Use of fuzzy logic in active suspension

1. A
REPORT
ON
FUZZY LOGIC
BASED
ACTIVE SUSPENSION
PRESENTED BY
AKSHAY GOPAL SARODE
1605013
MTECH CCR

2. ABSTRACT
The suspension system is mainly designed with an view of improving passenger
ride comport.Usually automobile suspension systems are compromise between two
important parameters namely travel of suspension and road handling abilty.The
demand for development of new suspension systems have arisen due to problems
in ride comfort and car handling.The contact forces between tires and road surface
is termed as raod holding ability.There is the linear dependence of contact forces
on the deflection of tires.The relative displacement between unsprung and sprung
mass is refered as suspension travel.The present work aims at developing fuzzy
logic based active suspension for performance improvement of passenger car.To
verify the performance of active suspension it is simulated using matlab and
comparing performance of both systems.

3. INTRODUCTION
The most important part of any vehicle is its suspensionsystem.Suspension is the
combination of the shockabsorbers,linkages and springs that separates sprung
mass from the unsprung mass of vehicle.The aim of suspension system is to
provide high ride quality comfort by eliminating the shocks from vehicle due to
bad road conditions;the holding ability of road ; to provide vehicle handling which
is best and to supportthe weight of vehicle.Also suspension system has to
minimize road noise,vibrations and bumps.Thetypes of automobile suspension are
1. Dependent
2. Semi Independent and
3. Independent suspension system.
The independent suspensionsystem is active suspension system.
The limitation of the passive suspension system is that it cannot control the
road holding capability and handling of the vehicle effectively.On the other
hand,the active suspension system consists of actuator in parallel connection
with damper and spring to inject energy into the system. The advantage of
active suspension system over passive suspension is that active suspension has
large adaptability potential where the characteristics of the suspension can be
varied according to the driving condition.The very big challenge in todays
world regarding suspension is producing cutting edge models for systems.thus
to avoid the suspension problems the various possible measures have been
proposed such as fuzzy logic control,adaptive control,non linear control and
linear quadratic regulator control.The above controllers can easily solve the
evolving problems in shortest possible time.The technology of vibration
control is nowadays perfect due to theory of modern theory of control

4. engineering. The Suspension system is one of the essential parts of vehicles,
and its main objectives are to ensure high-quality ride comfort by isolating the
vehicle body from road disturbances; to maintain good road holding ability; to
provide finest vehicle handling capability and to support the mass of vehicle
[1]. The automotive suspension system is classified into three types: passive
suspension, semi-active suspension and active suspension system [2].
However, due to the fixed characteristics such as damper coefficient and spring
stiffness in passive suspensions, it cannot control the road holding capability
and handling of the vehicle effectively [3] [4]. To the contrary, an active
suspension system has an actuator connected in parallel to both the spring and
damper to inject energy into the system. The adaptation potential of an active
suspension is one of the key advantages over passive
suspension where the suspension characteristics can be attuned while driving to
accommodate the diverse terrain conditions of the road being traversed [5]. Fierce
competition is driving today's automotive industry so as to produce cutting edge
suspension system models. Therefore, to overcome the complex suspension system
problems, several control methods have been proposed. For instance, control
approaches such as adaptive control, Fuzzy Logic Controller (FLC) and non-linear
control are proposed to resolve the arising problems [6].

5. LITERATURE REVIEW
Ayman aly,Al marakeby,Kamel A.Shoush
This paper represent the 4 dofhalf bodyvehicle suspension system with modeling
of roughness intensity of road.This technique used for controlling the suspension
system are fuzzy logic and pid techniques.The main aim of the paper is to reduce
the acceleration of the sprung mass.also there should be reduction in the
acceleration of pitching.the travel of the suspension is minimized.the comfort of
riding with stability can be achieved by comparing pid control suspension and
fuzzy logic.The active suspension is modeled using pids and flc which are self
adaptable.Here the model of closed loop flc is used,based onmamdani method.The
flc has three inputs namely deflection,velocity and acceleration.The output is
desired force of the actuation.The result of flc have been used for for designing
purpose,and being presented effective.The evaluation of result is that the
experimented active suspensionis very effective in isolation of the vibration from
vehicle body.Thus improvement of stability of active suspension is finally
achieved.

6. Narinder Singh Bhangal,kumar Amit Raj
This paper describes the dynamics of the the suspension system which is modeled
using quarter car having two dof which is the fuction of time which is linearly
invariable.This paper is aimed at improving performance of the active suspension
system with the help of flc and linear quadratic regulator.Also the result is
compared witrh Passive system of the suspension.The vehicle performance on the
road is simulated using Simulink.The results states that flc and lqr can be
efficiently used to controlthe vehicles vibration.Among the flc and lqr,the flc is
best in reducing the sprung mass acceleration.The objective is to represent
algorithm of fuzzy logic for making passenger comfortable with road handlin of
the quarter car model effective.FLC used consists of bodyvelocity and
acceleration as input with force of actuation as the output.Here the sine function is
used for simulation of the disturbance of the road.The designing of flc and lqr is
done on matlab.The active suspensioncan be very effective is maintaining the
suspension stability as compared to the passive suspension.The vibrations are
prevented effectively by flc with respect to all other suspensionsystems available.

7. M.V.C Rao and V.Prahalad
In this paper, the active suspension based on fuzzy logic controller is used for
increasing ride comfort. The vehicles vibration and road disturbances occuring due
to road conditions; are decreased significantly. This in turn leads to increase in
comfort during ride. The experiment of vehicle is done on road terrains which are
uncertain in nature. An quarter car suspension system is bought under required
control to decrease vertical acceleration. The suspension's deflection and
acceleration are adjusted by carrying trial and error method on parameters of
spread, bell-shaped centre and flex membership functions in relation to different
variables considered. Simulation is carried out to check the effectiveness of FLC
for active suspension system. The inputs to the FLC are deflection and velocity of
active suspension system. The output is the comfort of ride; by providing the
actuator force. The FLc which is tuned effectively results in lowering deflection
and accelerationto the level of arbitary considered reference model. The better
comfort of riding is achieved. Thus the active suspension system is successfully
experimented for increasing the passsenger's comfort.

8. Alireza Rezaee, Mazyar Pajobesh
This paper conveys controlling of active suspension system of quarter car model
using fuzzy logic technique. The purpose of the suspension system is to increase
and support body of vehicle. The results explains that active suspension system
improvement is achieved for ride comfort by decreasing acceleration ; compared
with other suspension system . The considered quarter car model has single damper
with body and tire mass, 2 springs and 1 actuator force. The model is used in
creation of control force for wheel and body. The model has 2 DOFs. The paper
describes the vehicle response results acquired through number of road simulations
input. Thus, active suspension is helpful and effective in improving the comfort of
riding, as related with the passive suspension system.

9. CASE STUDY
PROBLEM STATEMENT:
Many researchers have come up with a variety of vehicle suspension strategies
through simulation and experimental work with the aim to improve the ride quality
and vehicle stability in [8] [9]. Almost all of the implemented and proposed works
for complicated suspension models are considering uncertainty and nonlinearity in
the dynamics. Indeed, most of them show a margin of improvement that the
proposed active suspension model could deliver, primarily to the ride quality and
handling aspects, at the expense of creating additional loads to the system when
compared with the linear active suspension [10]. The use of several intelligent
control approaches such as using a neural network and fuzzy logic further
enhances the research. Nevertheless, both approaches are often limited to
simulation works in laboratories owing to inherent computation burden.
Furthermore, both
methods are mathematically intensive and not feasible in real time implementation
[11] [12]. Thus, the aim of this paper is to demonstrate a unique method to control
a real-time active suspension system, based on the Active Force Control (AFC)
strategy to an active suspensionsystem. The proposed controlmethod is capable of
improving ride comfort and vehicle road holding capability through reducing the
sprung mass (car body) motion of a quarter car suspension system model [12].
Quarter car model:
In this study, the vehicle model considered is a quarter car model. Typically, a
suspension system consists of sprung mass (car body), unsprung mass (wheel,
brake, steering hub), spring and dampers. The passive suspension system for
quarter car model consists of one wheel, one-fourth of the bodymass and
components of suspension as shown in Figure 1(a). The active suspension system
for quarter car model has a hydraulic actuator in parallel with the spring as shown
in Figure 1(b).

10. FIGURE 1: Passive (a) and Active (b) quarter car models [13]
The quarter car system modelling assumptions are as follows: The tire is
constantly in contact with the surface of the road and the friction effect is
ignored so that the residual damping is not considered into vehicle modelling;
the tire is modelled as a linear spring without damping; the wheel and body
have no rotational motion; the spring and damper are linear in behaviour [13].
Thus, the quarter car model with two degrees of freedom model uses a unit to
create the control force between wheel mass and body mass.
The motion equations of the wheel and car bodyare as follows:
mbz’’b = fa − k1 (zb − zw ) − c (z’b – z’w )
mwz’’w = −fa + k1 (zb − zw ) − k2 (zw – zr)
EQUATION 1, 2: Motion equationsof the wheel and car body [14]

11. TABLE 1: Rule Base [14]
DISCUSSION
Thus, we have discussed the designing of active force control loop for pneumatic
air spring actuator in this paper. In order to improve and control the ride comfort
and road handling in a quarter car model, Mamdani and Sugeno fuzzy control
techniques are used. MatLab/Simulink is used to obtain the simulation results.
Evaluation among the fuzzy, passive and active force control systems shows that
the performance of air spring suspension with AFC system can improve the road
handling and the ride comfort.