Sway Angle Sensor System for Full-Scale Tower Cranes Based on the Phase Difference of Sound Waves

Antisway control requires accurate and rapid sensing of the payload sway angle (SA). Therefore, in this study, we propose a novel approach for developing SA sensor systems for full-scale tower cranes. The proposed method focuses on applying physical laws of sound to achieve accurate SA sensing. First, sound waves were generated from a sound source installed on a hook and were monitored using microphones set up on the crane jib. Next, we introduced a signal processing method for computing the phase difference of sound waves (PDSWs) and an algorithm for estimating the SA from the PDSW. Furthermore, we developed an algorithm to remove aliasing from the PDSW and conducted experiments to demonstrate the effectiveness of the proposed SA sensor system. The proposed method accurately approximated the amplitude and frequency of the pendulum motion of a payload attached to a full-scale tower crane using more than 40 m of wire. Thus, the proposed sensor system can be used for antisway control in various types of full-scale cranes.