Experimental study on fingertip friction perception characteristics on ridged surfaces

Fingertip friction perception characteristics have not formed a clear and complete theory, owing to the low repeatability and accuracy of related experiments. Given this, a novel experimental method is proposed based on ridged surfaces for investigating the fingertip friction perception characteristics. In this method, based on the Universal Mechanical Tester (UMT) TriboLab, the proposed experiment makes subjects touch ridged surfaces under different ridge sizes and lubrication conditions, aiming to obtain fingertip friction and subject judgment. Subsequently, the average friction force fluctuation degree and the tactile perception accuracy are calculated to analyze the friction characteristics. For this, the relationship between friction and perception characteristics is discussed further. The results show that the adhesive and the deformation friction forces, which mainly consist of the total friction force under incomplete contact conditions, decrease due to the lubricating oil. However, the adhesive friction force increases slightly as the ridge widens. In addition, when the ridge spacing is raised, the deformation friction force increases and becomes the dominant component, while the adhesive friction force is the opposite. While analyzing the friction characteristics, it is found that the tactile perception accuracy is enhanced by raising the average friction force fluctuation. Moreover, the tactile perception accuracy can be improved by changing the surface texture and lubrication conditions, due to the changes in fingertip friction characteristics.