ANTI-LOCK BRAKING SYSTEM

USING FUZZY LOGIC

Guide: Mr. Arun PrasadPresented by: Janish J Arakkal

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Contents Anti-lock Braking System Why do we need ABS? Operation Components Working How ABS Works ABS Control Fuzzy Logic Fuzzy Control Fuzzy Control of ABS The Fuzzy-ABS Algorithm Advantages And Disadvantages of ABS Conclusion Reference

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Anti-Lock Braking System(ABS)

ABS is a safety system which prevents the wheels on a motor vehicle from locking up (or Skidding) while braking.

ABS prevent vehicle from skidding when applied brakes in any road condition keeping the vehicle speed and wheel speed at a same level.

It helps the driver to head the nose of the vehicle to a desired location even when full brakes are applied.

ABS offers improved vehicle control and decreases stopping distances on dry and especially slippery surfaces.

The aim of an ABS is to decelerate the vehicle in the best possible manner i.e. to Minimize the braking distance while maintaining the Stability.

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Why do we need ABS? Stopping a car in a hurry on a slippery road can be

very challenging.When you apply brakes on such road vehicle has a greater chance of getting skidded. If the vehicle starts to skid, there is no way to control the nose direction using the steering wheel.

The main disadvantage of ordinary brakes is that these brakes are imprecise and the vehicle is difficult to control. Locking of brake can be caused due to the high brake pressure applied. The wheel lockup causes instability of the vehicle.

Anti-lock Brake improves the controllability of vehicles in compare with brake systems lacking ABS

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Operation Some drivers using the same technique

to stop the vehicle without losing control in slippery roads.

What exactly happen there is once the vehicle starts skidding they release the brake pedal, so that they have the vehicle in control. After that the driver applies the brake again.

ABS is an electronic braking system can perform the above mentioned task more accurately and efficiently.

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Components Of ABS The 4 main

components of ABS

A. The Speed Sensor

B. The Controller

C. The Hydraulic Unit With Pressure Releasing Valves

D. The Brake Pipe

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Speed Sensor: The anti-lock braking 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: They work with the controller and the pump to add or release pressure from the individual wheels brakes to control the braking

Pump: 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 an ECU type unit in the car which receives information from each individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the controller will then limit the brakeforce and actuates the braking valves on and off.

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How Abs Works

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Working1) The controller monitors the speed sensors at

all times.2) Right before a wheel locks up, it will

experience a rapid deceleration.3) The ABS controller under such a rapid

deceleration reduces the pressure to that brake until it sees an acceleration

4) Then it increases the pressure until it sees the deceleration again.

5) It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up.

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ABS Control

Many different control methods for ABS systems have been developed. These methods differ in their theoretical basis and performance under the changes of road conditions. An anti-lock braking system control is a rather difficult problem due to its strongly nonlinear and uncertain characteristics. To overcome these difficulties, robust control methods should be employed such as a Fuzzy control.

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Fuzzy Logic!

Fuzzy logic is a mathematical technique for dealing with imprecise data and problems that have many solutions rather than one. Although it is implemented in digital computers which ultimately makes yes-no decisions, fuzzy logic works with ranges of values, solving problems in a way that more resembles human logic.

FUZZIFICATION - The crisp input has to be converted to a fuzzy number.

DEFUZZIFICATION- It is the process of producing a quantifiable result in fuzzy logic.

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Fuzzy ControlFuzzy control aims at replacing old techniques and solving the whole problem with artificial intelligence methods. Fuzzy controllers are very simple conceptually.

They consist of An input stage -maps sensor or other inputs to

the appropriate membership functions and truth values.

A processing stage - invokes appropriate rule and generates a result for each, then combines the results of the rules

An output stage - converts the combined result back into a specific control output value

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Fuzzy Control Of ABS

ABS which is a non-linear system may not be easily controlled by classical control methods.

An intelligent fuzzy control method is very useful for this kind of non linear system.

Fuzzy ABS require more complex control constructs than simple “if-then” rules. In “if-then” rules, input variables marks directly to the output variables. But in fuzzy control it is possible to build a control with intermediate fuzzy variables.

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Flow chart showing the control of the ABS

Wheel Slip

Pressure

Brake Actuato

r

Wheel Accelerato

n

Fuzzy Interference

System

Vehicle Velocit

y

Wheel Speed

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The Fuzzy-ABS Algorithm The Fuzzy-Controller uses two input values: the wheel

slip SB:

and the wheel acceleration:

The input variables are transformed into fuzzy variables slip and wheel acceleration by the fuzzification process. Both variables use seven linguistic values, the slip variable is described by the terms

Slip = {zero, very small, too small, smaller than optimum, optimum, too large, very large},

and the acceleration by dvwheel/dt = {negative large, negative medium,

negative small, negative few, zero, positive small, positive large}.

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As a result of two fuzzy variables, each of them having seven labels, 49 different conditions are possible. The rule base is complete that means, all 49 rules are formulated and all 49 conditions are allowed.

The two fuzzy input values slip and wheel acceleration can be mapped to the fuzzy output value pressure. The labels for this value are:

Pressure = {positive fast, positive slow, zero, negative slow, negative fast}

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Membership Functions

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Advantages of Abs

Reduce Accidents Stopping on slippery roads Better control while emergency braking improve steering in an evasive maneuver Increased tyre life Lower insurance costs

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Disadvantages of ABS

Unfortunately, ABS brakes do not make a vehicle stop quicker

Expense Inconsistent stop times Delicate systems

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CONCLUSION

Fuzzy ABS has reduced the percentage of road crashes by a considerable amount. Experts predict that 35% to 50% of all cars built worldwide in five years will have ABS as standard equipment. Though it has many advantages, there are few disadvantages such as increased braking distance in snow/icy regions at present. These drawbacks can be overcome in future by fuzzy controlled ABS.

So, next time buy a vehicle with ABS

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ReferenceS

[1] Yonggon Lee and Stanislaw H. Zak, “Designing a Genetic Neural Fuzzy Antilock-Brake-System Controller,” IEEE TRANSACTIONS ON EVOLUTIONARY COMPUTATION, VOL. 6, NO. 2, APRIL 2002

[2] Seibum B. Choi, “Antilock Brake System With a Continuous Wheel Slip Control to Maximize the Braking Performance and the Ride Quality,” IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL. 16, NO. 5, SEPTEMBER 2008

[3] Chih-Min Lin and Chun-Fei Hsu, “Self-Learning Fuzzy Sliding-Mode Control for Antilock Braking Systems,” IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL. 11, NO. 2, MARCH 2003

[4] Chih-Min Lin and Chun-Fei Hsu ,”Neural-Network Hybrid Control for Antilock Braking Systems,” IEEE TRANSACTIONS ON NEURAL NETWORKS, VOL. 14, NO. 2, MARCH 2003

[5] William K. Lennon and Kevin M. Passino, “Intelligent Control for Brake Systems,” IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY

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Thank you