Car Safety System

Driving under alcohol remains a major cause of road accidents worldwide and in Belgium. This is a big issue nowadays and the objective of this project is to reduce car accident by preventing the driver to use his car . This project focuses on the development of a car safety system equipped with an alcohol detection mechanism, using a sensor attached to a box inserted on a steering wheel. The sensor detects the alcohol level in real time and block the hand-break mechanism if the alcohol level is too high..

The system is controlled by an Arduino microcontroller, which collect data from the sensor and controls relays to activate or deactivate solenoid.

Key considerations include ensuring the reliability and response time of the alcohol sensor, optimizing the design to withstand environmental factors within the vehicle, and maintaining smooth connectivity despite the steering wheel's motion.

1. Belt
2. 12V Relay
3. MQ3 Sensor
4. Solenoid x2
5. Arduino UNO
6. Leds x2
7. wires

Some of the components have to be manufactered, for this :

1. Lasercutter
2. 3D printer

1. Table of content
2. Project motivation
3. Project working modes/functionality/requirements
4. State of the art and patent analysis
5. Conceptual Design
6. High-Level Design / Embodiment design
7. Design of Sub-Systems
8. Mechanical Systems
9. Circuitry & Sensors
10. Software
11. Integration guide
12. Demo project show + Quick start guide
13. Review of the project
14. Sustainability
15. Bill of materials
16. Presentation of the team

The principal motivation of this project is, as said in the introduction, to reduce the car accident due to alcohol consommation. If someone has drank alcohol our system will allow him to drive depending of the level of alcohol the sensor measure. Nowadays, a lot of people still want to drive after having drank alcohol, thinking they are able while they aren't. That's why an alcohol safety system would make sure the driver can drive without causing trouble on the road.

1. Who is going to use our product?

Our product is for driver's personal use. The driver can go out and drink a little and be sure he/she can drive without having a risk of accident.

1. What or who interacts with our product?

The product will interact with the driver by telling him if he/she is able to drive and it's going to interact with the car, more particularly the handbreak, that is going to be blocked if the driver is not permitted to drive.

1. To which purpose this product has to be developed ?

The product has to be developed to reduce car accidents due to alcohol consummation and to ensure the driver's safety. It would make sure the driver is able to drive a car despite having had a bit to drink

For the alcohol car safety system to function effectively within the defined constraints, a functional analysis is essential. It is clear that for the project to meet expectations, certain constraints must be respected.

1. The system must accurately estimate the driver's alcohol level
2. The system should prevent the car from starting
3. It should also minimize user waiting time, enabling the driver to start the car quickly.
4. The system must be adaptable to different handbrakes
5. The system should be affordable

Less important considerations are also taken into account for the functional analysis.

1. Minimizing user distraction
2. Low power consumption
3. Sufficient user feedback

Everything is summarized on the requirement list above.

To ensure sustainability, the system incorporates Eco-Design principles such as using recycled or recyclable plastics for 3D-printed components, optimizing energy efficiency with low-power relays and a 12V supply, and adhering to RoHS standards for reduced hazardous materials. Its compact, modular design minimizes material use and simplifies disassembly for recycling or repair. On top of that, robust construction ensures a long lifecycle, reducing waste, while sustainable manufacturing processes further lower the environmental footprint.

Finally, the sensor would be integrated in a box that estimates the level of alcohol, if the level is too high, the handbreak is blocked with solenoid connected to relay, controlled by an Arduino, that go into a small hole from the 3D printed part of the blocking mechanism. This would ensure the driver can not pull the handbreak down and thus will not be able to drive.

State Of The Art:

Three alcohol safety systems were found already existing. They are respectively the DADSS, the Ignition Interlock Devices (IIDS)and the Wearable Technology(BACtrack).

The first detects passively the level of alcohol and prevents the car from starting if the level is too high. Concerning the IIDs, the driver has to blow into a device that tells him if he can drive. Finally, the Wearable Technology is is designed to measure the alcohol coming from the skin and then estimate the blood alcohol content.

Each of the systems is detailed on the table above with the advantages in green and the disadvantages in red.

Patent Analysis:

To check for patents, the website European Patent Office was used. After filtering the results concerning alcohol car safety systems, one solution in particular had similarities with our project. The solution's patent was the EP2263904B1: Alcohol interlock system with wireless data transmission and safety function.

The particular patent: an interlock system for a vehicle, the interlock system comprising;

An alcohol tester for measuring an alcohol level of a driver of the vehicle; a control device coupled with said alcohol tester for allowing starting of the vehicle or preventing the vehicle from being started depending on the measured alcohol level; and a transceiver module coupled with said control device for sending data to a remotely located control system in a wireless manner and for receiving data in a wireless manner, said transceiver module releasing said control device in response to data received in a wireless manner in order to allow starting of the vehicle regardless of an operating state of said control device.

The solution chosen to differ from the patent will be to act on the handbrake of the car; the system will block the brakes until it receives a signal from the alcohol tester when the alcohol level is below the legal limit.

First an abstraction has to be made to identify the essential problems. After describing the requirements specified in Step 3 as a foundation, the conceptual design seeks to pinpoint the critical problems and establish functional and operational frameworks. The process then focuses on developing and selecting the most viable concepts in this section.

The abstraction is the next: "a security electronic device responsible for measuring the driver's alcohol level, determining whether or not they are allowed to drive the vehicle".

Thanks to the requirement list and the abstraction made, the objectives can be quantified.

In order to address the problems, a set of actions that must be considered was found. Once the feature is known, a list of possible means to achieve them is made on the first image.

The same features affect different parts of the design, so they will be represented in separate tables. In each of them, different means will be provided to analyze the best option.

Mechanisms

First of all, the design of the component arrangement must be decided. To make the device easily adaptable, placed in a comfortable location, and of an acceptable size that is not intrusive, three possible solutions are proposed. In the first, the system would be embedded in the car's steering wheel. The second would be external to the car and mounted alongside the dashboard. The last option would be strapped to the steering wheel with straps. The image above shows the initial design ideas illustrating these possibilities.

Green color is used to highlight the best option for each feature.

Sensor

To be able to choose the appropriate sensor, the features related to it are taken into account. It can be seen that there is a clear winner on the table.

Blocking mechanism

When it comes to locking the handbrake to prevent the driver from driving, various combinations of mechanisms were proposed.

A piston with a motor that locks it in different positions, which would be attached to the handbrake. Also, a gear system with a rack and a gear. A passing bar through another, with a pin that locks them together. A bar clamping system inspired by an existing one on the market.

By seeking robustness but avoiding excessive complexity at the same time, the table above is obtained.

Some sketches of the concepts can be seen in picture.

Actuator

Once the locking mechanism system has been decided, the actuator that will activate it to make it function must be selected. Thank to the table can be seen that the solenoid is the best option.

After considering the best options from each of the previous tables and combining them, three possible final concepts are obtained.

The table comparing the concepts outlines the various potential approaches to achieving an effective design, based on the key problems analyzed earlier.

To be able to make a selection, a quantitative assessment is made by giving a weight to the different costraints. This way, the best concept can be chosen.

High-Level Design

On the first image above is the high level diagram, which describes how the system function.

Manufacturing process of the product

In the picture 2 to 5 above is also explained how the sensor box and the blocking mechanism would be manufactured. As it can be deduced, the sensor box would be manufactured by injection molding and the blocking by the powder methods.

Material selection

The selection material has been done on the Granta Edupack software and is divided in the two

subsystems.

Sensor box:

For the small sensor box, the price is the only thing that has to be minimized. By looking graphically on Granta Edupack on Picture 6 which is the price in function of the density, we can see materials like polymers are good solutions for the box to be built with.

Blocking mechanism:

The objectives for the mechanism are to minimize the mass and volume while supporting the known force applied on the handbrake.

It is supposed that all the pieces of the mechanism should be able to sustain the same force, this is made to simplify the selection and can be done because even if the force is known, his transmission from the handbrake to the mechanism vary depending on the type of handbrake.

The objective equation is:

m = ρ.L.A

And the constraint equation:

σ = F/A

Where:

• m = mass [kg]

• ρ = density [kg/m3]

• L = Length of the bar [cm]

• A = Cross-section of the bar [cm2]

• σ = stress in the bar [Pa]

• F = Force applied [N]

By combining those two equations:

A = F/σ

⇒ V = L.A = F.L/σ

⇒ ρ = m/V = m.σ/(F.L)

The unknowns being σ and ρ, the material index is:

M = σ.m

⇒ log (M) = log (σ) + log (m)

⇒ log (σ) = log (M) - log (m)

The linear equation has thus a slope of 1 that we want to maximize.

The corresponding Ashby diagram is put above (Picture 7).

Another important aspect is the economic part, therefore another Ashby diagram can be made

evaluating the price in function of the fracture toughness (Picture 8).

Finally, with the comparison of the two Ashby diagrams obtained, a list of materials is obtained for the blocking mechanism (last picture ).

Mechanical Systems

Requirements

The main requirement of the mechanical part is to block the car's handbrake, meaning it must withstand a load of 17 kPa in our case. It should be easy to install, cause minimal intrusion or distraction to the driver’s normal routine, and ensure a very low switching time between states (from blocked to unblocked and vice versa) in order to securely block the car and prevent the driver from driving while intoxicated.

Conceptual design: preliminary concepts and selection

Several preliminary concepts were considered for the design:

1. A piston with a motor capable of locking it in different positions, attached to the handbrake.
2. A gear system involving a rack and pinion mechanism.
3. A passing bar through another, secured by a pin that locks them together.
4. A bar clamping system inspired by an existing design on the market.

To ensure robustness while minimizing complexity, the pin mechanism was selected and further developed as the most suitable concept.

Embodiment design: manufacturing and assembly (justification of all the choices)

As our main goal is to follow the motion of the handbrake and lock it when needed using a pin mechanism to externally control its motion, we require a component capable of rotating approximately 0 to 90°. This exceeds the actual maximum rotation angle of a handbrake which is around 30 to 45 degrees from its fully disengaged to fully engaged position because we lack access to its center of rotation and aim to act only on the handbrake bar to interrupt its motion with the support of the external handbrake structure of the car, thus a larger angular range is necessary for our system.

To ensure compactness and accommodate the solenoid, we based our mechanism on the slider-crank mechanism.This mechanism effectively converts rotational motion into translational motion, allowing easier control as the solenoid manages the permitted translational motion

To allow full rotational motion in the crank (360°), the conditions |DB| − |BC | > |C D| sin(α2) and |DB | > |BC | must be satisfied. Thus, they must also be respected in our model. There are joints at B, C, and D to allow the motion of the system. From point A, a part of the locking mechanism will be attached to the handbrake, enabling it to recover the load applied to the handbrake to release it. The load will then be transferred to component AC, which will further transfer it to DB, and subsequently to CD, where a solenoid will be placed. The solenoid will act as a pin through holes in CD to block and unblock the overall system.

To reduce the load applied at point A and supported by the system, we will place two of these sliding mechanisms in parallel. This configuration will divide the effort by two and balance the structural load

Furthermore, some considerations must be made for the position of point B. From a static analysis since component DB transfers the load to CD, the position of B is crucial. As CA is subjected to bending, the farther B is from A, the greater the load applied to joint B. Therefore, B should be as close as possible to A to minimize this effect.

From cinematic analysis, the motion of the slider can be written as

⇒x_D = |BC|(1 − cos(α2))+ |DB |/|BC | − sqrt((|DB|/BC)^2 − (sin(α2))^2)

For an optimal design, the position of B should ideally depend on the type of handbrake. However, to create a standard device, we will position B such as for a given length |DB| it will be as much close as possible to A while allowing a correct motion of the overall system.

We chose |DB | ≤ |C A|/2 so that when α2 = 0, the length of |C D| + |DB | will, at most, equal |C A|. This choice ensures the compactness of the design.

Thus, for |C A| = 15cm, by using the previous constraint we find |DB| = 7.5 and |BC | ≈ 4.5cm

This provides a maximum volume of clutter for the blocking mechanism, based on dimensions of L = 20 cm, l = 12 cm, and H = 20 cm, resulting in a total volume of 4,800 cm³.

PS(|CA| = 15 cm and l = 12 cm is an estimation based on the handbrakes we commonly used in our daily life)

Final CAD Design components

The final CAD design incorporates the essential functional components that address the identified design constraints. Only the functional parts relevant to the final product are considered, as opposed to the prototype. Below is a breakdown of the main components:

1. Linking Bars (H-S Bars, B-S Bar, and Bar Linkage):
2. These bars, labeled as 1 and 2 in the accompanying image, are designed to support and transfer the driver's force to the slider. They ensure efficient force transmission while maintaining structural integrity.
3. Solenoid Case (Left and Right):
4. Designed to house the two solenoids, the case allows slight rotational adjustment relative to the hole axis. This ensures that the solenoid pin aligns perfectly with the locking holes during operation.
5. Base Part (Left and Right):
6. The base contains holes that facilitate pin locking and incorporate speed bumps to guide the solenoid pin into the correct locking position. Additionally, it includes guiding rails to maintain the solenoid case's rectilinear motion.
7. Hand Brake Attachment:
8. This component securely binds the hand brake to the bars, ensuring effective transfer of rotational movement to the slider for proper functionality.

All components have been assembled into a comprehensive CAD file named "D&M final product.SLDASM". This file validates the design's motion and functionality.

Design testing

After assembly, the final design delivered the expected motion and resistance as validated through SolidWorks motion simulations and prototype testing. The attached videos provide a visual demonstration of these motion tests.

CAD files provided

Attached to this section are the CAD files for both the prototype and the final product. These include:

1. The individual components.
2. The full assembly for the final product.

https://drive.google.com/drive/folders/12HgkbM-VZ0WK6L8ubvUed7P6mPjtjMHB?usp=sharing

Circuitry & Sensors

Requirements

The primary goal of the circuitry is to integrate and manage the various electronic components in a reliable and efficient manner. This includes powering and getting the data of the sensor and the switch, transferring the signals of the code to the rights components (relay and LEDs)The specific requirements are:

Voltage and Current Supply:

• 5V for the Arduino.

• 12V for the solenoid, hence the use of a relay.

Sensor Accuracy:

• The alcohol sensor (MQ-3) must provide stable and precise readings to ensure correct system operation.

Logical Control:

• The Arduino must control the LEDs and relay via digital or analog signals.

Electrical Safety:

• Include resistors to protect the circuit from surges and ensure long-termdurability.

System Stability:

• Proper cable management and additional protection against electrical noise to prevent in-

terference or short circuits.

Design process and considerations of components

The circuit is designed to achieve simplicity, reliability, and modularity. Below are the major considerations for each component:

Alcohol Sensor (MQ-3):

Connected to an analog pin (A0) of the Arduino for real-time reading. Powered by the 5V output

of the Arduino.

LED Indicators:

One green LED (D13) and one red LED (D12) indicate the system status (alcohol level below or

above threshold).

Relay for Solenoid:

Controlled by a digital pin (D9) of the Arduino. Acts as a switch to manage the 12V power supply

for the solenoid.

Power Supply:

A 12V car battery is used as the primary power source and the 12V is directly used for the

solenoid via the relay.

Final Circuit Diagram

see Picture 6

Testing

Testing the circuitry ensures that each component operates as expected:

Alcohol Sensor (MQ-3): Verify stable readings for different alcohol concentrations. Calibrate

the threshold for switching LEDs (e.g., a threshold of 300 for the red LED).

Relay and Solenoid: Test the relay activation and deactivation by the Arduino. Confirm the

solenoid’s movement and locking/unlocking capability.

System Integration: Check the transition between states (green to red LED and solenoid activation).

Provide exact components

See picture 5

Software

Requirements

The code should be able to receive the analog signal of the sensor and compare it to a threshold (= legal limit). It will then send a signal to the LED's (Green if the level of alcohol is below the threshold, or Red else) and one to the relay (if the level of alcohol is lower than the threshold, signal releasing the solenoids).

In order to minimize the power consumption, the system should be able to be inactive for a moment till the end of the car trip.

Design process and considerations of components

The first code designed was implemented with a function acquiring the level of alcohol from the sensor, another to light the green or red LED and one last to send to the relay (like explained in the requirements).

The second code added an initial state, permitting the user to see if the system is working well, an inactive mode who can be reactivated by a switch. A function was thus designed to receive the signal of this switch and change the state to reactivate the system.

The third and last code implemented fixes the wrong answers of the system and implemented a parking mode, who shut the system down after the switch was pushed. (cf. last picture)

The integration of all the components of the prototype is explained below. It is mainly divided into two subsystems: the box containing the electronics and the blocking system.

Regarding the box, it is first assembled by gluing the different walls together, leaving the interior hollow to store the electronic components. Inside, the Arduino and the breadboard are placed. Then, the sensor is inserted into the hole made for it and connected to the Arduino and the breadboard using wires. The same steps are followed for the LEDs and the switch, but the switch is placed on the top cover. All the connections are made considering the best possible arrangement inside the box, adjusting the wires to the correct length to ensure clean connections. Once this subsystem is assembled, the focus shifts to the blocking system.

For the assembly of the blocking system, all the layers made with laser cutting are combined with the 3D-printed layers with holes, fitting them together using screws and nuts. The sliding parts are fitted into their rails before tightening the screws. Then, the solenoids are inserted into their holders (which are the sliding pieces) and are also connected to the breadboard to communicate with the other components. To be powered with 12V, they will be connected to a power supply unit.

Once assembled, it will be ready to be attached to the handbrake and operate as intended.

The assembly of the complete prototype can be done by following these steps:

1. Screw the attach to the long bars.
2. Screw the short bars at the middle hole of the long bars
3. Put the solenoids in the cases with the back of the solenoids facing the square hole
4. Screw the solenoids case at the other end of the short bars
5. Slide this assembly into the side wall
6. Screw the front wall and the sides with the holes to the side wall
7. Screw the back wall with the bars
8. Connect the wires of the solenoids to the back of the sensor box
9. Connect the sensor box to the 5V and 12V power supply
10. The sensor can be attached to a steering wheel with the strap belt

As improvement, the next prototype should focus on,

for the box:

1. Reducing the size of the box
2. Implementing the attach for the straps
3. Redesign the snap-fit system to fit the last design
4. Make the LEDs more visible from the outside

for the mechanism:

1. Adjusting the prototype to avoid misalignment
2. Manufacturing the pieces according to the detail design step

Sustainability concern two parts of the project :

Ecological aspect:

As shown in the table, PLA is a sustainable material for being natural, recyclable, biodegradable and renewable, while needing few energy to produce and process it. In addition, its CO2 footprint is very low.

On the other hand, steel is an energy consuming material with a high CO2 footprint while being not

Biodegradable and renewable. But can still be recycled.

Toughness:

The laser cut pieces (sensor box, side and back walls) are strong enough to sustain shocks without breaking or being damaged severely.

The 3D printed pieces (bars, solenoid cases, hole and front walls) could resist the forces applied to them during the tests. Nonetheless, the limits were not tested;

Borel Bouwe

I hold a Bachelor’s degree from Haute École Louvain en Hainaut (HELHa) in Industrial Engineering of Electromechanics. I am currently pursuing the BRUFACE Master’s program in Robotics and Mechatronic Construction. My contributions focused on conceiving, designing, and building the blocking mechanism alongside Genial. I also 3D-printed several prototype parts and contributed to the overall assembly process.

Marwan El Haddaoui

I completed my bachelor’s degree at the École Polytechnique de Bruxelles at the Université Libre de Bruxelles. I am currently pursuing a Master’s degree in Electromechanical Engineering with a specialisation in Mechatronics, Robotics, and Construction. I worked on the electronics, software design, and assembly aspects of the project, contributing to both the development and integration phases.

Antoine Keiser

I did my bachelor at the University of Charleroi which was a joint UMONS and ULB teaching. I am now following the master Bruface robotics program at Bruxelles. I worked on the electrical part of the project and helped Jorge on the sensor box. My favourite part of the project was the assembly of the blocking mechanism.

Jorge Rivera

BSc and MSc in Industrial Technologies Engineering from the Polytechnic University of Madrid. I moved to Belgium to continue my education as a BRUFACE Master student with specialisation in Module Robotics and Mechatronics.

Genial Shongo

I earned my Bachelor’s degree in Electromechanical Engineering from the École Polytechnique de Bruxelles at Université Libre de Bruxelles (ULB) and am currently advancing my studies with a Master’s degree in the same field. My specialization focuses on Mechatronics, Robotics, and Construction

In this project, I thoroughly enjoyed the opportunity to learn new skills while working on the mechanical aspects, including mecanical , CAD and assembly design of the handbrake . My role extended across both the "development" and "eco-integration" phases.

Martin Vanopdenbosch

Bachelor at the École Polytechnique de Bruxelles at the Université Libre de Bruxelles, currently in Master I with specialisation in Module Robotics and Mechatronics. I mainly worked on the software design and prototype assembly and tests