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Previous work to examine the performance of a variety of control strategies for a switchable damper suspension system is extended to include an adaptive suspension. The aim of this adaptation algorithm is to maintain optimal performance over the wide range of input conditions typically encountered by a vehicle. The adaptive control loop is based on a gain scheduling approach and two strategies are examined both theoretically and experimentally using a quarter vehicle test rig. For the first strategy, the gains are selected on the basis of root mean square (r.m.s.) wheel acceleration measurements whereas in the second approach the r.m.s. value of suspension working space is used. A composite input is used consisting of sections of a road input disturbance of differing levels of magnitude in order to test the control systems' abilities to identify and adapt efficiently as the severity of the road input changes.

One of the various active suspensions, which have been shown to have considerable practical potential, is a switchable damper suspension system. However, previous studies of this system have concentrated on the improvements obtainable for certain fixed road roughness, fixed forward speed and fixed vehicle parameters using a quarter vehicle model. This paper is concerned with an analytical study of a four-degrees of freedom vehicle incorporating a passive and a switchable damper suspension system. A half vehicle model of the switchable damper suspension system with adaptive control strategy is developed. The controller provides a set of gains over different operating conditions. The vibrations of the half vehicle are induced by random road inputs at the front and rear wheels. An investigation of the influence of switchable damper suspension system on vehicle ride quality control is performed on this model and compared with the conventional passive suspension.

There have been numerous studies of various forms of active suspensions over the past three decades. Most of published literature has reported theoretical studies and outlined the potential advantages in both vehicle ride and handling of such systems over their passive equivalents. One of the systems, which have been shown to have considerable practical potential is a limited bandwidth active scheme based on hydro-pneumatic components. However, in order to exploit the full potential of this arrangement, the control law should include two features; (a) the ability to exploit the wheel-base preview effect in which information at the front suspension of the vehicle is used to improve performance at the rear and (b) the ability to adapt on gain scheduling approach to a variety of different operating conditions. Both features are investigated in the paper using a four degree of freedom model and practical performance benefits are quantified.