Design of an active suspension to suppress the horizontal vibrations of a spray boom

Spray-boom vibrations are one of the main causes of a non-homogeneous distribution of agro-chemicals. Yawing and jolting motions of the boom are most critical. A horizontal active suspension, reducing yawing and jolting is designed. The use of special and consequently expensive equipment hampers the breakthrough of active suspensions. Therefore the proposed active suspension is built from standard hydraulic equipment, suited for mobile applications. Coulomb friction and asymmetric behaviour introduces considerable non-linearities, complicating the derivation of a linear model and controller design. It is explained how to identify a model, approximating in the best-possible way the general linear behaviour of the system. By the H∞ methodology and an iterative procedure, introduced in this paper, non-linearities are taken into account in the controller design without increasing the controller dimensions. The resulting controller is stable and shows good performance.