Study of the Grasp Conditions Effects on Pinch-Insertion Force Using Wavelet Transform

In this paper, the effects of different grasp types, grasp widths, coupling types, and wearing gloves on pinch-insertion force have been studied using the discrete wavelet transform method, which was proposed for extracting features from the force-time curves during the experiment that simulates the snap-fit assembly procedure. This paper uses collected Salmanzadeh and Landau [4] experiments data as an application for proposed methodology. This method allows to use of all information obtained from the experiment and considers the whole force exertion process instead of one point of curves and at the same time reduce the number of variables without losing information. The results obtained by applying multivariate analysis of variance (MANOVA) on the wavelet coefficients are more sensible and more precise than the results of the conventional method based on only one point of the curve. The results show that both wearing glove and grasp type significantly affect the pinch-insertion forces. The second series of results show that the effects of both grasp width and grasp type on pinch force are significant. The third result series show that both pinch-insertion forces are significantly affected by coupling type with/without wearing gloves. Further analysis was performed on the average wavelet coefficients curves that can explain the cause of MANOVA test results. The results of this paper can be used for ergonomic designing of snap-fits to reduce the potential damage of the assembly process.