High-Precision Three-Axis Force Sensor for Five-Fingered Haptic Interface

Haptic interfaces that present force and tactile feeling have been utilized in the areas of telemanipulation (Ivanisevi & Lumelsky, 2000; Elhajj et al., 2001), interaction with micro/nano scale phenomena (Ando et al., 2001; Marliere et al., 2004), medical training and evaluation (Langrana et al., 1994; Basdogan et al., 2001), and so on. Haptic interfaces are key devices in constructing virtual reality environments. In contrast with single-point haptic interfaces, multi-fingered haptic interfaces hold promise for the above-mentioned applications and should dramatically increase the believability of the haptic experience (Magnenat-Thalmann & Bonanni, 2006). From these points of view, several multi-fingered haptic interfaces (Kawasaki & Hayashi, 1993; Ueda & Maeno, 2004; Walairacht et al., 2001; Bouzit et al., 2002; Adachi et al., 2002; Yoshikawa & Nagara, 2000; Immersion Corporation) have been developed. A haptic interface consisting of an arm and fingertips (Adachi et al., 2002; Yoshikawa & Nagara, 2000; Immersion Corporation) can be used in a wide space. However, most of them consist of a hand and arm exoskeleton system. With this system, it is hard to represent the weight of virtual objects through the fingertips because the hand mechanism is mounted on the back of a human hand. Fixing the haptic interface to the hand binds the hand and creates an oppressive sensation in the operator. Moreover, the operator is subject to a strong sense of unease when the system performs abnormally. The haptic interface must be safe, function in a wide space, and represent not only the force at the contact points but also the weight of virtual objects. In addition, it should not cause an oppressive feeling when it attached to humans and should not represent its own weight. In order to solve these problems, we have developed a multi-fingered haptic interface robot, which is placed opposite to the human hand: HIRO (Kawasaki et al., 2003) and HIRO II+ (Kawasaki & Mouri, 2007). However, HIRO and HIRO II+ have high reduction mechanisms at all finger joints, an arrangement that ensures the compactness of the mechanism, but requires force sensors at the haptic fingertips. Most haptic devices have a low reduction ratio, which permits impedance control without the use of a force sensor. However, this requires a large mechanism and entails difficulty in construction. Therefore, HIRO and HIRO II+ have high reduction mechanisms and require a O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg