srs document.docxcse435/projects/f2013/groups/cacc1/docs/sr… · web viewthis software...

Platoon Control | 1 Software Requirements Specification

Software Requirements Specifications

Cooperative Adaptive Cruise Control

Team CACC1

Prepared By: Kathy Cummings Garrett Stevenson Phil Plachta Jack Schinderle

Customer: Ford Motor Company

Instructor: Dr. Betty H. C. Cheng


Contents Table 1. Introduction

1.1 Purpose1.2 Scope1.3 Definitions, acronyms, and abbreviations1.4 Organization

2. Overall Description2.1 Product Perspective2.2 Product Functions2.3 User Characteristics2.4 Constraints2.5 Assumptions and Dependencies2.6 Approportioning of Requirements

3. Specific Requirements4. Modeling Requirements

4.1 Class Diagram4.2 Sequence Diagram4.3 Use Case Diagram4.4 Use Cases

5. Prototype5.1 How to Run Prototype5.2 Sample Scenarios

6. References7. Point of Contact


1 Introduction

This Software Requirements Specification (SRS) document provides information about the Cooperative Adaptive Cruise Control system (CACC). There are five parts in this section: introduction, purpose, scope, definitions, acronyms and abbreviations, and organization. The introduction provides an overview of the SRS document and indicates the topics to be covered. The purpose indicates the reason for writing the SRS document and its intended audience. The scope describes the software products that will be produced, the domain and objectives of these products, and also covers what the software product should or should not do. The Definitions, acronyms, and abbreviations section defines all terms, acronyms, and abbreviations used in the SRS document to help reduce any confusion. Finally, the organization details the rest of the sections in the SRS document.

1.1 Purpose

The purpose of the document is to collect and analyze the system and its requirements with respect to its consumers. This document will aid in predicting how we hope this product will be used in order to gain a better understanding of the project, outline concepts that may be developed later, and document ideas that are being considered. However, these ideas may be discarded as the product develops. The target audience of this SRS document are the engineers at the Ford Motor Company.

1.2 Scope

The software product to be developed is the CACC system. This is an embedded system for all vehicles, an intelligent form of cruise control that decelerates and accelerates automatically to keep pace with the vehicle in front of it. Assisting the user in a variety of road conditions including, but not limited to, congested traffic conditions, adverse weather and road conditions, varying states of health of vehicle equipment, and varying skill levels of users. This product will not aid in the control of the vehicle.

1.3 Definitions, acronyms, and abbreviations

Adaptive Cruise Control (ACC) - A cruise control system for vehicles that adjusts vehicle speed through use of sensors and a vehicle controller to maintain a safe distance from vehicles ahead.Brake by wire - When instructed by the vehicle controller apply brakes from 0% to 100% of maximum braking power defined by the vehicle performance envelope. Cooperative Adaptive Cruise Control (CACC) - A cruise control system for vehicles that adjusts vehicle speed through the use of sensors and a vehicle controller to maintain a safe distance (gap) from vehicles ahead. In addition to this a CACC system must also be able to join a


platoon, leave a platoon, detect when target vehicles are CACC enabled, and acquire an ID from an authoritative infrastructure.Dedicated short range communication (DSRC) - A short to medium range communication service for vehicle-to vehicle communication, providing very high data transfer rates while minimizing latency in the communication link and isolating relatively small communication zones.Electronic Throttle Control - When instructed by the vehicle controller accelerate from 0% to 100% of maximum accelerating power defined by the vehicle performance envelope.Heads Up Display (HUD) - The display in a vehicle that contains warnings, instrument panels (speedometer, odometer, tachyometer), and other information.Infrastructure - The part of the CACC system outside of individual vehicles that assigns and validates VNAs. It consists of towers which communicate with vehicles by radio and then pass on communication to centralized servers.Gap - Distance between two vehicles in a platoon. This is set by the lead vehicle in the platoon and is maintained by the vehicle controller. The gap setting is based on following distance of vehicles on the highway traveling at 70 mph or 102.67 fps. The maximum Gap distance allowed is 5 seconds or 513 feet while the minimum gap distance allowed is 2 seconds or 205 feet.Gap Increment - The increases and decreases in gap when using steering wheel controls. The gap setting is based on following distance of vehicles on the highway traveling at 70 mph or 102.67 fps. The lowest gap setting represents 2 seconds of following time or 205 feet. A gap increment is approximately ½ second or 51.3 feet. There are a total of 7 different gap settings representing following times of 2, 2.5, 3, 3.5, 4, 4.5, 5.Lead Vehicle - The vehicle in the front of the platoon.Performance Envelope- Predetermined values including maximum braking power defined in gees and maximum acceleration defined in gees.Platoon - A group of CACC enabled vehicles traveling contiguouslySRS - Software Requirements SpecificationTarget Vehicle - A vehicle in front of the CACC enabled vehicleTransponder - A device located at the rear of all CACC enabled vehicles that transmits vehicle ID to a requesting vehicle with a valid Vehicle Network Address (VNA) and establishes a radio link between the two vehicles that allows for the transmission of information.Vehicle Network Address (VNA) - A dynamic identifier assigned to a CACC vehicle by the system infrastructure.

1.4 Organization

The remainder of this document is divided as follows:

Section 2 contains an overall description of the CACC system including a description of the domain, product and general functionality of the system.

Section 3 contains a detailed outline of specific functional requirements of the system.


Section 4 supplies a range of behavioral and structural diagrams and outlines specific scenarios to be handled by the system.

Section 5 contains an overview of the CACC prototype including the prototype’s use and functionality.

2 Overall Description

This section describes the focus of the CACC system, as well as how it interacts with other systems and subsystems. Assumptions and limitations of both the system’s environment and the system itself are listed and discussed. There is a brief profile of the targeted users and how they are expected to interact with the system interface.

2.1 Product Perspective

The CACC system is designed to make travel on the highway more efficient. Its goal is to provide convenience and safety features for vehicles traveling on the road. The system’s intent is to not only display warnings in the event of an unsafe condition such as a car that a vehicle is approaching that is going slower, but to manipulate subsystems to physically decelerate or accelerate the vehicle. This system is an expansion of the ACC system.

Interface constraints that the system will face are it must itself fit into the vehicle while not impeding any of the vehicle’s normal functions. The user interface must be easily viewable by the user while not inhibiting her/his vision. The hardware must have backup systems in place in case of failure. The hardware must not impede any of the vehicle’s normal functions. The software must be extremely reliable and therefore must have both software and hardware backups in place in case of failures. If any software or hardware system fails CACC must be disabled and the user must be warned if possible.

2.2 Product Functions

The CACC system’s primary purpose is to form a platoon of vehicles, each enabled with CACC, that move at a constant speed and maintain a safe gap between each vehicle. Information is shared between these vehicles to coordinate braking and acceleration of the platoon, given the varying capabilities of each individual vehicle. Also included with the CACC system are features such as lane keeping / lane centering technology and curve speed assist.

2.3 User Characteristics

Due to the fact that the system will be mounted on private as well as commercial vehicles, very few assumptions are made about the skill level and expertise of the system users. The wide range of possible users precludes this as a viable option. There are however, several


key assumptions. Users are assumed to have a valid motor vehicle operator license as well as a lawful understanding of applicable driving laws and regulations. The system is a convenience feature and it is necessary that the user is able to assume control of the vehicle.

In addition, it is assumed that all vehicles have fully functioning turn signals and brake lights. This is necessary to help the system determine the intentions of other vehicles on the road. The camera system used to visually detect vehicles is reliant on brake lights. Situations with poor visibility such as heavy precipitation or fog reduce the effectiveness of visual sensors and brake lights help reduce the negative impact caused by poor visibility.

2.4 Constraints

Use of the CACC system is limited to a highway environment, with restricted on and off access. The main cruise control portion of the system will not function at speeds of 25 miles per hour or lower, and so is not meant for use in driving environments where slower speeds and complete stops are necessary. In addition, the CACC system can only be utilized in areas where it is able to communicate with infrastructure outside of the vehicle. Although many types of vehicles may utilize CACC, the system will not work with vehicles that are pulling trailers.

Because the purpose of the CACC system is to form platoons, it requires more than one CACC enabled vehicle to function to its full capacity. Information must be passed between the vehicles of the platoon without compromising the privacy of the users or owners of the vehicles. A platoon is limited in size to 6 vehicles, after which other CACC vehicles will be unable to join the platoon. The CACC system itself is also composed of multiple parts, such as the camera, the radar, and the radio. If any of these should fail, the system as a whole cannot function and fails as well.

2.5 Assumptions and Dependencies

Because utilizing CACC effectively requires multiple vehicles, the success of a CACC system is reliant on the assumption that users can agree on the constant speed of the platoon. It also assumes that its use will be limited to freeway driving with periodic on/off access, as the system is not designed to function in other environments. Although the system controls acceleration and braking, it does require that the system user be actively controlling the steering, as well as responding to any warnings or signals provided by the system. As the system is integrated into the vehicle itself, its acceleration and braking capabilities are limited by the vehicle’s performance envelope. Gap length between vehicles in a platoon is set by the platoon leader. It is assumed that all vehicles will be properly maintained by users and will have access to communicate with infrastructure.

2.6 Approportioning of Requirements

There are currently a number of requirements that are beyond the scope of the current project. The first being the system will not handle platoons larger than six vehicles long. The


system will also assume freeway driving. Another being the system will not take control of the steering. The system will only alert the user by visual or physical warnings.

3. Specific RequirementsThis section explicitly states the requirements for the project. The requirements are broken down by functionality.

3.1 Requirement Specification

1. Radar Sensing1.a. Radar sensing system must be able to detect, id and track target vehicles1.b. Radar sensing must be able to identify target vehicle’s VNA through transponder for

purposes of establishing a DSRC communication link.

2. Radio Communication2.a. Radio communication system must be able to communicate with target vehicle to

receive information about other vehicle’s distance, speed, whether it is in a platoon, if it is about to brake, or accelerate.

2.b. Radio communication system must be able to communicate with trailing vehicle to transmit speed, location, platoon status, whether vehicle is about to brake or accelerate.

2.c. Radio communication system must be able to communicate with infrastructure to receive an authoritative VNA to confirm its validity.

3. Electronic Throttle Control3.a. The electronic throttle control system must regulate vehicle speed as instructed by

the vehicle controller. If the vehicle controller decides that vehicle speed must be increased electronic throttle control must engage according to the vehicle controllers command and bring vehicle to commanded speed.

4. Brake by wire 4.a Brake by wire must regulate vehicle speed as instructed by the vehicle controller. If the vehicle controller decides that speed must be decreased, brake by wire must engage as according to the vehicle controllers command to bring vehicle to commanded speed.

5. Radar Transponder 5.a. When requested by a vehicle with valid VNA, transmit vehicle VNA and information such as speed, location, whether it is in a platoon, or if it has CACC enabled to requesting trailing vehicle in order to establish radio link between vehicles.

6. GPS System


6.a. The GPS system must be able to maintain accurate vehicle position, speed and direction information to be transmitted to vehicles requesting information and to evaluated by the vehicle controller.

6.b. The GPS systems must be able to aid radar system by differentiating between vehicle targets from known fixed target. 6.c. The GPS system must be able to provide information about upcoming curve or hills in roadway and inform the vehicle controller so it can send requests to engage brake by wire or electronic throttle control.

6.d. The GPS system must be able to aid the vehicle controller by providing information such as speed, location, direction, and gap distance in the event of radar or transponder failure so the vehicle controller can make valid requests to the brake by wire and electronic throttle control.

7. Camera Sensing7.a. The camera sensing system must be able to visually identify the distance between

the vehicle and target vehicle.7.b. The camera sensing system must be able to visually identify the relative speed of

target vehicle.

8. Vehicle Controller 8.a. The vehicle controller must coordinate all sub-systems.

8.b. The vehicle controller must be able to receive information from the radar sensing system, the GPS system, the camera and radio systems.

8.c. The vehicle controller must be able to detect vehicle speed, speed of lead vehicle and adjust speed by sending commands to the brake-by-wire or throttle control to maintain the defined gap. 4.d. The vehicle controller must maintain the state of the vehicle and operating environment information and transmit this information to the vehicles around them. 8.e. Commands brake and throttle.

8.f. Receives information from radar system.8.g. Sends and receives information from radio system.

9. User Interface9.a. The system has an on/off toggle button on the steering wheel.9.b. The system has a cancel button on the steering wheel.9.c. The system has a resume button on the steering wheel.9.d. The system has cruise speed up and cruise speed down buttons on the steering

wheel.9.e. The system has gap increment and gap decrement buttons on the steering wheel.9.f. The system displays warnings on the vehicle’s HUD.9.g The system plays audio cues to alert the driver


4 Modeling RequirementsThis section contains models for better understanding the project requirements. A class

diagram, several sequence diagrams, and a use case diagram are included in this section.

4.1 Class Diagram


4.2 Sequence Diagrams

This Sequence Diagram shows the order in which the components of the system are initialized when the CACC system is turned on.


This Sequence Diagram shows the process for joining a platoon


Sequence Diagram for slowing vehicle when cruise is engaged. Depicts how the vehicle applies brakes using the Brake By Wire Controller.


4.3 Use Case Diagram


4.4 Use Cases

Use Case Join PlatoonActors Other CACC Vehicles, User’s VehicleType Primary (Essential)Description

A Vehicle equipped with CACC joins a pre-existing platoon. Can be the user’s vehicle or any other vehicle with a CACC system.

Use Cases

Turn On

Use Case Leave PlatoonActors Other CACC Vehicles, User’s VehicleType Primary (Essential)Description

A Vehicle equipped with CACC joins a pre-existing platoon. Can be the user’s vehicle or any other vehicle with a CACC system.

Use Cases

Turn On

Use Case Split PlatoonActors Other Non-CACC VehicleType Primary (Essential)Description

A Vehicle without a CACC system (Non-CACC vehicle) merges or changes lanes resulting in the Non-CACC vehicle entering the lane in front of the user’s vehicle and in the middle of the user’s platoon. When this occurs, the user’s vehicle then becomes the first vehicle


in a new platoon.Use Cases

Turn On

Use Case Transmit DataActors Radio System, Radar Transponder, Other CACC Equipped

VehiclesType Primary (Essential)Description

A CACC System transmits data using either the radio system or the radar transponder. The radio system is used to transmit vehicle information (speed, location, heading) to other CACC equipped vehicles. The radar transponder is used to transmit VNA information for establishing connection with other vehicles.

Use Cases

Turn On

Use Case Receive DataActors Other CACC Equipped Vehicles, Radio System,

InfrastructureType Primary (Essential)Description

The system receives data from either the transportation infrastructure or other CACC equipped vehicles via the radio system.

Use Cases

Turn On

Use Case Connect with CACC VehicleActors Radio System, Radar Transponder, Other CACC Equipped


VehiclesType Primary (Essential)Description

A connection is established with another CACC equipped vehicle via DSRC.

Use Cases

Turn On

Use Case Check SpeedActors User’s Vehicle, Camera Sensor, Forward Radar Sensor,

GPS UnitType Secondary (Essential)Description

Data from the user’s vehicle, the camera sensor, forward radar sensor, as well as the GPS unit is evaluated in order to determine what action (Brake, Coast, Accelerate) is needed to maintain vehicle speed and following distance.

Use Cases

Turn On

Includes Brake, Coast, Accelerate

Use Case BrakeActors Brake By Wire Controller, User’s VehicleType Secondary (Essential)Description

The brake by wire controller is used to activate the vehicle’s brakes in order to maintain a safe following distance to the target vehicle.

Use Cases

Check Speed, Turn On


Includes Alert User

Use Case CoastActors Throttle Controller, User’s VehicleType Secondary (Essential)Description

The throttle controller is used to set vehicle acceleration to zero (0) in order to maintain a safe following distance to the target vehicle.

Use Cases


Use Case AccelerateActors Throttle Controller, User’s VehicleType Secondary (Essential)Description

The throttle controller is used to increase the user’s vehicle’s acceleration in order to maintain a safe following distance.

Use Cases


Use Case Identify ObstacleActors Camera Sensor, Forward Radar SensorType Primary (Essential)Description

The camera sensor and the radar sensor are used in combination in order to detect obstacles in the vehicle’s path. When an obstacle is detected, distance to the object, the object’s heading, and the object’s speed are determined.


Use Cases

Turn On

Includes Check Speed

Use Case Alert UserActors UserType Primary (Essential)Description

When the vehicle must brake or if a collision is likely, the system alerts the driver with a notification on the HUD and audio cues.

Use Cases

Turn On

Use Case Turn OnActors UserType Primary (Essential)Description

The user turns on the CACC system.

Use Cases

Turn Off

Use Case Turn OffActors UserType Primary (Essential)Description

The user turns off the CACC system.

Use Turn On


Cases

Use Case CancelActors UserType Primary (Essential)Description

The cancel feature deactivates the CACC system but does not turn it off. This preserves speed and gap settings to allow for system reactivation with the Resume button.

Use Cases

Turn On

Use Case ResumeActors UserType Primary (Essential)Description

The resume function activates the CACC system with the last used settings.

Use Cases

Turn On

Use Case Increase/Set Cruise SpeedActors UserType Primary (Essential)Description

The CACC system cruise speed is set to the user’s vehicle’s current speed if the system is not activated. If the system is activated, the cruise speed is incremented by one mile per hour (+1 mph).


Use Cases

Turn On

Use Case Decrease Cruise SpeedActors UserType Primary (Essential)Description

When the CACC system is active, the cruise speed is decreased by one mile per hour (-1 mph).

Use Cases

Turn On

Use Case Increase GapActors UserType Primary (Essential)Description

If the current gap setting is not at the maximum allowed setting (5 seconds), the gap setting is increased by one gap increment.

Use Cases

Turn On

Use Case Decrease GapActors UserType Primary (Essential)Description

If the current gap setting is not at the lowest allowed setting (2 seconds), the gap setting is decreased by one gap increment.

Use Turn On


Cases

5 Prototype


The first prototype depicts the scenario involving a CACC vehicle joining an existing platoon at the end (the vehicle joining becomes the last vehicle in the platoon). The second prototype depicts the scenario involving a CACC vehicle joining an existing platoon in a position other than the end. The third prototype depicts the scenario involving a non CACC vehicle splitting an existing platoon into two platoons by entering the middle.

5.1 How to Run Prototype

The prototype was designed to be viewed in the Firefox web browser on a computer with an internet connection. The latest flash plugin (version 11.9 or higher) for the users browser is also required. If these requirements are met the prototype may be viewed at the following link: http://www.cse.msu.edu/~cse435/Projects/F2013/Groups/CACC1/web/prototypes.php

5.2 Sample Scenarios

Scenario 1: A platoon of four CACC equipped vehicles are traveling down a road. The lead vehicle's performance profile is that of a sport utility vehicle with a mass of 2987 kilograms and a max braking force of 1.87 gees. The second vehicle is a sports car with a mass of 1321 kilograms and a max braking force of 2.5 gees. The third vehicle is a semi truck with a mass of 15894 kilograms and a max braking force of 1.66 gees. The fourth vehicle in the platoon is a four door sedan with a mass of 2356 kilograms and a max braking force of 2.00 gees. In this scenario, the platoon is initially travelling with a velocity of 67 miles per hour when the lead vehicle detects a vehicle up ahead with its sensors and determines that the platoon will need to slow down to 64 miles per hour in order to maintain a safe following distance. The lead vehicle transmits a signal via its rear transmitter containing this information and begins to coast. The second vehicle in the platoon receives the signal from the lead vehicle and after appending its own performance information to the message, transmits it via its rear transmitter. This process is repeated with the semi truck as well as the final vehicle, the sedan. In this scenario, the sedan also transmits the coast signal via its rear transmitter - the system does not know the position of the vehicle in a platoon.

Scenario 2: The same platoon as described in scenario 1 is traveling along a road. A non CACC equipped vehicle comes up from behind the platoon in the opposite lane and then proceeds to merge into the middle of the platoon between the second and third vehicles. In order to avoid a collision and to maintain a safe following distance, the semi truck (vehicle in third position) simultaneously transmits coast/brake message and slows to allow space for the new vehicle. The sedan behind the semi truck receives the information and slows as well. The sedan’s performance profile includes better braking performance than the semi truck in front of it and it is therefore able to safely maintain proper following distance behind the semi truck. The non CACC vehicle moves into the space between the semi truck and the sports car. The semi truck behind the new vehicle does not detect any transmissions from the vehicle in front of it (the non-CACC vehicle that has just merged) and therefore the system on board the semi truck


removes the semi truck from the platoon by creating a new platoon with the semi truck as the lead vehicle. The new platoon then slows if necessary to establish safe following distance.

6 References

[1] Alonso, Luciano; Milanés, Vicente; Torre-Ferrero, Carlos; Godoy, Jorge; Oria, Juan P.; De Pedro, Teresa. 2011. "Ultrasonic Sensors in Urban Traffic Driving-Aid Systems." Sensors 11, no. 1: 661-673.

[2] Wolf, S. Richard. “DSRC: A short range wireless technology for Telematics Applications.” Slides 3-6. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.coe.montana.edu%2Fee%2Frwolff%2Fshel%2520leader%2520dsrc.pdf&ei=JO52Uq4uoZ_JAZCXgDA&usg=AFQjCNGAUi7EQDHmyUZR7h9FWAvUifeO_w&sig2=6A6_t2AfRQAxQWnR6DVgAQ&bvm=bv.55819444,d.aWc

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.

srs document.docxcse435/projects/f2013/groups/cacc1/docs/sr… · web viewthis software...

Documents