identify a

target vehicle as well as estimate the target vehicle’s distance and relative

speed.

7.2. In the event of radar failure, the camera will aid the GPS system in

maintaining the platoon functionality.

8. Vehicle Controller

8.1. The system will coordinate all subsystems by taking in data from the

radar, camera, and GPS systems and determining a safe output for the

ETC and Braking System. This output will also take into consideration the

following distance that was set by the user.

8.2. The system will determine the vehicle’s speed, take into account the speed

of the lead vehicle, and adjust its own speed to maintain a ‘safe’ distance

based on environmental conditions, such as rain or snow and road

conditions, such as icy roads or flooded roads.

8.3. The system will maintain a current state consisting of its speed and

relative position to the target vehicle. The system will also include relative

environmental information in the state such as speed limits and road

conditions

8.4. The system will command the vehicle’s brakes and throttle to maintain a

speed within a predetermined minimum and maximum speed at a relative

distance to the target vehicle. This speed is set by the user when the user

turns on the CACC system.

8.5. The system will receive information from the radar system to update the

system’s current state at a rate of 10 milliseconds.

8.6. The system will send any requested information, such as speed and

position to other vehicles within the platoon though radio communication

links

8.7. The VC manages safe function of the platoon by setting the maximum

speed of the platoon to 85 miles per hour and the maximum number of

vehicles allowed in the platoon to 8 vehicles. If a vehicle is going over 85

miles per hour, then it will not be allowed to join or form a platoon.

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4 Modeling Requirements In order to give both the customer and developers a better understanding of the how the

CACC system functions, the following sections give examples of models of the system.

Use cases are first expanded followed by the domain model and data dictionary. Finally

sequence diagrams are showcased and the section is closed with system state diagrams.

4.1 Use Cases

The Use Case diagram in Figure 4.1 shows the functionality of the CACC system. In this

diagram, the actors are represented by people. These are the different entities that are not

a part of the system itself, but have an effect on the system. The box represents the

CACC system and anything within this box is a part of this system. The ovals inside of

the system represent the different uses of the system. There are lines connecting either

actors to use cases, or use cases to other use cases. These lines represent associations.

There are also lines with arrows pointing towards a use case. One is an include which

shows that the use case that is pointed to by an arrow is included as a part of the use case

that the arrow is coming from. Another line with an arrow is an extends. These lines

show special cases that have to be met by a certain circumstance. The arrow is pointing to

the use case that has the regular functionality.

Figure 4.1 Use Case Diagram

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Use Case: Start Up

Actors: User

Description: The user starts the CACC which initiates the camera, radar sensors, GPS

system, and communication systems.

Type: Primary

Includes: Communication, Car Monitor

Cross References: All Requirements

Use Cases: All

Use Case: Manual Override

Actors: User

Description: The user is able to override the CACC system at any time

Type: Primary

Cross References: Requirements 3, 3.2, and 4

Use Cases: Speed Control, Car Monitor

Use Case: Speed Control

Actors: Electronic Throttle Control, Braking System, User

Description: The user is able to control the speed of the vehicle. The speed is either

maintained, increased, or decreased depending on the distance and speed of the target

vehicle. The ETC increases or decreases power to the engine depending on the speed of

the vehicle and whether or not the vehicle is within a safe or unsafe range as specified by

the following distance. If the lead vehicle wants to set the speed to over 85 miles per

hour, then the system will be turned off, the user will be notified that the system is

shutting down because they are exceeding the maximum speed of the platoon, and the

user will be handed back control.

Type: Primary

Cross References: Requirements 3, 3.1, 3.2, 4, and 8.7

Use Cases: Distance Maintaining, Car Monitor

Use Case: Communication

Actors: Radio

Description: This is the short range communication between multiple vehicles. This

communication will tell the other vehicles in the platoon about its location and speed.

There can be up to 8 vehicles in the platoon that the radio will need to communicate with.

If the short range communication can not broadcast to all of the vehicles at once because

some are out of range, then the information can be retransmitted through other vehicles

throughout the platoon so that the vehicles outside of the broadcast range can receive the

information.

Type: Primary

Cross References: Requirements 2, 2.1, 2.2, 8, 8.6, and 8.7

Use Cases: Communication Failure, Start Up

Use Case: Communication Failure

Actors: Radio

Description: If the communication between two vehicles fails due to weather or the

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communication link was dropped, then the VC needs to know so that it can try to

reestablish the communication. If the communication can not be reestablished or the

process times out while trying to reconnect, then the system needs to be turned off and

the control needs to be handed back to the user. If the radio malfunctions, then the system

needs to be turned off and the control needs to be handed back to the user.

Type: Primary

Extends: Communication

Cross References: Requirements 2, 2.1, 2.2, 8, and 8.6

Use Cases: Communication

Use Case: Radar Failure

Actors: Radar

Description: The radar sensors work with the camera sensors to detect target vehicles. In

addition, it identifies the target vehicle’s ID so that a communication link can be

established. If the radar sensors fail, then the camera sensors will still be used to identify

target vehicles and estimate their distance and speed. The GPS will be used to maintain

platoon function.

Type: Primary

Cross References: Requirements 1, 5, 6, 6.3, and 8

Use Cases: Car Monitor

Use Case: Camera Failure

Actors: Camera

Description: The camera is used to visually identify target vehicles and estimate their

distance and relative speed. If the camera fails, then the GPS system can be used in its

place to gain the speed and position information. The radar will continue to track and

identify vehicles, and the radio will continue to communicate with the other vehicles.

Type: Primary

Cross References: Requirements 1, 2, 4, 6, 6.3, and 8


Use Case: GPS Failure

Actors: GPS

Description: The GPS is used to maintain vehicle position, speed, and direction

information. Also, it helps the radar system differentiate between vehicles and other fixed

targets along with helping with the curves and hills in the roadway. When the GPS fails,

the system will need to be shut down because the GPS maintains the vehicle’s position,

speed, and direction information and this is information that is essential to maintain the

platoon functionality.

Type: Primary

Cross References: Requirements 6, 6.2, 6.3, 8, 8.1, and 8.6


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Use Case: Car Monitor

Actors: Radar, Camera, GPS

Description: This use case contains the radar, camera, and GPS systems that work

together to carry out the following functions: detect other vehicles, maintain position,

maintain speed, and collect the directional information on other vehicles. This will also

be used to differentiate between vehicles and fixed objects as well as compensate for hills

and curves in the roadway.

Type: Primary

Includes: Distance Maintaining

Cross References: Requirements 1, 1.1, 1.2, 3, 3.1, 3.2, 4, 5, 6, 6.1, 6.2, 6.3, 7, 7.1, 7.2, 8,

8.1, 8.2, 8.3, 8.4, and 8.5

Use Cases: All

Use Case: Distance Maintaining

Actors: Radar, Camera, GPS, Electronic Throttle Control, Braking System

Description: The GPS, camera, radar, and radio systems work together to detect other

vehicles and gain information about their speed, direction, and position. It uses this

information to maintain a safe distance from the target vehicle.

Type: Primary

Includes: Speed Control

Cross References: All Requirements

Use Cases: Speed Control, Car Monitor, Communication

4.2 Domain Model The domain model gives a visualization of how the major system components

communicate with each other. Each box represents a subsystem of the CACC system.

Each line represents a communication link between the subsystems. This means that the

subsystems can directly talk to each other through the given operations of each

subsystem. Figure 4.2 below gives a representation of the CACC domain model.

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Figure 4.2: CACC System Domain Model

4.3 Data Dictionary

The data dictionary further expands the domain model by detailing the functions and

attributes used in the subsystems and further explains how the system communicates

within itself. Data dictionaries are made up of element names and descriptions, their

attributes, operations, and relations to other subsystems.

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Element Name Description

Vehicle Controller The Vehicle Controller (VC) is the main class in

the CACC system. It takes input from all of the

sensors and determines the speed of the vehicle.

Attributes:

int:cruiseSpeed The maximum cruising speed of the vehicle.

int:followDistance The distance to follow behind a target vehicle.

bool: isLead A flag to show an indicator to the user if they are

the lead vehicle in a platoon.

Operations:

isFunctioning() Does a check to make sure the VC is functioning

correctly by making sure all subsystems are

responding correctly.

increaseSpeed() Increases the cruising speed by increasing the

power of the ETC.

decreaseSpeed() Decreases the cruising speed by decreasing the

power of the ETC.

systemOn() Turns on the CACC system.

systemOff() Turns off the CACC system.

sendJoinPlatoon() Sends a request to a vehicle outside the platoon to

join the platoon if their CACC system is turned on.

receiveJoinPlatoon() Handles when another vehicle wants to join a

platoon the user is currently in.

exitPlatoon() Handles when a user exits from a platoon.

splitPlatoon() Splits one platoon into two separate platoons when

a vehicle unexpectedly enters or exits from the

middle of the platoon.

resume() Resumes CACC with the same variables before the

cancel button was pressed.

cancel()` Cancels the current CACC system and puts the

system in a neutral state without shutting down the

system.

getFollowDistance() Returns the follow distance of the user’s vehicle.

increaseDistance() Increase the following distance of the user’s

vehicle.

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decreaseDistance() Decrease the following distance of the user’s

vehicle.

receiveJoinRequest() Receives a request from another vehicle to join its

current platoon or create a new one.

setSpeed() Sets the user’s cruising speed.

response() A success or failure response sent as an

acknowledgement.

memoryCheck() Before a vehicle is accepted in a platoon the VC

checks to make sure it has enough space in

memory to accommodate another vehicle.

Relationship The VC talks to every other subsystem within the

system. It also handles the user’s control requests

and is responsible for electronic throttle and

braking management.


Camera The camera is used to aid the radar tracking

subsystem by identifying the target vehicle’s speed

and distance from the user’s vehicle.

Attributes:

Operations:

isFunctioning() Check to make sure that the camera system is

functioning correctly.

identifyTargetVehicle() Aids in the detection of a target vehicle.

estimateSpeed() Returns the estimated speed of the target vehicle.

estimateDistance() Returns the estimated distance of the target

vehicle.

Relationship The camera subsystem continuously talks to the

VC to help aid the radar system in the tracking of

target vehicles so that the VC can determine

whether or not to increase or decrease speed and

braking force.


Braking Controller The braking subsystem is responsible for

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controlling vehicle speed by applying braking

pressure.

Attributes:

int:brakeForce The braking force the braking system will apply

when the brakes are engaged.

Operations:

isFunctioning() Check to make sure that the braking system is


getBrakeForce() Returns the braking force that the braking system

will use.

setBrakeForce(int brakeForce) Sets the braking force that the braking system will

use.

applyBrakes(int brakeForce) Applies a given brake force to slow the vehicle.

Relationship The braking system talks with the VC. Brakes are

the system default for any safety issue where there

is conflicting information from other subsystems.


Electronic Throttle Control The Electronic Throttle Control (ETC) subsystem

is responsible for controlling vehicle speed by

regulating power to the engine.

Attributes:

int:power The amount of power that the subsystem will apply

when the ETC is engaged.

Operations:

isFunctioning() Check to make sure that the ETC system is


getPower() Returns the engine power that the ETC system will

use.

setPower(int power) Sets the engine power that the ETC system will

use.

applyPower(int power) Applies the given power to the engine.

Relationship The ETC system talks with the VC to set engine

power appropriately.

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Radar The main function for the radar subsystem is to

scan in front of the user’s vehicle to help detect,

identify, and track other vehicles.

Attributes:

Operations:

isFunctioning() Check to make sure that the radar system is


detectTargetVehicle() Scans the area in front of the vehicle looking for

other vehicles.

identifyTargetVehicle() Identifies target vehicles after detection, looking

for the CACC system.

trackTargetVehicle() Tracks the target vehicle to keep the user vehicle at

a safe distance behind.

getTargetVehicleData() Gets the target vehicle’s information such as speed

and position.

noTargetVehicle() Lost track of target vehicle, or scanned but was

unable to find any.

Relationship The radar subsystem is the primary system for the

detection and identification of target vehicles.

Once detected the radar feeds information to the

VC where the VC can determine if it should

increase or decrease braking pressure or engine

power. It also talks to the radar transponder to send

vehicle information to the vehicle behind it.


User Controls The user controls refer to the buttons and

indicators located on the dash of the vehicle that

the user will control the subsystem with.

Attributes:

Operations:

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isFunctioning() Check to make sure that the user control subsystem

is functioning correctly.

btnOn() Turns the CACC system on.

btnOff() Turns the CACC system off.

btnIncreaseSpeed() Increases the set cruising speed if only in CC mode

or maximum cruising speed if in CACC mode.

btnDecreaseSpeed() Decreases the set cruising speed if only in CC

mode or maximum cruising speed if in CACC

mode.

btnIncreaseDistance() Increases the distance of the gap between the user's

vehicle and the target vehicle.

btnDecreaseDistance() Decreases the distance of the gap between the

user's vehicle and the target vehicle.

btnEngage() Sends a request to a platoon to join.

setDistanceIndicator() Sets the distance indicator based on the current

following distance.

setInPlatoonIndicator() Sets the indicator to let the user know they are part

of a platoon.

setLeadCarIndicator() Sets the indicator to let the user know they are the

lead vehicle in a platoon.

setActiveIndicator() Sets the indicator to let the user know that the

CACC system is active, not canceled.

setInactiveIndicator() Set the indicator to let the user know that the

CACC system is not active, that it is currently

canceled.

btnCancel() Cancels the current CACC system without turning

the system off. This has the same functionality as a

pause function.

btnResume() Resumes the CACC system from a canceled state

as long as the whole system was not shut off.

btnSetSpeed() Sets the user vehicle’s cruising speed.

Relationship The user controls are the primary way for the user

to interact with the system. This subsystem talks

directly to the VC to help determine the action the

VC should take.


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GPS Responsible for gathering vehicle data,

broadcasting it to other vehicles, as well as

differentiating between vehicle targets and known

fixed targets.

Attributes:

Operations:

isFunctioning() Check to make sure that the GPS subsystem is


getSpeed() Returns the speed of the user’s vehicle.

getPosition() Returns the position of the user’s vehicle.

getDirection() Returns the direction of the user’s vehicle.

Relationship The GPS talks to the VC to give it information

about the position of the vehicle so that the VC can

determine the action it should take. From here, the

VC can broadcast the GPS information through the

radio.


Radio The primary means of communication within the

platoon for the vehicles to talk to each other and

pass information.

Attributes:

Operations:

isFunctioning() Check to make sure that the radio subsystem is


requestID() Ask for a vehicle’s unique identification.

broadcastGPS() Sends out the user vehicle’s GPS to the entire

platoon.

receiveGPS() Receives GPS information being broadcast by all

other vehicles in the platoon

sendJoinPlatoon() Sends request to vehicle in front to join it in

already formed platoon or new platoon.

sendRequestResponse() Sends an acceptance or denial to a request of

another vehicle to form a new platoon or join the

existing one.

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receiveInfrastructureSignal() Receives information broadcasted by the

infrastructure.

noTrailingVehicle() Does not receive GPS information of trailing

vehicle or receives an exit signal (when the system

is the lead vehicle).

reestablishConnection() If radio contact is lost for any vehicle in the

platoon, the radio first tries to reestablish a

connection before booting the lost vehicle from the

platoon

Relationship The GPS system communicates with the VC where

vehicle position, speed, and direction can be

stored, analyzed, and then sent to the platoon.


Radar Transponder Responsible for giving vehicle ID information to

requesting trailing vehicle.

Attributes:

Operations:

isFunctioning() Check to make sure that the radar transponder

subsystem is functioning correctly.

sendVehicleID() Sends user vehicle’s identification to trailing

vehicle when requested.

Relationship The radar transponder talks with the trailing

vehicle, giving it information about the user’s

vehicle when requested.


Platoon Vehicle Represents a vehicle in a platoon. This save

information about the vehicle including its ID and

position in the platoon.

Attributes:

int ID A vehicle’s unique identification number.

int Position The vehicle’s position in the platoon. 0 is the lead

vehicle and the number increases by 1 for each

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position in the platoon.

Operations:

Relationship Platoon vehicles interact with the camera, radar,

radar transponder, and radio subsystem to

effectively communicate vehicle information to the

other vehicles in a platoon.

4.4 Sequence Diagrams

Sequence diagrams show a more detailed view of how the system behaves technically

when certain events or activities happen within the system. Figures 4.3 through 4.10

show the sequences for user scenarios. In each scenario there is an actor who starts an

interaction with the CACC system. Arrows represents messages sent between subsystems

when certain events happen and the boxes represents the subsystem that the messages is

being received at or sent from.

Figure 4.3 depicts the “turn on” scenario where a user enters the highway and wants to

turn the CACC system on.

Figure 4.3: Turn On Sequence Diagram

Figure 4.4 depicts the “turn off” scenario where, a user is using the system on the

highway and is approaching an exit. The user decides to turn off the CACC system to

take control of the vehicle and exit the highway.

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Figure 4.4: Turn Off Sequence Diagram

Figure 4.5 depicts the “send request to join platoon” scenario where, a user is driving on a

highway and decides to turn on the system. Then the user notices a platoon of cars

engaged in the CACC system. They request to join the platoon.

Figure 4.5: Send Request to Join Platoon Sequence diagram

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Figure 4.6 illustrates the “receive request to join platoon” scenario where a user is driving

on a highway and has the CACC system on, but is currently not in a platoon. Another

vehicle requests to join the user by creating a platoon.

Figure 4.6: Receive Request to Join Platoon Sequence Diagram

Figure 4.7 shows the “cancel” scenario. A user is driving along a highway and is the last

person in a platoon of three vehicles. The user has been driving for a while and decides to

pull over at the next rest stop. Instead of turning the CACC system completely off the

user decides to hit cancel so they can resume with their previous settings after making the

stop.

Figure 4.7: Cancel Sequence Diagram

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Figure 4.8 displays the “resume” scenario. A user is returning from a quick break at a

rest stop while driving down the highway. After getting back up to speed the user decided

to resume their previous CACC state. The user pressed the resume button and their

settings from earlier are restored.

Figure 4.8: Resume Sequence Diagram

Figure 4.9 shows the “increase distance” scenario. A user is driving along the highway

with the CACC system engaged. The user is behind the lead vehicle. The lead vehicle is a

rather expensive vehicle and even though the user has full confidence that the system will

not fail, the user decides to increase their following distance.

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Figure 4.9: Increase Distance Sequence Diagram

Figure 4.10 depicts the “decrease distance” scenario. A user is behind the lead vehicle.

The user is coming home in rush hour traffic. They notice that vehicles keep cutting into

the space between their vehicle and the lead vehicle. The user decides to decrease their

following distance to keep this from happening.

Figure 4.10: Decrease Distance Sequence Diagram

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4.5 System State Diagrams

System state diagrams are used to show the various states that a system can take and how

the system can enter and exit from these states. The boxes represent the different states

the system can be in at any single time. The arrows represent the transition from one state

to another. The first diagram, Figure 4.11, explains the highest level view of the system

that starts and ends with the ignition off.

Figure 4.11: Vehicle system state diagram

The second diagram, Figure 4.12, explains the internal blocks when the system is on. It

also shows the different levels that the Cruise Control system can operate in.

Figure 4.12: CC system state diagram

The Third and Fourth diagrams, Figures 4.13 and 4.14 respectively, show the details of

the ‘ACC set’ state and ‘CACC on’ state from the second diagram.

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Figure 4.13: ACC system state diagram

Figure 4.15: CACC system state diagram

5 Prototype The prototype shows two views side by side. The first view is the view from the user’s position.

In this view, there are indicators that show if the user is in a platoon, if the user’s vehicle is the

lead vehicle in the platoon, and what the following distance is currently set to. It also displays

user controls for increasing or decreasing speed, turning the system on or off, and increasing or

decreasing the following distance. This system also has a button called engage that sends the

request for the user’s vehicle to join a platoon. The second view shows a bird’s eye view of the platoon as it drives down the highway. From

here the current state of the platoon can be seen based the buttons the user presses.

5.1 How to Run Prototype All that is needed to run the prototype is a modern Internet browser that can run HTML5 and has

JavaScript turned on. No system configurations or web plug-ins are needed.

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The prototype can be accessed at the follow link:

https://www.cse.msu.edu/~cse435/Projects/F2014/Groups/CACC/web/test_proto/protov3

.html

5.2 Sample Scenarios

Scenario 1: A user is driving down the highway without the CACC system turned on. The

user then turns the system on, sets the speed and follow distance, and then engages the

system. The user’s vehicle will now be in a platoon based on the leading vehicle.

Scenario 2: The lead vehicle exits the platoon and the user’s vehicle is now the platoon

leader. The user’s vehicle will continue at the same speed unless changed by the user.

Figure 5.1 shows the interface for the current prototype for Scenario 1.

Figure 5.1: Prototype Interface

Figure 5.2 shows the interface for the current prototype for Scenario 2.

Figure 5.2: Prototype Interface

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6 References

[1] BMW Technology Guide: Active Cruise Control." BMW Technology

Guide: Active Cruise Control. N.p., n.d. Tues. 14 Oct. 2014.

http://www.bmw.com/com/en/insights/technology/technology_guide/articles/activ

e_cruise_control.html

[2] Jones, Stephen. Cooperative Adaptive Cruise Control: Human Factors

Analysis. No. FHWA-HRT-13-045. 2013.

http://www.fhwa.dot.gov/publications/research/safety/13045/13045.pdf

[3] M. Austin. (2013). Toyota's Semi-Autonomous Cars Hit the Highway

[online]. http://www.popularmechanics.com/cars/news/industry/toyotas-semi-

autonomous-cars-hit-the-real-road-16024804

[4] Shladover, Lu, Nowakowski.(2015) Using Cooperative Adaptive Cruise

Control to From High-Performance Vehicle Streams

http://www.automatedvehiclessymposium.org/callforposters/using-cooperative-

adaptive

7 Point of Contact

For further information regarding this document and project, please contact Prof. Betty

H.C. Cheng at Michigan State University (chengb at cse.msu.edu). All materials in this

document have been sanitized for proprietary data. The students and the instructor

gratefully acknowledge the participation of our industrial collaborators.

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