Application of laser slot sensors for the state estimation of overhead cranes

The load of overhead cranes are attached to the mechanical structure with a rope, consequently the trajectory of the load cannot be actuated directly. This results in an unwanted oscillatory behaviour, which needs to be damped for the effective and safe transportation. In existing automated cranes, control solutions suggest state-feedback law. In previous work we proposed an estimation algorithm employing the unscented Kalman filter for the calculation of the unmeasured states. Because of the stiction, this method becomes inaccurate when the trolley does not move. In this paper we suggest the application of a pair of laser slot sensors for detecting when the rope is close to the vertical. Incremental encoders are used to measure the displacement of the trolley and the length of the rope. Since the detection of the vertical rope angle is asynchronous w.r.t. the sampling instant, an appropriate sensor fusion technique is provided. The effectiveness of the estimation method is verified on a real laboratory crane setup.