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This paper describes the testbed telesurgery system that was developed in MIT's Human Machine Systems Laboratory. This system was used to investigate the effects of communication time delays on controller stability and on the performance of surgical tasks. The system includes a bilateral force-reflecting teleoperator system, interchangeable surgical tools, audio and video communication between the master and slave sites, and methods to generate time delays between the sites. To compensate for the time delays, various control schemes were investigated, leading to the development and selection of fuzzy sliding control (FSC). With a stable teleoperator system, experiments in performing a variety of surgical exercises were conducted. These looked at the performance of a team of a telesurgeon and local assistant given a number of different time-delay scenarios, including synchronous and asynchronous force and audio/video feedback. The results of the research project include the development of the novel FSC algorithm, data on how time delays degrade performance of surgical tasks, and recommendations on how telesurgery should be performed to accommodate telecommunication time delays.

With regard to “presence” and “reality,” the philosophical perspectives of Heidegger and Gibson are commonly seen to be in opposition to those of Descartes. This paper questions the validity of these differences and suggests a framework that would seem to accommodate both perspectives, namely that of engineering estimation theory. In this same regard—and in view of our interest in virtual reality—an ultimate challenge is posed as an exercise: how to treat the “presence” and “reality” of God.

This is an extension of an earlier paper (Sheridan, 1992) that considered alternative meanings and significance of “presence,” the experience of “being there,” commonly called “telepresence” in the case of remote control or teleoperation, and called “virtual presence” in the case of computer-generated simulation. In both cases presence can include feedback to the human senses of vision, hearing, and haptics, both kinesthetic and cutaneous. Presence is discussed here in terms of alternative subjective meanings, operational measurements, and meaningful experimental comparisons. Three practical approaches to measurement of presence are compared, including elicitation of “natural” neuromuscular or vocal responses, single or multidimensional subjective scaling, and ability to discriminate the real and immediate environment from that which is recorded/transmitted or synthesized. A new proposal, fitting into the third category, is to measure presence according to the amount of noise required to degrade the real and virtual stimulation until the perceived environments are indiscriminable. The author also opines on the stimulus magnitude, space, and time attributes of human interactions with a tele- or virtual environment.

The objective of this research was to study the capabilities of sensory substitution for force feedback through the tactile and auditory senses for teleoperation tasks, with and without time delay. The motivation and potential benefits of sensory substitution for force feedback with vibrotactile and auditory displays are discussed. Teleoperator experiments that examined the presentation of basic force information through object contact tasks indicated that operator performance was improved by using the vibrotactile and auditory displays to present force information. Further, the vibrotactile and auditory displays compared favorably to traditional bilateral force feedback. Common manipulation experiments with peg-in-hole tasks of varying complexity were also conducted and showed that when the subjects' view was fully obstructed, the subjects were able to successfully complete the task by using either of the sensory substitution displays. Sensory substitution was also tested in the presence of a 3 sec time delay and significantly improved performance without instabilities.