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Modeling and design of asymmetric vibrations to induce ungrounded pulling sensation through asymmetric skin displacement

When subjected to asymmetric accelerations at the fingertips, a human perceives an ungrounded pulling sensation. This paper presents a model and analysis of the underlying physics and perception behind this pulling sensation. We design a system with voicecoil actuators that are driven with step-ramp current pulses to create asymmetric accelerations. When the voicecoils are attached to a handle, the force pulses are translated to skin displacement at the user's fingertips. This skin displacement, which is asymmetric in both amplitude and speed, is perceived as a directional pulling force, rather than as a vibration. Our analysis shows that the frequency and pulse width of the actuator inputs are important in creating effective skin displacement profiles. Both the amplitude and speed of skin displacement should be maximized in the desired direction, and minimized in the opposite direction. Our physical model of the system allows us to optimize the parameters of the actuator commands without time-intensive human-subject studies.