Design and Evaluation of Haptic Soft Tissue Interaction

This chapter examines the application of a psychophysical evaluation technique to quantify the fidelity of haptic rendering methods. The technique is based on multidimensional scaling analysis of similarity ratings provided by users comparing pairs of haptically-presented objects. Unbeknownst to the participants, both real and virtual deformable objects were presented. In addition, virtual objects were either rendered under high fidelity condition or under lower-fidelity condition in which filtering quality was reduced. The analysis of pairwise similarity data provides quantitative confirmation that users perceived a clear difference between real and virtual objects in the lower-fidelity, but not in the higher-fidelity condition. In the latter, a single perceptual dimension, corresponding to stiffness, sufficed to explain similarity data, while two perceptual dimensions were needed in the former condition. This demonstrates how multidimensional scaling analysis can be used in the evaluation of haptic rendering scenarios, providing perceptual maps of real and virtual objects. It offers an opportunity to visualize and quantify the perceptual effects of changes in rendering parameters.