29-08-2014, 03:16 PM
AUTOMATIC BRAKING SYSTEM FRONT AND BACK
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INTRODUCTION
We have pleasure in introducing our new project “INTELLIGENT BRAKING SYSTEM”, which is fully equipped by IR sensors circuit and Pneumatic breaking circuit.
It is a genuine project which is fully equipped and designed for Automobile vehicles. This forms an integral part of best quality. This product underwent strenuous test in our Automobile vehicles and it is good.
The “PNEUMATIC BRAKING CIRCUIT” can stop the vehicle within 2 to 3 seconds running at a speed of 50 KM. The intelligent breaking system is a fully automation project.
This is an era of automation where it is broadly defined as replacement of manual effort by mechanical power in all degrees of automation. The operation remains an essential part of the system although with changing demands on physical input as the degree of mechanization is increased.
NEED FOR AUTOMATION
Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc., of these sources, pneumatics form an attractive medium for low cost automation. The main advantages of all pneumatic systems are economy and simplicity. Automation plays an important role in mass production.
For mass production of the product, the machining operations decide the sequence of machining. The machines designed for producing a particular product are called transfer machines. The components must be moved automatically from the bins to various machines sequentially and the final component can be placed separately for packaging. Materials can also be repeatedly transferred from the moving conveyors to the work place and vice versa.
LITERATURE SURVEY
SAFETY SYSTEM
The aim is to design and develop a control system based on pneumatic breaking system of an intelligent electronically controlled automotive braking system. Based on this model, control strategies such as an 'antilock braking system' (ABS) and improved maneuverability via individual wheel braking are to be developed and evaluated.
There have been considerable advances in modern vehicle braking systems in recent years. For example, electronically controlled ABS for emergency braking, electronically controlled hydraulically actuated individual brake-by-wire (BBW) systems for saloon cars and electronically controlled pneumatically actuated systems for heavy goods vehicles. The work of recent years shall form the basis of a system design approach to be implemented. The novelty of the proposed research programmed shall lie in the design and evaluation of control systems for achieving individual wheel motion control facilitated by BBW. In the case of BBW the brake pedal is detached from the hydraulic system and replaced by a 'brake pedal simulator'. The simulator provides an electrical signal for the electronic control system.
Preliminary modeling and simulation work considers a quarter cars initially followed by a natural progression to the half car and full four wheel station cases. The model is to be constructed in modular form thus allowing the replacement / interchange of the various blocks and their associated technologies. Upon completion of the full vehicle braking model, sensitivity analyses will be carried out. Once the preliminary simulation model has been thoroughly benchmarked and existing control system strategies evaluated, an audit of the technology used is to take place and this will provide a basis for comparison of iterative technologies / techniques.
The final phase of the new modern vehicle shall include:
• Development of improved ABS control systems
• Development and assessment of an electro-hydraulic-BBW (EH-BBW) system
• Individual wheel braking combined with traction control
• Assessing sensor failure and fault tolerant control system design
• Preliminary studies into an electrically actuated system
• Re-engineering using simplified models.
PNEUMATICS
The word ‘pneuma’ comes from Greek and means breather wind. The word pneumatics is the study of air movement and its phenomena is derived from the word pneuma. Today pneumatics is mainly understood to means the application of air as a working medium in industry especially the driving and controlling of machines and equipment.
MECHANICAL BRAKE
In a motor vehicle, the wheel is attached to an auxiliary wheel called drum. The brake shoes are made to contact this drum. In most designs, two shoes are used with each drum to form a complete brake mechanism at each wheel. The brake shoes have bake linings on their outer surfaces. Each brake shoe is hinged at one end by on anchor pin; the other end is operated by some means so that the brake shoe expands outwards. The brake linings come into contact with the drum. Retracting spring keeps the brake shoe into position when the brakes are not applied. The drum encloses the entire mechanism to keep out dust and moisture. The wheel attaching bolts on the drum are used to contact wheel and drum. The braking plate completes the brake enclosure, holds the assembly to car axie, and acts the base for fastening the brake shoes and operating mechanism. The shoes are generally mounted to rub against the inside surface of the drum to form as internal expanding brake as shown in the figure
HYDRAULIC BRAKES
The hydraulic brakes are applied by the liquid pressure. The pedal force is transmitted to the brake shoe by means of a confined liquid through a system of force transmission.
The force applied to the pedal is multiplied and transmitted to brake shoes by a force transmission system. This system is based upon Pascal’s principle, which states that “The confined liquids transmit pressure without loss equally in all directions”.
It essentially consists of two main components – master cylinder and wheel cylinder the master cylinder is connected by the wheel cylinders at each of the four wheels. The system is filled with the liquid under light pressure when the brakes are not in operation. The liquid is known as brake fluid, and is usually a mixture of glycerin and alcohol or caster-oil, denatured alcohol and some additives Spring pressure, and thus the fluid pressure in the entire system drops to its original low valve, which allows retracting spring on wheel brakes to pull the brake shoes out of contact with the brake drums into their original positions. This causes the wheel cylinder piston also to come back to its original inward position. Thus, the brakes are released.
AIR BRAKE
Air brakes are widely used in heavy vehicle like buses and trucks which require a heavier braking effort that can be applied by the driver’s foot. Air brakes are applied by the pressure of compressed air, instead of foot pressure, acting against flexible diaphragms in brake chamber. The diaphragms are connected to the wheel brakes. These diaphragms are controlled through a hand or foot operated valve. The brake valve controls brake operation by directing the flow of air from a reservoir against diaphragms in the brake chamber when the brakes are applied and from brake chambers to tube atmosphere when the brakes are released. The air compressor, driven by the engine furnishes compressed air to the reservoir fall below a set valve.
ELECTRIC BRAKE
Electric Brakes are also used in some motor vehicles, although these are not very popular. Warner electric brake is one of the examples of such brakes. An electric brake essentially consists of an electromagnet within the brake drum. The current from the battery is utilized to energize the electromagnet, which actuates the mechanism to expand the brake shoe against the brake drum, thus applying the brakes. The severity of braking is controlled by means of a rheostat, which is operated by the driver through the foot pedal.
VACUUM BRAKES / SERVO BRAKES
A serve mechanism fitted to the braking system reduces the physical effort the driver has to use on the brake pedal most servo mechanisms are of the vacuum assistance type. A pressure differential can be established by subjecting one side of the piston to atmospheric pressure and the other side to a pressure below atmospheric pressure by exhausting air from the corresponding end of the servo cylinder.
IR SENSOR
A sensor is a transducer used to make a measurement of a physical variable. Any sensor requires calibration in order to be useful as a measuring device. Calibration is the procedure by which the relationship between the measured variable and the converted output signal is established.
Care should be taken in the choice of sensory devices for particular tasks. The operating characteristics of each device should be closely matched to the task for which it is being utilized. Different sensors can be used in different ways to sense same conditions and the same sensors can be used in different ways to sense different conditions.
CAPACTIVE SENSOR
Unlike inductive and Hall-effect sensors which detect only Ferromagnetic materials, capacitive sensors are potentially capable (with various degrees of sensitivity) of detecting all solid and liquid materials. As this name implies, these sensors are based on detecting a change in capacitance induced by a surface that is brought near the sensing elements.
OPTICAL PROXIMITY SENSORS
These are similar to ultrasonic sensor in the sense that they detect proximity of an object by its influence on a propagating wave as it travels from a transmitter to a receiver. This sensor consist of a solid state light emitting diode (LED), which acts as a transmitter of infrared light, and a solid state photo diode which acts as a receiver.
The cones of light formed by focusing the source and detector on the same plane intersect in a long, pencil-like volume. This volume defines field of operation of the sensor since a reflective surface. Which intersects the volume is illuminated by the source and simultaneously seen by the receiver
PNEUMATIC BRAKING COMPONENTS
SELECTION OF PNEUMATICS
Mechanization is broadly defined as the replacement of manual effort by mechanical power. Pneumatics is an attractive medium for low cost mechanization particularly for sequential or repetitive operations. Many factories and plants already have a compressed air system, which is capable of providing both the power or energy requirements and the control system (although equally pneumatic control systems may be economic and can be advantageously applied to other forms of power).
The main advantages of an all-pneumatic system are usually economy and simplicity, the latter reducing maintenance to a low level. It can also have out standing advantages in terms of safety
PNEUMATIC COMPONENTS AND ITS DESCRIPTION
The pneumatic bearing press consists of the following components to fulfill the requirements of complete operation of the machine.
i. Double acting Pneumatic cylinder
ii. Solenoid valve
iii. Flow control value
iv. Connectors
DOUBLE ACTING PNEUMATIC CYLINDER
The cylinder is a double acting cylinder one, which means that the air pressure operates alternatively (forward and backward). The air from the compressor is passed through the regulator which controls the pressure to required amount by adjusting its knob. A pressure gauge is attached to the regulator for showing the line pressure.
Then the compressed air is passed through the directional control valve for supplying the air alternatively to either sides of the cylinder. Two hoses take the output of the directional control valve and they are attached to two ends of the cylinder by means of connectors. One of the outputs from the directional control valve is taken to the flow control valve from taken to the cylinder.
An air cylinder is an operative device in which the state input energy of compressed air i.e. pneumatic power is converted in to mechanical output power, by reducing the pressure of the air to that of the atmosphere.
Frame
The solenoid frame serves several purposes. Since it is made of laminated sheets, it is magnetized when the current passes through the coil. The magnetized coil attract the metal plunger to move. The frame has provisions for attaching the mounting. They are usually bolted or welded to the frame. The frame has provisions for receivers, the plunger. The wear strips are mounted to the solenoid frame, and are made of materials such as metal or impregnated less fiber cloth
WORKING OPERATION
The impartant components of our project are,
IR transmitter
IR receiver
Control Unit with Power supply
Solenoid Valve
Flow control Valve
Air Tank (Compressor)
The IR TRANSMITTER circuit is to transmite the Infra-Red rays. If any obstacle is there in a path, the Infra-Red rays reflected. This reflected Infra-Red rays are received by the receiver circuit is called “IR RECEIVER”.
The IR receiver circuir receives the reflected IR rays and giving the control signal to the control circuit. The control circuit is used to activate the solenoid valve. The operating principle of solenoid valve is already explained in the above chapter
CONTROL VALVE
In our project, we have to apply this breaking arrangement in one wheel as a model. The compressed air drawn from the compressor in our project. The compressed air floe through the Polyurethene tube to the flow control valve. The flow control valve is connected to the solenoid valve as mentioned in the block diagram.
CONCLUSION
This project work has provided us an excellent opportunity and experience, to use our limited knowledge. We gained a lot of practical knowledge regarding, planning, purchasing, assembling and machining while doing this project work. We feel that the project work is a good solution to bridge the gates between institution and industries.
We are proud that we have completed the work with the limited time successfully. The INTELLIGENT BRAKING SYSTEM is working with satisfactory conditions. We are able to understand the difficulties in maintaining the tolerances and also quality. We have done to our ability and skill making maximum use of available facilities.
In conclusion remarks of our project work, let us add a few more lines about our impression project work.
Thus we have developed an “INTELLLIGENT BRAKING SYSTEM” which helps to know how to achieve low cost automation. The application of pneumatics produces smooth operation.