Decorators Help Teleoperations

Abstract

The wide bandwidths of the communication and advanced bilateral robot control technologies have led us to realize multi-sensational teleoperation systems that provide auditory, visual, and haptic information of remote site to its operator simultaneously. Such teleoperation system is expected to be applied to medicine, education, work in hazardous environment, online game or other use. Especially, haptic sensation is extremely required to improve its operability and safety in medical operations. In this chapter, a teleoperation system is assumed to consist of three components, i.e., audio, video, and haptics transmission systems. In addition, each transmission system can be distinguished into local site and remote site. When the distance between the remote site and the local site of a teleoperation system is far enough, the performance of its communication line becomes crucial factor to decide the operability of the teleoperation. In general, since the data rate of video information is higher than the bandwidth of communication line, data compression is indispensable. Moreover, data compression and decompression are considered as time consuming processes. As a result, video transmission system must be delayed in principle. In multi-media context, audio transmission system should be delayed artificially so as to keep its playout delay to be the same as that of video transmission system. For example, lip sync is necessary for its operator to feel the audio and video contents in naturally. From this point of view, the bandwidth of its communication line is the only requirement for realize video and audio transmission systems. Even if these transmission systems are used to make a conversation for its operator with a remote person, it is said that 200ms delay is allowable. This requirement is rather negligible in the Internet in nowadays. On the other hand, a haptics transmission system requires short and stable performance of delay for communication line. This is because the achievable bandwidth of haptic sensation is limited by the round trip time of communication line since haptics transmission controller includes the delay inside of its closed control loop. In fact, a human being can feel the sense of touch at the tip of a finger up to about 400Hz. To recognize this bandwidth of haptic sensation, its sampling period must be higher than 800Hz according to Shannon’s sampling theory. Thus, the round trip time of communication line must be shorter than 1ms. This value is much shorter than the allowable delay of audio and video transmission systems. In short, haptics transmission system requires short delay while video transmission system requires wide bandwidth for communication line. 2