Robust Design of a Rope Ascender Based on Geometric Parameters of Traction Sheave

In this study, an optimal-traction sheave is designed to prevent slip for a two-degrees-of-freedom facade-cleaning robot called Dual Ascender Robot (DAR). The DAR uses the length of the rope to estimate its position. Therefore, if a slip occurs, it becomes difficult to measure the length of the rope, thereby making it difficult to estimate position. Problems with position estimation may also cause difficulties in achieving control. The redesigned traction sheave was thoroughly evaluated by experiments. A well-known Taguchi method was used as the experimental procedure, and the optimal design parameters of the sheave were determined as hoop direction groove shape of 0.8, axial direction groove pitch of 6°, and axial direction groove depth of 2 mm. Verification experiments comparing the traction sheave with the optimal condition to that used in DAR showed improved performance. Therefore, it is expected that applying the optimal traction sheave to a DAR in further studies would help achieve better position estimation by preventing slips.