Discrimination Accuracy of Step Height Based on Reference Height and Comparison Height in Tactile Inspection

Abstract

Tactile inspection, which is part of the appearance inspection, involves touching a target object to detect defects in appearance, such as unevenness of the product surface, irregular steps between parts, and distortion of the product shape. Herein, this inspection is assumed to discriminate the step height. This study clarifies how inspectors' discrimination accuracy for step heights is affected by the step height set in quality standards and the step height generated on the product. The subjects were 10 healthy males, and they discriminated whether the step height of a sample is “higher than,” “lower than,” or “the same as” a reference step height. Discrimination ability was evaluated using the indices of the correct-answer rate and the vertical control force that the subjects applied to the step. The results clarified that misjudgment occurred by recalling the memorized reference height as being higher than the actual height. Additionally, control force had almost no effect. From these results, it is suggested that the risk of outflow of defective products due to the type-II error may differ depending on whether or not the criteria for defective products includes the standard value of the step height.