The effect of indentation force and displacement on visual perception of compliance

Abstract

Abstract-This paper investigates the effect of maximum indentation force and depth on people's ability to accurately discriminate compliance using indirect visual information only. Participants took part in two psychophysical experiments in which they were asked to choose the 'softest' sample out of a series of presented sample pairs. In the experiments, participants observed a computer-actuated tip indent the sample pairs to one of two conditions; maximum depth (10mm) or maximum force (4N). This indentation process simulates tool operated palpation in laparoscopic surgery. Results were used to plot psychometric functions as a measure of accuracy of compliance discriminability. A comparison indicated that participants performed best in the task where they judged samples being indented to a pre-set maximum force relying solely on visual cues, which demonstrates the effect of visual information on compliance discrimination. Results also show that indentation cues such as force and deformation depth have different effects on our ability to visually discriminate compliance. These findings will inform future work on designing a haptic feedback system capable of augmenting visual and haptic information independently for optimal compliance discrimination performance.

Inferring the stiffness of unfamiliar objects from optical, shape, and motion cues

“…They showed observers animated scenes in which a rigid cylinder interacted with cubes of varying stiffness and optical appearance, either (a) by pushing into the cubes from above (i.e., indenting the cubes) or (b) by retracting from the rear edge of the cubes (i.e., setting the cubes into reverberating motion). In line with the findings by Kawabe and Nishida (2016), perceived stiffness varied along with the deformation of the cubes' shape in both scenarios (i.e., either with the magnitude of the penetration of the cylinder into the cube or with the amount of shape change across the cube's motion; also see Fakhourny, Culmer, & Henson, 2015). Then, Paulun et al (2017) obtained stiffness ratings for the cubes in the first scenario (cylinder pushing into cube) and in the second scenario (cube set into motion) when rendered with different optical materials, ranging from hard (e.g., steel, copper) to soft (e.g., latex, velvet).…”

The impact of visual cues on haptic compliance discrimination using a pseudo-haptic robotic system

“…Force and position data for all 11 samples obtained during the indentation tests were fitted to the Voigt model. The stiffness and damping coefficients are identical to those obtained in previous experiments [4].…”

“…The data was fitted to a Voigt viscoelastic model to obtain stiffness constants and damping coefficients for the samples. Stimuli fabrication, compliance testing and model fitting methods are extracted from [4], [5].…”

“…The average force and displacement values across the five repeats were calculated and used for model fitting. 1] was used in this experiment as it has been used in the literature to model the behaviour of soft tissue during loading [4], [21].…”

“…These ratings reflect the compliance levels of the physical stimuli, not the participant responses. The ratings were obtained using Equation [4].…”