DVA455: Software Development
for Real-Time Systems
Reverse Parking Assistance
Airbag Control System
Students:
Date:
Michael Hunter
2022-04-13
Assignment 1: Requirements and High-Level Design
1. Introduction
Reverse Parking Assistance – Assists the driver of a vehicle when they are
reversing their vehicle. This system works by giving the driver a view of
the vehicle’s blind spot. Most systems use a beeping sensor to
communicate to the driver when they are approaching an object whilst
reversing or the use of a screen to allow to driver to have a wider range of
sight whilst reversing. With a reverse parking assistance installed in a car
this greatly reduces the likelihood of an accident occurring whilst
reversing a vehicle.
Airbag Control System - Detects and assesses the severity of an accident
before activating the necessary restraining systems. This includes
accelerometers and a rotating speed sensor. If a vehicle crash was to occur
signals would be sent airbag control system. Hazard lights and interior
lights are then activated whilst the fuel pump and vehicle engine are
simultaneously turned off.
2. System Architecture
Reverse Parking Assistance – This consist of parking sensors, a controller, back-up
alarm beeper, and the communication between them by wire harness. The connections
between the parking sensors and controller are based on a wire harness, and each of
the parking sensors is separate from one another meaning that, if one of parking sensors
were to be damaged, it would not affect the others.
The parking sensors detect the distance between the vehicle and the obstacle, and
when the distance reaches the alarm valve, the controller controls the back-up alarm
beeper. Generally, the back-up alarm beeper is integrated inside the controller, or
installed in the vehicle separately, connected to controller by the wire harness. If the
vehicle is equipped with displayer, it can show the distance from vehicle to obstacle.
Airbag Control System – This consists of high-powered microcontrollers that take the
data from the satellite and side impact sensors to indicate whether the air bags need to
be deployed. When an impact occurs either the impact sensor or safety sensor close
which activates the airbag through the electrical transmission between two metal pins.
If a vehicle is a newer model, it may also have a rollover sensor which has increased
precision when a crash occurs compared to older vehicle models which offer a more
mechanical airbag sensor.
a. Sensors
The system will make use of the following sensors:
Reverse Parking Assistance
Sensor 1: Alarm Beeper
An alarm that gets louder depending on how close the vehicle is to
an object. Located in the compartment above the pedals. It should
also have a led flashing on the dashboard for drivers with hearing
difficulties that flashes more frequently when getting closer to an
object.
Sensor 2: Parking Sensor
A sensor that uses geolocation or satellite imaging to guide the
driver whilst navigating or parking the vehicle. Located in the
vehicle’s bumpers. If a collision occurred, the sensor would work
with the alarm beeper to alert the driver of the collision.
Airbag Control System
Sensor 1: Impact Sensor
An impact sensor determines whether the vehicle has collided with
an object. If a collision occurs the airbag is deployed.
Sensor 2: Safety Sensor
A safety sensor works along with the impact sensor to activate the
airbags when a collsion has occured. If the airbags have been
deployed a notification or distress signal should be sent to the local
emergency services.
b. Actuators
The system will make use of the following actuators.
Reverse Parking Assistance
Actuator 1: Parking Sensor
A sensor that uses satellite imaging to detect how far a driver is from an
object. This would be in the bumper of the vehicle one on each side of the
bumper and one in the middle leading the 3 actuators in total.
Airbag Control System
Actuator 1: Airbag System
A nylon fabric that is inflated by nitrogen when a collision has
occurred. This is to reduce injury to the driver and passengers in the
vehicle. These are in the steering wheel, the front dashboard, and
the side doors in the back of the vehicle. This leads to 4 actuators.
3. Functional- and Timing Requirements
Reverse Parking Assitance
FR 1: When the vehicle is reversing, the parking sensor should notify the driver
how close they are to an object.
The parking sensors are 0.75 meters from the object whilst reversing. This then
forces the sensor to notify the driver that they are about to hit something and
should steer around the object.
Stimulus: The driver is about to hit something.
Response: Drive forward whilst also steering right or left.
Additional information needed: Use the display screen if the vehicle has one.
TR 1.1: When the vehicles approach an object while driving in reverse, the
sensor should increase speed and volume every 0.1 second.
FR 2: When the vehicle approaches an object while driving in reverse, the
brakes should be applied.
The parking sensors are 0.3 meters from the object whilst reversing. This then
forces the driver to change to clutch to drive from reverse to drive.
Stimulus: The driver is about to hit something.
Response: Drive forward whilst also steering right or left.
Additional information needed: Use the display screen if the vehicle has one.
TR 2.1: When the vehicles approach an object while driving in reverse, the
brakes should be applied within 1 second.
Airbag Control System
FR 1: When the vehicle collides with an object, the airbag control system should
deploy.
Stimulus: The driver has collided with an object.
Response: Deploy the airbag control system so you can reduce injury.
TR 1.1: When the vehicle collides with an object, the airbag control system
should deploy, within 0.5 seconds.
4. High-level Software Design
Reverse Parking Assistance
Task 1: Object Detection
Inputs: Parking sensors
Outputs: Alarm beeper
Description: As a driver is reversing satellite imaging detects how far the
driver is from and object. Once the driver is 1 meter from an object the
parking sensors indicate this to the alarm which then emits a noise to alert
the driver of this. As the driver gets closer to the object the alarm gets
louder and more frequent. Once the driver is 0.3 meters the parking
sensors stop the driver from reversing further. This results in the driver
not colliding with the object.
Task 2: Object Collision
Inputs: Control box
Outputs: Airbag control system deployment
Description: If the driver collides with an object the control box sends a
signal to the airbag control system within 0.1 seconds, this will then
activate the airbags protecting the driver and reducing injuries.
Airbag Control System
Task 1: Protecting People
Inputs: Impact Sensor
Outputs: Deployment of airbag control system
Description: When a vehicle collides with an object the impact sensors
activate the metals pins that keep an electrical circuit closed. This then
allows a nylon airbag to inflate due to nitrogen gas to protect both the
driver of the vehicle but also any passengers that are in the vehicle.
Task 2: Emergency Services
Inputs: Impact Sensor, Satellite Sensor
Outputs: Emergency services dispatched
Description: When a vehicle collides with an object the impact sensors
activate the metals pins that keep an electrical circuit closed. This then
allows a nylon airbag to inflate due to nitrogen gas to protect both the
driver of the vehicle but also any passengers that are in the vehicle. The
satellite sensors in combination with the impact sensors contact the
emergency services for the country that the vehicle is in and informs the
dispatcher of the location using gps location.
Assignment 2: Timing Parameter Assignment and
Schedulability Analysis
1. Real-time Task Parameters
Reverse Parking Assistance
Task
T1
Task name
Object Detection
WCET Period Deadline Precedes
2
0.5
1.5
T2
Motivation for the task parameters: When the driver is reversing, they want to
know if an object is within a proximity so that they can maneuver around it. If
a collision were to occur the vehicle and the driver are injured. The driver
wants to reduce this happening as medical bills may have to be paid if a
collision occurred and the driver’s insurance will be affected due to the
vehicle being damaged.
As the driver is reversing, they want to be notified by the parking sensors
every 0.1 seconds so that the driver can make the decision whether they need
to change gears and drive forward to maneuver around the object. If the
WCET occurs that can greatly affect the driver due to the driver normally
taking 1 second to react to seeing the object and changing the gear stick.
Airbag Control System
Task
T1
Task name
WCET Period Deadline Precedes
Protecting People 5
0.5
10
T2
Motivation for the task parameters: When a collision occurs the vehicle if
designed correctly should deploy airbags to reduce injury to the driver and
passenger.
As the driver collides with an object the metal pins that keep the nylon airbag
from inflating should break the circuit within 0.5 of the impact sensors
colliding with the object. The WCET occurring increases the likelihood of the
driver and possible passengers from receiving greater injuries, thus once the
airbags are deployed the satellite sensors need to contact the emergency
services within 2 seconds.
2. Offline Scheduling
Reverse Parking Assistance
I treated this as if I was a driving instructor examining someone doing their
driver’s test. The object is within 0.75 meters of the parking sensor the WCET is
A and the driver reacting is B. The execution time between the object being 0.75
meters is 4 seconds due to the driver changing gears and maneuvering around
the object itself.
Schedulability test:
Verdict: The task set is offline schedulable.
Airbag Control System
I am a safety tester and rather than having the dummy system contact
dispatchers it is given a phone number that is in a silent room where another
person is timing the delay between each sensor activation. A is the impact
sensor, B is the airbag deploying and C is the phone being called by the satellite
sensor.
Schedulability test:
Verdict: The task set is offline schedulable.
3. FPS scheduling
Reverse Parking Assistance
I treated this as if I was a driving instructor examining someone doing their
driver’s test. The object is within 0.75 meters of the parking sensor the WCET is
A and the driver reacting is B. The execution time between the object being 0.75
meters is 4 seconds due to the driver changing gears and maneuvering around
the object itself. A has a higher priority over B.
Task
T1
Task name
Object Detection
WCET Period Deadline Priority
2
0.5
1.5
1
Schedulability test:
Verdict: The task set is FPS schedulable under the above priority assignment.
Airbag Control System
I am a safety tester and rather than having the dummy system contact
dispatchers it is given a phone number that is in a silent room where another
person is timing the delay between each sensor activation. A is the impact
sensor, B is the airbag deploying and C is the phone being called by the satellite
sensor. A has the highest priority then B and then C.
Task
T1
Task name
WCET Period Deadline Priority
Protecting People 5
0.5
10
1
Schedulability test:
Verdict: The task set is FPS schedulable under the above priority assignment.
4. EDF scheduling
Reverse Parking Assistance
I treated this as if I was a driving instructor examining someone doing their
driver’s test. The object is within 0.75 meters of the parking sensor the WCET is
A and the driver reacting is B. The execution time between the object being 0.75
meters is 4 seconds due to the driver changing gears and maneuvering around
the object itself. A has a higher priority over B.
Task
Task name
T1
Object Detection
WCET Period Adjusted
Deadline
2
0.5
1
Schedulability test:
Period A- 3 seconds
Period B- 3 seconds
Processing A- 1 second
Processing B- 1second
Verdict: The task set is EDF schedulable.
Airbag Control System
I am a safety tester and rather than having the dummy system contact
dispatchers it is given a phone number that is in a silent room where another
person is timing the delay between each sensor activation. A is the impact
sensor, B is the airbag deploying and C is the phone being called by the satellite
sensor. A has the highest priority then B and then C.
Task Task name
T1
WCET
Protecting People 5
Schedulability test:
Period A- 5 seconds
Period B- 9 seconds
Period C- 6.5 seconds
Processing A- 1 second
Processing B- 1second
Processing C- 3.5 seconds
Verdict: The task set is EDF schedulable.
Period
0.5
Adjusted
deadline
10
Assignment 3: Resource Sharing and Communication
(to be filled in after you get the question)
1. Shared resources
<Describe the shared resources.>
Task
WCET
Deadline
Period
T1
T2
Shared
Resource
<Resource 1>
<Resource 2>
None
Critical
section
3
5
Figure 1: Shared resources and length of critical sections
2. Communication
<Describe the architecture of the distributed system (how many nodes (ECUs),
how do they communicate and which sensors/actuators are connected to which
node.>
<Describe the allocation of tasks to hardware nodes and list the resulting
network communication in Figure 8.>
Task
WCET
Deadline
Period
T1
T2
Sends
Message To
T5
T6
None
Figure 2: Network communication
3. Holistic Schedulability Analysis
<Describe the schedulability analysis considering communication and resource
sharing.>
Verdict: The task set <is/is not> schedulable.
<If the task set is not schedulable, describe what can you do to make it
schedulable>
4. Dependability
<Describe the overall dependability concerns in your systems>
Threats: <Describe the identified threats to your system.>
Task criticality: <Motivate the tasks criticalities you have identified (you can
decide your own scale from non-critical to highly critical).>
Task
T1
Task name
ComputePosition
WCET Period Deadline Criticality
<High>
Figure 3: Task criticalities
Time and space redundancy: <Discuss the possibilities to use time or space
redundancy, and the resulting consequences.>