Studies of the Mechanical Impedance of the Index Finger in Multiple Dimensions

Measuring dynamic stiffnesses of preloaded distal phalanges in vibration - Test bench validation and parameter study

“…In the study of Moore and Mundie (Moore and Mundie, 1972), the preloading was only significant for frequencies less than 130 Hz, whereas in the highfrequency region, the effect of static loads was measured. However, Dong and co-workers (Dong et al, 2004c) and Kern and Werthschützky (Kern and Werthschützky, 2008) found that the gripping forces or static loads have considerable effects, but they do not cause dissimilar behaviour between the rubbery plateau and the leathery or glassy state, as we found in the present work. However, the boundary conditions of the fingers in their works were different from those in our study.…”

“…Hz. In Lundström's study (Lundström, 1984), this frequency is approximately 200 Hz, while it is approximately 100 Hz for Kern and Werthschützky (Kern and Werthschützky, 2008), Mann and Griffin (Mann and Griffin, 1996), and Wiertlewski and Hayward (Wiertlewski and Hayward, 2012) and 130 Hz for Moore and Mundie (Moore and Mundie, 1972;Moore, 1970). The latter two studies highlighted that the failure frequency at Hz occurs not only at the fingertip, but also in the thenar eminence, the volar forearm, and the thigh.…”

“…To potentially overcome the previous drawbacks, an alternative might consist of directly measuring the local biodynamic responses at the fingertips by using specific devices. For a number of years, the assessment of the local mechanical impedance of the fingers has been the objective of a number of different research fields, such as of course the pathological effects of finger-transmitted vibration (Lundström, 1984;Mann and Griffin, 1996), but also the field of human tactile sensitivity (Moore and Mundie, 1972;Moore, 1970;Wiertlewski and Hayward, 2012), the design of haptic systems (Chai-Yu and Oliver, 2005;Kern and Werthschützky, 2008), and determining mathematical models of the skin dynamic response (Gulati and Srinivasan, 1997;Hajian and Howe, 1997). The common procedure was to locally vibrate the fingertip with a small-sized probe in contact with the skin for two main phalanx boundary conditions: i) clamped fingernail (Gulati and Srinivasan, 1997;Lundström, 1984;Moore and Mundie, 1972), and ii) free fingernail (Hajian and Howe, 1997;Mann and Griffin, 1996;Wiertlewski and Hayward, 2012).…”

Mechanical behavior of the fingertip in the range of frequencies and displacements relevant to touch

“…Since the excitation had little high-frequency energy, the identification was reliable only in the low frequencies. Kern and Werthschützky (2008) used the 'impedance head' approach where force and acceleration are simultaneously measured in the proximity of the interface between the probe and the finger. This approach, however, is known to provide unreliable results in the high frequencies, owing to a possible lack of truly co-located measurements (Brownjohn et al, 1980).…”

An Open-Source Robotic Tool for the Simulation of Quasi-Static Finger Pressing on Stationary and Vibrating Surfaces

“…The fingertip pulp is usually modeled as a viscoelastic nonlinear spring-mass-damper mechanical system [6], whose impedance changes with the frequency and motion direction of external stimuli [11]. As motion direction is concerned, fingertips are anisotropic, exposing a different mechanical impedance in tangential and normal directions [12].…”