EVALUATION OF A CASCADE COMPENSATOR FOR HORIZONTAL VIBRATIONS OF A FLEXIBLE SPRAY BOOM

Spray booms are weakly damped flexible structures. Tractor vibrations induce horizontal boom deformations which are one of the main causes o f an uneven spray deposition. Since structural adaptations to suppress boom vibration present problems, the feasibility of an active vibrati on compensator was investigated in laboratory tests. The experimental structure consisted of a flexible hollow beam with properties represen tative of common small spray booms, and a cradle on which the beam was clamped. In the experiments, longitudinal tractor vibrations were imp osed upon the cradle and flexible deformations of the beam, induced by cradle accelerations, were compensated by an electro-hydraulic contro l system. The linear quadratic Gaussian method with loop transfer reco very, a robust control theory, was used to design the compensator. Mea sured amplitudes of the beam vibrations were reduced by a factor of mo re than thirty by the electro-hydraulic compensator. (C) 1998 Silsoe R esearch Institute.