speed control design for a vehicle system using fuzzy logic

8/11/2019 Speed Control Design for a Vehicle System Using Fuzzy Logic

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Speed control design for a vehicle system using fuzzy logic

.

Introduction

Engine and other automobile systems are increasingly controlled electronically. This has led to

improved fuel economy, reduced pollution, improved driving safety and reduced manufacturing

costs. However the automobile is a hostile environment: especially in the engine compartment,

where high temperature, humidity, vibration, electrical interference and a fine cocktail of

potentially corrosive pollutants are present. These hostile factors may cause electrical contacts to

deteriorate, surface resistances to fall and sensitive electronic systems to fail in a variety of modes.

Some of these failure modes will be benign, whereas others may be dangerous and cause accidents

and endanger to human life.

A cruise control system, or vehicle speed control system can keep a vehicles speed constant on

long runs and therefore may help prevent driver fatigue !"#$%. &f the driver hands over speed

control to a cruise control system, then the capability of the system to control speed to the set

value is 'ust as critical to safety as is the capability of the driver to control speed manually. So the

cruise control system design is imperative and important to an automobile.

. Design requirements

a(. )esigning controller using fu**y logic+

b(. aking the automobile-s speed keep constant.

. Model description of the automobile

The dynamics of the automobile !% are given as follows

"/ ( / / ( / ((

pt A t d f t

m = +&

/ ( / / ( / ((f t f t u t

= +&

0here u is the control input / 1u > represents a throttle input and 1u < represents a brake

input(, 211m kg= is the mass of the vehicle, 1.2pA = " "3Ns m is its aerodynamic drag,

11d N= is a constant frictional force, fis the driving3braking force, and 1." = sec is

saturated at 111N (.

0e can use fu**y control method to design a cruise control system. 4bviously, the fu**y cruise


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control design ob'ective is to develop a fu**y controller that regulates a vehicle-s speed / (t to a

driver#specified value / (d t .

. Speed control design using fuzzy logic

5u**y control logic and neural networks are other e6amples of methodologies control

engineers are e6amining to address the control of very comple6 systems. A good fu**y control

logicapplication is in cruise control area.

( )esign of 7& fu**y controller

Suppose that we wish to be able to track a step or ramp change in the driver#specified speed

value / (d t very accurately. A 87& fu**y controller9 can be used as shown in 5ig. . &n 5ig. , the

fu**y controller is denoted by + 1, g g and "g are scaling gains+ and / (b t is the input of the

integrator.

5ig. Speed control system using a 7& fu**y controller

5ind the differential euation that describes the closed#loop system. ;et the state be

" 2! , , % ! , , %T T

x x x x f b= = and find a system of three first#order ordinary differential euations

that can be used by the ?m3sec /@1.2 mph( for 1 1t and / (d t "" m3sec

/@." mph( for 1 21t .

b: Test input " makes / (d t >?m3sec /@1.2 mph( for 1 1t and / (d t increases

linearly /a ramp( from ? to "" 3secm by "$sect = , and then / ( ""d t = for "$ 21t .

c: Test input 2 makes / (d t >"" for 1 t and we use /1(x as the initial condition /this

represents starting the vehicle at rest and suddenly commanding a large increase speed(.

Bse /1( !?,AC.","1%Tx = for test input and ".


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)esign the fu**y controller to get less than "D overshoot, a rise#time between $ and C sec,

and a settling time of less than ? sec /i.e., reach to within "D of the final value within ? sec( for

the 'ump from ? to "" 3secm in 8test input 9 that is defined above. Also, for the ramp input

/8test input"9 above( it must have less than mph /1.@@C 3secm ( steady#state error /i.e., at the

end of the ramp part of the input have less than mph error(. 5ully specify the controller /e.g., themembership functions, rule#base defu**ification, etc.( and simulate the closed#loop system to

demonstrate that it performs properly. 7rovide plots of / (t and / (d t on the same a6is and / (u t

on a different plot. 5or test input 2 find the rise#time, overshoot, "D settling time, and steady#state

error for the closed#loop system for the controller that you designed to meet the specifications for

test input and ". Bsing the


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5ig. 2 ehicle speeds and the output of fu**y controller using test input "

Test input 2

5ig. @ ehicle speeds and the output of fu**y controller using test input 2

"( )esign of 7) fu**y controller

Suppose that you are concerned with tracking a step change in / (d t accurately and that you

use the 7) fu**y controller shown in 5ig. $. To represent the derivative, simply use a backward

difference

/ ( / (/ ( e t e t hc th

=


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0here h is the integration step si*e in your simulation /or it could be your sampling period in an

implementation(.

5ig. $ Speed control system using a 7) fu**y controller

)esign a 7) fu**y controller to get less than "D overshoot, a rise#time between C and 1 sec.

and a settling time of less than 1 sec for test input defined in a(. Also, for the ramp input / test

input " in (( it must have less than mph steady#state error to the ramp /i.e., at the end of the

ramp part of the input, have less than mph error(.

5ully specify your controller and simulate the closed#loop system to demonstrate that it

performs properly. 7rovide plots of / (t and / (d t on the same a6is and / (u t on a different plot.

&n the simulations, the


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5ig. C ehicle speeds and the output of fu**y controller using test input "

Test input 2

5ig. ? ehicle speeds and the output of fu**y controller using test input 2

. Summary

To keep an automobile-s speed constant, a speed control design method using fu**y logic is

presented. 7& fu**y controller and 7) fu**y controller design schemes are given to regulate avehicle-s speed to a driver#specified value. The simulation results show the validity and of the


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proposed techniue.

The control design procedure can be summari*ed as follows:

odeling and performance ob'ectives

Gasically, the role of modeling a fu**y control design is uite similar to its role in

conventional control system design. &n fu**y control there is a more significant emphasis on the

use of heuristics. onventional feedback controller design entails constructing a controller to meet

the closed#loop specifications /such as disturbance re'ection properties, insensitivity to plant

parameter variations, stability, overshoot, steady#state error et al(, which is also applied to fu**y

control design.

" 5u**y controller design

5u**y control design essentially amounts to /( choosing the fu**y controller inputs and

outputs /"( choosing the preprocessing that is needed for the controller inputs and possibly

postprocessing that is needed for the outputs, and /2( designing the four components of the fu**y

controller: /a( The fu**ification interface simply modifies the inputs so that they can be interpreted

and compared to the rules in the rule#base. /b( The 8rule#base9 holds the knowledge, in the form of

a set of rules, of how best to control the system. /c( The inference engine evaluates which control

rules are relevant at the current time and then decides what the input to the plant should be. And

/d( the defu**ification interface converts the conclusions reached by the inference engine into the

inputs to the plant.

2 omputer simulation

To prove the effectivity of the controller design and check up whether the design

reuirements are reali*ed or not.

References

!% =. . 7assino and S. Iurkovich/C(. 5u**y control, st edn, Addision 0esley ;ongman,

olifornia.

!"% 0ard, ). . Gerlit* complete guide to cruising and cruise ships "111. 7rinceton, Jew

Kersey: Gerlit* 7ublishing ompany.

!2% &oannou, 7.A.+ hien, .. LAutonomous &ntelligent ruise ontrol,L &EEE Trans. on

ehicular Technology, @"/@( :F$C M FC", 2.

!@% ayr,


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&ntelligent Transportation Systems,pp. C1 M C$, .
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speed control design for a vehicle system using fuzzy logic

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