Modelling And Simulation Of Anti Lock Braking System Abs Computer Science Essay

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In every vehicle the most important role is played by the BRAKING SYSTEM. Now-a -days every vehicle comes with advanced type of braking system. In recent years there is been enormous changes taking place in the braking system. Many new technologies have been developed to make the braking system more efficient and easy, so there is no extra effort needed to be applied while braking. Traditionally two types of braking systems are used in the vehicle Drum Brakes or Disc brakes or the combination of the two. But in recent years Disc Brakes are more often used in each and every vehicle due to its more effective braking and efficiency which is more as compared with disc brakes. After this one more system came into existence which was called ABS (Anti- Lock braking system) which took braking efficiency to even higher level.

Anti Lock Braking System (ABS) is used to avoid locking of the wheels during sudden braking. It is very useful in the situation when the road surfaces are very slippery and due to which it is very difficult for the driver to maintain control of the vehicle. ABS avoids wheel locking and minimizes chances of the wheels to skid under various road conditions. In other words ABS is an electronically operated system which helps the operator (driver) to have control of the vehicle during emergency braking and thus preventing the wheels to get lock during braking. If in worst case the wheels get locked up then it will be very difficult for the vehicle to gain stability which can lead to severe accident and cause injuries to the passengers. Hence in simple words the function of an ABS is to maintain stable condition even under sudden braking or extreme slippery conditions. ABS work only when the wheels are about to skid, apart from that the other function of an ABS is to maintain brake pressure just below the point where it wheel starts to lock up.[ 2]

ABS was initially designed to stop airplanes but now-a-days it is a useful system which is used in every vehicle because its ability to stop the vehicle in minimum possible distance with no extra effort. A typical ABS consists of all standard components i.e. A hydraulic modulator, speed sensors and an ECU (Electronic Control Unit). This electronic control unit is going to be replaced by new component called COMPACT RIO which is designed and developed by NATIONAL INSTRUMENTS which is the aim of the project and how it is going to affect in better way than the ECU. The angular velocity of the wheels and the acceleration is measured with the help of these sensors. These sensors are connected to the ECU who sends signals to the ECU in the form of pulse which helps in understanding the ECU whether the wheels are going to lock. If it is going to lock the ECU sends the signal to hydraulic modulator to decrease the pressure in the brake cylinder to avoid locking, after the wheels are prevented from locking the cylinder in the brake cylinder is increased again.

Recently organized study and design has been helped significantly by modern software tools which combine with an interactive user environment and suite to control the designer. This can be very well explained by the use of block diagrams which shows the implementation of control design which are suited with system and control modeling techniques. Due to combining of hardware with the software to form a controlled model has made commercial off the shelf products available and affordable for wide range of customers. These products can extensively accelerate the development process which is one of the main reasons for its popularity and wide application. LABVIEW is one of the product which is has got wide range of applications such as in the field of control prototyping to get an effective solution for any problem.[3]

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FIGURE : SITUATION WITH ABS AND WITHOUT AN ABS [9]

MODELLING

COMPACT RIO

SIGNAL

TEST AND VALIDATION

HARDWARE IN LOOP

CONTROL PROTOTYPING

EVALUATION

CONTROL PROTOTYPING SHOWING ENABLING TECHNOLOGIES

The modeling and simulation is done by using software called LABVIEW which is produced by National Instruments which generate Virtual Instrument which can be made using Lab view real time environment. Labview is very widely used real time software which has a user interface which helps in carrying out test and evaluation. Apparently users which are familiar with labview are very much able to simulate, implement and test the controllers in the single platform which helps in testing and measurement.

Interfacing to physical hardware, data acquisition, signal processing and other facilities available in labview are skilled in a steady manner.

Coding is done to operate the braking system. A proper coding is to be developed on the basis of which the command is to be send to the Compact Rio for it to function. The basic signal will be send with the help of a algorithm which will be developed particularly for compact rio and which will compatible with every device [3]

Hardware in loop is done in order to evaluate and validate component during the development of new system. HIL (Hardware in Loop) helps in testing the prototypes while communicating with the software models that simulate the rest of the vehicle system, rather than testing these components in complete system setups. HIL helps in replacing the rest of the vehicle with computer running software which at a great extent reduces the size and the complexity of application and increases the flexibility and the rate of running many test conditions.

All the new components which are to be developed are modeled into particular software prior to the development of any prototype.

Labview Real Time software helps us to use labview graphical programming to create new with accurate timing and complete dependability that runs on fixed hardware targets. Labview Real Time can be compatible with wide variety of I/O devices including FPGA and Compact RIO hardware.[3]

FPGA (Field Programming Gate Array) uses labview implanted technology to extend graphical development and target programmable field gate array on I/O devices like Compact Rio. Labview is particularly suited for FPGA programming because it represents data flow very clearly. Labview FPGA model helps us how to create custom measurements and control hardware without any low level hardware explanation.

I/O (Input Output) device in this case is a RIO hardware which is going to replace ECU. National Instruments delivers a spontaneous solution for incorporating the flexibility of FPGA technology into measurements and control systems. Using Labview one can define logic in FPGA chips that are surrounded across the family of re-configurable I/O (RIO). In general labview allows us to join together the devices such as image acquisition, motion control and industrial communications such as CAN (Control Area Network) and R3232

National Instruments Compact Rio is a platform centered on Rio technology which gives small scale industries. A rugged and modular stage for delivering high performance I/O and unmatched flexibility for the off the shelf fixed systems. We can use National Instruments Compact Rio to build an implanted system for applications such as in-vehicle data acquisition, NVH (Noise Vibration and Harshness) testing and embedded machine control systems. We can develop our own custom Compact RIO modules by using this Compact Rio module kit. This rugged National Instrument Compact Rio system is a industrially certified which is designed to carry greater than 50g of shock at temperature range of -40Ëš C to 70Ëš C.

COMPACT RIO hardware is a product of National Instruments which is a high-performance programmable automation controller (PAC) which is differentiated by a FPGA at its architecture.

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FIGURE : COMPACT RIO [3]

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FIGURE 4: ELECTONIC CONTROL UNIT [6]

COMPACT RIO hardware system is widely used for rapid prototyping and hardware in loop simulation of controllers under development. At first before manufacturing the controller the control algorithm should be tested after that it should be validated. This is done by the use of hardware in loop testing.

FPGA is a reprogrammable silicon chip. Mainly FPGAs are widely used due to their performance and reliability of custom hardware. FPGAs can be learned through labview without any guidance of an expertise. Labview is a powerful graphical programming language with many built in control, analysis, communication and logging functions. Compact Rio is fully programmable with labview which included FPGA real time processor.[8]

COUNTER SPECIFIC FEATURES ( CRIO)

1mhz counting on eight channels

32 bit count register with programmable terminal count

Configurable terminal count and terminal count behavior

Configurable count edge source and gate

Period PWM and frequency measurements with configurable database

PWM (PULSE WIDTH MODULATOR) is commonly used in many automotive industries. In this the frequency is kept constant and the information is send by the duty cycle. With the help of labview FPGA module we can arrange any of the digital lines on the Compact Rio to read and write PWM signal according to the application needed.[8]

PWM FEATURES:

Eight output channels

Per channel duty cycle and period configuration[8]

Compact Rio Scan Mode is basically designed for applications requiring synchronous I/O updates at rates of up to 1 kHz. We can use this scan mode for various purposes like initial setup system, performance monitoring and advance troubleshooting. This scan engine runs above time critical or between time critical or time structures which can be configured by the operator. After finishing every scan we can see that all the I/O variables are updated. We can block the I/O which reads and writes whenever we want and can allow I/O to read and write the programs accordingly. These I/O variables are also published in the network to make them available for reading and writing in the main computer, test panels etc. [5]

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FIGURE 5: COMPACT RIO SCAN MODE [5]

DEVICE

DEVICE

RIO

I/OCAN BUS (Control Area Network) allow the micro-controllers and devices to communicate with each other within the vehicle. For this project we can use the CAN bus for communicating the Compact Rio with various sensors of the system for e.g. WHEEL SENSOR of an Anti lock braking system. It is a cheap and durable network which allows many devices to communicate with each other. A Compact Rio can use it as an advantage by using a single CAN interface rather than having both analog and digital inputs to every component in the system. This will help in reducing the weight and the overall cost of the vehicle. In this all the devices under CAN network has CAN controller chips and it is therefore called intelligent system due to which all the devices can see all the messages which are transmitted. Each device has an authority to decide which messages are related and which messages need to be sorted out. Every messages

holds a precedence, so for e.g. if two nodes try to send messages at same time, the one with high precedence passes through and the one with the lower precedence gets delayed.[4]

As the ECU is going to be replaced by Compact Rio there is going to be some changes in the block diagram too. Basically the diagram will be described as the Compact Rio connected to the FPGA real time module through cables or wires which will be then connected to the hydraulic modulator through respective connections which will receive the input data from the Compact Rio when to reduce the pressure in the brakes depending on which wheel is about to get locked and will start skidding. Whose one end will be connected to the wheel sensors which are connected to the wheels. Wheels sensors one end will be connected to the Compact Rio so that accordingly it will receive the signal from the Compact Rio depending upon the operating conditions. This is a simple setup which I have decided to connect the various devices and sensors for proper data collection and signal processing.

Then the use of CAN bus can be done to communicate with the components within the system. Even pulse width modulator can be used to read the signal accordingly which will be sending the information with the help of FPGA module.

LABVIEW FPGA MODULE

HYDRAULIC MODULATOR

COMPACT RIO

TO THE BRAKE

WHEEL SENSORS

A TYPICAL ASSUMED BLOCK DIAGRAM USING COMPACT RIO AND THE CONNECTIONS

The above diagram shows the various connection of the anti-lock braking system with the use of compact rio which is going to control the whole system. The connection will be the same as shown in the figure the only thing will be solenoids which will be used to hold, release and re-apply the hydraulic pressure to the brakes.

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