Complet Documnetation for Smart Assistant Application for Disabled Person
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GroupC_ABS.pptx
1. ANTILOCK BRAKING SYSTEM
MODELING AND DEVELPOMENT
Vehicle Dynamics (ME5670)
Siva Teja Golla (ME14MTECH11025)
Harshad Keskar (ME14MTECH11027)
Mohini Kale (ME14MTECH11029)
Nikhil Mhaske (ME14MTECH11030)
Sukanya Joshi (ME14MTECH11037)
ANTILOCK BRAKING SYSTEM 1
Indian Institute of Technology, Hyderabad
2. INTRODUCTION
ANTILOCK BRAKING SYSTEM 2
โข 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 driver inputs while braking, preventing the wheels from locking up
and avoiding uncontrolled skidding.
โข ABS generally offers improved vehicle control and decreases stopping distances
on dry and slippery surfaces.
โข ABS modulates the brake line pressure independent of the pedal force, to bring
the wheel speed back to the slip level range that is necessary for optimal
braking performance.
3. PROJECT OUTLINE
ANTILOCK BRAKING SYSTEM 3
โข Objectives of ABS
โข Components of ABS
โข Working of ABS
โข Mathematical model
โข System model
โข Results
โข Conclusion
โข References
4. OBJECTIVES OF ABS
ANTILOCK BRAKING SYSTEM 4
โข To reduce stopping distance
1. The road surface type and conditions can be inferred from the vehicle's
braking pressure, wheel slip measurements, and deceleration rate
comparisons.
2. The wheel slip is regulated so that the road adhesion coefficient is
maximized. By keeping all of the wheels of a vehicle near the maximum
friction coefficient, an antilock system can attain maximum fictional
force
3. In turn, this strategy leads to the minimization of the vehicle stopping
distance.
5. ANTILOCK BRAKING SYSTEM 5
โข Stability
1. A locked-up wheel generates a reduced braking force, smaller than the peak
value of the available adhesion between tires and road. A locked-up wheel
will also lose its capability to sustain any lateral force. This may result in the
loss of vehicle stability.
2. The basic purpose of a conventional ABS system is thus to prevent any
wheel from locking and to keep the longitudinal slip in an operational range
by cycling the braking pressure.
6. ANTILOCK BRAKING SYSTEM 6
โข Steerability
1. Good peak frictional force control is necessary in order to achieve
satisfactory lateral forces and, therefore, satisfactory steer-ability.
2. If an obstacle appears without warning, emergency braking may not be
sufficient. When the wheels are locked, car no longer respond to the driverโs
steering intention.
3. With ABS car remains steerable even during emergency braking, and thus the
obstacle can be safely avoided.
7. COMPONENTS OF ABS
ANTILOCK BRAKING SYSTEM 7
The primary components of the ABS braking system are:
โข Electronic control unit (ECU)
1. It receives signals from the sensors in the circuit and controls the brake
pressure at the road wheels according to the data analysed by the Unit.
2. ECU assists the vehicle operator to prevent wheel lockup by regulating the
wheel slip.
โข Hydraulic control unit or modulator
1. It receives operating signals from the ECU to apply or release the brakes
under ABS conditions.
2. It executes the commands using three solenoid valves connected in series
with the master cylinder and the brake circuits- one valve for each front
wheel hydraulic circuit, and one for both of the rear wheels. Thus brakes can
be actuated by controlling hydraulic pressure.
8. ANTILOCK BRAKING SYSTEM 8
โข Power booster and master cylinder assembly
1. It is activated when the driver pushes down on the brake pedal. The master
cylinder transforms the applied pedal force into hydraulic pressure which
is transmitted simultaneously to all four wheels.
2. It provides the power assistance required during braking.
โข Wheel sensor unit
1. Speed sensors are comprised of a magnet wrapped in a coil and a toothed
sensor ring. An electrical field given off by the contact between the magnet
and the toothed ring creates a AC voltage.
2. The voltage frequency is directly proportional to the wheel's rotational
speed.
3. It monitors the rotational speed of the wheel and transmits this data to the
ABS control module.
9. WORKING OF ABS
ANTILOCK BRAKING SYSTEM 9
โข If a wheel-speed sensor signals a lock up - the ECU sends a current to the
hydraulic unit. This energizes the solenoid valve. The action of the valve
isolates the brake circuit from the master cylinder. This stops the braking
pressure at that wheel from rising, and keeps it constant. It allows wheel
velocity to increase and slip to decrease.
โข When the velocity increases, ECU re-applies the brake pressure to restrict
the wheel slip to a particular value.
โข Hydraulic control unit controls the brake pressure in each wheel cylinder
based on the inputs from the system sensor. This in result controls the wheel
speed.
10. MATHEMATICAL MODEL
ANTILOCK BRAKING SYSTEM 10
โข Wheel slip:
When the braking action is initiated, a slippage between the tire and the
contacted road surface will occur, which make the speed of the vehicle to be
different from that of the tire.
โข The longitudinal slip is defined as
๐ =
๐๐๐๐ ๐ผ โ ๐๐ ๐ค
๐๐๐๐ ๐ผ
The side slip angle is
๐ผ = ๐ก๐๐โ1 ๐๐ ๐ฆ
๐๐ฅ
Force and velocity components on tyre
11. ANTILOCK BRAKING SYSTEM 11
โข Vehicle Dynamics
According to Newton's second law, the equation of motion of the
simplified vehicle can be expressed by,
๐๐ก๐ = โ๐น๐ก โ ๐น๐
The road friction force is given by Coulomb law
๐น๐ก = ๐๐
The total mass of the quarter vehicle can be written as
๐๐ก = ๐๐ก๐๐๐ +
๐๐
4
Thus, the total normal load cm be expressed by
๐ = ๐๐ก๐ โ ๐น๐
๐น๐ is the longitudinal weight transfer load due to braking
13. ANTILOCK BRAKING SYSTEM 13
โข Wheel dynamics
According to Newton's second law, the equation of motion at wheel
level for the rotational DOF is given by,
๐ฝ๐ค๐ = โ๐๐ + ๐น๐ก๐ ๐ค
15. SYSTEM MODEL
ANTILOCK BRAKING SYSTEM 15
Assumption: Only a linear model was considered and does not include actual road
conditions. The system here is modelled only for straight line braking.
16. INPUT PARAMETERS FOR SIMULINK MODEL
ANTILOCK BRAKING SYSTEM 16
Gravitational constant ๐ = 32.18 ๐๐ก/๐ 2
Initial velocity of vehicle ๐ฃ0 = 88 ๐๐ก/๐
Wheel Radius ๐ ๐ = 1.25 ๐๐ก
Mass of vehicle ๐ = 50 lbs
Maximum Braking Torque ๐๐๐๐๐ฅ
= 1500 ๐๐๐ โ ๐๐ก
Hydraulic Lag ๐๐ต = 0.01 ๐
Moment of Inertia ๐ฝ๐ค = 5 ๐๐ก4
24. CONCLUSION
ANTILOCK BRAKING SYSTEM 24
โข It is inferred that ABS improves the braking performance.
โข The stopping distance after using ABS system has considerably reduced.
โข The error in slip and desired slip is used to manipulate brake pressure in brake
cylinder.
25. REFERENCES
ANTILOCK BRAKING SYSTEM 25
โข Tianku Fu,โModelling and performance analysis of ABS system with non-linear controlโ,
2000.
โข Tobias Eriksson,โCo-simulation of full vehicle model in Adams and anti-lock brake system
model in Simulinkโ, 2014.