OPTIMAL PATH PLANNING FOR A TROLLEY CRANE - FAST AND SMOOTH TRANSFER OF LOAD

Optimal speed references were designed for a trolley crane. The path p lanning problem was split into five phases: vertical upward movement o f the load; acceleration of the trolley while still hoisting the load; horizontal movement of the trolley with maximum velocity without hois ting; deceleration of the trolley while setting down the load; and ver tical downward movement of the load. Energy optimal speed references f or a given transfer time were computed for the so-called diagonal move ments in which the load and trolley moved simultaneously. A dynamical model of the crane mechanics and actuators was used in the formulated optimal control problem. The transfer times for the diagonal movements were made as small as possible so that the given maximal angular velo cities of the actuators were not exceeded. Speed references for the th ree other phases were easily obtained since they involved either hoist ing only, or transfer of the trolley with constant velocity without ho isting. A pilot crane experiment with a scaled-down model of an existi ng crane showed that for a typical load transfer task, the duration of the optimal movement was less than 50 per cent of the duration of man ual transfer. Moreover, the transfer of the load was smoother than in the manual operation and without any significant back and forth swingi ng of the load.