Active Suspensions Classical or Optimal?

SUMMARY The paper describes four control configurations designed for an electromagnetic vertical active suspension fitted to a BR Mk III coach. Two of the control systems were designed using classical frequency response techniques and two using linear optimal control theory. Theoretically the performance of the optimal control systems compared favourably with that of the classical controllers and design of the regulator proved to be both rapid and straightforward. However, physical realisation of the optimal control system required a rationalisation of the vehicle model which drew heavily on experience gained in the design of classical control systems. During track testing, problems of interaction between vehicles were encountered, as a result the biggest improvements in ride were obtained with a simple “skyhook” damper which was less specific to the vehicle than the other configuration. However, with further development one of the optimal controllers will probably turn out to be the most effective as it draws on the attributes of both control system design techniques.