Performance evaluation of haptic device via quasi-quantitative Z-width

This paper presents the quasi-quantitative Z-width measurement method. The quasi-quantitative Z-width criterion is defined that the haptic interaction is unstable, if the frequency and amplitude of chattering go over certain level, which is a threshold for the instability. Through the literatural study, the threshold for instability was fixed 0.4 rad/sec amplitude with 30 Hz frequency, which is human´s discomfort level. The measurement of the instability is achieved by measuring the velocity and the number of zero-crossing of limit cycles during haptic display. Comparing the experimental results with theoretical results, the proposed quasi-quantitative Z-width can be applied to the haptic interfaces as a more reliable Z-width measurement method.