Design of SlidingMode Controller Based Antilock Braking System of a Vehicle
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Date
2017-04
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Addis Ababa University
Abstract
Anti-lock braking system (ABS) is the most common safety system in the vehicles, which works
to increase the generated braking force between the tire and the road surface for enhancing
passenger safety specifically related to accident avoidance. However, designing an ABS is a
challenging task considering the fact that it is highly nonlinear and a time varying system. The
interaction between the tires and the road surface, the dynamics of the whole vehicle and the
characteristics of key components in ABS are all nonlinear and time varying. Due to the nonlinearities
of the brake actuation system, robust braking control system with a faster response
is required to handle even sudden, extreme variations in driving conditions with little loss of
traction and steering ability.
In this thesis, out of the robust controlling mechanisms, a sliding mode controller based antilock
braking systemof a vehicle is introduced. The objective of this SMC based ABS is to keep
the wheel slip at an ideal value so that the tire can still generate lateral and steering forces as
well as shorter stopping distances in order to prevent the controlledwheel frombecoming fully
locked. In order to control the system based on wheel slip, a Quarter car in terms of wheel slip
is modelled and the model is validated by using open loop response analysis by usingMATLAB.
Then a controller is designed and implemented using MATLAB. During our controller design,
in order to resolve the drawback of SMC i.e. chattering, a nonlinear integral surface is defined.
The designed SMC based ABS and the conventional ABS are then evaluated under dry nominal,
dry concrete and dry slippery road types. And also the performance of the two systems
are evaluated under three different initial vehicle velocities and the system responses are then
compared in terms of wheel speed and stopping distance.
As the numerical simulation shows, on a dry nominal road, for an initial vehicle speed of 40
km/hr, the stopping distance that is obtained from the SMC based ABS and the conventional
ABS are 14.5000mand 15.7080mrespectively. In the same road type, for an initial velocity of 90
km/hr, the stopping distance that is obtained from the SMC based ABS and the conventional
ABS are 73.5122mand 79.6029m respectively. And also for an initial vehicle speeds of 40km/hr
and 90km/hr, the braking time of the SMC based ABS is 0.11 Second and 0.39 Second faster
than the conventional ABS respectively. At last, the proposed SMC based ABS achieves a robust
system, minimum braking time and minimum stopping distance than the conventional
ABS for all road types.
Keywords: SlidingMode Control, Antilock Braking System, Sliding surface, wheel slip
Description
Keywords
SlidingMode Control; Antilock Braking System; Sliding surface; wheel slip v