User:Netisurya95/sandbox

= Airbag Integrated Helmet Design =

Abstract
Multiple concepts designed to prevent neck and cervical spine injuries of a motorcyclist during accidents have been explored and discussed, detailed analysis for each of these has  also been done. Based on which, a novel innovative design,of a helmet using an airbag that inflates when triggered and envelops the neck and collar expanse of a motorcyclist upon collision, has been proposed. A prototype was made and tested, the results and the critical analysis of the design  are also presented.

Introduction
Currently two wheeler is the predominant mode of transport most Indians use. They are more suitable to the traffic and road conditions, and are also cost effective/economical, hence pertinent for use in  a developing country. Unfortunately, two wheelers continue to be the most vulnerable to accidents. The latest data released by the home ministry has revealed that “21% of the road death victims in 2009 in the country were riding two wheelers....estimates suggest that over 60% of the country's motor vehicles are two wheelers.” And with so many users for this product category, it becomes vitally important that safety is ensured during use.

‘Helmets’ function as a protective carapace to the head and skull preventing damage to our most important organ- the brain. Although safety awareness and the general habit of wearing helmets by the two-wheeler users is on the rise, there are certain issues with the current design that this project attempts to address.

A study published in the Asia Pacific Journal of Public Health shows that in rear-end, side impact, and skidded accidents, the use of helmets increases the probability of a severe cervical spine injury. Another study indicated that “Both helmeted and unhelmeted motorcyclists in these fatal crashes showed a high frequency of soft tissue neck injuries such as hemorrhages in the carotid sheath, hemorrhages surrounding the phrenic nerves or the brachial plexus...”

Hence, we attempted to design a product that modifies the current design of the helmet while also protecting the cervical spine from injury. The design bases on inflating an airbag when a collision is detected by sensors placed appropriately. A detailed explanation of alternate designs and more is given in the following sections.

Target Market
Potentially, all the two-wheeler users / motorcyclists benefit from the use of this product since it improves the safety of the user. Hence each and every one of the operators of the 85.8 million two wheelers currently plying on our roads constitute our market size. We intend to make the design cost-effective and hence affordable to all the financial sectors of the economy. This statistic only accounts for domestic sales, the device can be very well used and hence sold outside India as well.

Our market segment includes the middle class and neo-middle class of the economy who heavily depend on the two wheelers as a daily mode of transport. Our design although has not been calibrated for the use of professional motorcycle racers, a variation in the design can  be implemented in this domain as well to increase user safety.

Neck Brace
The basic principle of a neck brace is to redirect some of the forces that can stress the neck otherwise through alternate load paths into other areas of the body. Secondly, a neck brace can limit the extreme ranges of motion of the neck in instances when the neck is injured and Spinal Cord Injury has not yet occurred, but the rider is still mid-crash. More importantly, the neck brace slows the head in a controlled manner, it has failure points where the brace will deform or break, when subjected to extreme forces, thus it cannot cause damage to the rider. Following are some of its drawbacks:
 * It restricts the neck movement while riding, blocking the peripheral vision
 * The rigid carbon fiber design is uncomfortable to wear
 * It costs Rs.17,000 - Rs.34,000

APC Airbag Helmet
Utilizing accelerometers and gyroscopes, the airbag is activated through a remote switchboard which is fitted on the motorcycle that interprets the changes in movement. The total time between detection of accident and full inflation is slightly less than 1½ seconds.The airbag is mounted under the helmet. Also, the helmet is equipped with Bluetooth and has an ultra-light external protective shield made of fiber composite and is available in various sizes. Following are some of its drawbacks:
 * Due to the Rear-biased weight and altered aerodynamics, the structural integrity of the helmet during a collision might affect rider fatigue.
 * It costs the same as a standard helmet + neck brace Rs. 63,000

Pro-Neck-Tor by University of British Columbia
Pro-Neck-Tor™ uses a double-shell design with engineered mechanical guides that connects the two shells. During a head-first impact, this design induces the head motion along an engineered path either in forward or in backward direction by guiding the inner shell relative to the outer shell, thereby reducing the neck's need to stop the following the torso, and minimizing the excess load on the neck during impact. Proof of concept using an instrumented mechanical head and neck model have demonstrated that Pro-Neck-Tor™ reduces neck injury in head-first impact.

Biomechanics of Head and Neck Trauma
For an unhelmeted head, the amount of force a head can withstand depends on several factors, including the location of the impact, the size of the object striking the head and the density of the individual’s bone tissue. The frontal bone (forehead) can withstand on average, 1,000 to 1,600 pounds of force. The temporo-parietal (sides of head) bones can tolerate around 700 to 1,900 pounds of force, the back of the skull can handle around 1,440 pounds of force. The bones of the face and cheek are less tolerant, standing forces of only 280 to 520 pounds.

'G-forces' determine the extent of injury to the head or neck in many motorcycle accidents. When a body is stopped (due to crashing into a stationary object) or is hurled into space with a 3 pound helmet flexing the neck, the force of gravity causes the body to weigh many times its actual weight. For example, a male human head, without helmet, weighs about 10 pounds. If subjected to 10 'G's', that head briefly weighs about 100 pounds, passing that stress and load onto the neck.

To determine the number of 'G-forces' in a collision, the formula is: G's = .0333 X (M.P.H. X M.P.H.) Distance. In other words, multiply the square of the vehicle's speed, in mph, times .0333 and divide it by the stopping distance in feet. This is for a direct, head on collision, and the formula is more complex in angular collisions due to the fact that the kinetic energy is expanded over a longer period of time, resulting in lower 'G-forces'.

It has been suggested that race car drivers exceed speeds of 200 miles-per-hour and walk away from crashes because they had a helmet on. Modern technicians have learned that in order to protect the driver, the race car must crush and disintegrate during a crash. This allows for a more gradual, extended period to distribute the force of the crash and decelerate the 'G's'. The problem with motorcycle design is that there is no safety cockpit that would afford us the room and time for a disintegrating chassis to take up the 'G-forces' for us. And we don't have anything padded in front of us to reduce the loads reaching our neck, such as a break away steering wheel or padded dash panel. Hence, an airbag that envelops the neck and collar expanse would be helpful in this case.

Concept Generation
The underlying idea is  to ensure that an airbag (which is attached to the base of the helmet) is inflated when a specific sensor positioned on the motorcycle triggers a collision.

Metrics to consider for the process design of inflation of the bag

 * Time required; It is crucial that the bag, inflate within 15 - 30 milliseconds after the first impact contact and fully inflate in approximately 60 - 80 milliseconds (~the same time as the airbags in a car).
 * Additional weight & space; The design should not impose a lot of weight on the current design of the helmet which would make the product highly inconvenient for usage especially during an activity like driving that requires focused attention.
 * Cost; The additional cost levied due to the inclusion of the system components should be as minimum as can be achieved. An additional safety feature should be available to all sectors of society, hence it is crucial that the product be made inexpensive.
 * Stability; We would have to ensure that the system/design that deploys the bag is stable by itself (for daily rough use) and does not set off unnecessarily.
 * Safety; The process by which the inflation would occur should not cause any injury to the user when in active use or when passively stored at homes/ work places etc...
 * Durability: In addition to this, durability will decide the usage of this product in the long run. A helmet can be subjected to extreme harsh conditions if an accident occurs, so it should be able to withstand certain high amounts of  wear, pressure and damage.

Implementation of an ‘Airbag’ (Vacuum pump)
This design includes the use of a 12 V DC motor, 12 W operating power, 0-16” Hg vacuum range, 0.25” barbs, with two openings- one  that sucks in air and the other that pumps air out. It is commonly used to create vacuum but can be used to fill tires, or inflatable pillows etc…as well. It does not expel air at a faster rate, but is reliable.

Implementation of an ‘Airbag’ (Compressed Air)
This design includes the use of Compressed CO2 Cartridges (available in the market) to ensure the inflation of the airbag. A single cartridge is attached to the airbag of the helmet via a solenoid valve and is triggered when the collision occurs. (Further details are mentioned in the following sections)

Subjective Analysis

 * Time required for inflation of airbag: On using a vacuum pump, the inflation time is around 33 seconds which is too high in comparison to using compressed air which takes less than 2 seconds.
 * Additional Weight & Space: The electronics components involved in both the design are the same. The first design uses a 12V DC vacuum air pump measuring ~ 6cm x 4cm x 3cm. The second design uses a 16g CO2 Cartridge measuring ~ 0.95cm x 8.25cm and also a solenoid valve measuring 1.5 kgs, It can be clearly seen that the second design adds more weight and occupies a significant amount of space when compared to the first design
 * Cost: The principle component of the first design is the 12V DC vacuum air pump which costs Rs. 800. The main components of the second design are the 16g CO2 Cartridge and the solenoid valve  which costs Rs.200 and Rs.950 respectively. So if we take the overall cost of the product, it is safe to say that the difference in cost is nominal.
 * Stability: The degree of stability of both the design are nearly same considering the fact that it depends on the calibration of the sensors which detect if accident occurs. Nevertheless, there is a slight danger of leakage of the CO2 Cartridge in the second design.
 * Safety: Since the inflation time of compressed air is far better than the vacuum air pump, the second design is more reliable and safe to use.
 * Durability: The lifetime of both the designs are limited, hence it’s essential to check its condition from time to time.

Concept Scoring
Therefore, the second design using Compressed Air has been selected after thorough analysis

Sensor module + Transmitter module
This module mainly includes the  MCP-6050 Gyro-sensor. It is placed on the motorcycle/two-wheeler along with the RF Transmitter unit. When the vehicle tilts beyond a certain angle, so does this module,  hence the gyro-sensor activates and measures this angle. The processing of this algorithm is implemented in C language. The C-files are compiled using HT-PIC C-compiler which compiles the C-file to a Hex-file (.hex). This file is loaded into the micon using Microchip ICD-3 programmer into the flash memory of the micon, which is present on the transmitter unit. Micon gets connected to the Gyro-sensor by I2C interface (SCL,SDA lines). Micon can read through I2C acc-x, acc-y, acc-z, and all other registers in the Gyro-sensor. These registers are 16 bit registers in the 2's complement format giving -32768 to +32767 counts.

Angle considered for triggering collision
Only along the X axis (vertical axis,) = ~ 65 deg

Only along the Y axis ( falling on the side, neglecting steep turn tilts) = ~ 50 deg

When both the angles are non zero simultaneously: ~(35 deg, 35 deg)

This count is corresponding to -2g to +2g of x,y,z axes. We place the Gyro-sensor on the board so as to acquire only the relevant x and y axes values.. We read them every 20 milli secs. Each time we delete oldest reading, copy old reading ( acc-x[1] into acc-x[2], acc-x[0] into acc-x[1], and the new reading into acc-x[0] )

Thus the these form the last three readings. Similarly for acc-y in the Y direction. Then we compare these reading with certain pre-defined values and decide if they indicate any accident or not. On the occasion that there is an accident we activate RA1 pin which is connected to the Data pin of the transmitter unit. As long as the accident condition remains and for 200 milliseconds after it disappears, pin RA1 will keep toggling between logic 0 and logic 1, thus generating ASK modulated signal out of Transmitter.

Receiver module
The signal sent by the transmitter as mentioned above will be picked up by the receiver unit’s  Antenna, making its Data pin Toggle in a similar way. This Data pin of the receiver is connected to the RB4 pin of micon. Micon, when it senses that this pin RB4 is toggling consistently (4 consecutive times), micon extends supply to the base of the transistor via RC0, thus making the Relay ON.

Inflation Module
The module consists of a Solenoid valve (220V AC) that has a sharp “pin” like structure which is used to puncture the cartridge positioned in the interior of the opening.. When the signal is received from the transmitter unit, the Relay activates. The contact of the relay closes making the 220V AC supply extend to the solenoid valve opening.

The CO2 cartridge is placed carefully positioned such that the top layer is completely pierced but without any leaks. The compressed gas in this state stays in high pressure conditions until the valve is triggered and opened, once this happens, the gas immediately flows through the open valve and fills the airbag.

Circuit Design:
* RX - RF Receiver Unit * TX - RF Transmitter Unit

Functional Decomposition




Critical Analysis of the Design
Time taken for inflation of airbag upon receiving signal = 2 sec
 * Time taken for detection and communication from transmitter to receiver = 0.5 sec

Overall it takes merely 2.5 sec for the deployment of airbag from the instant the accident occurs. This gives us a huge margin of safety and ensures the user is secured cautiously even before he hits something. The standard 0-80 bar solenoid valve commercially available in the market is the heaviest component in the system weighing a whopping 1.5 kg. Other ways to trigger the cartridge by custom manufacture of components can be explored. For the prototype made though the bill of materials cost is expensive. Mass manufacturing and industry scale assembly of the components can reduce the cost significantly. The increase in cost of the helmet owing to the additional setup compensates for the enhanced safety aspect. The novel idea of using an airbag for protecting the neck has proved very effective in serving its purpose. The airbag functions by directing the crash forces from the helmet to the body and bypassing the neck. The premise of using an inflatable airbag design is the level of comfort and convenience it offers to the user making the whole riding experience enjoyable and also assuring the safety at the same time.
 * Total weight of the additional setup = ~1.9 kg
 * Total cost of the additional setup = Rs. 2446
 * The present prototype is calibrated to sense an accident by measuring the angle of gyro-sensor placed on the motorcycle. Thus, this takes care of the case in which the user falls to the ground along with the vehicle. But other possible scenarios like head on collision has to be taken into consideration and a better algorithm needs to be worked on.

Scope for Improvement

 * Additional weight & space: The individual components chosen were not optimized to minimize the weight and space that the design adds to the current helmet form. This was due to cost issues and market availability of those components. This issue can be resolved by considering less heavy and bulky valve with suitable specifications, and printing a circuit board instead of soldering one.
 * Power supply hindrance for valve: The valve requires a 220V AC power supply for functioning, this has to be given from a battery. It also has to be included in the design which would be additional weight.
 * A safety module: The addition of a safety module that ensures that the pierced compressed gas cartridge does not begin to leak in time, or prevent such situations so as to provide safety for the user is important.
 * Changing cartridges after use: The current design used compressed CO2 cartridges that are a one time use only product. Once the bag is deployed because of a collision, the user has to change the old empty cartridge to a new full one which requires him/her to travel to the suitable store. These multiple trips can be avoided by implementing a pump with faster air supply rate, that uses surrounding air to fill the bag.