Abstract
Spreaders and lifters of cranes are usually controlled to stop at the same time when their trolleys are stopped. Despite the adequate control, however, the lifters have usually considerably large swings due to the free suspension of the lifters from the ceilings through pullies with two pair of wires. It is therefore important to measure the attitude of the lifters on-line in order to suppress the swings by second controls.
The authors previously proposed a maintenance-free automatic measurement and control system which measured the lifter's attitudes accurately and controlled the lifters to have no swings. But, the control system was available only after the trolleys were stopped, because the control system was constructed on the basis of the double pendulum model of the lifter system under no movement of trolleys.
The paper proposes a new on-line automatic measurement and control system which enables the lifters to stop at the same time when the trolleys are stopped. To realize it, the system uses a rotary-encoder and a tacho-generator on the trolley and a servo-type accelerometer on the lifter to extract a useful information on the trolley-lifter system.
