Performance of Active Suspension with Fuzzy Control

Vehicle suspension along with tires and steering linkages is designed for safe vehicle control and to be free of irritating vibrations. Therefore the suspension system designs are a compromise between ride softness and handing ability. However, this work is concerned with a theoretical investigation into the ride behavior of actively suspended vehicles. It is based on using fuzzy logic control (FLC) to implement a new sort of active suspension system. Comparisons between the behavior of active suspension system with FLC with those obtained from active systems with linear control theory (LQR), ideal skyhook system and the conventional passive suspension systems. Results are introduced in such a way to predict the benefits that could be achieved from fuzzy logic system over other competing systems. Furthermore, a controller is designed and made by using results of FLC system, theoretical inputs are used to examine the validity of this controller. Moreover, comparison between actual outputs from this controller with those obtained theoretical is made to judge the validity of the controller. The results indicate that the controller has a good capability in simulation of the theoretical model.

NOMENCLATURE

A

Road input amplitude, m 0.05

BA

Body acceleration, m/s2 -

C

Coefficient of power spectral density 5

C₂

Suspension damping coefficient, Ns/m 1300

C₃

Skyhook damping coefficient, Ns/m 20000

DTD

Dynamic tire deflection, m -

K₁

Tire stiffness, N/m 192000

K₂

Suspension stiffness, N/m 20000

M₁

Unsprung mass, kg 45

M₂

Sprung mass, kg 310

R_c

Road roughness coefficient 4 × 10⁻⁴

SWS

Suspension work space, m -

t_s

Sampling time, s 0.01

V

Vehicle velocity, m/s -

y₁

Body acceleration as an output, m/s₂ -

y₂

Suspension working space as an output, m -

y₃

Dynamic tire loading as an output, m -

λ

Road wave length, m 10.46

ω_c

Sprung mass natural frequency, rad/s 7