Extending haptic augmented reality: Modulating stiffness during two-point squeezing

This paper is concerned with haptic augmented reality, which allows us to merge virtual haptic stimuli into the real haptic environment. Considering the modulation of real haptic properties as a key functionality, we previously focused on modulating stiffness of a real fixed object constrained at one contact point. In this paper we generalize the approach by enabling a user to grasp, lift, and manipulate an object via two interaction points. Modulated stiffness can be explored by squeezing an object. To this end, two haptic interfaces equipped with force sensors are employed to render the additional virtual forces of the augmentation at the two interaction points. We introduce the required extended algorithms and evaluate the performance in a pilot user study. A longer term goal of our work is the development of a training environment for tumor palpation.