Evaluation of a Cascade Compensator for Horizontal Vibrations of a Flexible Spray Boom

Abstract

Spray booms are weakly damped flexible structures. Tractor vibrations induce horizontal boom deformations which are one of the main causes of an uneven spray deposition. Since structural adaptations to suppress boom vibration present problems, the feasibility of an active vibration compensator was investigated in laboratory tests. The experimental structure consisted of a flexible hollow beam with properties representative of common small spray booms, and a cradle on which the beam was clamped. In the experiments, longitudinal tractor vibrations were imposed upon the cradle and flexible deformations of the beam, induced by cradle accelerations, were compensated by an electro-hydraulic control system. The linear quadratic Gaussian method with loop transfer recovery, a robust control theory, was used to design the compensator. Measured amplitudes of the beam vibrations were reduced by a factor of more than thirty by the electro-hydraulic compensator.