Controlling the slewing motion of hydraulically actuated cranes using sequential activation of counterbalance Valves

This paper is concerned with the controlled motion of hydraulically actuated transmissions characterized by large inertias, backlash and several parallel coupled gearmotors. A method for controlled start and braking of such a transmission is put forward that utilizes sequential activation of the counterbalance valves of the hydraulic circuit. The method, which has been implemented into numerous high end offshore applications, is demonstrated by means of time domain simulations of a knuckle boom crane used for pipe handling in offshore drilling. The suggested activation method may yield higher load levels in the transmission but has the ability to reduce or eliminate the occurrence of impact and loss of contact in the transmission.