Analysis of Skilled Force Control in Glass Grinding Work

Abstract

Due to the importance of understanding the scientific basis in the succession of handwork skills, this study aims to clarify human factors contributing to the basis of handwork skills by examining glass grinding work. The glass grinding load manually added by workers was measured with a handmade force sensor. Four workers participated in this experiment : one novice, one intermediate, and two skilled workers. Two important force parameters, the intensity of load (IL) and the center of load (CL), were analyzed. With respect to IL, the novice worker maintained a high load level with weak intensity changes, whereas the skilled workers used a clear force rhythm with large intensity changes. Because the novice maintained a high load (vertical pushing force), he had to apply a strong muscle force against the grinding force (horizontal resistance force). Therefore, the novice’s method was tiresome. In addition, the results indicate that the CL patterns did not converge into a single mode among workers. However, based on a simulation, the CL patterns for intermediate and skilled workers were less influenced by force fluctuations compared to that of the novice. The results demonstrate that handwork skill compensates for human weakness; that is, handwork skill reduces fatigue and compensates for force instability.