Fiche individuelle

This work presents the control of a piezoelectric interface that combines two vibration modes of a plate to render the haptic feeling of a button click. By principle, the two vibration modes create an elliptical motion of particles of a beam that can induce a lateral force to the fingerpulp. In this device, the synchronization of the modes’ vibrations is essential, and can be obtained with a closed loop control. In the paper, we present the control in the (d,q) frame, because it can ensure the dynamic performances to achieve a compelling haptic feedback, yet being robust besides the external disturbances produced by the user’s finger. The proposed method could achieve a 2 ms response time, and the haptic feedback was perceived by 100% of users in a psychophysical study.

Recent studies have shown that a button click sensation could be simulated thanks to ultrasonic vibrations. In this context, a travelling wave may enhance the simulation because it creates internal lateral stresses that are released during the stimulation. However, this solution is difficult to integrate on plates. We present 2MoTac, a method which superpose a longitudinal and a bending mode simultaneously on a plate, in order to create a pseudo-travelling wave. We present the design, and a psychophysical study to deduce the optimal ratio between the bending and longitudinal mode amplitudes, in terms of detection threshold and robustness.

The invention relates to a touch interface comprising, on the one hand, an interfacial surface able to generate a haptic-feedback effect in response to a touch of said surface by a user, and, on the other hand, at least one piezoelectric actuator configured to generate, in said interfacial surface, at least one wave of ultrasonic frequency able to endow the particles of this surface with an elliptical movement having a movement component tangential to said surface, which component is denoted ut(t), and a movement component normal to said surface, which component is denoted un(t), wherein said wave of ultrasonic frequency is chosen so that the amplitude Ut of the tangential component ut(t) and the amplitude Un of the normal component un(t) are substantially equal.

Dispositif pour la création de sensations haptiques sur une surface à l’aide d‘ondes ultrasonores produisant des mouvements elliptiques