Haptic discrimination of softness in teleoperation: The role of the contact area spread rate

Many applications in teleoperation and virtual reality call for the impleme ntation of effective means of displaying to the human operator information on the softness and other mechanical properties of objects being touched. T he ability of humans to detect softness of different objects by tactual exp loration is intimately related to both kinesthetic and cutaneous perception , and haptic displays should be designed so as to address such multimodal p erceptual channel. Unfortunately, accurate detection and replication of cut aneous information in all its details appears to be a formidable task for c urrent technology, causing most of today's haptic displays to merely addres s the kinesthetic part of haptic information, In this paper, we investigate the possibility of surrogating detailed tactile information for softness d iscrimination, with information on the rate of spread of the contact area b etween the finger and the specimen as the contact force increases, Devices for implementing such a perceptual channel are described, and a practical a pplication to a mini-invasive surgery tool is presented. Psychophysical tes t results are reported, validating the effectiveness and practicality of th e proposed approach.