Vibrotactile actuators: Effect of load and body site on performance

The objective of the present set of experiments was to characterize the dynamics of two types of actuator used in vibrotactile displays: a linear resonant actuator and a C2 tactor. Of particular interest was to determine how much the inputs delivered by these actuators changed under varying load conditions and when they were mounted at different locations on the body. When on a rigid surface the force gain frequency response functions of the two tactors were found to be very similar, although the C2 tactor generated considerably higher forces. When the dynamics of the C2 tactor were measured on the skin, there was a substantial decrease in the displacement of the skin with load. When the two tactors were compared under the same loading conditions, the displacement produced by the LRA on the skin was an order of magnitude less than that of the C2 tactor. The resonant frequency of the LRA did vary with the site on the body to which it was attached, which appeared to be related to the stiffness and damping of the underlying skin. These studies indicate the importance of characterizing the properties of actuators used in tactile displays and of controlling how tactors are attached to the skin.