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Modulated-Demodulated control (or vector control) allows to simultaneously impose amplitude and phase of a resonator. Moreover, the working frequency in the case of discrete-controller is substantially lower than the resonance frequency. However, the design of a such controller can be complex. In this paper, we outline a design directly in the baseband. To do so, the oscillator is modelled as a non-dimensional Multi-Input-Multi-Output system. An optimal control (Linear Quadratic Regulator) framework can then be used to design the controller. Thanks to ad hoc performances criteria, the weighting matrices are systematically specified according to the desired closed-lop time response. The methodology is validated by an experimental results on a plate actuated using piezoelectric patches.

This paper aims to investigate the semantic perceptual space of synthetic tactile textures rendered via an ultrasonic based haptic tablet and the parameters influencing this space. Through a closed card sorting task, 30 participants had to explore 32 tactile-only textures and describe each texture using adjectives. A factorial analysis of mixed data was conducted. Results suggest a 2 dimensional space with tactile textures belonging to a continuum of rough to smooth adjectives. Influence of waveform and amplitude is shown to play an important role in perceiving a texture as smooth or rough, and spatial period is a possible modulator of different degrees of roughness or smoothness. Finally, we discuss how these findings can be used by designers on tactile feedback devices.

In this paper, a psychophysical experiment is designed and setup to perform the comparison between lateral and normal ultrasonic vibration for friction modulation on haptic devices at the same vibration amplitudes. Thanks to a simple analytical modelling relying on mechanical contact, the results obtained are explained. A parametric analysis of this comparison is then performed.

In this paper, we present a method to observe the fundamental of the acoustical finger force for the case of a friction reduction based haptic interface. The capability of the method to be achieved on-line, in a small micro-controller is established. We show a correlation between this measurement and the friction when sliding the finger. A model that predicts the friction coefficient and the friction contrast is laid down; it gives consistent output for 10 participants out of 12 having different biomechanical parameters of the skin.

A realistic keyclick sensation is a serious challenge for haptic feedback since vibrotactile rendering faces the limitation of the absence of contact force as experienced on physical buttons. It has been shown that creating a keyclick sensation is possible with stepwise ultrasonic friction modulation. However, the intensity of the sensation is limited by the impedance of the fingertip and by the absence of a lateral force component external to the finger. In our study, we compare this technique to rendering with an ultrasonic travelling wave, which exerts a lateral force on the fingertip. For both techniques, participants were asked to report the detection (or not) of a keyclick during a forced choice one interval procedure. In experiment 1, participants could press the surface as many time as they wanted for a given trial. In experiment 2, they were constrained to press only once. The results show a lower perceptual threshold for travelling waves. Moreover, participants pressed less times per trial and exerted smaller normal force on the surface. The subjective quality of the sensation was found similar for both techniques. In general, haptic feedback based on travelling ultrasonic waves is promising for applications without lateral motion of the finger.