Effect of a pneumatically driven haptic interface on the perceptional capabilities of human operators

This paper describes experimental studies conducted using a pneumatically driven haptic interface (PHI) system. The PHI is a unilateral exoskeletal device that tracks the motion of the shoulder and elbow. The study was carried out to evaluate the impact of an exoskeletal haptic interface on human perceptional capabilities. A population of twenty subjects participated in a set of experiments that were tailored to assess force sensation, shape perception, and effect of force feedback in task performance. Using Weber fractions, we contrasted the outcome of our force sensation experiments against results reported by psychophysical researchers. The results indicated that the perception of weight (or force magnitude) through the haptic interface was significantly affected for relatively low reference force levels (4.44 N, Weber fraction = 0.5). The effect progressively diminished as the force level was increased, and almost matched the natural human capabilities for a reference force level of 18 N (Weber fraction = 0.06). The haptic shape identification experiments showed that the subjects were able to identify various shapes using the PHI system (1 = 0.3 m reference length, with Weber fraction = 0.38). This identification, however, was adversely affected by the lack of tactile sensation in the haptic device. The outcome of the force-feedback experiments demonstrated mixed results, an observation that was consistent with expenmental studies of other researchers. While force feedback did not affect the time needed to complete the task, the subjects' performance was significantly improved when the experiments involved controlling the thickness of a curve drawn on a pressure-sensitive tablet.