In this paper we propose a robust control strategy for a gantry crane system with hoisting. The trolley moves horizontally to translate a load mass, hanging at the lower end of a cable, from rest to rest. Due to the flexibility of the cable, load swing easily arises, and should be controlled. To this end, the trolley motion and load hoisting are designed carefully. The desired trolley motion is decided in real time by a wave-based approach, which interprets the cable motion as two superposed traveling waves, to eliminate the load swing at the end of a manoeuvre. The load hoisting is chosen to reduce the load swing during the manoeuvre. A robust algorithm, based on a nonlinear model of the crane system, is proposed for the tracking control, allowing for system parameter variations and uncertainties. This control algorithm works very well and is stable and robust to large load variations. As demonstrated in the numerical simulations, it lands the load rapidly and exactly at target and stops it dead, with zero swing

A macro-micro manipulator system, which is composed of a long flexible-link manipulator as a macro manipulator and a relatively smaller rigid manipulator attached to the tip of the macro one as a micro manipulator, is employed to improve the motion precision of a flexible space manipulator. At the same time the macro-micro manipulator system preserves the capabilities of large work volume, high operation speed and low energy consumption of the flexible space manipulator. In this study, using the forward/inverse kinematics and a perturbation principle, an error compensation approach is proposed to eliminate as far as possible the endpoint errors of a flexible system through the fast and fine adjustment of the motion of the micro manipulator. A feedback model-based control scheme is proposed to realize the endpoint trajectory tracking of the flexible macro-micro manipulator system. Experimental results on a planar flexible 2-DOF macro/2-DOF micro manipulator system are presented herein to show the effectiveness of the proposed methods.