Integration of Electrotactile and Force Displays for Telexistence

Telexistence (or telepresence) enable us to interact with another human or object in a remote or a virtual place through a robotic system (Tachi & Yasuda, 1994). This technology spreads across the world because of a desire to extend a person’s sensing and interacting capability to remote places. In telexistence technologies, a robotic system called haptic display that provides haptic feedback to our hand is essential to touch the remote human or object (Shimoga, 1993a; 1993b). When we communicate or perform a task, a lack of haptic sensation reduces the realism and interactivity. Therefore, there is increasing requirement for haptic display presently. The haptic feedback can be divided into two types based on the receptor that acquires the sensory information. One type is tactile (cutaneous) feedback, which is acquired by mechanoreceptors that exist at a depth of several millimetres from the skin surface. The other type is force (or kinesthetic) feedback, which is acquired by the proprioceptors that exist in the muscle, tendon, and joint. Based on the characteristics of human perception, it would be appropriate to provide both types of haptic feedback. In particular, a spatially distributed tactile feedback is necessary for dexterous manipulation. The spatially distributed tactile feedback and force feedback help us to perceive the position of the object and improve the stability of hand movements, respectively. For example, while holding a pen, we can pinch it with our fingertips and feel the reactive force; the position of the pen can be determined by tactile sensations. Thus far, several haptic interfaces have been developed. However, these are not suitable for dexterous manipulation because of inadequate tactile feedback. The tactile display on conventional interfaces provides only a symbolic “contact” sensation of an object. Therefore, we cannot feel the object on our fingertips. It is believed that handling small objects such as pens is difficult without position information. Recently, some systems that can provide spatially distributed tactile sensation of an object have been proposed (Kim, et al., 2006; Methil, et al., 2006; Wagner, et al., 2005). Unfortunately, the systems proposed in these studies are too large for use in dexterous manipulation. A large system limits the workspace, i.e., the movement range of our finger required to manipulate an object. This limitation of workspace complicates manipulations such as pinching. On the basis of results of conventional studies, we aimed to develop a haptic display for dexterous manipulation. First, we will summarize the requirements for the tactile feedback display intended for dexterous manipulations; the requirements are as follows: