Detection Threshold and Mechanical Impedance of the Hand in a Pen-Hold Posture

Abstract

-We report position and force detection thresholds for sinusoidal waveforms in the frequency range 10-500 Hz delivered through a stylus. The participants were required to hold the stylus in a way similar to that of holding the stylus of a force-feedback device. A minishaker moved the stylus along its length so that the majority of vibrations were presented tangentially to the skin of the hand. The measured position thresholds decreased initially with an increasing stimulus frequency and formed a U-shaped curve in the high frequency region. The thresholds of high frequency vibrations were lower than those reported previously for vibrations that were perpendicular to the skin, but were similar to the thresholds reported earlier using vibrations that were tangential to the skin. A similar force threshold curve was obtained using a force sensor attached to one end of the stylus. Mechanical impedance of the skin derived from velocity estimates and force measurements indicated that the skin and tissues in the hand holding the stylus can be modeled with mass-, damper-and spring-like elements. A comparison of the mechanical impedance from the present study with those reported previously showed similar results for vibrations delivered in the tangential and normal directions to the skin.

Mechanical Impedance of the Hand Holding a Spherical Tool at Threshold and Suprathreshold Stimulation Levels

“…Brisben et al reported the displacement detection thresholds for a cylindrical tool that was held in the palm of the hand in a power grip and vibrated in a direction tangential to the skin of the palm [9]. One of our previous studies published the displacement and force detection thresholds measured with a stylus held in a pen-holding posture [1]. In the present study, we investigated the detection thresholds for a spherical tool held with multiple fingers.…”

“…Common tool shapes include stylus, thimble, puck and ball, resulting in varying hand-holding postures and contact areas with the tool. We have been interested in examining the effect of tool shapes on the proximal stimuli received by the fingers of the hand (e.g., [1]). The present study considers the spherical tool (e.g., a ball or a puck), found in the Delta or Omega devices (ForceDimension, Switzerland) and magnetic levitation devices [2], that is typically held in the hand with multiple fingertips.…”

Human-Arm-and-Hand-Dynamic Model With Variability Analyses for a Stylus-Based Haptic Interface

“…McMahan and Kuchenbecker identified a five-parameter MSD model of the hand interfaced with a stylus grip haptic device using a 1-DOF linear actuator custom mounted onto the Phantom's stylus itself (for high-frequency, i.e., 10-200 Hz, vibrotactile feedback applications) [22]. Israr et al have used both stylus-based devices and spherical actuators to shake the hand at 10-500 Hz [23], [24]. Also, Díaz and Gil have investigated the vibration modes from 0.7 to 200 Hz in 1 DOF of the human operator using a racquet grip on the Phantom Premium 1.0 and a custom haptic interface [25].…”

Development and assessment of a hand assist device: GRIPIT

“…12) and the rotated angle of the pen (φ in Fig. 12) was used as an indicator of solidity [29,30]. The system for simultaneously measuring force and position data is shown in Fig.…”