Visual feedback control of an overhead crane and its combination with time-optimal control

Abstract

For operation of overhead crane, positioning and swing controls of a load are necessary. There is time-optimal control as feedforward control of crane. This method does not use sensors, but the trolley controlling velocity must be set using exact natural period of load swing that is beforehand estimated and the time to control swing suppression is necessary as same order of natural period. Therefore, if the rope length changes in use, the load may swing that is caused by the feedforward control based on false natural period different from real. In addition, the time to control swing suppression gets longer when rope length is long. On the other hand, concerning the feedback control of crane, there is visual feedback control using a camera as non-contact sensor. In this paper, we used a three dimensional camera installed on the trolley and measured the three dimensional position of the marker of the load. Experiments of visual feedback control using 3D-camera and time-optimal feedforward control were performed to control the overhead crane with traveling, traversing and hoisting motions. Furthermore, we tried the combination control that is the timeoptimal feedforward control of transportation and the visual feedback control of swing suppression. We examined influences of estimated error of natural period and installed position of load marker. The experimental results of overhead crane by both visual feedback control and its combination with time-optimal control show that these control systems are effective. © 2008 IEEE.