SRS for Team ADS.docx - Michigan State Universitycse435/Projects/F2013/Groups/ADS/Docs... · Web viewIt is to be an automotive system with the end goal of reducing fuel usage by turning

Software Requirements Specification (SRS)

Assisted Direct Start

Authors: Alec Dutch, Cameron Keif, Taylor Jones, Duncan Young

Customer: Ford Motor Company

Instructor: Dr. Betty Cheng

1 Introduction

The SRS document is divided into 7 subsections - Introduction, Overall Description, Specific Requirements, Modeling Requirements, Prototype, References, and Point of Contact. The bulk of the document is contained in the Overall Description section, which provides an overview of the ADS system and how it will integrate with existing components; Specific Requirements, which provides an enumerated list of the system’s required behavior; and Modeling Requirements, which contains class, state, and sequence UML diagrams that describe the structure of the ADS system.

1.1 Purpose

The purpose of the SRS document is to lay out the specifications of the project and assure that the developer and the customer are in agreement about the project details. In this case, the audience is the customer at Ford Motor Company.

1.2 Scope

Assisted Direct Start is the system to be developed. It is to be an automotive system with the end goal of reducing fuel usage by turning the engine off when it is not needed. The Assisted Direct Start system (ADS) will monitor inputs from necessary car systems in order to determine if it is able to turn the engine off. The primary function of the ADS is to gather that information from those systems and turn the engine off, if possible. If the gathered data indicates the engine needs to be on, the ADS will activate the Ford quick start technology that will allow the engine to be restarted with no noticeable lag time for the driver.

1.3 Definitions, acronyms, and abbreviations

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)

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ADS - Assisted Direct Startmph - miles per hourGPS - Global Positioning SystemUML - Unified Modeling Language

1.4 Organization

The next section of this document, titled Overall Description, will provide an overview of how the ADS system will be integrated with existing vehicle components and how this system will provide new functionality. This section will also discuss assumptions regarding the target users and will summarize all constraints and assumptions used to create the technical requirements further in the document.

The third section, titled Requirements Specification, provides an enumerated, hierarchical list of all of the technical requirements of the system.

The fourth section, Model Requirements, will show the connection between the application and machine domains. It will include several diagrams, including use-case diagrams, a high-level class diagram, and state diagrams. The Model Requirements section will also include several scenario descriptions to accompany each state diagram.

The fifth section, Prototype, will provide information regarding the existing prototypes of the system, including instructions on how to access and run the prototypes and sample scenarios of system use.

The sixth section will provide a list of all sources used in preparing this document, and the seventh section will provide a point of contact for any further information regarding the project.

2 Overall Description

This section gives an overview of how the ADS system fits with existing hardware and software components found in a vehicle, as well as the functionality given by the ADS system. Expected characteristics of the system’s users are provided, as well as information about known constraints that could affect safety or system function. In addition, this section gives all important assumptions that were made in the creation of this system.

2.1 Product Perspective

The ADS system will use readings from the user’s vehicle such as fuel levels, battery levels, engine temperature, and speedometer reading. These readings are already being gathered by the vehicle’s system according to our Ford contact. The ADS system will monitor these readings and use them to decide if the engine should be shut off or turned on in order to save fuel.

The ADS system is a subsystem that fits in with the other software components in 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)

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a vehicle. It acts independently by monitoring various states of the vehicle and using that information to preserve fuel by turning the engine on and off. The ADS receives information about the states of other systems and components in the vehicle, and this information is used to determine the ADS system’s behavior.

There are no strict memory constraints for the system. It is pulling information that is already being monitored by the vehicle and is using that information to turn off the engine, if all the readings verify that the engine is not currently needed. Operationally, the engine temperature needs to be above 200 degrees Fahrenheit in order for a quick engine start to be performed by the ADS. The driver can choose to manually disable ADS via a button on the dashboard. There are no plans for on-site customization. Figure 1 below shows a data flow diagram of the ADS and the surrounding systems with which it interacts.

Figure 1. Data Flow Diagram

This data flow diagram shows how the ADS system fits in with the rest of the systems in the vehicle and indicates the flow of information to and from the ADS. Arrows from another system to the ADS system indicate a flow of information into the ADS system, and arrows from the ADS system to another system indicate a flow of


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information out of the ADS system.The fuel tank provides the ADS system with the current remaining fuel, which

becomes important information as the fuel tank gets close to empty. In one mode of operation, the ADS system will disable user comforts such as music and air conditioning in order to maximize fuel economy.

The engine provides the ADS system with the engine temperature so that the ADS can decide whether the engine is warm enough to allow the quick start feature which is the primary function of ADS. The engine and ADS system communicate about the state of the engine (on or off) as ADS will turn the engine on and off depending on the information it is receiving from other systems.

The vehicle’s ignition will have a key state that is provided to the ADS. The presence of a key in the ignition will allow the ADS to be enabled if other conditions are met, such as the engine temperature.

The battery provides the ADS the amount of remaining energy, in percentage of full, so that the ADS can determine whether there is enough battery to turn the engine on or off while sustaining battery-operated comforts such as windshield wipers, air conditioning, and power operated windows.

The driver can choose to enable or disable the ADS system by pushing a button on the dashboard. In this way, the driver sends information to the the ADS system.

The dashboard indicator receives information about the enabled/disabled state of the ADS system and displays the current state for the driver.

The speedometer sends the ADS system information about the vehicle’s current speed, which the ADS uses in order to determine whether the engine can be turned off.

The seat force monitor sends the ADS information about the amount of weight currently in the driver seat. If there is not enough weight on the driver’s seat to verify that an adult is seated, the ADS will not turn the engine on.

2.2 Product Functions

The main goal of the ADS system will be to turn off the engine when it is not needed in order to save fuel. This function is utilized when the vehicle is approaching a stop, as in the case of traffic or a red light. The ADS system will then restart the engine when it is needed to accelerate the vehicle, provide heat to the cabin, or charge the battery. Because the ADS system may remain enabled when the engine is turned off, there is a risk that the driver will leave the vehicle while the ADS is still running. In order to prevent dangerous situations caused by this confusion, the ADS system will disable itself when the car is switched into park gear. There will also be a button on the dashboard that will allow the driver to manually enable and disable the ADS system if desired.

The goals of the system are as follows:

1) Increase fuel economy by minimizing unnecessary engine idle time (primary)2) Ensure safety for the driver and passengers of the vehicle (primary)3) Ensure that functionality of the vehicle is not hindered by the ADS (primary)


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4) Allow driver input to maximize user comfort and convenience (secondary)

A primary goal is one that is crucial to the the operation of the system- without it, the ADS system would be pointless or counterproductive. A secondary goal is one which is a convenient addition to the system’s design, but which is not essential to its functionality. Figure 2 below shows a goal diagram indicating the four goals and the most important ADS functions which are used to achieve them.

Figure 2. Goal Diagram

2.3 User Characteristics

The user of our system will be a driver who is not expected to have any skill or expertise related to control of the ADS system. Because the ADS system is able to function without any direct input from the user, it is possible that the driver will actually be unaware that it exists. Because users are untrained about the ADS system’s functionality, all user input will be made as simple as possible.

Because constant stopping and starting of the engine may become annoying to the user during heavy traffic or parking lot scenarios, the user will be able to disable the ADS system, meaning that the ADS system will no longer turn off and restart the engine. The user will also be able to enable the system to resume its functionality.

The only user interface feature that will be necessary to control the ADS itself is a single button located in the dashboard area that will allow the user to disable or enable the ADS system. In addition to this button, the dashboard will contain a button which switches the mode between “fuel economy” and “driver comfort.” Addtional buttons will allow a temperature to be set for climate control, and a final button will enable or disable a “customer annoyance avoidance” system.

2.4 Constraints

The ADS system will be integrated with existing hardware and software systems present within Ford vehicles. The following information must be given to the ADS


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system by existing vehicle features for proper functionality:

1) The state of the brake pedal and gas pedal will be provided by sensors or associated software.2) The current gas and battery levels will be provided by sensors or associated software.3) The current vehicle speed will be provided by either the speedometer or a GPS system.4) The engine temperature will be provided by the engine or associated software.5) The key state of the vehicle’s ignition will be provided by the vehicle ignition system.6) The force on the driver seat will be provided by a seat force sensor.

Because this system is only activated when the vehicle is at rest or is coming to a stop, it has very few safety-critical properties. The main danger would involve a user mistakenly leaving the vehicle at a time when the motor is shut off but the ADS system is still active. In this case, it is possible that another driver or even a child could start the engine. In order to avoid this scenario, the following features will be included:

1) When the car is shifted into the ‘park’ gear, the engine will be turned on to remind the driver that the ADS system is still active.2) A key will be used in the ignition to make it less likely that a user would forget to shut off the car completely.3) a seat force sensor will ensure that the engine will not restart when an adult is not in the driver seat.

The ADS system should also be informed of failures in the following vehicle components. These failures should be detected by existing hardware and software.

1) brake pedal2) gas pedal

If the brake pedal is diagnosed as failed, the ADS system will continue unaffected under our current design. If the gas pedal is diagnosed as failed then the engine will be turned on and the ADS system will be disabled.

2.5 Assumptions and Dependencies

It is assumed that the ADS software will be added to a fully-functioning vehicle as an enhancement, rather than as a necessary system. For a list of vehicle components that provide input to the ADS system, see Section 2.4 above. The only vehicle component that must direct input from the ADS system is the engine.

In addition to the previously stated vehicle components, the ADS system depends on proprietary Ford technology that allows the motor to be started more quickly than normal. The known properties of this technology as provided by Ford are:


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1) An engine temperature of at least 200 degrees Fahrenheit is necessary to start the engine in this way.2) The engine can be started in less than half a second.3) Certain conditions, such as heavy cargo loads on the vehicle, may cause a more noticeable delay when the engine starts (exact loads are unknown.) In this event, the user may wish to disable the ADS system, and therefore a user interface should be present.4) The vehicle’s battery must have sufficient charge to restart the engine- 5% of the battery’s total charge is required.5) No fuel is used in order to turn off or restart the engine.

2.6 Approportioning of Requirements

Currently there are no known requirements that are outside the scope of the project. However, a possible enhancement to the system would involve the use of the vehicle’s GPS system to predict times when the engine should be restarted after a stop. If the system is able to predict times when the engine must be started in this way, it could eliminate all delay associated with starting the engine. This may give a more seamless feel to the ADS operation and a more pleasant experience for the driver.

Predicting the start of the engine could be accomplished by using the GPS to monitor the surrounding traffic patterns while the user’s vehicle is stopped. For example, the engine could be restarted when the vehicle directly in front of the user’s vehicle begins to accelerate from a stop. It is likely that the user’s vehicle will need to accelerate as well.

3 Specific Requirements

This section lays out the exact requirements and functionality that the ADS system will deliver

1) The proposed system will include a software package referred to as the ADS system and a hardware user interface which allows the driver to interact with the ADS system.

2) The ADS system may be either enabled or disabled. Enabled means that the ADS system may turn the engine on and off. Disabled means that the ADS may not turn the engine on and off.

3) The user interface will include the following features:3.1) Displays the current state of the ADS system (enabled/disabled)3.2) Includes a toggle button which the driver can press. This button will affect the enabled/disabled state of the ADS system.3.3) Includes a climate control panel which allows the driver to interact with the climate control subsystem, including enabling or disabling the subsystem.3.4) Includes a mode select button which allows the driver to switch between driver comfort mode and fuel economy mode.


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3.5) Includes an annoyance detection button which enables or disables a “customer annoyance avoidance” system.

5) When the vehicle is started (when the key is inserted into the ignition) or when the vehicle is in the park gear:

5.1) The engine will be turned on.5.2) The ADS system be disabled.

6) If the key is in the ignition and the car is in the drive or reverse gear, the ADS becomes enabled or disabled as follows:

6.1) If the the ADS system is disabled, it will become enabled if all of the following conditions are true:

6.1.1) The engine temperature is greater than or equal to 200 degrees.6.1.2) The driver presses the toggle button.

6.2) The ADS system will also become enabled automatically the first time the engine becomes greater than or equal to 200 degrees.6.3) If the ADS system is enabled, it will become disabled if at least one of the following conditions is true:

6.2.1) The engine temperature is less than 200 degrees.6.2.2) the driver presses the toggle button.

7) If (and only if) the ADS system is enabled, it will interact with the engine according to the following rules:

7.1) If the engine is currently on, it will be turned off if all of the following conditions are true:

7.1.1) The accelerator pedal is not being pressed.7.1.2) The vehicle speed is less than or equal to 2.5 mph.7.1.3) The vehicle speed is greater than 0 mph (this ensures that the engine will be unaffected if the ADS becomes enabled during a stop.)7.1.4) The battery level is greater than 20% (this ensures that there is enough battery power left to turn the engine back on.)

7.2) If the engine is currently off, it will be turned on if the key is in the ignition, the seat force monitor in the driver’s seat reads at least 75 pounds, and one of the following conditions is true:

7.2.1) The gas pedal is pressed.7.2.2) The battery level is less than or equal to 10% (any lower and the battery may die when the engine is turned on.)7.2.3) The ADS system becomes disabled.

8) When the key is removed from the ignition or the fuel level equals zero:8.1) The engine will be turned off.8.2) The ADS system will be disabled.

9) If the climate control subsystem is enabled on the user interface, it will behave as follows:

9.1) Temperature set buttons on the user interface will allow the driver to set a


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desired temperature for the car’s interior.9.2) If the current temperature in the car is less than the desired temperature, the heat will be turned down.9.3) If the current temperature in the car is greater than the desired temperature, the heat will be turned up.

10) If the driver comfort mode is selected on the user interface (this is the standard mode):

10.1) All electronic components will remain enabled when the engine is turned off.

10.2) If the battery level is less than or equal to 10%, the engine will restart.

11) If the fuel economy mode is selected on the user interface:11.1) The following electronic components will be disabled when the engine is turned off: air conditioning and music players.11.2) The following electronic components will always remain enabled to ensure safety: windshield wipers, internal and external vehicle lights, window operation, power steering, dashboard indicator lights.11.3) If the battery level is less than or equal to 10%, the engine will restart.

12) If the “customer annoyance avoidance” system is enabled on the user interface, it will behave as follows:

12.1) If the engine is turned off by the ADS more than 3 times in a 20 second period, the ADS system will be disabled.12.2) At the time the ADS system is disabled, a tone will sound to alert the driver.

4 Modeling Requirements

Use Case Diagram:

Use case diagrams are used to show the primary functions of the system, referred to as use cases, and the external actors which affect them. The large box represents the bounds of the system, and each oval inside the box represents a use case. The stick figures outside the box represent external actors which provide input into the system. A line between an actor and a use case indicates that the actor plays some role in that use case, and a line between two use cases indicates that they affect each other.

A special type of connection that is shown is the dashed line labeled <<Include>>. The include line goes from a use case to another use case which it will always trigger. As an example, the “turn engine on” use case is always triggered when the “disable system” use case is run. Each use case accomplishes or assists in at least one of the goals of the system. Figure 3 below shows a use case diagram for the ADS system.

As shown in section 2.2, the goals of the ADS system are as follows:

1) Increase fuel economy by minimizing unnecessary engine idle time (primary)


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2) Ensure safety for the driver and passengers of the vehicle (primary)3) Ensure that functionality of the vehicle is not hindered by the ADS (primary)4) Allow driver input to maximize user comfort and convenience (secondary)

Figure 3. Use case diagram

Use Case: display ADS stateActors: dashboard indicatorDescription: The current state of the ADS system (enabled/disabled) will be displayed for the driver. The state of the system is changed when the system is either enabled or disabled.Type: SecondaryIncludes: NoneExtends: NoneCross-references: 1 (goal #4)Use cases: enable system, disable system Use Case: enable systemActors: driver, engine temperatureDescription: Enabling the ADS system will make it able to turn the engine off and on. The ADS system will always be disabled when the car is first turned on. The system will be enabled for the first time when the engine temperature reaches a specified value necessary for the ADS to stop or start the engine. If the temperature is sufficient, the driver can disable and enable the ADS system by pressing a button.Type: Primary


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Includes: display ADS stateExtends: NoneCross-references: 1 (goal #1)Use cases: turn engine on, turn engine off Use Case: disable systemActors: driver, engine temperature, fuelDescription: Disabling the ADS system will make it unable to turn the engine off and on. Before the ADS system is disabled, the engine must be turned on or the driver will be unable to start the engine- this will be handled automatically. The system will be disabled if the driver presses a button or if the fuel runs out, and also if the engine temperature gets too low for an engine restart.Type: PrimaryIncludes: display engine state, turn engine onExtends: NoneCross-references: 3 (goals #2,3,4)Use cases: None Use Case: turn engine onActors: driver, seat force monitor, batteryDescription: When the ADS system is enabled but the engine is off, the engine will be turned on if the driver pushes the gas pedal or when the battery gets dangerously low and must be recharged by the engine. This event will also be triggered when the ADS system is disabled. For safety, turning on the engine requires that the force of an adult driver is in the seat.Type: PrimaryIncludes: NoneExtends: NoneCross-references: 1 (goal #3)Use cases: enable system, disable system Use Case: turn engine offActors: speedometer/GPS, batteryDescription: When the ADS system is enabled and the engine is on, the engine will be turned off if the speed of the vehicle drops below 2.5 mph and the vehicle is decelerating- these conditions indicate that the vehicle is about to stop. The engine will only be shut off if there is at least 20% battery power remaining.Type: PrimaryIncludes: NoneExtends: NoneCross-references: 1 (goal #1)Use cases: enable system

Class Diagram:


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A class diagram shows all classes within a system and the connections between them. Each box represents a class, and the lines between classes indicate connections such that data can be shared. An arrow head on a connection indicates that the class sending the arrow is derived from the class which receives the arrow. The derived class has all the functionality of the parent class, but also includes unique functionality. A diamond head on a connection indicates composition, meaning that the class which receives the diamond is composed of the classes which send the diamond. Each box also lists every attribute and every operation of the class. Figure 4 below shows the class diagram for the ADS system.

Figure 4. Class diagram

Classes:

Pedal: a foot pedal in the driver’s seat.Attributes: isPressed: boolean value indicating whether the pedal is currently being pressed.Operations: getIsPressed: returns the value of isPressed.

Brake Pedal: the driver’s brake pedal. Inherits from Pedal.Operations: decelerate: reduces the speed of the car. Returns nothing.

Gas Pedal : the driver’s gas pedal. Inherits from Pedal.Operations: accelerate: increases the speed of the car. Returns nothing.

Gas Tank : The car’s gas tank.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)

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Attributes: gasLevel: the gas level in gallons.Operations: getGasLevel: returns the value of gasLevel.

Dashboard: contains and controls Dashboard Indicators and Dashboard Controls.

Dashboard Indicator: an indicator light on the dashboard.Attributes: isEnabled: boolean value indicating whether or not this indicator is turned on.Operations: setIsEnabled: sets the value of isEnabled to parameter enabled.

Dashboard Control: a control on the dashboard.Attributes: isPressed: boolean value indicating if this control is pressed.Operations: press: take action based on pressing this control.

getIsPressed: returns the value of isPressed.

Ignition : The car’s ignition, where the key is inserted or removedAttributes: keyIsIn: boolean value indicating whether the key is currently in the ignitionOperations: keyIn: called when the key is inserted into the ignition. Turns on the engine.

keyOut: called when the key is removed from the ignition. Turns off the engine and disables the ADSgetKeyIsIn: returns the value of keyIsIn

Engine: The car’s engine.Attributes: turnedOn: boolean value indicating if the engine is on.

temperatureFarenheit: temperature of the coolant in degrees Farenheit.Operations: getTurnedOn: returns the value of turnedOn.

getTemperatureFarenheit: returns the value of temperatureFarenheit. setTurnedOn: sets the value of turnedOn to parameter state

Gear Shift: The engine’s gear shift.Attributes: currentGear: the gear the engine is currently set to: “park,” “drive,”or

“reverse” Operations: getCurrentGear: returns the value of currentGear.

changeGear: sets the value of currentGear to parameter gear.

GPS System : The GPS system of the car.Attributes: longitude: the longitude value observed by the GPS system.

latitude: the latitude value observed by the GPS system.Operations: getLongitude: returns the value of longitude.

getLatitude: returns the value of latitude.

Speedometer: The car’s speedometer.Attributes: milesPerHour: the car’s current speed in miles per hour.Operations: getMilesPerHour: returns the value of milesPerHour

Battery: The car’s battery.Attributes: percentCharged: percentage of maximum charge currently held by the battery


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in range [0.0,100.0] as a floating point number.Operations: getPercentCharged: returns the value of getPercentCharged

Seat Force Monitor: the force monitor in each seat.Attributes: forcePounds: the force currently read by this seat force monitor in pounds.Operations: getForcePounds: return the value of forcePounds

ADS: the ADS systemAttributes: enabled: boolean value indicating if the ADS system is currently enabled.Operations: performReadings: reads the values of the other subsystems (battery level,

seat force, speed, etc.) and enables/disables the ADS system based on their values, based on the requirements of the system.TurnEngineOnOrOff: calls setTurnedOn in the engine class and sets the engine on or off based on the current values of variablesSetEnabled: sets the enabled state of the ADS to the parameter state

System State Diagrams:

State diagrams show the transitions between states of the system. An example of a state might be “engine on” or “engine off.” The black circle indicates the transition to the system’s initial state. From there, there are arrows directing the transition to new states. The text above the arrow indicates the condition that triggers the transition to the new state. Figure 5 below shows an overall state diagram for the ADS system.

Figure 5. Overall state diagram

This diagram shows the state of the system in terms of the two key variables: the on/off state of the engine and the enabled/disabled state of the ADS system. The system reaches its initial state when the driver puts the key in the ignition- this action turns the 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)

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engine on, but does not enable the ADS system. This is because the ADS system requires an engine temperature of 200 degrees Fahrenheit to trigger a quick stop or start of the engine.

When the engine temperature reaches 200 degrees Farenheit, the ADS system will be enabled for the first time. From this state, the engine will be automatically turned off by the ADS system if the speed of the vehicle drops below 2.5 mph while the vehicle is not accelerating. The engine will only be turned off if there is sufficient battery power remaining to turn the motor back on, and the motor will not turn off if the vehicle was already at a stop at the time the ADS system was enabled.

If the engine is off, it will be turned on if the driver presses the gas pedal or if the battery power falls below 10%. If the engine temperature falls below 200 degrees while the engine is turned off, the engine will be turned back on and the ADS system will be disabled so that the engine will not turn off immediately. This allows the engine to warm up again.

When the ADS system is running, the driver can press a button located on the dashboard to disable the ADS system (and turn the motor back on if it is currently off.) Pressing the button again will enable the system once more.

If at any time the key is removed from the ignition or the gas level reaches zero gallons, the engine will turn off and the ADS system will be disabled. The vehicle is completely shut off at this point.

Figure 6 below shows a state diagram for the engine alone, and Figure 7 shows a state diagram for the ADS alone.

Figure 6. Engine state diagram

This state diagram shows the transition between engine states. When the vehicle is moving at a speed less than or equal to 2.5 miles per hour, if the battery is more than 20% charged, the engine will be turned off. The engine will also be turned off if the key is removed from the ignition.

If the key is in the ignition, the engine will be turned back on if the gas pedal is engaged or if the battery’s charge is less than 10%. if the key has been removed from the


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ignition, the engine can be turned back on by reinserting the key into the ignition, as long as the seat force monitor in the driver’s seat is currently reading more than 75 pounds.

Figure 7. ADS state diagram

This state diagram shows the transition between the ADS system being enabled and disabled. If the engine temperature is greater than or equal to 200 degrees, the seat force monitor in the driver’s seat is reading at least 75 pounds, and the battery is more than 20% charged, the ADS system will be enabled. If any of these conditions is false, the vehicle runs out of fuel, or the key is removed from the ignition, the ADS system will be disabled.

Sequence Diagrams:

Sequence diagrams are used to show interactions between objects in specific scenarios. The stick figures, called “actors” indicate a component of the system (ADS, engine, gas tank, etc.). Please note that there is one actor labeled “Actor” which is the class that calls the function being focused on. The details of who is calling these methods are not important in these diagrams; the focus is on the flow of control for specific scenarios.

There are two kinds of arrows.The solid black arrow indicates control transfer, typically a function call. The dotted arrows indicate returning control. The label on the black arrows is the name of the function being called, and the label on the dotted arrows indicates the return value.

Finally, there are boxes labeled as “alt.” These indicate an if-else relationship - that is, if the condition in the square brackets is true, the calls and returns in that box would be executed. If the condition is false, that portion of calls and returns would not be executed.

In order to explain the behavior of the system, several sequences of events are shown. The first sequence shows the events called during the performReadings function in the ADS class, and the second sequence shows the events called during the turnEngineOnOrOff function in the ADS class.

Sequence 1Template 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)

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performReadings - This function will be called every 0.025 seconds to determine if the ADS needs to be disabled/enabled. It gets the engine’s temperature (in degrees Farenheit), the gas tank level in gallons, and the battery’s charge percentage.

If the temperature is greater than 200 degrees Farenheit, the gas tank is not empty, and the battery is more than 20% charged, ADS is enabled, if any of these conditions is not true, ADS is disabled. If ADS is disabled, an indicator on the dashboard will be turned on to let the user know the ADS functionality is not currently available. If ADS is enabled, the indicator will be turned off. This sequence is shown in Figure 8 below.

Figure 8. Sequence 1: performReadings

Sequence 2

turnEngineOnOrOff - This function will be called every 0.025 seconds, if the ADS system is enabled, to determine whether the engine should be turned on or off. It will retrieve the speed (in miles per hour) read by the speedometer, the battery’s charge percentage, the weight (in pounds) from the seat force monitor in the driver’s seat, and detect whether or not the gas pedal is engaged.

If the gas pedal is engaged and the key is in the ignition, the engine will be turned on, regardless of the other conditions, as this indicates that the driver is attempting to accelerate. Otherwise, the system will check the car’s current speed, battery, and the force in the seat. If the vehicle is moving at a speed less than or equal to 2.5 miles per hour, and 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)

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the battery has charge greater than 20%, the engine will be turned off. If the speed is greater than 2.5 miles per hour or the charge of the battery is less than 10%, and the seat force monitor detects a weight greater than or equal to 75 pounds in the driver’s seat, the engine will be turned on. This sequence is shown in Figure 9 below.

Figure 9. Sequence 2: turnEngineOnOrOff

5 Prototype

Figure 10 below shows the layout of the prototype, version 1. The prototype will be made using Adobe Flash. It will include a two-dimensional driving simulation with buttons that allow user interaction. The user will be able to push the gas pedal to accelerate and the brake pedal to decelerate. Animations on the screen will give visual feedback about the current speed of the car, and a large panel on the right side of the screen will display the current status and values of these variables:

1) fuel remaining in gallons

2) battery remaining as a percentage of maximum charge

3) velocity in miles per hourTemplate 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)

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4) engine temperature in degrees Fahrenheit

5) the status of the engine- on or off

6) the status of the ADS system- on (enabled) or off (disabled)

The prototype will display all aspects of the ADS system’s functionality. All requirements specified in Section 3 above will be carried out by the prototype so that they can be tested.

Figure 10. Simulation Layout

5.1 How to Run Prototype

The prototype is a Shockwave Flash video file, or an SWF. In order to run the prototype, it is necessary to have Adobe Shockwave Player installed on your computer (any version should work.) Prototype version 1 can be found at the following URL:

http://www.cse.msu.edu/~cse435/Projects/F2013/Groups/ADS/web/prototype.html

5.2 Sample Scenarios

In order to demonstrate the behavior of the system, several sample scenarios will be described with screenshots and descriptions of how the prototype responds. The first scenario will demonstrate the typical functionality of the ADS system during normal conditions.


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scenario 1- standard operation

When the prototype is run, the car will begin with both the engine and the ADS system in the “off” position. At this point, the temperature of the engine is stable at 60 degrees Fahrenheit- the temperature outside the vehicle. The gas starts at 10 gallons, and the battery is fully charged at 100 %. A key appears over the user’s mouse, and a flashing red light comes from the ignition located on the side of the steering wheel. The flashing light indicates that the key should be moved to this spot on the screen, as shown in Figure 11 below.

Figure 11. Starting the prototype

When the key is dragged over the ignition, the car will start- this means that the engine will switch to “on.” Immediately the engine temperature will begin to rise- the engine temperature will rise continuously while the engine is “on” until a temperature of 250 degrees is reached. Turning the engine on also took a portion of the battery power- 5% is removed, but the battery will automatically recharge when the engine is turned on. Because the engine temperature is not above the required 200 degrees yet, the ADS system remains off, as shown in Figure 12.


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Figure 12. Immediately after the engine is started

For this scenario, we will first wait for the engine to warm up sufficiently. The fuel will steadily decrease over time when the engine is turned on. When the engine temperature reaches 200 degrees, the ADS system switches to “on.” The car is not moving, but the ADS system will not turn off the engine because the car was already at a stop at the time the ADS system was enabled. the current state is shown in Figure 13.

Figure 13. The engine temperature gets high enough to turn on the ADS system

If we now press the accelerator pedal inside the vehicle, the car’s velocity will increase. The fuel also drains faster during the acceleration. We accelerate up to 10 mph and then release the accelerator pedal. The current state is shown in Figure 14.


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Figure 14. The car is accelerated up to 10 mph

The car’s velocity will naturally decrease when the accelerator pedal is not pressed. When the velocity reaches 2.5 mph, the ADS system will cause the engine to turn off, as shown in Figure 15. Turning off the engine requires 5% of the vehicle’s battery.

Figure 15. The car decelerates below 2.5 mph and the ADS system turns off the motor

Later scenarios will be shown when more of the prototype is developed.

6 References


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ADS team website:http://cse.msu.edu/~keifcame/

Assisted Direct Start Project description:http://cse.msu.edu/~keifcame/cse435/ads_2013.pdf

7 Point of ContactFor 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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Documents

SRS for Team ADS.docx - Michigan State Universitycse435/Projects/F2013/Groups/ADS/Docs... · Web viewIt is to be an automotive system with the end goal of reducing fuel usage by turning