IJTERI
ISSN (Online): 2456-4788
INTERNATIONAL JOURNAL FOR TECHNICAL EDUCATION AND RESEARCH INNOVATIONS
JANUARY 2017 | IJTERI | Volume 1 Issue 4 |
A REVIEW ON ANTILOCK BRAKING SYSTEM DYNAMICS AND ITS SAFETY
FEATURES
Shubham yadav
Student, Mechanical Engineering, Kirodimal Institute of Technology, Raigarh (C.G.).
ABSTRACT
The control of an antilock braking system is difficult problem due to the existence of non linear dynamics and
uncertainties of its characteristics. To overcome these issues, in the work, a dynamic non-linear controller is
proposed, based on a nonlinear observer. The dynamic controller ensures exponential convergence of the state
estimation, as well as robustness with respect to parameter variations. In this paper the methods used in design
of ABS is discussed.
Keywords- ABS, Dynamics, Formulation linear and nonlinear system, Safety features
1. INTRODUCTION
A brake is an appliances used to apply frictional resistance to maintain body to stop or retard it by absorbing its
kinetic energy. In general, in all types of motion, there is always some amount of resistance which retards the
motion and is sufficient to bring the body to rest. Anti-lock braking system (ABS) is an automobile safety
system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to
drivers inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding
uncontrolled skidding. It is an automated system that uses the principles of threshold braking and cadence
braking which were practiced by skillful drivers with previous generation braking systems. It does this at a
much faster rate and with better control than driver could manage. ABS generally offers improved vehicle
control and decreases stopping distances on dry and slippery surfaces. However, on loose gravel or snowcovered surfaces, ABS can significantly increases braking distance, although still improving vehicle control.
ABS is recognized as an important contribution to road safety as it is designed to keep a vehicle steerable and
stable during heavy braking moments by preventing wheel lock. It is well known that wheels will slip and
lockup during severe braking or when braking on a slippery road surface. The objective of ABS is to manipulate
the wheel slip so that a maximum friction is obtained and the steering stability (also known as the lateral
stability) is maintained. That is, to make the vehicle stop in the shortest distance possible while maintaining the
directional control. The ideal goal for the control design is to regulate the wheel velocity.The basic function of
the ABS is prevention of wheel lockup and thus maintains both, steerability and vehicle stability assuring at the
same time shorter stopping distances as compared to locked-wheel braking on most road surfaces. Malfunction
caused by aging of the ABS components or insufficient maintenance of the vehicle can result in a loss of
braking power. A sufficient braking capability is one of the most important qualities a vehicle must have.
Fig.1 Typical Layout of ABS components
1.
ABS control module and hydraulic control unit(ABSCM & H/U)
2.
Two-way connector
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IJTERI
ISSN (Online): 2456-4788
INTERNATIONAL JOURNAL FOR TECHNICAL EDUCATION AND RESEARCH INNOVATIONS
JANUARY 2017 | IJTERI | Volume 1 Issue 4 |
3.
Diagnosis connecter
4.
ABS warning light
5.
Data link connector (for SUBARU select monitor)
6.
Transmission control module
7.
Tone wheels
8.
ABS wheel speed sensor
9.
Wheel cylinder
10. G sensor
11. Stop light switch
12. Master cylinder
13.
14. Brake & EBD warning light
15. Lateral G sensor
II. PRINCIPLE OF ANTILOCK BRAKING SYSTEM
When the brake pedal is depressed during driving, the wheel speed decreases and the vehicle speed
does as well. The decrease in the vehicle speed, however is not always proportional to the decrease in the wheel
speed. The non-correspondence between the wheel speed and vehicle speed is called “slip”.
Slip, S= (V- ωR)/ V
Where ω, R, and V denotes the wheel angular velocity, the wheel rolling radius, and the vehicle forward velocity
respectively.
and the magnitude of the slip is expressed by the “slip ratio” which is defined as follows,
Slip ratio = (vehicle speed - wheel speed)/vehicle speed x 100%
When the slip ratio is 0%, the vehicle speed corresponds exactly to the wheel speed and when it is 100%, the
wheels are completely locking (rotating at zero speed) while the vehicle is moving.
III. ABS FORMULATION
The dynamic equation of ABS are the result of Newton‟s law applied to the wheels and the vehicle. The vehicle
dynamic is determined by summing the total forces applied to the vehicle during a braking operation to obtain.
Vv(t) = -[4Ft(t)+BvVv(t)+Fθ(θ)]/Mv
Ww(t) =[-Tb(t)-Bwww(t)+Tt(t)]/Jw
Fig.2 Quarter car forces and torques
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IJTERI
ISSN (Online): 2456-4788
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Where,
Vv(t) = Velocity of the vehicle
Mv
= Mass of the vehicle
Bv
= Vehicle viscous friction
Ft(t) = Tractive force
Fθ(θ) = Vertical force applied to the car
Bw = Viscous friction of the wheel
Jw = Rotation inertia of the wheel
Tb(t) = Braking torque
Tt(t) = Torque generated due to slip between the wheel and the road surfaces
The expressions of different forces are given as follows:Fθ(θ)= Mv g sin(θ)
Ft(t)= µ(λ)Nv(θ)
Nv(θ)= Mvg cos(θ)/4
Tt(t)= RwFt (t)
Where θ is the angle of inclination of the road, g is the gravitational acceleration constant, Nv(θ) is the vertical
force applied to the wheel and µ(λ) is the coefficient of friction.
Note that
wv(t) =Vv(t)/R w
Is the angular velocity, where Rw is the radius of the wheel.
The longitudinal slip is defined by
λ (t)= [wv(t) - ww(t)]/wv(t)
It describes the normalized difference between the angular velocity of the wheel. The slip value of λ=0
characterizes the free motion of the wheel where no friction force Ft is exerted. If the slip attains the value λ=1,
then the wheel is locked (Ww=0).
IV. FRICTION COEFFICIENT
It characterizes the road and has the properties µ(λ=0)=0 and µ(λ)>0 for λ=0. Its typical qualitative dependence
on longitudinal slip λ is shown in figure 3.1. It shows the how the friction coefficient µ increases with slip λ up
to a value λ0, where it attains its maximum value µH. For higher slip values, the friction coefficient will decrease
to a minimum µG where the wheel is locked and only the sliding friction will act on the wheel. The longitudinal
force gets smaller as side slip angle is increased.
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IJTERI
ISSN (Online): 2456-4788
INTERNATIONAL JOURNAL FOR TECHNICAL EDUCATION AND RESEARCH INNOVATIONS
JANUARY 2017 | IJTERI | Volume 1 Issue 4 |
Fig.3 Dependence of friction on the road
Fig.4 Friction coefficient
CONCLUSION
After completing the study of this review paper the reader should be able to understand the various information
about antilock brake system. ABS control is highly nonlinear control problem due to the complicated
relationship between its components and parameters. Anti-lock brake systems (ABS) - generally also referred to
as anti-lock systems (ALS) - are designed to prevent the vehicle wheels from locking as a result of the service
brake being applied with too much force, especially on slippery road surfaces. The idea is to maintain cornering
forces on braked wheels to ensure that the vehicle or vehicle combination retains its driving stability as far as
physically possible. The available power transmission or grip between tyres and carriageway should also be
utilised as far as possible to minimise the braking distance and maximise vehicle deceleration. Many different
control methods for ABS have been developed and research on improved control methods is continuing.
REFERENCES
[1] H. Mirzaeinejad, M. Mirzaei, „A novel method for non-linear control of wheel slip in anti-lock braking
systems‟, Control Engineering Practice vol. 18, pp. 918–926, 2010
[2] S. Ç.baslamisli, I. E. Köse and G Anlas, „Robust control of anti-lock brake system’, Vehicle System
Dynamics, vol. 45, no. 3, pp. 217-232, March 2007
[3] S. 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
[4] K.Z. Rangelov, SIMULINK model of a quarter-vehicle with an anti-lock braking system, Master’s Thesis
Eindhoven: Stan Ackermans Institute, 2004. Eindverslagen Stan Ackermans Institute, 2004102
[5] A. B. Sharkawy,„Genetic fuzzy self-tuning PID controllers for antilock braking systems‟ Engineering
Applications of Artificial Intelligence, vol. 23, pp. 1041–1052, 2010.
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