Objective and Subjective Assessment of Algorithms for Reducing Three-Axis Vibrations to One-Axis Vibrations

A typical approach to creating realistic vibrotactile feedback is reducing 3D vibrations recorded by an accelerometer to 1D signals that can be played back on a haptic actuator, but some of the information is often lost in this three-to-one (321) dimensional reduction process. This paper describes five real-time 321 algorithms and proposes four performance metrics that indicate the average value and the variability of the output signal's spectral match and temporal match across 3D rotations of the input vector. These four performance metrics were applied to four texture recordings, and the method utilizing the discrete Fourier transform (DFT) was found to be the best regardless of the sensing axis. We also recruited 16 human subjects to assess the perceptual similarity achieved by each 321 algorithm in real time. We found the four metrics correlated well with the subjectively rated similarities for four of the dimensional reduction algorithms, with the exception of taking the 3D vector magnitude, which was perceived to be good despite its low average spectral and temporal match metrics.