Softness Haptic Display Device for Human - Computer Interaction

In the field of virtual reality and teleoperation, haptic interaction between human operator and a computer or telerobot plays an increasingly important role in performing delicate tasks, such as robotic telesurgery, virtual reality based training systems for surgery, virtual reality based rehabilitation systems (Dario et al, 2003) (Taylor, Stoianovici, 2003) (Popescu, et al, 2000), etc. These applications call for the implementation of effective means of haptic display to the human operator. Haptic display can be classified into the following types: texture display, friction display, shape display, softness display, temperature display, etc. Previous researches on haptic display mainly focused on texture display (Lkei et al, 2001), friction display (Richard, Cutkosky, 2002) and shape display (Kammermeier et al, 2000). Only a few researches dealt with softness display, which consists of stiffness display and compliance display. The stiffness information is important to the human operator for distinguishing among different objects when haptically telemanipulating or exploring the soft environment. Some effective softness haptic rendering methods for virtual reality have already been proposed, such as a finite-element based method (Payandeh, Azouz, 2001), a pre-computation based method (Doug et al, 2001), etc. An experimental system for measuring soft tissue deformation during needle insertions has been developed and a method to quantify needle forces and soft tissue deformation is proposed (Simon, Salcudean, 2003). However, there are no effective softness haptic display devices with a wide stiffness range from very soft to very hard for virtual reality yet. The existing PHANToM arm as well as some force feedback data-gloves are inherently force display interface devices, which are unable to produce large stiffness display of hard object owing to the limitation of output force of the motors. This chapter focuses on the softness haptic display device design for human-computer interaction (HCI). We firstly review the development of haptic display devices especially softness haptic display devices. Then, we give the general principles of the softness haptic display device design for HCI. According to the proposed design principles, a novel method to realize softness haptic display device for HCI is presented, which is based on control of deformable length of an elastic element. The proposed softness haptic display device is composed of a thin elastic beam, an actuator for adjusting the deformable length of the beam, fingertip force sensor, position sensor for measuring the movement of human