Vehicle Safety
- 1. Vehicle Safety To avoid severe fatalities, injuries, property damage caused by motor vehicle , today’s vehicle manufacturer have introduced different safety system inside the car. Below are some major safety system- 1.Passive Safety Seat Belt, Airbag 2.Active Safety ABS, ESC/ESP , Brake Assist 3.Advanced Driver Assistance System Adaptive Cruise Control, Blind Spot, Attention assist , Precrash Systems 4.Cooperative safety
- 2. Passive Safety 1.Seatbelt :- In today’s scenario all cars are equipped with the three pointed seat belt for Driver (Mandatory), Front Passenger ( Mandatory), Rear Passenger(Optional). Seatbelt plays a vital role in preventing injuries. The basic idea of a seatbelt is very simple: It keeps you from flying through the windshield or hurdling toward the dashboard when your car comes to an abrupt stop. A seatbelt applies the stopping force to more durable parts of the body over a longer period of time to prevent injuries. A typical seatbelt consists of a lap belt, which rests over your pelvis, and a shoulder belt, which extends across your chest. The two belt sections are tightly secured to the frame of the car in order to hold passengers in their seats. In modern car ECU’s are intelligent enough to alert the Driver/Passenger about the seatbelt information whether it is buckled/unbuckled through different ways- sometime only a telltale, sometime telltale with buzzer(if vehicle moving) or telltale + buzzer + text warning display . A typical seat belt telltale is shown below
- 3. Passive Safety 2.Airbag :- Like seat belts, the concept of the airbag -- a soft pillow to land against in a crash is also used for safety purpose. The goal of an airbag is to slow the passenger's forward motion as evenly as possible in a fraction of a second. There are three parts to an airbag that help to accomplish this feat: • The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door. • The sensor is the device that tells the bag to inflate. Inflation happens when there is a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per hour). A mechanical switch is flipped when there is a mass shift that closes an electrical contact, telling the sensors that a crash has occurred. The sensors receive information from an accelerometer built into a microchip. • The airbag's inflation system reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas. Hot blasts of the nitrogen inflate the airbag.
- 4. Passive Safety 2.Airbag :- The airbag system ignites a solid propellant, which burns extremely rapidly to create a large volume of gas to inflate the bag. The bag then literally bursts from its storage site at up to 200 mph (322 kph) -- faster than the blink of an eye! A second later, the gas quickly dissipates through tiny holes in the bag, thus deflating the bag so you can move. The whole process happens in only one-twenty-fifth of a second. The powdery substance released from the airbag is regular cornstarch or talcum powder, which is used by the airbag manufacturers to keep the bags pliable and lubricated while they're in storage. ECU’s are intelligent enough to alert the Driver/Passenger about the airbag information whether it is functional through telltale. A typical airbag telltale is shown below
- 5. Active Safety 1. ABS:- Stopping a car in a hurry on a slippery road can be very challenging. Anti-lock braking systems (ABS) take a lot of the challenge out of this sometimes nerve-wracking event. There are four main components to an ABS system: • Speed sensors The ABS system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information. • Valves There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions: In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releases some of the pressure from the brake. • Pumps Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up. • Controller The controller is a computer in the car. It watches the speed sensors and controls the valves. It might take a car five seconds to stop from 60 mph (96.6 kph) under ideal conditions, but with ABS it could stop in less than a second.
- 6. Active Safety 1. ABS:- Typically a vehicle with ABS helps to stop the car smoother , faster by not locking the wheel . When the ABS system is in operation you will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves.
- 7. Active Safety 1. ABS:- You absolutely should not pump the brake pedal in a car with ABS. Pumping the brakes is a technique that is sometimes used in slippery conditions to allow the wheels to unlock so that the vehicle stays somewhat straight during a stop. In a car with ABS the wheels should never lock in the first place, so pumping the brakes will just make you take longer to stop. In an emergency stop in a car with ABS, you should apply the brake pedal firmly and hold it while the ABS does all the work. ABS prevent wheels from locking up and provide the shortest stopping distance on slippery surfaces. ECU’s are intelligent enough to alert the Driver/Passenger about the ABS information whether it is functional through telltale. A typical ABS telltale is shown below-
- 8. Active Safety 2. Electronic Stability Program(ESP)/ESC:- The German auto supplier Bosch developed the first ESP or Electronic Stability Control(ESC) system and the Mercedes-Benz S-Class and BMW 7-series were the first cars to use the new safety and regulatory devices. Electronic stability control, in particular, takes advantage of two other systems, ABS and traction control, plus a few special sensors, to do its job. ESC information is fed into the car's central computer via three types of sensor: • Wheel-speed sensors: One wheel-speed sensor at each wheel measures the speed of the wheel which the computer can then compare to the speed of the engine. • Steering-angle sensors: This sensor, in the steering column, measures the direction the driver intends to aim the car. If it's different than the direction the car is actually traveling, the ESC system will kick in. • Rotational-speed sensor: This is also known as the yaw sensor. It's the one in the middle of the car that measures the side-to-side motion of the vehicle. ESC can activate one or more individual brakes, depending on which wheel can increase driving safety the most, and control the throttle to lessen the speed at which the car is traveling. The sensor is looking for differences between the direction of the steering wheel and the direction the car is headed; the car's computer then makes the necessary corrections to bring the vehicle's direction of travel in line with what the driver wanted. ECU’s are intelligent enough to alert the Driver/Passenger about the ESC/ESP information whether it is functional through telltale. A typical ESC telltale is shown -
- 9. Active Safety 3. Brake Assist(BA/IBA):- The purpose of brake assist and its related technologies is to help us stop our vehicles sooner and faster. As your foot instinctively clamps down on the brake pedal for sudden stop a sensor immediately knows, by the speed and pressure of your foot on the pedal, that this is an emergency. Within a fraction of a second, the brake assist system signals the brakes to direct maximum clamping power to the brake calipers. The pedal pulses as its anti-lock braking system (ABS) kicks in, working in concert with the brake assist. The vehicle remains under control as it decelerates and stops far short of hitting anything. The IBA system uses a distance sensor located below the front bumper to measure the distance to the vehicle ahead. When the system judges that your vehicle is getting close to the vehicle ahead in the traveling lane, the vehicle ahead detection indicator on the instrument panel blinks and a warning chime sounds. The IBA system will be turned on/off by pushing the IBA OFF switch. The IBA OFF indicator light will illuminate when the system is turned off.
- 10. Active Safety 3. Brake Assist(BA/IBA):- The limitation of IBA The IBA system is not a collision avoidance system. It is the driver’s responsibility to stay alert, drive safely and be in control of the vehicle at all times. ► As there is a performance limit, the system may not provide a warning or braking in certain conditions. ► The system will not detect the following objects: — Pedestrians, animals or obstacles in the roadway — Motorcycles traveling offset in the traveling lane — Oncoming vehicles in the same lane
- 11. Advance Driver Assistance System 1. Adaptive Cruise Control Adaptive cruise control (ACC) is an intelligent form of cruise control that slows down and speeds up automatically to keep pace with the car in front of you. The driver sets the maximum speed — just as with cruise control — then a radar sensor watches for traffic ahead, locks on to the car in a lane, and instructs the car to stay 2, 3, or 4 seconds behind the person car ahead of it (the driver sets the follow distance, within reason). ACC is now almost always paired with a pre-crash system that alerts you and often begins braking. Adaptive cruise control is also called active cruise control, autonomous cruise control, intelligent cruise control, or radar cruise control. This is the case because distance is measured by a small radar unit behind the front grille or under the bumper.
- 12. Advance Driver Assistance System 1. Adaptive Cruise Control To use adaptive cruise control, you start the same as you would with standard cruise control. The driver turns ACC on, accelerates to the desired speed, then presses the “Set” button. It’s then possible to tweak the “+” and “-” buttons to raise or lower the speed, typically by in 1 or 5 mph increments. Lastly, the driver can set the desired gap behind the next car, most commonly by pressing a button to cycle among short, medium, and long following distances. An indicator in the instrument panel or head-up display shows a car icon and often what looks like converging-at-infinity lines, indicating the roadway. When radar detects a car ahead, a second car icon appears or the lone car icon changes color.
- 13. Advance Driver Assistance System 2. Blind Spot/Lane Keeping Assist/Forward Collision Warning A blind spot is an area that can't be seen in a driver’s mirror or that is masked by parts of the car's structure. So there has been some technology to overcome this difficulty known as Blind Spot Information System(BLIS). A typical blind spot monitoring system uses some kind of electronic detection device(s) mounted on the sides of the car (often in the vicinity of the external rear view mirrors or near the rear bumpers) that sends out either electronic electromagnetic waves (usually in the radar wavelengths) or takes computer-processed images with a digital camera and analyzes them. When one of these detectors notices another vehicle getting too friendly with your car, it tells you about it, usually by flashing a light in the driver's peripheral vision or by making audible sounds -- often using both methods. Lane departure warning(LDW) alerts you when you’re about to drift across, but only if your turn signal isn’t on. Lane departure warning has emerged as a key tool for driver safety. The technology has evolved over the last few years to lane keep assist where the car automatically corrects course if it reaches the lane markings, and now a higher level of lane keep assist that automatically keeps the car centered on the road. The corrections are subtle and the driver can always override the car and turn the wheel manually. The most common LDW system is a camera mounted high up in the windshield often as part of the rear view mirror mounting block. It captures a moving view of the road ahead. The digitized image is parsed for straight or dashed lines — the lane markings. As the car deviates and approaches or reaches the lane marking, the driver gets a warning: a visual alert plus either an audible tone, a vibration in the steering wheel, or a vibration in the seat. If the turn signal is on, the car assumes the driver is intentionally crossing over the lane, and there’s no alert.
- 14. Advance Driver Assistance System 2. Blind Spot/Lane Keeping Assist/Forward Collision Warning A collision avoidance system is an automobile safety system designed to reduce the severity of an accident. Also known as Precrash system, Forward collision warning system or collision mitigating system, it uses radar and sometimes laser and camera sensors to detect an imminent crash. Once the detection is done, these systems either provide a warning to the driver when there is an imminent collision or take action autonomously without any driver input (by braking or steering or both) The blue car's driver sees the green car through his mirrors but cannot see the red car without turning to check his blind spot (the mirrors are not properly adjusted)
- 15. Co-Operative Safety The Vehicle-Infrastructure Cooperative safety Systems support driving, and aim to avoid traffic accidents by notifying drivers of the information obtained through communications between the vehicles and sensors installed on the road, or among vehicles. Effects of Vehicle-Infrastructure Cooperative Systems that support driving: A lot of accidents has been prevented with the help of co-operative safety. Below are the graph that elaborates this
- 16. Co-Operative Safety 1. ITS(Intelligent Transport System) /Dedicated Short Range Communication(DSRC) As an addition to conventional services this system operates primarily on expressways and uses bidirectional communication between vehicles and infrastructure to provide traffic information services that support safe driving.
- 17. Co-Operative Safety 2. DSSS(Driving Safety Support Systems) These systems are designed focusing on general roads to convey information about vehicles, motorcycles, and pedestrians that are difficult for drivers to see, as well as traffic control information (traffic signals, etc.) from the transport infrastructure to vehicles to help ensure the safe driving operation.
- 18. Co-Operative Safety 3. Next Generation System(Use of UHF band radio waves) The new next generation of Vehicle Infrastructure Cooperative Systems uses direct communication between vehicles and pedestrians or among vehicles for continuous information exchange in order to prevent frontal collision accidents between vehicles and pedestrians at intersections difficult for drivers to see, which has been difficult to solve until now.