Haptic interaction with virtual objects

Abstract

This paper considers interaction of the human arm with "virtual" objects simulated mechanically by a planar robot. Haptic perception of spatial properties of objects is distorted. It is reasonable to expect that it may be distorted in a geometrically consistent way. Three experiments were performed to quantify perceptual distortion of length, angle and orientation. We found that spatial perception is geometrically inconsistent across these perceptual tasks. Given that spatial perception is distorted, it is plausible that motor behavior may be distorted in a way consistent with perceptual distortion. In a fourth experiment, subjects were asked to draw circles. The results were geometrically inconsistent with those of the length perception experiment. Interestingly, although the results were inconsistent (statistically different), this difference was not strong (the relative distortion between the observed distributions was small). Some computational implications of this research for haptic perception and motor planning are discussed.

Coordinate Dependence of Variability Analysis

“…For example, Todd and colleagues present convincing evidence that visual space does not have a metric structure [18], [19]. Behavioral evidence of an equivalent finding for the motor system was provided by Fasse and colleagues who showed that at least some aspects of human perceptual-motor behavior do not admit a metric structure [20]. To underscore the behavioral evidence, if joint angles are perceived with respect to an external spatial reference, as reported by Soechting and Ross [21] then they cannot admit a metric because finite rotations with respect to an extrinsic spatial reference do not commute and hence violate one of the fundamental requirements to define a space with a metric.…”

Haptic Discrimination of Distance

“…Recently, however, McFarland and Soechting [31] systematically manipulated arm speed and effort of participants judging radial and tangential distances and found no effect of either manipulation on the size of the illusion. Other authors have shown that the illusion is still present when the L-shape is presented at an angle with the radial and tangential axes [32], [33], [34], but it disappears when the stimulus is presented in the vertical (fronto-parallel) plane [34], [35].…”

Two hands, one perception: how bimanual haptic information is combined by the brain

“…We know that haptic sensing requires the integration of spatially disparate sensory signals from cutaneous afferents in the digits with proprioceptive signals of the arm (a process of intersensory integration). However, we know very little about how the brain combines the haptic information of our two hands to achieve a single percept of an object and about the underlying mechanism of how the nervous system integrates or fuses information from two haptic systems.To investigate issues of haptic sensing in a controlled experimental setting, virtual force environments have been used to present haptic stimuli (Chib et al 2006;Fasse et al 2000;Henriques and Soechting 2005;Hogan et al 1990). In these studies, subjects usually grasped the handle or stylus of a robotically controlled manipulandum, which generated appropriate boundary forces resembling the surfaces of virtual objects.…”

“…In these studies, subjects usually grasped the handle or stylus of a robotically controlled manipulandum, which generated appropriate boundary forces resembling the surfaces of virtual objects. The advantage of this technique is that object shape and boundary stiffness can be modified from trial to trial (Chib et al 2006;Henriques and Soechting 2003), shapes that are not realizable physically can be simulated (Fasse et al 2000), and subjects' sensitivities can be computed with great precision (Henriques and Soechting 2005). Whereas a number of these psychophysical studies have investigated unimanual curvature discrimination (Louw et al 2000;Pont et al 1997Pont et al , 1998Pont et al , 1999van der Horst and Kappers 2008;Wheat and Goodwin 2001), scant attention has been paid to bimanual curvature discrimination, because the technology for bimanual haptic environments has just recently become available.…”

“…To investigate issues of haptic sensing in a controlled experimental setting, virtual force environments have been used to present haptic stimuli (Chib et al 2006;Fasse et al 2000;Henriques and Soechting 2005;Hogan et al 1990). In these studies, subjects usually grasped the handle or stylus of a robotically controlled manipulandum, which generated appropriate boundary forces resembling the surfaces of virtual objects.…”