Engineering, 2009, 1, 1-54
Published Online June 2009 in SciRes (http://www.SciRP.org/journal/eng/).
Copyright © 2009 SciRes. Engineering, 2009, 1, 1-54
Skyhook Surface Sliding Mode Control on Semi-Active Vehicle
Suspension System for Ride Comfort Enhancement
Yi Chen*
Department of Mechanical Engineering, University of Glasgow, Glasgow, United Kingdom
Email: yichen@mech.gla.ac.uk
Received March 25, 2009; revised April 11, 2009; accepted April 18, 2009
Abstract
A skyhook surface sliding mode control method was proposed and applied to the control on the semi-active
vehicle suspension system for its ride comfort enhancement. A two degree of freedom dynamic model of a
vehicle semi-active suspension system was given, which focused on the passenger’s ride comfort perform-
ance. A simulation with the given initial conditions has been devised in MATLAB/SIMULINK. The simula-
tion results were showing that there was an enhanced level of ride comfort for the vehicle semi-active sus-
pension system with the skyhook surface sliding mode controller.
Keywords: Sliding Mode Control, Skyhook Damper, Fuzzy Logic Control, Semi-Active Suspension System
1. Introduction
The ride comfort is one of the most important character-
istics for a vehicle suspension system. By reducing the
vibration transmission and keeping proper tire contacts,
the active and semi-active suspension system are de-
signed and developed to achieve better ride comfort per-
formance than the passive suspension system. The active
suspension is designed to use separate actuators which
can exert an independent force on the suspension, this
action is to improve the suspension ride comfort per-
formance. The active suspension system has been inves-
tigated since 1930s, but for the bottle neck of complex
and high cost for its hardware, it has been hard for a
wide practical usage and it is only available on premium
luxury vehicle [1]. Semi-active (SA) suspension system
was introduced in the early 1970s, it has been considered
as good alternative between active and passive suspen-
sion system. The conceptual idea of SA suspension is to
replace active force actuators with continually adjustable
elements, which can vary or shift the rate of the energy
dissipation in response to instantaneous condition of mo-
tion. SA suspension system can only change the viscous
damping coefficient of the shock absorber, it will not add
additional energy to the suspension system. The SA sus-
pension system is also less expensive and energy cost
than active suspension system in operation [2]. In recent
years, research on SA suspension system has been con-
tinuing to advance with respect to their capabilities, nar-
rowing the gap between SA and active suspension sys-
tem. SA suspension system can achieve the majority of
the performance characteristics of active suspension sys-
tem, which cause a wide class of practical applications.
Magnetorheological / Electrorheological (MR/ER) [3
-5] dampers are both of the most widely studied and
tested components of the SA suspension system. MR/ER
fluids are materials that respond to an applied mag-
netic/electrical field with a change in rheological behav-
iour.
Variable structure control (VSC) with sliding mode
control was introduced in the early 1950s by Emelyanov
and was published in 1960s [6], further work was devel-
oped by several researchers [7-9]. Sliding mode control
(SMC) has been recognized as a robust and efficient
control method for complex high order nonlinear dy-
namical system. The major advantage of sliding mode
control is the low sensitivity to a system's parameter
changing under various uncertainty conditions, and it can
decouple system motion into independent partial com-
*
Yi Chen is with the Department of Mechanical Engineering, Univer-
sity of Glasgow, Glasgow, United Kingdom, G12 8QQ. Tel:
44(0)-141-330-2477, Fax: 44(0)-141-330-4343.